STRUCTURAL VARIATIONS IN ANTIMONY SELENIDE

DTA graphs, X-ray diffraction patterns and electron micrographs showed that bulk Sb2Se3 obtained by furnace cooling or quenching the melt from 1 123 K to room temperature has a crystalline nature of orthorhombic structure while the prepared thin films with any thickness showed amorphous structure. The sharp endothermic peak at 603 K showing phase transition extended as a plateau to about 623 K with the quenched material depending on the degree of crystallinity. Crystallization of thin films was attained by annealing at 423 K in air and at 448 K under vacuum. This amorphous into crystalline transformation showed itself as an additional exothermic peak at 453 K in the D TA graph. Increasing the temperature and time of annealing and also the film thickness enhanced crystallization which was found to start with the preferred orientation on the planes (020), (120) and (130). The observed structural changes were explained in view of the variations of atomic orientation energy and internal stresses, the nature of boundary angles, the chain and layer structure of Sb2Se, and the role played by surface defects during crystallization.