Optimization in fabricating bismuth telluride thin films by ion beam sputtering deposition

Abstract

N-type bismuth telluride (Bi2Te3) thermoelectric thin films were deposited on BK7 glass substrates by ion beam sputtering method. Various substrate temperatures were tried to obtain optimal thermoelectric performance. The influence of deposition temperature on microstructure, surface morphology and thermoelectric properties was investigated. X-ray diffraction shows that the films are rhombohedral with c-axis as the preferred crystal orientation when the deposition temperature is above 250°C. All the films with single Bi2Te3 phase are obtained by comparing X-ray diffraction and Raman spectroscopy. Scanning electron microscopy result reveals that the average grain size of the film is larger than 500nm when the deposition temperature is above 300°C. Thermoelectric properties including Seebeck coefficient and electrical conductivities were measured at room temperature, respectively. It is found that Seebeck coefficients increase from −28μVk−1 to −146μVk−1 and the electrical conductivities increase from 1.87×103Scm−1 to 3.94×103Scm−1 when the deposition temperature rose to 250°C and 300°C, respectively. An optimal power factor of 6.45×10−3Wm−1K−2 is gained when the deposition temperature is 300°C. The thermoelectric properties of bismuth telluride thin films have been found to be strongly enhanced by increasing the deposition temperature.