89 citations · 678 across the 24 of their papers we have counts for
24 papers
Exploration of a new reconstructed structure on GaN(0001) surface by Bayesian optimization
Akira Kusaba, Yoshihiro Kangawa, Tetsuji Kuboyama +1
GaN(0001) surfaces with Ga- and H-adsorbates are fundamental stages for epitaxial growth of semiconductor thin films. We explore stable surface structures with nanometer scale by t…
Order- orbital-free density-functional calculations with machine learning of functional derivatives for semiconductors and metals
Fumihiro Imoto, Masatoshi Imada, Atsushi Oshiyama
Orbital-free density functional theory (OFDFT) offers a challenging way of electronic-structure calculations scaled as computation for system size . We here dev…
Screw dislocation that converts p-type GaN to n-type: Microscopic study on the Mg condensation and the leakage current in p-n diodes
Takashi Nakano, Yosuke Harashima, Kenta Chokawa +9
Recent experiments suggest that Mg condensation at threading dislocations induce current leakage, leading to degradation of GaN-based power devices. To study this issue, we perform…
Structural stability and energy levels of carbon-related defects in amorphous SiO and its interface with SiC
Yu-ichiro Matsushita, Atsushi Oshiyama
We report the density-functional calculations that systematically clarify the stable forms of carbon-related defects and their energy levels in amorphous SiO using the melt-que…
Unfolding energy spectra of multi-periodicity materials
Yu-ichiro Matsushita, Hirofumi Nishi, Jun-ichi Iwata +2
We propose a new unfolding scheme to analyze energy spectra of complex large-scale systems which are inherently of multi-periodicity. Considering twisted bilayer graphene (tBLG) as…
A novel intrinsic interface state controlled by atomic stacking sequence at interfaces of SiC/SiO
Yu-ichiro Matsushita, Atsushi Oshiyama
On the basis of ab-initio total-energy electronic-structure calculations, we find that interface localized electron states at the SiC/SiO interface emerge in the energy region…
Microscopic Mechanism of Carbon Annihilation upon SiC Oxidation due to Phosphorous Treatment: Density-Functional Calculations Combined with Ion Mass Spectrometry
Takuma Kobayashi, Yu-ichiro Matsushita, Takafumi Okuda +2
We report first-principles static and dynamic calculations that clarify the microscopic mechanism of carbon annihilation due to phosphorous treatment upon oxidation of silicon carb…
Comprehensive study on band-gap variations in -bonded semiconductors: roles of electronic states floating in internal space
Yu-ichiro Matsushita, Atsushi Oshiyama
We have performed electronic structure calculations to explore the band-gap dependence on polytypes for -bonded semiconducting materials, i.e., SiC, AlN, BN, GaN, Si, and dia…
Mechanisms of initial oxidation of 4H-SiC (0001) and (000) surfaces unraveled by first-principles calculations
Yu-ichiro Matsushita, Atsushi Oshiyama
We have performed electronic state calculations to clarify the initial stage of the oxidation of the Si- and C-faces in 4H-SiC based on the density-functional theory. We investigat…
Microscopic mechanisms of initial formation process of graphene on SiC(0001) surfaces
Fumihiro Imoto, Jun-Ichi Iwata, Mauro Boero +1
We report total-energy calculations based on the density-functional theory that clarify microscopic mechanisms of initial stage of graphene formation on the SiC(0001) surface. We e…
First-principles calculations that clarify energetics and reactions of oxygen adsorption and carbon desorption on 4H-SiC () surface
Han Li, Yu-ichiro Matsushita, Mauro Boero +1
We report static and dynamic first-principles calculations that provide atomistic pictures of the initial stage of the oxidation processes occurring at the () surface of…
Atomic Force Microscope manipulation of Ag atom on the Si(111) surface
Batnyam Enkhtaivan, Atsushi Oshiyama
We present first-principles total-energy electronic-structure calculations that provide the microscopic mechanism of the Ag atom diffusion between the half unit cells (HUCs) on the…
Band-unfolding approach to Moirè-induced band-gap opening and Fermi-level-velocity reduction in twisted bilayer graphene
Hirofumi Nishi, Yu-ichiro Matsushita, Atsushi Oshiyama
We report on the energy spectrum of electrons in twisted bilayer graphene (tBLG) obtained by the band-unfolding method in the tight-binding model. We find the band-gap opening at p…
Multi-step atomic reaction enhanced by an atomic force microscope probe on Si(111) and Ge(111) surfaces
Batnyam Enkhtaivan, Atsushi Oshiyama
We present first-principles total-energy electronic-structure calculations that provide the microscopic mechanism of the adatom interchange reaction on the Sn- and Pb-covered Ge(11…
A precaution for the hybrid density functional calculation of open-shell systems
Jun-Ichi Iwata, Keisuke Sawada, Atsushi Oshiyama
We show that a naive treatment of open-shell systems in hybrid density functional calculations ignoring the spin dependence causes significant errors due to a kind of self interact…
Structural Evolution and Optoelectronic Applications of Multilayer Silicene
Zhi-Xin Guo, Yue-Yu Zhang, Hongjun Xiang +2
Despite the recent progress on two-dimensional multilayer materials (2DMM) with weak interlayer interactions, the investigation on 2DMM with strong interlayer interactions is far f…
Spontaneous Appearance of Low-dimensional Magnetic Electron System on Semiconductor Nanostructures
Keisuke Sawada, Jun-Ichi Iwata, Atsushi Oshiyama
We find that spin-polarized ground states emerge in nanofacets which are self-organized on SiC (0001) surfaces. Our large-scale density-functional calculations reveal that the nano…
Structural stability and energy-gap modulation through atomic protrusion in freestanding bilayer silicene
Yuki Sakai, Atsushi Oshiyama
We report on first-principles total-energy and phonon calculations that clarify structural stability and electronic properties of freestanding bilayer silicene. By extensive struct…
Crossover between Silicene and Ultra-Thin Si Atomic Layers on Ag(111) Surfaces
Zhi-Xin Guo, Atsushi Oshiyama
We report on total-energy electronic structure calculations in the density-functional theory performed for the ultra-thin atomic layers of Si on Ag(111) surfaces. We find several d…
Interstitial Channels that Control Band Gaps and Effective Masses in Tetrahedrally Bonded Semiconductors
Yu-ichiro Matsushita, Atsushi Oshiyama
We find that electron states at the bottom of the conduction bands of covalent semiconductors are distributed mainly in the interstitial channels and that this floating nature lead…
Structural Tristability and Deep Dirac States in Bilayer Silicene on Ag(111) Surfaces
Zhi-Xin Guo, Atsushi Oshiyama
We report on total-energy electronic-structure calculations in the density-functional theory performed for both monolayer and bilayer silicene on Ag(111) surfaces. The rt3 x rt3 st…
New Identification of Metallic Phases of In Atomic layers on Si(111) Surfaces
Kazuyuki Uchida, Atsushi Oshiyama
We report first-principles calculations that clarify atomic structures and coverage of the metallic phases of In overlayers on Si (111) surfaces. Calculated energy bands and scanni…
Absence of Dirac Electrons in Silicene on Ag (111) Surfaces
Zhi-Xin Guo, Shinnosuke Furuya, Jun-ichi Iwata +1
We report first-principles calculations that clarify stability and electronic structures of silicene on Ag(111) surfaces. We find that several stable structures exist for silicene/…
Comparative study of hybrid functionals applied to structural and electronic properties of semiconductors and insulators
Yu-ichiro Matsushita, Kazuma Nakamura, Atsushi Oshiyama
We present a systematic study that clarifies validity and limitation of current hybrid functionals in density functional theory for structural and electronic properties of various…