Details of the Researcher

PHOTO

Akira Nagakubo
Section
Graduate School of Engineering
Job title
Associate Professor
Degree

  • 博士（工学）（大阪大学）

  • 修士（工学）（大阪大学）

e-Rad No.
70751113

Research History 12

  • 2024/10 - Present
    Tohoku University　Division for the Establishment of Frontier Sciences of Organization for Advanced Studies

  • 2024/10 - Present
    Tohoku University　Graduate School of Engineering Materials Science and Engineering　Associate Professor

  • 2022/04 - 2024/09
    Osaka University　Center for Future Innovation, Graduate School of Engineering　Outstanding Young Researchers, Assistant Professor

  • 2020/04 - 2022/03
    Osaka University　Division of Precision Engineering and Applied Physics, Graduate School of Engineering　Assistant Professor

  • 2018/04 - 2020/03
    Osaka University　Department of precision Science and Technology, Graduate School of Engineering　Assistant Professor

  • 2017/04 - 2018/03
    Kyoto University　Nano-spintronics, Institute for Chemical Research　JSPS Research Fellowship for Young Scientists (PD)

  • 2016/10 - 2017/03
    Osaka University　Division of Nonlinear Mechanics, Science Department of Mechanical Science and Bioengineering, Graduate School of Engineering　Specially Appointed Assistant Professor

  • 2016/04 - 2016/09
    Los Alamos National Laboratory　Materials Physics and Applications　Visiting Scientist

  • 2016/04 - 2016/09
    Osaka University　Division of Nonlinear Mechanics, Science Department of Mechanical Science and Bioengineering, Graduate School of Engineering　Visiting Researcher

  • 2015/04 - 2016/03
    Osaka University　Division of Nonlinear Mechanics, Science Department of Mechanical Science and Bioengineering, Graduate School of Engineering　Specially Appointed Assistant Professor

  • 2014/04 - 2015/03
    Osaka University　Division of Nonlinear Mechanics, Science Department of Mechanical Science and Bioengineering, Graduate School of Engineering,　JSPS Research Fellowship for Young Scientists (PD)

  • 2012/04 - 2014/03
    Osaka University　Division of Nonlinear Mechanics, Science Department of Mechanical Science and Bioengineering, Graduate School of Engineering　JSPS Research Fellowship for Young Scientists (DC1)

Show all Show first 5

Education 3

  • Osaka University　Division of Nonlinear Mechanics, Science Department of Mechanical Science and Bioengineering, Graduate School of Engineering　Ph.D. student

    2012/04 - 2014/03

  • Osaka University　Division of Nonlinear Mechanics, Science Department of Mechanical Science and Bioengineering, Graduate School of Engineering　Ph. D. student

    2011/04 - 2012/03

  • Osaka University　Mechanical Science Course, Department of System Science, School of Engineering Science　Undergraduate student

    2007/04 - 2011/03

Committee Memberships 4

  • 公益社団法人 応用物理学会関西支部　庶務

    2024/04 - Present

  • The Institute of Electronics, Information and Communication Engineers　Ultrasonics Committee

    2020/06 - Present

  • Symposium on Ultrasonic Electronics　Organizing Committee

    2020/04 - 2022/03

  • Symposium on Ultrasonic Electronics　Local Committee

    2019/04 - 2020/03

Professional Memberships 2

  • IEEE

    2024/03 - Present

  • The Japan Society of Applied Physics

    2011/01 - Present

Research Interests 9

  • spintronics

  • physical acoustic

  • phonon

  • sensor

  • thin film

  • laser

  • sound velocity

  • elastic constant

  • ultrasonics

Research Areas 2

  • Nanotechnology/Materials / Nanomaterials /

  • Nanotechnology/Materials / Applied physics - general /

Awards 8

  1. Osaka University Prize

    2022/11　Osaka University

  2. Outstanding Reviewer Awards 2021

    2022/04　IOP Publishing

  3. Young Scientist Award

    2014/12　Symposium on Ultrasonic Electronics

  4. Young Scientist Presentation Award

    2014/09　The Japan Society of Applied Physics

  5. Encouragement Prize for article presentations abroad

    2013/09　Association for the Advancement of Manufacturing & Technology

  6. Science Engineering Graduate Student Award

    2011/03　Osaka University

  7. Eiji Muto Excellent Student Award

    2010/03　Japan Society for Design Engineering

  8. Science Engineering Student Award

    2010/03　Osaka University

Show all ︎Show 5

Papers 66

  1. Deep-Learning Generation of High-Resolution Images of Live Cells in Culture Using Tri-Frequency Acoustic Images Peer-reviewed

    Natsumi Fujiwara, Midori Uno, Hiroki Fukuda, Akira Nagakubo, Shao Ying Tan, Masahiro Kino-oka, Hirotsugu Ogi

    Physical Review X　15　(2)　021015　2025/04/15

    Publisher: American Physical Society (APS)

    DOI： 10.1103/physrevx.15.021015 　

    eISSN： 2160-3308

    More details Close

    Ultrasound microscopy is the only technique that has the ability to monitor live-cell morphology over a long period of time without causing any damage to the cells, but its longer wavelength prevents one from obtaining high-resolution cell images. Here, we propose a deep-learning (DL) method for generating high-resolution acoustic images. By preparing datasets consisting of many pairs of acoustic and optical-microscope images for the same cells and training them, a high-resolution image comparable to optical microscopy is generated from an acoustic image. Importantly, the most accurate images are generated when three-layer (RGB) images containing not only high-frequency (approximately 180 MHz) images but also lower-frequency (approximately 100 MHz) images are used as the input images, which is attributed to enhanced acoustic absorption in the nucleus because the nucleus resonates in this low-frequency band. The DL scheme with the tri-frequency image input is applied to human mesenchymal stem cells and human induced pluripotent stem cells, and the high image-generation capability is demonstrated. As a result, high-resolution acoustic microscopy images are obtained for the same cells for over 24 h, without the typical cell damage encountered using optical imaging. Published by the American Physical Society 2025

  2. Coupled Nanomechanical Resonator with Protein-Interaction Vibration for an Ultrasensitive Label-Free Biosensor Peer-reviewed

    Ryo Hirose, Takuya Haraguchi, Akira Nagakubo, Masamitsu Tachibana, Mutsuaki Murakami, Hirotsugu Ogi

    ACS Applied Materials & Interfaces　17　23405　2025/04/02

    Publisher: American Chemical Society (ACS)

    DOI： 10.1021/acsami.5c03549 　

    ISSN： 1944-8244

    eISSN： 1944-8252

  3. Time course observation of cross-sectional shape of iPS cell colony using ultrasound spectroscopic imaging Peer-reviewed

    Natsumi Fujiwara, Takaki Matsumoto, Akira Nagakubo, Shao Ying Tan, Masahiro Kino-oka, Hirotsugu Ogi

    npj Biological Physics and Mechanics　2　(1)　1　2025/01/10

    Publisher: Springer Science and Business Media LLC

    DOI： 10.1038/s44341-024-00004-0 　

    eISSN： 3004-863X

  4. Sensitivity enhancement of hydrogen-gas sensor by sub nm Au on Pd surface of a wireless quartz resonator Peer-reviewed

    Akira Nagakubo, Tokiya Matsukura, Hirotsugu Ogi

    Japanese Journal of Applied Physics　63　(7)　074002-074002　2024/07/01

    Publisher: IOP Publishing

    DOI： 10.35848/1347-4065/ad61a7 　

    ISSN： 0021-4922

    eISSN： 1347-4065

    More details Close

    Abstract Hydrogen (H2) is an important source of next-generation energy production. The various H2 sensors developed to date cannot easily detect very low concentrations of H2 (<10 ppm) at room temperature within 100 s. In this study, we develop H2 sensors by depositing a 200 nm thick palladium (Pd) film on AT-cut quartz resonators and adding a sub nm gold (Au) layer on the Pd surface. Moderate Au deposition on the Pd surface improves the sensitivity of the sensor by decreasing the activation energy of atomic-hydrogen migration from the surface to the subsurface. The optimal Au thickness that minimizes the activation energy is 0.5 nm. Finally, we show that the approximate detection limit at room temperature is 5 ppm.

  5. Development of a focused-ultrasound spectroscopic-imaging system combined with optical imaging for applying mechanical stimulation on living cells and the possibility of selective stimulation for the nucleus Peer-reviewed

    Natsumi Fujiwara, Shao Ying Tan, Takaki Matsumoto, Akira Nagakubo, Masahiro Kino-oka, Hirotsugu Ogi

    Japanese Journal of Applied Physics　63　(3)　03SP65-03SP65　2024/03/01

    Publisher: IOP Publishing

    DOI： 10.35848/1347-4065/ad2651 　

    ISSN： 0021-4922

    eISSN： 1347-4065

    More details Close

    Abstract Various techniques have been used for the mechanical stimulation of cells, but most of them require direct contact with cells and can damage them. Here, we propose a focused ultrasound technique for non-invasive localized mechanical stimulation in a culture environment. First, we develop the focused ultrasound system for establishing the spectroscopic images and for applying mechanical stimulation combined with optical observation. Second, we construct the acoustic-absorption spectroscopic images of human mesenchymal stem cells, leading to the finding of the ultrasound absorption band of the nucleus around 130 MHz caused by its resonance. Finally, we find that the nucleus less absorbs ultrasound before the cell division, supporting our view that the acoustic absorption band is related to the resonance of the nucleus. Our results show the potential for realizing selective and effective mechanical stimulation for nuclei non-invasively, which is critically important for a deeper understanding of mechanobiology.

  6. GHz surface-wave phononic crystal biosensor using a Fano resonance at the bandgap edge

    Wenlou Yuan, Akira Nagakubo, Oliver B. Wright, Hirotsugu Ogi

    Japanese Journal of Applied Physics　63　(1)　017006-017006　2024/01/01

    Publisher: IOP Publishing

    DOI： 10.35848/1347-4065/ad193a 　

    ISSN： 0021-4922

    eISSN： 1347-4065

    More details Close

    Abstract We propose an ultrahigh-sensitivity biosensor based on a GHz surface-acoustic-wave nanopillar phononic crystal using a Fano resonance at the bandgap edge. By means of numerical simulations, we find that the asymmetric, sharp and controllable transmission dip at the bandgap edge arising from the Fano resonance, which is caused by mode coupling between a local nanopillar resonance and the surface acoustic waves, allows ultrasensitive detection of attached biomolecules. The effect of such mass loading is studied, showing an attogram detection limit, and a unique “on–off” triggering at the sub-femtogram level for each individual Au nanopillar. This study opens up frontiers for biosensing applications of phononic crystals and ultrahigh-frequency surface acoustic wave devices.

  7. Elastic constants of GaN grown by the oxide vapor phase epitaxy method Peer-reviewed

    Hiroki Fukuda, Akira Nagakubo, Shigeyoshi Usami, Masayuki Imanishi, Yusuke Mori, Hirotsugu Ogi

    Applied Physics Express　17　(1)　016501-016501　2023/12/26

    Publisher: IOP Publishing

    DOI： 10.35848/1882-0786/ad0ba2 　

    ISSN： 1882-0778

    eISSN： 1882-0786

    More details Close

    Abstract Oxide vapor phase epitaxy (OVPE) has attracted much attention as a highly efficient method for synthesizing high-quality bulk GaN crystals, but the mechanical properties of OVPE GaN have not been clarified. We measured the five independent elastic constants of the OVPE GaN by resonant ultrasound spectroscopy. The in-plane Young modulus E 1 and shear modulus C 66 of the OVPE GaN are smaller than those of the hydride vapor phase epitaxy GaN by 1.8% and 1.3%, respectively. These reductions agree with predictions by density functional theory calculations. We also calculated the Debye temperature, revealing that oxygen impurity decreases its magnitude.

  8. 2E1-4 Development of a focused ultrasound spectroscopic imaging system combined with optical imaging for applying mechanical stimulation on living cells

    Fujiwara Natsumi, Matsumoto Takaki, Ying Tan. Shao, Nagakubo Akira, Nakajima Kichitaro, Kino-oka Masahiro, Ogi Hirotsugu

    Proceedings of Symposium on Ultrasonic Electronics　44　84　2023/11/13

    Publisher: Institute for Ultrasonic Elecronics

    DOI： 10.24492/use.44.0_2e1-4 　

    ISSN： 1348-8236

    eISSN： 2433-1910

  9. Deep-Learning-Assisted Resonant Ultrasound Spectroscopy for Cubic Solids Peer-reviewed

    Hiroki Fukuda, Akira Nagakubo, Oliver B. Wright, Kazuhiro Kyotani, Hirotsugu Ogi

    Physical Review Applied　20　(3)　2023/09/21

    Publisher: American Physical Society (APS)

    DOI： 10.1103/physrevapplied.20.034048 　

    eISSN： 2331-7019

  10. High sensitivity biosensing scheme based on a GHz phononic crystal waveguide Peer-reviewed

    Wenlou Yuan, Akira Nagakubo, Oliver B. Wright, Hirotsugu Ogi

    Japanese Journal of Applied Physics　62　(SJ)　SJ1012-SJ1012　2023/02/14

    Publisher: IOP Publishing

    DOI： 10.35848/1347-4065/acb2d6 　

    ISSN： 0021-4922

    eISSN： 1347-4065

    More details Close

    Abstract We propose a high sensitivity biosensor based on a GHz phononic crystal (PnC) waveguide, and demonstrate its operation by numerical simulations. The geometry consists of a micron-scale freestanding PnC silica waveguide plate with embedded Au nanopillars for bioparticle attachment, the PnC plate lying between two groups of periodic metal strips for GHz Lamb-wave acoustic generation and detection with ultrashort light pulses. By precise choice of the waveguide defect width, this biosensor is designed to work using a single, isolated waveguide mode. We study the influence of the waveguide defect width on the acoustic dispersion and transmission of this mode. Bioparticle attachment is simulated by investigation of the Au nanopillar mass loading, and is shown to shift the waveguide transmission peak to lower frequencies. We thereby demonstrate femtogram detection, showing that our approach provides a new methodology for label-free ultra-sensitive biosensing.

  11. 3Pb2-4 Development of a high-frequency focused ultrasound system for applying noninvasively localized mechanical stimulation on cultured cells

    Fujiwara Natsumi, Matsumoto Takaki, Nagakubo Akira, Kino-oka Masahiro, Ogi Hirotsugu

    Proceedings of Symposium on Ultrasonic Electronics　43　425　2022/11/07

    Publisher: Institute for Ultrasonic Elecronics

    DOI： 10.24492/use.43.0_3pb2-4 　

    ISSN： 1348-8236

    eISSN： 2433-1910

  12. The angular dependence of magnetization dynamics induced by a GHz range strain pulse Peer-reviewed

    Kakeru Tojo, Akira Nagakubo, Hirotsugu Ogi

    Japanese Journal of Applied Physics　61　(SG)　SG1007-SG1007　2022/07/01

    Publisher: IOP Publishing

    DOI： 10.35848/1347-4065/ac4a04 　

    ISSN： 0021-4922

    eISSN： 1347-4065

    More details Close

    <title>Abstract</title> The dynamics of magnetization is important in spintronics, where the coupling between phonon and magnon attracts much attention. In this work, we study the angular dependence of the coupling between longitudinal-wave phonon and magnon. We investigated the magnetization dynamics using the time-resolved magneto-optical Kerr effect, which allows measuring spin-wave resonances and the magnetic echo signal. The frequency, mode number, and amplitude of the spin-wave resonance change with the out-of-plane angle of the external magnetic field. The amplitude of the magnetic echo signal caused by the strain pulse also changes with the angle. We calculate these angular dependences based on the Landau–Lifshitz–Gilbert equation and find that the angles of the external field and magnetic moment are important factors for the phonon–magnon coupling when phonon propagates in the thickness direction under the out-of-plane magnetic field.

  13. Lattice thermal conductivity in isotope diamond asymmetric superlattices Peer-reviewed

    Hsu Kai Weng, Akira Nagakubo, Hideyuki Watanabe, Hirotsugu Ogi

    Japanese Journal of Applied Physics　61　(SG)　SG1004-SG1004　2022/07/01

    DOI： 10.35848/1347-4065/ac4304 　

    ISSN： 0021-4922

    eISSN： 1347-4065

  14. Determination of the electron trap level in Fe-doped GaN by phonon-assisted conduction phenomenon Peer-reviewed

    Hiroki Fukuda, Akira NAGAKUBO, Shigeyoshi Usami, Masashi Ikeda, Masayuki Imanishi, Masashi Yoshimura, Yusuke MORI, Kanta Adachi, Hirotsugu OGI

    Applied Physics Express　15　(7)　071003-071003　2022/05/30

    Publisher: IOP Publishing

    DOI： 10.35848/1882-0786/ac749c 　

    ISSN： 1882-0778

    eISSN： 1882-0786

    More details Close

    Abstract We acoustically measured the energy level for thermally activated conduction (TAC) in high-resistivity Fe-doped GaN using the non-contacting antenna-transmission acoustic-resonance method. The acoustic attenuation takes a maximum at a specific temperature, where the TAC is accelerated with the help of phonon energy. The Debye type relaxation is thus observed for acoustic attenuation, and its activation energy (0.54±0.04 eV) was determined with attenuation measurements at various frequencies and temperatures. This value agrees with the E3 level in GaN, indicating that thermally associated conduction originates from the E3 trap level. We also measured the five independent elastic constants at high temperatures.

  15. Variable repetition frequency asynchronous optical sampling method without a feedback loop Peer-reviewed

    A. Nagakubo, K. Kanai, H. Tamura, A. Tange, H. Ogi

    AIP Advances　12　(4)　045323-045323　2022/04/01

    Publisher: AIP Publishing

    DOI： 10.1063/5.0083354 　

    eISSN： 2158-3226

    More details Close

    The ultrafast pump–probe measurement represents a key technique to study fs–ps dynamics. The asynchronous optical sampling (ASOPS) method realizes fast and long time-range measurement with high time resolution using different repetition frequency pump–probe light pulses. The frequency difference Δ f is an important parameter, as it dictates the measurement time and time resolution. However, usual ASOPS measurements require a complex and precise stabilizer to control Δ f or it is difficult to change Δ f. In this study, we use two free-running titanium/sapphire pulse lasers to develop a variable repetition frequency ASOPS (VRF-ASOPS) method without a stabilizer or feedback loop, where we can easily alter Δ f by changing the cavity length of the probe light laser. To detect the coincidences of the pump–probe light pulses, we cause the instantaneous reflectivity change in a 100 nm platinum film by irradiating the pump light and observe it by the probe light. We use this signal as the trigger signal to directly determine Δ f, which enables us to average and convert the measured responses without a stabilizer or feedback loop. Using this VRF-ASOPS system, we obtain pulse echo signals and 100 GHz Brillouin oscillations, which are equivalent to those measured by the mechanical delay line method, confirming the validity of our developed method.

  16. Suppression of Brillouin oscillation in transparent free-standing diamond thin films in picosecond ultrasound Peer-reviewed

    H. K. Weng, A. Nagakubo, H. Watanabe, H. Ogi

    Applied Physics Letters　120　(11)　112203-112203　2022/03/14

    Publisher: AIP Publishing

    DOI： 10.1063/5.0087648 　

    ISSN： 0003-6951

    eISSN： 1077-3118

    More details Close

    Brillouin oscillation appears in picosecond ultrasonics for a transparent specimen because of backward light scattering by moving strain pulse. Its amplitude is comparable with those of other responses, such as pulse-echo signals and through-thickness resonance, obscuring these non-Brillouin-oscillation responses. We here find that Brillouin oscillation can be suppressed in a transparent free-standing film by coating both sides with a metallic thin film of appropriate thickness and that this peculiar behavior is caused by strain pulses generated on both sides with a slight phase difference. This phenomenon allowed us to fabricate a Brillouin-oscillation-free diamond free-standing film, which showed a high capability for sensor applications.

  17. Effect of interfacial damping on high-frequency surface wave resonance on a nanostrip-bonded substrate Peer-reviewed

    Wenlou Yuan, Akira Nagakubo, Hirotsugu Ogi

    Journal of Applied Physics　131　(1)　015103-015103　2022/01/07

    DOI： 10.1063/5.0075585 　

    ISSN： 0021-8979

    eISSN： 1089-7550

  18. 1J4-2 Ultrasound-spectroscopy imaging on human iPS cells for mechanobiology study

    Fujiwara Natsumi, Matsumoto Takaki, Nagakubo Akira, Kino-oka Masahiro, Ogi Hirotsugu

    Proceedings of Symposium on Ultrasonic Electronics　42　n/a　2021/10/25

    Publisher: Institute for Ultrasonic Elecronics

    DOI： 10.24492/use.42.0_1j4-2 　

    ISSN： 1348-8236

    eISSN： 2433-1910

  19. Phonon propagation in isotopic diamond superlattices Peer-reviewed

    H. K. Weng, A. Nagakubo, H. Ogi, H. Watanabe

    Physical Review B　104　(5)　2021/08/16

    Publisher: American Physical Society (APS)

    DOI： 10.1103/physrevb.104.054112 　

    ISSN： 2469-9950

    eISSN： 2469-9969

  20. Elastic constant of dielectric nano-thin films using three-layer resonance studied by picosecond ultrasonics Peer-reviewed

    Hiroki Fukuda, Akira Nagakubo, Hirotsugu Ogi

    Japanese Journal of Applied Physics　60　(SD)　SDDA05-SDDA05　2021/07/01

    Publisher: {IOP} Publishing

    DOI： 10.35848/1347-4065/abec5a 　

    ISSN： 0021-4922

    eISSN： 1347-4065

  21. MEMS hydrogen gas sensor with wireless quartz crystal resonator Peer-reviewed

    Lianjie Zhou, Fumihito Kato, Nobutomo Nakamura, Yasushi Oshikane, Akira Nagakubo, Hirotsugu Ogi

    Sensors and Actuators B: Chemical　334　129651-129651　2021/05

    Publisher: Elsevier {BV}

    DOI： 10.1016/j.snb.2021.129651 　

    ISSN： 0925-4005

  22. Thermal conduction in isotope diamond thin films studied by pump-probe laser reflectivity measurement Peer-reviewed

    Hsu Kai Weng, Akira Nagakubo, Hideyuki Watanabe, Hirotsugu Ogi

    Japanese Journal of Applied Physics　59　2020/07/01

    DOI： 10.35848/1347-4065/ab7c0f 　

    ISSN： 0021-4922

    eISSN： 1347-4065

  23. Enhancement of sensitivity of Pd-based hydrogen-gas sensor by plasma exposure studied by wireless quartz resonator Peer-reviewed

    Lianjie Zhou, Nobutomo Nakamura, Akira Nagakubo, Hirotsugu Ogi

    Japanese Journal of Applied Physics　59　(SK)　SKKB02-SKKB02　2020/07/01

    DOI： 10.35848/1347-4065/ab78e2 　

    ISSN： 0021-4922

    eISSN： 1347-4065

  24. Interplanar stiffness in defect-free monocrystalline graphite Peer-reviewed

    Koichi Kusakabe, Atsuki Wake, Akira Nagakubo, Kensuke Murashima, Mutsuaki Murakami, Kanta Adachi, Hirotsugu Ogi

    Physical Review Materials　4　(4)　2020/04/20

    DOI： 10.1103/PhysRevMaterials.4.043603 　

    eISSN： 2475-9953

  25. Elastic constants of beta tungsten thin films studied by picosecond ultrasonics and density functional theory Peer-reviewed

    A. Nagakubo, H. T. Lee, H. Ogi, T. Moriyama, T. Ono

    Applied Physics Letters　116　(2)　021901-021901　2020/01/13

    Publisher: {AIP} Publishing

    DOI： 10.1063/1.5131768 　

    ISSN： 0003-6951

    eISSN： 1077-3118

  26. GHz-range resonant ultrasound spectroscopy for a free-standing nano film studied by picosecond ultrasonics Peer-reviewed

    Akira Nagakubo, Kanta Adachi, Tokihiro Nishihara, Hirotsugu Ogi

    Applied Physics Express　13　(1)　2020/01/01

    DOI： 10.7567/1882-0786/ab600d 　

    ISSN： 1882-0778

    eISSN： 1882-0786

  27. Highly sensitive hydrogen detection using curvature change of wireless-electrodeless quartz resonators Peer-reviewed

    L. Zhou, N. Nakamura, A. Nagakubo, H. Ogi

    Applied Physics Letters　115　(17)　2019/10/21

    DOI： 10.1063/1.5126135 　

    ISSN： 0003-6951

  28. Zero temperature coefficient of sound velocity in vitreous silicon oxynitride thin films Peer-reviewed

    A. Nagakubo, S. Tsuboi, Y. Kabe, S. Matsuda, A. Koreeda, Y. Fujii, H. Ogi

    Applied Physics Letters　114　(25)　2019/06/24

    DOI： 10.1063/1.5098354 　

    ISSN： 0003-6951

  29. Nano-plate biosensor array using ultrafast heat transport through proteins Peer-reviewed

    Hirotsugu Ogi, Shigeru Iwagami, Akira Nagakubo, Takuya Taniguchi, Teruo Ono

    Sensors and Actuators, B: Chemical　278　15-20　2019/01/01

    DOI： 10.1016/j.snb.2018.09.030 　

    ISSN： 0925-4005

  30. Theoretical study on elastic properties of Si<inf>2</inf>N<inf>2</inf>O by ab initio calculation Peer-reviewed

    Seiya Tsuboi, Kanta Adachi, Akira Nagakubo, Hirotsugu Ogi

    Japanese Journal of Applied Physics　57　(7)　2018/07

    DOI： 10.7567/JJAP.57.07LB04 　

    ISSN： 0021-4922

    eISSN： 1347-4065

  31. アモルファス酸窒化シリコン薄膜の音速の温度依存性:ゼロ温度係数の実現

    坪井誠也, 荻博次, 長久保白, 松田聡, 壁義郎, 是枝聡肇, 藤井康裕

    日本物理学会講演概要集(CD-ROM)　73　(2)　2018

    ISSN： 2189-079X

  32. Phonon anharmonicity in zirconium tungstate single crystal investigated by broadband light scattering Peer-reviewed

    Eiichi Oishi, Yasuhiro Fujii, Daisuke Katayama, Akitoshi Koreeda, Akira Nagakubo, Hirotsugu Ogi

    JAPANESE JOURNAL OF APPLIED PHYSICS　56　(10)　2017/10

    DOI： 10.7567/JJAP.56.10PB06 　

    ISSN： 0021-4922

    eISSN： 1347-4065

  33. 超音波探測 斜方晶構造を有する液晶ポリマーの弾性率計測

    長久保 白, 中島 静香, 荻 博次, 太田 晃仁

    超音波techno　29　(5)　99-101　2017/09

    Publisher: 日本工業出版

    ISSN： 0916-2410

  34. タングステン酸ジルコニウムのラマン散乱分光

    大石栄一, 片山大輔, 藤井康裕, 是枝聡肇, 長久保白, 荻博次

    日本物理学会講演概要集(CD-ROM)　72　(1)　2017

    ISSN： 2189-079X

  35. Temperature behavior of sound velocity of SiON thin films studied by picosecond ultrasound Peer-reviewed

    Seiya Tsuboi, Hirotsugu Ogi, Akira Nagakubo, Nobutomo Nakamura, Satoru Matsuda, Yoshiro Kabe

    2017 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS)　2017

    DOI： 10.1109/ULTSYM.2017.8092986 　

    ISSN： 1948-5719

  36. Thermal Mode Spectroscopy for Thermal Diffusivity of Millimeter-Size Solids Peer-reviewed

    Hirotsugu Ogi, Tatsuya Ishihara, Hideshi Ishida, Akira Nagakubo, Nobutomo Nakamura, Masahiko Hirao

    PHYSICAL REVIEW LETTERS　117　(19)　2016/11

    DOI： 10.1103/PhysRevLett.117.195901 　

    ISSN： 0031-9007

    eISSN： 1079-7114

  37. Piezoelectric coefficients of GaN determined by hopping conduction of carriers Peer-reviewed

    K. Adachi, H. Ogi, A. Nagakubo, N. Nakamura, M. Hirao, M. Imade, M. Yoshimura, Y. Mori

    APPLIED PHYSICS LETTERS　109　(18)　2016/10

    DOI： 10.1063/1.4966995 　

    ISSN： 0003-6951

    eISSN： 1077-3118

  38. Elastic constants of GaN between 10 and 305K Peer-reviewed

    K. Adachi, H. Ogi, A. Nagakubo, N. Nakamura, M. Hirao, M. Imade, M. Yoshimura, Y. Mori

    JOURNAL OF APPLIED PHYSICS　119　(24)　2016/06

    DOI： 10.1063/1.4955046 　

    ISSN： 0021-8979

    eISSN： 1089-7550

  39. Elastic constant C-11 of C-12 diamond between 10 and 613 K Peer-reviewed

    A. Nagakubo, M. Arita, H. Ogi, H. Sumiya, N. Nakamura, M. Hirao

    APPLIED PHYSICS LETTERS　108　(22)　2016/05

    DOI： 10.1063/1.4952613 　

    ISSN： 0003-6951

    eISSN： 1077-3118

  40. Impact of interface stiffness in surface-wave resonances on nanostrip-attached substrates Peer-reviewed

    Ogi Hirotsugu, Masuda Shoichi, Nagakubo Akira, Nakamura Nobutomo, Hirao Masahiko, Kondou Kouta, Ono Teruo

    PHYSICAL REVIEW B　93　(2)　2016/01/22

    DOI： 10.1103/PhysRevB.93.024112 　

    ISSN： 1098-0121

    eISSN： 2469-9969

  41. 21aAF-6 A Brillouin scattering study of ZrW_2O_8

    Wani H., Fujii Y., Koreeda A., Nagakubo A., Ogi H.

    Meeting Abstracts of the Physical Society of Japan　71　2694-2694　2016

    Publisher: The Physical Society of Japan (JPS)

    DOI： 10.11316/jpsgaiyo.71.1.0_2694 　

    ISSN： 2189-079X

  42. Stiffness of isotropy controlled diamond studied by picosecond ultrasonics and transmission electron microscope

    (45)　43-45　2016

    Publisher:

  43. Refractive index and extinction coefficient of Si at 400nm between 10 and 300K Peer-reviewed

    Akira Nagakubo, Hirotsugu Ogi, Masahiko Hirao

    JAPANESE JOURNAL OF APPLIED PHYSICS　54　(12)　2015/12

    DOI： 10.7567/JJAP.54.128001 　

    ISSN： 0021-4922

    eISSN： 1347-4065

  44. G213 A large-scale multichannel biosensor using phonon transport through proteins

    Iwagami Shigeru, Ogi Hirotsugu, Nagakubo Akira, Hirao Masahiko, Taniguchi Takuya, Ono Teruo

    Procee[d]ings of Thermal Engineering Conference　2015　"G213-1"-"G213-2"　2015/10/23

    Publisher: The Japan Society of Mechanical Engineers

    More details Close

    Biosensors are important measurement tools for diagnosis and drug discovery. Especially in drug-discovery processes, high-throughput biosensors are required because of many drug candidates. Then we developed a new concept high-throughput biosensor using picosecond ultrasound method. A metal microdot is irradiated with ultrashort optical pulse, where ultrahigh-frequency phonons are excited. They are transferred into the solution across the proteins captured on the microdot, leading to the phonon intensity change. We observe this phenomenon using a time-resolved pump-probe method. We can detect 67 pM rabbit IgG using reflective change caused by phonon intensity change due to protein coupling onto the sensor chip. In addition, we achieved detection of difference between specific binding and non-specific binding using multi-channel microdots. And we developed theoretical calculation for this measurement principle. In this study, Our new concept biosensor can be a powerful tool as a large-scale multichannel biosensor.

  45. Observation abnormal isotope effect on elastic constants in diamond thin films

    ARITA MARI, NAGAKUBO AKIRA, MORIGAMI KENTA, OGI HIROTSUGU, HIRAO MASAHIKO, WATANABE HIDEYUKI

    JSAP Annual Meetings Extended Abstracts　2015.2　340-340　2015/08/31

    Publisher: The Japan Society of Applied Physics

    DOI： 10.11470/jsapmeeting.2015.2.0_340 　

    eISSN： 2436-7613

  46. Acoustic properties of co-doped AlN thin films at low temperatures studied by picosecond ultrasonics Peer-reviewed

    Akira Nagakubo, Mari Arita, Tsuyoshi Yokoyama, Satoru Matsuda, Masanori Ueda, Hirotsugu Ogi, Masahiko Hirao

    JAPANESE JOURNAL OF APPLIED PHYSICS　54　(7)　2015/07

    DOI： 10.7567/JJAP.54.07HD01 　

    ISSN： 0021-4922

    eISSN： 1347-4065

  47. Temperature behavior of sound velocity of fluorine-doped vitreous silica thin films studied by picosecond ultrasonics Peer-reviewed

    A. Nagakubo, H. Ogi, H. Ishida, M. Hirao, T. Yokoyama, T. Nishihara

    JOURNAL OF APPLIED PHYSICS　118　(1)　2015/07

    DOI： 10.1063/1.4923353 　

    ISSN： 0021-8979

    eISSN： 1089-7550

  48. Hopping conduction and piezoelectricity in Fe-doped GaN studied by non-contacting resonant ultrasound spectroscopy Peer-reviewed

    H. Ogi, Y. Tsutsui, N. Nakamura, A. Nagakubo, M. Hirao, M. Imade, M. Yoshimura, Y. Mori

    APPLIED PHYSICS LETTERS　106　(9)　2015/03

    DOI： 10.1063/1.4913973 　

    ISSN： 0003-6951

    eISSN： 1077-3118

  49. Elastic properties of single-crystalline omega phase in titanium (vol 61, pg 7543, 2013) Peer-reviewed

    Tane M, Okuda Y, Todaka Y, Ogi H, Nagakubo A

    ACTA MATERIALIA　84　515　2015/02/01

    DOI： 10.1016/j.actamat.2014.11.006 　

    ISSN： 1359-6454

  50. Erratum: Elastic properties of single-crystalline ω phase in titanium (Acta Materialia 61 (2013) (7543-7554))

    M. Tane, Y. Okuda, Y. Todaka, H. Ogi, A. Nagakubo

    Acta Materialia　84　515　2015/02/01

    DOI： 10.1016/j.actamat.2014.11.006 　

    ISSN： 1359-6454

  51. 3P1-1 Guided wave propagation in a 2-D patterned nano-bridge studied by picosecond ultrasonics Peer-reviewed

    Nagakubo Akira, Iwagami Shigeru, Ogi Hirotsugu, Taniguchi Takuya, Ono Teruo, Hirao Masahiko

    Proceedings of Symposium on Ultrasonic Electronics　36　(0)　_3P1-1-1_-_3P1-1-2_　2015

    Publisher: Institute for Ultrasonic Elecronics

    ISSN： 1348-8236

  52. 1P1-1 Picosecond Ultrasound for Studying Anomalous Temperature Dependence of Elastic Constants of the Negative-Thermal-Expansion Zirconium Tungstate(Poster Session) Peer-reviewed

    Fukazawa Shunsuke, Nagakubo Akira, Ogi Hirotsugu, Hirao Masahiko

    Proceedings of Symposium on Ultrasonic Electronics　35　19-20　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN： 1348-8236

  53. 1P3-3 Acoustic properties of co-doped AlN thin films at low temperatures studied by picosecond ultrasonics(Poster Session) Peer-reviewed

    Nagakubo Akira, Arita Mari, Yokoyama Tsuyoshi, Matsuda Satoru, Ueda Masanori, Ogi Hirotsugu, Hirao Masahiko

    Proceedings of Symposium on Ultrasonic Electronics　35　83-84　2014/12/03

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN： 1348-8236

  54. Elasticity and hardness of nano-polycrystalline boron nitrides: The apparent Hall-Petch effect Peer-reviewed

    A. Nagakubo, H. Ogi, H. Sumiya, M. Hirao

    APPLIED PHYSICS LETTERS　105　(8)　2014/08

    DOI： 10.1063/1.4894377 　

    ISSN： 0003-6951

    eISSN： 1077-3118

  55. Monitoring of Longitudinal-Wave Velocity and Attenuation of SrTiO3 at Low Temperatures Using Picosecond Ultrasound Spectroscopy (vol 51, 07GA09, 2012) Peer-reviewed

    Akira Nagakubo, Akihiro Yamamoto, Kenichi Tanigaki, Hirotsugu Ogi, Nobutomo Nakamura, Masahiko Hirao

    JAPANESE JOURNAL OF APPLIED PHYSICS　53　(5)　2014/05

    DOI： 10.7567/JJAP.53.059201 　

    ISSN： 0021-4922

    eISSN： 1347-4065

  56. Elastic properties of single-crystalline omega phase in titanium Peer-reviewed

    M. Tane, Y. Okuda, Y. Todaka, H. Ogi, A. Nagakubo

    ACTA MATERIALIA　61　(20)　7543-7554　2013/12

    DOI： 10.1016/j.actamat.2013.08.036 　

    ISSN： 1359-6454

    eISSN： 1873-2453

  57. 2E1-1 Acoustic properties of fluorine-doped silica-glass thin films at low temperatures(Physical Acoustics・Acousto-Optics, Piezoelectric Devices) Peer-reviewed

    Nagakubo Akira, Masuda Shoichi, Matsuda Satoru, Ogi Hirotsugu, Hirao Masahiko

    Proceedings of Symposium on Ultrasonic Electronics　34　375-376　2013/11/20

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN： 1348-8236

  58. F124 Development of Thermal Resonance Spectroscopy for Thermal Diffusivity for Small Rectangular Parallelepipeds

    Morigami Kenta, Nagakubo Akira, Ogi Hirotsugu, Ishida Hideshi, Maris Humphrey J., Hirao Masahiko

    Procee[d]ings of Thermal Engineering Conference　2013　177-178　2013/10/18

    Publisher: The Japan Society of Mechanical Engineers

    More details Close

    Thermal conductivity is a crucial value in designing devices, and materials with high thermal conductivity are favorable for wide variety of applications. However, some of those materials are so small that conventional methods fail to measure thermal conductivity precisely. Here, we introduce a new technique for thermal diffusivity measurement, which observes the thermal resonance and is valid for a small specimen such as synthesized diamond. We describe the theory and the experimental method for this technique and present experimental results for small rectangular parallelepiped specimens. The results show quantitative agreement with reported values.

  59. 物性・評価 サブTHz超音波を用いた機能性酸化物の音速・減衰の極低温計測 Invited

    長久保 白, 荻 博次, 平尾 雅彦

    超音波techno　25　(5)　89-92　2013/09

    Publisher: 日本工業出版

    ISSN： 0916-2410

  60. Elastic constants of cubic and wurtzite boron nitrides Peer-reviewed

    A. Nagakubo, H. Ogi, H. Sumiya, K. Kusakabe, M. Hirao

    APPLIED PHYSICS LETTERS　102　(24)　2013/06

    DOI： 10.1063/1.4811789 　

    ISSN： 0003-6951

    eISSN： 1077-3118

  61. 1105 Development of Thermal Resonance Spectroscopy Method for Thermal Conductivity Measurement

    MORIGAMI Kenta, NAGAKUBO Akira, OGI Hirotsugu, ISHIDA Hideshi, HIRAO Masahiko

    2013　(88)　"11-15"　2013/03/16

    Publisher: The Japan Society of Mechanical Engineers

  62. 1J1-1 Precise Measurement of Elastic Constant of Isotopically Controlled Diamond Thin Films using Brillouin Oscillation Method(Physical Acoustics, Acousto-Optics, Piezoelectric Devices) Peer-reviewed

    Morigami Kenta, Nagakubo Akira, Ogi Hirotsugu, Hirao Masahiko, Watanabe Hideyuki, Shikata Shinichi

    Proceedings of Symposium on Ultrasonic Electronics　33　135-136　2012/11/13

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN： 1348-8236

  63. 1P1-9 Sub-terahertz-frequency attenuation and sound velocity of GaN at Cryogenic Temperatures Studied by Picosecond Ultrasound Spectroscopy(Poster Session) Peer-reviewed

    Nagakubo Akira, Tsutsui Yuki, Ogi Hirotsugu, Nakamura Nobutomo, Hirao Masahiko

    Proceedings of Symposium on Ultrasonic Electronics　33　35-36　2012/11/13

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN： 1348-8236

  64. Monitoring of Longitudinal-Wave Velocity and Attenuation of SrTiO3 at Low Temperatures Using Picosecond Ultrasound Spectroscopy Peer-reviewed

    Akira Nagakubo, Akihiro Yamamoto, Kenichi Tanigaki, Hirotsugu Ogi, Nobutomo Nakamura, Masahiko Hirao

    JAPANESE JOURNAL OF APPLIED PHYSICS　51　(7)　2012/07

    DOI： 10.1143/JJAP.51.07GA09 　

    ISSN： 0021-4922

  65. 3Pb1-4 Monitoring of Sound Velocity and Attenuation in SrTiO_3 across the Phase Transition at Low Temperatures using Picosecond Ultrasonics(Poster Session)

    Nagakubo Akira, Yamamoto Akihiro, Ogi Hirotsugu, Hirao Masahiko

    Proceedings of Symposium on Ultrasonic Electronics　32　459-460　2011/11/08

    Publisher: Steering committee of symposium on ultrasonic electronics

    ISSN： 1348-8236

  66. OS02-2-5 Picosecond Ultrasound Spectroscopy for High Purity Boron Nitrides Peer-reviewed

    Nagakubo Akira, Tanigaki Kenichi, Ogi Hirotsugu, Hirao Masahiko, Sumiya Hitoshi, Harano Katsuko

    Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics　2011　(10)　"OS02-2-5-1"　2011/09/19

    Publisher: The Japan Society of Mechanical Engineers

Show all ︎Show first 5

Presentations 39

  1. Early non-destructive detection of electromigration studied by sub-THz ultrasound

    Akira Nagakubo, Shuhei Izuma, Atsushi Nishimura, Yoshiro Kabe, Hirotsugu Ogi

    2024/09/16

  2. In situ monitoring of electromigration in a single nano wire by picosecond ultrasonics

    A. Nagakubo, E. Asanuma, H. Ogi

    184th Meeting of the Acoustical Society of America　2023/05/09

  3. Machine learning prediction of initial values of elastic constants in resonant ultrasound spectroscopy

    Hiroki Fukuda, Akira Nagakubo, Hirotsugu Ogi

    The 43rd Symposium on Ultrasonic Electronics　2022/11/07

  4. Propagation properties of longitudinal wave in defect-free multilayer graphene at low temperatures and high magnetic field

    K. Tojo, A. Nagakubo, M. Tachibana, K. Murashima, M. Murakami, H. Ogi

    The 43rd Symposium on Ultrasonic Electronics　2022/11/07

  5. Effects of Au atoms deposition on Pd film for hydrogen gas sensor using wireless and electrodeless quartz crystal resonator

    T. Matsukura, L. Zhou, A. Nagakubo, H. Ogi

    The 43rd Symposium on Ultrasonic Electronics　2022/11/07

  6. Numerical Study on High Sensitivity Biosensing Scheme Based on Waveguide Phononic Crystal

    W. Yuan, A. Nagakubo, H. Ogi

    The 43rd Symposium on Ultrasonic Electronics　2022/11/07

  7. Shear moduli of liquid crystalline polymers and relaxation process in poly methyl methacrylate studied by resonant ultrasound spectroscopy

    K. Fujita, A. Nagakubo, H. Ogi

    The 43rd Symposium on Ultrasonic Electronics　2022/11/07

  8. GHz phonon biosensor using free-standing SiN nanofilm with real-time monitoring by asynchronous optical sampling picosecond ultrasonics

    A. Nagakubo, A. Tange, H. Ogi

    2022/10/11

  9. Interaction between ultrasound and magnetization in ferromagnetic thin film studied by picosecond ultrasonics

    K. TojoA, Nagakubo, H. Ogi

    The 42nd Symposium on Ultrasonic Electronics　2021/10/25

  10. Elastic constants of tungsten carbide single crystal studied by picosecond ultrasonics

    M. KimotoA, Nagakubo, H. Ogi

    The 42nd Symposium on Ultrasonic Electronics　2021/10/25

  11. Development of nano-thin film biosensors using asynchronous picosecond ultrasound method

    A. Tange, A. Nagakubo, H. Ogi

    The 42nd Symposium on Ultrasonic Electronics　2021/10/25

  12. Acoustic properties of metal/antiferromagnet epitaxial multilayers

    H. Fukuda, A. Nagakubo, H. Ogi

    The 41st Symposium on Ultrasonic Electronics　2020/11/25

  13. Relationship between Temperature Coefficient of Sound Velocity and Bond Angle in Vitreous SiO2-Type Films

    A. Nagakubo, H. Ogi, S. Tsuboi, A. Koreeda, Y. Fujii

    2019 IEEE International Ultrasonics Symposium　2019/10/06

  14. Time-range controllable asynchronous picosecond ultrasonics with titanium-sapphire pulse lasers

    A. Nagakubo, H. Tamura, H. Ogi

    2019 International Congress on Ultrasonics　2019

  15. Resonance frequencies of AlN and metal freestanding multilayers studied by picosecond ultrasonics

    A. Nagakubo, T. Nishihara, H. Ogi

    The 39th Symposium on Ultrasonic Electronics　2018/10/29

  16. ピコ秒超音波法を用いたa及びb型タングステンナノ薄膜の弾性率計測および重水素照射による機械特性の変化

    長久保 白, 土生 善昭, Lee Heun Tae, 上田 良夫, 荻 博次

    2018/09/18

  17. Guide wave excitation and detection in a single nanowire

    A. Nagakubo, T. Taniguchi, H. Ogi, T. Ono

    2017 International Congress on Ultrasonics　2017/12/18

  18. Elastic constant of alpha and beta tungsten films studied by picosecond ultrasonics

    A. Nagakubo, Lee Heun Tae, Y. Ueda, H. Ogi, T. Moriyama, T. Ono

    The 38th Symposium on Ultrasonic Electronics　2017/10/25

  19. Discussion on very small temperature dependence of diamond's elastic constants

    A. Nagakubo, H. Ogi, M. Hirao

    5th Joint Meeting of the Acoustical Society of America and Acoustical Society of Japan　2016/11/28

  20. Wave-propagation properties of alpha and beta Lanthanum studied by ab-initio calculations

    A. Nagakubo, H. Ogi, K. Kusakabe, M. Hirao

    The 37th Symposium on Ultrasonic Electronics　2016/11/16

  21. Guided wave propagation in a 2-D patterned nano-bridge studied by picosecond ultrasonics

    A. Nagakubo, S. Iwagami, H. Ogi, T. Taniguchi, T. Ono, M. Hirao

    The 36th Symposium on Ultrasonic Electronics　2015/11/05

  22. The apparent Hall-Petch effect of nano-polycrystalline cubic boron nitrides

    A. Nagakubo, K. Tanigaki, H. Ogi, M. Hirao, H. Sumiya

    9th International Conference on New Diamond and Nano Carbons 2015　2015/05/24

  23. Elasticity measurements by Picosecond ultrasound spectroscopy Invited

    A. Nagakubo, H. Ogi, M. Hirao

    Seminor in Academy of Sciences of the Czech Republic　2015/05/18

  24. Precise measurement of sound velocity of amorphous silica at low temperatures by picosecond ultrasounds: correction of static heating effect

    A. Nagakubo, H. Ishida, H. Ogi, M. Hirao

    2015 International Congress on Ultrasonics　2015/05/10

  25. Elastic stiffness of cubic and wurtzite boron nitride

    A. Nagakubo, K. Tanigaki, H. Ogi, M. Hirao, H. Sumiya

    TMS (The Minerals, Metals and Materials Society) 2015, 144th annual Meeting　2015/03/15

  26. 極低温ピコ秒超音波法を用いた異なるキャリア密度のGaNに対するキャリアダイナミクスの観測 Invited

    長久保 白, 石原 達也, 荻 博次, 中村 暢伴, 平尾 雅彦

    第62回 応用物理学会春季学術講演会　2015/03/10

  27. Acoustic properties of co-doped AlN thin films at low temperatures studied by picosecond ultrasonics

    A. Nagakubo, M. Arita, T. Yokoyama, S. Matsuda, M. Ueda, H. Ogi, M. Hirao

    The 35th Symposium on Ultrasonic Electronics　2014/12/03

  28. 極低温ピコ秒超音波法を用いたGaNのキャリアダイナミクスの観測と圧電定数計測

    長久保 白, 石原 達也, 荻 博次, 中村 暢伴, 平尾 雅彦

    第75回 応用物理学会学術講演会　2014/09/17

  29. Temperature coefficients of fluorine-doped amorphous-SiO2 thin films measured by picosecond ultrasonics

    A. Nagakubo, S. Matsuda, H. Ogi, M. Hirao

    2014 IEEE International Ultrasonics Symposium

  30. Measurement and Calculation of Elastic Constants of Boron Nitrides

    A. Nagakubo, K. Tanigaki, H. Ogi, M. Hirao, H. Sumiya

    2013 International Congress on Ultrasonics

  31. Acoustic properties of fluorine-doped silica-glass thin films at low temperatures

    A. Nagakubo, S. Masuda, S. Matsuda, H. Ogi, M. Hirao

    The 34th Symposium on Ultrasonic Electronics

  32. Sub-terahertz-frequency attenuation and sound velocity of GaN at Cryogenic Temperatures Studied by Picosecond Ultrasound Spectroscopy

    A. Nagakubo, Y. Tsutsui, H. Ogi, N. Nakamura, M. Hirao

    The 33rd Symposium on Ultrasonic Electronics

  33. 極低温域における圧電体・誘電体に対するサブTHz超音波の減衰計測

    長久保 白, 筒井 裕貴, 荻 博次, 中村 暢伴, 平尾 雅彦

    第73回 応用物理学会学術講演会

  34. Study of Phase Transition in SrTiO3 Using Ultrasonic Attenuation at Sub-Terahertz Region

    A. Nagakubo, H. Ogi, M. Hirao

    Quantitative Nondestructive Evaluation (QNDE) 2012

  35. Elastic Constants of Boron Nitrides at Cryogenic Temperature

    A. Nagakubo, K. Tanigaki, H. Ogi, M. Hirao, H. Sumiya, K. Harano

    Materials Research Society(MRS) Fall Meeting 2011

  36. Monitoring of sound velocity and attenuation in SrTiO3 across the phase transition at low temperature using picosecond ultrasonics

    A. Nagakubo, A. Yamamoto, H. Ogi, M. Hirao

    The 32nd Symposium on Ultrasonic Electronics

  37. Picosecond Ultrasound Spectroscopy for High Purity Boron Nitrides

    A. Nagakubo, K. Tanigaki, H. Ogi, M. Hirao, H. Sumiya, K. Harano

    International Conference on Advanced Technology in Experimental Mechanics 2011 The 10 th Annual Conference of the Asian Society

  38. Elasticity of High Purity Boron Nitrides at Cryogenic Temperatures Studied by Picosecond Laser Ultrasound and ab-initio Calculation

    A. Nagakubo, K. Tanigaki, H. Ogi, M. Hirao, H. Sumiya, K. Harano

    5th International Conference on New Diamond and Nano Carbons 2011

  39. 高純度BN多結晶体の超高弾性とその極低温計測:ピコ秒超音波計測と第一原理計算

    長久保 白, 谷垣 健一, 森田 啓, 荻 博次, 平尾 雅彦, 角谷 均, 原野 佳津子

    第58回 応用物理学関係連合講演会

Show all Show first 5

Research Projects 11

  1. Development of the extreme ultrasonics in the nm/sub-THz region

    Akira Nagakubo

    Offer Organization: Japan Science and Technology Agency

    System: Fusion Oriented Research for disruptive Science and Technology

    Institution: Osaka University

    2022/01 - 2029/03

  2. The mechanism of electromigration studied by real-time ultrasound monitoring for single nanowire

    Akira Nagakubo

    Offer Organization: Japan Society for the Promotion of Science

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

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Osaka University

    2022/04 - 2026/03

  3. Development of highly sensitive real-time monitoring biosensors using asynchronous optical sampling picosecond ultrasonics

    Akira Nagakubo

    Offer Organization: Japan Society for the Promotion of Science

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

    Category: Grant-in-Aid for Challenging Research (Exploratory)

    Institution: Osaka University

    2022/06 - 2024/03

  4. Understanding the synthesis and electronic behavior of beta tungsten thin film materials

    Offer Organization: Japan Society for the Promotion of Science

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

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Osaka University

    2020/04 - 2024/03

  5. ナノ薄膜炭素材料のフォノン物性学理の深化

    荻 博次, 草部 浩一, 渡邊 幸志, 長久保 白

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業 基盤研究(A)

    Category: 基盤研究(A)

    Institution: 大阪大学

    2019/04 - 2023/03

    More details Close

    ナノダイヤモンド薄膜や多層グラフェン等のナノ炭素材料は、極めて高い弾性率や熱伝導率を示す。その優れたフォノン物性を利用した実用研究が加速する一方、フォノン物性の基礎的理解が追随しているとは言い難い。本年度は、同位体比を制御したホモエピタキシャルダイヤモンド薄膜およびホモエピタキシャルダイヤモンド超格子薄膜に対して、顕微ピコ秒レーザー超音波法を用いて、膜厚方向の熱拡散率の評価を行った。通常の理論では説明することのできないフォノン特性が観測された。この成果は、Japanese Journal of Applied Physics に掲載された。また、無欠陥のグラファイト単結晶を作製することに成功し、この試料に対して顕微ピコ秒レーザー超音波法により、c軸方向の弾性定数を正確に評価したところ、従来信じられていた値よりも大幅に高いことが判明した。さらに、理論的に短距離電子相関効果から非調和性が強まることを発見し、この実験値を再現することに成功した。これはグラファイトの弾性定数を再現すると信じられていた乱雑位相近似を用いる理論計算に変更が必要であることを強く示す結果である。この成果により、ファンデルワールス力に潜む量子効果がさらに深く理解されることが期待できる。これらの成果は、Physical Review Materialsに掲載された。

  6. Spin dynamics in antiferromagnetic nanofilms studied by phonon-magnon interaction

    Nagakubo Akira

    Offer Organization: Japan Society for the Promotion of Science

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

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Osaka University

    2018/04 - 2022/03

    More details Close

    In this study, we studied the fundamental phono properties of NiO and the interaction between magnon and GHz-range longitudinal phonon to reveal and apply the phonon-magnon coupling in antiferromagnets. Our measurement for Pt/NiO/Pt nanofilms revealed that the elastic constant of NiO largely changes depending on deposition conditions and substrates. From ultrasound resonance spectroscopy measurement for a single bulk crystal, we also found that the antiferromagnetic order seriously affects the phonon properties, which change with deformation modes. These results will contribute to further study and application of the phonon properties of antiferromagnetic films.

  7. Development of shear-wave picosecond ultrasonics using hotelectrons in a nanowire

    Nagakubo Akira

    Offer Organization: Japan Society for the Promotion of Science

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

    Category: Grant-in-Aid for Challenging Research (Exploratory)

    Institution: Osaka University

    2019/06 - 2021/03

    More details Close

    Picosecond ultrasonics has been developed and applied to a wide range of acoustic physics. However, shear wave can be excited only in some piezoelectric materials and unique-angle crystals. Therefore, we develop a new shear-wave picosecond ultrasonic method for usual materials. By changing the irradiation conditions of electron beam lithography, we fabricated original designed nanowires, which have the minimum width of 100 nm. We succeeded in exciting and observing high frequency longitudinal waves on 500-nm nanowires. Under a perpendicular magnetic field, we changed the irradiation position of pump light on the nanowire and changed the incident angle of probe light to excite and detect shear wave. We obtained a 68-GHz peak, which corresponds to the Brillouin-oscillation frequency of shear wave in strontium titanate.

  8. 高い時空間分解能を持つ超音波計測法と微細加工技術を融合した磁性ナノデバイスの開発

    長久保 白

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業 特別研究員奨励費

    Category: 特別研究員奨励費

    Institution: 京都大学

    2017/04 - 2020/03

    More details Close

    本研究ではフェムト秒パルスレーザーを用いた超高速ポンププローブ計測法と電子線リソグラフィを用いたナノメートルオーダーの微細加工技術を組み合わせ、フォノン(超音波)による磁壁の移動現象の実験的解明を目指して研究を行った。電子線リソグラフィを用いることで独自に提案した形状のデバイスを作製し、ナノワイヤの方端部にポンプ光を照射して超音波を励起し、もう一端まで伝播してきた超音波をプローブ光の反射率変化を通して検出することに成功した。その計測の結果、ナノワイヤ中を伝わる2つの現象を発見した。1つはポンプ光の照射後、100 ps以内に数ミクロンの距離を伝播するパルス的な応答である。もう1つは1000 ps以上経ってから数ミクロンの距離を伝播してくる振動的な応答である。細線の材料や寸法を変えるとパルス応答の振幅や、振動の周波数や伝播時間にも変化が現れた。これらは細線中を伝わる電子や超音波の応答を捉えていると考えられ、今後これを用いることで磁壁の移動現象の実験へとつなげることが可能となった。 また光学系を改築し、磁気光学Kerr効果をピコ秒オーダーにおいてとらえることで磁化の超高速動的挙動も観測することができるようになった。本研究で構築した光学系では、検出光の分離方法を変えるだけで同一の励起条件下における磁化の応答と超音波の応答をそれぞれ独立に計測できる。これにより超音波の挙動と磁壁・磁化振動の挙動を時間領域において計測できるようになり、これらの相互作用を解明することができるようになった。

  9. Physical properties of isotope diamond looking for further light element materials

    Shikata Shinichi, Watanabe Hideyuki, Kushibiki Junichi, Tanno Takenori, Ogi Hirotugu, Nagakubo Akira, Majdi Saman

    Offer Organization: Japan Society for the Promotion of Science

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

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Kwansei Gakuin University

    2016/04 - 2019/03

    More details Close

    In this study, we have focused on the physical properties of diamond which has a large influence on characteristics by isotope purification. High concentration of oxygen was applied to grow isotopically controlled diamond, and successfully obtained high quality 12C freestanding crystals. Regarding elastic properties, the ultra-precise lattice constant measurements were carried out for isotopically-enriched crystal by four-crystal symmetric reflection type X-ray diffraction. Also, the measurement using the Brillouin vibration method was performed to obtain the precise elastic constant of isotopically-enriched crystal. We have conducted photoluminescence and differential absorption spectroscopy under uniaxial stress at cryogenic temperatures and observed that free exciton transitions in 12Ccrystal are split by uniaxial stress for the first time. We also have succeeded in precise identification of the 12C and 13C bandgap difference and the isotope effect on phonons and excitons.

  10. Sound velocity, refractive index, and thickness measurement of thin films below room temperature.

    Nagakubo Akira

    Offer Organization: Japan Society for the Promotion of Science

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

    Category: Grant-in-Aid for Young Scientists (B)

    Institution: Osaka University

    2015/04 - 2017/03

    More details Close

    In this study, I have developed a method to accurately measure the sound velocity of functional materials, which are widely used in wireless communication devices such as cell phone. Using home built optics, I succeeded in observing ultrasound propagations in micro-order films with two different incident angle, which enable me to measure the sound velocity, refractive index, and film thickness of the film at the same time. Furthermore, I have measured the temperature dependence of acoustic properties of functional materials such as AlN and diamond. These results contribute to device design and give many important knowledge for material science.

  11. サブTHz超音波を用いた物質の弾性と機能との強相関の究明

    長久保 白

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業 特別研究員奨励費

    Category: 特別研究員奨励費

    Institution: 大阪大学

    2012/04 - 2015/03

    More details Close

    今年度は本研究の最終年度として今までの研究成果の論文執筆・学会発表に努めた。その中でダイヤモンドに次ぐ高硬度材料として知られる窒化ホウ素の硬度が測定法によっては弾性率の影響を受けて過大評価されてしまうことを示した。これは超硬材料の硬度測定法に関して重要な指針である。なぜなら近年、窒化ホウ素の硬度がダイヤモンドの硬度を上回るという報告や、従来のダイヤモンドの2倍以上の硬度を誇るダイヤモンドの合成に成功したという報告がなされており、硬度の計測法自体に疑問がもたれているからである。 またフッ素を添加した石英ガラス薄膜の音速の温度依存性がバルクよりも小さく、また石英ガラスの熱伝導率の低さによってレーザー加熱の影響が無視できないということを示した。石英ガラス薄膜は携帯電話など無線通信デバイスで特製周波数の電波を受信するための音響フィルタ中で温度補償材として使用されている。しかしその薄膜の特性を直接計測することは従来法では困難であり、音速の絶対値やその温度係数などは未知のままであった。本研究は初めてそれを直接計測することに成功し、デバイス開発やガラス薄膜の音響特性の解明に大きく貢献した。 音響フィルタ中では電波信号を音響信号に変換する素子として窒化アルミニウム(AlN)などの圧電体が使用されており、マグネシウムとハフニウムまたはジルコニウムを添加したAlN薄膜の音速計測も行った。これは信号変換効率を上昇させるために新たに作成された材料であり、デバイスとして実用化するためには音響特性の解明が欠かせない。計測の結果、異種元素を約10％添加することで音速が10％以上低下することを解明した。 以上の結果はすべて今年度に学会で発表または論文として執筆を行った。

Show all Show first 5

Teaching Experience 11

  1. Experiments in Precision Science and Technology　Osaka University

  2. Introduction to Advanced Sciences II　Osaka University

  3. Seminar III　Osaka University

  4. Seminar II　Osaka University

  5. Seminar in Precision Science and Technology　Osaka University

  6. Exercises in Mathematical Analysis II　Osaka University

  7. Exercises in Mathematical Analysis I　Osaka University

  8. A Door to Academia　Osaka University

  9. Basic Physics Experiments　Osaka University

  10. Synthetic Exercises in Mechanical Engineering　Osaka University

  11. Experiments in Mechanical Engineering　Osaka University

Show all Show first 5