Investigation of vacuum evaporated SnTe thin films for their structural, electrical and thermoelectric properties

Remarkable enhancement in figure-of-merit (ZT) value of p-type Tin Telluride (SnTe) thin films is reported in the present investigations. Under high vacuum conditions, all thin films deposited on the glass substrate by using thermal evaporation technique. Thickness of the thin films were kept 55 and 33 nm. Morphological features and the elemental composition of the thin film were investigated using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) technique respectively. High-resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED) pattern was used to investigate the microstructure of these thin films. For the identification of crystalline features, phase, and nano-crystallites size in all the thin films, the X-ray diffraction (XRD) technique had played a dominant role. The analysis of the XRD data results in a single-phase cubic structure. Atomic force microscopy (AFM) analysis revealed the 2D and 3D view of variable size grains formed on the glass substrate. Four probes method was used to determine the electrical conductivity of these thin films. Electrical measurements revealed the semi-metallic nature of the SnTe thin films. The thermoelectric measurement analysis revealed that the ZT of the thin films was found to be increased as the thickness of the film enhanced. The maximum value of ZT∼1.0 was obtained at room temperature for the film of thickness 55 nm. (author)