Comparison of Structural, Electrical and Thermoelectric Properties of Vacuum Evaporated SnTe Films of Varied Thickness

Abstract

As a key type of promising thermoelectric (TE) material p-type Tin Telluride (SnTe) vacuum evaporated thin films synthesized at room temperature (RT) on a glass substrate, report a significant enhancement in the figure of merit (ZT) value. The thicknesses of the nanostructured thin films were kept about 145 nm and 275 nm. High-resolution X-ray diffraction (HRXRD) outlines the polycrystalline nature in both thin films. Surface morphology of these films is composed of grains of variable sizes as elucidated by scanning electron microscopy (SEM). This observation is further confirmed by atomic force microscopy (AFM) wherein the average roughness, surface skewness, and surface kurtosis parameters are used to analyze the surface morphology. Local microstructural features and crystalline structure have been confirmed from High-resolution transmission electron microscope (HRTEM) and the selected area electron diffraction (SAED) pattern, respectively. Four probes method was used to determine electrical measurements which confirm that the thin films have semi-metallic nature. Thermoelectric measurements carried out on these films resulted that the figure of merit increases as the thickness of the film increases. The maximum ZT value of ˜1.02 is obtained at room temperature for the thin film of thickness 275 nm.