Structural and optical properties of Ge-As-Te thin films

Abstract

Chalcogenide glasses with Ge 10 As x Te 90− x ( x = 20, 25, 30, 35, 40, 45 and 55 at.%) were prepared by melt quenching technique. The glass transition temperature, the crystallization temperature, the melting temperature and the glass-forming tendency were determined from the differential scanning calorimetry measurements. The structural and optical properties of Ge 10 As x Te 90− x thin films prepared by electron beam evaporation were studied. X-ray diffraction showed that the as-evaporated films are amorphous and crystallize after annealing depending on the As content. The transmittance and reflectance of the films are found to be thickness dependent. The optical-absorption data indicate that the absorption mechanism is direct transition. The optical band gap values are increased with increasing As content while they decrease with increasing the film thickness. Upon annealing the transmittance and the optical band gap decrease whereas the reflectance and the refractive index increase.