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

Abstract

We investigated the relationships among the deposition potential, the electric properties, and the thermoelectric properties of Bi2Te3 films electrodeposited from a solution containing 1.00mM TeO2 and 0.86mM Bi-EDTA complex. From the results of the Hall-effect measurements, the films formed at >−0.27V vs Ag∕AgCl were Te-rich n-Bi2Te3, and the carrier concentration increased with more negative deposition potential. The films formed at <−0.35V 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±10μVK−1) was observed for the film deposited at −0.20V. 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.