Dependence of thermal stability in the composition of Ge-As-Te films

Ge5AsxTe95-x amorphous thin films (x=20∼60) have been deposited by thermal evaporation and the change of their optical parameters—like refractive index and optical bandgap as a function of thermal annealing time—have been studied with an aim to screen the composition of the film with stable optical and thermal properties for applications in optical waveguide devices. The film with a composition around x=38.0 was found to be stable, while the optical band gap and refractive index decreases in the films with x 38.0. Further structural characterization showed no any observable changes of the Raman spectra in the as-prepared and annealed Ge5.2As38.0Te56.8 film, confirming the stability of the optical and thermal properties in this composition.