Microstructural and optical properties investigation of variable thickness of Tin Telluride thin films

A series of Tin Telluride (SnTe) thin films of varied thicknesses are deposited on glass substrates at room temperature using thermal evaporation technique. The optical and microstructural properties of SnTe thin films of thicknesses 33 nm to 275 nm are reported. High-resolution x-ray diffraction patterns of SnTe thin films revealed the polycrystalline nature with [200] orientation having cubic structure. The microstructural and morphological structures of these films were examined using high-resolution transmission electron microscopy and scanning electron microscopy, respectively. The distribution of isotopes of various elements in the thin film along with lateral and longitudinal directions was determined by depth profile measurement using the time of flight - secondary ion mass spectroscopy technique. Fourier transform infrared spectroscopy spectra reveal the molecular vibrations, narrow bandgap property of material and suitability of materials in infrared applications. Longitudinal - optical phonon scattering due to the [222] orientation was observed in the micro-Raman spectra at room temperature which corresponds to a peak in the range 120-130 Raman shift/cm(-1). Hence, the change in optical and microstructural properties at the nano-regime resulted in a shift towards the near-infrared region with an increase in the thickness of the thin films.