Effect of annealing on the structure and optical properties of lead selenide and cadmium selenide thin film prepared by chemical bath deposition

Abstract

The effect of annealing on the structural and optical properties of lead selenide and cadmium selenide thin films prepared by chemical bath deposition has been studied. The films were annealed in air for a duration of 1 hour at temperatures of 673 K for CdSe and 573 K for PbSe. Both the as-deposited and annealed films were characterized by X-ray diffraction and optical absorption spectroscopy. The as–deposited CdSe films had the cubic structure with preferred orientation along (111) plane. However, after annealing there was a phase change from the cubic structure to the hexagonal structure with preferred orientation along the (002) plane. Both the as-deposited and annealed PbSe had the cubic structure with preferred orientation along the (200) plane. Other structural parameters such as the average crystallite size increased, whilst the dislocation density and strain decreased, suggesting a reduction in lattice imperfections after annealing. Optical absorbance of the films increased after annealing with a corresponding decrease in the direct band gap from 1.78 eV to 1.52 eV for CdSe, and 1.47 eV to 1.35 eV for PbSe. These results suggest an improvement in optical and structural properties after annealing.