Fabrication of a p-type Sb/sub 2/Te/sub 3/ and n-type Bi/sub 2/Te/sub 3/ thin film thermocouple

Abstract

A thin film Sb/sub 2/Te/sub 3/-Bi/sub 2/Te/sub 3/ based thermocouple was fabricated. P-type antimony telluride thin films and n-type bismuth telluride thin films have been deposited by co-evaporation on to glass substrates. The conditions for deposition have been investigated as a function of substrate temperature (T/sub s/) and flux ratio (F/sub r/ = F(Te)/F(Sb,Bi)) and optimised to achieve a high thermoelectric power factor. The qualities of deposited films, e.g. structure, composition and morphology, have been examined by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDXA), flame atomic absorption spectroscopy (FAAS) and atomic force microscope (AFM). The thermoelectric properties of the thin films have been studied by room temperature measurement of the Seebeck coefficient, Hall coefficient and electrical resistivity. It has been observed that the Seebeck coefficient and electrical conductivity of p-type Sb/sub 2/Te/sub 3/ thin film (/spl alpha//sub p/, /spl sigma//sub p/) and n-type Bi/sub 2/Te/sub 3/ thin films (/spl alpha//sub n/, /spl sigma//sub n/) were found to be about 185 /spl mu/V/K, 0.32 /spl times/ 10/sup 3/ /spl Omega//sup -1/ cm/sup -1/ and -228 /spl mu/V/K, 0.77 /spl times/ 10/sup 3/ /spl Omega//sup -1/ cm/sup -1/, respectively. From optimal deposition parameters, a thin film thermocouple was fabricated and operated in Peltier mode. The observed maximum value for temperature difference between hot and cold end is about 15 K for a current of 50 mA. The results indicate that good quality antimony telluride and bismuth telluride thin films grown by co-evaporation are promising candidates for use in a micro-Peltier module.