الفهرس 
Introduction and Literature ReviewOnly 14 pages are availabe for public view
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Abstract
The bulk lead sulfide and lead telluride are narrow gap semiconductors that can be used in fabricating infrared detectors and thermoelectric devices. In the recent years nanomaterials of those compounds were prepared in order to tune their energy gaps to widen their applications as different electronic devices. Therefore lead sulfide and lead telluride nanomaterials were prepared by a simple chemical method called hydrothermal method. Their structural properties were studied by using X-ray diffraction and their crystallite size lattice parameter, dislocation density and the strain were determined for PbS and PbTe nanomaterials. The atomic percentages were measured for both materials and their stoichiometric composition was confirmed.
Compressed pellets were made from both nanomaterials to study their electrical properties using alternating current, PbS and PbTe nanomaterials with various morphologies were synthesized by a hydrothermal method. The structural properties were investigated by using X-ray diffraction (XRD) and corresponding scanning electron microscopy together with their EDX analysis. Both the PbS and PbTe nanomaterials possess good polycrystalline structure. The crystallite size, determined from the XRD data, of PbS is 5 nm whereas the corresponding value of PbTe is 2.69 nm. SEM micrographs reveal that the prepared PbS nanomaterial has star-shaped structures, micro-flowers, some cubes, and semi-dendrites, whereas PbTe has semi-flower structures. Additionally, the dielectric properties have been studied in a broad frequency range from 0.1 Hz up to 1 MHz at temperatures from 298–423 K. The real and imaginary parts of the complex dielectric constant ε′ and ε″ of PbTe are comparatively higher than those of PbS. Moreover, the dielectric data were analyzed on the basis of the electric modulus.
PbS and PbTe films of different thicknesses were prepared by thermal evaporation technique. The PbS film thicknesses were 26, 34, 79 and 93 nm, while those of PbTe are 21, 50 and 66 nm. The structural properties of those films were studied by grazing incident X-ray diffraction, electron diffraction, energy dispersive X-ray spectral analysis. PbS and PbTe films showed NaCl face - centered cubic structure. The transmission electron micrographs showed nanoparticles, whose size increases with film thickness increase. High resolution electron micrographs showed separate nanocrystal inside which lattice fringes were observed. selected area electron diffraction patterns were obtained and used to determine the interplanar spacings of both PbS and PbTe nanocystalline films.
from the spectral distribution of transmittance and reflectance of both PbS and PbTe films of different thicknesses the optical parameters spectra of the absorption coefficients, the refractive index and the real part of the dielectric constant were illustrated. The optical energy gaps and their variation with film thickness the optical dielectric constant and the ratio of the charge carriers concentration to the electron effective mass were determined as a function of film thickness and wavelength.
The electrical resistivity, the charge carriers concentration and the charge carriers mobility were investigated as a function of temperature and film thickness for PbTe nanocrystalline films. Besides the variation of the same parameters with temperature were studied for PbS films of thickness 93 nm. The variation of the room temperature electrical resistivity of PbS films with film thickness was measured.
p-PbS /n-Si and p-PbTe/n-Si heterojunction were prepared. Their current –voltage characteristics were studied.at different temperatures. The variation of the ideality factor, the barrier height and the series resistance with temperature were studied. It was found that the ideality factor and the series resistance for both p- PbS/n-Si and p-PbTe/n-Si heterojunctions decrease with temperature increase, while the barrier height increases with heating.