Thin films of GeTe, Ge2Sb2Te5 and Sb2Te3 have been synthesized from their respective polycrystalline bulk by thermal evaporation. X‐ray diffraction study of the films confirms the amorphous nature of GeTe and Ge2Sb2Te5 films, but as‐deposited Sb2Te3 film was in the crystalline form. Structural analysis has been performed for the annealed films above their crystallization temperature by XRD, which was evaluated by temperature‐dependent sheet resistance measurements. The Sb2Te3 film, which was already crystalline, undergoes a small transition at 110 °C. For optical studies, the transmittance and the reflectance spectra were measured over the wavelength ranges 400–2500 nm using UV‐VIS‐NIR spectroscopy. The optical bandgap, reflectance and optical contrast are also presented for thermally evaporated thin films. The dc electrical conductivity of the as‐deposited films has been measured as a function of temperature below the phase‐transition temperature, and increases exponentially with temperature. The value of the activation energy, calculated from the slope of lnσ versus 1000/T, is found to decrease from one end binary GeTe to pseudobinary Ge2Sb2Te5 and then to the other end binary Sb2Te3 films. On the basis of the pre‐exponential factor, the type of conduction in these films has also been discussed in the measured temperature range.
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