Some studies on chemically synthesized antimony-doped CdSe thin films

• Published in: Materials chemistry and physics 2003-01, Vol.77 (3), p.669-676
• Main Authors: Masumdar, E.U, Gaikwad, V.B, Pujari, V.B, More, P.D, Deshmukh, L.P
• Format: Article
• Language: English
• Subjects: Bandgap; Chemical deposition process; Cross-disciplinary physics: materials science; rheology; Electrical conductivity; Exact sciences and technology; Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids); Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Thermoemf
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/S0254-0584(02)00122-0

A solution growth process is employed for deposition of the pure and antimony-doped CdSe thin films with Sb 3+ 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 Sb 3+ content from 0 to 0.1 mol% and for further increase in Sb 3+ 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=10 4 cm −1) with an allowed direct type of transitions. The optical energy gap ( E g) decreased typically from 1.79 to 1.61 eV as the doping concentration (Sb 3+) 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 Sb 3+ 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 ( Φ B’s) were computed and it was found that the carrier concentration has a poor variation with Sb 3+ concentration and temperature, whereas the carrier mobility is a sensitive function of both.