顔写真

アンドウ ダイスケ
安藤 大輔
Daisuke Ando
所属
大学院工学研究科 知能デバイス材料学専攻 ナノ材料物性学講座(極限材料物性学分野)
職名
准教授
学位
  • 博士(工学)(東北大学)

  • 修士(工学)(東北大学)

e-Rad 研究者番号
50615820

所属学協会 3

  • TMS

  • 軽金属学会

  • 金属学会

研究キーワード 9

  • 医療材料

  • 変形双晶

  • セラミックコーティング

  • 高温材料

  • 構造機能材料学

  • アルミニウム

  • マグネシウム

  • 材料組織学

  • 構造材料学

研究分野 1

  • ナノテク・材料 / 構造材料、機能材料 /

受賞 21

  1. 第80回 日本金属学会功績賞

    2022年3月 公益社団法人日本金属学会 Mg基合金の変形・破壊メカニズムとその高機能化に関する研究

  2. 令和3年度(第24回)日本マグネシウム協会賞 奨励賞

    2021年6月 一般社団法人 日本マグネシウム協会 マグネシウム合金の変形・破壊メカニズムとその高機能化に関する研究

  3. 東北大学ディスティングイッシュトリサーチャー

    2021年5月 東北大学

  4. 文部科学大臣表彰 若手研究者賞

    2021年4月 文部科学省 Mg合金の変形破壊メカニズムとその高機能化に関する研究

  5. 第42回本多記念研究奨励賞

    2021年2月 公益財団法人 本多記念会 マグネシウム合金の変形・破壊メカニズムとその高機能化 に関する研究

  6. 第36回軽金属奨励賞

    2019年11月 一般社団法人 軽金属学会 マグネシウム合金の変形機構解明および新規合金開発

  7. 第18回インテリジェント・コスモス奨励賞

    2019年5月 公益財団法人インテリジェント・コスモス学術振興財団 自己拡張性を有する生体分解性 マグネシウム合金ステントの開発

  8. LPSO2018 Excellent Poster Award

    2018年12月 The Fourth International symposium on Long-Period Stacking Ordered Structure and Mille-feuille Structure

  9. 第23回青葉工学研究奨励賞

    2017年12月 一般社団法人 青葉工学振興会

  10. 第14回 村上奨励賞

    2017年9月 公益財団法人 日本金属学会 超弾性・形状記憶能を有したマグネシウム合金の創製

  11. 第27回 トーキン科学技術賞最優秀賞

    2017年3月8日 公益財団法人トーキン科学技術振興財団

  12. 第11回 JIM/TMS Young Leader International Scholar

    2017年3月1日 The Japan Institute of Metals and Materials / The Minerals, Metals & Materials Society

  13. 第56回原田研究奨励賞

    2016年7月 公益財団法人 本多記念会

  14. 第24 回日本金属学会若手講演論文賞

    2016年3月 日本金属学会

  15. 第25 回日本金属学会奨励賞【力学特性】

    2015年9月 日本金属学会

  16. 第23 回日本金属学会若手講演論文賞

    2015年9月 日本金属学会

  17. 日本金属学会論文賞[力学特性部門]

    2009年9月 日本金属学会

  18. 財団法人青葉工学振興会及川研究奨励賞

    2008年9月 財団法人青葉工学振興会

  19. 日本マグネシウム協会齋藤マグネシウム学生奨学金

    2007年12月 日本マグネシウム協会

  20. The 2nd Asian Symposium on Magnesium Alloys Best Poster Award受賞

    2007年10月 The 2nd Asian Symposium on Magnesium Alloys

  21. 日本金属学会若手講演論文賞受賞

    2007年3月 日本金属学会

︎全件表示 ︎最初の5件までを表示

論文 101

  1. Room temperature superelasticity in a lightweight shape memory Mg alloy 査読有り

    K. Yamagishi, Y. Ogawa, D. Ando, Y. Sutou, J. Koike

    Scripta Materialia 168 114-118 2019年7月15日

    DOI: 10.1016/j.scriptamat.2019.04.023  

    ISSN:1359-6462

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    To realize a superelastic Mg-Sc lightweight alloy at room temperature, we investigated the stress–strain behavior of Mg-18.7 at.% Sc alloy sheets at room temperature with martensitic transformation starting temperature of approximately −90 °C. We found that the superelasticity of the alloy strongly depends on the grain size and a distinct room temperature superelasticity (~3% superelastic strain) was obtained in the alloy with a large grain size. The obtained maximum superelastic strain was smaller than that expected from the orientation dependence of the transformation strain. This result suggests that the stress-induced martensite phase was stabilized because of the introduction of slip defects.

  2. 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22日

    出版者・発行元:AMER ASSOC ADVANCEMENT SCIENCE

    DOI: 10.1126/science.aaf6524  

    ISSN:0036-8075

    eISSN:1095-9203

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    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 aMg SMA showing superelasticity of 4.4% at -150°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.

  3. 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 666 94-99 2016年6月1日

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/j.msea.2016.04.030  

    ISSN:0921-5093

    eISSN:1873-4936

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    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.

  4. 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8月25日

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.matlet.2015.06.057  

    ISSN:0167-577X

    eISSN:1873-4979

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    The effect of aging treatment on microstructure and hardness in a Mg-16.8 at%Sc alloy with a bcc phase (β-Sc) was investigated. The hardness increased dramatically upon aging, owing to the formation of a fine hcp phase (α-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.

  5. 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 600 145-152 2014年4月10日

    DOI: 10.1016/j.msea.2014.02.010  

    ISSN:0921-5093

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    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. © 2014 Elsevier B.V.

  6. 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 600 (10) 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

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    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. © 2014 Elsevier B.V.

  7. 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

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    Fatigue tests were performed on AZ31 Mg alloys at room temperature in tension cycles. Deformation twinning of the {101̄2} type was observed both below and above the fatigue limit, indicating that the {101̄2} 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 {1011}-{101̄2} double twinning that led to the formation of large surface steps, cracks and eventual failure. © 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  8. 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

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    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 {101̄1}-{101̄2} double twin type with their basal planes tilted by 37° 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. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  9. NbTe<inf>4</inf> Phase-Change Material: Breaking the Phase-Change Temperature Balance in 2D Van der Waals Transition-Metal Binary Chalcogenide

    Yi Shuang, Qian Chen, Mihyeon Kim, Yinli Wang, Yuta Saito, Shogo Hatayama, Paul Fons, Daisuke Ando, Momoji Kubo, Yuji Sutou

    Advanced Materials 35 (39) 2023年9月27日

    DOI: 10.1002/adma.202303646  

    ISSN:0935-9648

    eISSN:1521-4095

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    2D van der Waals (vdW) transition metal di-chalcogenides (TMDs) have garnered significant attention in the nonvolatile memory field for their tunable electrical properties, scalability, and potential for phase engineering. However, their complex switching mechanism and complicated fabrication methods pose challenges for mass production. Sputtering is a promising technique for large-area 2D vdW TMD fabrication, but the high melting point (typically Tm > 1000 °C) of TMDs requires elevated temperatures for good crystallinity. This study focuses on the low-Tm 2D vdW TM tetra-chalcogenides and identifies NbTe4 as a promising candidate with an ultra-low Tm of around 447 °C (onset temperature). As-grown NbTe4 forms an amorphous phase upon deposition that can be crystallized by annealing at temperatures above 272 °C. The simultaneous presence of a low Tm and a high crystallization temperature Tc can resolve important issues facing current phase-change memory compounds, such as high Reset energies and poor thermal stability of the amorphous phase. Therefore, NbTe4 holds great promise as a potential solution to these issues.

  10. B2 Ordering and Its Effect on Room Temperature Superelasticity in Mg–Sc Alloy

    Keisuke Yamagishi, Yuta Takeuchi, Yukiko Ogawa, Daisuke Ando, Yuji Sutou

    Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science 54 (7) 2841-2848 2023年7月

    DOI: 10.1007/s11661-023-07062-4  

    ISSN:1073-5623

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    We investigated the effect of aging treatment on the microstructure and superelasticity of Mg–Sc alloy. Transmission electron microscopy observations and tensile tests revealed that aging treatment at 100 °C caused ordering of the parent phase from a disordered bcc (A2) to an ordered bcc (B2) structure and considerably improved the superelasticity at room temperature. The maximum superelastic recovery obtained in an aged bamboo-crystalline sample was 4.6 pct, which is comparable to the conventional shape memory alloys.

  11. Evaluation of cholesterol crystals in carotid plaque by dual energy computed tomography

    Takuya Saito, Hidenori Endo, Daisuke Ando, Itsuki Miyagi, Yuichi Kawabata, Mika Watanabe, Atsushi Saito, Miki Fujimura, Yukako Yazawa

    Neuroradiology 65 (5) 979-982 2023年5月

    DOI: 10.1007/s00234-023-03138-5  

    ISSN:0028-3940

    eISSN:1432-1920

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    Cholesterol crystals (CCs) in carotid plaques might be an indicator of vulnerability, although they have not been fully investigated and non-invasive methods of assessment have not been established. This study examines the validity of assessing CCs using dual-energy computed tomography (DECT) that uses X-rays with different tube voltages for imaging, allowing material discrimination. We retrospectively evaluated patients who had undergone preoperative cervical computed tomography angiography and carotid endarterectomy between December 2019 and July 2020. We developed CC-based material decomposition images (MDIs) by scanning CCs crystallized in the laboratory using DECT. We compared the percentage of CCs in stained slides defined by cholesterol clefts with the percentage of CCs displayed by CC-based MDIs. Thirty-seven pathological sections were obtained from 12 patients. Thirty-two sections had CCs; of these, 30 had CCs on CC-based MDIs. CC-based MDIs and pathological specimens showed a strong correlation. Thus, DECT allows the evaluation of CCs in carotid artery plaques.

  12. Abnormal grain growth through cyclic heat treatment in a Mg–Sc alloy

    K. Yamagishi, K. Onyam, Y. Ogawa, D. Ando, Y. Sutou

    Journal of Alloys and Compounds 938 2023年3月25日

    DOI: 10.1016/j.jallcom.2022.168415  

    ISSN:0925-8388

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    Enlarging the grain size in Mg–Sc alloys can greatly improve superelasticity. The impact of heat treatment conditions on abnormal grain growth (AGG) caused by phase transformation through cyclic heat treatment (CHT) was investigated in this study. In the CHT process between temperatures in a β single-phase region (Tβ) and α + β two-phase region (Tα+β), lowering the Tα+β resulted in a uniform huge grain size after AGG. In the heating process of the CHT from the Tα+β to the Tβ, the decrease in the heating rate was found to be ineffective in realizing huge grain size because the number of grains that can start AGG increases, which causes the collision of the abnormally growing grains with each other. We also revealed one of the key factors for the AGG to occur. Subgrains, which were formed through CHT, not only act as an additional driving force for grain growth but also shorten the required time for AGG nucleation.

  13. Adjustable room temperature deformation behavior of Mg–Sc alloy: From superelasticity to slip deformation via TRIP effect

    Keisuke Yamagishi, Yukiko Ogawa, Daisuke Ando, Yuji Sutou

    Journal of Alloys and Compounds 931 2023年1月10日

    DOI: 10.1016/j.jallcom.2022.167507  

    ISSN:0925-8388

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    This study investigated the transformation-induced plasticity (TRIP) effect in Mg–Sc alloys with β single-phase (body-centered cubic) structure. A Mg-19.8 at% Sc alloy showed fracture strain of ∼53 % accompanied by necking propagation with increasing the tensile strain at room temperature. An X-ray diffraction analysis and transmission electron microscopy observations confirmed the existence of a hexagonal close-packed phase beside the β matrix phase during and after the tensile test; this indicates a strain-induced martensitic transformation, i.e., the TRIP effect induced superior ductility. Moreover, the study revealed a threshold Sc content of ∼19.5 at% Sc at which the deformation behavior at room temperature changes from superelasticity to TRIP. The TRIP Mg–Sc alloys exhibited fracture strain from 45 % to 66 % and ultimate tensile strength (UTS) above 220 MPa to overcome the tradeoff between the fracture strain and UTS of conventional Mg alloys.

  14. Low-Temperature Oxidation-Sintering Behaviors of Cu Fine Particles

    Nobuaki Takeuchi, Daisuke Ando, Koike Junichi, Yuji Sutou

    Materials Transactions 64 (4) 931-938 2023年

    DOI: 10.2320/matertrans.MT-M2022219  

    ISSN:1345-9678

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    Cu fine-particle paste is a promising material to form a low-cost interconnect for flexible electronics devices. It has been reported that Cu particles can be sintered at low temperature (well below the half of the melting point) through two-step heat treatment processes of oxidation and reduction. However, the mechanism of the low temperature sintering is not clear yet. In this study, we investigated the oxidation sintering process of Cu fine particles by thermal gravimetric analysis (TGA) in the temperature range of 200°C~300°C, X-ray diffraction (XRD), and microstructural observation. It was found from TGA that the oxidation process was initially rate-controlled by surface reaction and then by Cu diffusion at grain boundaries of Cu2O. Transmission electron microscopy observation revealed the formation of a core (Cu)-shell (Cu2O) structure during the oxidation process. The adjacent Cu2O shells were bonded to each other resulting in a cross-linked structure. The subsequent reduction process led to the formation of a porous structure by oxygen removal, but the cross-linked structure was maintained, which would make the low-temperature sintered Cu body as robust as solidified solder and sintered Ag paste.

  15. Development of Mg-Based Superelastic Alloy Through Aging Heat Treatment

    Keisuke Yamagishi, Yukiko Ogawa, Daisuke Ando, Yuji Sutou

    Minerals, Metals and Materials Series 181-187 2023年

    DOI: 10.1007/978-3-031-22645-8_34  

    ISSN:2367-1181

    eISSN:2367-1696

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    The effect of aging heat treatment on microstructure, hardness, and superelasticity at room temperature was investigated herein for Mg-18.8 at.% Sc alloy. The hardness of the alloy is increased via aging heat treatment at temperatures between 423 and 523 K, from * 90 Hv (as-quenched condition) to a maximum of 180 Hv. Aging heat treatment at a higher temperature reduces the incubation time before the onset of age hardening. Scanning electron microscopy observations and X-ray diffraction analysis showed that the precipitation of hexagonal close-packed (a) phases within the body-centered cubic (b) matrix phase causes age hardening and the hardness value almost depends linearly on the volume fraction of a precipitates. Furthermore, the a precipitates formed via aging heat treatment can be deformed along with b matrix phase upon stress-induced martensitic transformation in a sample with * 10% volume fraction of a precipitates, resulting in a slight reduction in stress hysteresis and a minor increase in superelastic recovery compared with the as-quenched condition.

  16. Microstructure Evolution and Local Hardness of Mg–Y–Zn Alloys Processed by ECAE 査読有り

    Motohiro Yuasa, Ryoichi Sato, Takao Hoshino, Daisuke Ando, Yoshikazu Todaka, Hiroyuki Miyamoto, Hidetoshi Somekawa

    MATERIALS TRANSACTIONS 64 (4) 730-734 2023年

    出版者・発行元:Japan Institute of Metals

    DOI: 10.2320/matertrans.mt-md2022018  

    ISSN:1345-9678

    eISSN:1347-5320

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    Mg-9at%Y-6 at%Zn and Mg-2at%Y-1 at%Zn alloys were processed by equal-channel-angular extrusion (ECAE) to investigate their microstructure evolution and local hardness. The area fraction of the kink bands in the Mg-9 at%Y-6at%Zn alloys increased with increasing the number of ECAE passes, resulting in higher hardness. In contrast, the number of kink boundaries in the local region near the indentation was almost constant. The relationship between the microstructure factors of the kink bands and the local hardness is discussed in comparison with the forged alloy. In the Mg-2 at%Y-1at%Zn alloys, the microstructural evolution of the alpha-Mg matrix phase and long-period stacking ordered (LPSO) phase by 1-pass ECAE and the increase in local hardness were discussed.

  17. Predominant factor for effectively forming kink boundaries in Mg–Y–Zn alloy through wrought-process

    Hidetoshi Somekawa, Motohiro Yuasa, Daisuke Ando, Yoshikazu Todaka

    Materials Science and Engineering A 858 2022年11月14日

    DOI: 10.1016/j.msea.2022.144168  

    ISSN:0921-5093

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    The numerical and experimental results reveal that application of large strain to bulk Mg-9at.%Y-6at.%Zn alloy leads to formation of a high density of deformation kink boundaries. Shear strain is a controllable parameter for the effective induction of kink boundaries, from the processing viewpoint. This correlation is also applicable to wrought-processed alloys containing the LPSO phase.

  18. Effect of N dopants on the phase change characteristics of Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf> film revealed by changes in optical properties

    Yi Shuang, Shogo Hatayama, Daisuke Ando, Yuji Sutou

    Applied Surface Science 601 2022年11月1日

    DOI: 10.1016/j.apsusc.2022.154189  

    ISSN:0169-4332

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    In this study, the microstructure, optical properties, and crystallization kinetics of N-doped Cr2Ge2Te6 (NCrGT) phase change materials (PCMs) were investigated. The NCrGT films exhibited a reflectance decrease upon crystallization, which is opposite to the behavior of CrGT and traditional PCMs, such as Ge2Sb2Te5. Additionally, the N dopants were confirmed to accelerate the crystallization speed of CrGT. Furthermore, the crystallized spots on the NCrGT films were found to be reamorphized by laser irradiation at a lower power than is required for CrGT, indicating a reversible laser pulse-induced phase transition and a lower thermal cost resulting from the incorporation of N. The faster crystallization speed of the NCrGT films originated from their shorter incubation time and simplified crystallization process tuned by the local bonding configuration close to N atoms. Our findings demonstrate that adding N dopants can dramatically alter the optical properties of CrGT, leading to faster crystallization and reduced power consumption.

  19. Catalyze hydrolysis reaction for hydrogen generation by Mg/Mg<inf>2</inf>Ca nanolamellar structure in Mg–Ca alloys

    Tomoharu Uchiyama, Daisuke Ando, Yuji Sutou

    Journal of Alloys and Compounds 919 2022年10月25日

    DOI: 10.1016/j.jallcom.2022.165767  

    ISSN:0925-8388

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    The hydrogen generating characteristics of Mg–Ca alloys with Mg/Mg2Ca nanolamellar structures in the hydrolysis reaction with artificial seawater—a 3.5-wt% NaCl aqueous solution—were investigated for a new hydrogen supply source application. The concept of this study was to fabricate a complete hydrolysis reaction alloy using nanolamellar structure of Mg and Mg2Ca having an electrochemically less noble product than Mg. The hydrolysis reaction properties of Mg-10Ca, Mg-15Ca, Mg-16.2Ca, Mg-20Ca, and Mg2Ca were compared with respect to microstructure, which is the volume fraction of the primary phase and its nanolamellar width, and reaction temperatures at 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, and 60 °C. Mg-16.2Ca and Mg-20Ca reacted completely even at room temperature and became white powders comprising Mg(OH)2, Ca(OH)2, and CaCO3 after 9–14 days without changing the solvent. The hydrolysis reaction rates of the Mg–Ca alloys in the temperature range of 10–40 °C were fast in the order of Mg-16.2Ca ≥ Mg-20Ca ≥ Mg-10Ca ≥ Mg-15Ca. From the results of the hydrolysis reaction rate dependency on temperature, the activation energies of Mg-10Ca, Mg-15Ca, Mg-16.2Ca, Mg-20Ca, and Mg2Ca were estimated to be 41.27, 43.39, 22.07, 15.46, and 29.27 kJ mol−1, respectively. This study revealed that the eutectic structure with several nanogalvanic cells of Mg/Mg2Ca in the alloys accelerated the hydrolysis reaction and completely reacted with artificial seawater for hydrogen generation.

  20. Thermal stress control of the polymorphic transformation in MnTe semiconductor films

    Shunsuke Mori, Yinli Wang, Daisuke Ando, Fumio Narita, Yuji Sutou

    Materialia 24 101493-101493 2022年8月

    出版者・発行元:Elsevier BV

    DOI: 10.1016/j.mtla.2022.101493  

    ISSN:2589-1529

    eISSN:2589-1529

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    The polymorphic transformation of the compound MnTe between its wurtzite-type (β) and nickeline-type (α) crystalline phase results in a significant change in its physical properties. In this study, the effect of thermal stress on the β→α transformation in MnTe films was investigated by varying the materials used for the MnTe film's capping layers (Ni, Ti, Mo, W, and SiO2). The capping layer/β-MnTe stacked films were heated above the transformation temperature, and the volume fraction of the material that transformed during the heating was evaluated using XRD measurements. In-plane compressive thermal stress observed at the interface between the MnTe film and capping layer promotes the β→α transformation. The in-plane thermal stress at the interface that induces the β→α transformation has linear temperature dependence, and the gradient of this dependence was estimated to be around −20.5 MPa K−1. The obtained results indicate that the polymorphic transformation of the MnTe film can be controlled by the thermal stress generated by mechanical constraints induced by the surrounding layers. The results of this study offer new insights into the design of MnTe-based phase-change devices and the application of straintronics in semiconductor films.

  21. Application of deep neural network learning in composites design 招待有り 査読有り

    Yinli Wang, Constantinos Soutis, Daisuke Ando, Yuji Sutou, Fumio Narita

    2 (1) 118-171 2022年4月8日

    出版者・発行元:None

    DOI: 10.1080/26889277.2022.2053302  

    eISSN:2688-9277

  22. Electrical Conduction Mechanism of β-MnTe Thin Film with Wurtzite-Type Structure Using Radiofrequency Magnetron Sputtering

    Mihyeon Kim, Shunsuke Mori, Yi Shuang, Shogo Hatayama, Daisuke Ando, Yuji Sutou

    Physica Status Solidi - Rapid Research Letters 16 (9) 2022年

    DOI: 10.1002/pssr.202100641  

    ISSN:1862-6254

    eISSN:1862-6270

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    Manganese telluride (MnTe) compound is known to be a polymorphic chalcogenide. Recently, it has been reported that the MnTe shows nonvolatile memory properties with a significant change in resistance via a polymorphic transition between NiAs-type (NC) structure (low resistance) and wurtzite-type (WZ) structure (high resistance). This crystalline polymorphic MnTe is expected to realize a phase-change memory with fast operation speed and ultralow operation energy. While the NC-MnTe, generally designated as α-MnTe, is intensively studied, WZ-MnTe is still poorly understood. Herein this study, electrical conduction mechanism of a β-MnTe film with a WZ-type structure is studied. A resistivity, Hall mobility, and Seebeck coefficient of the WZ-MnTe film are measured at various temperatures. The temperature dependence of resistivity in the temperature range 120–300 K clearly indicates that the WZ-MnTe film shows a variable-range hopping (VRH) conduction. In this temperature region, with decreasing temperature, the conduction mechanism changes from Mott–VRH conduction to Efros–Shklovskii VRH conduction at about 210 K. Furthermore, the low thermally activated Hall mobility, occurrence of Hall-effect sign anomaly, and relatively low activation energy for thermopower, which are the observed results, suggest that the small polaron hopping conduction is dominant above 310 K.

  23. Kink bands strengthening of Mg-Y-Zn alloy via various wrought-processing

    Hidetoshi Somekawa, Yoshikazu Todaka, Daisuke Ando, Motohiro Yuasa

    Materials Letters 304 130653-130653 2021年12月

    出版者・発行元:Elsevier BV

    DOI: 10.1016/j.matlet.2021.130653  

    ISSN:0167-577X

    eISSN:1873-4979

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    Microstructures and mechanical properties were investigated using Mg-9at.%Y-6at.%Zn alloy produced by several types of wrought-processing, i.e., forging, rolling, extrusion, equal-channel-angular extrusion, caliber rolling and high-pressure-torsion. Regardless of the wrought-processing method, deformation kink bands were induced to the long-periodic stacking ordered phase. Hardness increased with higher magnitude of applied strains. However, the inducing direction of shear strain affected the hardness values, and multiple shear strains were effective in improving the mechanical properties. For instance, the alloy produced by extrusion-torsion process exhibited yield strength in compression exceeding 600 MPa, which was over 1.7 times higher than that of the direct extruded alloy.

  24. Intrinsic kink bands strengthening induced by several wrought-processes in Mg-Y-Zn alloys containing LPSO phase

    Hidetoshi Somekawa, Daisuke Ando, Koji Hagihara, Michiaki Yamasaki, Yoshihito Kawamura

    Materials Characterization 179 2021年9月

    DOI: 10.1016/j.matchar.2021.111348  

    ISSN:1044-5803

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    The kink bands strengthening effect was investigated using Mg-9at.%Y-6at.%Zn alloys produced by caliber rolling or extrusion at intermediate and elevated temperatures (373 K and more than 673 K). The results of microstructural observations showed that deformation kink bands were induced in all the alloys, regardless of the wrought-processing method and the processing temperatures. Micro-Vickers hardness tests showed that the regions including kink bands exhibited a higher hardness than those without kink bands, which reveal intrinsic kink bands strengthening. Interestingly, the trend of this kink bands strengthening effect could be expressed by an empirical relationship, which was divided into two lines associated with the wrought-processing temperature. This tendency did not appear to depend on the wrought-processing method. The alloys produced at the intermediate temperature showed markedly superior hardness, since, in addition to the kink bands strengthening, the residual strains/dislocations around kink boundaries contributed to obstruct dislocation slips.

  25. Evolution of the local structure surrounding nitrogen atoms upon the amorphous to crystalline phase transition in nitrogen-doped Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf> phase-change material

    Yi Shuang, Shogo Hatayama, Yuta Saito, Paul Fons, Alexander V. Kolobov, Daisuke Ando, Yuji Sutou

    Applied Surface Science 556 2021年8月1日

    DOI: 10.1016/j.apsusc.2021.149760  

    ISSN:0169-4332

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    Phase-change memory based upon resistive switching due to phase transitions between the amorphous and crystalline phases of chalcogenide-based phase-change materials (PCMs) has been widely studied for the next generation non-volatile memory (NVM). Unlike traditional PCMs such as Ge2Sb2Te5, nitrogen doped Cr2Ge2Te6 (NCrGT) was reported to not exhibit a bulk resistivity change upon the amorphous to crystalline phase transition, instead the contact resistivity contrast in the presence of metal electrodes was found to play an essential role. In the current study, a distinct difference in the local structure around N atoms in amorphous and crystalline NCrGT films was found using X-ray absorption near-edge spectroscopy (XANES) and hard X-ray photoelectron spectroscopy (HAXPES). Cr[sbnd]N and Ge[sbnd]N bonds and N2 molecular vibrational modes were found to be present in an amorphous NCrGT film, while N atoms were found to be present at Te substitutional positions in the crystalline phase. A previous study revealed that Cr nanoclusters are present in the undoped amorphous phase, whose concentration was found to decrease as crystallization progressed leading to an increase in the resistivity. In the present study, it was determined that N doping inhibits Cr nanocluster formation in the amorphous NCrGT phase and leads to a constant Cr nanocluster volume fraction even after crystallization, ensuring negligible resistance contrast between the amorphous and crystalline phases. These results will prove useful in understanding the role of dopant elements in the promising PCM CrGT.

  26. Thermal stability and polymorphic transformation kinetics in β-MnTe films deposited via radiofrequency magnetron sputtering

    Shunsuke Mori, Shogo Hatayama, Daisuke Ando, Yuji Sutou

    Japanese Journal of Applied Physics 60 (4) 045504-045504 2021年4月

    出版者・発行元:{IOP} Publishing

    DOI: 10.35848/1347-4065/abee03  

    ISSN:0021-4922

    eISSN:1347-4065

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    A manganese telluride (MnTe) compound is an interesting polymorphic semiconductor with physical properties differing greatly among various polymorphs. In this study, the thermal stability and polymorphic transformation kinetics in β-MnTe films obtained via radiofrequency magnetron sputtering were investigated. The obtained MnTe films with a composition range of 50.5-46.1 at.% Te exhibited a single β phase. The polymorphic transformation temperature from the β (wurtzite-type) to an α (NiAs-type) phase decreased with increasing the Te content. In the non-isothermal analysis using differential scanning calorimetry, the activation energy for β → α transformation was measured to be 1.41 eV, based on Kissinger plots. The retention time of β-MnTe was also investigated via the Ozawa method, and it was estimated to be retained for 4.5 109 years at 25 C. The estimated Avrami exponent of 3.5 indicated that two- and three-dimensional growth at a constant nucleation rate was dominant at the intermediate stage of β → α transformation.

  27. High Contact Resistivity Enabling Low-Energy Operation in Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf>-Based Phase-Change Random Access Memory

    Shogo Hatayama, Yasunori Abe, Daisuke Ando, Yuji Sutou

    Physica Status Solidi - Rapid Research Letters 15 (3) 2021年3月

    DOI: 10.1002/pssr.202000392  

    ISSN:1862-6254

    eISSN:1862-6270

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    A phase-change material (PCM) exhibiting a significant difference in resistance between the amorphous and crystalline phases can be used for phase-change random access memory (PCRAM). Reduction of the energy to operate is one of the major challenges in PCRAM technology. One strategy for energy reduction is to increase the resistance of the memory device in the crystalline state of the PCM. Cr Ge Te (CrGT) shows p-type semiconductor characteristics in both the amorphous and crystalline phases. A CrGT-based memory device shows a contact resistance–dominant behavior, suggesting that the resistance of a CrGT-based memory device can be increased by changing the electrode material. The contact resistivity (ρ ) of a CrGT/electrode increases with a decrease in the work function of the electrode material in both amorphous and crystalline phases, as with general p-type semiconductor materials. The highest ρ is observed for a LaB electrode. The resistance of the CrGT-based device with a LaB electrode (LaB device) is three or four orders of magnitude greater than that of a device with a W electrode (W device). The LaB device is indicated to require much smaller operation energy than the W device. 2 2 6 c c 6 6 6 6

  28. Temperature-Dependent Electronic Transport in Non-Bulk-Resistance-Variation Nitrogen-Doped Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf> Phase-Change Material

    Yi Shuang, Shogo Hatayama, Daisuke Ando, Yuji Sutou

    Physica Status Solidi - Rapid Research Letters 15 (3) 2021年3月

    DOI: 10.1002/pssr.202000415  

    ISSN:1862-6254

    eISSN:1862-6270

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    The electronic transport mechanism of the nitrogen-doped Cr Ge Te (NCrGT) phase-change material (PCM) is studied, showing almost zero resistivity variation upon phase transition. A similar low-temperature variable-range hopping (VRH) behavior in both the amorphous and crystalline phases of the NCrGT PCM is observed by measuring the temperature-dependent resistivity. At high temperatures above 300 K, the conduction mechanism in the amorphous NCrGT is thermally activated band conduction, while the carrier transport in the crystalline NCrGT is still driven by VRH. Moreover, Hall property measurements reveal a thermally activated carrier in the amorphous NCrGT and mobility-driven hopping conduction in the crystalline NCrGT at a high temperature range from 300 to 400 K. The conduction mechanism difference between the amorphous and crystalline NCrGT/tungsten (W) contacts is further investigated by measuring the temperature-dependent I–V characteristics. The conduction in the amorphous NCrGT/W contact is dominated by thermionic-field emission, while the transport mechanism through the crystalline NCrGT/W interface is controlled by the defect-assisted tunneling current. Such noticeable conduction mechanism variation results in a large contact resistance contrast in a memory cell. 2 2 6

  29. Potential of low-resistivity Cu<inf>2</inf>Mg for highly scaled interconnects and its challenges

    Linghan Chen, Qian Chen, Daisuke Ando, Yuji Sutou, Momoji Kubo, Junichi Koike

    Applied Surface Science 537 2021年1月30日

    DOI: 10.1016/j.apsusc.2020.148035  

    ISSN:0169-4332

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    Materials with low resistivity in small dimensions are urgently desired to replace Cu for highly scaled interconnection in advanced integrated circuits. This study reports the possibility of Cu Mg intermetallic compound as a Cu alternative by showing adequate adhesion on SiO , a low resistivity of 25.5 μΩcm at 5 nm film thickness and good trench-filling capability in trench width of 38 or 23 nm by sputtering reflow. However, annealing at 400 °C for 30 min led to the dielectric current leakage associated with the formation of a thick MgO layer. Furthermore, Mg composition inside the trenches was less than the stoichiometric Cu Mg composition. Theoretical calculation of surface diffusion process revealed that the adatom hopping of Mg atoms was slower than that of Cu atoms, which resulted in the Mg-poor composition inside the trenches. 2 2 2

  30. Interdiffusion reliability and resistivity scaling of intermetallic compounds as advanced interconnect materials

    Linghan Chen, Sushant Kumar, Masataka Yahagi, Daisuke Ando, Yuji Sutou, Daniel Gall, Ravishankar Sundararaman, Junichi Koike

    Journal of Applied Physics 129 (3) 2021年1月21日

    DOI: 10.1063/5.0026837  

    ISSN:0021-8979

    eISSN:1089-7550

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    Intermetallic compounds have been proposed as potential interconnect materials for advanced semiconductor devices. This study reports the interdiffusion reliability and resistivity scaling of three low-resistivity intermetallic compounds (Cu2Mg, CuAl2, and NiAl) formed on thermally grown SiO2. Experimental observations and thermodynamic calculations indicated good interdiffusion reliability with CuAl2 and NiAl but not with Cu2Mg. This was due to slow reaction between Al and SiO2 in conjunction with strong chemical bonds of Cu-Al and Ni-Al. As for resistivity scaling, all three intermetallic compounds showed better resistivity scalability than Cu. Resistivity of the thin films was measured and characteristic parameters were obtained by curve fitting using a classical scattering model. First-principles calculations were carried out to determine the electron mean free path and bulk resistivity in order to explain the resistivity scaling. The results showed the importance of having optimum microstructure features, i.e., low-defect-density surface, interface, and grain boundaries in addition to optimum material properties, i.e., a short mean free path and low bulk resistivity. CuAl2 and NiAl appeared to satisfy the interdiffusion and resistivity conditions and be promising candidates to replace Cu interconnections for future devices.

  31. Texture Formation through Thermomechanical Treatment and Its Effect on Superelasticity in Mg–Sc Shape Memory Alloy 査読有り

    Keisuke Yamagishi, Daisuke Ando, Yuji Sutou, Yukiko Ogawa

    MATERIALS TRANSACTIONS 61 (12) 2270-2275 2020年12月1日

    出版者・発行元:None

    DOI: 10.2320/matertrans.mt-m2020244  

    ISSN:1347-5320

  32. Reversible displacive transformation in MnTe polymorphic semiconductor

    Shunsuke Mori, Shogo Hatayama, Yi Shuang, Daisuke Ando, Yuji Sutou

    Nature Communications 11 (1) 2020年12月1日

    DOI: 10.1038/s41467-019-13747-5  

    eISSN:2041-1723

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    Displacive transformation is a diffusionless transition through shearing and shuffling of atoms. Diffusionless displacive transition with modifications in physical properties can help manufacture fast semiconducting devices for applications such as data storage and switching. MnTe is known as a polymorphic compound. Here we show that a MnTe semiconductor film exhibits a reversible displacive transformation based on an atomic-plane shuffling mechanism, which results in large electrical and optical contrasts. We found that MnTe polycrystalline films show reversible resistive switching via fast Joule heating and enable nonvolatile memory with lower energy and faster operation compared with conventional phase-change materials showing diffusional amorphous-to-crystalline transition. We also found that the optical reflectance of MnTe films can be reversibly changed by laser heating. The present findings offer new insights into developing low power consumption and fast-operation electronic and photonic phase-change devices.

  33. Sequential two-stage displacive transformation from β to α via β′ phase in polymorphic MnTe film

    Shunsuke Mori, Daisuke Ando, Yuji Sutou

    Materials and Design 196 2020年11月

    DOI: 10.1016/j.matdes.2020.109141  

    ISSN:0264-1275

    eISSN:1873-4197

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    MnTe films exhibit a remarkable change in physical properties upon polymorphic transformation from β (wurtzite-type) to α (nickeline-type) phase. In this study, the mechanism of the β to α transformation in MnTe films capped with a tungsten layer during isothermal annealing at 500 °C was investigated. X-ray diffraction analyses revealed that the out-of-plane c-axis orientation was maintained during the polymorphic transformation. High-resolution transmission electron microscopy revealed that the β-phase transformed to the α-phase via a β′-phase which has a wurtzite-type structure as the β-phase but with a slight difference in the coordinates of the Te atoms. The β → β′ transformation was induced by the puckering process during which Mn- and Te-atomic planes shift in opposite directions along the c-axis, whereas the β′ → α transformation was induced by a buckling process during which pairs of Mn- and Te-atomic planes alternately move to the opposite directions along the 210 direction. Meanwhile, in the MnTe film without the tungsten capping layer, the out-of-plane c-axis orientation was not retained during the polymorphic transformation. These results imply that the sequential two-stage polymorphic transformation maintaining the out-of-plane c-axis orientation is caused by the constraint on the MnTe film induced by the tungsten capping layer.

  34. Texture formation through thermomechanical treatment and its effect on superelasticity in MgSc

    Shape Memory Alloy, Keisuke Yamagishi, Daisuke Ando, Yuji Sutou, Yukiko Ogawa

    Materials Transactions 61 (12) 2270-2275 2020年10月30日

    DOI: 10.2320/matertrans.MT-M2020244  

    ISSN:1345-9678

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    The formation of texture through thermomechanical treatment was investigated in Mg18.8 at% Sc shape memory alloy to enhance its superelasticity at room temperature. The samples were cold rolled in an phase or in a β phase and then finally heat treated at 690C followed by water quenching to obtain a β phase. In the case of cold rolling in the phase, a basal-plane texture was formed, while no preferential texture was observed along in-plane direction. After the final heat treatment, {011}(uvw)β transformation texture was obtained, according to Burgers relationship, indicating no improvement of the superelasticity along in-plane direction. In the case of the cold rolling in the β phase, a weak {111}(011)β recrystallization texture was obtained. The sample showed about 0.65% superelastic tensile strain along rolling direction, while that along transverse direction (//∼(113)β) showed only about 0.43%. This trend is in good agreement with the orientation dependence of the transformation strain, but, the obtained superelastic strain was much lower than the expected value, which is due to the weak texture and suggests the existence of a strong grain constraint in the MgSc shape memory alloy.

  35. Possibility of Cu2Mg for Liner-Barrier Free Interconnects

    Linghan Chen, Daisuke Ando, Yuji Sutou, Masataka Yahagi, Junichi Koike

    2020 IEEE International Interconnect Technology Conference (IITC) 2020年10月5日

    出版者・発行元:IEEE

    DOI: 10.1109/iitc47697.2020.9515588  

  36. Nitrogen doping-induced local structure change in a Cr2Ge2Te6 inverse resistance phase-change material

    Yi Shuang, Shogo Hatayama, Hiroshi Tanimura, Daisuke Ando, Tetsu Ichitsubo, Yuji Sutou

    MATERIALS ADVANCES 1 (7) 2426-2432 2020年10月

    出版者・発行元:ROYAL SOC CHEMISTRY

    DOI: 10.1039/d0ma00554a  

    eISSN:2633-5409

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    Fast and reversible switching utilizing the resistance contrast upon phase transition of phase change materials (PCMs) has been widely studied for next generation nonvolatile memory (NVM). Cr2Ge2Te6 (CrGT) and N-doped CrGT (NCrGT) PCMs have been demonstrated to show enhanced memory performance compared to the traditional Ge2Sb2Te5 (GST) PCM. We investigated here the crystallization behavior of Cr2Ge2Te6 (CrGT) and the effect of nitrogen (N) doping on it. We revealed that the Ge- or Cr-centered defective octahedral structure dominated in the amorphous phase of CrGT and the evolution of the c-axis-aligned Ge-Ge dimer and Cr-centered octahedral structure marked the beginning of crystallization. The further formation of new Cr-Te bonds resulted in a dramatic decline of carrier density in the crystalline phase, which explained the inverse resistance change between the amorphous and crystalline phases of CrGT. The N atom can form stronger bonds with Ge or Cr than Cr-Te, restraining the shift of Cr to the center of the octahedron to form the new Cr-Te bonds, resulting in a constant carrier density change during crystallization. The thermal stability and data retention properties also show an improvement by N doping.

  37. Microstructure and mechanical properties of low-temperature wrought-processed Mg–Y–Zn alloy containing LPSO phase

    Hidetoshi Somekawa, Daisuke Ando, Michiaki Yamasaki, Yoshihito Kawamura

    Materialia 12 2020年8月

    DOI: 10.1016/j.mtla.2020.100786  

    eISSN:2589-1529

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    The effect of process temperature on microstructure and mechanical properties was investigated using Mg–4at%Y–2at%Zn alloy produced by caliber rolling at temperatures of 373 K and 748 K. Caliber rolled bars were successfully fabricated with the introduction of deformation kink bands in the long periodic stacking ordered (LPSO) structure, regardless of rolling temperature. Microstructural observations showed that the alloy rolled at 748 K had the same microstructural features as previously reported wrought-processed magnesium alloys that contained the LPSO phase. In contrast, the alloy rolled at the lower temperature (373 K) had a high density of residual strains and deformation twins, as well as deformation kink bands. These microstructural features affected the mechanical properties; the alloy rolled at 373 K had higher properties of strength and hardness compared with those of the alloy produced at 748 K. However, the lower-temperature rolled alloy showed a decrease in compressibility, due to the existence of micro-cracks. Three-dimensional microstructural observation revealed that such defects were unlikely to be present in deformation kink bands and at the interface between kink bands and LPSO/α-Mg phases.

  38. Texture formation through thermomechanical treatment and its effect on superelasticity in Mg-Sc shape memory alloy

    Keisuke Yamagishi, Daisuke Ando, Yuji Sutou, Yukiko Ogawa

    Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals 84 (8) 253-259 2020年8月1日

    DOI: 10.2320/jinstmet.J2020010  

    ISSN:0021-4876

    詳細を見る 詳細を閉じる

    The formation of texture through thermomechanical treatment was investigated in Mg-18.8 at% Sc shape memory alloy to enhance its superelasticity at room temperature. The samples were cold rolled in an α phase or in a β phase and then finally heat treated at 690°c followed by water quenching to obtain a β phase. In the case of cold rolling in the α phase, a basal-plane texture was formed, while no preferential texture was observed along in-plane direction. After the final heat treatment, {011}<uvw>β transformation texture was obtained, according to Burgers relationship, indicating no improvement of the superelasticity along in-plane direction. In the case of the cold rolling in the β phase, a weak {111}<011>β recrystallization texture was obtained. The sample showed about 0.65% superelastic tensile strain along rolling direction, while that along transverse direction (//∼<113>β) showed only about 0.43%. This trend is in good agreement with the orientation dependence on the transformation strain, but, the obtained superelastic strain was much lower than the expected value, which is due to the weak texture and suggests the existence of a strong grain constraint in the Mg-Sc shape memory alloy.

  39. Microstructure and mechanical properties of caliber rolled Mg–Y–Zn alloys

    Hidetoshi Somekawa, Daisuke Ando

    Materials Science and Engineering A 780 2020年4月

    DOI: 10.1016/j.msea.2020.139144  

    ISSN:0921-5093

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    The microstructural evolution and mechanical properties were investigated using a caliber rolled Mg–5Y-2.5Zn (in at.%) alloy. Deformation kink bands could be induced by the caliber rolling process, which is the same as that of conventional wrought processed (extruded or rolled) Mg–Y–Zn alloys. The number of rolling passes was an influential factor for the microstructure, i.e., the bending angle of the long periodic stacking ordered (LPSO) phase associated with deformation kink bands. The mechanical properties of strength and hardness also depended on the number of rolling passes. These properties were improved with increased number of rolling passes (up to 6 passes). The yield strength and hardness before the rolling process were 260 MPa and ~90 Hv. On the other hands, after caliber rolling, these properties showed over 500 MPa and 129 Hv, respectively, for the alloy with 6 rolling passes. Microstructural observations revealed that such good properties resulted from the existence of deformation kink bands and dense dislocations induced by caliber rolling. Controlling the morphology of the LPSO phase associated with deformation kink bands was found to be an effective strategy; the bending angle of this phase of more than 20° is outstanding for further improving the mechanical properties.

  40. Liner- and barrier-free NiAl metallization: A perspective from TDDB reliability and interface status 査読有り

    Linghan Chen, Daisuke Ando, Yuji Sutou, Shinji Yokogawa, Junichi Koike

    Applied Surface Science 497 143810 2019年12月15日

    DOI: 10.1016/j.apsusc.2019.143810  

    ISSN:0169-4332

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    This study reports the time-dependent-dielectric-breakdown (TDDB) reliability of NiAl on SiO without any barrier layer. NiAl was indicated to exhibit superior TDDB reliability in comparison to Cu/TaN in the time-to-failure (4200 s versus 240 s, at 4 MV/cm at 200 °C) and in the breakdown activation energy under 4 MV/cm (1.17 eV versus 0.87 eV). Moreover, NiAl was found to form an atomically thin and self-limiting Al oxide layer at the NiAl/SiO interface, and this Al oxide layer, together with the large cohesive energy of NiAl, was considered to be possible origin for the excellent reliability. The results demonstrate a great potential of NiAl as a liner- and barrier-free interconnect material. 2 2

  41. Bidirectional Selector Utilizing Hybrid Diodes for PCRAM Applications

    Yi Shuang, Shogo Hatayama, Junseop An, Jinpyo Hong, Daisuke Ando, Yunheub Song, Yuji Sutou

    Scientific Reports 9 (1) 2019年12月1日

    DOI: 10.1038/s41598-019-56768-2  

    eISSN:2045-2322

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    Three-dimensional crossbar technology has been of great significance for realizing high density and multiple terabytes of data storage in memory devices. However, to further scale down the size of memory devices, a selector exhibiting nonlinear electrical properties should be in series with a memory layer in case of unwanted sneak current disturbance. Conventional selectors usually utilize a complicated multilayer structure to realize the high nonlinearity of current, which might be incompatible with certain manufacturing processes or limit the scalability of memory. Herein, we propose a simple heterojunction diode using an n-type oxide semiconductor, specifically, InGaZnO (IGZO), and a p-type phase change material (PCM), specifically, N-doped Cr Ge Te (NCrGT), to realize self-selective performance. The electrode/IGZO/NCrGT/plug-electrode structure with an IGZO/NCrGT pn diode and NCrGT/plug-electrode Schottky diode can realize bidirectional, self-selective phase change random access memory (PCRAM) for either amorphous or crystalline NCrGT. The approximate equilibrium energy band diagrams for the IGZO/NCrGT pn junction and the IGZO/NCrGT/W hybrid junction were proposed to explain the possible conduction mechanism. We demonstrated that hybrid diode-type PCM memory exhibits both selectivity and resistive switching characteristics. The present findings offer new insight into selector technology for PCM. 4 2 2 6

  42. Cr-Triggered Local Structural Change in Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf> Phase Change Material 査読有り

    Shogo Hatayama, Yi Shuang, Paul Fons, Yuta Saito, Alexander V. Kolobov, Keisuke Kobayashi, Satoshi Shindo, Daisuke Ando, Yuji Sutou

    ACS Applied Materials and Interfaces 11 (46) 43320-43329 2019年11月20日

    出版者・発行元:American Chemical Society ({ACS})

    DOI: 10.1021/acsami.9b11535  

    ISSN:1944-8244

    eISSN:1944-8252

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    Cr Ge Te (CrGT) is a phase change material with higher resistivity in the crystalline phase than in the amorphous phase. CrGT exhibits an ultralow operation energy for amorphization. In this study, the origin of the increased resistance in crystalline CrGT compared to amorphous CrGT and the underlying phase change mechanism were investigated in terms of both local structural change and associated change in electronic state. The density of states at the Fermi level in crystalline CrGT decreased with increasing annealing temperature and became negligible upon annealing at 380 °C. Simultaneously, the Fermi level shifted from the vicinity of the valence band to the band gap center, leading to an increase in resistance. The phase change from amorphous to crystalline CrGT occurred through a metastable crystalline phase with a local structure similar to that of the amorphous phase. Cr nanoclusters were confirmed to exist in both the amorphous and crystalline phases. The presence of Cr nanoclusters induced Cr vacancies in the crystalline phase. These Cr vacancies generated hole carriers, leading to p-type conduction. Photoelectron spectroscopy of the Cr 2s core level clearly indicated a decrease in the fraction of Cr-Cr bonds and an increase in the fraction of Cr-Te bonds in crystalline CrGT upon annealing. Meanwhile, the coordination number of the Cr nanoclusters decreased as the number of Cr-Cr bonds was reduced. Together, these results imply that the origin of the increased resistance in crystalline CrGT is the filling of Cr vacancies by Cr atoms diffusing from Cr nanoclusters. 2 2 6

  43. Ordering of the bcc Phase in a Mg-Sc Binary Alloy by Aging Treatment 査読有り

    Yukiko Ogawa, Yuji Sutou, Daisuke Ando, Junichi Koike, Hidetoshi Somekawa

    Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science 50 (7) 3044-3047 2019年7月15日

    DOI: 10.1007/s11661-019-05260-7  

    ISSN:1073-5623

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    In a Mg-Sc system, a bcc (β) phase exists in a high-temperature region, and the quenched β shows drastic age-hardening and shape-memory properties. In addition to the disordered β phase, the ordered β (B2) phase is reported to exist in a low-temperature region. We report that the quenched β phase can be ordered through aging treatment at 573 K. This finding indicates that the mechanical characteristics and shape-memory functionality of β-type Mg-Sc alloys can be controlled by ordering the β phase.

  44. Zn-Fe めっき層の組成および組織制御による改質に向けたスパッタリング成膜による検証 査読有り

    Uchiyama, A, Kawasaki, K, Sutou, Y, Ando, D, Koike, J

    鉄と鋼 105 (7) 724-732 2019年7月

  45. Relation between density and optical contrasts upon crystallization in Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf> phase-change material: Coexistence of a positive optical contrast and a negative density contrast 査読有り

    Shogo Hatayama, Daisuke Ando, Yuji Sutou

    Journal of Physics D: Applied Physics 52 (32) 325111 2019年6月13日

    DOI: 10.1088/1361-6463/ab233f  

    ISSN:0022-3727

    eISSN:1361-6463

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    In this study, the relation between density contrast and optical contrast for Cr Ge Te (CrGT) was studied. The CrGT showed negative density contrast between its as-deposited amorphous and crystalline phases. We confirmed that the CrGT satisfies the linear relation between the density contrast and optical contrast at wavelength of 630 nm, consistent with the behaviors of reported phase-change materials (PCMs). In CrGT films annealed at temperatures below 350 °C, the films exhibited a negative density contrast and negative optical contrast at 630 nm, consistent with the Clausius-Mossotti relationship. However, the 380 °C-annealed film showed a positive optical contrast at 630 nm due to a drastic increase in reflectance even with the negative density contrast. The absorption coefficient measurements as a function of wavelength indicated that there is no electron delocalization in the crystalline CrGT phase. It was found that the crystalline CrGT exhibited a drastic increase in the refractive index upon annealing at 380 °C at a wavelength range of visible light, causing an increase in the reflectance. Similar behavior was also observed in ultraviolet (330 nm) and infrared light (1000 nm) ranges. Such a large difference in refractive index in a wide wavelength range covering from ultraviolet to infrared light ranges introduces the possibility to realize the CrGT-based metasurface. 2 2 6

  46. CuAl<inf>2</inf> thin films as a low-resistivity interconnect material for advanced semiconductor devices 査読有り

    Linghan Chen, Daisuke Ando, Yuji Sutou, Junichi Koike

    Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics 37 (3) 031215 2019年5月1日

    DOI: 10.1116/1.5094404  

    ISSN:2166-2746

    eISSN:2166-2754

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    New interconnect materials that have a low line resistivity are required to address issues associated with the increased resistivity due to the aggressive downscaling of future semiconductor devices. In this work, CuAl thin films are investigated as a potential material for liner- and barrier-free interconnect applications. The results show that CuAl blanket films adhere well to and do not undergo interdiffusion with SiO , as well as having a favorable size effect of resistivity. Furthermore, the filling of CuAl in narrow low-k trenches is investigated, and an excellent gap-filling performance is registered. These features suggest that CuAl is a promising alternative to Cu that does not require any additional liner or barrier layers for feature sizes less than 10 nm. 2 2 2 2 2

  47. Electrical transport mechanism of the amorphous phase in Cr <inf>2</inf> Ge <inf>2</inf> Te <inf>6</inf> phase change material 査読有り

    Shogo Hatayama, Yuji Sutou, Daisuke Ando, Junichi Koike, Keisuke Kobayashi

    Journal of Physics D: Applied Physics 52 (10) 105103 2019年1月9日

    DOI: 10.1088/1361-6463/aafa94  

    ISSN:0022-3727

    eISSN:1361-6463

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    A Cr Ge Te (CrGT) phase change material (PCM) was studied. Different from conventional PCMs, it shows an inverse resistance change between a low-resistance amorphous phase and a high-resistance crystalline phase. Moreover, the anomalous low resistivity in the amorphous CrGT is considered to be due to a large carrier density, but the mechanism of electrical transport is still not clear. In this study, the electrical transport mechanism of the amorphous CrGT was discussed based on the temperature dependence of the resistivity, carrier density, mobility, and current-voltage characteristics. Above 300 K, the conduction mechanism of the amorphous CrGT was thermally activated band conduction, which is different from the conventional Ge-Sb-Te PCMs that show Poole-Frenkel conduction in the amorphous phase. Below 300 K, the amorphous CrGT shows hopping conduction, changing from variable range hopping (Mott VRH) to Efros-Shklovskii variable range hopping (ES-VRH) with decreasing temperature. The crossover from Mott VRH to ES-VRH was observed at around 200 K. Furthermore, the Fermi level was not pinned at the center of bandgap; instead, it was located near the valence band. 2 2 6

  48. Improvement of powdering resistance of Zn-Fe galvannealed coating by controlling of its composition and microstructure: Verification with sputtering method

    Aimi Uchiyama, Kohei Kawasaki, Yuji Sutou, Daisuke Ando, Junichi Koike

    Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan 105 (7) 724-732 2019年

    DOI: 10.2355/tetsutohagane.TETSU-2018-164  

    ISSN:0021-1575

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    Improvement of the powdering resistance of galvannealed (GA) coatings is a key issue in automotive GA steel sheets. To make the relationship between powdering resistance and microstructure of GA layer, sputtering fabrication process was used to prepare Zn-Fe intermetallic films with various composition and microstructure in this study. Zn-Fe films with 1500 nm in thickness were deposited on an iron substrate by RF magnetron sputtering. Г+Г two-phase film (17.2~24.4 at.%Fe) was found to show a severe powdering by 3-point bending test, while Г (16.2 at.%Fe) or Г (34.3 at.%Fe) single-phase films showed much better powdering resistance. These results indicate that Г/Г interfaces boundaries have a low interfacial strength compared to that of Г/iron or Г /iron interfaces. To improve the low powdering resistance of the Г+Г two-phase film, we investigated the effect of grain size refinement by B addition on the powdering resistance. It was found that the grain size refinement by B addition drastically improves the powdering resistance of Г+Г two-phase film. The decrease in the fracture toughness of Г+Г two-phase film by grain refinement was suggested to cause the improvement of its powdering resistance. 1 1 1 1 1 1 1

  49. NiAl as a potential material for liner- and barrier-free interconnect in ultrasmall technology node

    Linghan Chen, Daisuke Ando, Yuji Sutou, Daniel Gall, Junichi Koike

    Applied Physics Letters 113 (18) 2018年10月29日

    DOI: 10.1063/1.5049620  

    ISSN:0003-6951

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    Because of aggressive downscaling of the dimensions of future semiconductor devices, they will suffer from increased line resistivity and resistance-capacitance delay. In this work, NiAl thin films are investigated as a potential liner- and barrier-free interconnect material. The results show that NiAl has strong adhesion, does not undergo interdiffusion with SiO , and has a favorable resistivity size effect. These features suggest that NiAl is a good candidate for replacing Cu as a liner- and barrier-free interconnect for linewidths below 7 nm. 2

  50. Crystallization mechanism and kinetics of Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf> phase change material

    S. Hatayama, Y. Sutou, D. Ando, J. Koike

    MRS Communications 8 (3) 1167-1172 2018年9月1日

    DOI: 10.1557/mrc.2018.176  

    ISSN:2159-6859

    eISSN:2159-6867

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    The crystallization mechanism and kinetics of Cr Ge Te (CrGT) films were investigated by differential scanning calorimetry. The average Avrami exponent (na) analysis indicated that CrGT exhibits a growth-dominant crystallization in the range of heating rate (β) of 10-50°C/min. In comparison, Ge Sb Te (GST) showed a nucleation-dominant crystallization. The na of CrGT was about 3, and was majorly independent of β. The n of GST decreased with an increasing β, which asymptotically approached a value of around 3. The kinetic constant of CrGT was evaluated to be almost the same with that of GST, indicating that CrGT undergoes fast crystallization. 2 2 6 2 2 5 a

  51. New Contact Metallization Scheme for FinFET and beyond

    Junichi Koike, Maryamsadat Hosseini, Daisuke Ando, Yuji Sutou

    2018 IEEE Electron Devices Technology and Manufacturing Conference, EDTM 2018 - Proceedings 169-171 2018年7月26日

    DOI: 10.1109/EDTM.2018.8421448  

    詳細を見る 詳細を閉じる

    A new metallization scheme of Co/CoTi alloy is proposed to replace conventional W contact plug and TiN/Ti barrier so as to alleviate increasing parasitic resistance of MOL with device scaling in sub-10 nm node. Annealing of the CoTi alloy layer led to the formation of epitaxial Co silicide and TiO at the Co/Si interface. With this interface structure, a low contact resistivity of 10-9 Ω cm2 was obtained on highly doped n-Si. x x x

  52. Aging precipitation kinetics of Mg-Sc alloy with bcc+hcp two-phase

    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

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    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 . 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. −1

  53. Understanding the fast phase-change mechanism of tetrahedrally bonded Cu2GeTe3: Comprehensive analyses of electronic structure and transport phenomena

    Keisuke Kobayashi, Jonathan M. Skelton, Yuta Saito, Satoshi Shindo, Masaaki Kobata, Paul Fons, Alexander V. Kolobov, Stephen Elliott, Daisuke Ando, Yuji Sutou

    Physical Review B 97 (19) 2018年5月3日

    DOI: 10.1103/PhysRevB.97.195105  

    ISSN:2469-9950

    eISSN:2469-9969

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    Cu2GeTe3 (CGT) phase-change material, a promising candidate for advanced fast nonvolatile random-access-memory devices, has a chalcopyritelike structure with sp3 bonding in the crystalline phase; thus, the phase-change (PC) mechanism is considered to be essentially different from that of the standard PC materials (e.g., Ge-Sb-Te) with threefold to sixfold p-like bonding. In order to reveal the PC mechanism of CGT, the electronic structure change due to PC has been investigated by laboratory hard x-ray photoelectron spectroscopy and combined first-principles density-functional theory molecular-dynamics simulations. The valence-band spectra, in both crystalline and amorphous phases, are well simulated by the calculations. An inherent tendency of Te 5s lone-pair formation and an enhanced participation of Cu 3d orbitals in the bonding are found to play dominant roles in the PC mechanism. The electrical conductivity of as-deposited films and its change during the PC process is investigated in connection with valence-band spectral changes near the Fermi level. The results are successfully analyzed, based on a model proposed by Davis and Mott for chalcogenide amorphous semiconductors. The results suggest that robustness of the defect-band states against thermal stress is a key to the practical application of this material for memory devices.

  54. Co and CoTi<inf>x</inf> for contact plug and barrier layer in integrated circuits

    Maryamsadat Hosseini, Daisuke Ando, Yuji Sutou, Junichi Koike

    Microelectronic Engineering 189 78-84 2018年4月

    出版者・発行元:Elsevier B.V.

    DOI: 10.1016/j.mee.2017.12.017  

    ISSN:0167-9317

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    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/CoTi to replace conventional contact plug/barrier materials of W/TiN/Ti. Co and CoTi amorphous alloy layers were deposited on SiO /p-Si. The 3 nm-thick amorphous CoTi layer promoted adhesion between Co and SiO . The resistivity of the 150 nm-thick Co film on CoTi showed low film resistivity close to bulk Co value both in as-deposited and annealed conditions. The amorphous structure of the CoTi layer was maintained throughout annealing up to 500 °C. Capacitance-voltage measurement of Co/CoTi /SiO /p-Si samples showed a good diffusion barrier property of the CoTi layer between Co and SiO after thermal stress as well as bias thermal stress. The obtained results indicated that Co/CoTi can be good candidate materials for contact plug and diffusion barrier in advanced integrated circuits. x x 2 x 2 x x x 2 x 2 x

  55. Contact resistance change memory using N-doped Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf> phase-change material showing non-bulk resistance change

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

    Applied Physics Letters 112 (18) 2018年4月

    出版者・発行元:American Institute of Physics Inc.

    DOI: 10.1063/1.5029327  

    ISSN:0003-6951

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    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 Cr Ge Te (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. 2 2 6

  56. Martensitic Transformation in a β-Type Mg–Sc Alloy 査読有り

    Yukiko Ogawa, Daisuke Ando, Yuji Sutou, Hidetoshi Somekawa, Junichi Koike

    Shape Memory and Superelasticity 4 (1) 167-173 2018年3月1日

    DOI: 10.1007/s40830-017-0143-y  

    ISSN:2199-384X

    eISSN:2199-3858

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    Recently, we found that a Mg–Sc alloy with a bcc (β) phase exhibits superelasticity and a shape memory effect at low temperature. In this work, we examined the stress-induced and thermally induced martensitic transformation of the β-type Mg–Sc alloy and investigated the crystal structure of the thermally induced martensite phase based on in situ X-ray diffraction (XRD) measurements. The lattice constants of the martensite phase were calculated to be a = 0.3285 nm, b = 0.5544 nm, and c = 0.5223 nm when we assumed that the martensite phase has an orthorhombic structure (Cmcm). Based on the lattice correspondence between a bcc and an orthorhombic structures such as that in the case of β-Ti shape memory alloys, we estimated the transformation strain of the β Mg–Sc alloy. As a result, the transformation strains along the 001, 011, and 111 directions in the β phase were calculated to be + 5.7, + 8.8, and + 3.3%, respectively.

  57. Inverse Resistance Change Cr<inf>2</inf>Ge<inf>2</inf>Te<inf>6</inf>-Based PCRAM Enabling Ultralow-Energy Amorphization

    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

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    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 Cr Ge Te (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 Ge Sb Te 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. 2 2 6 2 2 5

  58. Material innovation for MOL, BEOL, and 3D integration

    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

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    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 Ωcm on both n+ and p+ Si. For BEOL, a CVD-MnO layer could be formed conformally in high-aspect ratio contact holes. The ALD-MnO 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. -9 2 x x

  59. Optical and electrical properties of ¡-MnTe thin films deposited using RF magnetron sputtering

    Materials Transactions 59 (9) 1506-1512 2018年

    DOI: 10.2320/matertrans.M2018086  

    ISSN:1345-9678

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    © 2018 The Japan Institute of Metals and Materials. The optical and electrical properties of MnTe films were investigated to ascertain the feasibility of their use in solar cell applications. Three ¡-MnTe thin films with different composition, i.e., Mn-47.9 at% Te, Mn-49.2 at% Te, and Mn-50.4 at% Te, were prepared using RF magnetron sputtering. All the films demonstrated a high light absorption coefficient (0.2 © 1050.8 © 106 cm11) and an optimal indirect band gap (1.371.52 eV) for solar cell applications. Furthermore, all of them exhibited p-type conductivity, with the Mn-47.9 at% Te film demonstrating three to four times higher carrier mobility (5.2cm2·V11·s11) than the Mn-50.4at% Te film (1.6cm2·V11·s11).

  60. Feasibility study of Cu paste printing technique to fill deep via holes for low cost 3D TSV applications

    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  

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    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].

  61. Enhanced fatigue properties of cast AZ80 Mg alloy processed by cyclic torsion and low-temperature annealing

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

    Materials Science and Engineering A 696 52-59 2017年6月1日

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/j.msea.2017.04.061  

    ISSN:0921-5093

    eISSN:1873-4936

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    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.

  62. Texture randomization of hexagonal close packed phase through hexagonal close packed/body centered cubic phase transformation in Mg-Sc alloy

    Yukiko Ogawa, Daisuke Ando, Yuji Sutou, Junichi Koike

    Scripta Materialia 128 27-31 2017年2月1日

    出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.scriptamat.2016.09.024  

    ISSN:1359-6462

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    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.

  63. Cr-Mo-N被膜の硬度および摩擦摩耗特性に及ぼすCu添加の影響

    鈴木 優太, 須藤 祐司, 安藤 大輔, 小池 淳一

    日本金属学会誌 81 (5) 270-275 2017年

    出版者・発行元:公益社団法人 日本金属学会

    DOI: 10.2320/jinstmet.JBW201613  

    ISSN:0021-4876

    eISSN:1880-6880

  64. Effect of initial microstructure on stress-strain behavior in Mg-Sc-Zn based alloy with high Sc content

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

    Nippon Kinzoku Gakkaishi/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

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    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°C into a sheet. The rolled sheets were finally annealed at 500 (designated as a-type) and 680°C (designated as α + β-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°C, respectively. The ultimate tensile strength (UTS) and elongation of the α(hcp)-type sample were 280 MPa and 20.5%, respectively, while those of α(hcp) + β(bcc)-type sample were 373 MPa and 5.9%, respectively. It was found that c/a ratio of α-type sample was small indicating that non-basal slip systems were activated during tensile test. On the other hand, it was suggested that, in β phase, the stress induced phase transformation from bcc to hcp occurred during tensile test which causes higher strength and lower elongation.

  65. Stress-strain hysteresis and strain hardening during cyclic tensile test of Mg-0.6at%Y alloy

    Qinghuan Huo, Daisuke Ando, Yuji Sutou, Junichi Koike

    Materials Science and Engineering A 678 235-242 2016年12月15日

    出版者・発行元:ELSEVIER SCIENCE SA

    DOI: 10.1016/j.msea.2016.10.008  

    ISSN:0921-5093

    eISSN:1873-4936

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    The Mg-0.6at%Y alloy having an average grain size of 180 µm and random texture was subjected to cyclic tensile tests at room temperature. Tensile tests were performed at a strain rate of 1×10  s 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 {101̅2} 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. −3 −1

  66. Erratum to “Determination of ɑ/β phase boundaries and mechanical characterization of Mg-Sc binary alloys” [Mater. Sci. Eng. A 670 (2016) 335–341]

    Materials Science and Engineering A 674 713 2016年9月30日

    出版者・発行元:None

    DOI: 10.1016/j.msea.2016.08.016  

    ISSN:0921-5093

    詳細を見る 詳細を閉じる

    © 2016 The publisher regrets that some of the Author&#039;s requested amendments were not applied. These were as follows: • On page 135, Introduction, the sentence in the second column should read as follows: Meanwhile, there are a few reports on mechanical properties of Sc-added Mg alloys with single α phase [11–13]. Very recently, the present authors have found that Mg-Sc alloy with a β phase shows significant age hardening due to the formation of very fine α precipitates in β matrix [14].• On page 136, Section 2, the sentence should read as follows: The obtained diffusion couples were annealed at 773, 823 and 873 K for 96, 72 and 72 h, respectively, in an Ar atmosphere.• On page 136, Section 2, the sentence should read as follows: The Mg-20 at% Sc alloy ingot melted in a high frequency induction furnace was hot rolled at 873 K and then cold rolled until a thickness of about 0.7 mm with annealing at 873 K.• Table 1 show appears as follows: • Page 340, Section 3.3, the sentence should read as follows: Therefore, the specific strength is also higher than the conventional high strength alloys, such as AZ91, ZK60, etc. [10].The publisher would like to apologise for any inconvenience caused.

  67. 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

    Mater. Sci. Eng. A 670 335-341 2016年7月18日

    出版者・発行元:None

    DOI: 10.1016/j.msea.2016.06.028  

    ISSN:0921-5093

    eISSN:1873-4936

  68. 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

    Nippon Kinzoku Gakkaishi/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.

  69. 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

    出版者・発行元:JAPAN INST METALS

    DOI: 10.2320/matertrans.M2015383  

    ISSN:1345-9678

    eISSN:1347-5320

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    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 (06.0 ccm) gases using Ti Mo C 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 (fN ) and reached to a minimum hardness of 16.4 GPa at fN = 2:0 ccm. Contrarily, at over fN = 3:0 ccm, the hardness drastically increased with increasing fN and reached a maximal value of 32 GPa, and then slightly decreased again with further increase of fN 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 fN and the film deposited at fN = 5:0 ccm showed a minimum value of 0.27. The simple oxidation test in air indicated that lubricious MoO is easy to be formed in the film deposited at a high fN , which should cause the reduction of friction coefficient. 25 25 50 2 2 2 2 2 2 2 3 2

  70. Aging effect of Mg-Sc alloy with α+β two-phase microstructure 査読有り

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

    Mater. Trans. 57 (7) 1119-1123 2016年

    出版者・発行元:None

    DOI: 10.2320/matertrans.M2016093  

    ISSN:1345-9678

    eISSN:1347-5320

  71. Age-hardening of dual phase Mg-Sc alloy at 573 K 査読有り

    Yukiko Ogawa, Daisuke Ando, Yuji Sutou, Junichi Koike

    Magnesium Technology 2016-January 147-149 2016年

    DOI: 10.1002/9781119274803.ch29  

    ISSN:1545-4150

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    In this study, we investigated the effect of aging treatment at 573 K on hardness in Mg-Sc alloy with bcc/hcp dual phase prepared by annealing at 873 K. It was found that hardness abruptly increased after some incubation time, and then reached steady state level. Moreover, by further aging, the hardness increased again. It was confirmed by SEM observation and XRD that the initial drastic hardening was due to the precipitation of α phase. Furthermore, XRD results suggested that the secondary hardening was attributed to the formation of MgSc phase with ordered B2 structure.

  72. Study on fatigue mechanism of Mg-0.6at%Y alloy by cyclic tensile test 査読有り

    Qinghuan Huo, Daisuke Ando, Junichi Koike, Yuji Sutou

    Magnesium Technology 2016-January 299-303 2016年

    DOI: 10.1002/9781119274803.ch58  

    ISSN:1545-4150

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    In this investigation, the fatigue mechanisms of Mg-0.6at%Y dilute alloy were studied by cyclic tensile tests. After annealing at 723 K for 8 h, average grain size of 180 pm was obtained. Yield stress and ultimate tensile strength were 65 and 140 MPa, respectively. Cyclic tensile tests were carried out at room temperature for 10 cycles. Stress was continuously cycled from nil to peak value and subsequently unloading back to nil. Peak stress was controlled according to yield stress: below yield stress, near yield stress and above yield stress. The results showed that basal slip and prismatic slip are the main fatigue mechanisms of Mg-Y alloy. {10-12} tension twinning only occurs when peak stress is above yield stress. Furthermore, compared with previous work on AZ31 Mg alloy, prismatic dislocation slip promotes cyclic strain hardening more obvious than {10-12} tension twinning does.

  73. 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 80 (3) 171-175 2016年

    出版者・発行元:None

    DOI: 10.2320/jinstmet.JBW201511  

    ISSN:0021-4876

    eISSN:1880-6880

  74. 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 and Coatings Technology 280 1-7 2015年10月25日

    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 , on SUS304 stainless steel were investigated. The hardness, H, of the film increased with increasing f in a low f region (f ≤0.05sccm) and reached a maximum value of about 32GPa because of grain refinement. With further increasing f , 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 . 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 =0.2sccm 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 =0.2sccm with a crystalline/amorphous mixed structure showed the lowest μ in the present study and exhibited less frequent transverse cracking introduced by wear, as compared with that deposited at f =0.02sccm 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 μ and good wear resistance on the stainless steel substrate. O2 O2 O2 O2 O2 O2 O2 O2 O2

  75. 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

    Saito, Y, Sumiya, M, Sutou, Y, Ando, D, Koike, J

    AIP Adv. 5 (9) 097151 2015年9月1日

    DOI: 10.1063/1.4931392  

    ISSN:2158-3226

    eISSN:2158-3226

  76. Mg-Y合金圧延材の再結晶過程と集合組織変化 査読有り

    鈴木哲, 安藤大輔, 須藤祐司, 小池淳一

    軽金属 67 (7) 259-262 2015年7月

    出版者・発行元:一般社団法人 軽金属学会

    DOI: 10.2464/jilm.65.259  

    ISSN:0451-5994

    eISSN:1880-8018

  77. 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

    Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals 79 (4) 220-226 2015年4月

    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 Ti<inf>25</inf>Mo<inf>25</inf>C<inf>50</inf> 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 (/n2) and reached to a minimum hardness of 16.4 GPa at fN<inf>2</inf>=2.0 ccm. Contrarily, at overf N<inf>2</inf>=3;0 ccm, the hardness drastically increased with increasingf N<inf>2</inf> and reached a maximal value of 32 GPa, and then slightly decreased again with further increase of fn<inf>2</inf>. 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 fn<inf>2</inf> and the film deposited at fN<inf>2</inf>=5.0 ccm showed a minimum value of 0.27. The simple oxidation test in air indicated that lubricious M0O<inf>3</inf> is easy to be formed in the film deposited at a high/N<inf>2</inf>, which should cause the reduction of friction coefficient.

  78. Precipitation hardening in Ti-Mo-N coating deposited by reactive sputtering 査読有り

    Yuji Sutou, Shoko Komiyama, Katsunari Oikawa, Daisuke Ando, Junichi Koike

    PTM 2015 - Proceedings of the International Conference on Solid-Solid Phase Transformations in Inorganic Materials 2015 417-418 2015年

    詳細を見る 詳細を閉じる

    The effect of heat treatment on the hardness of sputtered Ti-Mo-N film were investigated. We found that Ti Mo N film showed little hardness change by heat treatment, while Ti Mo28N film showed a drastic increase of hardness (28 GPa → 35 GPa) by heat treatment at around 1000°C. Such a hardness increase was caused by the precipitation of a bcc phase in a S-matrix. 42 11 47 34 38

  79. Mg–Y合金圧延材の再結晶過程と集合組織変化 査読有り

    鈴木 哲, 安藤 大輔, 須藤 祐司, 小池 淳一

    軽金属 65 (7) 259-262 2015年

    出版者・発行元:一般社団法人 軽金属学会

    DOI: 10.2464/jilm.65.259  

    ISSN:0451-5994

    eISSN:1880-8018

  80. Significant age hardening response of BCC/HCP dual phase Mg-Sc alloys 査読有り

    Daisuke Ando, Yukiko Ogawa, Yuji Sutou, Junichi Koike

    PTM 2015 - Proceedings of the International Conference on Solid-Solid Phase Transformations in Inorganic Materials 2015 1207-1208 2015年

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    Mg alloys have poor ductility due to their hcp structure. Thus, a novel Mg-Sc alloys with hcp+bcc (a+ß) dual phase is proposed in this study. The age-hardening behavior in solution treated Mg-16.8at.%Sc alloy with single ß phase was investigated and a very high hardness of over 230 Hv was obtained by aging treatment at 473 K for 2.4 ks. Such a significant age hardening response was caused by the formation of a very fine α phase in the ß matrix phase.

  81. Determination of HCP/BCC boundaries and mechanical properties of dual phase alloy in binary Mg-Sc system 査読有り

    Yukiko Ogawa, Daisuke Ando, Yuji Sutou, Junichi Koike

    PTM 2015 - Proceedings of the International Conference on Solid-Solid Phase Transformations in Inorganic Materials 2015 419-420 2015年

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    We proposed a novel Mg-Sc alloy with hcp+bcc dual phase. It is necessary to determine the Sc composition of hcp/bcc phase boundaries to control the dual phase microstructure. Thus, in this work, the Mg-Sc binary phase diagram was reconsidered using a conventional equilibrated alloy method. It was found from the obtained results that the hcp/bcc phase boundaries shifted towards a lower Sc content than those of previous reports. Mg-16.8 at% Sc alloy had a single bcc phase after annealing at 923K followed by quenching. The Mg-16.8 at% Sc alloy annealed at 923K followed by cooling at a rate of 20 K/min showed hcp+bcc dual phase and exhibited high strength and better ductility.

  82. Resistive Switching Behavior in Undoped α-Fe<sub>2</sub>O<sub>3</sub> Film with a Low Resistivity

    Yukiko Ogawa, Yuji Sutou, Daisuke Ando, Junichi Koike

    Advances in Science and Technology 95 96-99 2014年10月

    出版者・発行元:Trans Tech Publications, Ltd.

    DOI: 10.4028/www.scientific.net/ast.95.96  

    ISSN:1662-0356

    詳細を見る 詳細を閉じる

    <jats:p>The resistive switching behavior of a low resistive p-type α-Fe<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> thin film sandwiched between Fe bottom electrode and top electrodes of various materials (Fe, Ni and TiN) was studied by current-voltage measurements. When TiN was used for top electrode of memory cell, the reversible resistive switching behavior was observed for over 100 cycles. From impedance measurement, it was suggested that the resistive switching behavior in the TiN/p-type α-Fe<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/Fe device is attributed to the change of the contact resistance in the interface between TiN and α-Fe<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> layers.</jats:p>

  83. 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 SPEC. ISSUE 2) 05GA10 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 °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 . The metallic Mn layer enhanced the adhesion and wettability of Cu on the BD-III substrates. © 2014 The Japan Society of Applied Physics. -1

  84. Formation behavior and adhesion property of metallic Mn layer on porous SiOC by chemical vapor deposition 査読有り

    安藤 大輔, 須藤 祐司

    Japanese Journal of Applied Physics 53 (5) 05GA10 2014年5月

    出版者・発行元:None

    DOI: 10.7567/JJAP.53.05GA10  

    ISSN:0021-4922

    eISSN:1347-4065

  85. Reflow behavior of Cu-Mn in LSI line patterns 査読有り

    安藤 大輔, 須藤 祐司

    Japanese Journal of Applied Physics 53 (5 SPEC. ISSUE 2) 05GA09 2014年5月

    出版者・発行元:None

    DOI: 10.7567/JJAP.53.05GA09  

    ISSN:0021-4922

    eISSN:1347-4065

  86. Effects of O2 and N2 flow rate on the electrical properties of Fe-O-N films 査読有り

    安藤 大輔

    Materials Transactions 55 (10) 1606-1610 2014年

    出版者・発行元:None

    DOI: 10.2320/matertrans.M2014089  

    ISSN:1345-9678

    eISSN:1347-5320

  87. New model for low-temperature oxidation of copper single crystal 査読有り

    Kensuke Fujita, Daisuke Ando, Masahito Uchikoshi, Kouji Mimura, Minoru Isshiki

    Applied Surface Science 276 347-358 2013年7月1日

    出版者・発行元:ELSEVIER SCIENCE BV

    DOI: 10.1016/j.apsusc.2013.03.096  

    ISSN:0169-4332

    詳細を見る 詳細を閉じる

    Low-temperature oxidation of a copper single crystal, Cu(1 1 1), was investigated using an in situ spectroscopic ellipsometer. The oxidation rate followed the cubic rate law at 5-25 nm oxide thickness; thus, the rate law of Cu single crystal oxidation depended on Cu oxide thickness. Furthermore, the activation energy was found to be close to that of grain boundary diffusion of metal ions in the oxide layer. These results could be explained by grain boundary diffusion and oxide grain growth. Thus, we verified that the low-temperature oxidation kinetics of copper depend on oxide grain growth. © 2013 Elsevier B.V. All rights reserved.

  88. The electrical and optical properties of feon 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

    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 FeON films were investigated in order to find their possibilities for solar cell application. FeON thin films were deposited on glass substrates by RF magnetron sputtering using an ArN2O reactive gas. Under optimum flow rates of nitrogen and oxygen, the FeON 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 hematitemagnetite mixed phase, and the introduction of oxygen vacancies and/or nitrogen interstitials. ©2013 The Japan Society for Technology of Plasticity. 2

  89. 結晶塑性有限要素法を用いた圧延集合組織を有するマグネシウム合金の変形・強度発現機構の解明 査読有り

    石田智広, 渋谷慎兵, 加藤準治, 寺田賢二郎, 京谷孝史, 安藤大輔, 小池淳一

    日本機械学会論文集A編 79 (808) 1840-1851 2013年

    出版者・発行元:None

    DOI: 10.1299/kikaia.79.1840  

    ISSN:0387-5008

  90. 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.

  91. A new constitutive model for crystal plasticity with deformation twinning 査読有り

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

    Transactions of JSCES 20120014 2012年9月

  92. 六方晶金属の結晶塑性・変形双晶構成モデル 査読有り

    石田 智広, 渋谷 慎兵, 加藤 準治, 寺田 賢二郎, 京谷 孝史, 安藤 大輔, 小池 淳一

    計算工学会論文集 2012 P20120014 2012年

  93. 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

    Materials Science Forum 717-720 829-832 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

    eISSN:1662-9752

    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 °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. © (2012) Trans Tech Publications.

  94. A new constitutive model for crystal plasticity with deformation twinning

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

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

    eISSN:1347-8826

    詳細を見る 詳細を閉じる

    A thermodynamics-based constitutive model, which accounts for both crystallographic slip and deformation twinning, is developed for a single crystal of hcp metals within the framework of finite crystal plasticity. While the volume fractions of stress-free twin deformations are introduced as internal variables, the free-energy involves the bulk energy of separate phases and the surface energy at twin interfaces, which are introduced as functions of the internal variables, in addition to the standard hardening-related energy in crystal plasticity framework. After the formulation is described in detail, a series of numerical examples is presented to verify the performance of the proposed model in predicting the deformation twinning, the successive deformation process and the twinning-induced stress responses. The results are studied with reference to the theoretical consequences and the experimental results reported in the literature. © 2012 by the Japan Society for Computational Engineering and Science.

  95. The Relationship between Grain boundary sliding and Grain Orientation in AZ31 Magnesium Alloys at Room Temperature 査読有り

    D. Ando, Y. Sutou, J. Koike

    TMS Magnesium Technology 2010 245-247 2010年3月

  96. 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 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 app.ears to be a major cause for the slip-induced grain boundary sliding.

  97. MICROSTRUCTURAL INVESTIGATION OF TWINS UNDER THE FRACTURE SURFACE IN AZ31 MAGNESIUM ALLOYS 査読有り

    D. Ando, J. Koike

    MAGNESIUM TECHNOLOGY 2009 537-540 2009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

    The present work was aimed at understanding the fracture behavior and mechanism of magnesium alloys. AZ31 magnesium alloys were deformed to failure by tensile loading at room temperature. The underlying microstructure of the fracture surface was investigated with a focused ion beam (FIB) microscope and a transmission electron microscope (TEM). The microscopic feature of the fracture surface could be classified by its morphology into three types: (1) dimples, (2) elliptic facets, and (3) severely sheared dimples. Observation of the substructure with TEM indicated the presence of {10-12} twins under the elliptic facets and the presence of {10-11}-{10-12} double twins under the severely sheared dimples. These results suggest that the localized shear deformation in the double twin become a crack initiation site. Failure occurs by the propagation of the crack along the interface of the {10-12} twins to form the elliptic faces and within grains to form the dimple feature.

  98. The Role of Deformation Twin during Fracture Behavior in AZ31 査読有り

    D. Ando, J. Koike

    Magnesium, 8th International Conference on Magnesium Alloys their Applications 8 8 538-543 2009年

  99. Microstructural investigation of twins under the fracture surface in AZ31 magnesium alloys 査読有り

    D. Ando, J. Koike

    TMS Annual Meeting 537-540 2009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

    The present work was aimed at understanding the fracture behavior and mechanism of magnesium alloys. AZ31 magnesium alloys were deformed to failure by tensile loading at room temperature. The underlying microstructure of the fracture surface was investigated with a focused ion beam (FIB) microscope and a transmission electron microscope (TEM). The microscopic feature of the fracture surface could be classified by its morphology into three types: (1) dimples, (2) elliptic facets, and (3) severely sheared dimples. Observation of the substructure with TEM indicated the presence of {10-12} twins under the elliptic facets and the presence of {10-11}-{10-12} double twins under the severely sheared dimples. These results suggest that the localized shear deformation in the double twin become a crack initiation site. Failure occurs by the propagation of the crack along the interface of the {10-12} twins to form the elliptic faces and within grains to form the dimple feature.

  100. Origin of the anomalous {101̄2} twinning during tensile deformation of mg alloy sheet 査読有り

    J. Koike, Y. Sato, D. Ando

    Materials Transactions 49 (12) 2792-2800 2008年12月

    出版者・発行元:JAPAN INST METALS

    DOI: 10.2320/matertrans.MRA2008283  

    ISSN:1345-9678

    eISSN:1347-5320

    詳細を見る 詳細を閉じる

    In order to understand the origin of the anomalous twinning of the {101̄2} type, rolled sheets of AZ31 Mg alloy were deformed at room temperature in tension along the rolling direction. An excellent correlation was found between {101̄2} twinning tendency and basal dislocation slip activity. Calculation of strain tensor indicated that the diagonal strain components associated with the localized basal slip can be canceled completely by the {101̄2} twinning. The results led to the conclusion that anomalous {101̄2} twins were formed to accommodate the strain incompatibility caused by localized basal dislocation slip. © 2008 The Japan Institute of Metals.

  101. 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:公益社団法人 日本金属学会

    DOI: 10.2320/jinstmet.71.684  

    ISSN:0021-4876

    eISSN:1880-6880

︎全件表示 ︎最初の5件までを表示

MISC 32

  1. Cu微粒子の低温酸化焼結挙動

    竹内 喬亮, 安藤 大輔, 小池 淳一, 須藤 祐司

    日本金属学会誌 86 (11) 224-231 2022年11月1日

    出版者・発行元:公益社団法人 日本金属学会

    DOI: 10.2320/jinstmet.j2022020  

    ISSN:0021-4876

    eISSN:1880-6880 2433-7501

  2. 合金化亜鉛めっき層のパウダリング耐性改善に向けたスパッタリング成膜による検証

    薗部駿太, 安藤大輔, 須藤祐司, 栗田大樹, 成田史生

    材料とプロセス(CD-ROM) 35 (2) 2022年

    ISSN:1882-8922

  3. ウルツ鉱型MnTe薄膜における電気伝導機構

    金美賢, 森竣祐, 双逸, 畑山祥吾, 安藤大輔, 須藤祐司

    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 82nd 2021年

    ISSN:2436-7613

  4. p-MnTe/n-AZO積層構造素子のメモリ動作性

    金 美賢, 森 竣祐, 安藤 大輔, 須藤 祐司

    応用物理学会学術講演会講演予稿集 2020.2 2176-2176 2020年8月26日

    出版者・発行元:公益社団法人 応用物理学会

    DOI: 10.11470/jsapmeeting.2020.2.0_2176  

    eISSN:2436-7613

  5. MnTe/Oxide積層構造にけるダイオード特性及びその応用可能性

    金 美賢, 森 竣祐, 安藤 大輔, 須藤 祐司

    応用物理学会学術講演会講演予稿集 2020.1 3229-3229 2020年2月28日

    出版者・発行元:公益社団法人 応用物理学会

    DOI: 10.11470/jsapmeeting.2020.1.0_3229  

    eISSN:2436-7613

  6. 不揮発性メモリ用Cr<sub>2</sub>Ge<sub>2</sub>Te<sub>6</sub>相変化材料の局所構造の解明

    畑山祥吾, YI Shuang, FONS Paul, FONS Paul, 齊藤雄太, KOLOBOV Alexander V., KOLOBOV Alexander V., 小林啓介, 進藤怜史, 安藤大輔, 須藤祐司

    応用物理学会春季学術講演会講演予稿集(CD-ROM) 67th 2020年

  7. No. 6 マグネシウム(Magnesium)

    安藤 大輔

    まてりあ 58 (11) 593-593 2019年11月1日

    出版者・発行元:公益社団法人 日本金属学会

    DOI: 10.2320/materia.58.593  

    ISSN:1340-2625

    eISSN:1884-5843

  8. 依頼講演 Co/Si界面の酸化物層がショットキー障壁高さと接触抵抗に及ぼす影響 (シリコン材料・デバイス)

    城戸 光一, 佐藤 謙, 黒田 理人, 安藤 大輔, 須藤 祐司, 小池 淳一

    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 119 (239) 35-38 2019年10月23日

    出版者・発行元:電子情報通信学会

    ISSN:0913-5685

  9. 低抵抗アモルファスCr<sub>2</sub>Ge<sub>2</sub>Te<sub>6</sub>の電気伝導機構

    畑山祥吾, 須藤祐司, 安藤大輔, 小池淳一, 小林啓介, 小林啓介

    応用物理学会春季学術講演会講演予稿集(CD-ROM) 66th 2019年

  10. アモルファスCr<sub>2</sub>Ge<sub>2</sub>Te<sub>6</sub>相変化材料の電気伝導機構

    畑山祥吾, 須藤祐司, 安藤大輔, 小池淳一, 小林啓介, 小林啓介

    日本金属学会講演概要(CD-ROM) 164th 2019年

    ISSN:2433-3093

  11. Cr<sub>2</sub>Ge<sub>2</sub>Te<sub>6</sub>を用いた相変化メモリの動作特性

    畑山祥吾, 須藤祐司, 安藤大輔, 小池淳一

    応用物理学会春季学術講演会講演予稿集(CD-ROM) 65th 2018年

  12. 低抵抗アモルファス相と高抵抗結晶相を有するCr<sub>2</sub>Ge<sub>2</sub>Te<sub>6</sub>を用いた相変化メモリ

    畑山祥吾, 須藤祐司, 安藤大輔, 小池淳一

    電子情報通信学会技術研究報告 118 (241(SDM2018 52-63)) 2018年

    ISSN:0913-5685

  13. 逆抵抗変化Cr<sub>2</sub>Ge<sub>2</sub>Te<sub>6</sub>相変化材料の結晶化メカニズム

    畑山祥吾, 須藤祐司, 安藤大輔, 小池淳一, 齊藤雄太, 進藤怜史, 進藤怜史, SONG Yun-Heub

    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 79th 2018年

  14. 超軽量形状記憶マグネシウム合金の開発

    須藤 祐司, 小川由 希子, 安藤 大輔, 小池 淳一

    アルトピア 47 (2) 5-8 2017年2月

    出版者・発行元:カロス出版

    ISSN:0285-5240

  15. 第11回本会派遣JIM/TMS Young Leader International Scholar出張報告

    安藤 大輔

    まてりあ 56 (6) 404-404 2017年

    出版者・発行元:公益社団法人 日本金属学会

    DOI: 10.2320/materia.56.404  

    ISSN:1340-2625

    eISSN:1884-5843

  16. 青色レーザーを用いたCu電極とSi太陽電池基板間のコンタクト形成

    雑賀真晃, 安藤大輔, 須藤祐司, 小池淳一, 坂本隼規, 諏訪雅也, 東條公資, 山蔭康弘

    応用物理学会春季学術講演会講演予稿集(CD-ROM) 64th 2017年

    ISSN:2436-7613

  17. 青色レーザーを用いたCu電極とSi太陽電池基板間のコンタクト形成

    雑賀真晃, 安藤大輔, 須藤祐司, 小池淳一, 坂本隼規, 諏訪雅也, 東條公資, 山蔭康弘

    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 78th 2017年

    ISSN:2436-7613

  18. マグネシウム合金の変形・破壊における変形双晶の役割と新合金探索

    安藤 大輔

    まてりあ 55 (8) 377-381 2016年

    出版者・発行元:公益社団法人 日本金属学会

    DOI: 10.2320/materia.55.377   10.2497/jjspm.66.547_references_DOI_XAIGWtMCsD7pbaGRQEduNZDF96w  

    ISSN:1340-2625

    eISSN:1884-5843

  19. 青色レーザーによるSiN反射防止膜除去とCu電極太陽電池セルの電気特性

    雑賀真晃, 安藤大輔, 須藤祐司, 小池淳一, 坂本隼規, 諏訪雅也, 東條公資, 山蔭康弘

    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 77th 2016年

    ISSN:2436-7613

  20. Cr-Ge-Te化合物薄膜の相変化挙動

    畑山祥吾, 進藤怜史, 安藤大輔, 須藤祐司, 小池淳一

    応用物理学会春季学術講演会講演予稿集(CD-ROM) 63rd 2016年

  21. W電極/GeCu<sub>2</sub>Te<sub>3</sub>相変化材料間のコンタクト抵抗

    進藤怜史, 須藤祐司, 安藤大輔, 小池淳一, 齊藤雄太

    日本金属学会講演概要(CD-ROM) 159th 2016年

    ISSN:2433-3093

  22. Cr-Ge-Te薄膜の相変化挙動

    畑山祥吾, 安藤大輔, 須藤祐司, 小池淳一

    応用物理学会秋季学術講演会講演予稿集(CD-ROM) 76th 2015年

  23. OS0317 六方晶金属の変形双晶モデルの構築とその結晶塑性シミュレーションへの適用

    石田 智広, 渋谷 慎兵, 加藤 準治, 寺田 賢二郎, 京谷 孝史, 安藤 大輔, 小池 淳一

    M&M材料力学カンファレンス 2012 "OS0317-1"-"OS0317-3" 2012年9月22日

    出版者・発行元:一般社団法人日本機械学会

    DOI: 10.1299/jsmemm.2012._os0317-1_  

    eISSN:2424-2845

    詳細を見る 詳細を閉じる

    A thermodynamics-based constitutive model, which accounts for both crystallographic slip and deformation twinning, is developed for a single crystal of hcp metals within the framework of finite crystal plasticity. While the volume fractions of stress-free twin deformations are introduced as internal variables, the free-energy involves the bulk energy of separate phases and the surface energy at twin interfaces, which are introduced as functions of the internal variables, in addition to the standard hardening-related energy in crystal plasticity framework. After the formulation is described in detail, a series of numerical examples is presented to verify the performance of the proposed model in predicting the deformation twinning, the successive deformation process and the twinning-induced stress responses. The results are studied with reference to the theoretical consequences and the experimental results reported in the literature.

  24. OS0316 Mg合金の局所変形量と変形双晶の関係

    安藤 大輔, 須藤 祐司, 小池 淳一, 石田 智広, 渋谷 慎平, 加藤 準治, 寺田 賢二郎, 京谷 孝史

    M&M材料力学カンファレンス 2012 "OS0316-1"-"OS0316-3" 2012年9月22日

    出版者・発行元:一般社団法人日本機械学会

    詳細を見る 詳細を閉じる

    In this study, the origin of amounts of localized strain in basal textured Magnesium alloy sheets was investigated. First, grid patterns were drawn on a top surface of sample by Focus Ion Beam system. And then, a distribution of crystal orientation from same area was observed by SEM/EBSD. From these methods, the relationship between the localized strain and crystal orientation was revealed. In generally, the amounts of strains are dependent on the crystal orientation, which means the facility of slip deformation. However, my results show that localized strain is dependent on the existence or absence of twins and twin types, and but not on the Schmid factor of basal slip. And I suggest that {1012} type has the roll of strain accommodation to satisfy the strain compatibility with neighbor grain in primary deformation stage and continue to cancel the strain of slip during deformation. So the grain with {10-12} type slightly deformed. On the other hand, {10-11} type has the roll of accommodation strain component to conform to externally applied stress. But {10-11} twin easily generate double twin. And the grain with double twin localized severely deformed and formed surface steps or cracks.

  25. Mg に魅せられて

    安藤 大輔

    まてりあ 51 (6) 265-265 2012年

    出版者・発行元:公益社団法人 日本金属学会

    DOI: 10.2320/materia.51.265  

    ISSN:1340-2625

    eISSN:1884-5843

  26. マグネシウム合金の変形・破壊機構における転位と双晶の役割

    安藤 大輔, 小池 淳一, 須藤 祐司

    金属 80 (11) 940-944 2010年11月

    出版者・発行元:アグネ技術センター

    ISSN:0368-6337

  27. 高アニール耐性・高反平行結合強度を有する積層フェリ構造の開発

    西村 真之, 渡邉 大輔, 大兼 幹彦, 安藤 康夫

    Transactions of the Magnetics Society of Japan 33 (3) 266-269 2009年

    出版者・発行元:公益社団法人 日本磁気学会

    DOI: 10.3379/msjmag.0903re8054  

    ISSN:1882-2924

    eISSN:1882-2932

  28. スピントロニクスの形成と発展

    宮崎 照宣, 大兼 幹彦, 桜庭 裕弥, 渡邉 大輔, 佐久間 昭正, 安藤 康夫, 久保田 均

    粉体および粉末冶金 55 (2) 109-115 2008年

    出版者・発行元:一般社団法人 粉体粉末冶金協会

    DOI: 10.2497/jjspm.55.109  

    ISSN:0532-8799

    eISSN:1880-9014

  29. AZ31マグネシウム合金における変形双晶形成に及ぼす結晶粒径の影響

    安藤 大輔, 小池 淳一

    大会講演概要 113 253-254 2007年10月10日

  30. 強磁性共鳴を用いたMRAMフリー層材料の磁気緩和定数測定

    安藤 康夫, 大兼 幹彦, 渡邉 大輔, 渡邉 美穂, 家形 諭, 宮崎 照宣

    日本応用磁気学会研究会資料 153 7-14 2007年2月27日

    ISSN:1340-7562

  31. コプレーナ伝送路を有する微小強磁性トンネル接合の作製

    青木 達也, 渡邉 大輔, 大坊 忠臣, 安藤 康夫, 大兼 幹彦, 宮崎 照宣

    日本応用磁気学会誌 31 (2) 94-97 2007年

    出版者・発行元:公益社団法人 日本磁気学会

    DOI: 10.3379/jmsjmag.31.94   10.3379/msjmag.32.355_references_DOI_Gfdrwj5xbK5YFKHYWWhdTBlC51Q  

    ISSN:0285-0192

    eISSN:1880-4004

  32. 集束イオンビームを用いた微小強磁性トンネル接合の作製

    渡邉 大輔, 久保田 均, 安藤 康夫, 宮崎 照宣

    日本応用磁気学会誌 28 (4) 569-572 2004年

    出版者・発行元:公益社団法人 日本磁気学会

    DOI: 10.3379/jmsjmag.28.569  

    ISSN:0285-0192

    eISSN:1880-4004

︎全件表示 ︎最初の5件までを表示

講演・口頭発表等 16

  1. Age hardening effect and Superelasticity of Martensitic transformable Mg-Sc based alloys 招待有り

    D. Ando, K. Yamagishi, Y. Sutou, J. Koike, Y. Ogawa

    The 10th Pacific Rim International Conference on Advanced Materials and Processing 2019年8月20日

  2. Superelasticity of Martensitic transformable Mg-Sc based alloys 招待有り

    D. Ando, K. Yamagishi, Y. Sutou

    The Future of Materials Engineering - Dramatic Innovation to the next 100 years 2019年6月25日

  3. Resistive Switching Behavior of Undoped Hematite Film with Low Resistivity 国際会議

    Y. OGAWA, Y. SUTOU, D. ANDO, J. KOIKE

    CIMTEC2014 2014年6月15日

  4. The electrical properties of binary Fe-O films deposited under various pxygen flow rate

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

    応用物理学会 2014年3月17日

  5. A new model of ductility enhancement in Mg with small amounts of Y by grain subdivision 国際会議

    Daisuke Ando, Yuji Sutou, Junichi Koike

    THERMEC' 2013 2013年12月2日

  6. Revolution of silicon solar cells by switching metal electrodes from silver to copper 国際会議

    H. T. Hai, J. S. Kim, S. Tanabe, Y. Sutou, J. Koike

    PT-BEMS 2013 (2013 JAPAN-TAIWAN SYMPOSIUM ON POLYSCALE TECHNOLOGIES FOR BIOMEDICAL ENGINEERING AND ENVIRONMENTAL SCIENCES 2013) 2013年9月7日

  7. 銅ペースト配線の開発-太陽電池低コスト化の基幹部材-

    Daisuke Ando, Hoang Tri Hai, Junichi Koike

    材料科学的アプローチによる太陽電池研究の最前線 2012年10月12日

  8. The Rolls of Deformation Twinning in Basal Textured AZ31 Mg Alloy 国際会議

    D. Ando, J. Kolile

    NIMS conference 2012 2012年6月4日

  9. Mg合金の変形双晶形成要因と双晶界面構造解析

    安藤 大輔, 小池 淳一

    第44回高性能Mg合金創成加工研究会 2012年1月20日

  10. Mgにおける局所変形量に及ぼす変形双晶の影響

    安藤 大輔, 小池 淳一

    2011年度 材料モデリング分科会 第三回分科会 2011年11月25日

  11. Plastic Anisotropy and Deformation Twinning in Magnesium Alloys 国際会議

    J. Koike, D.Ando

    International Symp. of Physics of Materials 12 2011年9月4日

  12. Mg合金の変形と破壊に関する基礎検討

    小池 淳一, 安藤 大輔, 藤山 直人, 須藤 祐司

    第19回素材工学研究懇談会 2010年11月17日

  13. マグネシウム合金における変形双晶の重要性

    小池 淳一, 安藤 大輔

    軽金属学会秋季(第115回)大会 2008年11月15日

  14. マグネシウム合金の変形双晶と破壊機構

    安藤 大輔, 小池 淳一

    第4回軽金属学会Mg研究会 2008年7月18日

  15. Deformation mechanisms of magnesium alloys at ambient temperature 国際会議

    小池 淳一, 安藤 大輔, 藤山 直人

    NIMS Week 2008年7月16日

  16. マグネシウム合金の変形機構における双晶の役割

    小池 淳一, 安藤 大輔, 佐藤 優典, 宮村 剛夫

    2007年度軽金属東北支部会セミナー 2008年2月1日

︎全件表示 ︎最初の5件までを表示

産業財産権 16

  1. 太陽電池用保護ガラスおよびその製造方法

    小池 淳一, 須藤 祐司, 安藤 大輔, 和田 真, 白澤 勝彦

    特許第6619139号

    産業財産権の種類: 特許権

  2. 太陽電池モジュールおよびその製造方法

    小池 淳一, 須藤 祐司, 安藤 大輔, 和田 真

    特許第6548896号

    産業財産権の種類: 特許権

  3. 超弾性効果及び/又は形状記憶効果を発現するマグネシウム合金

    安藤 大輔, 須藤 祐司, 小川 由希子, 小池 淳一

    特許第6497686号

    産業財産権の種類: 特許権

  4. 電子部品およびその製造方法

    小池 淳一, 安藤 大輔, 須藤 祐司

    特許第5972317号

    産業財産権の種類: 特許権

  5. 銅ペーストの焼成方法

    小池 淳一, 須藤 祐司, 安藤 大輔

    特許第5766336号

    産業財産権の種類: 特許権

  6. 太陽電池及びその製造方法

    小池 淳一, 須藤 祐司, 安藤 大輔, ホアン チ ハイ

    特許第5735093号

    産業財産権の種類: 特許権

  7. 超弾性効果及び/又は形状記憶効果を発現するマグネシウム合金

    安藤 大輔, 須藤 祐司, 小川 由希子, 小池 淳一

    産業財産権の種類: 特許権

  8. 太陽電池装置及びその製造方法

    小池 淳一, 和田 真, 須藤 祐司, 安藤 大輔

    産業財産権の種類: 特許権

  9. 水素発生合金、実験教材、マグネシウム電池用負極材、及び発電用水素発生剤

    安藤 大輔, 須藤 祐司, 内山 智元

    産業財産権の種類: 特許権

  10. 高比抵抗合金および抵抗器

    須藤 祐司, 監物 幸翼, 安藤 大輔, 石田 清仁

    産業財産権の種類: 特許権

  11. 太陽電池モジュールおよびその製造方法

    小池 淳一, 須藤 祐司, 安藤 大輔, 和田 真

    産業財産権の種類: 特許権

  12. 太陽電池用保護ガラスおよびその製造方法

    小池 淳一, 須藤 祐司, 安藤 大輔, 和田 真, 白澤 勝彦

    産業財産権の種類: 特許権

  13. 電子部品およびその製造方法

    小池 淳一, 安藤 大輔, 須藤 祐司

    産業財産権の種類: 特許権

  14. 電子部品およびその製造方法

    小池 淳一, 安藤 大輔, 須藤 祐司

    産業財産権の種類: 特許権

  15. 銅ペーストの焼成方法

    小池 淳一, 須藤 祐司, 安藤 大輔

    産業財産権の種類: 特許権

  16. 太陽電池及びその製造方法

    小池 淳一, 須藤 祐司, 安藤 大輔, ホアン チ ハイ

    産業財産権の種類: 特許権

︎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 24

  1. (Mg,Sc)規則BCC相を利用したMg合金の高強度化 競争的資金

    制度名:Grant-in-Aid for Scientific Research

    2013年4月 ~ 継続中

  2. 高性能・低価格太陽電池を実現するためのCuペーストの開発 競争的資金

    制度名:The Other Research Programs

    2012年4月 ~ 継続中

  3. 超弾性・形状記憶能を有するMg基合金の開発 競争的資金

    2011年4月 ~ 継続中

  4. プレス変形可能なマグネシウム合金の開発 競争的資金

    制度名:Cooperative Research

    2010年4月 ~ 継続中

  5. マグネシウム合金の変形・破壊挙動の解明 競争的資金

    制度名:Grant-in-Aid for Scientific Research

    2005年4月 ~ 継続中

  6. Eutectic Engineeringによる双晶型振動吸収性Al耐熱鋳造合金の創製

    安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2023年4月1日 ~ 2027年3月31日

  7. ディフェクトエンジニアリングにより光塑性効果を引き出す強靭化セラミックスの実現

    安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Challenging Research (Exploratory)

    研究機関:Tohoku University

    2022年6月30日 ~ 2024年3月31日

  8. ねじり押出により導入した三次元キンクによる超強化

    安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research

    研究種目:Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    研究機関:Tohoku University

    2021年4月1日 ~ 2023年3月31日

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    本研究ではミルフィーユ物質群をキンク強化材料にするための最適塑性加工プロセス確立を目的とし、温間押出加工中にねじり変形が付与される『温間ねじり押出加工』を種々の温度で行った場合のキンク形態およびその分布に関して調査し、温間押出加工では得られないほどの超強化を目指している。その理由は、単純ねじり変形が最も小さな相当ひずみ量で大きな材料強化をしている可能性に着目した一方で、鋳造材にねじりを加えると鋳造欠陥で容易に割れてしまい、押出材に後からねじりを加えると再結晶したα-Mg のみが変形し、ミルフィーユ構造に大きなねじり変形を与えられなかった。そこで、押出ながらねじることができればミルフィーユ組織に三次元キンクが形成できるのではないかと考えた。温間押出加工のダイスを変更することで、押出加工中にねじり加工を加えることができる「温間ねじり押出加工」を実施して、通常の押出加工では得られない方向へのせん断も加えることで、キンク形成量を増やすこと、二次元欠陥のキンクを形成軸とは違う向きにねじって三次元化して形成形態を変えることでミルフィーユ物質群の超強化を狙った研究を行っている。本年度は通常の押出加工と押出比は同じだが、押出出口部のダイスでねじり変形するサンプルとしないサンプルを準備して、その強化量を測定した。加工温度は350℃として、ねじり角度は90°とした。その結果、ビッカース硬度としては、通常押出材よりもねじり押出材の方が高かったが、圧縮変形においてはその関係性が逆転した。さらに、ねじり押出材は通常押出材の2-3倍の圧縮破断伸びを呈することが分かった。その理由は、通常押出材ではキンク変形が局在化して早期に材料的に座屈するが、ねじり押出材ではキンク変形が材料内部に均一に形成されることが影響していると考察している。

  9. 生体吸収性Mg-Sc合金の腐食環境下での機械特性変化と産業化に向けたワイヤーと薄肉管材の製法確立

    安藤 大輔

    2020年 ~ 2022年

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    A-STEP機能検証フェーズ(2019年度)にて申請者が取り組んできたMg-Sc合金は、医学界から長年望まれている、「生体分解性」と「超弾性特性」を併せ持つ唯一の材料と成り得ることが分かった。しかし、インプラント製品として実用化するには、生体分解に伴う機械特性の劣化挙動まで調べる必要がある。また、ステント基材となる線材(φ0.7mm)や管材(管肉厚200μm)へと塑性加工する手法の確立が不可欠である。そこで、本課題ではMg-Sc合金の生体腐食下での機械特性劣化挙動の調査、従来の塑性加工プロセスの最適化、ニアネットシェイプ法への挑戦による製造プロセスの産業化指針確立を目標とする。

  10. 自動車エンジン用400MPa超級ウィドマンシュテッテン組織型Mg耐熱性合金の創製

    安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory)

    研究種目:Grant-in-Aid for Challenging Research (Exploratory)

    研究機関:Tohoku University

    2019年6月28日 ~ 2021年3月31日

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    本研究は車両重量1000kgf減に匹敵する燃費向上が望める自動車用エンジンシリンダーを400MPa 超級ウィッドマンシュテッテン組織型Mg耐熱合金の創製することで達成を目指し、Mg基合金では初めての試みである相変態を利用した高温強度向上のメカニズムを明らかにした。その結果、300℃下で良好な延性を示し、最大引張強度が430MPaとなる合金を創製し、元素添加により、300℃長時間熱処理にも耐える合金を開発した。

  11. 高温ねじり加工法によるMFS物質のキンク強化材料化に不可欠なキンク形成素因子抽出

    安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    研究種目:Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    研究機関:Tohoku University

    2019年4月1日 ~ 2021年3月31日

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    本研究は、当該新学術領域研究課題で、高圧ねじり加工などの高次塑性加工で導入されたキンク形態とその分布が材料強化に与える影響の定量化を担当していることで、これらの実験データの理解には、単純なひずみ分布が得られ、かつ塑性加工温度を容易に変更できる『ねじり加工』により得られたデータをフィードバックする必要があると考え、キンク強化させるための最適塑性加工プロセス確立を目的とし、単純なひずみ分布が得られる『ねじり加工』を種々の温度で行った場合のキンク形態およびその分布に関する基礎的な知見を得ることを目的として実施した。 初年度は鋳造時にLPSO 相が形成されるタイプのMg-2at%Y-1at%Zn合金を用いた研究を行った。この合金系LPSO 合金は供試材が作製され、得られた研究結果は当該領域研究の全計画研究班で比較可能である。鋳造まま材の高温ねじり試験ではキンクを形成させることができ、高強度化できたが、押出材はねじり変形が再結晶粒に集中するためにさらに強度を付加することは出来なかった。そこで、次年度は鋳造材を熱処理して、結晶粒内にLPSO相がミルフィーユ状に析出したラメラ合金を用いて、キンク変形の発生状況とその形態、および分布状況から、閾値となるひずみ量ならびに加工温度を抽出し、キンク形成素因子を明らかすることを試みた。その結果、高温ねじり変形挙動において、400℃と500℃でその加工硬化挙動に大きな差異が見られた。400℃変形までは加工硬化を示すが、500℃では加工硬化しなかった。これはキンク変形よりも非底面すべりの活動が活発になったからであると考えられる。 また、LPSO単相材であるMg-9at%Y-6at%Zn鋳造材においても高温ねじり変形により高強度化が達成でき、同班の同じ供試材で様々な冷間・温間塑性加工法での強化能と比較して、低相当塑性ひずみ量で大きな強化を示すことが分かった。

  12. TRIP/TWIP相乗効果を伴うβ型Mg合金による超高強度・高延性化

    安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2018年4月1日 ~ 2021年3月31日

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    様々な添加濃度の2元系Mg-Sc合金及び、d軌道レベルによる相安定性・主たる変形機構の遷移を予想して3元系Mg-Sc-X合金を検討したが、変形双晶支配となる合金の創製には至らなかった。一方で、変形誘起マルテンサイト変態によるTRIP効果を発現する2元系Mg-Sc合金及び3元系Mg-Sc-X合金を創製することには至った。特に、XにRE(レアアース)元素を選択した合金においては、過去に報告されているいずれのMg基合金と比較しても、最も高い強度・延性バランスを有していることが明らかになった。

  13. 自己拡張型生体吸収性Mg-Sc基合金材の組織制御による超弾性回復ひずみ最大化

    安藤 大輔

    2019年 ~ 2020年

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    自己拡張型生体吸収性の金属製ステント開発のため、Mg-Sc基形状記憶合金の組成制御、集合組織制御により、室温での超弾性回復ひずみ量を現状3%から計算理論値6.9%に向けて最大化させることを目的とする。

  14. 自己不働態膜形成により溶出速度が調整できる生体内分解型超弾性Mg合金ステント

    安藤 大輔, 小池 淳一, 須藤 祐司

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory)

    研究種目:Grant-in-Aid for Challenging Research (Exploratory)

    研究機関:Tohoku University

    2017年6月30日 ~ 2019年3月31日

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    この研究では室温や体温で超弾性能を有するMg-Sc合金を創製すること、試料表面に形成されるSc自然酸化物が不働態膜となり、溶出速度が従来のMg合金に比べて遅くなるかについて調査することを目的に行い、室温でも3%の超弾性ひずみを有する合金が開発でき、5%NaCl溶液中に封入した場合、Sc添加量の上昇に伴い、溶出速度が遅くなること、同じ添加濃度でもα単相、β単相よりα+β二相の方がわずかに速い溶出速度になることが明らかになった。

  15. ダイナミック・ナノリフロー法によるLSI超微細配線の形成と機構解明

    小池 淳一, 安藤 大輔, 須藤 祐司

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)

    研究種目:Grant-in-Aid for Scientific Research (A)

    研究機関:Tohoku University

    2015年4月1日 ~ 2018年3月31日

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    LSIデバイスは微細化することによって高性能化を実現してきたが、多層配線が細くなり過ぎて形成できないという課題があった。本研究では、高温で銅合金をスパッタ成膜するダイナミックナノリフロー法によって幅が15nmの超微細配線(M2配線とビア)を形成する条件を見出した。この方法によれば成膜中に合金元素が絶縁層界面に偏析して蒸着物の濡れ性を向上する。また、配線形成の可否を決める因子は、配線形成初期の表面曲率勾配と加熱・冷却中の熱応力勾配であり、それぞれの因子による駆動力を定量的に評価したところ同等の効果であることが明らかになった。得られた知見をもとにリフロー挙動をシミュレーションすることができた。

  16. 次世代微細PCRAMに向けた相変化材料/電極間の接触界面抵抗に関する研究

    須藤 祐司, 小池 淳一, 安藤 大輔, 小林 啓介, 進藤 怜史

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    研究種目:Grant-in-Aid for Scientific Research (B)

    研究機関:Tohoku University

    2015年4月1日 ~ 2018年3月31日

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    相変化メモリの大容量化には相変化材料(PCM)/電極構造の微細化がカギとなるが、微細メモリセル抵抗はPCM/電極間の接触抵抗に支配される。本研究では、PCMの接触抵抗率を評価すると共に、次世代メモリの創成を試みた。その結果、アモルファスCu2GeTe3/電極はショットキー伝導を示し界面伝導に支配される事が分かった。また、耐熱性に優れる新PCMとしてCr2Ge2Te6を見出した。Cr2Ge2Te6は通常とは逆に、結晶抵抗率がアモルファス抵抗率よりも高い。更に、その抵抗率差は一桁であるが、接触抵抗率差は二桁を示すためメモリへの適用が可能であり、また、動作エネルギーを大幅に低減できる事が分かった。

  17. BCC/HCP相変態を利用した超高強度かつ高機能性を有するMg-Sc合金の創製

    安藤 大輔, 小池 淳一, 須藤 祐司, 小川 由希子, 竹内 悠太

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)

    研究種目:Grant-in-Aid for Young Scientists (A)

    研究機関:Tohoku University

    2015年4月1日 ~ 2018年3月31日

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    本研究はBCC/HCP相変態を利用した高強度化および高機能化を目指した新規Mg-Sc合金を創製し、特にMg基合金において世界で初めてBCC相からorthorhombic相へとマルテンサイト変態すること、また、それを利用した超弾性・形状記憶効果を発現させることに成功した。この成果は、Mg基では母相が柔らかすぎてマルテンサイト変態は生じないという定説を覆す学術的に意味のあることだけでなく、自己展開型太陽電池パネルフレームなど航空宇宙材料や生体分解性インプラントなど医療分野への利用に対する新しい可能性が示された。

  18. 2ビット情報の記録可能な積層縦型構造多値記録相変化メモリ素子の創製

    須藤 祐司, 安藤 大輔, 小池 淳一, 齊藤 雄太, 進藤 怜史

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

    研究種目:Grant-in-Aid for Challenging Exploratory Research

    研究機関:Tohoku University

    2015年4月1日 ~ 2017年3月31日

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    次世代不揮発性メモリとして、アモルファス相と結晶相の電気抵抗差を利用した相変化メモリが注目されている。更なる大容量化を目指し、相変化メモリの多値記録化が期待されている。本研究では、二段階結晶化を示す相変化材料と一段階結晶化を示す相変化材料を積層する事により、2ビットの多値記録実現を目指した。Cu-Ge-Teについて、二段階結晶化過程を示す組成範囲を明確にした。その結果、23.4Cu-28.8Ge-47.8Te薄膜とGeTe薄膜の積層組み合わせにより、2ビット情報記録が可能である事が分かった。

  19. 転位・双晶ハイブリッド型制振効果による広周波数域対応α+β二相Mg合金の創製

    安藤 大輔, 小池 淳一, 須藤 祐司

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

    研究種目:Grant-in-Aid for Challenging Exploratory Research

    研究機関:Tohoku University

    2015年4月1日 ~ 2017年3月31日

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    本課題はMg-Sc合金においてマルテンサイト変態を利用し、転位型の制振性と双晶型の制振性を併せ持った高周波域対応制振合金を創製する目的で行い、研究期間内においては、(1)マルテンサイト変態に対する組成依存性の影響、(2)HCP単相・BCC単相合金の制振特性の評価、(3)良好な制振特性を得るための最適組織の確立の三点を目標に実験を行った。 その結果、マルテンサイトの変態温度はSc濃度に著しく依存することが分かった。また、二元系ではBCC相が柔らかいために転位が発生して、マルテンサイト変態による制振性が効率よく生じていないことが分かった。今後はBCC相を添加元素などにより硬化させる試みが必要である。

  20. 優先酸化を利用した極小結晶相電流パス自己形成による相変化メモリのデータ書換高速化

    須藤 祐司, 小池 淳一, 安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

    研究種目:Grant-in-Aid for Challenging Exploratory Research

    研究機関:Tohoku University

    2013年4月1日 ~ 2015年3月31日

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    不揮発性メモリとして、アモルファス/結晶変化を利用した相変化メモリ(PCRAM)が注目されている。現在、PCRAM材料として、GeSbTe材料が実用化されているが、結晶化温度(Tc)が低くデータ保持性能に劣る。一方、高Tc材料を用いればデータ保持性能は向上するが、データ書換速度の遅延を生む。それ故、高いTcを維持しつつ、結晶化速度を速める必要がある。 本研究では、相変化材料の表面・界面制御による相変化速度向上を試みた。その結果、GeTe-Si薄膜の表面酸化により、表面からの不均一核生成によって結晶化が進行する事が分かった。また、その不均一核生成により結晶化速度が速くなることが明らかとなった。

  21. (Mg,Sc)規則BCC相を利用したMg合金の高強度化

    安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

    研究種目:Grant-in-Aid for Young Scientists (B)

    研究機関:Tohoku University

    2013年4月1日 ~ 2015年3月31日

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    HCP単相やBCC単相、HCP+BCC二相組織を呈するMg-Sc合金を作製し、機械特性、特にビッカース硬さに関して系統的に調査した。HCP単相、BCC単相のビッカース硬さを計測したところ、それぞれ115、100Hvであった。また、BCC単相の試料(16.8at.%Sc;EPMAで測定)を様々な温度にて時効熱処理を行った結果、BCC相中にHCP相がBurger'sの関係で析出することが分かり、200℃で5時間時効することで、HCP相は数十nm程度の大きさで高密度に析出し、その硬さは231.5Hvにも達した。この硬さは金属ガラスを除いては、Mg基で最も高い値であった。

  22. 半導体多層配線のプロセス限界を超越する拡散バリア層の開発原理

    小池 淳一, 須藤 祐司, 根石 浩司, 安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (S)

    研究種目:Grant-in-Aid for Scientific Research (S)

    研究機関:Tohoku University

    2010年4月1日 ~ 2015年3月31日

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    半導体多層配線は、微細化の進展に伴って導体配線と絶縁層の界面に存在するバリア層厚さを可能な限り薄くすることが求められている。本研究はバリア層自己形成法に着目し、その形成機構を明らかにするとともに、プロセス限界を超越できる拡散バリア層の材料ならびに形成方法を提供することを目的とした。バリア層自己形成機構に関しては、電界促進拡散による機構であることを明らかにし、合金元素によって電界強度に差異が生じるため自己形成挙動が異なることを示した。また、将来の超微細配線を想定して、化学気相成長法による極薄バリア層の形成法とスパッタリフロー法による配線の形成法を確立し、それらの形成機構を明らかにした。

  23. β-Sc相を利用したBCC/HCP二相マグネシウム合金の組織制御

    安藤 大輔

    提供機関:Japan Society for the Promotion of Science

    制度名:Grants-in-Aid for Scientific Research Grant-in-Aid for Research Activity Start-up

    研究種目:Grant-in-Aid for Research Activity Start-up

    研究機関:Tohoku University

    2011年 ~ 2011年

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    従来のMg合金開発では、HCP相に固溶、析出させる研究が多いが、本研究ではMg-Sc合金でβ-Sc(BCC)相を利用した組織制御により、BCC/HCP二相化が可能であることを初めて見出した。また、これまでに報告されていた状態図よりも低Sc濃度までβ-Sc(BCC)相が存在することがわかった。さらに、本二相合金は従来のMg合金の強度延性バランスを凌駕する高強度かつ高延性をもつことがわかった。

  24. FIB/TEM断面観察による定量的破壊評価法を用いたMg合金の疲労破壊機構の解明 競争的資金

    安藤 大輔

    制度名:Grant-in-Aid for Scientific Research

    2010年 ~ 2011年

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    私の研究の目的は、高寿命高疲労強度を有するMg合金の開発のために、Mg合金の疲労破壊機構を変形双晶に着目し、破壊原因の解明をすることにある。そのために特徴的な疲労破面をFIBで断面加工し、TEMで内部構造観察することによって、定量的な破壊評価法の確立を目指した。 当該年度においては、疲労破壊の原因を単純化するために引張応力、圧縮応力のみの疲労試験を結晶粒径および応力を制御して、破壊形態の変化を明らかにすることを実施計画とした。実際には、引張応力下での破壊形態の詳細な調査をすることになった。 以下に、当該年度の研究成果について示す。試料は熱処理条件によって結晶粒径を調整し、作製した。変形双晶は結晶粒径が微細なほど生じにくい。疲労強度は結晶粒径5μmで120MPa、200μmで70MPaであった。また、繰返引張試験の結果から、疲労破壊は従来関係性が指摘されていた{1012}双晶の形成とは関係がないことがわかり、疲労破壊の原因はサイクル毎に試料内部に蓄積するひずみであることを明らかにした。また、微細粒径試料においてのひずみの蓄積は非底面すべりによって生じ、粗大粒径試料においては二重双晶の形成による局所的な大変形で生じることも明らかにした。破面とその内部組織構造とを1対1対応化させ、疲労破壊メカニズムと変形双晶の関係を示すという研究成果によって、単純引張試験においてだけでなく、引張疲労試験においても早期破壊の原因が二重双晶によることを示したことは今後のMg合金の疲労破壊研究において大きな意義があったと考える。

︎全件表示 ︎最初の5件までを表示