The electronic structure and phase stability of MgO, ZnO, CdO, related alloys in the rocksalt (B1), zincblende (B3), wurtzite (B4) crystal structures were examined within first-principles band theory; thermodynamically stable phases are reproduced for each material. alignment band-gap deformation potentials analyzed, showing an increase valence maximum from Mg to Zn Cd. Ternary alloy formation was explored through application special quasirandom method. B1 is over all (Mg,Cd)O compositions,...

Magnetic properties of iron chalcogenide superconducting materials are investigated using density-functional calculations. We find that the stability magnetic phases is very sensitive to height chalcogen species from Fe plane: while FeTe with optimized Te has double-stripe ($\ensuremath{\pi}$, 0) ordering, single-stripe $\ensuremath{\pi}$) ordering becomes ground state when lowered below a critical by, e.g., Se doping. This behavior understood by opposite Te-height dependences superexchange...

We study the electronic and magnetic properties of single-wall carbon nanotubes filled with Fe nanowires through local-spin-density-functional calculations. find that moments Fe-filled for ferromagnetic state are greatly enhanced due to reduced coordination number atoms on nanowire surface, compared bulk Fe. The increase is more effective thin nanowires, where interact very weakly nanotube thus their inside tube similar those free-standing nanowires. For thick undercoordinated strongly...

Band-gap bowing coefficients in large size-mismatched II-VI alloys ${M}^{\mathit{II}}{X}_{1\ensuremath{-}x}^{\mathit{VI}}{\mathrm{O}}_{x}$ with ${M}^{\mathit{II}}=\mathrm{Zn}$ and Cd, ${X}^{\mathit{VI}}=\mathrm{S}$, Se, Te the zinc-blende structure are calculated using first-principles methods. We show that these systems, composition dependent. The increase as size chemical mismatch between constituents increase. for Zn larger than corresponding Cd alloys, but smaller III-V alloys. results...

The origin of the ballistic hole gas recently observed in Ge/Si core−shell nanowires has not been clearly resolved yet, although it is thought to be result band offset at radial interface. Here we perform spin-polarized density-functional calculations investigate defect levels surface dangling bonds and Au impurities Si shell. Without any doping strategy, find that bond substitutional defects behave as charge traps, generating carriers Ge core, while their are very deep one-component...

We report anisotropic Dirac-cone surface bands on a side-surface geometry of the topological insulator Bi${}_{2}$Se${}_{3}$ revealed by first-principles density-functional calculations. find that electron velocity in Dirac cone is anisotropically reduced from (111)-surface cone, and not parallel with wave vector k except for high-symmetry directions. The size spin depends direction due to variation noncollinearity state. anisotropy electronic structures follows corresponding atomic...

We have investigated the band structure of zinc-blende (ZB) Hg chalcogenides using a corrected local density approximation method. find that gaps HgS, HgSe, and HgTe are 0.30, $\ensuremath{-}0.24$, $\ensuremath{-}0.31\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, respectively. That is, HgS has positive gap, whereas HgSe inverted structures. The chemical trend is explained by atomic energy levels sizes, as well related deformation potentials for these compounds. also show systematically how gap can...

We perform first-principles pseudopotential calculations to investigate the oxidation process by oxygen gas exposure in single-wall carbon nanotubes with a closed tip. Oxygen molecules can be initially adsorbed either on tube cap or wall, keeping their molecular form, then, successive transformation occurs into stable geometry broken C-C and O-O bonds. The broken-bond configuration of oxidated is suggested precursor for etching away particularly, small diameters, while oxidative suppressed...

First-principles calculations are performed to investigate the stability of dopant-related defects and dependence doping efficiency on wire diameter orientation in hydrogen-passivated silicon nanowires doped with B P dopants. As decreases below a critical value, it is energetically more favorable for donor atoms form donor-pair defects, which consist two donors separated at nearest-neighbor distance. While unstable bulk Si, these greatly enhanced because confinement effect nanostructures,...

A new group of hybrid organic−inorganic materials, AIIBVI(en)0.5 (A = Zn and Cd B S, Se, Te), have been shown to exhibit a number unusual structurally dependent properties that are not typically found in conventional inorganic organic materials. However, it is puzzling for given component the crystal comes different phases often favors one over another. Using first-principles methods, we study structural electronic (e.g., stability band gap) three observed phases: αI, αII, β. The general...

The two-particle vertex function contains all scattering processes from the electron-hole interaction and is a key component in evaluating susceptibilities. A study demonstrates how its orbital-selective, dynamic nature determines peak structure of spin susceptibility momentum space for Hund's metallic Sr${}_{2}$RuO${}_{4}$ within DFT + DMFT framework, which turn leads to specific superconducting gap symmetries.

We show that each surface atom of heavily boron-doped, (111)-oriented silicon with a √3 × reconstruction has electrically switchable two charge states due to the strong electron-lattice coupling at this surface. The structural and electronic properties as well their energetics are uncovered by employing scanning tunneling microscopy measurements density functional theory calculations, which reveals one is two-electron bound state or bipolaron. also execute single-atom bit operations on...

We investigate the evolution of electronic structure ${\mathrm{NiS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$ alloys with varying temperature and composition $x$ by using combined approach density-functional theory dynamical mean-field theory. Adopting realistic alloy structures containing S Se dimers, we map their correlation strength on phase diagram observe metal-insulator transition (MIT) at $x=0.5$, which is consistent experimental measurements. The dependence local magnetic susceptibility...

We perform first-principles pseudopotential calculations to investigate the dielectric response for ${\mathrm{MgB}}_{2}$, and calculate Coulomb repulsion parameter ${\ensuremath{\mu}}^{*}$ using full matrix approach. The calculated value is 0.118 when Debye energy ${\ensuremath{\omega}}_{D}$ of ${\mathrm{MgB}}_{2}$ used phononic cutoff ${\ensuremath{\omega}}_{c}$, while ${\ensuremath{\mu}}^{*}=0.151$ ${\ensuremath{\omega}}_{c}=0.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. find that local-field...

We investigate the evolution of magnetic properties as a function hydrogen doping in iron based superconductor LaFeAsO$_{1-x}$H$_x$ using dynamical mean-field theory combined with density-functional theory. find that two independent consequences doping, increase electron occupation and structural modification, have opposite effects on strength correlation magnetism, resulting minimum calculated moment around intermediate level $x$. Our result provides natural explanation for puzzling recent...

Study of superconductivity in layered iron-based materials was initiated 2006 by Hosono's group, and boosted 2008 the superconducting transition temperature, Tc, 26 K LaFeAsO1-xFx. Since then, enormous researches have been done on materials, with Tc reaching as high 55 K. Here, we review briefly experimental theoretical results atomic electronic structures magnetic properties FeAs-based superconductors related compounds. We seek for clues unconventional materials.

We predict atomic, electronic, and magnetic structures of a hypothetical compound LaFeSbO by first-principles density-functional calculations. It is shown that prefers an orthorhombic stripe-type antiferromagnetic phase [i.e., spin-density wave (SDW) phase] to the tetragonal nonmagnetic (NM) phase, with larger Fe spin moment greater SDW-NM energy difference than those LaFeAsO. In NM-phase LaFeSbO, electronic bandwidth near Fermi reduced compared LaFeAsO, indicating smaller orbital overlap...

Despite of the importance magnetism in possible relation to other key properties iron-based superconductors, its understanding is still far from complete especially for FeSe systems. On one hand, origin absence magnetic orders bulk yet be clarified. it not clear how close monolayer on SrTiO$_3$, with highest transition temperature among a instability. Here we investigate and using dynamical mean-field theory combined density-functional theory. We find that suppressed order associated...

We investigate defect properties in hexagonal boron nitride (hBN) which is attracting much attention as a single photon emitter. Using first-principles calculations, we find that nitrogen-vacancy <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M3"> <a:mfenced open="(" close=")" separators="|"> <a:mrow> <a:msub> <a:mi>V</a:mi> </a:mrow> <a:mi>N</a:mi> </a:msub> </a:mfenced> </a:math> has lower energy structure <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" id="M4"> <f:msub>...

Atomic ordering from random alloys results in a peculiar evolution of electronic structures. Utilizing this property, we show theoretically that the directness band gap can be manipulated by forming ordered specific atomic configurations. For example, ${\mathrm{Ga}}_{4}\mathrm{N}{\mathrm{As}}_{3}$ have an indirect if it forms luzonite structure, despite constituents GaN and GaAs zinc-blende (ZB) their alloys, all direct gaps. On other hand, ${\mathrm{Al}}_{2}\mathrm{N}\mathrm{P}$ CuPt...

We perform first-principles pseudopotential calculations to investigate the atomic structure and energetics of various defects consisting B P impurities effect on diffusion in Si. In equilibrium case, we find that a B-P pair is energetically most stable when positioned at second-neighbor site B. When excess Si interstitials are generated by implantation, tend form ${I}_{s}$-B-P complexes with self-interstitials ${(I}_{s}),$ where still prefers B, particularly for high donor concentrations....

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation J.‐S. Park, B. Ryu, C.‐Y. Moon, K. J. Chang; Hole Gas Induced by Defects in Ge/Si Core‐Shell Nanowires. AIP Conference Proceedings 23 December 2011; 1399 (1): 303–304. https://doi.org/10.1063/1.3666374 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks...

A charged vacancy on the Si surface, which generates deep levels within band gap to accommodate multiple charge states, becomes increasingly important with device scaling. Yet its characteristics have not been addressed as comprehensively bulk in Si. Here we generate adatom vacancies a heavily B doped Si(111) surface and measure their structural electronic properties by using scanning tunneling microscopy. We find that they are Jahn-Teller distorted ground state but undergo...

Magnetic interactions among substitutional dopant impurities in silicon nanowires are investigated theoretically using density functional calculations. Our results show that while have no magnetic ordering the ground state, a moment imposed at an impurity by applying effective local field induces moment, smaller magnitude and opposite sign, adjacent impurity, demonstrating antiferromagnetic coupling between spins. The sign of calculated Heisenberg exchange parameter $J$ spins also...