Showing papers on "Lead telluride published in 1989"

Electrical conductivity of air-exposed and unexposed lead telluride thin films-temperature and size effects

Abstract: Thin films of PbTe of different thicknesses have been prepared on glass substrates at room temperature by vacuum deposition. It is found that the electrical resistivity of the air-exposed films is much higher (by about 2 to 3 orders of magnitude) than that of the as-grown (unexposed) thin films. The electrical resistivity temperature behaviours of both the air-exposed and as-grown (unexposed) thin films of PbTe are different but both show hysteresis behaviour during successive heating-cooling cycles. These observations can be explained by considering that the desorption of absorbed gas molecules (mainly oxygen) and creation of defects at higher temperatures during heating influence the electrical conduction. Further, the time factor involved in gas desorption-adsorption can cause the observed hysteresis in temperature-dependent conduction behaviour. The as-grown (unexposed) thin-film conductivity exhibits the expected reciprocal thickness dependence due to the thickness effect, but the air-exposed film conductivity does not. This can be explained to be due to the complete masking of the thickness effect by the gas adsorption effect in air-exposed film conductivity. The reciprocal thickness dependence observed in the case of unexposed film conductivity has been explained by the 'effective mean free path' model. The low value of the 'grain boundary' mean free path obtained by the analysis points to the fact that in polycrystalline films, grain boundary scattering is extensive and controls the film conductivity.

Bismuth‐ and thallium‐doped lead telluride grown by molecular‐beam epitaxy

Abstract: Lead telluride and its high‐energy gap alloys are useful for long wavelength diode lasers. In the present study, the control of a donor (Bi) and of an acceptor (Tl) impurity in PbTe was studied in PbTe grown by molecular‐beam epitaxy. Several analytical techniques were used, including scanning Auger electron spectroscopy, secondary ion mass spectroscopy, conventional carrier transport measurements, and surface probe thermoelectric measurements. It was observed that bismuth incorporates well and undergoes negligible diffusion over the range of growth conditions used. Thallium surface segregates at high concentrations and diffuses appreciably at high growth temperatures and at high concentrations. Thus, it is only suitable for use in highly dimensionally defined structures at moderate to low concentrations and at relatively low growth temperatures.

Optical And Semiconductor Properties Of Lead Telluride Coatings

Abstract: The optical and semiconductor properties of lead telluride coatings are dependent on various factors contributing to its performance. In this paper, we will present the temperature dependent effects of single layer lead telluride coatings on the dispersion and absorption characteristics, absorption edge, and carrier concentration from 15 K to 436 K using both experimental and theoretical analysis.

States of paramagnetic impurities and laser-induced decomposition of impurity clusters in lead telluride

Abstract: Electrical and optical properties as well as the EPR of PbTe:Eu single crystals before and after an IR laser emission treatment in the matrix transparency region have been studied. Parameters of the spin Hamiltonian for Eu2+ ions in PbTe have been determined. It has been established that the IR laser treatment has a considerable effect on PbTe:Eu characteristics, allowing properties of the crystals to be changed over a wide range. Thus, a change over in the conductivity type of the crystals from the p type (P77K=4*1018 cm-3) to the n type (up to N77K=1*1019 cm-3) was attainable. The application of the IR laser emission made it possible to reveal a HFS in EPR spectra of Eu2+ ions and to separate the lines corresponding to Eu isotopes 151Eu and 153Eu. The changes in the electrical characteristics and EPR spectra of the crystals investigated are attributed to decomposition under the action of the IR radiation of Eu-enriched complexes.

Thermoelectric Power of Bismuth Doped Lead Telluride

Abstract: Etude du pouvoir thermoelectrique du systeme Pb 1-x Bi x Te en fonction de la temperature et de la compostion x, avec O≤x≤0.01. Les compositions x>0,003 sont fortement degenerees, et on y confirme la probable formation de complexes electriquement neutres