Electric and thermoelectric properties of electrodeposited bismuth telluride (Bi2Te3) films

We investigated the relationships among the deposition potential, the electric properties, and the thermoelectric properties of Bi2Te3 films electrodeposited from a solution containing 1.00 mM TeO2 and 0.86 mM Bi-EDTA complex. From the results of the Hall-effect measurements, the films formed at >-0.27 V vs Ag/AgCl were Te-rich n-Bi2Te3, and the carrier concentration increased with more negative deposition potential. The films formed at <-0.35 V were Bi-rich p-Bi2Te3, and the carrier concentration showed a constant value. A depth profile showed that all the electrodeposited films were composed of two layers, and that an n-type layer containing a large excess of Te existed near the substrate surface. From the Seebeck coefficient measurements, the electrical type of all the films was n type, and the maximum Seebeck coefficient (-70+/-10 muV K-1) was observed for the film deposited at -0.20 V. The electrical type obtained by the Seebeck coefficient measurements was completely different from the electrical type determined by the Hall-effect measurements. This difference could be explained by the p-n junction formation near the substrate surface. (C) 2004 American Institute of Physics.