東北大学研究者紹介

顔写真

コイケ　ジユンイチ

小池　淳一

Junichi Koike

所属

大学院工学研究科　知能デバイス材料学専攻　インターコネクト・アドバンスト・テクノロジー共同研究講座

職名

教授

学位

Ｐｈ．Ｄ．（アメリカ合衆国ノースウエスタン大学）

researchmap

https://researchmap.jp/read0184472

J-GLOBAL ID

200901081098078140

学歴 3

ノースウェスタン大学大学院　工学研究科　材料科学

～ 1989年5月30日
東京工業大学　理工学研究科　金属工学専攻

～ 1985年8月15日
東京工業大学　工学部　金属工学科

～ 1983年3月31日

委員歴 4

日本金属学会分科会　幹事

2000年3月～継続中
日本金属学会分科会　幹事

2000年3月～継続中
日本金属学会　評議員

2006年3月～ 2010年3月
日本金属学会　評議員

2006年3月～ 2010年3月

所属学協会 4

日本鉄鋼協会
アメリカ材料学会(Materials Research Society)
応用物理学会
日本金属学会

研究キーワード 4

マグネシウム合金
電極材料
実装材料
半導体配線

研究分野 2

ナノテク・材料 / 構造材料、機能材料 / 薄膜の組織制御
ナノテク・材料 / 金属材料物性 / 薄膜の機械的性質

受賞 17

第15回本多フロンティア賞

2018年5月　公益財団法人本多記念会
第24回日本金属学会増本量賞

2018年3月　日本金属学会
科学技術賞

2013年4月　平成25年度科学技術分野文部科学大臣表彰
Outstanding Symposium Paper

2008年7月17日　Materials Research Society　MRSシンポジウムにおける優秀論文
IDW '07 Best paper award

2007年12月7日　International Display Workshop 2007
日本金属学会若手講演論文賞

2007年12月　日本金属学会
応用物理学会講演奨励賞

2007年12月　応用物理学会
ASMA Best Poster Award

2007年10月3日　2nd Asian Syposium on Magnesium Alloys
第４回STARC共同研究賞

2006年9月7日　半導体理工学研究センター
IITC2005 Lerme Best Paper Award

2006年6月5日　International Interconnect Technology Conference
日本金属学会論文賞

2004年9月28日　日本金属学会
応用物理学会講演論文奨励賞

2003年9月　応用物理学会
PSTAM講演論文賞

2003年1月　International Conference on Platform Science and Technology of Advanced Magnesium Alloys 2003
PSTAMポスター賞

2003年1月　International Conference on Platform Science and Technology of Advanced Magnesium Alloys 2003
日本金属学会功績賞

2001年3月28日　日本金属学会
原田研究奨励賞

1996年6月　金属研究助成会
トーキン科学技術振興財団研究奨励賞

1994年10月　トーキン科学技術振興財団

︎全件表示 ︎最初の5件までを表示

論文 229

Electrical transport mechanism of the amorphous phase in Cr2Ge2Te6 phase change material 査読有り

52　(10)　2019年

DOI： 10.1088/1361-6463/aafa94 　

ISSN：0022-3727

eISSN：1361-6463
Aging precipitation kinetics of Mg-Sc alloy with bcc+hcp two-phase 査読有り

Yukiko Ogawa, Yuji Sutou, Daisuke Ando, Junichi Koike

Journal of Alloys and Compounds　747　854-860　2018年5月30日
出版者・発行元：Elsevier Ltd
DOI： 10.1016/j.jallcom.2018.03.064 　

ISSN：0925-8388

詳細を見る詳細を閉じる

In our previous research, we reported that Mg-Sc alloys with a bcc (β) phase showed significant age hardening by the formation of fine hcp (α) precipitates in the β phase. In this study, we investigated the kinetics of the aging precipitation in the α+β two-phase Mg-Sc alloy. The incubation time for age hardening became shorter with increasing aging temperature. The relationship between the volume fraction of α precipitates and aging time was better described by the Austin-Rickett equation than by the Johnson-Mehl-Avrami-Kolmogorov equation, and the obtained n values are 1.2–1.4. According to the n values and the morphology of fine α precipitates, the mechanism of α precipitation in the Mg-Sc alloy with an α+β two-phase was proposed to be a diffusion-controlled reaction, including the one-dimensional growth of α precipitates at a constant or decreasing nucleation rate. In addition, the activation energy for α precipitation was calculated to be 83.5 kJ mol−1. This value is much smaller than that of self-diffusion in Mg, while it is almost the same as that of grain boundary diffusion in Mg, namely interface diffusion. This reveals that the growth of α precipitates is dominated by interface diffusion along the boundaries between the α precipitate and the β phase.
Contact resistance change memory using N-doped Cr2Ge2Te6 phase-change material showing non-bulk resistance change 査読有り

Y. Shuang, Y. Sutou, S. Hatayama, S. Shindo, Y. H. Song, D. Ando, J. Koike

Applied Physics Letters　112　(18)　2018年4月30日
出版者・発行元：American Institute of Physics Inc.
DOI： 10.1063/1.5029327 　

ISSN：0003-6951

詳細を見る詳細を閉じる

Phase-change random access memory (PCRAM) is enabled by a large resistance contrast between amorphous and crystalline phases upon reversible switching between the two states. Thus, great efforts have been devoted to identifying potential phase-change materials (PCMs) with large electrical contrast to realize a more accurate reading operation. In contrast, although the truly dominant resistance in a scaled PCRAM cell is contact resistance, less attention has been paid toward the investigation of the contact property between PCMs and electrode metals. This study aims to propose a non-bulk-resistance-dominant PCRAM whose resistance is modulated only by contact. The contact-resistance-dominated PCM exploited here is N-doped Cr2Ge2Te6 (NCrGT), which exhibits almost no electrical resistivity difference between the two phases but exhibits a typical switching behavior involving a three-order-of-magnitude SET/RESET resistance ratio owing to its large contact resistance contrast. The conduction mechanism was discussed on the basis of current-voltage characteristics of the interface between the NCrGT and the W electrode.
Co and CoTix for contact plug and barrier layer in integrated circuits 査読有り

Maryamsadat Hosseini, Daisuke Ando, Yuji Sutou, Junichi Koike

Microelectronic Engineering　189　78-84　2018年4月5日
出版者・発行元：Elsevier B.V.
DOI： 10.1016/j.mee.2017.12.017 　

ISSN：0167-9317

詳細を見る詳細を閉じる

Continuous transistor scaling in integrated circuits brings about a significant increase of electrical resistance in the source/drain area. To alleviate the problem, this paper proposes Co/CoTix to replace conventional contact plug/barrier materials of W/TiN/Ti. Co and CoTix amorphous alloy layers were deposited on SiO2/p-Si. The 3 nm-thick amorphous CoTix layer promoted adhesion between Co and SiO2. The resistivity of the 150 nm-thick Co film on CoTix showed low film resistivity close to bulk Co value both in as-deposited and annealed conditions. The amorphous structure of the CoTix layer was maintained throughout annealing up to 500 °C. Capacitance-voltage measurement of Co/CoTix/SiO2/p-Si samples showed a good diffusion barrier property of the CoTix layer between Co and SiO2 after thermal stress as well as bias thermal stress. The obtained results indicated that Co/CoTix can be good candidate materials for contact plug and diffusion barrier in advanced integrated circuits.
Inverse Resistance Change Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf>-Based PCRAM Enabling Ultralow-Energy Amorphization 査読有り

Shogo Hatayama, Yuji Sutou, Satoshi Shindo, Yuta Saito, Yun Heub Song, Daisuke Ando, Junichi Koike

ACS Applied Materials and Interfaces　10　(3)　2725-2734　2018年1月24日

DOI： 10.1021/acsami.7b16755 　

ISSN：1944-8244

eISSN：1944-8252

詳細を見る詳細を閉じる

© 2017 American Chemical Society. Phase-change random access memory (PCRAM) has attracted much attention for next-generation nonvolatile memory that can replace flash memory and can be used for storage-class memory. Generally, PCRAM relies on the change in the electrical resistance of a phase-change material between high-resistance amorphous (reset) and low-resistance crystalline (set) states. Herein, we present an inverse resistance change PCRAM with Cr2Ge2Te6 (CrGT) that shows a high-resistance crystalline reset state and a low-resistance amorphous set state. The inverse resistance change was found to be due to a drastic decrease in the carrier density upon crystallization, which causes a large increase in contact resistivity between CrGT and the electrode. The CrGT memory cell was demonstrated to show fast reversible resistance switching with a much lower operating energy for amorphization than a Ge2Sb2Te5 memory cell. This low operating energy in CrGT should be due to a small programmed amorphous volume, which can be realized by a high-resistance crystalline matrix and a dominant contact resistance. Simultaneously, CrGT can break the trade-off relationship between the crystallization temperature and operating speed.
Material innovation for MOL, BEOL, and 3D integration 査読有り

J. Koike, M. Hosseini, H. T. Hai, D. Ando, Y. Sutou

Technical Digest - International Electron Devices Meeting, IEDM　32.3.1-32.3.4　2018年1月23日
出版者・発行元：Institute of Electrical and Electronics Engineers Inc.
DOI： 10.1109/IEDM.2017.8268485 　

ISSN：0163-1918

詳細を見る詳細を閉じる

This paper presents new materials and processes for advanced technology node of Si semiconductor devices. For MOL, Co contact plug and amorphous Co-Ti barrier showed a good adhesion, limited growth of Co silicide, and a low contact resistivity of the order of 10-9 Ωcm2 on both n+ and p+ Si. For BEOL, a CVD-MnOx layer could be formed conformally in high-aspect ratio contact holes. The ALD-MnOx layer of 1.2 nm thick showed a good diffusion barrier property at 400 °C. For 3D integration, TSV of 10 μm diameter and 80 μm depth could be filled with low resistivity sintered Cu paste without voids.
Optical and electrical properties of i-MnTe thin films deposited using RF magnetron sputtering 査読有り

59　(9)　1506-1512　2018年

DOI： 10.2320/matertrans.M2018086 　

ISSN：1345-9678
New Contact Metallization Scheme for FinFET and beyond 査読有り

169-171　2018年

DOI： 10.1109/EDTM.2018.8421448 　
Crystallization mechanism and kinetics of Cr2Ge2Te6 phase change material 査読有り

8　(3)　1167-1172　2018年

DOI： 10.1557/mrc.2018.176 　

ISSN：2159-6859

eISSN：2159-6867
NiAl as a potential material for liner- and barrier-free interconnect in ultrasmall technology node 査読有り

113　(18)　2018年

DOI： 10.1063/1.5049620 　

ISSN：0003-6951
Amorphous CoTix as a liner/diffusion barrier material for advanced copper metallization 査読有り

Maryamsadat Hosseini, Junichi Koike

JOURNAL OF ALLOYS AND COMPOUNDS　721　134-142　2017年10月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/jjallcom.2017.05335 　

ISSN：0925-8388

eISSN：1873-4669

詳細を見る詳細を閉じる

This paper reports the possibility of using an amorphous Co-Ti alloy as a single-layer liner/barrier material for multilayer Cu interconnects in advanced silicon devices. Theoretical and experimental results both showed a stable composition range of an amorphous phase at room temperature to be Co-18 to 83 at% Ti. Liner/barrier property was investigated using sputtered films of Cu (150 nm)/CoTix (3 nm) on thermal SiO2/p-Si substrates, where x = 25 +/- 3 at%Ti. The CoTix layer was found to enhance adhesion between Cu and SiO2. The CoTix layer stayed amorphous after annealing at 400 degrees C, and started to crystallize at 500 degrees C. The crystallization accompanied the dissociation of CoTix, leading to the formation of Ti oxide and Cu-Co solid solution. Capacitance-voltage measurement of the samples showed no interdiffusion of Cu ions into SiO2 after annealing at 600 degrees C and after bias temperature annealing at 250 degrees C at 3 MV/cm. The results indicated that the CoTix alloy would be a good candidate for a single-layer liner/barrier material to replace a double-layer Ta/TaN. (C) 2017 Elsevier B.V. All rights reserved.
Molybdenum oxide-base phase change resistive switching material 査読有り

Yukiko Ogawa, Satoshi Shindo, Yuji Sutou, Junichi Koike

APPLIED PHYSICS LETTERS　111　(16)　2017年10月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.5000410 　

ISSN：0003-6951

eISSN：1077-3118

詳細を見る詳細を閉じる

We investigated the temperature dependence of electrical resistance of a reactively sputtered Mo-oxide film with a composition near MoO3 and found that the sputtered Mo-oxide film shows a large electrical resistance drop of much more than 10(4)-fold at over 350 degrees C. Such a large drop in electrical resistance was found to be caused by a phase transition from an amorphous state to a crystalline state. It was confirmed that a W/Mo-oxide/W device shows a typical resistive switching effect of a phase change random access memory material and exhibits reversible resistive switching by the application of unidirectional set and reset voltage. The resistance contrast of the device had a large value of about 10(5)-10(6). Furthermore, the Mo-oxide film showed much better thermal stability in the amorphous state than conventional phase change materials. These results indicate that the Mo-oxide film is a promising oxide-base phase change material for phase change random access memory. Published by AIP Publishing.
Feasibility study of Cu paste printing technique to fill deep via holes for low cost 3D TSV applications 査読有り

Hoang Tri Hai, Kang-Wook Lee, Daisuke Ando, Yuji Sutou, Mitsumasa Koyanagi, Junichi Koike

IITC 2017 - 2017 IEEE International Interconnect Technology Conference　2017年7月5日
出版者・発行元：Institute of Electrical and Electronics Engineers Inc.
DOI： 10.1109/IITC-AMC.2017.7968976 　

詳細を見る詳細を閉じる

And the resistivity of the Cu paste under the low temperature annealing condition. Through-Silicon-Via (TSV) formation is a key technology for the fabrication of 3-D IC with good performance. Cu TSV has been attracting attention because Cu has a low resistance that can significantly reduce RC delay. Currently, Cu TSV is formed by an electroplating method. But, it becomes increasingly difficult to fill Cu into small size holes with high aspect ratio. This is because a sputter seed layer has poor step coverage, which induces failure of Cu filling. On the other hand, large size holes of more than 20μm diameter requires a long process time to be filled by electroplating. The large size electroplated Cu also suffers from severe thermo-mechanical stress after post-annealing process. In addition, CMP process is necessary to remove Cu overburden on the top surface of TSV wafers. Recently, various new techniques have been proposed, which include paste printing [1-5], super critical fluid deposition [6], electroless seed deposition [7], and dipping [8]. Among the proposed methods, the paste printing technique owns greatly foreseen advantages. However, production has not yet been feasible because of the existing bottlenecks high resistivity (∼ 38μΩ.cm) of the Cu paste [1], serious formations of cracks and voids in the TSV filled with Ag nanoparticle pastes due to unavoidable shrinkage of sintered Ag particles and too long filling time (needed 4 cycles, with 14h for each) [3, 4]. A recent work reported the improvements on electrical resistivity and filling ability using a nano-sized low melting point alloy. However it was used for the vias of O25μm × 100μm in glass substrates [5].
Metallurgical and electrical characterization of ultrathin CoTix liner/barrier for Cu interconnects 査読有り

Maryamsadat Hosseini, Junichi Koike

IITC 2017 - 2017 IEEE International Interconnect Technology Conference　2017年7月5日
出版者・発行元：Institute of Electrical and Electronics Engineers Inc.
DOI： 10.1109/IITC-AMC.2017.7968959 　

詳細を見る詳細を閉じる

This paper reports an amorphous CoTix alloy as a single-layer liner/barrier material for intermediate interconnects in place of bilayer Ta/TaN materials. The CoTix layer was found to enhance adhesion of Cu/SiO2. The CoTix layer stayed amorphous after annealing at 400°C, and started to crystallize at 500°C. Capacitance-voltage measurement of the samples showed no interdiffusion of Cu ions into SiO2 after annealing up to 600°C and after bias thermal stress at 250°C at 3 MV/cm. All the obtained results showed that the amorphous CoTix alloy is a promising material for a liner/barrier layer in advanced technology node.
Enhanced fatigue properties of cast AZ80 Mg alloy processed by cyclic torsion and low-temperature annealing 査読有り

Qinghuan Huo, Zhenyu Xiao, Xuyue Yang, Daisuke Ando, Yuji Sutou, Junichi Koike

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　696　52-59　2017年6月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.msea.2017.04.061 　

ISSN：0921-5093

eISSN：1873-4936

詳細を見る詳細を閉じる

In this work, cyclic torsion and low-temperature annealing was applied to a cast AZ80 Mg alloy. After processing, the grains were refined in the outer region of the twisted samples whereas coarse grains remained in the central region. Meanwhile, a large number of {10-12} twins were generated in the outer region but only a few twins were observed in the central region. Both the tensile and compressive yield stresses were increased by grain refinement. At the same stress amplitude in stress-controlled fatigue tests, the strain energy was decreased. The fatigue limit was increased from 70 to 120 MPa, an increase attributed to pre-twinning induced by cyclic torsion.
Texture randomization of hexagonal close packed phase through hexagonal close packed/body centered cubic phase transformation in Mg-Sc alloy 査読有り

Yukiko Ogawa, Daisuke Ando, Yuji Sutou, Junichi Koike

SCRIPTA MATERIALIA　128　27-31　2017年2月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.scriptamat.2016.09.024 　

ISSN：1359-6462

詳細を見る詳細を閉じる

Mg-Sc alloy has a body centered cubic (bcc) phase at high temperature beside an hexagonal close packed (hcp) phase in the Mg-rich region. In this study, we investigated the effect of a heat treatment process on the texture formation of an hcp single-phase in Mg-Sc alloy by means of electron backscatter diffraction. It was found that a random textured hcp single-phase could be obtained by phase transformation from a bcc single-phase to an hcp single-phase and that the texture did not depend on the grain size. (C) 2016 Acta Materialia Inc Published by Elsevier Ltd. All rights reserved.
Effect of Initial Microstructure on Stress-Strain Behavior in Mg-Sc-Zn Based Alloy with High Sc Content 査読有り

Yuta Takeuchi, Yukiko Ogawa, Daisuke Ando, Yuji Sutou, Junichi Koike

JOURNAL OF THE JAPAN INSTITUTE OF METALS　81　(5)　276-281　2017年
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/jinstmet.JBW201612 　

ISSN：0021-4876

eISSN：1880-6880

詳細を見る詳細を閉じる

Mg-Sc-Zn based alloy was investigated to understand the effects of introducing bcc structure on mechanical properties. The alloy ingot was prepared by induction melting of ZK60 and pure Sc in Ar atmosphere, and then hot rolled at 550 degrees C into a sheet. The rolled sheets were finally annealed at 500 (designated as alpha-type) and 680 degrees C ( designated as alpha + beta-type) for 30 minutes. From XRD patterns and SEM observation, the existence of ScZn compound was confirmed in both samples. The volume fraction ratio of bcc/ (hcp + bcc) were 0 and 73% on samples annealed at 500 and 680 degrees C respectively. The ultimate tensile strength ( UTS) and elongation of the alpha (hcp). type sample were 280 MPa and 20.5%, respectively, while those of alpha (hcp)+ beta (bcc). type sample were 373 MPa and 5.9%, respectively. It was found that c/a ratio of alpha-type sample was small indicating that non. basal slip systems were activated during tensile test. On the other hand, it was suggested that, in beta phase, the stress induced phase transformation from bcc to hcp occurred during tensile test which causes higher strength and lower elongation.
Effect of Cu Content on Hardness and Wear Properties in (Cr, Mo, Cu) N Film 査読有り

Yuta Suzuki, Yuji Sutou, Daisuke Ando, Junichi Koike

JOURNAL OF THE JAPAN INSTITUTE OF METALS　81　(5)　270-275　2017年
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/jinstmet.JBW201613 　

ISSN：0021-4876

eISSN：1880-6880

詳細を見る詳細を閉じる

Effects of Cu addition on hardness and wear properties of (Cr, Mo) N films were investigated by nanoindentation and ball. on. disk measurements. (Cr100-x-yMoxCuy) N films were deposited onto a stainless steel substrate by a reactive DC magnetron sputtering of Cr50Mo50 and Cu targets under the mixture of argon (45 ccm) and nitrogen (5 ccm) gases. The hardness of the film increased from 21.9 to 23.5 GPa by Cu addition of y= 3.4 of Cu addition and then drastically decreased with further increasing Cu addition. The drastic decrease in hardness is caused by the formation of amorphous structure. In crystalline films, it was found that the change of hardness obeys the inverse Hall. Petch relationship. The wear mechanism of the film was changed by increasing Cu addition, adhesive wear (y= 0), lubricated wear (3.4 <= y <= 12.6) and abrasive wear (y >= 20.4). It was also found from wear track observation that the lubricated wear in the Cu content region of 3.4 <= y <= 12.6 was obtained by the formation of the oxide debris resulted from the film with as small amount of Cu (3.4 <= y <= 12.6). With further increase in Cu content (y >= 20.4), the film was severely worn because of its low hardness of the amorphous film.
Effect of Plasma Surface Finish on Wettability and Mechanical Properties of SAC305 Solder Joints 査読有り

Kyoung-Ho Kim, Junichi Koike, Jeong-Won Yoon, Sehoon Yoo

JOURNAL OF ELECTRONIC MATERIALS　45　(12)　6184-6191　2016年12月
出版者・発行元：SPRINGER
DOI： 10.1007/s11664-016-4908-4 　

ISSN：0361-5235

eISSN：1543-186X

詳細を見る詳細を閉じる

The wetting behavior, interfacial reactions, and mechanical reliability of Sn-Ag-Cu solder on a plasma-coated printed circuit board (PCB) substrate were evaluated under multiple heat-treatments. Conventional organic solderability preservative (OSP) finished PCBs were used as a reference. The plasma process created a dense and highly cross-linked polymer coating on the Cu substrates. The plasma finished samples had higher wetting forces and shorter zero-cross times than those with OSP surface finish. The OSP sample was degraded after sequential multiple heat treatments and reflow processes, whereas the solderability of the plasma finished sample was retained after multiple heat treatments. After the soldering process, similar microstructures were observed at the interfaces of the two solder joints, where the development of intermetallic compounds was observed. From ball shear tests, it was found that the shear force for the plasma substrate was consistently higher than that for the OSP substrate. Deterioration of the OSP surface finish was observed after multiple heat treatments. Overall, the plasma surface finish was superior to the conventional OSP finish with respect to wettability and joint reliability, indicating that it is a suitable material for the fabrication of complex electronic devices.
Stress-strain hysteresis and strain hardening during cyclic tensile test of Mg-0.6at%Y alloy 査読有り

Qinghuan Huo, Daisuke Ando, Yuji Sutou, Junichi Koike

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　678　235-242　2016年12月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.msea.2016.10.008 　

ISSN：0921-5093

eISSN：1873-4936

詳細を見る詳細を閉じる

The Mg-0.6at%Y alloy having an average grain size of 180 gm and random texture was subjected to cyclic tensile tests at room temperature. Tensile tests were performed at a strain rate of 1 x 10(-3) s(-1) for 10 cycles with the peak stress of 40, 70, and 100 MPa with reference to the 0.2% proof stress of 68 MPa. Hysteresis loops and cyclic strain hardening were observed in all peak stress cases. The observation of slip traces and twin types suggested that the hysteresis behavior was due to synchronous movement of basal slip and anomalous {10 (1) over bar2} twinning, and that the cyclic strain hardening was due to non-basal slip. Prismatic slip led to cyclic strain hardening when peak stress was below the proof stress, and both prismatic and pyramidal slip promoted larger cyclic strain hardening when peak stress was increased over the proof stress.
Determination of α/β phase boundaries and mechanical characterization of Mg-Sc binary alloys 査読有り

Ogawa, Y, Ando, D, Sutou, Y, Yoshimi, K, Koike, J

Materials Science and Engineering A　670　335-341　2016年7月
出版者・発行元：None
DOI： 10.1016/j.msea.2016.06.028 　

ISSN：0921-5093

eISSN：1873-4936
A lightweight shape-memory magnesium alloy 査読有り

Yukiko Ogawa, Daisuke Ando, Yuji Sutou, Junichi Koike

SCIENCE　353　(6297)　368-370　2016年7月
出版者・発行元：AMER ASSOC ADVANCEMENT SCIENCE
DOI： 10.1126/science.aaf6524 　

ISSN：0036-8075

eISSN：1095-9203

詳細を見る詳細を閉じる

Shape-memoryalloys (SMAs), which display shape recovery upon heating, aswell as superelasticity, offermany technological advantages in various applications. Those distinctive behaviors have been observed in many polycrystalline alloy systems such as nickel titantium (TiNi)-, copper-, iron-, nickel-, cobalt-, and Ti-based alloys but not in lightweight alloys such as magnesium (Mg) and aluminum alloys. Here we present a Mg SMA showing superelasticity of 4.4% at -150 degrees C and shape recovery upon heating. The shape-memory properties are caused by reversible martensitic transformation. This Mg alloy includes lightweight scandium, and its density is about 2 grams per cubic centimeter, which is one-third less than that of practical TiNi SMAs. This finding raises the potential for development and application of lightweight SMAs across a number of industries.
Contact resistivity of amorphous and crystalline GeCu<inf>2</inf>Te<inf>3</inf> to W electrode for phase change random access memory 査読有り

S. Shindo, Y. Sutou, J. Koike, Y. Saito, Y. H. Song

Materials Science in Semiconductor Processing　47　1-6　2016年6月1日

DOI： 10.1016/j.mssp.2016.02.006 　

ISSN：1369-8001

詳細を見る詳細を閉じる

© 2016 Elsevier Ltd. All rights reserved. We have investigated the contact resistivity of GeCu2Te3 (GCT) phase change material to a W electrode using the circular transfer length method (CTLM). The contact resistivity ρc of as-deposited amorphous GCT to W was 3.9×10-2 Ω cm2. The value of ρc drastically decreased upon crystallization and crystalline GCT that annealed at 300 °C showed a ρc of 4.8×10-6 Ω cm2. The ρc contrast between amorphous (as-deposited) and crystalline (annealed at 300 °C) states was larger in GCT than in conventional Ge2Sb2Te5 (GST). Consequently, it was suggested from a calculation based on a simple vertical structure memory cell model that a GCT memory cell shows a four times larger resistance contrast than a GST memory cell.
Internal microstructure observation of enhanced grain-boundary sliding at room temperature in AZ31 magnesium alloy 査読有り

D. Ando, Y. Sutou, J. Koike

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　666　94-99　2016年6月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.msea.2016.04.030 　

ISSN：0921-5093

eISSN：1873-4936

詳細を見る詳細を閉じる

The origin of grain boundary sliding (GBS) is known to be slip-induced due to plastic incompatibility near the grain boundary at room temperature. In this study, the relationship between GBS and crystal orientation was investigated in AZ31 Mg alloy rolled sheets at room temperature. The GBS tendency was determined as related to basal dislocation slip where the GBS boundaries were generally located between the grains with respectively high and low or high and high Schmid factors for basal slip. The results indicate that GBS is attributed to the plastic incompatibility caused by anisotropic basal and prismatic slip. Furthermore, GBS was located in regions with localized deformation near grain boundaries. Cross-sectional focused ion beam/transmission electron microscopy (FIB/TEM) observations of these regions revealed seriately arranged subgrains adjacent to a grain boundary. Therefore, we propose that RT-GBS in AZ31 can be caused by localized crystal rotation due to dynamic recover and recrystallization by stress concentration near the grain boundary but not ordinary GBS. (C) 2016 Elsevier B.V. All rights reserved.
XAFS Analysis of Crystal GeCu<inf>2</inf>Te<inf>3</inf> Phase Change Material 査読有り

Kenji Kamimura, Koji Kimura, Shinya Hosokawa, Naohisa Happo, Hiroyuki Ikemoto, Yuji Sutou, Satoshi Shindo, Yuta Saito, Junichi Koike

Zeitschrift fur Physikalische Chemie　230　(3)　433-443　2016年3月28日

DOI： 10.1515/zpch-2015-0672 　

ISSN：0942-9352

詳細を見る詳細を閉じる

© 2015 Walter de Gruyter Berlin/Boston. The structure of crystal GeCu2Te3 was investigated by X-ray absorption fine structure (XAFS) measurement. We found that the Ge-Te interatomic distances obtained from XAFS are larger than those obtained from X-ray diffraction, and the Cu-Te distances are smaller. The averaged Ge-Te and Cu-Te distances obtained from XAFS are almost equal to the corresponding interatomic distances in amorphous GeCu2Te3. Therefore both crystal and amorphous GeCu2Te3 seem to be built up of the same local configurations of GeTe4 and CuTe4 tetrahedrons. This would be the reason why the phase change in GeCu2Te3 occurs very fast.
Hardness and Wear Properties of Ti-Mo-C-N Film 査読有り

Toshiaki Toyoda, Yuji Sutou, Shoko Komiyama, Daisuke Ando, Junichi Koike, Mei Wang

MATERIALS TRANSACTIONS　57　(3)　362-367　2016年3月
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/matertrans.M2015383 　

ISSN：1345-9678

eISSN：1347-5320

詳細を見る詳細を閉じる

The hardness and wear properties of Ti-Mo-C-N films were investigated by nanoindentation and ball-on-disc measurements, respectively. Ti-Mo-C-N films were deposited onto a stainless steel substrate by a reactive RF magnetron sputtering in the mixture of argon (7.5 ccm) and nitrogen (0-6.0 ccm) gases using Ti25Mo25C50 target. Ti-Mo-C film deposited without nitrogen gas flow showed a hardness of 34.8 GPa. The hardness drastically decreased with increasing nitrogen gas flow rate (f(N2)) and reached to a minimum hardness of 16.4 GPa at f(N2) = 2.0 ccm. Contrarily, at over f(N2) = 3.0 ccm, the hardness drastically increased with increasing f(N2) and reached a maximal value of 32 GPa, and then slightly decreased again with further increase of f(N2). It was found by TEM observation that the drastic decrease in hardness is caused by the formation of nanocrystalline microstructure, while the increase in hardness is due to the microstructural change from nanocrystalline to columnar structure. The friction coefficient decreased with increasing f(N2) and the film deposited at f(N2) = 5.0 ccm showed a minimum value of 0.27. The simple oxidation test in air indicated that lubricious MoO3 is easy to be formed in the film deposited at a high f(N2), which should cause the reduction of friction coefficient.
Aging effect of Mg-Sc alloy with α+β two-phase microstructure 査読有り

Ogawa, Y, Ando, D, Sutou, Y, Koike, J

Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals　80　(3)　171-175　2016年3月
出版者・発行元：None
DOI： 10.2320/jinstmet.JBW201511 　

ISSN：0021-4876

eISSN：1880-6880
XAFS analysis on amorphous and crystalline new phase change material GeCu<inf>2</inf>Te<inf>3</inf> 査読有り

K. Kamimura, S. Hosokawa, N. Happo, H. Ikemoto, Y. Sutou, S. Shindo, Y. Saito, J. Koike

Journal of Optoelectronics and Advanced Materials　18　(3-4)　248-253　2016年3月

ISSN：1454-4164

詳細を見る詳細を閉じる

© 2016, National Institute of Optoelectronics. All rights reserved. The structure of crystalline and amorphous GeCu2Te3 phase change material was investigated by x-ray absorption fine structure. The averaged interatomic distances of Ge-Te and Cu-Te in the crystal phase are confirmed to contradict the x-ray diffraction data, and are mostly equal to the experimental data in the amorphous phase. As regards the coordination numbers, the atomic configurations around the Ge atoms are a small modification of the crystalline one, while those around the Cu atoms are quite different and the large number of the Cu-Cu homopolar coordination become an important role in the amorphous phase. The x-ray absorption near edge structure data near the Ge K edge show a similarity of the local atomic configurations around the Ge atoms between the crystalline and amorphous GeCu2Te3. However, those near the Cu K edge indicate a large smearing-out on the amorphization, corresponding the large differences in the atomic configurations around the Cu atoms.
Crystal Orientation Changing Behavior During Erichsen Test in Mg-Y Dilute Alloy 査読有り

Tetsu Suzuki, Daisuke Ando, Hidetoshi Somekawa, Yuji Sutou, Junichi Koike

JOURNAL OF THE JAPAN INSTITUTE OF METALS　80　(8)　515-520　2016年
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/jinstmet.J2016018 　

ISSN：0021-4876

eISSN：1880-6880

詳細を見る詳細を閉じる

This paper reports the microstructure observation and crystal orientation change during Erichsen test on Mg-Y extruded alloy sheets. The Erichsen value of Mg-Y alloy was 4.2 which was higher than 1.8 of AZ31 commercial alloy rolled sheet. The result shows Mg-Y alloy has high formability than AZ31 rolled sheet. From the EBSD results of their crystal orientation change, tensile twin formed from early deformation stage and the area fraction of tensile twin increased with increasing the Erichsen value. In this time, crystal orientation changed to c axis parallel to nominal direction. During the Erichsen test, the randomly crystal orientation change to strong basal texture due to tensile twin. On the other hand, compression and their double twins formed on the strong basal textured grains from medium deformation stage. These compression twins easily formed the grains because of high Schmid factor for compression twin. The area fraction of these compression twins increased to 5% with increasing the Erichsen value. It was reported that double twins accompanied localized severe deformation and triggered premature failure in strong basal texture Mg alloy. Therefore, even in Mg-Y alloy with randomly crystal orientation, the crystal orientation change to strong basal texture due to tensile twin and it is presumed that these double twins also triggered premature failure.
Effect of surface cleaning on contact resistivity of amorphous GeCu<inf>2</inf>Te<inf>3</inf> to a W electrode 査読有り

S. Shindo, Y. Sutou, J. Koike, Y. Saito, Y. H. Song

MRS Advances　1　(39)　2731-2736　2016年

DOI： 10.1557/adv.2016.310 　

eISSN：2059-8521

詳細を見る詳細を閉じる

Copyright © Materials Research Society 2016. The contact resistivity, ρ c, between phase change material (PCM) and an electrode plays an important role in the operation of highly scaled phase change random access memory (PCRAM). We investigated the effect of surface cleaning on the ρ c between a W electrode and amorphous GeCu2Te3 (GCT) which shows high thermal stability. The surface cleaning of the amorphous GCT was conducted by Ar reverse sputtering. The ρ c of the amorphous GCT whose surface was cleaned with Ar reverse sputtering was 6.7×10-3Ω cm2. Meanwhile, the ρ c of the amorphous GCT with no surface cleaning was 8.0×10-5Ω cm2. The low ρ c in the amorphous GCT with no surface cleaning was apparently due to the existence of a low resistance Cu-rich underlayer which was formed as a consequence of surface oxidation of the amorphous GCT. These results indicate that the surface of a PCM must be treated carefully to accurately measure the contact resistivity between the PCM and electrodes.
Study on fatigue mechanism of Mg-0.6at%Y alloy by cyclic tensile test 査読有り

Huo, Q, Ando, D, Koike, J, Sutou, Y

Magnesium Technology　2016-January　299-303　2016年

DOI： 10.1002/9781119274803.ch58 　

ISSN：1545-4150
Age-hardening of dual phase Mg-Sc alloy at 573 K 査読有り

Ogawa, Y, Ando, D, Sutou, Y, Koike, J

Magnesium Technology　2016-January　147-149　2016年

DOI： 10.1002/9781119274803.ch29 　

ISSN：1545-4150
Aging effect of Mg-Sc alloy with α+β two-phase microstructure 査読有り

Ogawa, Y, Ando, D, Sutou, Y, Koike, J

Materials Transactions　57　(7)　1119-1123　2016年
出版者・発行元：None
DOI： 10.2320/matertrans.M2016093 　

ISSN：1345-9678

eISSN：1347-5320
Amorphous Co-Ti alloy as a single layer barrier for Co local interconnect structure 査読有り

Maryamsadat Hosseini, Junichi Koike, Yuji Sutou, Larry Zhao, Steven Lai, Reza Arghavani

2016 IEEE INTERNATIONAL INTERCONNECT TECHNOLOGY CONFERENCE / ADVANCED METALLIZATION CONFERENCE (IITC/AMC)　162-164　2016年
出版者・発行元：IEEE
DOI： 10.1109/IITC-AMC.2016.7507718 　

詳細を見る詳細を閉じる

This paper reports a new local interconnect structure using Co M0/contact and a Co-Ti amorphous single layer barrier. Good adhesion and low film resistivity were obtained for as-deposited and annealed samples. The metaloxide-semiconductor samples of Co/Co-Ti/SiO2/p-Si showed a high breakdown voltage and no negative shift of flat band voltage after annealing up to 700 degrees C for 10 min. The amorphous structure of the Co-Ti layer was maintained throughout annealing and prevented Co diffusion into dielectric. The obtained results indicated that Co-Ti could be a potential candidate to replace conventional local interconnect structure of Ti/TiN.
Erratum to “Determination of ?/β phase boundaries and mechanical characterization of Mg-Sc binary alloys” [Mater. Sci. Eng. A 670 (2016) 335?341] 査読有り

Ogawa, Y, Ando, D, Sutou, Y, Yoshimi, K, Koike, J

Materials Science and Engineering A　674　713　2016年

DOI： 10.1016/j.msea.2016.08.016 　
Structure and Thermoelectric Properties of PbTe Films Deposited by Thermal Evaporation Method 査読有り

M. P. Nguyen, J. Froemel, S. Hatayama, Y. Sutou, J. Koike, S. Tanaka, M. Esashi, T. Gessner

2016 IEEE 16TH INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO)　566-568　2016年
出版者・発行元：IEEE
DOI： 10.1109/NANO.2016.7751384 　

詳細を見る詳細を閉じる

Lead telluride (PbTe) thin films have been deposited on SiO2 substrate using thermal evaporation method. The structure of the films was found to have a face-centered cubic (fcc) with predominant grain growth in the (200) direction for both as-deposited and annealed samples up to 350 degrees C in vacuum for 1 h. The in-plain electrical resistivity and Hall measurements via van der Pauw method as a function of annealed temperatures were measured. It was found that increasing the annealing temperature led to increase in grain size, which in turn caused decrease of electrical resistivity and increase of Seebeck coefficient. The high power factor of 141.0 mu Wm(-1)K(-2) was obtained for the annealed samples at 350 degrees C in vacuum for 1 h.
Age-hardening effect by phase transformation of high Sc containing Mg alloy 査読有り

D. Ando, Y. Ogawa, T. Suzuki, Y. Sutou, J. Koike

MATERIALS LETTERS　161　5-8　2015年12月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/j.matlet.2015.06.057 　

ISSN：0167-577X

eISSN：1873-4979

詳細を見る詳細を閉じる

The effect of aging treatment on microstructure and hardness in a Mg-16.8 at%Sc alloy with a bcc phase (beta-Sc) was investigated. The hardness increased dramatically upon aging, owing to the formation of a fine hcp phase (alpha-Mg) in the bcc phase. The width of the hcp phase was below 50 nm. The crystal orientation of each phase was related by the Burgers orientation relationship. The maximum Vickers hardness was 231.5 Hv after aging treatment at 473 K for 18 ks. This significant age-hardening could be explained by the solid-solution hardening of Sc in Mg and the grain refinement hardening by the hcp precipitates. (C) 2015 Elsevier B.V. All rights reserved.
Microstructure, hardness and wear resistance of reactive sputtered Mo-O-N films on stainless steel substrate 査読有り

Y. Sutou, S. Komiyama, M. Sonobe, D. Ando, J. Koike, M. Wang

SURFACE & COATINGS TECHNOLOGY　280　1-7　2015年10月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.surfcoat.2015.08.047 　

ISSN：0257-8972

詳細を見る詳細を閉じる

The microstructure, hardness and wear property of Mo-O-N films deposited at different oxygen gas flow rates, f(O2), on SUS304 stainless steel were investigated. The hardness, H, of the film increased with increasing f(O2) in a low f(O2) region (f(O2) <= 0.05 sccm) and reached a maximum value of about 32 GPa because of grain refinement. With further increasing f(O2), the H started to decrease due to the formation of the amorphous phase. Similarly, the effective Young's modulus, E*, of the film increased and then decreased with increasing f(O2). It was found that the H/E* of the film could be enhanced by the addition of oxygen. The Mo-O-N film deposited at f(O2) = 0.2 sccm showed lower H and E*, but much higher H/E* than Mo-N film because of its considerably lower E*, which was due to the formation of a crystalline/amorphous mixed structure. The film deposited at f(O2) = 0.2 sccm with a crystalline/amorphous mixed structure showed the lowest mu in the present study and exhibited less frequent transverse cracking introduced by wear, as compared with that deposited at f(O2) = 0.02 sccm with a fine grain crystalline microstructure. These results indicate that the formation of the crystalline/amorphous mixed structure in the Mo-O-N film is effective to enhance the elasticity of the film without the associated large loss of the H, which leads to low mu and good wear resistance on the stainless steel substrate. (C) 2015 Elsevier B.V. All rights reserved.
Crystallization processes of Sb<inf>100-x</inf>Zn<inf>x</inf> (0 ≤ x ≤ 70) amorphous films for use as phase change memory materials 査読有り

Yuta Saito, Masashi Sumiya, Yuji Sutou, Daisuke Ando, Junichi Koike

AIP Advances　5　(9)　2015年9月1日

DOI： 10.1063/1.4931392 　

eISSN：2158-3226

詳細を見る詳細を閉じる

© 2015 Author(s). The phase change processes of as-deposited Sb-Zn films were investigated. The as-deposited amorphous SbZn film showed an unusual increase in resistance during heating, which was attributed to crystallization of the metastable SbZn phase. Further heating up to more than 300oC resulted in a structural transformation into the stable SbZn phase accompanied by a drop in resistance as in conventional phase change materials. Even though off-stoichiometric Sb-rich films exhibited crystallization into the metastable phase as well, the precipitation of Sb crystalline grains caused an undesirable drop in resistance at temperatures lower than that of the SbZn film. A memory device using an SbZn film showed typical switching behavior and successfully switched from the amorphous to crystal state and vice versa by the application of an electric pulse. These results revealed that stoichiometric SbZn film is a promising novel phase change material for phase change memory with high thermal stability.
Wear and oxidation behavior of reactive sputtered δ-(Ti,Mo)N films deposited at different nitrogen gas flow rates 査読有り

Komiyama, S, Sutou, Y, Oikawa, K, Koike, J, Wang, M, Sakurai, M

Tribology International　87　32-39　2015年7月
出版者・発行元：None
DOI： 10.1016/j.triboint.2015.02.005 　

ISSN：0301-679X

eISSN：1879-2464
Diffusion barrier property of MnSixOy layer formed by chemical vapor deposition for Cu advanced interconnect application 査読有り

Mai Phuong Nguyen, Yuji Sutou, Junichi Koike

THIN SOLID FILMS　580　56-60　2015年4月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.tsf.2015.03.007 　

ISSN：0040-6090

詳細を見る詳細を閉じる

An amorphous manganese oxide layers formed by chemical vapor deposition have been studied as a copper diffusion barrier. The thermal stability of the barrier layer was assessed by annealing Cu/MnSixOy/SiO2/Si samples at 400 degrees C for various times up to 10 h. Transmission electron microscopy, energy-dispersive X-ray spectroscopy (EDX), secondary ion mass spectroscopy (SIMS), capacitance-voltage and current-voltage measurements were performed. Failure of the barrier property is marked by observing the copper peak appearing in EDX and SIMS spectra data fromthe SiO2 region. Amorphous MnSixOy barrier with a thickness of 1.2 nm has failed in preventing Cu diffusion into SiO2 substrate after anneal at 400 degrees C in vacuum for 1h, as proven by the presence of Cu in the dielectric (SiO2) layer. However, the amorphous MnSixOy with the thickness of 2.0 nm barrier was thermally stable and could prevent Cu from inter-diffusion to the SiO2 substrate after annealing at 400 degrees C even up to 10 h. (C) 2015 Elsevier B.V. All rights reserved.
Hardness and Wear Properties of Ti-Mo-C-N Film 査読有り

Toshiaki Toyoda, Yuji Sutou, Shoko Komiyama, Daisuke Ando, Junichi Koike, Mei Wang

JOURNAL OF THE JAPAN INSTITUTE OF METALS　79　(4)　220-226　2015年
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/jinstmet.JBW201401 　

ISSN：0021-4876

eISSN：1880-6880

詳細を見る詳細を閉じる

The hardness and wear properties of Ti-Mo-C-N films were investigated by nanoindentation and ball-on-disc measurements, respectively-Ti-Mo-C-N films were deposited onto a stainless steel substrate by a reactive RF magnetron sputtering in the mixture of argon (7.5 ccm) and nitrogen (0-6.0 ccm) gases using Ti25Mo25C50 target. Ti-Mo-C film deposited without nitrogen gas flow showed a hardness of 34.8 GPa-The hardness drastically decreased with increasing nitrogen gas flow rate (f(N2)) and reached to a minimum hardness of 16.4 GPa at f(N2) = 2.0 ccm. Contrarily, at over f(N2) = 3.0 ccm, the hardness drastically increased with increasing f(N2) and reached a maximal value of 32 GPa, and then slightly decreased again with further increase of f(N2). It was found by TEM observation that the drastic decrease in hardness is caused by the formation of nanocrystalline microstructure, while the increase in hardness is due to the microstructural change from nanocrystalline to columner structure. The friction coefficient decreased with increasing f(N2) and the film deposited at f(N2) = 5.0 ccm showed a minimum value of 0.27. The simple oxidation test in air indicated that lubricious MoO3 is easy to be formed in the film deposited at a high f(N2), which should cause the reduction of friction coefficient.
Precipitation hardening in Ti-Mo-N coating deposited by reactive sputtering 査読有り

Sutou, Y, Komiyama, S, Oikawa, K, Ando, D, Koike, J

PTM 2015 - Proceedings of the International Conference on Solid-Solid Phase Transformations in Inorganic Materials 2015　417-418　2015年
Recrystallization process and texture change of Mg-Y alloy rolled sheet 査読有り

Tetsu Suzuki, Daisuke Ando, Yuji Sutou, Junichi Koike

Keikinzoku/Journal of Japan Institute of Light Metals　65　(7)　259-262　2015年
出版者・発行元：Japan Institute of Light Metals
DOI： 10.2464/jilm.65.259 　

ISSN：0451-5994

詳細を見る詳細を閉じる

This paper reports the texture weakening associated with the characteristic recrystallization processes of cold-rolled and hot-rolled Mg-Y alloy during annealing at 400°C. After rolling, severely strained regions were formed along grain boundaries for the cold-rolled samples and across neighboring grains for the hot-rolled samples. In the severely strained regions, the cold-rolled sample showed the presence of the 〈c+a〈 dislocations, while the hot-rolled sample showed the formation of multiple twins. The results suggested that the texture weakening after annealing was due to the formation of nucleation site for recrystallization near boundaries by the high activity of the 〈c+a〈 dislocations in the cold-rolled sample. Meanwhile, in the hot-rolled sample, it was due to the formation of multiple twins which acted as the nuclei of recrystallized grains.
Significant age hardening response of BCC/HCP dual phase Mg-Sc alloys 査読有り

Ando, D, Ogawa, Y, Sutou, Y, Koike, J

PTM 2015 - Proceedings of the International Conference on Solid-Solid Phase Transformations in Inorganic Materials 2015　1207-1208　2015年
Determination of HCP/BCC boundaries and mechanical properties of dual phase alloy in binary Mg-Sc system 査読有り

Ogawa, Y, Ando, D, Sutou, Y, Koike, J

PTM 2015 - Proceedings of the International Conference on Solid-Solid Phase Transformations in Inorganic Materials 2015　419-420　2015年
Chronological change of electrical resistance in GeCu<inf>2</inf>Te<inf>3</inf> amorphous film induced by surface oxidation 査読有り

Yuta Saito, Satoshi Shindo, Yuji Sutou, Junichi Koike

Journal of Physics D: Applied Physics　47　(47)　2014年11月26日

DOI： 10.1088/0022-3727/47/47/475302 　

ISSN：0022-3727

eISSN：1361-6463

詳細を見る詳細を閉じる

© 2014 IOP Publishing Ltd. Unusual chronological electrical resistance change behavior was investigated for amorphous GeCu2Te3 phase change material. More than a 1 order decrease of electrical resistance was observed in the air even at room temperature. The resistance of the amorphous film gradually increased with increasing temperature and then showed a drop upon crystallization. Such unusual behavior was attributed to the oxidation of the amorphous GeCu2Te3 film. From the compositional depth profile measurement, the GeCu2Te3 film without any capping layer was oxidized in air at room temperature and the formed oxide was mainly composed of germanium oxide. Consequently, a highly-conductive Cu-rich layer was formed in the vicinity of the surface of the film, which reduced the total resistance of the film. The present results could provide insight into the chronological change of electrical resistance in amorphous chalcogenide materials, indicating that not only relaxation of the amorphous, but also a large atomic diffusion contributes to the chronological resistance change.
Phase change characteristics in GeTe-CuTe pseudobinary alloy 査読有り

Yuta Saito, Yuji Sutou, Junichi Koike

Journal of Physical Chemistry C　118　(46)　26973-26980　2014年11月20日

DOI： 10.1021/jp5066264 　

ISSN：1932-7447

eISSN：1932-7455

詳細を見る詳細を閉じる

© 2014 American Chemical Society. Phase change characteristics in GeTe-CuTe pseudobinary alloy films, including GeCu2Te3 (GCT), were investigated. The crystallization temperature of the amorphous film increased with increasing Cu content and then decreased again with further increasing Cu content. X-ray diffraction measurements revealed that the amorphous films with a composition range from 0 to 18.6 atom % Cu crystallized to GeTe single-phase, while the amorphous films with a composition range from 26.2 to 37.9 atom % Cu crystallized to GCT single-phase. The amorphous films with a composition between 21.1 and 24.3 atom % Cu showed a clear two-step crystallization during heating and finally formed the GeTe and GCT mixed-phase. The amount of volume shrinkage upon crystallization of the amorphous film decreased with increasing Cu contents, and the film with around 23 atom % Cu showed almost no volume change after crystallization. Meanwhile, film with over 25 atom % Cu showed volume expansion. It was found that no volume change was achieved by a two-step crystallization, namely, initial crystallization to GCT (volume expansion) with subsequent crystallization to GeTe (volume shrinkage). The film with no volume change also showed no reflectance change upon crystallization. The obtained results suggest that nonstoichiometric Ge50-xCuxTe50 films such as 26.2Cu film showing a small volume change without phase separation are preferable in terms of cyclability of phase change random access memory. (Graph Presented).
Effects of O-2 and N-2 Flow Rate on the Electrical Properties of Fe-O-N Thin Films 査読有り

Yukiko Ogawa, Daisuke Ando, Yuji Sutou, Junichi Koike

MATERIALS TRANSACTIONS　55　(10)　1606-1610　2014年10月
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/matertrans.M2014089 　

ISSN：1345-9678

eISSN：1347-5320

詳細を見る詳細を閉じる

We report the dependence of electrical properties of Fe-O-N thin films on the deposition condition as well as on O-2 and N-2 gas flow rate. Fe-O-N films were deposited by reactive sputtering using O-2 and N-2 as reactive gas. The electrical resistivity of Fe-O-N films increased with increasing O-2 and N-2 gas flow rate. The resistivity increase with the O-2 flow rate was due to structure change from a mixed phase of metallic Fe+Fe3O4, to a mixed phase of FeO+alpha-Fe2O3, and to a single phase of alpha-Fe2O3, as evidenced by XPS analysis of Fe 2p core excitation peaks. Meanwhile, the resistivity increase with the N2 flow rate was due to structure change from a metallic Fe, to a mixed phase of metallic Fe+Fe3O4, and to a single phase of Fe3O4.
Formation behavior and adhesion property of metallic Mn layer on porous SiOC by chemical vapor deposition 査読有り

Yoshiyuki Tsuchiya, Daisuke Ando, Yuji Sutou, Junichi Koike

JAPANESE JOURNAL OF APPLIED PHYSICS　53　(5)　2014年5月
出版者・発行元：IOP PUBLISHING LTD
DOI： 10.7567/JJAP.53.05GA10 　

ISSN：0021-4922

eISSN：1347-4065

詳細を見る詳細を閉じる

A metallic Mn layer was successfully formed on a porous SiOC (Black Diamond-III, BD-III) substrate at 300 degrees C by chemical vapor deposition (CVD) using a newly developed Mn precursor, bis[1-(tert-butylamide)-2-dimethylaminoethane-N,N']Mn. A thin layer of Mn silicate was also formed at the interface between the metallic Mn and the porous SiOC. The formation of the metallic Mn layer was a thermally activated process with the activation energy of 161.2 kJ.mol(-1). The metallic Mn layer enhanced the adhesion and wettability of Cu on the BD-III substrates. (C) 2014 The Japan Society of Applied Physics
Reflow behavior of Cu-Mn in LSI line patterns 査読有り

Tomohiro Saito, Daisuke Ando, Yuji Sutou, Junichi Koike

JAPANESE JOURNAL OF APPLIED PHYSICS　53　(5)　2014年5月
出版者・発行元：IOP PUBLISHING LTD
DOI： 10.7567/JJAP.53.05GA09 　

ISSN：0021-4922

eISSN：1347-4065

詳細を見る詳細を閉じる

The reflow behavior of sputter-deposited Cu-Mn alloy into narrow trench lines formed in a SiO2 dielectric layer was investigated. At a substrate temperature of 350 degrees C, Cu-Mn completely filled a trench of 50 nm width. The reflow was rate-controlled by mixed-mode diffusion. An interfacial layer was formed between Cu and SiO2 during this process, which was considered to improve wettability and enhance reflow filling. The reflowed Cu-Mn lines had a few grain boundaries, most of which are coherent twin boundaries. (C) 2014 The Japan Society of Applied Physics
Multiple phase change structure for the scalable phase change random access memory array 査読有り

Jung Min Lee, Yuta Saito, Yuji Sutou, Junichi Koike, Jin Won Jung, Masashi Sahashi, Yun Heub Song

Japanese Journal of Applied Physics　53　(4)　2014年4月

DOI： 10.7567/JJAP.53.041801 　

ISSN：0021-4922

eISSN：1347-4065

詳細を見る詳細を閉じる

A multiple phase change structure with Sb79Te21 for switching and Ge1Cu2Te3 for memory was fabricated and evaluated for cell operation. It was confirmed that Sb 79Te21 with smaller contact diameter is successfully operated or used as a switching device with selective current pulses. In addition, it was estimated that this structure provides acceptable on-off ratio and leakage current by structural consideration. From these results, we consider that the structure with multiple phase change materials is suitable as a new device with both switching and memory functions, which gives higher scalability in three-dimensional array architecture by adopting no additional selective devices, such as transistors and diodes. Therefore, we expect that this structure can be one of the candidates for the scalable phase change random access memory (PCRAM). © 2014 The Japan Society of Applied Physics.
The role of deformation twinning in the fracture behavior and mechanism of basal textured magnesium alloys 査読有り

D. Ando, J. Koike, Y. Sutou

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　600　145-152　2014年4月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.msea.2014.02.010 　

ISSN：0921-5093

eISSN：1873-4936

詳細を見る詳細を閉じる

AZ31 magnesium alloys were deformed to 10% and to failure strain by tensile loading at room temperature. Scribed grids were drawn by a focused ion beam system (FIB) to visualize the local deformation in each grain. This showed that the magnitude of the strain was distributed non-uniformly in each grain. It was found that the low-strain grains accompanied {10-12} twins, while the severely strained grains accompanied {10-11}-{10-12} double twins. Cracks nucleated at the double twins and tended to propagate along {10-12} twin interfaces as well as within grains. Furthermore, fractography revealed three types of microstructural features: dimples, elliptic facets and sheared dimples. Most abundant were the dimples formed by ductile failure. The elliptic facets appeared to be due to crack propagation along the {10-12} twin interfaces. The sheared dimples were frequently observed in connection with localized shear deformation within the double twins. These results led us to conclude that premature and catastrophic failure of Mg alloys is mainly associated with double twins. Prevention of double twinning is essential to improve the ductility of Mg alloys. (c) 2014 Elsevier B.V. All rights reserved.
Barrier Properties of CVD Mn Oxide Layer to Cu Diffusion for 3-D TSV 査読有り

Kang-Wook Lee, Hao Wang, Ji-Cheol Bea, Mariappan Murugesan, Yuji Sutou, Takafumi Fukushima, Tetsu Tanaka, Junichi Koike, Mitsumasa Koyanagi

IEEE ELECTRON DEVICE LETTERS　35　(1)　114-116　2014年1月
出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI： 10.1109/LED.2013.2287879 　

ISSN：0741-3106

eISSN：1558-0563

詳細を見る詳細を閉じる

The effect of CVD Mn oxide layer as a barrier layer to Cu diffusion for 3-D TSV was characterized. The impact of oxide substrate on the barrier property of a planar Mn oxide was evaluated by XPS method. Planar Mn oxide layer of 20-nm thickness formed over thermal oxide showed an excellent barrier property to Cu diffusion after annealing at 500 degrees C, whereas the Mn oxide over P-TEOS oxide was good enough up to 400 degrees C annealing. On the other hand, the barrier property of Mn oxide upon O3-TEOS oxide was not as good as thermal and P-TEOS oxides. The effect of a vertical Mn oxide layer as a barrier layer to Cu diffusion from Cu TSV was evaluated by C-t analysis. Vertical Mn oxide layer with 20-nm thickness formed on P-TEOS oxide liner in TSV showed better barrier property, when compared with the sputtered Ta barrier layer, up to 400 degrees C annealing condition. However, the barrier property of CVD Mn oxide layer was degraded after annealing at 500 degrees C.
Foreword: Advanced metallization for ULSI applications 査読有り

Nakatsuka, O, Maekawa, K, Nemoto, T, Koike, J

Japanese Journal of Applied Physics　53　(5 SPEC. ISSUE 2)　2014年

DOI： 10.7567/JJAP.53.05G001 　
What can we do about barrier layer scaling to 5 nm node technology ? 査読有り

Koike, J

Digest of Technical Papers - Symposium on VLSI Technology　2014年

DOI： 10.1109/VLSIT.2014.6894408 　
The Electrical and Optical Properties of Fe-O-N Thin Films Deposited by RF Magnetron Sputtering 査読有り

Yukiko Ogawa, Daisuke Ando, Yuji Sutou, Junichi Koike

MATERIALS TRANSACTIONS　54　(10)　2055-2058　2013年10月
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/matertrans.M2013170 　

ISSN：1345-9678

eISSN：1347-5320

詳細を見る詳細を閉じる

The electrical and optical properties of Fe-O-N films were investigated in order to find their possibilities for solar cell application. Fe-O-N thin films were deposited on glass substrates by RF magnetron sputtering using an Ar-N-2-O-2 reactive gas. Under optimum flow rates of nitrogen and oxygen, the Fe-O-N films showed equivalent electrical properties to amorphous Si that has been conventionally used for thin film solar cells. Bandgap narrowing was also observed from 2.0 to 1.9 eV. The observed results were considered to be due to the formation of hematite-magnetite mixed phase, and the introduction of oxygen vacancies and/or nitrogen interstitials.
Oxidation behavior of Cu-Ag core-shell particles for solar cell applications 査読有り

Hoang Tri Hai, Hitoshi Takamura, Junichi Koike

JOURNAL OF ALLOYS AND COMPOUNDS　564　71-77　2013年7月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.jallcom.2013.02.048 　

ISSN：0925-8388

詳細を見る詳細を閉じる

Cu-Ag core-shell particles with 5 mu m-diameter Cu core and 260 nm-thick Ag shell were prepared by an electroless plating method in an aqueous system. The obtained core-shell particles were investigated for their thermal oxidation behavior during baking in air ambient. Thermogravimetric analysis indicated that the oxidation was started at about 200 degrees C. This oxidation temperature was a little higher than that (150 degrees C) of Cu particles without Ag shell. Microstructure observation of the core-shell particles baked in Ar ambient revealed the agglomeration of Ag shell on the Cu core surface after heating the sample above 200 degrees C, which resulted in direct exposure of the Cu core to ambient. Thus in air ambient, the exposed Cu core was destined to be oxidized. The temperature dependent growth of the agglomerated Ag shell was characterized with an activation energy of 37.56 kJ/mol, which could be assigned to a surface- diffusion-controlled mechanism. This characteristic of the Ag shell would limit the applications of the Cu-Ag core-shell particles to conductive paste for solar cells, wherein baking temperature beyond 200 degrees C in air ambient is generally required to promote good sintering of the paste particles as well as to obtain good electrical contact between metal and silicon. (C) 2013 Elsevier B.V. All rights reserved.
Simultaneous formation of a metallic Mn layer and a MnOx/ MnSixOy barrier layer by chemical vapor deposition at 250°C 査読有り

Kurokawa, A, Sutou, Y, Koike, J, Hamada, T, Matsumoto, K, Nagai, H, Maekawa, K, Kanato, H

Japanese Journal of Applied Physics　52　(5)　2013年5月
出版者・発行元：None
DOI： 10.7567/JJAP.52.05FA02 　

ISSN：0021-4922

eISSN：1347-4065
Investigation of a selective switching device using a phase-change material for a 3-dimensional PCRAM array 査読有り

Jung Min Lee, Yun Heub Song, Yuta Saito, Yuji Sutou, Junichi Koike

Journal of the Korean Physical Society　62　(9)　1258-1263　2013年5月

DOI： 10.3938/jkps.62.1258 　

ISSN：0374-4884

eISSN：1976-8524

詳細を見る詳細を閉じる

A selective switching device utilizing a phase-change material was investigated. In this work, we present a new concept to realize serially a selective switching and memory operation in a multiple phase-change memory with only phase-change materials without any semiconductor switching device. A phase-change material for selective switching can be expected to have a higher resistance amorphous phase and to show lower melting and crystallization temperatures than a phase-change material for a memory. Here, we present a structural method to obtain the above requirements. In addition, we confirm the switching operation by a selective current pulse for multiple phase-change materials from the experiment. From these results, we expected that one of the multiple phasechange materials can be replaced in a switching device without the need for an additional selective device, and that such a device would be feasible for 3-dimensional PCM architecture. © 2013 The Korean Physical Society.
Optical contrast and laser-induced phase transition in GeCu <inf>2</inf>Te<inf>3</inf> thin film 査読有り

Yuta Saito, Yuji Sutou, Junichi Koike

Applied Physics Letters　102　(5)　2013年2月4日

DOI： 10.1063/1.4791567 　

ISSN：0003-6951

詳細を見る詳細を閉じる

Fast crystallization and low power amorphization are essential to achieve rapid data recording and low power consumption in phase-change memory. This work investigated the laser-induced phase transition behaviors of GeCu 2Te3 film based on the reflectance of amorphous and crystalline states. The GeCu2Te3 film showed a reflectance decrease upon crystallization, which was the opposite behavior in Ge 2Sb2Te5 film. The crystallization starting time of the as-deposited GeCu2Te3 film was as fast as that of the as-deposited Ge2Sb2Te5 film. Furthermore, the GeCu2Te3 crystalline film was found to be reamorphized by laser irradiation at lower power and shorter pulse width than the Ge 2Sb2Te5. © 2013 American Institute of Physics.
Deformation and strength characterization of Mg alloys with rolled crystallographic textures by crystal plasticity finite element method 査読有り

Tomohiro Ishida, Shinpei Shibutani, Junji Kato, Kenjiro Terada, Takashi Kyoya, Daisuke Ando, Junichi Koike

Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A　79　(808)　1840-1851　2013年
出版者・発行元：Japan Society of Mechanical Engineers
DOI： 10.1299/kikaia.79.1840 　

ISSN：0387-5008

詳細を見る詳細を閉じる

A series of crystal plasticity finite element simulations are conducted to understand the grain-scale deformation process with crystallographic slip and to elucidate the development mechanism of the macroscopic yield strength for magnesium alloys. For the comparative study, different values of initial critical resolved shear stress are set for the basal slip system in a polycrystalline aggregate FE model. The main finding in this study is that the formation of shear bands with localized deformation, which are associated with the macroscopic strength and ductility, is strongly related to the evolution of deformation resistance of separate slip systems and depends on the latent hardening characteristics of the prismatic slip system. © 2013 The Japan Society of Mechanical Engineers.
Fourfold coordinated Te atoms in amorphous GeCu <inf>2</inf>Te <inf>3</inf> phase change material 査読有り

P. Jóvári, Y. Sutou, I. Kaban, Y. Saito, J. Koike

Scripta Materialia　68　(2)　122-125　2013年1月

DOI： 10.1016/j.scriptamat.2012.09.028 　

ISSN：1359-6462

詳細を見る詳細を閉じる

Amorphous GeCu 2Te 3 was investigated by X-ray diffraction and extended X-ray absorption fine structure measurements at the Ge, Cu and Te K-edges. Structural models were obtained by fitting the four experimental datasets simultaneously by reverse Monte Carlo simulation. It was found that Ge-Ge and Cu-Cu bonding are both significant. The average coordination numbers of Cu and Te, as well as Ge, are close to four. The high average coordination number of the network contributes to the enhanced thermal stability of amorphous GeCu 2Te 3. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Structural Characterization of a Manganese Oxide Barrier Layer Formed by Chemical Vapor Deposition for Advanced Interconnects Application on SiOC Dielectric Substrates 査読有り

Nguyen Mai Phuong, Yuji Sutou, Junichi Koike

JOURNAL OF PHYSICAL CHEMISTRY C　117　(1)　160-164　2013年1月
出版者・発行元：AMER CHEMICAL SOC
DOI： 10.1021/jp303241c 　

ISSN：1932-7447

詳細を見る詳細を閉じる

We investigated the microstructure and growth behavior of a manganese oxide layer deposited on SiOC substrates for the purpose of providing a new method to form a thin diffusion barrier layer for advanced LSI interconnections. The Mn oxide layer was formed by chemical vapor deposition (CVD), using bis(ethylcyclopentadienyl)Mn as a precursor and H-2 as a carrier gas at 300 degrees C for 30 min. The Mn oxide layer could be formed on plasma-treated SiOC, but not on as-received SiOC. By using thermal desorption spectroscopy (TDS), moisture absorption in SiOC was evidenced after plasma treatment, using various gases of O-2, N-2, and Ar. Two adsorbed moisture components, physisorbed (alpha) and chemisorbed (beta, gamma), were observed which were responsible for the formation of crystalline MnOx and amorphous MnSixOy, respectively. The position of the Mn oxide layer was also investigated by measuring the variation of the SiOC thickness. The Mn oxide layer was formed within the SiOC substrate. The result indicates that influence on the line resistance value, but influences on the dielectric capacitance value. the Mn oxide barrier layer would have no influence on the line resistance value, but influences on the dielectric capacitance value.
Deposition behavior and substrate dependency of ALD MnOx diffusion barrier layer 査読有り

K. Matsumoto, K. Maekawa, H. Nagai, J. Koike

Proceedings of the 2013 IEEE International Interconnect Technology Conference, IITC 2013　2013年

DOI： 10.1109/IITC.2013.6615566 　

詳細を見る詳細を閉じる

We investigated the possibility of applying an ALD method to form a Cu diffusion barrier layer of MnOx in an attempt to develop a deposition process which would not be influenced by absorbed water in a substrate. The MnOx formed by ALD using (EtCp)2Mn and H2O had the following features. (1) Capability of thickness control of the MnO x layer by changing the ALD cycle number. (2) Capability of the ALD-MnOx formation on low-k dielectrics by surface modification. (3) Good adhesion of the Cu/ALD-MnOx/SiOCH structure showing a fracture toughness of 0.3 MPa·m1/2. (4) Good diffusion barrier property for the thickness of over 1 nm. (5) Minimizing via resistance increase accompanied by the formation of MnOx on Cu. © 2013 IEEE.
Effect of CVD Mn oxide layer as Cu diffusion barrier for TSV 査読有り

Murugesan, M, Bea, J.C, Lee, K.W, Fukushima, T, Tanaka, T, Koyanagi, M, Sutou, Y, Wang, H, Koike, J

2013 IEEE International 3D Systems Integration Conference, 3DIC 2013　2013年

DOI： 10.1109/3DIC.2013.6702364 　
Effects of Si addition on the crystallization behaviour of GeTe phase change materials 査読有り

Y. Saito, Y. Sutou, J. Koike

Journal of Physics D: Applied Physics　45　(40)　2012年10月10日

DOI： 10.1088/0022-3727/45/40/405302 　

ISSN：0022-3727

eISSN：1361-6463

詳細を見る詳細を閉じる

The effects of the addition of Si on the temperature dependence of the electrical resistance and crystallization temperature, T x, of GeTe films were investigated by a two-point probe measurement. T x of the (GeTe) 100xSi x films increased with increasing Si content from x=0 (188°C) to x=12.6at% (297°C). It was confirmed from XPS measurements that Si-Te bonds were formed in the (GeTe) 100xSi x amorphous film by the addition of Si. The dependence of Si content on the T x of the (GeTe) 100xSi x film was calculated based on Lankhorst's model, which showed a linear relationship between T x and the Si content. In the region of low Si content (x ≤ 3.8at%), the obtained result was in good agreement with the calculated result. Meanwhile, in the region of high Si content (x ≥ 5.4at%), the obtained result considerably deviated from the calculated line. This may be due to the formation of the strongest Si-Si bonds in the amorphous (GeTe) 100xSi x film. It was found from XRD measurement that the (GeTe) 87.4Si 12.6 amorphous film showed crystallization with phase separation into α-GeTe and Si. The obtained results suggested that suitable Si content of the (GeTe) 100xSi x film is in the range 3-7at% because of the high T x, a small temperature interval of crystallization and the absence of phase separation during crystallization. © 2012 IOP Publishing Ltd.
Improved microstructure and ohmic contact of Nb electrode on n-type 4H-SiC 査読有り

Kunhwa Jung, Yuji Sutou, Junichi Koike

THIN SOLID FILMS　520　(23)　6922-6928　2012年9月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.tsf.2012.04.004 　

ISSN：0040-6090

詳細を見る詳細を閉じる

Niobium was deposited as an electrode material on an n-type SiC wafer for power device application. The reaction microstructure and electrical contact property were investigated after annealing at 700 to 1000 degrees C and compared with the results for an Ni electrode. Microstructure-related problems of the Ni electrode could be resolved without sacrificing ohmic contact behavior with a low contact resistivity of 1.53x10(-4) Omega cm(2). Carbon precipitation was completely eliminated with Nb by the formation of carbides, leading to good adhesion upon wire bonding process. At the reaction interface, Nb5Si3 was formed in an epitaxial relationship with SiC, leading to a good interface contact property as well as good interface adhesion. (C) 2012 Elsevier B.V. All rights reserved.
Fast crystal nucleation induced by surface oxidation in Si-doped GeTe amorphous thin film 査読有り

Yuta Saito, Yuji Sutou, Junichi Koike

Applied Physics Letters　100　(23)　2012年6月4日

DOI： 10.1063/1.4726107 　

ISSN：0003-6951

詳細を見る詳細を閉じる

Fast crystallization in the phase change materials (PCMs) used for optical and electrical phase change memory improves their data recording rate. In the present work, it was found that the preferential surface oxidation of Si shortens the nucleation time of Ge 46.55Te 46.55Si 6.9 amorphous films. The nucleation time of a surface-oxidized film was approximately 20 faster than that of a non-oxidized film. This was due to the formation of inhomogeneous nucleation sites at the film surface. These results suggest that preferential surface oxidation of PCM is an effective method to enhance the data recording rate of phase change memory devices. © 2012 American Institute of Physics.
Characterization of Chemically Vapor Deposited Manganese Barrier Layers Using X-ray Absorption Fine Structure 査読有り

James M. Ablett, Christopher J. Wilson, Nguyen Mai Phuong, Junichi Koike, Zsolt Tokei, George E. Sterbinsky, Joseph C. Woicik

JAPANESE JOURNAL OF APPLIED PHYSICS　51　(5)　2012年5月
出版者・発行元：JAPAN SOC APPLIED PHYSICS
DOI： 10.1143/JJAP.51.05EB01 　

ISSN：0021-4922

詳細を見る詳細を閉じる

Chemical vapor deposition of manganese (CVD-Mn) on silicon dielectrics allows the growth of manganese silicate/oxide for use as an effective barrier material for Cu interconnects and is currently under intense evaluation for integration into future sub-22 nm technology. Employing fluorescence X-ray absorption fine structure (XAFS) measurements, we explore the chemical and structural makeup of the barrier layer formation on both SiO2 and low-k dielectrics. (C) 2012 The Japan Society of Applied Physics
Crystallization and electrical characteristics of Ge <inf>1</inf>Cu <inf>2</inf>Te <inf>3</inf> films for phase change random access memory 査読有り

Toshiya Kamada, Yuji Sutou, Masashi Sumiya, Yuta Saito, Junichi Koike

Thin Solid Films　520　(13)　4389-4393　2012年4月

DOI： 10.1016/j.tsf.2012.02.025 　

ISSN：0040-6090

詳細を見る詳細を閉じる

Phase change random access memory (PCRAM) requires an advanced phase change material to lower its power consumption and to enhance its data retention and endurance abilities. The present work investigated the crystallization behaviors and electrical properties of Ge 1Cu 2Te 3 compound films with a low melting point of about 500 °C for PCRAM application. Sputter-deposited Ge 1Cu 2Te 3 amorphous films showed a high crystallization temperature of about 250 °C. The Ge 1Cu 2Te 3 amorphous film showed an electrical resistance decrease of over 10 2-fold and exhibited a small increase in thickness of 2.0% upon crystallization. The Ge 1Cu 2Te 3 memory devices showed reversible switching behaviors and exhibited a 10% lower power consumption for the reset operation than the conventional Ge 2Sb 2Te 5 memory devices. Therefore, the Ge 1Cu 2Te 3 compound is a promising phase change material for PCRAM application. © 2012 Elsevier B.V. All rights reserved.
Crystallization process and thermal stability of Ge <inf>1</inf>Cu <inf>2</inf>Te <inf>3</inf> amorphous thin films for use as phase change materials 査読有り

Y. Sutou, T. Kamada, M. Sumiya, Y. Saito, J. Koike

Acta Materialia　60　(3)　872-880　2012年2月

DOI： 10.1016/j.actamat.2011.10.048 　

ISSN：1359-6454

詳細を見る詳細を閉じる

The crystallization kinetics of amorphous Ge 1Cu 2Te 3 (GCT) films prepared by sputter deposition were investigated by differential scanning calorimetry under non-isothermal conditions. An exothermic peak due to crystallization was observed in the temperature range 230-270 °C. It was found that the local activation energy for crystallization is almost constant when the crystallization fraction is less than about 0.15 and then monotonically decreases with increasing crystallization fraction, which indicates that the crystallization of amorphous GCT films is a multi-step mechanism. The local Avrami exponent decreased from more than 5 to 1.7 with increasing crystallization fraction. It was demonstrated by the Ozawa method that GCT amorphous films show a higher thermal stability than Ge 2Sb 2Te 5 amorphous films, with an estimated failure time of over 70 years at 125 °C, which is well beyond the data retention requirements of the International Technology Roadmap for Semiconductors. In addition, the thickness change in GCT amorphous films accompanying crystallization was measured by atomic force microscopy. The GCT amorphous film was found to show a thickness increase of only 2.0% on crystallization, which is desirable to enhance the endurance of phase change random access memory devices. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
A new constitutive model for crystal plasticity with deformation twinning 査読有り

Ishida, T, Shibutani, S, Kato, J, Terada, K, Kyoya, T, Ando, D, Koike, J

Transactions of the Japan Society for Computational Engineering and Science　2012　2　2012年

eISSN：1347-8826
Crystallization behavior and resistance change in eutectic Si <inf>15</inf>Te <inf>85</inf> amorphous films 査読有り

Yuta Saito, Yuji Sutou, Junichi Koike

Thin Solid Films　520　(6)　2128-2131　2012年1月1日

DOI： 10.1016/j.tsf.2011.09.012 　

ISSN：0040-6090

詳細を見る詳細を閉じる

Crystallization process and the corresponding electrical resistance change were investigated in eutectic Si 15Te 85 amorphous thin films. The Si 15Te 85 amorphous film showed two-stage crystallization process upon heating. In the first stage, the Si 15Te 85 amorphous crystallized into Te crystals at 175 °C. In the second stage, the residual amorphous phase crystallized into Si 2Te 3 crystals at above 300 °C accompanying the resistance drop. Before the second crystallization, the electrical resistance once increased in the temperature range of about 250-295 °C. This phenomenon can be explained by considering the formation of amorphous phase with a high electrical resistivity. © 2011 Elsevier B.V. All rights reserved.
Interface reaction behavior between Mn and SiO2 formed by RF sputter deposition 査読有り

Byeong Taek Bae, Hideaki Nakano, Junichi Koike

MATERIALS INTEGRATION　508　48-51　2012年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/www.scientific.net/KEM.508.48 　

ISSN：1013-9826

詳細を見る詳細を閉じる

The present work investigated the effects of adsorbed moisture in substrates on the growth of a self-forming barrier layer between Mn and SiO2. In order to control the adsorbed moisture, the substrates of TEOS-SiO2/Si were pre-annealed in vacuum at various temperatures. Then, Mn thin films were deposited on the substrate with or without pre-annealing. The results of interface reaction after additional post-annealing indicated that an interface reaction layer becomes thinner with decreasing the adsorbed moisture in the SiO2 substrates.
The thickness-ratio effects of Ni/Nb electrode on wire bonding strength with n-type 4H-SiC 査読有り

Kunhwa Jung, Daisuke Ando, Yuji Sutou, Tetsuya Oyamada, Masamoto Tanaka, Junichi Koike

SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2　717-720　829-+　2012年
出版者・発行元：TRANS TECH PUBLICATIONS LTD
DOI： 10.4028/www.scientific.net/MSF.717-720.829 　

ISSN：0255-5476

詳細を見る詳細を閉じる

The thickness-ratio effects of Ni/Nb bi-layer electrodes were studied for power device applications. The reaction microstructure and electrical contact property were investigated after annealing at 1000 degrees C and compared with the results of an Ni electrode. Microstructure-related problems of the Ni electrode could be successfully resolved without sacrificing ohmic contact behavior by the addition of Nb to a Ni based electrode. Carbon precipitation on the electrode surface was reduced with increasing Nb thickness by the formation of carbides, which led to good adhesion between the electrode and a wiring pad. High shear strength of the bonded wire was also obtained by the elimination of the carbon precipitates on the electrode surface.
Multiresistance characteristics of PCRAM with Ge <inf>1</inf>Cu <inf>2</inf>Te <inf>3</inf> and Ge <inf>2</inf> Sb <inf>2</inf>Te <inf>5</inf> films 査読有り

Yuta Saito, Yun Heub Song, Jung Min Lee, Yuji Sutou, Junichi Koike

IEEE Electron Device Letters　33　(10)　1399-1401　2012年

DOI： 10.1109/LED.2012.2210534 　

ISSN：0741-3106

詳細を見る詳細を閉じる

A phase-change random access memory (PCRAM) with multiresistance characteristics was fabricated. In this multiple PCRAM device, Ge 1sb 2Te 5 (GST) and Ge1Cu2Te 3 (GCT) are utilized as phase-change materials to realize high- and middle-resistance states, respectively. Since GCT has simultaneously lower melting point and higher crystallization temperature than GST, recording of multiple states was directly achieved without any additional step. It was confirmed that multiple resistances of 10 3, 10 4, and 105\ \Omega were measured by a selection of current pulse during crystallization. From this work, it is expected that a device structure with GST and GCT can be one of the candidates for an effective multilevel cell operation in PCRAM. © 2012 IEEE.
Simultaneous formation of a metallic Mn layer and a MnOx / MnSixOy barrier layer by chemical vapor deposition at 250°C 査読有り

Kurokawa, A, Sutou, Y, Koike, J, Hamada, T, Matsumoto, K, Nagai, H, Maekawa, K, Kanato, H

Advanced Metallization Conference (AMC)　109-117　2012年

ISSN：1540-1766
Effect of Nitrogen Content on the Microstructure and Mechanical Properties of Ti-Mo-N Coating Films 査読有り

Shoko Komiyama, Yuji Sutou, Junichi Koike

METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE　42A　(11)　3310-3315　2011年11月
出版者・発行元：SPRINGER
DOI： 10.1007/s11661-010-0522-x 　

ISSN：1073-5623

詳細を見る詳細を閉じる

Effects of nitrogen content on the microstructure, hardness, and friction coefficient of Ti-Mo-N coating films were investigated. Ti-Mo-N films were deposited onto an AISI304 stainless steel substrate by reactive r.f. sputtering in the mixture of argon and nitrogen gases with various gas flow rates. The hardness and friction coefficients were measured by nanoindentation and ball-on-disk testing systems, respectively. The hardness of the Ti-Mo-N films increased with increasing a nitrogen gas flow rate (f(N2)) and showed a maximum hardness of about 30 GPa at a f(N2) = 0.3 ccm. On the one hand, the films deposited at f(N2) >= 1.0 ccm showed a constant hardness value of approximately 25 GPa. On the other hand, the friction coefficient of the Ti-Mo-N film decreased with increasing N content and was 0.44 in the film deposited at f(N2) = 2.0 ccm.
Effects of Adsorbed Moisture in SiO2 Substrates on the Formation of a Mn Oxide Layer by Chemical Vapor Deposition 査読有り

Nguyen Mai Phuong, Koji Neishi, Yuji Sutou, Junichi Koike

JOURNAL OF PHYSICAL CHEMISTRY C　115　(34)　16731-16736　2011年9月
出版者・発行元：AMER CHEMICAL SOC
DOI： 10.1021/jp201299w 　

ISSN：1932-7447

詳細を見る詳細を閉じる

Manganese oxide formed by a chemical vapor deposition (CVD) method is a promising candidate for an ultrathin diffusion barrier layer in the interconnect structure of advanced semiconductor devices. This study placed emphasis on the adsorbed moisture in a hydrophilic SiO2 substrate and investigated the effects of the adsorbed moisture on the formation behavior, structure and composition of the CVD Mn oxide layer. The SiO2 substrates were preannealed at 150 to 500 degrees C for 1 h to control the type and amount of the residual adsorbed moisture. A Mn oxide layer was subsequently deposited by thermal CVD of bis(ethylcyclopentadienyl)Mn at 200 degrees C for 30 min. The Mn oxide layer deposited on an as-received substrate was composed of the bilayer of crystalline MnOx and amorphous MnSixOy. The Mn oxide layer deposited on a preannealed substrate was composed of the single layer of amorphous MnSixOy. The crystalline MnOx, layer was formed by the reaction of the Mn precursor with physisorbed moisture on the as-received SiO2. The amorphous MnSixOy was due to the reaction with chemisorbed moisture on both the as-received and the preannealed SiO2. Results of the present work indicate the importance of controlling the adsorbed moisture of the substrates in order to obtain a Mn oxide layer with desired structure and thickness as a diffusion barrier layer.
Structural and Electronic Properties of a Mn Oxide Diffusion Barrier Layer Formed by Chemical Vapor Deposition 査読有り

Vijay Kumar Dixit, Koji Neishi, Noboru Akao, Junichi Koike

IEEE TRANSACTIONS ON DEVICE AND MATERIALS RELIABILITY　11　(2)　295-302　2011年6月
出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI： 10.1109/TDMR.2011.2141671 　

ISSN：1530-4388

eISSN：1558-2574

詳細を見る詳細を閉じる

A diffusion barrier layer of a few nanometers in thickness is required for a Cu/SiO2 interconnect structure for advanced integrated circuits (ICs). This paper reports a new barrier material and process by chemical vapor deposition (CVD) of a Mn oxide layer using a bis(ethylcyclopentadienyl)manganese precursor. A good adhesion was obtained when the MnOx layer was deposited below 300 degrees C because of the small amount of carbon inclusion within the layer. The metal-oxide-semiconductor samples of Cu/MnOx/SiO2/p-Si showed a very low leakage current of less than 10(-7) A/cm(2) at 4 MV/cm and a negligible shift of the flat-band voltage after thermal annealing and bias temperature annealing. The obtained results indicated that the CVD-deposited MnOx is an excellent diffusion barrier layer for advanced ICs.
P-23: The contact properties an d TFT structures of a-IGZO TFTs combined with cu-mn alloy electrodes 査読有り

Yun, P.S, Naito, M, Kumagai, R, Sutou, Y, Koike, J

Digest of Technical Papers - SID International Symposium　42 1　1177-1180　2011年
Metal Reaction Doping and Ohmic Contact with Cu-Mn Electrode on Amorphous In-Ga-Zn-O Semiconductor 査読有り

P. S. Yun, J. Koike

JOURNAL OF THE ELECTROCHEMICAL SOCIETY　158　(10)　H1034-H1040　2011年
出版者・発行元：ELECTROCHEMICAL SOC INC
DOI： 10.1149/1.3621723 　

ISSN：0013-4651

eISSN：1945-7111

詳細を見る詳細を閉じる

We investigated the microstructure and electrical properties of Cu and Cu-Mn alloy on amorphous In-Ga-Zn-O (a-IGZO) oxide semiconductor in order to explore a high performance electrode material for thin film transistors (TFTs) in advanced flat panel displays. Current-voltage measurements of metal/semiconductor contact structure showed a non-linear behavior with Cu, while a good ohmic behavior [rho(C) = (1.2-2.9) x 10(-4) Omega.cm(2)] with the Cu-Mn alloy after annealing at 250 degrees C for 1 h. Transfer and output characteristics of TFT structure also showed excellent performance with the Cu-Mn alloy. The good electrical property was due to the formation of a highly doped n(+) a-IGZO layer with the carrier density of 1.4 x 10(20) cm(-3). The donor doping could be achieved simply by heat treatment to promote the oxidation of Mn and the reduction of a-IGZO. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3621723] All rights reserved.
The contact properties and TFT structures of a-IGZO TFTs combined with Cu-Mn alloy electrodes 査読有り

Yun, P.S, Naito, M, Kumagai, R, Sutou, Y, Koike, J

49th Annual SID Symposium, Seminar, and Exhibition 2011, Display Week 2011　3　1177-1180　2011年
Roles of deformation twinning and dislocation slip in the fatigue failure mechanism of AZ31 Mg alloys 査読有り

J. Koike, N. Fujiyama, D. Ando, Y. Sutou

SCRIPTA MATERIALIA　63　(7)　747-750　2010年10月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.scriptamat.2010.03.021 　

ISSN：1359-6462

詳細を見る詳細を閉じる

Fatigue tests were performed on AZ31 Mg alloys at room temperature in tension cycles. Deformation twinning of the {1 0 (1) over bar 2} type was observed both below and above the fatigue limit, indicating that the {1 0 (1) over bar 2} twins do not contribute directly to fatigue failure. However, prismatic slip and substantial cyclic hardening were observed above the fatigue limit. Progressive hardening gave rise to {1 0 1 1}-{1 0 (1) over bar 2} double twinning that led to the formation of large surface steps, cracks and eventual failure. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Relationship between deformation twinning and surface step formation in AZ31 magnesium alloys 査読有り

D. Ando, J. Koike, Y. Sutou

ACTA MATERIALIA　58　(13)　4316-4324　2010年8月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.actamat.2010.03.044 　

ISSN：1359-6454

詳細を見る詳細を閉じる

Rolled sheets of AZ31 Mg alloys were deformed at room temperature under tension along the rolling direction. A number of large surface steps were observed in the region near the fractured edge. Transmission electron microscopy showed the presence of twins under these steps. Crystallographic analysis indicated that the twins are of the {1 0 (1) over bar 1}-{1 0 (1) over bar 2} double twin type with their basal planes tilted by 37 degrees with respect to the basal planes of the matrix, which is considered to make basal dislocation slip highly active within the twin. The localized deformation within the twins may lead to the formation of crack-like faults and to failure in a macroscopically brittle manner. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Effect of Heat Treatment on the Hardness of Ti-Mo-N Films Deposited by RF Reactive Magnetron Sputtering 査読有り

Shoko Komiyama, Yuji Sutou, Junichi Koike

MATERIALS TRANSACTIONS　51　(8)　1467-1473　2010年8月
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/matertrans.M2010119 　

ISSN：1345-9678

eISSN：1347-5320

詳細を見る詳細を閉じる

The effects of heat treatment on the microstructure and hardness of Ti-Mo-N films were investigated for various N contents. Ti-Mo-N films were deposited onto a AISI304 stainless steel substrate by reactive RF magnetron sputtering in a mixture of argon (7.5 ccm) and nitrogen (0-2.0 ccm) gases using a Ti50Mo50 target. X-ray analysis of the as-deposited films indicated that the main phases of the Ti-Mo-N film produced at nitrogen gas flow rates of <= 0.2 ccm and >0.3 ccm were bcc-(Ti,Mo) and delta-(Ti,Mo)N phase, respectively. As-deposited films were heat treated in an argon atmosphere at 300-1100 degrees C for 30 min. Hardness was measured using a nanoindentation system. There was almost no change in the hardness of the Ti-Mo-N films deposited at f(N2), = 2.0 ccm after heat treatment. In contrast, the hardness of the films deposited at f(N2) = 0.2 and 0.3 ccm was significantly increased by heat treatment at temperatures higher than 900 degrees C. In particular, the film deposited at f(N2) = 0.3 ccm showed a maximum hardness of approximately 35 GPa by heat treatment at 1000 degrees C for 30 min. X-ray measurements and transmission electron microscopy (TEM) observations indicated that the increment of hardness in the Ti-Mo-N film deposited at f(N2) = 0.3 ccm was due to the formation of a bcc-(Ti,Mo) phase in a delta-(Ti,Mo)N phase. [doi:10.2320/matertrans.M2010119].
Effects of Water Desorption from SiO2 Substrates on the Thickness of Manganese Oxide Diffusion Barrier Layer Formed by Chemical Vapor Deposition 査読有り

Kenji Matsumoto, Koji Neishi, Hitoshi Itoh, Hidenori Miyoshi, Hiroshi Sato, Shigetoshi Hosaka, Junichi Koike

JAPANESE JOURNAL OF APPLIED PHYSICS　49　(5)　05FA121-05FA122　2010年5月
出版者・発行元：JAPAN SOC APPLIED PHYSICS
DOI： 10.1143/JJAP.49.05FA12 　

ISSN：0021-4922

詳細を見る詳細を閉じる

A manganese oxide (MnOx) diffusion barrier layer was formed by chemical vapor deposition (CVD) on SiO2 substrates with or without pre-annealing. The thickness dependence of the MnOx layer was investigated in relation to the desorption behavior of water vapor from the substrates. A good correlation was found between MnOx thickness and the amount of desorbed water vapor. It is necessary to control the amount of absorbed water in the substrate to form a thin MnOx barrier layer with good thickness reproducibility. (C) 2010 The Japan Society of Applied Physics
Selective Formation of a SnO2 Cap Layer, Its Growth Behavior, and Oxidation Resistance 査読有り

Yoshihito Fujii, Junichi Koike, Yuji Sutou, Zifeng Li, Koji Neishi

JAPANESE JOURNAL OF APPLIED PHYSICS　49　(5)　05FA021-05FA024　2010年5月
出版者・発行元：JAPAN SOC APPLIED PHYSICS
DOI： 10.1143/JJAP.49.05FA02 　

ISSN：0021-4922

詳細を見る詳細を閉じる

In this paper, we propose a new method of cap-layer formation. The cap layer of SnO2 is formed by the displacement plating of Sn, followed by the oxidation of the plated Sn. An excellent plating selectivity was found between Cu and SiO2, but not with SiOCH. The SnO2 layer of 90 nm thickness showed a good oxidation resistance of the underlying Cu after heat treatment at 480 degrees C in air (P-O2 = 105 Pa). In contrast, the SnO2 layers of 6 and 9 nm thickness showed oxidation resistance at 400 degrees C in Ar+10 ppm O-2 (P-O2 = 1 Pa), but not in Ar+1000 ppm O-2 (P-O2 = 100 Pa). (C) 2010 The Japan Society of Applied Physics
Effect of Heat Treatment on the Hardness of Ti-Mo-N Coating Films Deposited by RF Reactive Magnetron Sputtering 査読有り

Shoko Komiyama, Yuji Sutou, Junichi Koike

JOURNAL OF THE JAPAN INSTITUTE OF METALS　74　(3)　135-141　2010年3月
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/jinstmet.74.135 　

ISSN：0021-4876

eISSN：1880-6880

詳細を見る詳細を閉じる

Effects of heat treatment on microstructure and hardness of Ti-Mo-N coating films were investigated for various N contents. Ti-Mo-N films were deposited onto a stainless steel substrate by a reactive RF sputtering process in the mixture of argon (7.5 ccm) and nitrogen (0 similar to 2.0 ccm) gases using Ti50Mo50 target. X ray results of as deposited films indicated that the main phase of the Ti-Mo-N film was a bcc (Ti, Mo) phase at a nitrogen flow rate (f(N2)) <= 0.2 ccm and a delta-(Ti, Mo)N phase at f(N2) over 0.3 ccm. The Ti-Mo-N films so obtained were heat treated in argon atmosphere at 300 similar to 1100 degrees C for 30 minutes. Hardness was measured by a nanoindentation system. The hardness of the Ti-Mo-N films deposited at f(N2)= 2.0 ccm hardly changed with heat treatment. In contrast, the hardness of the films deposited at jrN,= 0.2 and 0.3 ccm was drastically increased by heat treatment at temperatures higher than 900 degrees C. In particular, the film deposited at f(N2) = 0.3 ccm showed the maximum hardness of about 35 GPa by heat treatment at 1000 degrees C for 30 minutes. X ray measurement and TEM observation indicated that the increment of hardness in the Ti-Mo-N film at f(N2)= 0.3 ccm is due to the formation of a bcc-(Ti, Mo) phase in a delta-(Ti, Mo)N phase.
Graded composition and valence states in self-forming barrier layers at Cu-Mn/SiO2 interface 査読有り

Y. Otsuka, J. Koike, H. Sako, K. Ishibashi, N. Kawasaki, S. M. Chung, I. Tanaka

APPLIED PHYSICS LETTERS　96　(1)　2010年1月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.3269602 　

ISSN：0003-6951

詳細を見る詳細を閉じる

A self-forming diffusion barrier (SFB) layer was formed at Cu-Mn/SiO2 interface. Spatial variation of the chemical composition and valence state of the elements in the SFB was investigated in a subnanometer resolution using electron energy loss spectroscopy and transmission electron microscopy. The SFB was found to have a layered structure with graded compositions of nanocrystalline MnO and amorphous MnSiO3. The valence state of Mn was found to be +2 in the MnO layer and gradually increased to +3 in the MnSiO3 layer. The reported dielectric constant of the SFB could be explained by the observed composition and microstructure.
The Relationships between Grain Boundary Sliding and Anisotropic Dislocation Plasticity in AZ31 Magnesium Alloys at Room Temperature 査読有り

D. Ando, Y. Sutou, J. Koike

MAGNESIUM TECHNOLOGY 2010　245-247　2010年
出版者・発行元：MINERALS, METALS & MATERIALS SOC
ISSN：1545-4150

詳細を見る詳細を閉じる

Grain boundary sliding at room temperature was investigated in AZ31 Mg alloys in relation with the difference of plastic deformability between two neighboring grains on both sides of the slid grain boundary. The Schmid factors of basal and prismatic slip systems were used as a measure of the deformability of a given grain. The difference in basal slip activity appears to be a major cause for the slip-induced grain boundary sliding.
Structural and electrical characteristics of Cu-Mn/SiOC/Si 査読有り

Chung, S.M, Koike, J, Otsuka, Y, Sako, H, Ishibashi, K, Kawasaki, N

Advanced Metallization Conference (AMC)　242　2010年
Crystallization behavior of Ge<inf>1</inf>Cu<inf>2</inf>Te<inf>3</inf> amorphous film 査読有り

Y. Sutou, T. Kamada, Y. Saito, M. Sumiya, J. Koike

Materials Research Society Symposium Proceedings　1251　7-12　2010年

DOI： 10.1557/proc-1251-h05-08 　

ISSN：0272-9172

詳細を見る詳細を閉じる

The electrical resistance on the crystallization process of sputtered-deposited Ge1Cu2Te3 film was investigated by a two-point probe method. It was found that the amorphous Ge1Cu2Te3 film crystallized into a single Ge1Cu2Te3 phase with a chalcopyrite structure, which lead to a large resistance drop. The crystallization temperature of the Ge1Cu2Te3 amorphous film was about 250°C, which was about 70°C higher than the conventional Ge2Sb 2Te5 amorphous film. The activation energy for the crystallization of the Ge1Cu2Te3 amorphous film was higher than that of the Ge2Sb2Te5 amorphous film. The Ge1Cu2Te3 compound with a low melting point can be expected to be suitable as a phase change material for PCRAM. © 2010 Materials Research Society.
P-33: Cu-Mn electrodes for a-Si TFT and its electrical characteristics 査読有り

Koike, J, Hirota, K, Naito, M, Yun, P, Sutou, Y

48th Annual SID Symposium, Seminar, and Exhibition 2010, Display Week 2010　3　1343-1346　2010年
Electrical resistance change with crystallization in Si-Te amorphous thin films 査読有り

Yuta Saito, Yuji Sutou, Junichi Koike

Materials Research Society Symposium Proceedings　1251　99-104　2010年

DOI： 10.1557/proc-1251-h06-07 　

ISSN：0272-9172

詳細を見る詳細を閉じる

The electrical resistance change of amorphous SixTe 100-x (x: 10-23) films during heating was investigated by a two-point probe method. The SixTe100-x films showed two-stage crystallization processes. The film was firstly crystallized to Te and subsequently crystallized to Si2Te3 with an electrical resistance drop. The first crystallization temperature Tx1st slightly increased with increasing Si content, while the second crystallization temperature Tx2nd was independent on the composition and was a constant temperature of 310°C. In all films, the electrical resistance once increased in the temperature range from 250 to 295°C before the crystallization of the Si2Te3. This temporal resistance increase could be explained by considering a formation of high-resistivity Si-rich amorphous phase. © 2010 Materials Research Society.
Microstructure Analysis and Electrical Properties of Cu-Mn Electrode for Back-Channel Etching a-IGZO TFT 査読有り

Pilsang Yun, Junichi Koike

IDW'10: PROCEEDINGS OF THE 17TH INTERNATIONAL DISPLAY WORKSHOPS, VOLS 1-3　3　1873-1876　2010年
出版者・発行元：INST IMAGE INFORMATION & TELEVISION ENGINEERS
ISSN：1883-2490

詳細を見る詳細を閉じる

Cu-Mn alloy was investigated as an electrode on a-IGZO film because of its good adhesion, a diffusion barrier and a wet etching selectivity of about 10:1 with IGZO film. Contact property showed non-linear behavior with Al and Cu, while Ohmic contact was obtained with Cu-Mn and Ti after annealing.
Resistivity reduction by external oxidation of Cu-Mn alloy films for semiconductor interconnect application 査読有り

J. Iijima, Y. Fujii, K. Neishi, J. Koike

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B　27　(4)　1963-1968　2009年7月
出版者・発行元：A V S AMER INST PHYSICS
DOI： 10.1116/1.3179167 　

ISSN：1071-1023

詳細を見る詳細を閉じる

A self-forming barrier process using Cu-Mn alloy has been reported to exhibit excellent reliability for interconnect lines in advanced semiconductor devices. However, Mn increases resistivity. In this work, the authors investigated optimum annealing conditions to remove Mn from the Cu-Mn alloy by forming an external Mn oxide and to reduce resistivity to a level of pure Cu. The results were interpreted by an external oxidation mechanism of Mn atoms.
Deposition behavior and diffusion barrier property of CVD MnOx 査読有り

K. Matsumoto, K. Neishi, H. Itoh, H. Sato, S. Hosaka, J. Koike

Proc. Int. Interconnect Technology Conf.　197-199　2009年6月

DOI： 10.1109/IITC.2009.5090386 　
マグネシウム合金の室温変形機構ー変形双晶に注目してー招待有り査読有り

小池淳一

軽金属　59　(5)　272-277　2009年5月
Chemical Vapor Deposition of Mn and Mn Oxide and their Step Coverage and Diffusion Barrier Properties on Patterned Interconnect Structures 査読有り

Kenji Matsumoto, Koji Neishi, Hitoshi Itoh, Hiroshi Sato, Shigetoshi Hosaka, Junichi Koike

APPLIED PHYSICS EXPRESS　2　(3)　036503　2009年3月
出版者・発行元：JAPAN SOCIETY APPLIED PHYSICS
DOI： 10.1143/APEX.2.036503 　

ISSN：1882-0778

詳細を見る詳細を閉じる

Chemical vapor deposition of bis(ethylcyclopentadienyl) manganese, (EtCP)(2)Mn, was performed on a patterned interconnect structure to obtain a thin conformal layer with a good diffusion barrier property for advanced Si devices. Deposition of (EtCP)(2)Mn on SiO(2) formed a conformal layer of Mn oxide within a contact hole with a uniform thickness of 3 to 4 nm. Similar conformal formation of Mn oxide was obtained on SiO(2) in the vias and trenches of a dual-damascene structure. The deposition of (EtCP)(2)Mn on Cu, however, formed a solid solution with Cu. The solute Mn migrated toward the interface Of Cu/SiO(2) to form Mn oxide. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/APEX.2.036503
Microstructural invetigation of twins under the fracture surface in AZ31 Mg alloys 査読有り

D. Ando, J. Koike

2009 Magnesium Technology　537-540　2009年2月
Phase formation and growth kinetics of an interface layer in Ni/SiC 査読有り

Kenichiro Terui, Atsuko Sekiguchi, Hiroshi Yoshizaki, Junichi Koike

Materials Science Forum　600-603　631-634　2009年

DOI： 10.4028/3-908453-11-9 　
Adhesion and Cu diffusion barrier properties of a MnOx barrier layer formed with thermal MOCVD 査読有り

K. Neishi, D. Vijay, S. Aki, J. Koike, K. Matsumoto, H. Sato, H. Itoh, S. Hosaka

Proc. 2009 MRS Spring Meeting　D04-10　2009年
Electric transport properties of Cu/MnOx/SiO2/p-Si MOS devices 査読有り

D. Vijay, K. Neishi, J. Koike

Proc. 2009 MRS Spring Meeting　D04-11　2009年
Effects of plasma surface treatment on the self-forming barrier process in porous SiOCH 査読有り

S-M. Chung, J. Koike, Zs. Tokei

Proc. 2008 MRS Spring Meeting　2009年
Influence of moisture on the CVD formation of a MnOx barrier layer 査読有り

K. Neishi, K. Matsumoto, H. Sato, H. Itoh, S. Hosaka, J. Koike

Advanced metallization conference 2008　307-311　2009年
CVD法による先端LSI-Cu配線用MnOxバリア層形成と信頼性評価

根石浩司, V. K. Dixit, 松本賢治, 伊藤仁, 佐藤浩, 保坂重敏, 小池淳一

LSIにおける原子輸送・応力問題第14回研究会予稿集　29-32　2009年
Stress relaxation during isothermal annealing in electroplated Cu films 査読有り

Soo-Jung Hwang, Young-Chang Joo, Junichi Koike

Thin Solid Films　516　7588-7594　2008年8月

DOI： 10.1016/j.tsf2008.03.030 　
Formation of a manganese oxide barrier layer with thermal chemical vapor deposition for advanced large-scale integrated interconnect structure 査読有り

Koji Neishi, Shiro Aki, Kenji Matsumoto, Hiroshi Sato, Hitoshi Itoh, Shigetoshi Hosaka, Junichi Koike

APPLIED PHYSICS LETTERS　93　(3)　032106　2008年7月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2963984 　

ISSN：0003-6951

詳細を見る詳細を閉じる

Advanced large-scale integrated interconnect structure faces a major challenge in forming a thin and conformal diffusion barrier layer. We deposited a Mn oxide layer by thermal chemical vapor deposition (CVD) on SiO(2) substrates and investigated deposition behavior and diffusion barrier property. A thin Mn oxide layer was formed with a uniform thickness of 2.6-10 nm depending on deposition temperature between 100 and 400 degrees C. Heat-treated samples of Cu/CVD-Mn oxide/SiO(2) indicated no interdiffusion at 400 degrees C for 100 h. The CVD of the Mn oxide layer was found to be an excellent barrier formation process.
Evaluation of interface adhesion strength in Cu/(Ta-x% n, Ta/TaN)/SiO2/Si by nanoscratch test 査読有り

Atsuko Sekiguchi, Junichi Kolke

JAPANESE JOURNAL OF APPLIED PHYSICS　47　(2)　1042-1049　2008年2月
出版者・発行元：JAPAN SOC APPLIED PHYSICS
DOI： 10.1143/JJAP.47.1042 　

ISSN：0021-4922

詳細を見る詳細を閉じる

The adhesion strength of Cu/(Ta-x% N, Ta/TaN)/SiO2/Si was investigated and the feasibility of the nanoscratch technique was evaluated. Because of the grain orientation dependence of critical load owing to elastic/plastic anisotropy, the interface adhesion measured in the mix-textured films of < 111 > and < 100 > showed a wide-range data spread to higher adhesion strength compared with the highly < 111 > textured films. The adhesive energy derived from the measured critical. load by considering the residual stress and the effect of grain orientation by the aid Of finite element method calculation showed a reasonable agreement with theoretical work of adhesion. It was revealed that the adhesion strength of Cu/Ta-x% N decreases with increasing nitrogen concentration. This tendency can be associated with increasing number of weak Cu-N bonding along the Cu/barrier interface.
Formation of Mn oxide with thermal CVD and its diffusion barrier property between Cu and SiO2 査読有り

K. Neishi, S. Aki, J. Iijima, J. Koike

Proc. 2008 MRS Spring Meeting　2008年
Possibilities and problems of self-forming barrier process for advanced LSI metallization 査読有り

J. Koike, J. Iijima, K. Neishi

ADVANCED METALLIZATION CONFERENCE 2007 (AMC 2007)　23　3-9　2008年
出版者・発行元：MATERIALS RESEARCH SOCIETY
ISSN：0886-7860

詳細を見る詳細を閉じる

Self-forming barrier layer was investigated by deposition of Cu-Mn alloy films on dielectric layer. For the dielectric materials, conventional TEOS-SiO2 and advanced low-k SiOC were employed. Thin barrier layer could be successfully formed on SiO2 and dense SiOC. On the contrary, porous SiOC had a problem with Cu penetration in an as-deposited state. In order to use the self-forming barrier process on advanced porous low-k materials, surface treatment and pore sealing may be necessary.
Finite element method analysis of nanoscratch test for the evaluation of interface adhesion strength in Cu thin films on si substrate 査読有り

Atsuko Sekiguchi, Junichi Koike

JAPANESE JOURNAL OF APPLIED PHYSICS　47　(1)　249-256　2008年1月
出版者・発行元：JAPAN SOC APPLIED PHYSICS
DOI： 10.1143/JJAP.47.249 　

ISSN：0021-4922

詳細を見る詳細を閉じる

Mechanical processes of the nanoscratch test are investigated using a finite element analysis of Cu/Ta/SiO(2)/Si multilayer films. The calculated stress distribution at the moment of delamination suggests that delamination occurs in a small region of approximately 100 nm. The driving force for delamination is the stress concentration due to strain-incompatibility at the Cu/Ta interface resulting from the large plastic deformation in Cu. The degree of stress concentration is found to depend on internal variables, such as plastic deformation, residual stress, and the elastic modulus, and on the magnitude of lateral force.
AZ31マグネシウム合金における変形誘起表面起伏と二重双晶の関係査読有り

安藤大輔, 小池淳一

日本金属学会誌　71　(9)　684-687　2007年9月
出版者・発行元：None
DOI： 10.2320/jinstmet.71.684 　

ISSN：0021-4876

eISSN：1880-6880
Growth kinetics and thermal stability of a self-formed barrier layer at Cu-Mn/SiO2 interface 査読有り

J. Koike, M. Haneda, J. Iijima, Y. Otsuka, H. Sako, K. Neishi

JOURNAL OF APPLIED PHYSICS　102　(4)　043527　2007年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2773699 　

ISSN：0021-8979

詳細を見る詳細を閉じる

A thin diffusion barrier was self-formed by annealing at an interface between a Cu-Mn alloy film and a SiO2 substrate. The growth of the barrier layer followed a logarithmic rate law, which represents field-enhanced growth mechanism in the early stage and self-limiting growth behavior in the late stage. The barrier layer was stable at 450 degrees C for 100 h and at 600 degrees C for 10 h. The interface diffusivity was estimated from the morphology change of the barrier layer at 600 degrees C and was found to be smaller than the grain-boundary diffusivity of bulk Cu. (c) 2007 American Institute of Physics.
Growth behavior of self-formed barrier at Cu-Mn/SiO2 interface at 250-450 degrees C 査読有り

M. Haneda, J. Iijima, J. Koike

APPLIED PHYSICS LETTERS　90　(25)　252107　2007年6月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.2750402 　

ISSN：0003-6951

詳細を見る詳細を閉じる

A diffusion barrier layer was self-formed at the interface between Cu-Mn alloy and tetraethylorthosilicate oxide layers at 250-450 degrees C. No interdiffusion occurred across the self-formed barrier layer during annealing at these temperatures up to 100 h. The growth of the barrier layer obeyed a logarithmic law and depended on manganese concentration. The barrier thickness could be controlled in the range of 2-8 nm. (c) 2007 American Institute of Physics.
The effects of Cr oxidation and polyimide degradation on interface adhesion strength in Cu/Cr/polyimide flexible films 査読有り

T. Miyamura, J. Koike

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　445　620-624　2007年2月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.msea.2006.09.097 　

ISSN：0921-5093

詳細を見る詳細を閉じる

Interface adhesion strength of Cu/Cr/polyimide was measured and the effects of annealing atmosphere were investigated. Adhesion strength decreased after annealing in vacuum by 25% and in air by 41%, which was attributed, respectively, to broken carbonyl bonds and to the formation of Cr oxide. Failure mode changed accordingly from cohesive to interfacial at a Cr/polyimide interface. (c) 2006 Elsevier B.V. All rights reserved.
Highly reliable copper dual-damascene interconnects with self-formed MnSixOy barrier layer 査読有り

Takamasa Usui, Hayato Nasu, Shingo Takahashi, Noriyoshi Shimizu, T. Nishikawa, Masaki Yoshimaru, Hideki Shibata, Makoto Wada, Junichi Koike

IEEE TRANSACTIONS ON ELECTRON DEVICES　53　(10)　2492-2499　2006年10月
出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI： 10.1109/TED.2006.882046 　

ISSN：0018-9383

詳細を見る詳細を閉じる

Copper (Cu) dual-damascene interconnects with a self-formed MnSixOy barrier layer were successfully fabricated. Transmission electron microscopy shows that approximately 2-nm thick and continuous MnSixOy layer was formed at the interface of Cu and dielectric SiO2, and that no barrier was formed at the via bottom because no oxygen was at the via bottom during annealing. No leakage-current increase was observed, and electron energy loss analysis shows that no Cu was in SiO2, suggesting that MnSixOy layer has sufficient barrier properties for Cu, and that the concept of self-forming barrier process works in Cu dual-damascene interconnects. Via chain yield of more than 90% and 50% reduction in via resistance were obtained as compared with physical vapor deposited tantalum barrier, because there is no barrier at the via bottom. In addition, no failure in the stress-induced voiding measurement was found even after a 1600-h testing. No failure in electromigration (EM) testing was found, as the electron flow is from the lower level interconnects through via up to upper level interconnects even after 1000-h testing. At least, four times EM lifetime improvement was obtained in the case of electron flow from upper level interconnect through via down to lower level interconnects. Significant EM lifetime improvement is due to no flux divergence site at the via bottom, resulting from there being no bottom barrier at the via.
Enhanced deformation mechanisms by anisotropic plasticity in polycrystalline Mg alloys at room temperature 招待有り査読有り

J Koike

METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE　36A　(7)　1689-1696　2005年7月
出版者・発行元：MINERALS METALS MATERIALS SOC
ISSN：1073-5623

詳細を見る詳細を閉じる

This article presents room-temperature deformation mechanisms in polycrystalline Mg alloys. Dislocation slip of basal < a > and prismatic < a > types are shown to occur nearly at the same ease when the basal planes are tilted in such a way that the Schmid-factor ratio (equivalent to the critically resolved shear stress (CRSS) ratio) of prismatic < a > to basal < a > slip is larger than a value ranging from 1.5 to 2.0, depending on the initial texture distribution and grain size. Grain-boundary sliding (GBS) also occurs at room temperature up to 8 pct of total strain, enhanced by plastic anisotropy as well as by the increasing number of grain-boundary dislocations. Twinning plays an important role in both flow and fracture behaviors. Twins are induced mostly by stress concentrations caused by the anisotropic nature of dislocation slip. Twins can be classified into two types based on their shape: a wide lenticular type and a narrow banded type. The wide twins are {1 0(1) over bar 2} twins appearing in the early stage of deformation and accompany little change of surface height. The narrow twins are {1 0(1) over bar 1} or {3 0(3) over bar 2} appearing in the late stage of deformation and accompany a substantial change in surface height. The formation of the narrow twins seems to give rise to highly localized shear deformation within the twin, leading to strain incompatibility and to final failure.
Self-forming diffusion barrier layer in Cu-Mn alloy metallization 査読有り

J Koike, M Wada

APPLIED PHYSICS LETTERS　87　(4)　No. 041911　2005年7月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.1993759 　

ISSN：0003-6951

詳細を見る詳細を閉じる

Advancement of semiconductor devices requires the realization of an ultrathin diffusion barrier layer between Cu interconnect and insulating layers. The present work investigated the possibility of the self-forming barrier layer in Cu-Mn alloy thin films deposited directly on SiO2. After annealing at 450 degrees C for 30 min, a Mn containing amorphous oxide layer of 3-4 nm in thickness was formed uniformly at the interface. Residual Mn atoms were removed to form a surface oxide layer, leading to a drastic resistivity decrease of the film. No interdiffusion was detected between Cu and SiO2 within the detection limit of x-ray energy dispersive spectroscopy. (c) 2005 American Institute of Physics.
Geometrical c-Titerion for the activation of prismatic slip in AZ61 Mg alloy sheets deformed at room temperature 査読有り

J Koike, R Ohyama

ACTA MATERIALIA　53　(7)　1963-1972　2005年4月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/j.actamat.2005.01.008 　

ISSN：1359-6454

詳細を見る詳細を閉じる

AZ61 Mg alloy was hot-forged and subsequently hot-rolled to a thickness of 1 mm. Tensile anisotropy was investigated at room temperature within the plane of the rolled sheets. When the basal planes were tilted by more than 16.5 degrees towards the tensile axis, basal a) slip was a dominant deformation mechanism and a small elongation of 8% was obtained. Otherwise, prismatic (a) slip became a dominant deformation mechanism and a large elongation of more than 20% was obtained. The basal-plane tilt angle was considered as a geometrical criterion for the activation of the prismatic a) slip at room temperature. The corresponding Schmid factor ratio, or equivalently the critical resolved shear stress ratio of prismatic to basal slip, was found to be 1.5-2.0. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Evolution of stress-induced surface damage and stress-relaxation of electroplated Cu films at elevated temperatures 査読有り

S. J. Hwang, J. Koike, Y. C. Joo

Materials Science Forum　475-479　3641-3646　2005年1月
Newly developed heat-resistant magnesium alloy by Thixomolding 査読有り

T. Tsukeda, K. Saito, M. Suzuki, J. Koike, K. Maruyama

Materials Science Forum　488-489　287-290　2005年1月
Effects of zinc on creep strength and deformation substructures in Mg-Y alloy 招待有り査読有り

M Suzuki, T Kimura, J Koike, K Maruyama

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　387　706-709　2004年12月
出版者・発行元：ELSEVIER SCIENCE SA
DOI： 10.1016/j.msea.2003.12.071 　

ISSN：0921-5093

詳細を見る詳細を閉じる

Compressive Creep behavior of a hot-rolled Mg-Y binary alloy and Mg-Y-Zn ternary alloys was investigated at 650 K. Creep strength of Mg-Y alloys was significantly improved by the addition of zinc. In Mn-Y-Zn alloys, many "planar faults" were formed on (0 0 0 1) matrix planes at high temperatures even with small addition of 0.02 mol% zinc. The stacking fault energy decreased by the simultaneous addition of yttrium (Y) and zinc and many a-dislocations on basal planes were extended. The separation width of the extended dislocations is stabilized by the segregation of yttrium and zinc and the separation width significantly increases under the interaction of partial dislocations on different basal planes. The excellent creep strength in Mg-Y-Zn was explained by the decrease of the mobility of these widely extended dislocations. (C) 2004 Published by Elsevier B.V..
Stree relaxation during isothermal annealing at elevated temperatures in electroplated Cu films 査読有り

SooJung Hwang, Young-Chang Joo, Junichi Koike

MRS Proceeding　in press　2004年
AZ61マグネシウム合金圧延材における破断伸びの異方性と配向性の関係査読有り

大山礼, 小池淳一, 鈴木真由美, 丸山公一

日本金属学会誌　in press　2004年

DOI： 10.2320/jinstmet.68.27 　
Dislocation plasticity and complementary deformation mechanisms in polycrystalline Mg alloys 査読有り

J. Koike

Materials Science Forum　449-4　665-668　2004年1月
Microstructural influences on stress migration in electroplated Cu metallization 査読有り

A Sekiguchi, J Koike, K Maruyama

APPLIED PHYSICS LETTERS　83　(10)　1962-1964　2003年9月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.1609238 　

ISSN：0003-6951

詳細を見る詳細を閉じる

Stress migration in advanced Cu interconnects leads to device failure and to poor production throughput. In this work, microstructural effects on stress-migration resistance were investigated in two types of electroplated Cu metallization having a <111> texture and a random texture. Transmission electron microscopy showed incoherent twins in the <111> textured films whereas coherent twins in the random textured films. The incoherent twins were found to accompany stress-induced voids because of a weak bonding at twin interfaces. Unlike conventional Al interconnects, a strong <111> texture should be avoided to minimize stress-migration failure in Cu interconnects. (C) 2003 American Institute of Physics.
The activity of non-basal slip systems and dynamic recovery at room temperature in fine-grained AZ31B magnesium alloys 査読有り

J Koike, T Kobayashi, T Mukai, H Watanabe, M Suzuki, K Maruyama, K Higashi

ACTA MATERIALIA　51　(7)　2055-2065　2003年4月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/S1359-6454(03)00005-3 　

ISSN：1359-6454

詳細を見る詳細を閉じる

Fine-grained alloys of Mg-3Al-1Zn-0.2Mn in wt.% (AZ31B) were obtained by an equal-channel angular extrusion technique and subsequent annealing at elevated temperatures. Tensile tests were performed at room temperature at a strain rate of 1x10(-3) s(-1). The alloys exhibited an apparent steady-state deformation region and a large tensile elongation of 47%. The deformed microstructure at an elongation of 2% indicated substantial cross-slip to non-basal planes induced by plastic compatibility stress associated with grain boundaries. The non-basal segment of dislocations was found to consist of 40% of the total dislocation density at a yield anisotropy factor of only 1.1 instead of an expected value of 100 obtained from single-crystal experiments. The deformed microstructure at an elongation of 16% indicated recovered regions within twins as well as untwinned matrices. These results indicate that dynamic recovery can occur in Mg alloys at room temperature. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
Grain-boundary sliding in AZ31 magnesium alloys at room temperature to 523 K 査読有り

J Koike, R Ohyama, T Kobayashi, M Suzuki, K Maruyama

MATERIALS TRANSACTIONS　44　(4)　445-451　2003年4月
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/matertrans.44.445 　

ISSN：1345-9678

eISSN：1347-5320

詳細を見る詳細を閉じる

Rolled sheets of AZ31 Mg alloys were subjected to tensile testing at temperatures ranging from room temperature to 523 K. The occurrence of grain-boundary sliding (GBS) at room temperature was demonstrated by the displacement of scribed lines across grain boundaries of deformed samples. Surface relief of deformed samples was measured by use of a scanning laser microscope. GBS strain was calculated from the measured surface step height, and its temperature dependence was analyzed by a Dorn-type constitutive equation. GBS above 423 K was found to be pure GBS that was activated by resolved applied shear stress acting on grain boundaries. The activation energy for GBS was found to be 80 kJ/mol, which is in agreement with the activation energy for grain boundary diffusion. Meanwhile, GBS below 373 K was found to be slip-induced GBS, and its extent was found to be significantly greater than that expected from extrapolation of high-temperature values. The slip-induced GBS is considered to occur by plastic compatibility conditions in the presence of plastic strain anisotropy and by absorption and dissociation of lattice dislocations at grain boundaries.
Strengthening effect of Zn in heat resistant Mg-Y-Zn solid solution alloys 査読有り

M Suzuki, T Kimura, J Koike, K Maruyama

SCRIPTA MATERIALIA　48　(8)　997-1002　2003年4月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/S1359-6462(02)00590-0 　

ISSN：1359-6462

詳細を見る詳細を閉じる

The addition of zinc is effective in improving creep strength of Mg-Y solid solution alloys at temperatures 550-650 K because zinc suppresses the non-basal slip that operates predominantly at such temperatures. This suppression is caused by the formation of planar defects on the (0 0 0 1) plane and confinement of dislocations in the basal plane due to a decrease in stacking fault energy. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
Hall-Petch Parameters for tension and compression in cast Mg 査読有り

P. Anderson, C. H. Caceres, J. Koike

Mater. Sci. Forum　419-422　123-128　2003年
Effects of Zinc on creep bahavior and deformatin substructures of Mg-Y alloy 査読有り

M. Suzuki, T. Kimura, J. Koike, K. Maruyama

Mater. Sci. Forum　419-422　473-478　2003年
Anomalous activity of nonbasal dislocations in AZ31 Mg alloy at room temperature 査読有り

T. Kobayashi, J. Koike, T. Mukai, M. Suzuki, H. Watanabem, K. Maruyama, K. Higashi

Mater. Sci. Forum　419-422　231-236　2003年
Enhanced grain-boundary sliding at room temperature in AZ31 magnesium alloy 査読有り

R. Ohyama, J. Koike, T. Kobayashi, M. Suzuki, K. Maruyama

Mater. Sci. Forum　419-422　237-242　2003年
New deformation mechanisms in fine-grain Mg alloys 査読有り

J. Koike

Mater. Sci. Forum　419-422　189-194　2003年
AZ31マグネシウム合金における活動すべり系の粒径依存性査読有り

小林孝幸, 小池淳一, 吉田雄, 鎌土重春, 鈴木真由美, 丸山公一, 小島陽

日本金属学会誌　67　149-152　2003年

DOI： 10.2320/jinstmet1952.67.4_149 　
銅薄膜の室温再結晶における不均一ひずみの影響査読有り

和田真, 小池淳一, 丸山公一

日本金属学会誌　67　169-172　2003年

DOI： 10.2320/jinstmet1952.67.4_169 　
Texture development of AZ31 magnesium alloys during ECAE processing 査読有り

Y. Yoshida, L. Cisar, S. Kamado, J. Koike, Y. Kojima

Materials Science Forum　419-422　533-538　2003年
Magnesium research trend in Japan 査読有り

S. Kamado, J. .Koike, K. Kondoh, Y. Kawamura

Materials Science Forum　419-422　21-34　2003年
Newly develped heat resistant alloy by thixomolding 査読有り

T. Tsukeda, R. Uchida, M. Suzuki, J. Koike, K. Maruyama

Materials Science Forum　419-422　439-444　2003年
Creep behavior and deformation substructure of Mg-Y alloys containing dilute content of zinc 査読有り

M. Suzuki, T. Kimura, J. Koike, K. Maruyama

Materials Science Forum　426-432　593-598　2003年
Self-annealing process and its effects on heat-treated texture in electroplated Cu thin films 査読有り

M. Wada, J. Koike, K. Maruyama

Journal of Applied Physics　submitted　2003年
The correlation of adhesion strength with barrier structure in Cu metallization 査読有り

A. Sekiguchi, J. Koike, J. Ye, K. Maruyama

MRS Proc.　in press　2003年
Epitaxial growth of SrRuO3 thin film electrode on Si by pulsed laser deposition 査読有り

T Higuchi, YX Chen, J Koike, S Iwashita, M Ishida, T Shimoda

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS　41　(11B)　6867-6872　2002年11月
出版者・発行元：INST PURE APPLIED PHYSICS
DOI： 10.1143/JJAP.41.6867 　

ISSN：0021-4922

詳細を見る詳細を閉じる

Pseudocubic SrRuO3 (100) epitaxial thin films were fabricated on Si (100) with a SrO buffer layer by pulsed laser deposition (PLD). Reflection high-energy electron diffraction (RHEED) revealed that the SrO layer is epitaxially grown, on naturally oxidized Si substrates with an orientation relationship of SrO (110)/Si (100) and SrO <001>//Si <011>. Subsequent SrRuO3 deposition resulted in a (100) epitaxial thin film possessing good crystallinity with a full-width at half maximum (FWHM) of 1.9degrees in the SrRuO3 (200) rocking curve by X-ray diffraction (XRD). Based on the Gibbs free energy change in the reaction of silicon with alkaline earth metal oxides, deoxidization Of SiO2 on Si by Sr is thought to play an important role in the epitaxial growth of SrO. Cross-sectional observation for the optimized SrRuO3/SrO/Si sample using transmission electron microscopy (TEM) revealed that the thickness of the SrO layer is less than 2 nm and that the SrRuO3 electrode. forms an epitaxial thin film almost directly on Si.
Microstructure of epitaxial SrRuO3 filMS OD Si(001) substrates 査読有り

YX Chen, J Koike, T Higuchi, S Iwashita, M Ishida, Shimoda, I

PHILOSOPHICAL MAGAZINE B-PHYSICS OF CONDENSED MATTER STATISTICAL MECHANICS ELECTRONIC OPTICAL AND MAGNETIC PROPERTIES　82　(16)　1731-1748　2002年11月
出版者・発行元：TAYLOR & FRANCIS LTD
DOI： 10.1080/1364281021000050070 　

ISSN：0141-8637

詳細を見る詳細を閉じる

The microstructure of pulsed-laser-deposited SrRuO3 films on Si(001) with SrO buffer layers has been studied by means of high-resolution electron microscopy and energy-dispersive X-ray spectroscopy. It was found that good epitaxial growths of the SrO buffer layers and the subsequent SrRuO3 films were achieved on the Si(001) substrates. Multiple domains were formed in the SrRuO3 films with domain boundaries nearly perpendicular to the interface between the SrRuO3 films and the SrO buffer layers. A high density of planar defects, such as twins, stacking faults and antiphase boundaries, were formed along the (022) lattice plane of the SrRuO3 films. Lattice strains in the constituting layers were investigated by means of fast Fourier transformation of local regions in the high-resolution images. It was found that, close to the interface between the SrRuO3 films and the SrO buffer layers, both the layers were elastically strained in the opposite sense. The structure of coherent twin boundary in the SrRuO3 films was determined using a computer-aided high-resolution image simulation method. The comparison between the simulated and the experimental images indicated that the Sr-O plane constituted the twin boundary.
Effects of crystallographic texture on stress-migration resistance in copper thin films 査読有り

J Koike, M Wada, M Sanada, K Maruyama

APPLIED PHYSICS LETTERS　81　(6)　1017-1019　2002年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.1498495 　

ISSN：0003-6951

詳細を見る詳細を閉じる

The crystallographic texture of heat-treated Cu thin films and its effects on stress-migration resistance were studied as a function of film thickness within a range of 50-900 nm. All as-deposited films had (111) texture. After heat treatment at 723 K, texture transition from (111) to (100) was observed in films of thickness greater than 300 nm. The (111) texture films after heat treatment showed severe stress migration; in contrast, the (100) texture films showed no noticeable stress migration. The observed stress-migration resistance in the (100) texture films can be attributed to the absence of twins and to lower thermal stress as compared with the (111) texture films. (C) 2002 American Institute of Physics.
Formation of slit-like voids at trench corners of damascene Cu interconnects 査読有り

A Sekiguchi, J Koike, K Maruyama

MATERIALS TRANSACTIONS　43　(7)　1633-1637　2002年7月
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/matertrans.43.1633 　

ISSN：1345-9678

eISSN：1347-5320

詳細を見る詳細を閉じる

Stress voiding was investigated in damascene Cu lines embedded in Ta/TaN/SiO2/Si. Microstructure was observed before and after heat treatment at 723 K using a focused ion beam (FIB) technique. The distribution of thermal stress was calculated using a three-dimensional finite element method (FEM). FIB observation revealed that slit-like voids were formed at trench shoulders both before and after heat treatment. FEM calculation indicated that a large shear stress concentration occurred at the voided sites. The coincidence between the FIB observation and the FEM calculation suggests that the slit-like voids were formed by shear-mode delamination of Cu from the Ta/TaN barrier layer.
Fabrication of pseudocubic SrRuO3 (100) epitaxial thin films on Si by pulsed laser deposition 査読有り

T Higuchi, YX Chen, J Koike, S Iwashita, M Ishida, T Shimoda

JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS　41　(4B)　L481-L483　2002年4月
出版者・発行元：INST PURE APPLIED PHYSICS
DOI： 10.1143/JJAP.41.L481 　

ISSN：0021-4922

詳細を見る詳細を閉じる

Pseudocubic SrRuO3 (100) epitaxial thin films were successfully fabricated on Si (100) with a SrO buffer layer of 6mm thickness by pulsed laser deposition (PLD). Reflection high-energy electron diffraction (RHEED) revealed that the epitaxial growth of SrO occurred on naturally oxidized Si substrates, followed by the epitaxial growth of SrRuO3. X-ray diffraction (XRD) revealed high crystallinity with a full-width at half maximum (FWHM) of 1.9degrees in the SrRuO3 (200) rocking curve. XRD study of the in-plane orientation clarified a cube-on-cube epitaxy in which SrRuO3 [010] was rotated by 45degrees with respect to Si [010]. Deoxidization of SiO2 on Si by Sr is thought to play an important role in realizing the epitaxial growth of SrO.
Novel hexagonal structure of ultra-high strength magnesium-based alloys 査読有り

A Inoue, M Matsushita, Y Kawamura, K Amiya, K Hayashi, J Koike

MATERIALS TRANSACTIONS　43　(3)　580-584　2002年3月
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/matertrans.43.580 　

ISSN：1345-9678

eISSN：1347-5320

詳細を見る詳細を閉じる

A magnesium (Mg) solid solution with a novel long periodic hexagonal structure was formed for a Mg97Zn1Y2 (at%) alloy in a rod form prepared by extrusion of atomized powders at 573 K as well as in a melt-spun ribbon form. The novel structure of the rod alloy had an ABACAB-type six layered packing with lattice parameters of a = 0.322 nm and c = 3 x 0.521 nm, The Mg phase in the extruded rod alloy had fine grain sizes of 100 to 150 nm and included cubic Mg24Y5 particles with a size of about 10 nm at volume fractions below 10%. The density (p) was 1.84Mg/m(3). The tensile yield strength (sigma(y)) and elongation of the rod alloy were 6 10 MPa and 5%, respectively. and the specific strength defined by the ratio of sigma(y) to p was 330 MPa/(Mg/m(3)), being the highest among all metallic alloys, The sigma(y) is 2.7 to 8 times higher than those for conventional high-strength Mg-based alloys. The excellent mechanical properties are due to the combination of fine grain size. new long periodic hexagonal solid solution, homogeneous dispersion of fine Mg24Y5 particles inside the nano-grains and the absence of the second precipitates along the grain boundary. The new Mg-based alloy is promising for future uses in many fields.
A relationship between film texture and stress-voiding tendency in copper thin films 査読有り

J Koike, A Sekiguchi, M Wada, K Maruyama

STRESS-INDUCED PHENOMENA IN METALLIZATION　612　169-176　2002年
出版者・発行元：AMER INST PHYSICS
ISSN：0094-243X

詳細を見る詳細を閉じる

The origin of stress voiding in heat-treated Cu thin films was investigated in relation to microstructure. Voids were observed at the intersections of twins with grain boudaries or with other twins. Twin interfaces were accompanied by stress concentration due to the elastic anisotropy. Stress concentration was found to act as a driving force for stress voiding. Twin formation and associated void formation could be avoided by controlling the film texture. Texture transition from (111) to (100) was observed in heat-treated films with increasing the film thickness from 200 nm to 300 nm. The (100) oriented films did not show any voids or hillocks. The excellent stress-migration resistance in the (100) oriented films could be attributed to the absence of twins and by small thermal stresses.
Processing and characterization of hydroxyapatite coatings on titanium produced by magnetron sputtering 査読有り

TG Nieh, AF Jankowski, J Koike

JOURNAL OF MATERIALS RESEARCH　16　(11)　3238-3245　2001年11月
出版者・発行元：CAMBRIDGE UNIV PRESS
DOI： 10.1557/JMR.2001.0446 　

ISSN：0884-2914

eISSN：2044-5326

詳細を見る詳細を閉じる

Hydroxyapatite (HA) coatings with different thicknesses were produced on Ti and Si substrates using the radio frequency magnetron sputtering method. The mechanical properties, for example, modulus and hardness, of the coatings were measured using nanoindentation. The measured values of modulus and hardness were close to the upper limit of that reported for bulk HA, indicating a fully dense structure. Interfacial strengths between the HA coatings and substrates were also evaluated using a nanoscratch technique. The HA-Ti interface appeared to be stronger than the HA-Si interface. The microstructures of the HA coating and the HA-Ti interface were examined using high-resolution electron microscopy. Chemical compositions of the HA coating and the HA-Ti interface were also analyzed using x-ray energy dispersive spectrometer and electron energy loss spectroscopy. The results indicated that the strong HA-Ti bonding is associated with an outward diffusion of Ti into HA layer and concomitant formation of TiO2 at or near the interface.
Void formation by thermal stress concentration at twin interfaces in Cu thin films 査読有り

A Sekiguchi, J Koike, S Kamiya, M Saka, K Maruyama

APPLIED PHYSICS LETTERS　79　(9)　1264-1266　2001年8月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.1399021 　

ISSN：0003-6951

詳細を見る詳細を閉じる

A void formation mechanism was investigated in an electroplated copper thin film on Ta/SiO2/Si. Microstructural observation after thermal cycling indicated that void formation occurred at intersecting points or terminating corners of annealing twins. The calculated stress distribution was compared with experimental results of the void formation tendency. An excellent correlation was found between void formation sites and stress concentration sites. Electron diffraction analysis revealed that most twin interfaces in Cu thin films are incoherent {322} planes. The stress concentration drives diffusion along incoherent twin interfaces of {322} and leads to void formation at twin interfaces and corners. (C) 2001 American Institute of Physics.
Ti-6Al-2Sn-2Mo-2Zr-2Cr-Si合金の破壊特性に及ぼすミクロ組織の影響査読有り

新家光雄, 福永啓一, 戸野源三, 小池淳一, D. Eylon, 藤城四郎

鉄と鋼　87　(1)　55-62　2001年1月
出版者・発行元：None
DOI： 10.2355/tetsutohagane1955.87.1_55 　

ISSN：0021-1575
A large depression of the b transus temperature by mechanical deformation in two-phase Ti alloys 査読有り

J. Koike, Y. Shimoyama, K. Maruyama

Proc. of the 2nd Int. Symp. on Desiging, Processing and Properties of Advanced Eng. Mater.　256-258　2001年
A new class of stress-induced phase transformation and its effects on superplasticity in two-phase titanium alloys 査読有り

J. Koike, T. Okamura, Y. Fujinaga, K. Maruyama

Proc. of the 4th Pac. Rim Int. Conf. on Advanced Mater. and Processing　in print　2001年
Strength and ductility of Mg alloys 査読有り

J Koike

PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II　1179-1182　2001年
出版者・発行元：JAPAN INST METALS

詳細を見る詳細を閉じる

This paper reviews the strength and ductility of Mg alloys at room temperature. Compilation of various data indicated that tensile yield strength can be described by a single Hall-Petch equation as, sigma = 90 + 0.17/d(-1/2)+ Delta. Here, the stress and the grain size are given in MPa and in. The magnitude of the last term varies within a range of 0 to 120 MPa, depending on the crystallographic texture and aging conditions. The grain-size refinement predominates the strength above 300 MPa. As for the ductility, a good correlation was found between tensile elongation to failure and grain-boundary (GB) coverage of precipitates. The elongation increased with decreasing the GB coverage. Both the strength and the ductility can be improved synergistically by reducing the grain size and the GB precipitates.
Microstructural investigation of pulsed-laser-deposited SrRuO3 films on Si with SrO buffer layers 査読有り

Y. X. Chen, J. Koike, T. Higuchi, S. Iwashita, M. Ishida, T. Shimoda

Jpn. J. Appl. Phys.　40　L1305-L1307　2001年

DOI： 10.1143/JJAP.40.L1305 　
Effect of microstructure on fracture characteristics in Ti-6Al-2Sn-2Zr-2Mo-2Cr-Si 査読有り

M. Niinomi, K. Fukunaga, Gunawarman, G. Tono, J. Koike, D. Eylon, S. Fujishiro

Metall. Mater. Trans.　32A　2795-2804　2001年

DOI： 10.1007/s11661-001-1030-9 　
Strengthening mechanisms of creep resistant tempered martensitic steel 査読有り

K Maruyama, K Sawada, J Koike

ISIJ INTERNATIONAL　41　(6)　641-653　2001年
出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN
DOI： 10.2355/isijinternational.41.641 　

ISSN：0915-1559

詳細を見る詳細を閉じる

The creep deformation resistance and rupture life of high Cr ferritic steel with a tempered martensitic lath structure are critically reviewed on the basis of experimental data. Special attention is directed to the following three subjects: creep mechanism of the ferritic steel, its alloy design for further strengthening, and loss of its creep rupture strength after long-term use. The high Cr ferritic steel is characterized by its fine subgrain structure with a high density of free dislocations within the subgrains. The dislocation substructure is the most densely distributed obstacle to dislocation motion in the steel. Its recovery controls creep rate and rupture life at elevated temperatures. Improvement of creep strength of the steel requires a fine subgrain structure with a high density of free dislocations. A sufficient number of pinning particles (MX particles in subgrain interior and M23C6 particles on sub-boundaries) are necessary to cancel a large driving force for recovery due to the high dislocation density. Coarsening and agglomeration of the pinning particles have to be delayed by an appropriate alloy design of the steel. Creep rupture strength of the high Cr ferritic steel decreases quickly after long-term use. A significant improvement of creep rupture strength can be achieved if we can prevent the loss of rupture strength. In the steel tempered at high temperature, enhanced recovery of the subgrain structure along grain boundaries is the cause of the premature failure and the consequent loss of rupture strength. However, the scenario is not always applicable. Further studies are needed to solve this important problem of high Cr ferritic steel. MX particles are necessary to retain a fine subgrain structure and to achieve the excellent creep strength of the high Cr ferritic steel. Strengthening mechanism of the MX particles is another important problem left unsolved.
Novel hexagonal structure and ultrahigh-strength solid solution in the Mg-Zn-Y system 査読有り

A. Inoue, Y. Kawamura, M. Matsushita, K. Hayashi, J. Koike

J. Mater. Res.　16　1894-1900　2001年

DOI： 10.1557/JMR.2001.0260 　
A new class of stress-induced phase transformation and its effects on superplasticity in two-phase titanium alloys 査読有り

J. Koike, T. Okamura, Y. Fujinaga, K. Maruyama

Proc. the 4th Pac. Rim Conference　2047-2050　2001年
Development of rapidly solidified powder metallurgy magnesium alloys with excellent yield strength above 600 MPa 査読有り

Y. Kawamura, K. Hayashi, J. Koike, A. Inoue

Proc. the 4th Pac. RIM conference　1171-1174　2001年
Effects of initial microstructure on creep behavior of precipitation-hardened Mg-Y alloys at 530 K 査読有り

M. Suzuki, T. Kimura, H. Sato, J. Koike, K. Maruyama, H. Oikawa

Proc. the 4th Pac. RIM conf.　1163-1166　2001年
Stress-induced phase transformation during superplastic deformation in two-phase Ti-Al-Fe alloy 査読有り

J Koike, Y Shimoyama, Ohnuma, I, T Okamura, R Kainuma, K Ishida, K Maruyama

ACTA MATERIALIA　48　(9)　2059-2069　2000年5月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/S1359-6454(00)00049-5 　

ISSN：1359-6454

詳細を見る詳細を閉じる

Ti-5.5Al-1Fe alloys consisting of the h.c.p.-alpha phase and the b.c.c.-beta phase were investigated for microstructural changes during superplastic deformation at temperatures from 1050 to 1200 K. Observed changes occurred in two steps: (1) agglomeration of the beta phase to grain boundaries perpendicular to the tensile axis and (2) subsequent increase of the beta volume fraction. The beta volume fraction after failure was found to increase with increasing deformation temperature. The first step was considered to be induced by the gradient of traction force acting upon grain boundaries. The second step was considered to be induced by stress concentration at grain boundaries of the 2 phase where the beta phase was depleted by agglomeration to the perpendicular boundaries. The phase equilibrium under stressed condition was calculated by increasing the Gibbs energy of the alpha phase by 500 J/mol relative to that of the beta phase. An excellent quantitative agreement was found between calculated results and experimental results of the beta volume fraction and the Fe composition in each phase. The present work indicates that the phase transformation accompanied by diffusion can be induced by application of stress of the order of 100 MPa. This new type of stress-induced phase transformation can decrease the beta transus temperature by more than 100 K. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.
Effects of yttrium on creep behavior and deformation substructures of magnesium 査読有り

M. Suzuki, R. Inoue, M. Sugihara, H. Sato, J. Koike, K. Maruyama, H. Oikawa

Mater. Sci. Forum　350-351　151-156　2000年
Effects of the liquid phase on tensile elongation of Al-Bi alloys 査読有り

J. Koike, K. Miki, H. Takahashi, K. Maruyama

Mater. Sci. Eng. A　A285　158-164　2000年

DOI： 10.1016/S0921-5093(00)00641-9 　
Mechanical properties of rapidly solidified Mg-Zn alloys 査読有り

J. Koike, Y. Kawamura, K. Hayashi, M. Suzuki, K. Maruyama, A. Inoue

Mater. Sci. Forum　350-351　105-110　2000年
Structure and mechanical properties of rapidly solidified Mg-X alloys 査読有り

K. Hayashi, Y. Kawamura, J. Koike, K. Higashi, A. Inoue

Mater. Sci. Forum　350-351　117-122　2000年
High strength nanocrystalline Mg-Al-Ca alloys produced by rapidly solidified powder metallurgy processing 査読有り

Y. Kawamura, K. Hayashi, J. Koike, A. Kato, A. Inoue, T. Masumoto

Mater. Sci. Forum　350-351　111-116　2000年
熱サイクルによるSi基板上銅薄膜の塑性変形とキャビティ形成査読有り

A. Sekiguchi, J. Koike, K. Maruyama

日本金属学会誌　64　379-382　2000年

DOI： 10.2320/jinstmet1952.64.5_379 　
Mechanical properties and microstructure of heat-resistant Mg-Al-Ca alloys formed by thixomolding 査読有り

T Tsukeda, A Maehara, K Saito, M Suzuki, J Koike, K Maruyama, H Kubo

MAGNESIUM TECHNOLOGY 2000　395-402　2000年
出版者・発行元：MINERALS, METALS & MATERIALS SOC

詳細を見る詳細を閉じる

Thixomolding is a new process in which the metallic slurry is injected into a die cavity at semi-solid temperatures to form near net-shape products from the solid feed stock in one step. The relationship between the chemical composition and the mechanical properties of heat-resistant Mg-Al-Ca alloys formed by thixomolding was investigated. The effect of a variable such as barrel temperature was also studied. It was found that the addition of Ca is effective in improving the tensile strength and creep resistance of the alloys at elevated temperatures. The ductility is decreased with increasing Ca content. The microstructure of specimens was observed with SEM and TEM. It showed a fine structure consisting of granular primary a Mg solid solution and a network consisting of eutectic a and intermetallic compounds. The morphology of this network varies depending on Ca content.
Effects of alloying elements on the creep resistance of thixomolded Mg-Al-Ca-X (X=S, Zn, Mn, Ba, Sr) 査読有り

T. Tsukeda, R. Uchida, K. Saito, M. Suzuki, J. Koike, K. Maruyama, H. Kubo

Magnesium Alloys and Their Applications　47-52　2000年
Creep behavior and deformation substructures of thixomolded Mg-Al-Ca alloys 査読有り

M. Suzuki, J. Koike, K. Maruyama, T. Tsukeda, K. Saito, H. Kubo

Magnesium Alloys and Their Applications　699-704　2000年
Fatigue of bi-lamellar microstructures 査読有り

G. Schroeder, J. Arrecht, G. Lutjering, J. Koike, K. -D. Folkers, Ch. Liesner

Fatigue Behavior of Titanium Alloys (TMS)　31-36　1999年
Primary creep of Ti-6-22-22S alloy 査読有り

J . Koike, K. Maruyama

Mater. Sci. Eng. A　A263　155-159　1999年
Superplasticity Assisted by Stress-Induced Phase Transformation in Ti-5.5Al-1Fe Alloy 査読有り

J. Koike, Y. Shimoyama, T. Okamura, K. Maruyama

Materials Science Forum　304-306　183-188　1999年
Thermal cycling fatigue and deformation mechanism in aluminum alloy thin films on silicon 査読有り

J Koike, S Utsunomiya, Y Shimoyama, K Maruyama, H Oikawa

JOURNAL OF MATERIALS RESEARCH　13　(11)　3256-3264　1998年11月
出版者・発行元：MATERIALS RESEARCH SOCIETY
DOI： 10.1557/JMR.1998.0442 　

ISSN：0884-2914

詳細を見る詳細を閉じる

Thermal cycling was performed between room temperature and 723 K in a sputter deposited thin film of Al-l mol % Si alloy on a silicon substrate. After given numbers of cycling, residual stress was determined at room temperature by measuring the film curvature using a laser deflection apparatus. Residual stress was found to increase with increasing the cycle number up to the 4th cycle, followed by a continuous decrease by further cycling. Based on the microstructure observation, the initial increase of residual stress was caused by the increase of lattice dislocations and their tangling. The following decrease of residual stress was caused by crack formation and delamination. Stress relaxation experiments were also performed during isothermal annealing at various temperatures. Analysis of the relaxation curves indicates three temperature regions representing different deformation mechanisms. The boundaries between the neighboring regions were found to agree with the boundaries in a deformation mechanism map calculated for an Al thin film. Based on the obtained knowledge of the deformation mechanisms, the origin of the microstructure changes and the structural failure by thermal cycling are discussed.
Characterization of superplasticity in Ti-5.5Al-1Fe alloys 査読有り

J Koike, Y Shimoyama, H Fujii, K Maruyama

SCRIPTA MATERIALIA　39　(8)　1009-1014　1998年9月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/S1359-6462(98)00286-3 　

ISSN：1359-6462
Effects of the liquid phase on the high-temperature tensile ductility: from embrittlement to superplasticity 査読有り

J Koike, K Miki, K Maruyama, H Oikawa

PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES　78　(3)　599-614　1998年9月
出版者・発行元：TAYLOR & FRANCIS LTD
DOI： 10.1080/014186198253408 　

ISSN：0141-8610

詳細を見る詳細を閉じる

Inclusions of liquid phase are generally considered to cause liquid-metal embrittlement. On the other hand, there have been some reports implying the enhancement of tensile elongation by liquid inclusions. In this paper, the possibility of elongation enhancement by liquid and its underlying mechanism were investigated in a model binary system of Al-Bi and a composite of(Al-Mg)-Si3N4. Clear evidence of elongation enhancement was observed in the Al-Bi alloy. Liquid inclusions of Bi were found to assist stress accommodation processes and to delay cavitation failure. In the (Al-Mg)-Si3N4 composite, a close correlation was found between the incipient melting temperature and an optimum temperature for high-strain-rate superplasticity. The liquid phase was observed along grain boundaries and interfaces of the composite, suggesting a similar stress accommodation process to that of the Al-Bi alloy. The interface microstructure was also studied by high-resolution transmission electron microscopy to understand the detailed mechanism of high-strain-rate superplasticity.
The Nb-U (niobium-uranium) system 査読有り

J Koike, ME Kassner, RE Tate, RS Rosen

JOURNAL OF PHASE EQUILIBRIA　19　(3)　253-260　1998年6月
出版者・発行元：ASM INTERNATIONAL
ISSN：1054-9714
Thermal cycling fatigue in aluminum alloy thin films on silicon 査読有り

J. Koike, S. Utsunomiya, Y. Shimoyama, K. Maruyama

MRS Proc., vol. 505 (Thin Films - Stress and Mechanical Properties　505　319-324　1998年
Enhancement of tensile elongation in polycrystalline aluminum containing liquid bismuth 査読有り

J. Koike, K. Miki, K. Maruyama, T. Ohide, H. Oikawa

Superplastic Materials　177-184　1998年
Effects of surface oxide layer on thermal cycling in aluminum alloy thin films deposited on silicon substrates 査読有り

S Utsunomiya, J Koike, K Maruyama

STRESS INDUCED PHENOMENA IN METALLIZATION - FOURTH INTERNATIONAL WORKSHOP　(418)　283-288　1998年
出版者・発行元：AMER INST PHYSICS
ISSN：0094-243X

詳細を見る詳細を閉じる

An aluminum alloy thin film of 500nm thickness was sputter deposited on the silicon substrate using an Al-1mol%Si target. Then some specimens were anodized and a surface oxide layer of 33nm thickness was grown on the film surface (an anodized film). The specimens were subjected to thermal cycling between room temperature and 723K, after annealing at 823K for 60min. An anodized film showed a high resistance against thermal cycle fatigue, in comparison to the thin film without an anodic oxide layer (the normal film). In-situ stress measurements during thermal cycling showed that stress was kept at a lower level in the anodized film than in the normal film. TEM observations revealed that a fine grain size of as-deposited state was remained in the anodized film, while a substantial grain growth occurred in the normal film. It was suggested that the fine grain size in the anodized film caused a fast stress relaxation by grain boundary diffusion creep at high temperature, that leads to the low stress level and high resistance against thermal cycling fatigue in the anodized film.
Effects of grain boundary amorphous phase on high-temperature ductility in alumina polycrystals 査読有り

J Koike, H Oikawa, S Wakiya, T Takeda, K Maruyama

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　234　529-532　1997年8月
出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE
DOI： 10.1016/S0921-5093(97)00286-4 　

ISSN：0921-5093

詳細を見る詳細を閉じる

Two types of polycrystalline alumina were prepared by centrifugal compaction; MgO-doped alumina sintered in air and pure alumina HIPed in argon atmosphere with carbon susceptor. Both MgO-doped and HIP alumina had amorphous grain boundaries that were segregated, respectively by Mg and by C and S. The amorphous phase was found to melt near 1650 K, as evidenced by an endothermic peak in differential scanning calorimeter data. Melting of the grain boundary phase resulted in a ductile-to-brittle transition during the compressive deformation of the HIP alumina. In contrast, the MgO-doped alumina showed a ductile behavior up to the highest test temperature of 1773 K. The difference in ductility between two alumina specimens may be related to charge compensation, localization of bonding electrons in the grain boundary phase, and the spatial distribution of the grain boundary phase. (C) 1997 Elsevier Science S.A.
Influence of liquid-phase inclusion on high-temperature deformation behavior in Al-Bi alloys 査読有り

J Koike, K Miki, K Maruyama, H Oikawa

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　234　525-528　1997年8月
出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE
ISSN：0921-5093

詳細を見る詳細を閉じる

Tensile properties of an Al-3.4mass% Bi alloy up to 700 K were studied to understand the effects of the liquid Bi phase. Strain-rate sensitivity near the melting point of Bi was found to take values in a range of 0.17-0.31. Elongation showed a maximum value slightly above the melting temperature, indicating that the liquid phase could enhance tensile elongation in the AI-Bi alloy. Above the melting temperature, the dislocation density was found to decrease and the increment of the cavity volume fraction with strain slowed down in comparison to the results below the melting temperature. The increase of the tensile elongation was attributed to an efficient stress accommodation mechanism provided by the liquid phase. (C) 1997 Elsevier Science S.A.
Examination of deformation mechanism maps in 2.25Cr-1Mo steel by creep tests at strain rates of 10(-11) to 10(-6) s(-1) 査読有り

K Maruyama, K Sawada, J Koike, H Sato, K Yagi

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　224　(1-2)　166-172　1997年3月
出版者・発行元：ELSEVIER SCIENCE SA
ISSN：0921-5093

詳細を見る詳細を閉じる

The deformation mechanism map of 2.25Cr-1Mo steel was examined by creep data obtained over a wide range of creep rates down to 10(-11) s(-1). The stress dependence of minimum creep rates of the steel is similar to that of particle strengthened materials: low, high, and low stress exponent, respectively, in high (H), intermediate (I), and low (L) stress regions. The stress exponent and activation energy for creep rate suggest dislocation creep controlled by lattice diffusion as the deformation mechanism in regions I and L, including service conditions of the steel. Transition to diffusion creep occurs at a lower creep rate than what is expected in the deformation mechanism maps. Region H appears above athermal yield stress. During loading in this region, athermal plastic deformation takes place by dislocation glide mechanism, and then dislocation creep starts. The dislocation creep in region H is different from the one in regions I and L due to the plastic deformation during loading. A modified creep mechanism map of 2.25Cr-1Mo steel is proposed on the basis of the experimental results. (C) 1997 Elsevier Science S.A.
High Temperature Deformation Characteristics of Sintered Alumina Having Amorphous Grain Boundaries 査読有り

J. Koike, K. Maruyama, H. Oikawa

Mater. Sci. Forum　233/234　351-358　1997年
Microstructure and superplasticity in Al-Mg alloy composites reinforced with silicon nitride particles 査読有り

J. Koike

Materials Science Forum　243-245　277-285　1997年
Improvement of omega method for creep life prediction 査読有り

K Maruyama, Nonaka, I, K Sawada, H Sato, J Koike, H Umaki

ISIJ INTERNATIONAL　37　(4)　419-423　1997年
出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN
DOI： 10.2355/isijinternational.37.419 　

ISSN：0915-1559

詳細を見る詳細を閉じる

Omega method has been proposed for predicting rupture life from creep strain epsilon-time t data. The method is based on a linear relation between logarithm of creep rate epsilon and strain, namely a creep curve without the primary and secondary creep stages. Such a linear relation, however, seldom holds in real creep data. In this paper, the original equation is modified to the following form: epsilon = epsilon(0)+Omega/1{In(1+zeta t)-In(1-eta t)} where epsilon(0), Omega, zeta and eta are parameters characterizing a creep curve. The first and second terms in the parentheses describe primary creep and tertiary creep, respectively. The equation is applied to ferritic steels. The four parameters of the equation can uniquely be determined for a creep curve with a curved In be relation. The equation can well reproduce creep curves with a prominent primary creep stage. Because of the high reproducibility, the modified equation can predict rupture life with higher accuracy at an earlier stage of creep than the original equation.
Mechanical properties and microstructure of centrifugally compacted alumina and hot-isostatically-pressed alumina 査読有り

J Koike, S Tashima, S Wakiya, K Maruyama, H Oikawa

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　220　(1-2)　26-34　1996年12月
出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE
DOI： 10.1016/S0921-5093(96)10439-1 　

ISSN：0921-5093

詳細を見る詳細を閉じる

High purity alumina powder was compacted under a high centrifugal force. Mechanical properties of the sintered body were studied by the three-point bending test at room temperature and by the compressive test at elevated temperatures. Comparison was made with hot-isostatically-pressed (HIP) alumina. The room-temperature flexural strength of the centrifugally compacted (CC) alumina was found to be 1330 MPa compared with 585 MPa of the HIP alumina. The difference in the room-temperature strength was attributed to the presence of the amorphous phase along the grain boundaries of the HIP alumina caused by the segregation of carbon and sulfur during HIP. A large ductility was observed above 1473 K in the CC alumina and above 1573 K in the HIP alumina. High-temperature ductility was lost in the HIP alumina at 1773 K where the amorphous grain-boundary phase was considered to be melted.
High temperature strength of alpha Ti-Al alloys with a locally ordered structure 査読有り

J Koike, K Egashira, K Maruyama, H Oikawa

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING　213　(1-2)　98-102　1996年8月
出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE
DOI： 10.1016/0921-5093(96)10227-6 　

ISSN：0921-5093

詳細を見る詳細を閉じる

Tensile tests were performed in Ti-(7 similar to 13)mol.%Al alloys at 1100 K. Stress-strain curves showed a large region of constant stress deformation. The results were analyzed by a Dorn type creep equation. The strain rate and the steady-state stress showed anomalous strength of the examined alloys in comparison with the previously reported Ti-(1 similar to 5)mol.%Al alloys (H. Oikawa and T. Oomori, Mater. Sci. Eng., A104 (1988) 125). Both X-ray diffraction and transmission electron microscopy indicated the appearance of additional diffraction intensities that may owing to the formation of short range ordered (SRO) clusters. The anomalous creep strength observed in the present work seems to be caused by the retardation of dislocation glide by the SRO clusters.
単結晶Siの直接窒化によるSi3N4の形成過程査読有り

新見彰夫, 小池淳一, 木村彰一, 丸山公一, 及川洪

J. Ceramic Soc. Jpn.　104　(7)　662-667　1996年7月

DOI： 10.2109/jcersj.104.662
Formation of Si3N4 during the Direct Nitridation of Si Single Crystal 査読有り

A. Shinmi, J. Koike, S. Kimura, K. Maruyama, H. Oikawa

J. Ceramic Soc. Jpn., Int. Edition　104　(7)　641-646　1996年7月

DOI： 10.2109/jcersj.104.662
Structural and residual stress changes in Mo/a-Si multilayer thin films with annealing 査読有り

ME Kassner, FJ Weber, J Koike, RS Rosen

JOURNAL OF MATERIALS SCIENCE　31　(9)　2291-2299　1996年5月
出版者・発行元：SPRINGER
DOI： 10.1007/BF01152937 　

ISSN：0022-2461

eISSN：1573-4803

詳細を見る詳細を閉じる

The thermal and mechanical stability of molybdenum and amorphous silicon (Mo/a-Si) optical multilayers (3 and 4 nm nominal thickness of Mo and Si) at 316 degrees C were studied by annealing experiments. Growth of amorphous Mo-Si interlayers with a stoichiometry of 1:2 was observed at the Mo/a-Si interfaces. In addition, residual stresses significantly changed in the crystalline Mo and amorphous Si layers with annealing. High resolution electron microscopy, selected area electron diffraction, and X-ray diffraction of the crystalline Mo revealed that tensile stresses increased from 2 to about 10 GPa in the lateral direction (parallel to the interface plane). The compressive strains that developed in the vertical direction (perpendicular to the interface plane) are consistent with Poisson's ratio. Laser deflectometer measurements of thicker (0.1 mu m) amorphous silicon layers may indicate compressive-stress relaxation in the amorphous silicon with annealing, consistent with other investigations. Overall, the residual stress in a 40-bilayer film changes from about -0.5 to about +1.5 GPa. Structural transformation after relatively short annealing times at the interfaces in the thin amorphous Mo-Si interlayers may rationalize increased tensile strains in the Mo layers.
Anomalous high temperature strengthening in concentrated alpha titanium-aluminum alloys 査読有り

J Koike, H Oikawa

SCRIPTA MATERIALIA　34　(5)　797-801　1996年3月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/1359-6462(95)00574-9 　

ISSN：1359-6462
Mechanism of nitridation of silicon powder in a fluidized-bed reactor 査読有り

J Koike, S Kimura

JOURNAL OF THE AMERICAN CERAMIC SOCIETY　79　(2)　365-370　1996年2月
出版者・発行元：AMER CERAMIC SOC
DOI： 10.1111/j.1151-2916.1996.tb08130.x 　

ISSN：0002-7820

詳細を見る詳細を閉じる

Direct nitridation of 400 mu m average-sized silicon granules, composed of 2 mu m average-sized particles, was carried out in a fluidized-bed reactor, Nitridation progress was studied by transmission electron microscopy (TEM). TEM photomicrographs suggested that the formation of surface nitride layers on individual silicon particles and the subsequent spallation of these layers were the dominant process of the direct nitridation of silicon, The spallation was modeled based on a simple crack theory, and the critical thickness of nitride layers leading to spallation was estimated to be 57 nm, This agreed reasonably well with the experimentally observed values of 20-100 nm.
Influence of composition on creep of alpha-two Ti3Al polycrystals 査読有り

K. Maruyama, J. Koike, H. Oikawa

Proc. of the 8th World Conference on Titanium　348-355　1996年
High temperature deformation characteristics of sintered alumina having amorphous grain boundaries 査読有り

J. Koike, S. Tashima, S. Wakiya, K. Maruyama, O. Oikawa

Materials Science and Engineering A　A220　26-34　1996年
IN-SITU OBSERVATION OF PARTIAL MELTING IN SUPERPLASTIC ALUMINUM-ALLOY COMPOSITES AT HIGH-TEMPERATURES 査読有り

J KOIKE, M MABUCHI, K HIGASHI

ACTA METALLURGICA ET MATERIALIA　43　(1)　199-206　1995年1月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/0956-7151(95)90275-9 　

ISSN：0956-7151

詳細を見る詳細を閉じる

The possibility of partial melting and its relations to the superplasticity at high strain rates were studied with transmission electron microscopy and differential scanning calorimetry in Al-Cu-Mg (2124), Al-Mg (5052), and Al-Mg-Si (6061) alloys reinforced with Si3N4 particles. Calorimetry measurements of all three composites showed a sharp endothermic peak at an optimum superplastic temperature. At the same temperature, transmission electron microscopy showed the melting of grain boundaries and interfaces, suggesting direct correlations between partial melting and the superplasticity. Solute segregation was also observed at boundaries and interfaces, and was discussed as causes for partial melting.
PARTIAL MELTING AND SEGREGATION BEHAVIOR IN A SUPERPLASTIC SI3N4/AL-MG ALLOY COMPOSITE 査読有り

J KOIKE, M MABUCHI, K HIGASHI

JOURNAL OF MATERIALS RESEARCH　10　(1)　133-138　1995年1月
出版者・発行元：MATERIALS RESEARCH SOCIETY
DOI： 10.1557/JMR.1995.0133 　

ISSN：0884-2914

詳細を見る詳細を閉じる

Al-Mg alloy (5052) composite reinforced with Si3N4 particulates was investigated by transmission electron microscopy and electron energy loss spectroscopy. Partial melting was observed at matrix/reinforcement interfaces and matrix grain boundaries at a temperature near an optimum superplastic temperature. Segregation of solute elements (Mg and Si) was observed at the interfaces and grain boundaries. Both partial melting and solute segregation were found to depend on grain boundaries. The obtained results were explained by a decrease of the solidus temperature due to segregation whose extent depends on the type of the grain boundary structure.
DIMENSIONAL CHANGES IN HIGHLY ORIENTED PYROLYTIC-GRAPHITE DUE TO ELECTRON-IRRADIATION 査読有り

J KOIKE, DF PEDRAZA

JOURNAL OF MATERIALS RESEARCH　9　(7)　1899-1907　1994年7月
出版者・発行元：MATERIALS RESEARCH SOCIETY
DOI： 10.1557/JMR.1994.1899 　

ISSN：0884-2914

詳細を見る詳細を閉じる

One of the main problems found in the nuclear applications of graphite is its dimensional instability under irradiation, involving both swelling and shape changes. In order to understand better the mechanisms that give rise to these changes, highly oriented pyrolytic graphite was irradiated with 300 keV electrons at temperatures between 25 and 657-degrees-C in a transmission electron microscope (TEM). Microscopic dimensional changes and structural disordering were studied in directions parallel and perpendicular to the graphite basal plane. Changes in the specimen length were investigated by measuring the distance between two markers on the specimen surface in TEM images. Changes in the lattice parameter and the crystalline structure were studied by a TEM diffraction technique. In agreement with reported results, large increases in the specimen length and the lattice parameter were observed along the c-axis direction, whereas a relatively small decrease was observed along the a-axis. In irradiation studies conducted at room temperature, it was found that the dimensional change saturates at high dose, at an elongation along the c-axis direction of about 300%. High resolution microscopy revealed that the microstructure had become nanocrystalline. Electron energy loss spectroscopy results showed that the volume change was recovered at this stage. These observations are discussed in terms of point defect evolution and its effects on the microstructure of irradiated graphite.
DIMENSIONAL CHANGES IN GRADE H-451 NUCLEAR GRAPHITE DUE TO ELECTRON-IRRADIATION 査読有り

DF PEDRAZA, J KOIKE

CARBON　32　(4)　727-734　1994年
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/0008-6223(94)90095-7 　

ISSN：0008-6223

詳細を見る詳細を閉じる

Porosity plays a very important role in the overall dimensional changes induced by irradiation in many graphitic materials. In the present study, a nuclear grade isotropic graphite, H-451, was irradiated in situ in the electron microscope in regions bordering existing pores. Selected area diffraction patterns of different regions of this material showed that graphite grade H-451 is a well-graphitized, single-phase material whose structure is essentially identical to that of highly oriented pyrolytic graphite (HOPG). Therefore, structural changes in the individual crystallites must be the same as found in HOPG in our previous study. Crystallites having either of the two principal orientations parallel to the direction of the electron beam, viz., the c-crystallographic axis direction parallel or normal to the beam, could easily be found in specimens thinned to electron transparency. Both pore opening and closure were detected during irradiation depending upon the crystalline orientation around the pore. With increasing electron dose, elongated pores bound by crystallites with their c axis normal to the pore surface closed, while pores bound by crystallites with their basal plane in the plane of the pore at the observation surface opened up. These effects are consistent with the dimensional changes observed in HOPG. The present results are compared with the macroscopic changes observed under reactor irradiation.
Processing and development of superplastic metal matrix composites 査読有り

M. Mabuchi, J. Koike, H. Iwasaki, K. Higashi, T. G. Langdon

Materials Science Forum　170-172　503-512　1994年
ELASTIC INSTABILITY OF CRYSTALS CAUSED BY STATIC ATOM DISPLACEMENT - A MECHANISM FOR SOLID-STATE AMORPHIZATION 査読有り

J KOIKE

PHYSICAL REVIEW B　47　(13)　7700-7704　1993年4月
出版者・発行元：AMERICAN PHYSICAL SOC
DOI： 10.1103/PhysRevB.47.7700 　

ISSN：0163-1829

詳細を見る詳細を閉じる

During the solid-state amorphization process, there have been a number of observations showing a large lattice dilatation and softening of shear elastic constants. Based on these reports, the amorphization mechanism was modeled by introducing static displacement of atoms that caused lattice strain. The calculation indicated that a crystalline structure became unstable at a critical strain value. Qualitative agreement was obtained between the calculated and experimental values of the changes in the shear elastic constant and the lattice parameter at the instability point.
Tensile behavior of cold-rolled NiTi having an amorphous-crystalline composite microstructure 査読有り

J. Koike, H. W. Sizek

NATO advanced Study Institute Series　E233　323-328　1993年
Structural change of graphite during electron irradiation 査読有り

J. Koike, D. F. Pedraza

Materials Research Society Symposium Proceedings　279　67-72　1993年
STRUCTURAL-CHANGES INDUCED BY ELECTRON-IRRADIATION IN GRAPHITE 査読有り

J KOIKE, DF PEDRAZA

INTERNATIONAL CONFERENCE ON BEAM PROCESSING OF ADVANCED MATERIALS　519-536　1993年
出版者・発行元：MINERALS, METALS & MATERIALS SOC
Kinetics of Interlayer Growth and Changes in Residual Elastic Strain During Annealing of Mo/Si Multilayers. 査読有り

R. S. Rosen, D. G. Stearns, M. E. Kassner, J. Koike, Y. Cheng, S. P. Vernon

Journal of Applied Physics　1993年
DISPLACEMENT THRESHOLD ENERGY FOR TYPE-IIA DIAMOND 査読有り

J KOIKE, DM PARKIN, TE MITCHELL

APPLIED PHYSICS LETTERS　60　(12)　1450-1452　1992年3月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.107267 　

ISSN：0003-6951

詳細を見る詳細を閉じる

A type IIa natural diamond was irradiated at room temperature with energetic electrons. The threshold energy for displacement of atoms from their lattice sites was determined for three principal crystallographic directions by observing the formation of defect clusters during irradiation in a transmission electron microscope. The displacement-threshold energies were found to be 37.5 +/- 1.2 eV for the electron incident in the [100] direction, 45.0 +/- 1.3 eV in the [111] direction, and 47.6 +/- 1.3 eV in the [110] direction.
FORMATION OF DEFECT CLUSTERS IN ELECTRON-IRRADIATED DIAMOND AT 16-K AND 87-K 査読有り

J KOIKE, TE MITCHELL, DM PARKIN

APPLIED PHYSICS LETTERS　59　(20)　2515-2517　1991年11月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.105938 　

ISSN：0003-6951

詳細を見る詳細を閉じる

A type IIa natural diamond was irradiated with 300 kV electrons at 16 and 87 K. Transmission electron microscopy and electron energy-loss spectroscopy were employed to investigate the phase stability of diamond under electron irradiation. At both temperatures, the diamond structure was found to be stable, and the formation of defect clusters was observed. The present results in comparison to previous work on ion implantation indicate that displacement cascade damage is a prerequisite for irradiation-induced phase transformation from diamond to amorphous r-arbon or graphite. The temperature dependence of the cluster size suggests that interstitials are thermally mobile above 50 K.
CORRELATION BETWEEN THE ELASTIC SHEAR INSTABILITY MECHANISM AND EMPIRICAL CRITERIA FOR IRRADIATION-INDUCED AMORPHIZATION 査読有り

J KOIKE, PR OKAMOTO, LE REHN, M MESHII

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS　59　471-474　1991年7月
出版者・発行元：ELSEVIER SCIENCE BV
ISSN：0168-583X

詳細を見る詳細を閉じる

In an attempt to correlate the shear instability mechanism with empirical criteria for irradiation-induced amorphization, shear moduli of an A3B-type fcc crystal were calculated as a function of the chemical long range order parameter S using a Morse potential. The shear moduli were found to decrease with decreasing S. When the depth and the curvature of the A-B potential were changed while keeping the A-A and B-B potentials constant, the magnitude of the decrease in shear moduli is greater for deeper and narrower A-B potentials. The present results indicate that a shear instability should occur more readily in compounds with larger ordering energy and larger elastic moduli. These results agree with the reported empirical criteria for irradiation-induced amorphization, therefore providing further support for the shear instability mechanism for solid-state amorphization.
NUCLEATION AND GROWTH OF A BCC FE PHASE DEPOSITED ON A SINGLE-CRYSTAL (001) CU FILM 査読有り

J KOIKE

SCRIPTA METALLURGICA ET MATERIALIA　25　(3)　663-668　1991年3月
出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
DOI： 10.1016/0956-716X(91)90111-D 　

ISSN：0956-716X
Amorphous phase formation in NiTi during cold rolling 査読有り

J. Koike, D. M. Parkin, M. Nastasi

Materials Research Society Symposium Proceedings　186　161-167　1991年
Microstructural evolution of Fe grown on a (001) Cu film and its implication to the leastic anomaly in metallic superlattices 査読有り

J. Koike, M. Nastasi

Materials Research Society Symposium Proceedings　202　13-18　1991年
THE ROLE OF SHEAR INSTABILITY IN AMORPHIZATION OF COLD-ROLLED NITI 査読有り

J KOIKE, DM PARKIN, M NASTASI

PHILOSOPHICAL MAGAZINE LETTERS　62　(4)　257-264　1990年10月
出版者・発行元：TAYLOR & FRANCIS LTD
DOI： 10.1080/09500839008215132 　

ISSN：0950-0839
AMORPHIZATIONIN ZR3AI IRRADIATED WITH 1-MEVE- AND KR+ 査読有り

J KOIKE, PR OKAMOTO, LE REHN, M MESHII

METALLURGICAL TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE　21　(7)　1799-1808　1990年7月
出版者・発行元：MINERALS METALS MATERIALS SOC
DOI： 10.1007/BF02647225 　

ISSN：0360-2133
CRYSTAL-TO-AMORPHOUS TRANSFORMATION OF NITI INDUCED BY COLD-ROLLING 査読有り

J KOIKE, DM PARKIN, M NASTASI

JOURNAL OF MATERIALS RESEARCH　5　(7)　1414-1418　1990年7月
出版者・発行元：CAMBRIDGE UNIV PRESS
DOI： 10.1557/JMR.1990.1414 　

ISSN：0884-2914

eISSN：2044-5326
Irradiation-induced amorphization and elastic shear instability in intermetallic compounds 査読有り

J. Koike, P. R. Okamoto, L. E. Rehn, R. Bhadra, M. Grimsditch, M. Meshii

materials research society symposium proceedings　157　777-782　1990年
AMORPHIZATION OF GE/AL OR SI/AL BILAYER SPECIMENS INDUCED BY 1 MEV ELECTRON-IRRADIATION AT 10-K 査読有り

XW LIN, J KOIKE, DN SEIDMAN, PR OKAMOTO

PHILOSOPHICAL MAGAZINE LETTERS　60　(5)　233-240　1989年11月
出版者・発行元：TAYLOR & FRANCIS LTD
DOI： 10.1080/09500838908206463 　

ISSN：0950-0839
THE DOSE, TEMPERATURE, AND PROJECTILE-MASS DEPENDENCE FOR IRRADIATION-INDUCED AMORPHIZATION OF CUTI 査読有り

J KOIKE, PR OKAMOTO, LE REHN, M MESHII

JOURNAL OF MATERIALS RESEARCH　4　(5)　1143-1150　1989年9月
出版者・発行元：MATERIALS RESEARCH SOCIETY
DOI： 10.1557/JMR.1989.1143 　

ISSN：0884-2914
The effect of simultaneous electron and Kr+ irradiation on amorphization of CuTi 査読有り

J. Koike, P. R. Okamoto, L. E. Rehn, M. Meshii

Materials Research Society Symposium Proceedings　128　339-344　1989年
Amorphization of Zr3Al by hydrogenation and subsequent electron irradiation 査読有り

W. J. Meng, J. Koike, P.R. Okamoto, L.E.Rehn

Materials Research Society Symposium Proceedings　128　345-350　1989年
EFFECT OF PROJECTILE MASS ON AMORPHIZATION OF CUTI 査読有り

J KOIKE, PR OKAMOTO, M MESHII

JOURNAL OF NON-CRYSTALLINE SOLIDS　106　(1-3)　230-235　1988年12月
出版者・発行元：ELSEVIER SCIENCE BV
DOI： 10.1016/0022-3093(88)90265-7 　

ISSN：0022-3093
ELECTRON-IRRADIATION INDUCED AMORPHIZATION IN YBA2CU3O7 AND GDBA2CU3O7 SUPERCONDUCTORS 査読有り

M NASTASI, DM PARKIN, TG ZOCCO, J KOIKE, PR OKAMOTO

APPLIED PHYSICS LETTERS　53　(14)　1326-1328　1988年10月
出版者・発行元：AMER INST PHYSICS
DOI： 10.1063/1.100451 　

ISSN：0003-6951
The projectile mass dependence of the amorphization process and the critical temperature in the ion irradiated CuTi 査読有り

J. Koike, P. R. Okamoto, M. Meshii

Materials Research Society Symposium Proceedings　100　57-62　1988年
Temperature dependence of amorphization above 10K in the CuTi intermetallic compound under electron irradiation 査読有り

J. Koike, D. E. Luzzi, M. Meshii, P.R. Okamoto

Materials Research Society Symposium Proceedings　74　425-430　1987年
MASSIVE AND MARTENSITE TRANSFORMATIONS IN SN-CD ALLOYS 査読有り

J KOIKE, Y KOYAMA, O NITTONO

TRANSACTIONS OF THE JAPAN INSTITUTE OF METALS　27　(4)　254-259　1986年4月
出版者・発行元：JAPAN INST METALS
DOI： 10.2320/matertrans1960.27.254 　

ISSN：0021-4434

︎全件表示 ︎最初の5件までを表示

MISC 1

配線信頼性における界面密着性の役割

小池淳一, 貝沼亮介, 関口貴子, 飯島純, 根石浩司

表面科学　28　(2)　67-71　2007年2月

DOI： 10.1380/jsssj.28.67

講演・口頭発表等 38

Possibility of Cu-Mn alloy for TFT gate electrode 国際会議

International Display Workshop 2007　2007年12月5日
Deformaton and fracture mechanisms of Mg alloys 国際会議

Asian Forum on Light Metals and Exhibition　2007年12月3日
Possibility and problems of self-forming barrier process for advanced LSI metallization 国際会議

J. Koike, J. Iijima, K. Neishi

Advanced Metallization Conference　2007年10月9日
Role of twinning on deformation mechanisms of Mg alloys 国際会議

2nd Asian Syposium on Magnesium Alloys　2007年10月1日

詳細を見る詳細を閉じる

J. Koike
Role of twinning on deformation mechanisms of Mg alloys 国際会議

J. Koike, D. Ando, Y. Sato, T. Miyamura

Workshop on advanced magnesium alloys and their applications　2007年8月1日
Self-forming barrier process as a key technology for future technoogy node 国際会議

M. Haneda, J. Iijima, M. Wada, K. Neishi

Materials for Advanced Metallization　2007年3月4日
Impact of Mg alloys for structural application 国際会議

International Symposium on Magnesium Technology in the Global Age　2006年10月1日
Cu合金配線を用いた45nm世代のバリア層自己形成プロセス

電気化学会半導体・集積回路技術第７０回シンポジウム　2006年7月6日
多層配線におけるバリア層の新展開

Semi Forum Japan 2006　2006年6月13日
Cu alloy metallization for self-forming barrier process 国際会議

J. Iijima, M. Haneda, M. Wada

International Interconnect Technology Conference　2006年6月5日
Cu alloy metallization for self-forming barrier process 国際会議

Materials Research Society Syposium　2006年4月17日
Cu microstcture impact on reliability 国際会議

International Reliability Pysics Symposium　2006年3月26日
Cu/ILD界面バリア層の材料科学

応用物理学会　2006年3月
Deformation mechanisms and their grain-size dependence in magnesium alloys 国際会議

Workshop on fine grained materials: opportunities and challenges　2005年11月
Self-forming barrier process with Mn addition in Cu metallization 国際会議

Advanced metallization conference　2005年10月
Self-forming barrier with Cu alloy metallization and its effects on reliability 国際会議

International workshop on stress-induced phenomenoa in metallization　2005年9月
Quantitative evaluation of interface adhesion strength in multilayer films by nanoscratch test 国際会議

2005 MRS Spring Meeting　2005年4月
Texture-related reliability problems of Cu thin films for semiconductor applications 国際会議

TMS Spring Meeting　2005年3月
Texture and grain-size dependence on deformation mechanisms in Mg alloys 国際会議

Int. Conf. on Magnesium-Science, Technology and Applications　2004年9月20日
Role of twinning on the deformation and failure of hot-rolled AZ31 magnesium alloy 国際会議

Int. Conf. on Magnesium-Science, Technology and Applications　2004年9月20日
Interface Adhesion and Phase Formation in Cu Interconnect 国際会議

Solid State Devices and Materials, Tokyo　2004年9月15日
Plastic anisotropy and its effects on mechanical parameters in Mg alloys at RT 国際会議

2004 TMS Spring Meeting　2004年3月15日
Reliability of Cu/barrier structure in nanometer interconnect lines 国際会議

2004 TMS Spring Meeting, Charlotte　2004年3月15日
Dislocation Plasticity and Complementary Deformation Mechanisms in Polycrystalline Mg Alloys 国際会議

3rd Int. Symp. on Designing, Processing and Properties of Advanced Engineering Materials　2003年11月5日
Relationship between film texture and reliability of Cu interconnects 国際会議

2003 TMS Spring Meeting　2003年3月3日
Strength and Denctility of Mg Alloys 国際会議

4th Pac. Rim Int. Conf. on Advanced Materials and Processing　2001年12月11日
Stress-induced voiding and texture control in Cu thin films 国際会議

International Workshop in Stress-Induced Phenomena in Metallization Metallization　2001年7月25日
Stress-induced a to b phase transformation in two-phase Ti alloys 国際会議

2nd International Symposium on Designing, Processing, and Properties of Advanced Eng. Mater.　2000年10月20日
Relationship between high-strain-rate superplasticity and interface microstructure in aluminum alloy composites 国際会議

Microscopy and Microanalysis '99　1999年8月1日
Deformation and Failure of Metallic Thin Films Caused by Thermal Stress 国際会議

Mechanical Properties of Films, Coatings and Interfacial Materials　1999年6月27日
Microstructure, Physical and Mechanical Properties, Primary creep resistance of Ti-6-22-22S alloy 国際会議

The 9th World Conference on Titanium　1999年6月7日
Study of primary creep of Ti-6-22-22S alloys 国際会議

Xi'an International Titanium Conference　1998年9月
Microstructure and Superplasticity in Al-Mg Alloy Composites Reinforced with Silicon Nitride Particles 国際会議

International Conference on Superplasticity of Advanced Materials　1997年1月29日
Structural Changes induced by Electron Irradiation 国際会議

International Conference on Beam Processing of Advanced Materials　1993年8月1日

詳細を見る詳細を閉じる

(プロシーディング) Proc. of Int'l Conf. of Beam Processing ofAdvanced Mater. TMS 1993 519 536
Electron-Beam Interaction and Defect Production in Diamond 国際会議

International Workshop on Electron Beam Assisted Processes　1993年1月13日

詳細を見る詳細を閉じる

(プロシーディング) Proc. of the Int'l Workshop on Electron Beam Assited Processes 1993 44 52
Beam-Solid Interactions 国際会議

Materials Research Society Fall Meeting　1992年11月30日
Tensile Behavior of Cold Rolled NiTi having an amorphous-crystalline microstructure 国際会議

NATO Advanced Institute　1992年6月28日

詳細を見る詳細を閉じる

(プロシーディング) Mechanical Properties and Deformation Behavior of Materials Having Ultra-Fine Microstructures Kluwer Academic Publishers 1993 323 328
Irradiation-induced amorphization as a result of Elastic Instability 国際会議

Materials Research Society Fall Meeting　1991年12月2日

︎全件表示 ︎最初の5件までを表示

共同研究・競争的資金等の研究課題 6

パワーデバイス用における金属・SiC界面のコンタクト抵抗の改善と力学的高信頼化競争的資金

制度名：The Other Research Programs

2005年4月～継続中
フレキシブルデバイス用のハイブリッド透明電極材料の開発競争的資金

制度名：The Other Research Programs

2003年4月～継続中
フレキシブル回路の界面密着強度の評価および改善競争的資金

制度名：The Other Research Programs

2002年4月～継続中
マグネシウム合金の変形機構競争的資金

制度名：The Other Research Programs

2000年4月～継続中
ナノスケールにおける界面密着強度の評価競争的資金

制度名：The Other Research Programs

2000年4月～継続中
先端半導体用の高信頼性合金配線の開発競争的資金

2000年4月～継続中

︎全件表示 ︎最初の5件までを表示

その他 5

CuMn成膜技術の研究

詳細を見る詳細を閉じる

CuMn成膜技術の研究
フレキシブルなセラミック積層フィルムの開発

詳細を見る詳細を閉じる

フレキシブルなセラミック積層フィルムの開発
45nm世代IC多層配線におけるバリア層自己形成プロセスの開発

詳細を見る詳細を閉じる

45nm世代IC多層配線におけるバリア層自己形成プロセスの開発
界面の物性評価

詳細を見る詳細を閉じる

界面の物性評価
界面制御された高信頼性Cu合金配線の開発

詳細を見る詳細を閉じる

界面制御された高信頼性Cu合金配線の開発