Electrical properties of antimony telluride

We investigate the effects of the ambient temperature (T), both temperature (T _a )and time (t _a )of annealing on the electrical conductivity (), and the Seebeck coefficient (S) of Sb₂Te₃. We concluded that both holes and electrons can participate to the conduction process. The material behaves as a semimetal. Although the Seebeck coefficient possesses a plus sign, the coefficient of S vs. plots was negative as a degenerate semiconductor. The decrease in value of S with increasing t _a was attributed to a corresponding decrease in the amount of positional disorder which acts as an electron trap center.     

Electrical and thermoelectric properties of antimony telluride and cadmium sulfide films

Films of p-type Sb₂Te₃ and of n-type CdS have been examined for Hall effect, electrical conductivity, and differential thermo-emf; concentration, mobility, and activation energy are derived. The mobility in CdS is increased by indium doping.     

Electrophysical characteristics of epitaxial cadmium telluride films

Equilibrium electrophysical characteristics of epitaxial CdTe films grown by the thermal screen method and the quasiclosed volume method are investigated. It is established that the films in both cases are semiconductors with inhomogeneous potential relief of the band to whose formation the main contribution is from barriers on the boundaries of the growth patterns. It is shown that jump conductivity with a variable jump length due to inhomogeneity of the potential relief of the bands and the high states density at the Fermi level is observed in CdTe films synthesized by the quasiclosed volume method for relatively high temperatures.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 72–76, March, 1990.     

Structural and optical properties of thermally evaporated antimony telluride thin films

Antimony telluride thin films were prepared on the well-cleaned glass substrates under a pressure of 10 – 5 torr by thermal evaporation method. The thicknesses of the films were measured using Multiple Beam Interferometer (MBI) technique. The structure of the sample was analyzed by X-ray diffraction technique. The film attains crystalline structure as the temperature of the substrate is increased to 373 K. The d spacing and the lattice parameters of the sample were calculated. Optical behavior of the film samples with the various thicknesses was analyzed by obtaining their transmittance spectra in the wavelength range of 400 – 800 nm. The transmittance is found to decrease with increase in film thickness and also it falls steeply with decreasing wavelength. The optical constants were estimated and the results are discussed. The optical band gap energy decreases with increase in the film thickness. The optical transition in these films is found to be indirect and allowed. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

High pressure study of structural and electronic properties of magnesium telluride

The full-potential linear muffin-tin orbital method (FP-LMTO) within the local density approximation (LDA) is used to calculate the electronic band structures and the total energies of MgTe in its stable (NiAs-B8) and high pressure phases. The latter provide us with the ground state properties such us lattice parameter, bulk modulus and its pressure derivatives. The transition pressure at which this compound undergoes the structural phase transition from the NiAs to CsCl phase is calculated. The energy band gaps and their volume and pressure dependence in the stable NiAs-B8 phase are investigated. The ground state properties, the transition pressure are found to agree with the experimental and other theoretical results. The elastic constants at equilibrium in both NiAs and CsCl structure are also determined.     

Electrophysical properties of gallium arsenide in combination with impurity-doped germanium and isovalent indium and antimony impurities

The temperature dependence of the charge carrier concentration and mobility in n-type GaAs monocrystals doped jointly by Ge and isovalent In and Sb impurities is investigated. The observable charge carrier concentration and mobility changes in the GaAs:Ge:In and GaAs:Ge:Sb are compared with the corresponding characteristics in GaAs:Ge, and the change in properties along the ingots can be explained by the Ge impurity redistribution in the gallium and arsenic sublattices in the presence of an isovalent impurity.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 3–8, September, 1987.     

Preparation and characterization of the antimony telluride hexagonal nanoplates

Nanostructured thermoelectric materials are of much interest for improving the thermoelectric figure of merit. In the present work, Sb₂Te₃ hexagonal nanoplates were successfully fabricated via a facile hydrothermal method. The products were characterized by means of X-ray diffraction, field-emission scanning electron microscope, transmission electron microscope and energy-dispersive X-ray spectroscopy. The results show that the typical Sb₂Te₃ crystal is hexagonal in shape with about 35 nm in thickness and 300 nm in edge length. The mechanism for formation of Sb₂Te₃ hexagonal nanoplates is primarily discussed.     

Correlation of structural and electronic properties in a new low-dimensional form of mercury telluride

Using high resolution electron microscopy and first principles quantum mechanical calculations we have explored the fundamental physics and chemistry of the semiconductor, HgTe grown inside single wall carbon nanotubes. This material forms a low-dimensional structure based on a repeating Hg2Te2 motif in which both atom species adopt new coordination geometries not seen in the bulk. Density-functional theory calculations confirm the stability of this structure and demonstrate conclusively that it arises solely as a consequence of constrained low dimensionality. This change is directly correlated with a modified electronic structure in which the low-dimensional form of HgTe is transformed from a bulk semimetal to a semiconductor.     

Band structure and electronic properties of InP

A combination of the pseudopotential method with thek,p method was used to calculate the complete band structure of InP. The pseudopotential form factors were determined by fitting to conduction band energy spacings, optical spectra, and density of states properties. Effective masses for important conduction band minima and pressure coefficients for some transiton energies were evaluated and compared with experimental data as far as possible.     

Optical properties and electronic structure of US

The optical properties of uranium sulphide single crystals have been determined for the first time. An excellent agreement is found between the structure in the optical spectrum and the results of a self-consistent cellular multiple scattering calculation. The results evidence that the 5? electrons form a resonance state at E_F and that the 5??6d coupling produces a dip in the 6d density of states near E_F which is responsible for many peculiar properties of US.     

Optical properties of zinc telluride with cadmium telluride submonolayers

Reflection, luminescence, and Raman spectra of epitaxial ZnTe layers nominally incorporating double CdTe submonolayers were studied. The band of an exciton localized at the potential produced by narrow-gap planar inclusions dominated the luminescence of these heterostructures. The emission parameters of localized excitons (specifically, the ratio of integral emission intensity to localization energy) were determined, and it was found that excitons interact with longitudinal optical phonons of the layer enriched with cadmium. Giant amplification of the Stokes component resonant with the localized exciton level was observed in Raman scattering.     

XANES studies of unoccupied electronic states and local real structure of some antimony chalcogenides

Summary The X-rayL absorption edges of antimony and iodine in SbSI, Sb₂S₃, Sb₂S₅ have been measured with high resolution using synchrotron radiation. It is shown that the density of the unoccupied levels in the conduction band is adequate to interpret the edge structures between 0 and 10 eV. These structures and the chemical shifts of the three compounds are compared: a striking similarity of the electric charge of antimony and of the electronic structure in the bottom of the conduction band is found. The structures between 10 and 50 eV are analysed and interpreted in terms of stereochemical co-ordination. The nonexistence of Sb₂S₅ as a stoichiometric compound is confirmed.

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Riassunto Le soglie di assorbimentoL dell'antimonio e dello iodio sono state misurate ad alta risoluzione con luce di sincrotrone in SbSI, Sb₂S₃ e Sb₂S₅. La densità degli stati liberi nella banda di conduzione è risultata adeguata per interpretare le strutture di soglia tra 0 e 10 eV. Il confronto delle strutture di soglia e degli spostamenti chimici dei tre composti ha rivelato una notevole somiglianza nella carica dell'atomo di antimonio e nella struttura della parte bassa della banda di conduzione. Le strutture tra 10 e 50 eV sopra la soglia sono state analizzate ed interpretate in relazione alla coordinazione stereochimica. è stata confermata la non esistenza del Sb₂S₅ come composto stechiometrico.

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Резюме Были определны рентгеновскиеL края поглощения суьмы и йода в SbSI, Sb₂S₃, Sb₂S₅ с высоким разрешением, используя синхротронное излучение. Показывается, что плотность незаполненных уровней в зоне проводимости адекватно описывает структуры в области от 0 до 10 эВ. Для трех соединений проводится сравнение полученных структур и химических сдвигов. Обнаружено удивительное подобие электрического заряда сурьмы и электронной структуры на дне зоны проводимости. Анализируются структуры в области от 50 эВ и предлагается их интерпрпретация. Отмечается отсутствие Sb₂S₅, как стехиометрического соединения.

     

Electrophysical properties of heat-treated gallium arsenide

The electrical conductivity, Hall effect, ionization energy, and defect concentration of GaAs samples subjected to various forms of heat treatment were studied. The original material comprised single crystals grown by the Bridgman and Czochralski methods with electron concentrations of 2·10¹⁵–7·10¹⁷ cm^–3. The ionization energy and defect concentration were calculated with an electronic computer. The thermal conversion of GaAs was attributed to traces of copper, lattice defects, and residual impurities. The mobility varied in a complicated manner with the temperature of heat treatment in GaAs samples retaining their original n-type conductivity.Translated from Izvestiya VU Z, Fizika, No. 3, pp. 69–76, March, 1973.     

Structure and electronic properties of antimony films on the Mo(110) surface

The structure and electronic properties of antimony on the Mo(110) surface are investigated over a wide range of coverages. In the submonolayer range, p(2×1), p(1×1), (1×3), and (1×2) adsorbate structures matched to the substrate are formed at room temperature. For coverages larger than a monolayer, three-dimensional antimony crystals whose orientation is determined by the substrate grow on the surface. Annealing of the system at temperatures higher than 1000 K leads to the formation of structures that are not observed upon condensation. The results of analyzing the electron energy-loss spectra jointly with the work function of the surface suggest the formation of surface molybdenum-antimony alloys.