Theoretical predictions of structural electronic and optical properties of vanadium ferrite

The structural properties of Vanadium Ferrite VFe2O4 are reported for temperature range 0–1000 K using Density Functional Theory. A comparative study with the available experimental and theoretical data in the literature is also presented. Effects of temperature on lattice constant, volume and bulk modulus are deduced that with the increase in temperature, bulk modulus decreases and lattice constant slightly increases. This proves that the material VFe2O4 remains in the same cubic phase for temperature range 0–1000 K. In addition, the optical response is observed with six optical constants like absorption, reflectivity, eloss, dielectric functions, refraction and optical conductivity. Band structures and electronic density of states are also computed by using TB-mBJ potential. We hope that our findings would provide a help to experimentalists in fabricating VFe2O4 for temperature-sensitive optical devices.

Photoluminescence features of LiNbO3:Zn (0,04÷2,01 mol. %) crystals.

The main contribution to the luminescence of LiNbO3 : Zn (0,04 ÷ 2,01 mol. %) at 420 and 440 nm was established to be due to two electro-hole pairs of Nb4+–O-in niobium octahedron. Moreover, the luminescence weakly depends on Li / Nb ratio and Zn concentration. The increase of Zn concentration to 2,01 mol. % ZnO leads to monotonically increasing intensity in long-wave region of the photoluminescent spectra. This fact indicates that there are shallow energy levels near bottom of the conductivity band. Also the features of hydrogen bonds in LiNbO3structure effects on the location of the shallow energy levels as the complex defects caused by OH-group in the structure can contribute to the photoluminescence.

Electron Spectroscopy of CdMeTe Nanostructures Created on CdTe Surface Under Ion Bombardment

The electronic structure of CdMeTe nanostructures was studied by a variety of techniques of secondary and photoelectron spectroscopy. Particularly, for the first time it has been shown that in the conductivity band of the CdZnTe films there are maximums peaks of free electronic states with energies 3.5 and 4.4 eV relative Ev.

Transport Phenomena In Single Crystals Tl1−XIn1−XGeXSe2 (x=0.1, 0.2)

Temperature dependences of electroconductivity for single crystals Tl1−xIn1−xGexSe2 were analyzed. It was established an occurrence of thermoactivated states within the temperature range 100-300 K. The conductivity is formed by delocalized carriers within the conductivity band and the jumping conductivity over the localized states which are situated in the narrow localized states near the Fermi level. Following the performed data the activation energy was evaluated with accuracy up to 0.02 eV. The density of the localized states as well as the distribution of the energy over the mentioned states was evaluated. Additionally the average distance between the localized states is evaluated at different temperatures.

Introduction to low frequency local plasmons in bulk extrinsic semiconductors

It is shown that restoring force acts on the electronic cloud of the outer electrons of a neutral or charged impurity atom when it is shifted relative to the inner charged core (or expanded). Because of this the dipole oscillations arise which influence considerably the dispersion law of the plasma oscillations in bulk extrinsic semiconductors. Assuming that only one transition of electron from the ground state to the first excited state is essential, the dispersion law is calculated. It is shown that the calculated dispersion law consists of two separate branches, one of them originates from the regular plasma oscillations of the free electrons of a conductivity band, and the other one stems from the local oscillations of the outer electrons bounded to the impurity atoms.

Radiative Recombination Rates in GaN, InN, AlN and their Solid Solutions

The radiative recombination rates have been calculated for the first time in the wide band gap wurtzite semiconductors GaN, InN and AIN and their solid solutions GaxAl1−xN and InxAl1−xN on the base of existing data on the energy band structure and optical absorption in these materials. We calculated the interband matrix elements for the direct optical transitions between the conductivity band and the valence one using the experimental photon energy dependence of the absorption coefficient near the band edge. In our calculations we assumed that the material parameters of the solid solutions (the interband matrix element, carrier effective masses and so on) could be obtained by a linear interpolation between their values in the alloy components. The temperature dependence of the energy gap was taken in the form proposed by Varshni. The calculations of the radiative recombination rates were performed in the wide range of temperature and alloy compositions.

The Rate of Radiative Recombination in the Nitride Semiconductors and Alloys

The radiative recombination rates have been calculated for the first time in the wide band gap wurtzite semiconductors GaN, InN and AlN and their solid solutions GaxAl1−xN and InxAl1−xN on the base of existing data on the energy band structure and optical absorption in these materials. We calculated the interband matrix elements for the direct optical transitions between the conductivity band and the valence one using the experimental photon energy dependence of the absorption coefficient near the band edge. In our calculations we assumed that the material parameters of the solid solutions (the interband matrix element, carrier effective masses and so on) could be obtained by a linear interpolation between their values in the alloy components. The temperature dependence of the energy gap was taken in the form proposed by Varshni. The calculations of the radiative recombination rates were performed in the wide range of temperature and alloy compositions.