Electrochemical Deposition and Characterization of Thermoelectric Ternary (Bi_(x)Sb_(1-x))_(2)Te_(3) and Bi_(2)(Te_(1-y)Se_(y))_(3) Thin Films

摘要

Thermoelectric thin films of the ternary compounds (Bi_(x)Sb_(1-x))_(2)Te_(3) and Bi_(2)(Te_(1-y)Se_(y))_(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 (Bi_(x)Sb_(1-x))_(2)Te_(3) and Bi_(2)(Te_(1-y)Se_(y))_(3) films, i.e., Seebeck coefficient and electrical resistivity, were measured after transferring the films to a nonconductive epoxy support. (Bi_(x)Sb_(1-x))_(2)Te_(3) 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 Bi_(0.5)Sb_(1.5)Te_(3). In addition, Bi_(2)(Te_(1-y)Se_(y))_(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 Bi_(2)Te_(2.7)Se_(0.3). In contrast to Bi_(2)Te_(2.7)Se_(0.3) thin films, an annealing treatment was required for Bi_(0.5)Sb_(1.5)Te_(3) thin films to achieve the same magnitude of power factor as Bi_(2)Te_(2.7)Se_(0.3). Therefore, Bi_(2)Te_(2.7)Se_(0.3) thin films appear to be good candidates for multilayer preparation using electrochemical deposition, but the morphology of the films must be further improved.