Influence of Pb doping on the structural, optical and electrical properties of nanocomposite Se-Te thin films

Nanocomposite thin films of Se0.80Te0.20−xPbx (x = 0.02, 0.06 and 0.10) were deposited on glass substrates at room temperature by thermal evaporation method. The prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), field emission transmission electron microscope (FETEM), optical and electrical transport measurements. The XRD patterns show the monoclinic crystal structure with average crystallite size ∼30 nm. These results were correlated with the result obtained from SEM and TEM. All films reflect almost sphere-like particles with tightly bonded together and exhibit nearly equal sizes. The TEM images showed the average particle size about 27 nm whereas the average particle size for 2% Pb content sample was about 24 nm. The temperature dependence of dc conductivity has been reported in the temperature range 201-401 K. In low temperature region, we interpreted our results in terms of the Mott's law and the analysis is very consistent with the variable range hopping conduction mechanism; while in the high temperature region, it is due to the thermally activated tunneling of charge carriers in the band tails of localized states. The compositional dependence of the derived optical properties was found and discussed.