Investigations on chemical bath deposited cadmium selenide thin films

CdSe polycrystalline thin films were grown onto glass substrates by chemical bath deposition at 70 °C. The samples were characterised by structural, optical and electrical properties. XRD results revealed that the deposited CdSe thin films are polycrystalline in nature with cubic structure having (1 1 1) plane as the preferred orientation. The structural parameters such as the lattice constant, crystallite size, dislocation density, number of crystallites per unit area and strain were calculated for films and it was found that the estimated structural parameters are better compared with those of vacuum based hot wall deposited CdSe thin films. EDAX results indicated that the prepared CdSe thin films are non-stoichiometric in composition (Cd1.3Se0.7). The optical analysis helped to establish the type of transition as direct allowed. Various optical parameters such as absorption coefficient, extinction coefficient and band gap energy have also been evaluated. The thickness dependence of structural and optical parameters has been discussed in this paper in detail. The high temperature conductivity mechanism has been found to be due to the grain boundary scattering contribution and the evaluated high temperature electrical parameters strongly confirm the semiconducting nature of CdSe thin films.