# Fumiyasu Oba (Professor, Tokyo Institute of Technology)¶

## Research Interest¶

Atomistic and electronic structure of point defects, surfaces, and interfaces in compound semiconductors and their impact on the electrical properties: A theoretical approach using first-principles calculations

- Native defects and dopants:
- ZnO, SrTiO
_{3}, BaTiO_{3}, EuTiO_{3}, NaTaO_{3}, KTaO_{3}, Cu_{2}O, SnO, NiO, Ga_{2}O_{3}, Ca_{2}CuO_{2}Cl_{2}, MgAl_{2}O_{4}, MgO, Si_{3}N_{4}, BN, AlN, GaN, Li_{3}N, CuInSe_{2}, CuGaSe_{2}, ZnSnP_{2}, and CdSnP_{2}.

- Surfaces:
- ZnO, GaN, GaAs, Si, C, BN, CuInSe
_{2}, CuGaSe_{2}, ZnSnP_{2}, CdSnP_{2}, etc

- Heterointerfaces:
- CuInSe
_{2}/CdS, ZnS, CdTe/CdS, g-Ga_{2}O_{3}/MgAl_{2}O_{4}, Cu_{2}O/ZnO, etc

- Grain boundaries:
- ZnO, YSZ, and BaZrO
_{3}.

## Refereed Journal Publications¶

Ionization potentials of solids: The importance of vertex corrections

A. Gruneis, G. Kresse, Y. Hinuma, and F. Oba,

*Phys. Rev. Lett.*,**112**, 096401-1-5 (2014).Electrostatics-based finite-size corrections for first-principles point defect calculations

Y. Kumagai and F. Oba,

*Phys. Rev. B*,**89**, 195205-1-15 (2014). [Editors’ Suggestion]First-principles study of point defects in chalcopyrite ZnSnP

_{2}Y. Kumagai, M. Choi, Y. Nose, and F. Oba,

*Phys. Rev. B*,**90**, 125202-1-12 (2014).Band alignment of semiconductors from density-functional theory and many-body perturbation theory

Y. Hinuma, A. Gruneis, G. Kresse, and F. Oba,

*Phys. Rev. B*,**90**, 155405-1-16 (2014).Atomic structure of luminescent centers in high-efficiency Ce-doped w-AlN single crystal

R. Ishikawa, A. R. Lupini, F. Oba, S. D. Findlay, N. Shibata, T. Taniguchi, K. Watanabe, H. Hayashi, T. Sakai, I. Tanaka, Y. Ikuhara, and S. J. Pennycook,

*Sci. Rep.*,**4**, 3778-1-5 (2014).Anti-ferrodistortive-like oxygen-octahedron rotation induced by the oxygen vacancy in cubic SrTiO

_{3}M. Choi, F. Oba, Y. Kumagai, and I. Tanaka,

*Adv. Mater.*,**25**, 86-90 (2013).Strong spin-lattice coupling through oxygen octahedral rotation in divalent europium perovskites

H. Akamatsu, Y. Kumagai, F. Oba, K. Fujita, K. Tanaka, and I. Tanaka,

*Adv. Funct. Mater.*,**23**, 1864-1872 (2013).Functional complex point-defect structure in a huge-size-mismatch system

R. Ishikawa, N. Shibata, F. Oba, T. Taniguchi, S. D. Findlay, I. Tanaka, and Y. Ikuhara,

*Phys. Rev. Lett.*,**110**, 065504-1-5 (2013).Valence band offsets at zinc-blende heterointerfaces with misfit dislocations: A first-principles study

Y. Hinuma, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**88**, 075319-1-8 (2013).Band offsets of CuInSe

_{2}/CdS and CuInSe_{2}/ZnS (110) interfaces: A hybrid density functional theory studyY. Hinuma, F. Oba, Y. Kumagai, and I. Tanaka,

*Phys. Rev. B*,**88**, 035305-1-12 (2013).Theoretical photovoltaic conversion efficiencies of ZnSnP

_{2}, CdSnP_{2}, and Zn_{1-x}Cd_{x}SnP_{2}alloysT. Yokoyama, F. Oba, A. Seko, H. Hayashi, Y. Nose, and I. Tanaka,

*Appl. Phys. Express*,**6**, 061201-1-3 (2013).First-principles study of valence band offsets at ZnSnP

_{2}/CdS, ZnSnP_{2}/ZnS, and related chalcopyrite/zincblende heterointerfacesY. Hinuma, F. Oba, Y. Nose, and I. Tanaka,

*J. Appl. Phys.*,**114**, 043718-1-6 (2013).Local environment of silicon in cubic boron nitride

H. Murata, T. Taniguchi, S. Hishita, T. Yamamoto, F. Oba, and I. Tanaka,

*J. Appl. Phys.*,**114**, 233502-1-4 (2013).Site preference of cation vacancies in Mn-doped Ga

_{2}O_{3}with defective spinel structureH. Hayashi, R. Huang, F. Oba, T. Hirayama, and I. Tanaka,

*Appl. Phys. Lett.*,**101**, 241906-1-4 (2012).Ionization potentials of (112) and (11-2) facet surfaces of CuInSe

_{2}and CuGaSe_{2}Y. Hinuma, F. Oba, Y. Kumagai, and I. Tanaka,

*Phys. Rev. B*,**86**, 245433-1-7 (2012).First-principles calculations of the phase diagrams and band gaps in CuInSe

_{2}-CuGaSe_{2}and CuInSe_{2}-CuAlSe_{2}pseudobinary systemsY. Kumagai, Y. Soda, F. Oba, A. Seko, and I. Tanaka,

*Phys. Rev. B*,**85**, 033203-1-4 (2012).Ground-state search in multicomponent magnetic systems

Y. Kumagai, A. Seko, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**85**, 012401-1-4 (2012).Crystal and electronic structure and magnetic properties of divalent europium perovskite oxides Eu

*M*O_{3}(*M*= Ti, Zr, and Hf): Experimental and first-principles approachesH. Akamatsu, K. Fujita, H. Hayashi, T. Kawamoto, Y. Kumagai, Y. Zong, K. Iwata, F. Oba, I. Tanaka, and K. Tanaka,

*Inorg. Chem.*,**51**, 4560-4567 (2012).Defect chemistry of a BaZrO

_{3}S3 (111) grain boundary by first principles calculations and space-charge theoryJ. M. Polfus, K. Toyoura, F. Oba, I. Tanaka, and R. Haugsrud,

*Phys. Chem. Chem. Phys.*,**14**, 12339-12346 (2012).Point defects in ZnO: An approach from first principles

F. Oba, M. Choi, A. Togo, and I. Tanaka,

*Sci. Tech. Adv. Mater.*,**12**, 034302-1-14 (2011). [Topical Review]Electronic and structural properties of the oxygen vacancy in BaTiO

_{3}M. Choi, F. Oba, and I. Tanaka,

*Appl. Phys. Lett.*,**98**, 172901-1-3 (2011).Hybrid density functional study of oxygen vacancies in KTaO

_{3}and NaTaO_{3}M. Choi, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**83**, 214107-1-6 (2011).Antiferromagnetic superexchange via 3d states of titanium in EuTiO

_{3}as seen from hybrid Hartree-Fock density functional calculationsH. Akamatsu, Y. Kumagai, F. Oba, K. Fujita, H. Murakami, K. Tanaka, and I. Tanaka,

*Phys. Rev. B*,**83**, 214421-1-6 (2011).Epitaxial growth of Mn-doped g-Ga

_{2}O_{3}on spinel substrateH. Hayashi, R. Huang, F. Oba, T. Hirayama, and I. Tanaka,

*J. Mater. Res.*,**26**, 578-583 (2011).Atomistic structure and energetics of interface between Mn-doped g-Ga

_{2}O_{3}and MgAl_{2}O_{4}H. Hayashi, R. Huang, F. Oba, T. Hirayama, and I. Tanaka,

*J. Mater. Sci.*,**46**, 4169-4175 (2011).Epitaxial growth and characterization of rocksalt ZnO thin films with low-level NiO alloying

S. Katayama, H. Hayashi, F. Oba, and I. Tanaka,

*Jpn. J. Appl. Phys.*,**50**, 075503-1-5 (2011).Doping of hexagonal boron nitride via intercalation: A theoretical prediction

F. Oba, A. Togo, I. Tanaka, K. Watanabe, and T. Taniguchi,

*Phys. Rev. B*,**81**, 075125-1-6 (2010).Classification of spinel structures based on first-principles cluster expansion analysis

A. Seko, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**81**, 054114-1-7 (2010).Native defects in oxide semiconductors: A density functional approach

F. Oba, M. Choi, A. Togo, A. Seko, and I. Tanaka,

*J. Phys.: Condens. Matter*,**22**, 384211-1-9 (2010). [in JPCM Highlights of 2010]Phase relationships and structures of inorganic crystals by combination of cluster expansion method and first principles calculations

I. Tanaka, A. Seko, A. Togo, Y. Koyama, and F. Oba,

*J. Phys.: Condens. Matter*,**22**, 384207-1-8 (2010).Non-Fermi-liquid behavior on an iron-based itinerant electron magnet Fe

_{3}Mo_{3}NT. Waki, S. Terazawa, Y. Tabata, F. Oba, C. Michioka, K. Yoshimura, S. Ikeda, H. Kobayashi, K. Ohoyama, and H. Nakamura,

*J. Phys. Soc. Jpn.*,**79**, 043701-1-4 (2010).Thermodynamics and structures of oxide crystals by a systematic set of first principles calculations

I. Tanaka, A. Togo, A. Seko, F. Oba, Y. Koyama, and A. Kuwabara,

*J. Mater. Chem.*,**20**, 10335-10344 (2010).Role of Ti antisite-like defects in SrTiO

_{3}M. Choi, F. Oba, and I. Tanaka,

*Phys. Rev. Lett.*,**103**, 185502-1-4 (2009).First-principles study of defect-induced potentials in Ca

_{2}CuO_{2}Cl_{2}Y. Kumagai, F. Oba, I. Yamada, M. Azuma, and I. Tanaka,

*Phys. Rev. B*,**80**, 085120-1-9 (2009).Variable anisotropy of ionic conduction in lithium nitride: Effect of duplex-charge transfer

I. Kishida, F. Oba, Y. Koyama, A. Kuwabara, and I. Tanaka,

*Phys. Rev. B*,**80**, 024116-1-6 (2009).^{27}Al NMR chemical shifts in oxide crystals: A first-principles studyM. Choi, K. Matsunaga, F. Oba, and I. Tanaka,

*J. Phys. Chem. C*,**113**, 3869-3873 (2009).Defect energetics in ZnO: A hybrid Hartree-Fock density functional study

F. Oba, A. Togo, I. Tanaka, J. Paier, and G. Kresse,

*Phys. Rev. B*,**77**, 245202-1-6 (2008).Transition pathway of CO

_{2}crystals under high pressuresA. Togo, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**77**, 184101-1-5 (2008).Structure and stability of homologous series of tin oxides

A. Seko, A. Togo, F. Oba, and I. Tanaka,

*Phys. Rev. Lett.*,**100**, 045702-1-4 (2008).First-principles study of native defects and lanthanum impurities in NaTaO

_{3}M. Choi, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**78**, 014115-1-8 (2008).Effects of crystal structure on Co-

*L*_{2,3}x-ray absorption near-edge structure and electron-energy-loss near-edge structure of trivalent cobalt oxidesY. Kumagai, H. Ikeno, F. Oba, K. Matsunaga, and I. Tanaka,

*Phys. Rev. B*,**77**, 155124-1-9 (2008).First-principles-based phase diagram of the cubic BNC ternary system

K. Yuge, A. Seko, Y. Koyama, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**77**, 094121-1-8 (2008).First-principles calculations of the ferroelastic transition between rutile-type and CaCl

_{2}-type SiO_{2}at high pressuresA. Togo, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**78**, 134106-1-9 (2008).First-principles approach to chemical diffusion of lithium atoms in a graphite intercalation compound

K. Toyoura, Y. Koyama, A. Kuwabara, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**78**, 214303-1-12 (2008).First principles calculations for modern ceramic science and engineering

I. Tanaka and F. Oba,

*J. Phys.: Condens. Matter*,**20**, 064215-1-6 (2008).Atomic structures of supersaturated ZnO-Al

_{2}O_{3}solid solutionsS. Yoshioka, F. Oba, R. Huang, I. Tanaka, T. Mizoguchi, and T. Yamamoto,

*J. Appl. Phys.*,**103**, 014309-1-9 (2008).First-principles investigation of R

_{2}O_{3}(ZnO)_{3}(R=Al, Ga, and In) in homologous series of compoundsS. Yoshioka, K. Toyoura, F. Oba, A. Kuwabara, K. Matsunaga, and I. Tanaka,

*J. Solid State Chem.*,**181**, 137-142 (2008).First principles calculation of CO and H

_{2}adsorption on strained Pt surfaceA. Kuwabara, Y. Saito, Y. Koyama, F. Oba, K. Matsunaga, and I. Tanaka,

*Mater. Trans.*,**49**, 2484-2490 (2008).Ordering and segregation of Cu

_{75}Pt_{25}(111) surface: A first-principles cluster expansion studyK. Yuge, A. Seko, A. Kuwabara, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**76**, 045407-1-8 (2007).Awaking of ferromagnetism in GaMnN through control of Mn valence

S. Sonoda, I. Tanaka, F. Oba, H. Ikeno, H. Hayashi, T. Yamamoto, Y. Yuba, K. Yoshida, M. Aoki, M. Asari, Y. Akasaka, K. Kindo, and H. Hori,

*Appl. Phys. Lett.*,**90**, 012504-1-3 (2007).Microstructure of Mn-doped g-Ga

_{2}O_{3}epitaxial film on sapphire (0001) with room temperature ferromagnetismR. Huang, H. Hayashi, F. Oba, and I. Tanaka,

*J. Appl. Phys.*,**101**, 063526-1-6 (2007).Structures and energetics of Ga

_{2}O_{3}polymorphsS. Yoshioka, H. Hayashi, A. Kuwabara, F. Oba, K. Matsunaga, and I. Tanaka,

*J. Phys.: Condens. Matter*,**19**, 346211-1-11 (2007).First-principles study of defect equilibria in lithium zinc nitride

K. Toyoura, F. Oba, T. Ninomiya, A. Kuwabara, and I. Tanaka,

*J. Phys.: Condens. Matter*,**19**, 046201-1-11 (2007).First-principles calculations of native defects in tin monoxide

A. Togo, F. Oba, I. Tanaka, and K. Tatsumi,

*Phys. Rev. B*,**74**, 195128-1-8 (2006).First-principles study of cation disordering in MgAl

_{2}O_{4}spinel with cluster expansion and Monte Carlo simulationA. Seko, K. Yuge, F. Oba, A. Kuwabara, I. Tanaka, and T. Yamamoto,

*Phys. Rev. B*,**73**, 094116-1-6 (2006).Debye temperature and stiffness of carbon and boron nitride polymorphs from first principles calculations

T. Tohei, A. Kuwabara, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**73**, 064304-1-7 (2006).Prediction of ground-state structures and order-disorder phase transitions in II-III spinel oxides: A combined cluster-expansion method and first-principles study

A. Seko, K. Yuge, F. Oba, A. Kuwabara, and I. Tanaka,

*Phys. Rev. B*,**73**, 184117-1-5 (2006).First-principles study of bulk ordering and surface segregation in PtRh binary alloys

K. Yuge, A. Seko, A. Kuwabara, F. Oba, and I. Tanaka,

*Phys. Rev. B*,**74**, 174202-1-13 (2006).Room temperature ferromagnetism in Mn-doped g-Ga

_{2}O_{3}with spinel structureH. Hayashi, R. Huang, H. Ikeno, F. Oba, S. Yoshioka, I. Tanaka, and S. Sonoda,

*Appl. Phys. Lett.*,**89**, 181903-1-3 (2006).Carbon supersaturation due to paraequilibrium carburization: Stainless steels with greatly improved mechanical properties

G. M. Michal, F. Ernst, H. Kahn, Y. Cao, F. Oba, N. Agarwal, and A. H. Heuer,

*Acta Mater.*,**54**, 1597-1606 (2006).First principles calculations of migration energy of lithium ions in halides and chalcogenides

I. Kishida, Y. Koyama, A. Kuwabara, T. Yamamoto, F. Oba, and I. Tanaka,

*J. Phys. Chem. B*,**110**, 8258-8262 (2006).Coexistence of Mn

^{2+}and Mn^{3+}in ferromagnetic GaMnNS. Sonoda, I. Tanaka, H. Ikeno, T. Yamamoto, F. Oba, T. Araki, Y. Yamamoto, K. Suga, Y. Nanishi, Y. Akasaka, K. Kindo, and H. Hori,

*J. Phys.: Condens. Matter*,**18**, 4615-4621 (2006).Gas-phase surface alloying under “kinetic control”: A novel approach to improving the surface properties of titanium alloys

F. Ernst, G. M. Michal, F. Oba, L. Liu, J. Blush, and A. H. Heuer,

*Int. J. Mater. Res.*,**97**, 597-606 (2006).Epitaxial growth of cuprous oxide electrodeposited onto semiconductor and metal substrates

F. Oba, F. Ernst, Y. Yu, R. Liu, H. M. Kothari, and J. A. Switzer,

*J. Am. Ceram. Soc.*,**88**, 253-270 (2005). [Feature Article]Local environment of Mn dopant in ZnO by near-edge x-ray absorption fine structure analysis

M. Kunisu, F. Oba, H. Ikeno, I. Tanaka, and T. Yamamoto,

*Appl. Phys. Lett.*,**86**, 121902-1-3 (2005).Epitaxial electrodeposition of high-aspect-ratio Cu

_{2}O (110) nanostructures on InP(111)R. Liu, E. A. Kulp, F. Oba, E. W. Bohannan, F. Ernst, and J. A. Switzer,

*Chem. Mater.*,**17**, 725-729 (2005).General rule for displacive phase transitions in perovskite compounds revisited by first principles calculations

T. Tohei, A. Kuwabara, T. Yamamoto, F. Oba, and I. Tanaka,

*Phys. Rev. Lett.*,**94**, 035502-1-4 (2005).Pressure-induced phase transition in ZnO and ZnO-MgO pseudobinary system: A first-principles lattice dynamics study

A. Seko, F. Oba, A. Kuwabara, and I. Tanaka,

*Phys. Rev. B*,**72**, 024107-1-10 (2005).Arrangement of multiple structural units in a [0001] S49 tilt grain boundary in ZnO

Y. Sato, T. Mizoguchi, F. Oba, Y. Ikuhara, and T. Yamamoto,

*Phys. Rev. B*,**72**, 064109-1-7 (2005).Effect of boundary plane on the atomic structure of [0001] S7 tilt grain boundaries in ZnO

F. Oba, Y. Sato, T. Yamamoto, H. Ohta, H. Hosono, and Y. Ikuhara,

*J. Mater. Sci.*,**40**, 3067-3074 (2005).Atomic and electronic structure of [0001]/(-1-230) S7 symmetric tilt grain boundary in undoped ZnO bicrystal with linear current-voltage characteristic

Y. Sato, T. Mizoguchi, F. Oba, M. Yodogawa, T. Yamamoto, and Y. Ikuhara,

*J. Mater. Sci.*,**40**, 3059-3066 (2005).Systematic study of grain boundary atomistic structures and related properties in cubic zirconia bicrystals

N. Shibata, F. Oba, T. Yamamoto, and Y. Ikuhara,

*Z. Metallkd.*,**96**, 177-185 (2005).Atomic structure of [0001]-tilt grain boundaries in ZnO: A high-resolution TEM study of fiber-textured thin films

F. Oba, H. Ohta, Y. Sato, H. Hosono, T. Yamamoto, and Y. Ikuhara,

*Phys. Rev. B*,**70**, 125415-1-12 (2004).Effectiveness of BaZrO

_{3}buffer layer in SmBa_{2}Cu_{3}O_{y}epitaxial growth on MgO substrate: A first-principles studyF. Oba, Y. Sugawara, K. Hasegawa, T. Izumi, Y. Shiohara, T. Hirayama, T. Yamamoto, and Y. Ikuhara,

*J. Appl. Phys.*,**95**, 2309-2318 (2004).Grain boundary dependency of nonlinear current-voltage characteristics in Pr and Co doped ZnO bicrystals

Y. Sato, F. Oba, M. Yodogawa, T. Yamamoto, and Y. Ikuhara,

*J. Appl. Phys.*,**95**, 1258-1264 (2004).Identification of native defects around grain boundary in Pr-doped ZnO bicrystal using electron energy loss spectroscopy and first-principles calculations

Y. Sato, T. Mizoguchi, F. Oba, M. Yodogawa, T. Yamamoto, and Y. Ikuhara,

*Appl. Phys. Lett.*,**84**, 5311-5313 (2004).Structure, energy and solute segregation behaviour of [110] symmetric tilt grain boundaries in yttria-stabilized cubic zirconia

N. Shibata, F. Oba, T. Yamamoto, and Y. Ikuhara,

*Philos. Mag.*,**84**, 2381-2415 (2004).Interfacial structures of Y123 and Nd123 films formed on MgO(001) substrates by liquid phase epitaxy

J. S. Matsuda, F. Oba, T. Murata, T. Yamamoto, Y. Ikuhara, M. Mizuno, K. Nomura, T. Izumi, and Y. Shiohara,

*J. Mater. Res.*,**19**, 2674-2682 (2004).Current-voltage characteristics of cobalt-doped inversion boundaries in zinc oxide bicrystals

F. Oba, Y. Sato, T. Yamamoto, Y. Ikuhara, and T. Sakuma,

*J. Am. Ceram. Soc.*,**86**, 1616-1618 (2003).Grain boundary faceting at S=3, [110]/{112} grain boundary in cubic zirconia bicrystal

N. Shibata, F. Oba, T. Yamamoto, T. Sakuma, and Y. Ikuhara,

*Philos. Mag.*,**83**, 2221-2246 (2003).Shape control in epitaxial electrodeposition: Cu

_{2}O nanocubes on InP (001)R. Liu, F. Oba, E. W. Bohannan, F. Ernst, and J. A. Switzer,

*Chem. Mater.*,**15**, 4882-4885 (2003).Epitaxial electrodeposition of Cu

_{2}O films onto InP (001)R. Liu, E. W. Bohannan, J. A. Switzer, F. Oba, and F. Ernst,

*Appl. Phys. Lett.*,**83**, 1944-1946 (2003).Improvement of superconducting properties of SmBa

_{2}Cu_{3}O_{y}films on MgO substrate by using BaZrO_{3}buffer layerK. Hasegawa, J. Shibata, T. Izumi, Y. Shiohara, Y. Sugawara, T. Hirayama, F. Oba, and Y. Ikuhara,

*Physica C*,**392-396**, 835-845 (2003).Al-doped ZnO ceramics fabricated by mechanical alloying and high-pressure sintering technique

Y. Sato, F. Oba, M. Yodogawa, T. Yamamoto, and Y. Ikuhara,

*J. Mater. Sci. Lett.*,**22**, 1201-1204 (2003).First principles calculations of the formation energy of Cr/Al vacancies in spinel-type MgCr

_{2}O_{4}and MgAl2O_{4}H. Moriwake, I. Tanaka, F. Oba, Y. Koyama, and H. Adachi,

*Int. J. Quantum Chem.*,**91**, 208-210 (2003).Non-linear current-voltage characteristics related to native defects in SrTiO

_{3}and ZnO bicrystalsY. Sato, T. Tanaka, F. Oba, T. Yamamoto, Y. Ikuhara, and T. Sakuma,

*Sci. Tech. Adv. Mater.*,**4**, 605-611 (2003).Effective doping in cubic Si

_{3}N_{4}and Ge_{3}N_{4}: A first-principles studyF. Oba, K. Tatsumi, I. Tanaka, and H. Adachi,

*J. Am. Ceram. Soc.*,**85**, 97-100 (2002).Atomic structure and solute segregation of a S=3, [110]/{111} grain boundary in an yttria stabilized cubic zirconia bicrystal

N. Shibata, F. Oba, T. Yamamoto, Y. Ikuhara, and T. Sakuma,

*Philos. Mag. Lett.*,**82**, 393-400 (2002).Current-voltage characteristics across [0001] twist boundaries in zinc oxide bicrystals

Y. Sato, F. Oba, T. Yamamoto, Y. Ikuhara, and T. Sakuma,

*J. Am. Ceram. Soc.*,**85**, 2142-2144 (2002).First-principles calculations of anion-vacancies in oxides and nitrides

I. Tanaka, K. Tatsumi, M. Nakano, H. Adachi, and F. Oba,

*J. Am. Ceram. Soc.*,**85**, 68-74 (2002).Theoretical prediction of post-spinel phases of Si

_{3}N_{4}K. Tatsumi, I. Tanaka, H. Adachi, F. Oba, and T. Sekine,

*J. Am. Ceram. Soc.*,**85**, 7-10 (2002).Formation energy of Cr/Al-vacancies in spinel MgCr

_{2}O_{4}and MgAl_{2}O_{4}by first principles calculationsH. Moriwake, I. Tanaka, F. Oba, Y. Koyama, and H. Adachi,

*Phys. Rev. B*,**65**, 153103 1-4 (2002).Hardness of cubic silicon nitride

I. Tanaka, F. Oba, T. Sekine, E. Ito, A. Kubo, K. Tatsumi, H. Adachi, and T. Yamamoto,

*J. Mater. Res.*,**17**, 731-733 (2002).First-principles calculations of Co impurities and native defects in ZnO

F. Oba, T. Yamamoto, Y. Ikuhara, I. Tanaka, and H. Adachi,

*Mater. Trans.*,**43**, 1439-1443 (2002).Current-voltage characteristics across small-angle symmetric tilt boundaries in Nb-doped SrTiO

_{3}bicrystalsT. Yamamoto, F. Oba, Y. Ikuhara, and T. Sakuma,

*Mater. Trans.*,**43**, 1537-1541 (2002).Theoretical formation energy of oxygen-vacancies in oxides

I. Tanaka, F. Oba, K. Tatsumi, M. Kunisu, M. Nakano, and H. Adachi,

*Mater. Trans.*,**43**, 1426-1429 (2002).*n*- and*p*-type dopants for cubic silicon nitrideF. Oba, K. Tatsumi, H. Adachi, and I. Tanaka,

*Appl. Phys. Lett.*,**78**, 1577-1579 (2001).*Ab initio*study of symmetric tilt boundaries in ZnOF. Oba, S. R. Nishitani, H. Adachi, I. Tanaka, M. Kohyama, and S. Tanaka,

*Phys. Rev. B*,**63**, 045410-1-10 (2001).Energetics of native defects in ZnO

F. Oba, S. R. Nishitani, S. Isotani, H. Adachi, and I. Tanaka,

*J. Appl. Phys.*,**90**, 824-828; 3665 (2001).Electron-energy-loss near edge structures of six-fold-coordinated Zn in MgO

T. Mizoguchi, M. Yoshiya, J. Li, F. Oba, I. Tanaka, and H. Adachi,

*Ultramicroscopy*,**86**, 363-370 (2001).Energetics and electronic structure of point defects associated with oxygen excess at a tilt boundary of ZnO

F. Oba, H. Adachi, and I. Tanaka,

*J. Mater. Res.*,**15**, 2167-2175 (2000).Geometry and electronic structure of [0001] / (-1-230) S=7 symmetric tilt boundary in ZnO

F. Oba, I. Tanaka, S. R. Nishitani, H. Adachi, B. Slater, and D. H. Gay,

*Philos. Mag. A*,**80**, 1567-1581 (2000).Core-hole effects on theoretical electron-energy-loss near-edge structure and near-edge x-ray adsorption fine structure of MgO

T. Mizoguchi, I. Tanaka, M. Yoshiya, F. Oba, K. Ogasawara, and H. Adachi,

*Phys. Rev. B*,**61**, 2180-2187 (2000).Electronic structure and chemical bonding of MgCr

_{2-x}O_{4}H. Moriwake, I. Tanaka, F. Oba, and H. Adachi,

*Jpn. J. Appl. Phys., Part 1*,**39**, 513-516 (2000).Effect of oxidation on chemical bonding around 3d transition-metal impurities in ZnO

F. Oba, I. Tanaka, and H. Adachi,

*Jpn. J. Appl. Phys., Part 1*,**38**, 3569-3575 (1999).Valence band structure of ZnO (10-10) surface by cluster calculation

K. Matsunaga, F. Oba, I. Tanaka, and H. Adachi,

*J. Electroceram.*,**4:S1**, 69-80 (1999).Theoretical calculation of oxygen K electron-energy-loss near-edge structure of Si-doped MgO

T. Mizoguchi, I. Tanaka, M. Yoshiya, F. Oba, and H. Adachi,

*J. Phys.: Condens. Matter*,**11**, 5661-5670 (1999).Cluster calculation of oxygen K-edge electron-energy-loss near-edge structure of NiO

H. Kanda, M. Yoshiya, F. Oba, K. Ogasawara, I. Tanaka, and H. Adachi,

*Phys. Rev. B*,**58**, 9693-9696 (1998).

## International Conference Proceedings¶

Finite-size correction for first-principles point defect calculations using a supercell approach

Y. Kumagai and F. Oba,

*AMTC Lett.*,**4**, 88-89 (2014).Effects of misfit dislocations on the band alignment of zincblende semiconductors

Y. Hinuma, F. Oba, and I. Tanaka,

*AMTC Lett.*,**4**, 90-91 (2014).Fabrication and characterization of Sn

_{2}M_{2}O_{7}(M=Nb, Ta) thin filmsS. Katayama, Y. Ogawa, H. Hayashi, F. Oba, and I. Tanaka,

*AMTC Lett.*,**4**, 174-175 (2014).First-principles study of electronic structure in Mn-doped g-Ga

_{2}O_{3}H. Hayashi, R. Huang, F. Oba, T. Hirayama, and I. Tanaka,

*AMTC Lett.*,**3**, 118-119 (2012).Fabrication and characterization of rocksalt Zn

_{1-x}Ni_{x}O thin filmsS. Katayama, H. Hayashi, F. Oba, and I. Tanaka,

*AMTC Lett.*,**3**, 244-245 (2012).Role of d states of B-site cations for spin-lattice coupling in Eu

^{2+}perovskite oxidesH. Akamatsu, F. Oba, Y. Kumagai, K. Fujita, K. Tanaka, and I. Tanaka,

*AMTC Lett.*,**3**, 250-251 (2012).Atomic-resolution STEM imaging in nitrides

R. Ishikawa, N. Shibata, F. Oba, T. Taniguchi, S. D. Findlay, I. Tanaka, and Y. Ikuhara,

*AMTC Lett.*,**3**, 174-175 (2012).First principles calculations of point defects in acceptor-doped BaZrO

_{3}A. Kuwabara, K. Toyoura, Y. Koyama, C. A. J. Fisher, F. Oba, K. Matsunaga, H. Moriwake, and I. Tanaka,

*AMTC Lett.*,**3**, 120-121 (2012).Density functional study of Ti antisites in SrTiO

_{3}, BaTiO_{3}, and PbTiO_{3}M. Choi, F. Oba, and I. Tanaka,

*AMTC Lett.*,**2**, 160-161 (2010).Synthesis of Mn-doped Ga

_{2}O_{3}epitaxial thin film with spinel structureH. Hayashi, R. Huang, X. Wang, F. Oba, T. Hirayama, and I. Tanaka,

*AMTC Lett.*,**2**, 234-235 (2010).Ground-state structures in MgO-NiO crystalline solutions

Y. Kumagai, A. Seko, F. Oba, and I. Tanaka,

*AMTC Lett.*,**2**, 180-181 (2010).Statistical thermodynamics of oxides by combination of cluster expansion method and first principles calculations

I. Tanaka, A. Seko, A. Togo, and F. Oba,

*AMTC Lett.*,**2**, 154-155 (2010).First-principles study of magnetism and electronic structure in Eu

^{2+}perovskite oxidesH. Akamatsu, Y. Kumagai, F. Oba, K. Fujita, K. Tanaka, and I. Tanaka,

*AMTC Lett.*,**2**, 162-163 (2010).First principles calculations of advanced nitrides, oxides and alloys

I. Tanaka, A. Kuwabara, K. Yuge, A. Seko, F. Oba, and K. Matsunaga,

*Key. Eng. Mater.*,**403**, 73-76 (2009).Energetics and electronic structure of point defects in NaTaO

_{3}M. Choi, F. Oba, and I. Tanaka,

*AMTC Lett.*,**1**, 204-205 (2008).Structure and phase stability of nonstoichiometric compounds of tin oxides

A. Seko, A. Togo, F. Oba, and I. Tanaka,

*AMTC Lett.*,**1**, 198-199 (2008).Characterization of Ga

_{2}O_{3}:Mn thin films with room temperature ferromagnetismH. Hayashi, R. Huang, H. Ikeno, S. Sonoda, F. Oba, and I. Tanaka,

*AMTC Lett.*,**1**, 276-277 (2008).First-principles study of Co

*L*_{2,3}XANES and ELNES of trivalent cobalt compoundsY. Kumagai, H. Ikeno, F. Oba, K. Matsunaga, and I. Tanaka,

*AMTC Lett.*,**1**, 138-139 (2008).First-principles study on segregation and surface structures of Pt-Rh alloys

K. Yuge, A. Seko, Y. Koyama, A. Kuwabara, F. Oba, and I. Tanaka,

*ECS Trans.*,**11**, 749-758 (2007).Atomic-scale processes of grain-boundary faceting in a zirconia bicrystal

N. Shibata, F. Oba, T. Yamamoto, and Y. Ikuhara,

*Mater. Sci. Forum*,**558-559**, 955-958 (2007).Microstructure of interfaces made by epitaxial electrodeposition

F. Oba, R. Liu, E. W. Bohannan, F. Ernst, and J. A. Switzer,

*Interfaces in Electronic Materials, ed. by L. P. Cook, The Electrochemical Society Proceedings Series PV2003-31*, 101-110 (2006).Grain-boundary atomic structures in zirconia ceramics

N. Shibata, F. Oba, T. Yamamoto, and Y. Ikuhara,

*Ceram. Eng. Sci. Proc.*,**27**, 171-181 (2006).Identification of Mg vacancy in MgO by positron lifetime measurements and first-principles calculations

M. Mizuno, H. Araki, Y. Shirai, F. Oba, and I. Tanaka,

*Diffus. Defect Data. Pt. A Defect Diffus. Forum*,**242-244**, 1-7 (2005).Paraequilibrium surface alloying with interstitial solutes: A new concept for improving the performance of medical devices

F. Ernst, G. M. Michal, Y. Cao, N. Agarwal, H. Kahn, F. Oba, and A. H. Heuer,

*Proceedings of Materials & Processes for Medical Devices Conference*, Boston, Nov 14-16, 2005.Current-voltage characteristic and grain boundary structure in undoped and Pr and Co doped ZnO bicrystals

Y. Sato, F. Oba, M. Yodogawa, T. Yamamoto, and Y. Ikuhara,

*Proceedings of the 5th Pacific Rim International Conference on Advanced Materials and Processing (PRICM-5)*, Beijing, Nov 2-5, 2004 [Materials Science Forum, 475-479, 3867-3870 (2005).]Improvement of in-plane alignment and superconducting characteristics of SmBa

_{2}Cu_{3}O_{y}film on textured NiO/Ni substrate by using BaZrO_{3}buffer layerT. Izumi, K. Hasegawa, Y. Shiohara, Y. Sugawara, T. Hirayama, F. Oba, and Y. Ikuhara,

*Epitaxial Growth of Functional Oxides, ed. by A. Goyal, Y. Kuo, O. Leonte, and W. Wong-Ng, The Electrochemical Society Proceedings Series PV 2003-29*, 270-282 (2005).TEM Studies of Cu

_{2}O-Si and Cu_{2}O-InP interfaces made by epitaxial electrodepositionF. Oba, R. Liu, Y. Yu, E. W. Bohannan, F. Ernst, J. A. Switzer,

*Proceedings of Microscopy & Microanalysis*, Savannah, Georgia, USA, August 1-5, 2004.Electronic states associated with bond disorder at ZnO grain boundaries

F. Oba, I. Tanaka, and H. Adachi,

*Adv. Quantum Chem.*,**42**, 175-186 (2003).First-principles calculations of silicon nitrides and SiAlONs

I. Tanaka, K. Tatsumi, F. Oba, and H. Adachi,

*Key. Eng. Mater.*,**247**, 149-153 (2003).Atomic and electronic structure of symmetric tilt boundaries in ZnO

F. Oba, S. R. Nishitani, H. Adachi, I. Tanaka, M. Kohyama, and S. Tanaka,

*Mater. Res. Soc. Symp. Proc.*,**654**, AA1.2.1-6 (2001).Interaction of Co impurities and native defects in ZnO

F. Oba, T. Yamamoto, Y. Ikuhara, I. Tanaka, and H. Adachi,

*Proceedings of the 4th Pacific Rim International Conference on Advanced Materials and Processing (PRICM4)*,**1**, 555-558 (2001).First principles calculations of oxygen-vacancies in oxides

I. Tanaka, F. Oba, K. Tatsumi, M. Nakano, and H. Adachi,

*Proceedings of the 4th Pacific Rim International Conference on Advanced Materials and Processing (PRICM4)*,**1**, 545-548 (2001).Electronic structure calculation of symmetric tilt boundaries in ZnO

F. Oba, S. R. Nishitani, H. Adachi, and I. Tanaka,

*Ceram. Trans.*,**118**, 223-230 (2000).First-principles calculation of optical spectra for transition-metal impurities doped in ZnO and ZnS

K. Ogasawara, T. Ishii, F. Oba, I. Tanaka, and H. Adachi,

*Mater. Res. Soc. Symp. Proc.*,**560**, 341-346 (1999).The role of Co ions on the appearance of non-linear I-V characteristics of ZnO-based ceramics

M. Yodogawa, Y. Ikuhara, F. Oba, and I. Tanaka,

*Key Eng. Mater.*,**157-158**, 249-255 (1999).Interaction between oxygen and 3d transition-metal impurities on ZnO (10-10) surface

F. Oba, I. Tanaka, K. Ogasawara, and H. Adachi,

*Proceedings of US-Japan Workshop on Electrically Active Ceramic Interfaces*, 141-144 (1998).

## Books¶

First-principles approaches to defect energetics in ZnO: A review

F. Oba,

Chapter publication in

*Zinc oxide, the future material for electronics: A Comprehensive review on ZnO physics and defects (Research Signpost, Trivandrum)*, 1-23 (2012).

## Invited Talks at International Conferences¶

Complex behavior of point defects in functional oxides and nitrides: Insights from first principles

F. Oba,

Energy Materials Nanotechnology Summer Meeting, Cancun, Jun. 10, 2014

Band alignment of zinc-blende and chalcopyrite semiconductors: Effects of misfit dislocations

F. Oba,

APS March Meeting 2014, Denver, Mar. 3, 2014

Point defects in oxide and nitride semiconductors: Understanding and prediction toward material screening

F. Oba,

2013 MRS Fall Meeting, Boston, Dec. 3, 2013

Complex behavior of defects in oxide semiconductors: Insights from first-principles calculations

F. Oba,

International Symposium on Compound Semiconductors 2013 (ISCS2013), Kobe, May. 21, 2013

Complex behavior of point defects in oxide and nitride semiconductors: Insights from density functional calculations

F. Oba,

The 5th International Symposium on Designing, Processing and Properties of Advanced Engineering Materials (ISAEM-2012), Toyohashi, Nov. 8, 2012

Native point defects in functional oxides: An approach from first principles

F. Oba,

Materials Science & Technology 2011, Columbus, Oct. 19, 2011

Density functional approach to point defects in oxide semiconductors

F. Oba,

3rd International Congress on Ceramics(ICC3), Osaka, Nov. 15, 2010

Point defects in oxide semiconductors: A density functional approach

F. Oba,

4th International Conference on the Science and Technology for Advanced Ceramics(STAC-4), Yokohama, Jun. 23, 2010

Energetics and electronic structure of native defects and dopants in ZnO

F. Oba,

12th International Ceramics Congress, Montecatini Terme, Jun. 10, 2010

Point defects in oxide semiconductors: An approach from first principles

F. Oba,

The 3rd Theory Meets Industry International Workshop, Nagoya, Nov. 13, 2009

Room temperature ferromagnetism in manganese-doped gallium oxide

F. Oba, H. Hayashi, R. Huang, H. Ikeno, S. Sonoda, and I. Tanaka,

Materials Science & Technology 2007, Detroit, Sep. 19, 2007

Microstructure of interfaces made by epitaxial electrodeposition

F. Oba, R. Liu, E. W. Bohannan, F. Ernst, and J. A. Switzer,

204th Meeting of the Electrochemical Society, Orlando, Oct. 14, 2003