Investigation of structural, optical and thermoelectric properties of SnTe thin films of variable thickness

Tin Telluride (SnTe) thin films of thickness 33 nm, 145 nm and 275 nm have been deposited on glass substrate by thermal vapor deposition technique. XRD results revealed that thin films are polycrystalline and having NaCl cubic crystalline structure. It was observed that dominant diffraction peak corresponds to the plane (200) and average crystallite size of SnTe thin films was calculated around 13 – 15 nm. SEM micrographs show morphological feature of these thin films which represent the granular shape structure for individual thin film. Overall this indicates the presence of different size grains (50 – 450 nm) in these thin films. HRTEM micrograph indicates the presence of randomly oriented fine grains of polyhedral shape having crystallite size between 5 – 20 nm and also inter-planar spacing value is in close agreement with XRD results. FTIR spectrum revealed that transmittance peaks observed in the wave numbers range from 2500 – 2800 cm–1 belongs to symmetrical stretching vibrations of Sn-Te molecule. At room temperature Raman spectrum revealed the phonon mode vibration peaks of Sn-Te molecule in range from 121 – 125 cm–1. The result of the Figure-of-merit (ZT) obtained by Hermann method is measured around 1.02 for thin film of thickness 275 nm at 293 K. (author)