Thermal annealing effect on the structural and the optical properties of Nano CdTe films

Structural and optical properties of as-prepared and annealed thermal evaporated CdTe films were investigated. The annealing temperature (373–523 K) affects both structural and optical parameters. Polycrystalline nature with preferred (1 1 1), (2 0 0) and (2 2 0) orientations was released, the corresponding two theta is 23.15°, 27.42° and 40.26° respectively. Structural parameters as dislocation density, inter-planer distance, the number of crystallites per unit surface area, lattice constant, crystallite size and strain could be determined as a function of annealing. The results confirm the films nanostructure property. The optical gap, refractive index, dielectric constant and optical conductivity increase as a function of annealing. These effects were attributed to the nano structural property and the partial reduction of the defect density.