Chemical states and optical properties of thermally evaporated Ge-Te and Ge-Sb-Te amorphous thin films

► Thermally evaporated amorphous GeTe and Ge2Sb2Te5 thin films. ► Sample characterization with XRD, XPS, EPMA, UV-vis-NIR and temperature dependent sheet resistance. ► Role of Sb was to suppress the formation of wrong homopolar bonds in GST system. ► Band gap, sheet resistance and phase transition temperature decreases while reflectivity and refractive index increase for GST than GT films. ► GST film was more absorptive than GT film for whole studied wavelength range.