論文 - 小田　将人

Sustainable thermoelectric materials: Utilizing Fukushima weathered biotite via molten salt treatment

Mitsunori Honda, Yui Kaneta, Masakazu Muraguchi, Kosetsu Hayakawa, Masato Oda, Chiaki Iino, Hiroyuki Ishii, Takuya Goto

AIP Advances ( AIP Publishing )  14 ( 5 )   2024年05月  [査読有り]

　概要を見る

This study examines the utilization of Fukushima weathered biotite (WB) as an alternative to conventional thermoelectric materials traditionally derived from rare and toxic substances. WB underwent milling, classification, and subsequent heat treatment via molten-salt treatment to produce crystals exhibiting conductivity akin to semiconductors within the 650–850 °C range. Evaluation of WB and the derived crystal’s electrical conductivity and Seebeck coefficient showcased their viability for high-temperature thermoelectric applications. Consequently, WB attained a dimensionless figure of merit (ZT) of 0.015, signaling its potential as a thermoelectric material that surpasses 650 °C.

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Adiabatic Potential for Conformational Change of V_Ga–V_N Complex Defects in GaN

Jota Nakamura, Masato Oda, Yoshihiro Kangawa (担当区分： 責任著者 )

physica status solidi (b) ( Wiley )    2024年03月  [査読有り]

　概要を見る

Focusing on a V_Ga–V_N complex vacancy defect in GaN, the adiabatic potential for conformational changes of the V_Ga–V_N is investigated using the density functional theory. There are two types of configurations due to the symmetry of the crystal, it is confirmed that there is almost no difference in their stability or electronic state. Using these configurations as the initial and final states, the defect reaction is analyzed when V_Ga–V_N moves using the climbing‐image nudged elastic band method. The reaction barrier for the migration of V_Ga (V_N) is found to be 2.2 (3.3) eV. It is concluded that these reactions occur frequently as GaN is annealed since the atomic diffusion potential barrier is similar to that in other semiconductors. These results suggest that V_Ga–V_N in GaN moves through the crystal as a pair of vacancies by alternately repeating the V_Ga and the V_N migration. These results provide important knowledge for elucidating the microscopic mechanism of the experimentally observed V_Ga–V_N aggregation reaction.

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(ZnO)1-x(InN)x混晶半導体の初期成長過程と電子状態

小田将人, 古木凌太, 篠塚雄三 (担当区分： 筆頭著者,　責任著者 )

日本結晶成長学会誌   50 ( 1 ) 50-1-06_1 - 50-1-06_11   2023年04月  [査読有り]  [招待有り]

Electronic Structures of Iodine‐Doped Lithium Phthalocyanine Crystals

Masato Oda, Noritake Koike (担当区分： 筆頭著者,　最終著者,　責任著者 )

physica status solidi (b) ( Wiley )  260 ( 5 )   2023年03月  [査読有り]

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Theoretical study on adsorption state of chemisorbed oxygen molecule on partially oxidized Si(001) surface

Nao Kadowaki, Masato Oda, Jun Nara

Japanese Journal of Applied Physics ( IOP Publishing )  60 ( 12 ) 125501 - 125501   2021年11月  [査読有り]

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Investigation of GaAs and AlAs atomic-layer epitaxial growth mechanism based on experimental results and first-principles total energy calculation

Nobuyuki Ohtsuka, Masato Oda, Takashi Eshita, Ichiro Tanaka, Chihiro Itoh

Jpn. J. Appl. Phys.   59   SGGK16   2020年02月  [査読有り]

Study on the initial growth mechanism of (ZnO)1−x(InN)x using first-principles calculation

Ryota Furuki, Masato Oda, Yuzo Shinozuka

Jpn. J. Appl. Phys   59   SGGK11   2020年02月  [査読有り]

Investigation of the electron-phonon interactions around Ga vacancies in GaN and their role in the first stage of defect reactions

小田将人 (担当区分： 筆頭著者,　最終著者,　責任著者 )

Jpn. J. Appl. Phys.   58   SCCC16   2019年  [査読有り]

Electronic structure of (ZnO)1-x(InN)x alloys calculated by interacting quasi-band theory

R. Furuki, M. Oda, Y. Shinozuka

Japanese Journal of Applied Physics   58   021002   2019年  [査読有り]

Electronic structures of a cerasome surface model

小田将人 (担当区分： 筆頭著者,　最終著者,　責任著者 )

Jpn. J. Appl. Phys.   58   SIID04   2019年  [査読有り]

フェロセン内包カーボンナノチューブの電子状態計算

境 新, 小田 将人, 伊東 千尋, 篠塚 雄三

日本物理学会講演概要集 ( 一般社団法人 日本物理学会 )  73.1   1818 - 1818   2018年

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Electronic structure calculation of Si1-xSnx compound alloy using interacting quasi-band theory

Masato Oda, Yukina Kuroda, Ayaka Kishi, Yuzo Shinozuka (担当区分： 筆頭著者 )

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS ( WILEY-V C H VERLAG GMBH )  254 ( 2 ) 1600519   2017年02月  [査読有り]

　概要を見る

We investigate energy band structures of the Si1-xSnx compound alloy in the zincblende structure using interacting quasi-band (IQB) theory. We first extend the IQB theory for four-element compounds and subsequently calculate the electronic structures of the virtual Si1-xSnxSi1-ySny alloy where x=y. Diagonalizing a 20x20 non-Hermitian Hamiltonian matrix using sp(3)s* empirical tight-binding model with parameters obtained for the Si, Sn, and SiSn (zincblende) crystals, we obtain the electronic energy spectrum of the Si1-xSnx alloy for arbitrary x. Comparing the band structures, we reveal that the indirect-direct gap crossover in Si1-xSnx alloys occurs around x=0.67 with E-g=0.87eV. Calculated Sn concentration dependence of energy gaps in Si1-xSnx alloy.

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First-principles calculation of electron-phonon coupling at a Ga vacancy in GaN

Takeshi Tsujio, Masato Oda, Yuzo Shinozuka (担当区分： 責任著者 )

Japanese Journal of Applied Physics ( Japan Society of Applied Physics )  56 ( 9 ) 091001   2017年  [査読有り]

　概要を見る

We investigate the dependence of the electronic band structure on the localized phonon mode at a Ga vacancy in GaN. The electronic states and phonon modes are both calculated using a first-principles method based on the density functional theory. Comparing the calculated electronic band structures and phonon-frequency densities of states of GaN without and with a Ga vacancy, we find that 1) there are localized electronic midgap states closely above the top of the valence band, 2) localized phonon modes appear above the acoustic and optical phonon bands, 3) one of these localized phonon modes contains asymmetric distortions in which one of the four N atoms around a Ga vacancy strongly oscillates, and 4) the localized electronic midgap states strongly couple with the localized asymmetric mode. These results indicate that a Ga vacancy can act as a nonradiative recombination center and may trigger defect reactions in GaN-based devices.

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First-principles study of initial oxidation process of Ge(100) surfaces

Takahiro Mizukoshi, Masato Oda (担当区分： 最終著者,　責任著者 )

JAPANESE JOURNAL OF APPLIED PHYSICS ( IOP PUBLISHING LTD )  55 ( 8 ) 08PE03   2016年08月  [査読有り]

　概要を見る

Stable structures of oxygen atoms inserted into Ge(100) surfaces are investigated by first-principles calculations based on the density functional theory. Comparing the total energies of several models, the most stable structure is realized when oxygen atoms are inserted into the backbond of a lower dimer atom and the next bond along the (100) direction. We calculate the electronic density of states to reveal the origin of the stability. The structure is stable because a dangling bond of the lower dimer atom disappeared to form a four-coordinated structure. We also reveal that the dangling bond disappears from equal-amplitude plots of wave functions. These results are due to the strong electronegativity of the oxygen atom. (C) 2016 The Japan Society of Applied Physics

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Interacting quasi-band theory for electronic states in compound semiconductor alloys: Wurtzite structure

Ayaka Kishi, Masato Oda, Yuzo Shinozuka

JAPANESE JOURNAL OF APPLIED PHYSICS ( IOP PUBLISHING LTD )  55 ( 5 ) 051202   2016年05月  [査読有り]

　概要を見る

This paper reports on the electronic states of compound semiconductor alloys of wurtzite structure calculated by the recently proposed interacting quasi-band (IQB) theory combined with empirical sp(3) tight-binding models. Solving derived quasi-Hamiltonian 24 X 24 matrix that is characterized by the crystal parameters of the constituents facilitates the calculation of the conduction and valence bands of wurtzite alloys for arbitrary concentrations under a unified scheme. The theory is applied to III-V and II-VI wurtzite alloys: cation-substituted Al1-xGaxN and Ga1-xInxN and anion-substituted CdS1-xSex and ZnO1-xSx. The obtained results agree well with the experimental data, and are discussed in terms of mutual mixing between the quasi-localized states (QLS) and quasi-average bands (QAB): the latter bands are approximately given by the virtual crystal approximation (VCA). The changes in the valence and conduction bands, and the origin of the band gap bowing are discussed on the basis of mixing character. (C) 2016 The Japan Society of Applied Physics

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19aAR-7 Ge(100)表面における初期酸化過程の安定構造

水越 隆大, 小田 将人

日本物理学会講演概要集 ( 一般社団法人日本物理学会 )  71   2486 - 2486   2016年

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GaN中の欠陥における格子変位が引き起こす電子状態変化

辻尾 健志, 小田 将人, 篠塚 雄三

日本物理学会講演概要集 ( 一般社団法人 日本物理学会 )  71   2558 - 2558   2016年

　概要を見る

<p>GaN中の欠陥反応は、デバイスの性能劣化に重大な影響を与えるがその発生機構は明らかになっていない。先行研究では、バンドギャップ中の孤立電子準位の荷電状態変化によって局在振動モードが増強され、欠陥反応が誘起される機構を簡単なモデルによって示した。本研究では第一原理計算を用い具体的な空孔欠陥を含むGaNモデルの電子状態及び振動状態解析を行った。上記欠陥反応機構が実際に起こりうることを示した。</p>

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Electronic States of III-V and II-VI Alloys Calculated by IQB Theory

Ayaka Kishi, Masato Oda, Yuzo Shinozuka

2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS) ( IEEE )    2016年  [査読有り]

　概要を見る

The electronic states of compound semiconductor (III-V and II-VI) alloys are calculated by the recently proposed interacting quasi-band (IQB) theory. Combining with the sp(3)(s*) empirical tight-binding model, quasi-Hamiltonian matrix facilitates the calculation of the conduction and valence bands of general alloys, A(1-x)B(x)D (AD(1-y)F(y)) for arbitrary concentration x (y) under a unified scheme. The concentration dependence of the electronic bands, including midgap states, is discussed in particular attention to constituent materials, lattice structure (zincblend or wurtzite), and substitution type (anion or cation).

Electronic Structures Calculation of Si1-xSnx Compound Alloy Using Inter-acting Quasi-band Model

Masato Oda, Yukina Kuroda, Ayaka Kishi, Yuzo Shinozuka (担当区分： 筆頭著者,　責任著者 )

2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS) ( IEEE )    2016年  [査読有り]

Interacting quasi-band model for electronic states in compound semiconductor alloys: Zincblende structure

Yuzo Shinozuka, Masato Oda

JAPANESE JOURNAL OF APPLIED PHYSICS ( IOP PUBLISHING LTD )  54 ( 9 ) 091202   2015年09月  [査読有り]

　概要を見る

The interacting quasi-band model proposed for electronic states in simple alloys is extended for compound semiconductor alloys with general lattice structures containing several atoms per unit cell. Using a tight-binding model, a variational electronic wave function for quasi-Bloch states yields a non-Hermitian Hamiltonian matrix characterized by matrix elements of constituent crystals and concentration of constituents. Solving secular equations for each k-state yields the alloy's energy spectrum for any type of randomness and arbitrary concentration. The theory is used to address III-V (II-VI) alloys with a zincblende lattice with crystal band structures well represented by the sp(3)s* model. Using the resulting 15 x 15 matrix, the concentration dependence of valence and conduction bands is calculated in a unified scheme for typical alloys: Al1-xGaxAs, GaAs1-xPx, and GaSb1-xPx. Results agree well with experiments and are discussed with respect to the concentration dependence, direct-indirect gap transition, and band-gap-bowing origin. (C) 2015 The Japan Society of Applied Physics

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