Effect of Annealing on the Structural and Optical Properties of Amorphous Ge8Se60Te30Sb2 Thin Films

Abstract

Thin film of Ge8Se60Te30Sb2 was synthesized by conventional melt quench technique. The structural properties of the pre annealed and post annealed films were studied by XRD characterization. Once the Ge8Se60Te30Sb2 film is annealed in the temperature range of 373–413 K for 2 h, it is observed that there is a continuous change in structure and formation of some polycrystalline structures in the amorphous phases. The optical transmission of these films was studied in the range 300–1000 nm as a function of photon wavelength. The band gap value suggests that sample is a semiconductor. The optical band gap Eg was observed to decrease in the range 373–413 K with increasing annealing temperature. The absorption coefficient (α) and extinction coefficient (k) were also evaluated. Annealing induced effect on the optical parameters was described on the basis of defect states and density of localized states arises from amorphous to crystalline phase transformation.