Electrochemical Deposition and Characterization of Thermoelectric Ternary (BixSb1−x)2Te3 and Bi2(Te1−ySey)3 Thin Films
Thermoelectric thin films of the ternary compounds (BixSb1−x)2Te3 and Bi2(Te1−ySey)3 were synthesized using potentiostatic electrochemical deposition on gold-coated silicon substrates from aqueous acidic solutions at room temperature. The surface morphology, elemental composition, and crystal structure of the deposited films were studied and correlated with preparation conditions. The thermoelectric properties of (BixSb1−x)2Te3 and Bi2(Te1−ySey)3 films, i.e., Seebeck coefficient and electrical resistivity, were measured after transferring the films to a nonconductive epoxy support. (BixSb1−x)2Te3 thin films showed p-type semiconductivity, and the highest power factor was obtained for film deposited at a relatively large negative potential with composition close to Bi0.5Sb1.5Te3. In addition, Bi2(Te1−ySey)3 thin films showed n-type semiconductivity, and the highest power factor was obtained for film deposited at a relatively small negative potential, having composition close to Bi2Te2.7Se0.3. In contrast to Bi2Te2.7Se0.3 thin films, an annealing treatment was required for Bi0.5Sb1.5Te3 thin films to achieve the same magnitude of power factor as Bi2Te2.7Se0.3. Therefore, Bi2Te2.7Se0.3 thin films appear to be good candidates for multilayer preparation using electrochemical deposition, but the morphology of the films must be further improved.