Thermal annealing dependence of the structural, optical and electrical properties of selenium–tellerium films

Glassy substrates Se85Te15 thin films were thermally evaporated onto chemically cleaned glass. Optical absorption measurements were carried out on as-deposited and thermal annealed Se85Te15 films. It was found that the mechanism of the optical absorption follows the rule of non-direct transition. The annealed Se85Te15 films showed a decrease in the optical energy gap with increasing temperature of annealing higher than the glass transition temperature (343 K). The microstructure of the as-deposited and annealed Se85Te15 films was investigated. The crystalline phases, resulting from differential thermal analysis, have been confirmed using X-ray diffraction and transmission electron microscopy. The effect of annealing on the activation energy for conduction was also studied. The results are discussed on the basis of amorphous–crystalline transformations.