Pulsed Electroplating: a Derivate Form of Electrodeposition for Improvement of (Bi1-xSbx)2Te3 Thin Films

Bismuth antimony telluride (Bi1-x Sb (x) )(2)Te-3 thermoelectric compounds were synthesized by pulse plating. Due to the large number of parameters available (pulse waveform, on/off pulse time, applied current density), this advanced form of electrodeposition allows better control of the interfacial supply and electrochemical reactions and offers effective ways to improve macroscopic properties such as adhesion and to produce crack-free hard deposits and fine-grained films with higher uniformity and lower porosity. The influence of pulse parameters (pulse time t (on), cathodic current density J (c)) on the stoichiometry, roughness, and crystallography of deposits was studied. The thermoelectric properties (electrical resistivity and Seebeck coefficient) of the films were measured. The results revealed that deposits have p-type conductivity directly after electroplating (Seebeck coefficient around 150 mu V K-1), in contrast to films synthesized by direct current, which require annealing. An improvement of resistivity was observed: for a direct-current-deposited film the resistivity is around 5000 mu Omega m, whereas for a pulse-deposited film the resistivity was around 200 mu Omega m.