Materials Literature
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Zinc ferrite films were deposited on fused quartz substrate at different temperatures using pulsed laser ablation (PLA) and rf sputtering. X-ray diffraction indicated that all the films were single phase ZnFe2O4 with grain growing in the range of 8–80nm with substrate temperature. The nanocrystalline films were found…
Both band gap engineering and spatial confinement of optical phonon were observed depending upon the size of ZnO quantum dots at room temperature. Size-dependent blueshifts of photoluminescence and absorption spectra reveal the quantum confinement effect. The measured Raman spectral shift and asymmetry for the E2(high…
In recent decades, novel magnetism of d- and f-electron compounds has been discussed very intensively both in experimental and theoretical research fields of condensed matter physics. It has been recognized that these material groups are in the same category of strongly correlated electron systems, while the low-energ…
The radiative recombination coefficient B in crystalline bulk silicon is enhanced by the Coulomb attraction between electrons and holes. This effect is weakened at high carrier densities due to screening. We measure the resulting dependence of B on the free-carrier density (i) by reinterpreting published data and (ii)…
The field-theory model is proposed to study the electronic states near the Fermi energy in spheroidal fullerenes. The low energy electronic wavefunctions obey a two-dimensional Dirac equation on a spheroid with two kinds of gauge fluxes taken into account. The first one is so-called K spin flux which describes the exc…
We investigate weaker than usual constitutive assumptions in linear Cosserat theory still providing for existence and uniqueness and show a continuous dependence result for Cosserat couple modulus μc → 0.This result is needed when using Cosserat elasticity not as a physical model but as a numerical regularization devi…
We numerically study the quantum Hall effect (QHE) in graphene based on a lattice model in the presence of disorder. Two distinct QHE regimes are identified in the energy band with unconventional ``half-integer'' QHE appearing near the band center, in agreement with the experimental observation. A topological invarian…
We investigate temperature dependent electronic correlation effects in the conduction bands of Gadolinium Nitride (GdN) based on the combination of many body analysis of the multi-band Kondo lattice model and the first principles TB-LMTO bandstructure calculations. The physical properties like the quasi-particle densi…
Recent optical absorption and emission experiments showed that the lower energy optical transitions in carbon nanotubes are excitonic in nature, as predicted by theory. These experiments were based on the symmetry aspects of free electron-hole states and bound excitonic states. The present work shows, however, that gr…
Energies of a certain class of fullerene molecules (elongated, contracted, and regular icosahedral fullerenes) are numerically calculated using a microscopic description of carbon-carbon bonding. It is shown how these results can be interpreted and comprehended using the theory of elasticity that describes bending of…
We have studied ferroelectricity in Dion-Jacobson CsBiNb2O7 from first principles. Using group-theoretical analysis and first-principles density functional calculations of the total energy and phonons, we perform a systematic study of the energy surface around a paraelectric prototypic phase. Our results suggest that…
Electronic and thermodynamic properties of β-Ga2O3 are investigated in the framework of density functional theory. The equilibrium structural parameters and Debye temperature are obtained through fitting of the energy surface to the equation of state. Analysis of the band structure shows the valence band maximum to be…
ZnO quantum dots (QDs) of controlled sizes have been fabricated by a simple sol-gel method. The blueshift of room-temperature photoluminescence measurement from free exciton transition are observed decreasing with the QD size that is ascribed to the quantum confinement effect. From the resonant Raman scattering, the c…
The bending Young's modulus of ZnO nanobelts was measured by performing three-point bending tests directly on individual nanobelts with an atomic force microscope (AFM). The surface-to-volume ratio has no effect on the bending Young's modulus of the ZnO nanobelts for surface-to-volume ratios ranging from 0.017 to 0.03…
We experimentally investigate the crystallization of a uniformly heated quasi-2D granular fluid as a function of the filling fraction. Our experimental results for the Lindemann melting criterion, the radial distribution function, the bond order parameter, and the statistics of topological changes at the particle leve…
Using first-principles calculations we show that the work function of noble metals can be decreased or increased by up to 2 eV upon the adsorption of self-assembled monolayers of organic molecules. We identify the contributions to these changes for several (fluorinated) thiolate molecules adsorbed on Ag(111), Au(111)…
Magnetic field and temperature dependence of the terahertz conductivity and permittivity of the colossal magnetoresistance manganite ${\mathrm{Pr}}_{0.65}{\mathrm{Ca}}_{0.28}{\mathrm{Sr}}_{0.07}\mathrm{Mn}{\mathrm{O}}_{3}$ (PCSMO) is investigated approaching the metal-to-insulator transition (MIT) from the insulating…
We present a phenomenological model of melting in nanoparticles with facets that are only partially wet by their liquid phase. We show that in this model, as the solid nanoparticle seeks to avoid coexistence with the liquid, the microcanonical melting temperature can exceed the bulk melting point, and that the onset o…
Crystallization of calcite from different concentrated calcium chloride solutions by the CO(2) vapor diffusion technique in the presence of polystyrenesulfonate (PSS) yields defined assemblies of nanoparticles with unusual morphology. From the typical calcite rhombohedra, the morphology can be systematically varied vi…
Raman spectra of ZnO and Co substituted ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}\mathrm{O}$ (ZCO) were carried out using the Raman microprobe system with an ${\mathrm{Ar}}^{+}$ ion laser source of $514.5\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ wavelength. The shift towards the lower frequency side of the nonp…