Preparation and characterization of p-type Sb2Te3 and n-type Bi2Te3 thin films grown by coevaporation

p-type antimony telluride thin films and n-type bismuth telluride thin films have been deposited by coevaporation on glass substrates. The conditions for deposition have been investigated as a function of substrate temperature (T-s), flux ratio (F-r = F(Te)/F(Sb, Bi)) and optimized to achieve a high thermoelectric power factor. The quality of deposited films, e.g. structure, composition and morphology, has been examined by x-ray diffraction, energy dispersive x-ray analysis, flame atomic absorption spectroscopy, and with an atomic force microscope. The thermoelectric properties of the thin films have been evaluated by room temperature measurement of the Seebeck coefficient, Hall coefficient, and electrical resistivity. Both the crystallinity and the transport properties are strongly affected by nonstoichiometry with the highly stoichiometric samples exhibiting a high crystallinity and high thermoelectric power factor. The Seebeck coefficient and electrical conductivity of p-type Sb2Te3 thin film (alpha (p), sigma (p)) and, n-type Bi2Te3 thin films ( alpha (n), sigma (n)) were found to be about 185 muV/K, 0.32 X 10(3) Omega (-1) cm(-1) and -228 muV/K, 0.77 X 10(3) Omega (-1) cm(-1), respectively. The results indicate that good quality antimony telluride and bismuth telluride thin films grown by coevaporation are promising candidate materials for use in the fabrication of micro-Peltier modules. (C) 2001 American Vacuum Society.