Growth of p- and n-type bismuth telluride thin films by co-evaporation

Both n- and p-type bismuth telluride thin films have been deposited by co-e vaporator on glass substrates. The conditions for deposition have been inve stigated as a function of substrate temperature (T-s) and flux ratio (F-r = F(Bi)/F(Te)) and optimised to achieve a high thermoelectric power factor. The quality of the deposited films, e.g. structure, composition and morphol ogy, has been examined by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDXA), and atomic force microscope (AFM). The thermoelectric prop erties of the thin films have been studied by room-temperature measurement of the Seebeck coefficient, Hall coefficient and electrical resistivity. Bo th the crystallinity and the transport properties have been found to be str ongly affected by nonstoichiometry with the highly stoichiometric samples e xhibiting a high crystallinity and high thermoelectric power factor. It has been observed that the Seebeck coefficient and electrical conductivity of n-type (alpha (n), sigma (n)) and p-type (alpha (p), sigma (p)) bismuth tel luride films were found to be about -228 muV/K, 0.77 x 10(3)Ohm (-1)cm(-1) and 81 muV/K, 3.1 x 10(3)Ohm (-1)cm(-1). respectively. The results indicate that the good quality bismuth telluride thin films grown by co-evaporator in both p- and n-type are promising candidates for use in micro-Peltier mod ules. (C) 2001 Elsevier Science B.V. All rights reserved.