Some studies on chemically synthesized antimony-doped CdSe thin films

A solution growth process is employed for deposition of the pure and antimony-doped CdSe thin films with Sb3+ doping concentration from 0.005 to 5 mol%. Cadmium sulphate, sodium selenosulphite (refluxed) and antimony trichloride were the basic starting materials. The samples were deposited at 60 °C in an aqueous alkaline medium and were analysed spectrophotometrically, before characterizing them through the structural, microscopic, optical, and transport characterization techniques. The terminal thickness was found to increase with the Sb3+ content from 0 to 0.1 mol% and for further increase in Sb3+ concentration up to 5 mol%, the thickness decreased. The as-deposited films were found to be polycrystalline with the hexagonal wurtzite structure. The optical absorption studies gave a high coefficient of absorption (α=104 cm−1) with an allowed direct type of transitions. The optical energy gap (Eg) decreased typically from 1.79 to 1.61 eV as the doping concentration (Sb3+) was increased from 0 to 0.1 mol% and then it increased at higher doping levels. Electrical conductivity measurements revealed two types of conduction mechanisms, namely grain boundary scattering limited and a variable range hopping conduction. These studies showed that electrical conductivity increased with antimony content in CdSe from 0 to 0.1 mol% and then decreased for higher values of the Sb3+ contents. The thermoelectric power measurements showed that the thermally generated voltage was of the order of several microvolts and samples exhibited n-type conduction. The carrier concentration (n), mobility (μ) and intergrain barrier potentials (ΦB’s) were computed and it was found that the carrier concentration has a poor variation with Sb3+ concentration and temperature, whereas the carrier mobility is a sensitive function of both.