2023
Zero-dimensionality of a scaled-down VO2 metal-insulator transition via high-resolution electrostatic gating
Takeaki Yajima, Yusuke Samata, Satoshi Hamasuna, Satya Prakash Pati, Akira Toriumi
NPG Asia Materials, 15 39-1-39-6, Jun, 2023
CMOS-based area-and-power-efficient neuron and synapse circuits for time-domain analog spiking neural networks
Xiangyu Chen, Zolboo Byambadorj, Takeaki Yajima, Hisashi Inoue, Isao H. Inoue, Tetsuya Iizuka
Applied Physics Letters, 122 074102, Feb, 2023
2022
Controlling proton volatility in SiO2-capped TiO2 thin films for neuromorphic functionality [Editor’s Pick]
T. Yajima, S. P. Pati
Applied Physics Letters, 120(24) 241601-241601, Jun 13, 2022
Self-synchronized Rectifier with Phase Information Extracted from Vibration Energy Harvester
Hang Yin, Takeaki Yajima
Sensors and Materials, 34(5) 1899-1907, May, 2022
An ultra-compact leaky integrate-and-fire neuron with long and tunable time constant utilizing pseudo resistors for spiking neural networks
Xiangyu Chen, Takeaki Yajima, Isao H. Inoue, Tetsuya Iizuka
Japanese Journal of Applied Physics, 61(SC) SC1051-SC1051, May 1, 2022
Ultra-low-power switching circuits based on a binary pattern generator with spiking neurons
Takeaki Yajima
Scientific Reports, 12 1150, Jan, 2022
Kyushu University Pre-release , JST Pre-release , JST news Apr. , ihon Keizai Shimbun(Japanese newspaper) , Science Japan
2021
Observation of the Pinch‐Off Effect during Electrostatically Gating the Metal‐Insulator Transition
Takeaki Yajima, Akira Toriumi
Advanced Electronic Materials, 2100842-2100842, Nov 21, 2021
Temperature dependence of resistivity increases induced by thiols adsorption in gold nanosheets
Taro Kato, Takahisa Tanaka, Takeaki Yajima, Ken Uchida
Japanese Journal of Applied Physics, 60(SB) SBBH13-SBBH13, Feb 3, 2021
Atomistic simulation study of impacts of surface carrier scatterings on carrier transport in Pt nanosheets
Takahisa Tanaka, Taro Kato, Takeaki Yajima, Ken Uchida
IEEE Electron Device Letters, 1-1, 2021
2020
Regulating phase transformation kinetics via redox reaction in ferroelectric Ge-doped HfO2
T. Yajima, T. Nishimura, S. Migita, T. Tanaka, K. Uchida, A. Toriumi
Applied Physics Letters, 117(18) 182902-182902, Nov 2, 2020
Modulation of VO 2 Metal–Insulator Transition by Ferroelectric HfO 2 Gate Insulator
Takeaki Yajima, Tomonori Nishimura, Takahisa Tanaka, Ken Uchida, Akira Toriumi
Advanced Electronic Materials, 6(5) 1901356-1901356, May, 2020
Impact of defects in self-assembled monolayer on humidity sensing by molecular functionalized transistors
T. Tanaka, T. Yajima, K. Uchida
Jpn. J. Appl. Phys., Mar, 2020
Understanding of Fermi level pinning at metal/germanium interface based on semiconductor structure
X. Lu, T. Nishimura, T. Yajima, A. Toriumi
APEX, 13 031003, Mar, 2020
Reaction of GeO2 with Ge and crystallization of GeO2 on Ge
M. Xie, T. Nishimura, T. Yajima, A. Toriumi
J. Appl. Phys., 127 024101, Feb, 2020
Study on Circuit Technologies Using Metal-Insulator Transition Materials
Takeaki Yajima
IEICE JPN Ed., J103-C(10) 420-427, 2020
2019
Heteroepitaxial vertical perovskite hot-electron transistors down to the monolayer limit.
B. Kim, Y. Hikita, T. Yajima, H. Hwang
Nature Commun., 10 5312, Dec, 2019
High-speed low-energy heat signal processing via digital-compatible binary switch with metal-insulator transitions.
T. Yajima, T. Tanaka, Y. Samata, K. Uchida, A. Toriumi
International Electron Devices Meeting (IEDM), 903-906, Dec, 2019
Electron‐Doping Mottronics in Strongly Correlated Perovskite
J. Chen, W. Mao, L. Gao, F. Yan, T. Yajima, N. Chen, Z. Chen, H. Dong, B. Ge, P. Zhang, X. Cao, M. Silde, Y. Jiang, T. Terai, J. Shi
Adv. Mater., 32(6) 1905060, Dec, 2019
Almost pinning-free bismuth/Ge and/Si interfaces
Tomonori Nishimura, Xuan Luo, Soshi Matsumoto, Takeaki Yajima, Akira Toriumi
AIP ADVANCES, 9(9), Sep, 2019
Delta-temperatural electronic transportation achieved in metastable perovskite rare-earth nickelate thin films
Chen Jikun, Hu Haiyang, Yajima Takeaki, Wang Jiaou, Ge Binghui, Dong Hongliang, Jiang Yong, Chen Nuofu
JOURNAL OF MATERIALS CHEMISTRY C, 7(26) 8101-8108, Jul 14, 2019
Overcoming synthetic metastabilities and revealing metal-to-insulator transition & thermistor bi-functionalities for d-band correlation perovskite nickelates
Chen Jikun, Hu Haiyang, Wang Jiaou, Yajima Takeaki, Ge Binghui, Ke Xinyou, Dong Hongliang, Jiang Yong, Chen Nuofu
MATERIALS HORIZONS, 6(4) 788-795, Apr, 2019
2018
Inhomogeneous barrier heights at dipole-controlled SrRuO3/Nb:SrTiO3 Schottky junctions
T. Yajima, M. Minohara, C. Bell, H. Y. Hwang, Y. Hikita
Applied Physics Letters, 11 221603, Nov 26, 2018
Hydrogenation of the wide-gap oxide semiconductor as a room-temperature and 3D-compatible electron doping technique.
T. Yajima, G. Oike, S. Yamaguchi, S. Miyoshi, T. Nishimura, A. Toriumi
AIP Advances, 8 115133, Sep, 2018
Analog Spike Processing with High Scalability and Low Energy Consumption Using Thermal Degree of Freedom in Phase Transition Materials.
T. Yajima, T. Nishimura, and A, Toriumi
VLSI (Technology), 18 27-28, Jul, 2018
Evolution of ferroelectric HfO2 in ultrathin region down to 3 nm
Xuan Tian, Shigehisa Shibayama, Tomonori Nishimura, Takeaki Yajima, Shinji Migita, Akira Toriumi
Applied Physics Letters, 112(10), Mar 5, 2018
Rigidity enhancement of GeO2by Y doping for reliable Ge gate stacks
Tomonori Nishimura, Xiaoyu Tang, Takeaki Yajima, Akira Toriumi
Electron Devices Technology and Manufacturing Conference (EDTM), Mar, 2018
Potential Influence of Surface Atomic Disorder on Fermi-level Pinning at Metal/SiGe Interface
X Luo, T Nishimura, T Yajima, A Toriumi
Electron Devices Technology and Manufacturing (EDTM), Mar, 2018
Anomalous Spectral Shape Evolution of Ge Raman Shift in Oxidation of SiGe.
Y Noma, W Song, T Nishimura, T Yajima, A Toriumi
IEEE Electron Devices Technology and Manufacturing (EDTM), Mar, 2018
Strain Tuning in Complex Oxide Epitaxial Films Using an Ultrathin Strontium Aluminate Buffer Layer
Di Lu, Yasuyuki Hikita, David J. Baek, Tyler A. Merz, Hiroki Sato, Bongju Kim, Takeaki Yajima, Christopher Bell, Arturas Vailionis, Lena F. Kourkoutis, Harold Y. Hwang
Physica Status Solidi – Rapid Research Letters, 12(3), Mar 1, 2018
Rigidity Enhancement of GeO2 by Y-Doping for Reliable Ge Gate Stacks
Nishimura Tomonori, Tang Xiaoyu, Lu Cimang, Yajima Takeaki, Toriumi Akira
IEEE JOURNAL OF THE ELECTRON DEVICES SOCIETY, 6(1) 1207-1212, Mar, 2018
Sub-nm EOT ferroelectric HfO2 on p+Ge with highly reliable field cycling properties
X. Tian, L. Xu, S. Shibayama, T. Nishimura, T. Yajima, S. Migita, A. Toriumi
Technical Digest – International Electron Devices Meeting, IEDM, 17 37.1.1-37.1.4, Jan 23, 2018
2017
Dipole-correlated carrier transportation and orbital reconfiguration in strain-distorted SrNbxTi1-xO3/KTaO3
Jikun Chen, Xinyou Ke, Jiaou Wang, Takeaki Yajima, Haijie Qian, Song Sun
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 19(44) 29913-29917, Nov, 2017
Kinetic pathway of the ferroelectric phase formation in doped HfO2 films
Lun Xu, Tomonori Nishimura, Shigehisa Shibayama, Takeaki Yajima, Shinji Migita, Akira Toriumi
JOURNAL OF APPLIED PHYSICS, 122(12), Sep, 2017
Thermal oxidation kinetics of germanium
X. Wang, T. Nishimura, T. Yajima, A. Toriumi
APPLIED PHYSICS LETTERS, 111(5) 052101, Jul, 2017
n(+)Si/pGe Heterojunctions Fabricated by Low Temperature Ribbon Bonding With Passivating Interlayer
Tony Chi Liu, Shoichi Kabuyanagi, Tomonori Nishimura, Takeaki Yajima, Akira Toriumi
IEEE ELECTRON DEVICE LETTERS, 38(6) 716-719, Jun, 2017
Thermodynamic understanding and analytical modeling of interfacial SiO2 scavenging in HfO2 gate stacks on Si, SiGe, and SiC
Xiuyan Li, Takeaki Yajima, Tomonori Nishimura, Akira Toriumi
APPLIED PHYSICS LETTERS, 110(14), Apr, 2017
Ultrahigh Thermoelectric Performance in SrNb0.2Ti0.8O3 Oxide Films at a Submicrometer-Scale Thickness
Jikun Chen, Hongyi Chen, Feng Hao, Xinyou Ke, Nuofu Chen, Takeaki Yajima, Yong Jiang, Xun Shi, Kexiong Zhou, Max Dobeli, Tiansong Zhang, Binghui Ge, Hongliang Dong, Huarong Zeng, Wenwang Wu, Lidong Chen
ACS ENERGY LETTERS, 2(4) 915-921, Apr, 2017
Identifying the Collective Length in VO2 Metal-Insulator Transitions
Takeaki Yajima, Tomonori Nishimura, Akira Toriumi
SMALL, 13(12), Mar, 2017
General relationship for cation and anion doping effects on ferroelectric HfO2 formation
L. Xu, S. Shibayama, K. Izukashi, T. Nishimura, T. Yajima, S. Migita, A. Toriumi
Technical Digest – International Electron Devices Meeting, IEDM, 25.2.1-25.2.4, Jan 31, 2017
Functional passive material VO2 for analogue signal processing with high-speed, low power, and robust performance
T. Yajima, T. Nishimura, A. Toriumi
Technical Digest – International Electron Devices Meeting, IEDM 34.4.1 – 34.4.4 Jan 31, 2017
Local, Isotropic, and Damageless Doping to Oxide Semiconductors by Using Electrochemistry
Takeaki Yajima, Tomonori Nishimura, Akira Toriumi
2017 IEEE ELECTRON DEVICES TECHNOLOGY AND MANUFACTURING CONFERENCE (EDTM), 80-81, 2017
Reconsideration of Metal Work Function at Metal/Semiconductor Interface
Nishimura Tomonori, Yajima Takeaki, Toriumi Akira
SEMICONDUCTOR PROCESS INTEGRATION 10, 80(4) 107-112, 2017
2016
Ferroelectric phase stabilization of HfO2 by nitrogen doping
Lun Xu, Tomonori Nishimura, Shigehisa Shibayama, Takeaki Yajima, Shinji Migita, Akira Toriumi
APPLIED PHYSICS EXPRESS, 9(9), Sep, 2016
Ferroelectricity of nondoped thin HfO2 films in TiN/HfO2/TiN stacks
Tomonori Nishimura, Lun Xu, Shigehisa Shibayama, Takeaki Yajima, Shinji Migita, Akira Toriumi
JAPANESE JOURNAL OF APPLIED PHYSICS, 55(8), Aug, 2016
Anomalous electrical properties of Au/SrTiO3 interface
Lun Xu, Takeaki Yajima, Tomonori Nishimura, Akira Toriumi
JAPANESE JOURNAL OF APPLIED PHYSICS, 55(8), Aug, 2016
Reexamination of Fermi level pinning for controlling Schottky barrier height at metal/Ge interface
Tomonori Nishimura, Takeaki Yajima, Akira Toriumi
APPLIED PHYSICS EXPRESS, 9(8), Aug, 2016
Independent control of phases and defects in TiO2 thin films for functional transistor channels
Takeaki Yajima, Go Oike, Tomonori Nishimura, Akira Toriumi
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 213(8) 2196-2202, Aug, 2016
General relationship for cation and anion doping effects on ferroelectric HfO2 formation
L. Xu, S. Shibayama, K. Izukashi, T. Nishimura, T. Yajima, S. Migita, A. Toriumi
2016 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM), 16 608-611, 2016
Functional Passive Material VO2 for Analogue Signal Processing with High-Speed, Low Power, and Robust Performance
T. Yajima, T. Nishimura, A. Toriumi
2016 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM), 16 858-861, 2016
Experimental evidence of zone-center optical phonon softening by accumulating holes in thin Ge
Shoichi Kabuyanagi, Tomonori Nishimura, Takeaki Yajima, Akira Toriumi
AIP ADVANCES, 6(1), Jan, 2016
2015
Positive-bias gate-controlled metal-insulator transition in ultrathin VO2 channels with TiO2 gate dielectrics
Takeaki Yajima, Tomonori Nishimura, Akira Toriumi
NATURE COMMUNICATIONS, 6, Dec, 2015
Study of Si kinetics in interfacial SiO2 scavenging in HfO2 gate stacks
Xiuyan Li, Takeaki Yajima, Tomonori Nishimura, Akira Toriumi
APPLIED PHYSICS EXPRESS, 8(6), Jun, 2015
Nondestructive characterization of oxide/germanium interface by direct-gap photoluminescence analysis
Shoichi Kabuyanagi, Tomonori Nishiumura, Takeaki Yajima, Akira Toriumi
APPLIED PHYSICS EXPRESS, 8(5), May, 2015
Drastic change in electronic domain structures via strong elastic coupling in VO2 films
Takeaki Yajima, Yuma Ninomiya, Tomonori Nishimura, Akira Toriumi
PHYSICAL REVIEW B, 91(20), May, 2015
Analytical Formulation of SiO<inf>2</inf>-IL scavenging in HfO<inf>2</inf>/SiO<inf>2</inf>/Si gate stacks – A key is the SiO<inf>2</inf>/Si interface reaction
Xiuyan Li, Takeaki Yajima, Tomonori Nishimura, Kosuke Nagashio, Akira Toriumi
Technical Digest – International Electron Devices Meeting, IEDM, 2015-(February) 21.2.1-21.2.4, Feb 20, 2015
Enhanced Electrical Transparency by Ultrathin LaAlO3 Insertion at Oxide Metal/Semiconductor Heterointerfaces
Yajima, Takeaki, Minohara, Makoto, Bell, Christopher, Kumigashira, Hiroshi, Oshima, Masaharu, Hwang, Harold Y., Hikita, Yasuyuki
Nano Letters, 15(3) 1622-1626, 2015
Controlling band alignments by artificial interface dipoles at perovskite heterointerfaces
Yajima, Takeaki, Hikita, Yasuyuki, Minohara, Makoto, Bell, Christopher, Mundy, Julia A., Kourkoutis, Lena F., Muller, David A., Kumigashira, Hiroshi, Oshima, Masaharu, Hwang, Harold Y.
Nature Communications, 6, 2015
Significance of Kinetic-linkage of Oxygen Vacancy with SiO2/Si Interface for SiO2-IL Scavenging in HfO2 Gate Stacks
Xiuyan Li, Takeaki Yajima, Tomonori Nishimura, Akira Toriumi
2015 SILICON NANOELECTRONICS WORKSHOP (SNW), 2015
Effect of Free Carrier Accumulation or Depletion on Zone-center Vibrational Mode in Ge
Shoichi Kabuyanagi, Tomonori Nishimura, Takeaki Yajima, Akira Toriumi
2015 SILICON NANOELECTRONICS WORKSHOP (SNW), 2015
Recent Progress of Junction Technology for Germanium CMOS
Tomonori Nishimura, Choong Hyun Lee, Toshimitsu Nakamura, Takeaki Yajima, Kosuke Nagashio, Koji Kita, Akira Toriumi
2015 15TH INTERNATIONAL WORKSHOP ON JUNCTION TECHNOLOGY (IWJT), 65-68, 2015
Gate-bias dependent phonon softening observed in Ge MOSFETs
Shoichi Kabuyanagi, Tomonori Nishimura, Takeaki Yajima, Akira Toriumi
ECS Transactions, 69(10) 75-80, 2015
2014
Effect of Si substrate on interfacial SiO2 scavenging in HfO2/SiO2/Si stacks
Xiuyan Li, Takeaki Yajima, Tomonori Nishimura, Kosuke Nagashio, Akira Toriumi
APPLIED PHYSICS LETTERS, 105(18), Nov, 2014
Atomically flat planarization of Ge(100), (110), and (111) surfaces in H-2 annealing
Tomonori Nishimura, Shoichi Kabuyanagi, Wenfeng Zhang, Choong Hyun Lee, Takeaki Yajima, Kosuke Nagashio, Akira Toriumi
APPLIED PHYSICS EXPRESS, 7(5), May, 2014
HfO2-assisted SiO2 reduction in HfO2/SiO2/Si stacks
Xiuyan Li, Takeaki Yajima, Tomonori Nishimura, Kosuke Nagashio, Akira Toriumi
THIN SOLID FILMS, 557 272-275, Apr, 2014
Visualizing the interfacial evolution from charge compensation to metallic screening across the manganite metal-insulator transition
Julia A. Mundy, Yasuyuki Hikita, Takeaki Hidaka, Takeaki Yajima, Takuya Higuchi, Harold Y. Hwang, David A. Muller, Lena F. Kourkoutis
NATURE COMMUNICATIONS, 5, Mar, 2014
Atomic-scale Planarization of Ge (111), (110) and (100) Surfaces
Tomonori Nishimura, ChoongHyun Lee, Takeaki Yajima, Kosuke Nagashio, Akira Toriumi
2014 7TH INTERNATIONAL SILICON-GERMANIUM TECHNOLOGY AND DEVICE MEETING (ISTDM), 127-128, 2014
Analytical Formulation of SiO2-IL scavenging in HfO2/SiO2/Si gate stacks – A key is the SiO2/Si interface reaction –
Xiuyan Li, Takeaki Yajima, Tomonori Nishimura, Kosuke Nagashio, Akira Toriumi
2014 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM), 2014
Kinetic Model for Scavenging of SiO2 Interface Layer in HfO2 Gate Stacks
Xiuyan Li, Takeaki Yajima, Tomonori Nishimura, Kosuke Nagashio, Akira Toriumi
2014 IEEE SILICON NANOELECTRONICS WORKSHOP (SNW), 2014
2013
Coexistence of two-dimensional and three-dimensional Shubnikov–de Haas oscillations in Ar+-irradiated KTaO3
S. Harashima, C. Bell, M. Kim, T. Yajima, Y. Hikita, H. Y. Hwang
Physical Review B – Condensed Matter and Materials Physics, 88(8) 085102, Aug 2, 2013
Hot electron transport in a strongly correlated transition-metal oxide
Kumari Gaurav Rana, Takeaki Yajima, Subir Parui, Alexander F. Kemper, Thomas P. Devereaux, Yasuyuki Hikita, Harold Y. Hwang, Tamalika Banerjee
SCIENTIFIC REPORTS, 3, Feb, 2013
Atomically Flat Germanium (111) Surface by Hydrogen Annealing
T. Nishimura, S. Kabuyanagi, C. H. Lee, T. Yajima, K. Nagashio, A. Toriumi
ULSI PROCESS INTEGRATION 8, 58(9) 201-206, 2013
High electron mobility (>16 cm2/Vsec) FETs with high on/off ratio (>106) and highly conductive films (σ>102 S/cm) by chemical doping in very thin (∼20 nm) TiO2 films on thermally grown SiO2
Go Oike, Takeaki Yajima, Tomonori Nishimura, Kosuke Nagashio, Akira Toriumi
Technical Digest – International Electron Devices Meeting, IEDM, 11.5.4, 2013
2011
Reentrant insulating state in ultrathin manganite films
Bongju Kim, Daeyoung Kwon, Takeaki Yajima, Christopher Bell, Yasuyuki Hikita, Bog G. Kim, Harold Y. Hwang
APPLIED PHYSICS LETTERS, 99(9), Aug, 2011
A heteroepitaxial perovskite metal-base transistor
Takeaki Yajima, Yasuyuki Hikita, Harold Y. Hwang
NATURE MATERIALS, 10(3) 198-201, Mar, 2011
2010
Charge Writing at the LaAlO3/SrTiO3 Surface
Yanwu Xie, Christopher Bell, Takeaki Yajima, Yasuyuki Hikita, Harold Y. Hwang
NANO LETTERS, 10(7) 2588-2591, Jul, 2010
2009
Mn3O4 precipitates in laser-ablated manganite films
T. Higuchi, T. Yajima, L. Fitting Kourkoutis, Y. Hikita, N. Nakagawa, D. A. Muller, H. Y. Hwang
APPLIED PHYSICS LETTERS, 95(4) 043112, Jul, 2009
Termination control of the interface dipole in La0.7Sr0.3MnO3/Nb:SrTiO3 (001) Schottky junctions
Yasuyuki Hikita, Mitsuru Nishikawa, Takeaki Yajima, Harold Y. Hwang
PHYSICAL REVIEW B, 79(7), Feb, 2009