Effect of pulse frequency on structural and thermoelectric properties of bismuth telluride thin films by electrodeposition

Effects of current pulse frequency and duty ratio [off-time/(on-time + off-time)] on thermoelectric properties of bismuth telluride (Bi2Te3) thin films were investigated. The crystal structure of the Bi2Te3 thin films was strongly affected by the duty ratio rather than the current pulse frequency. In particular, the Bi2Te3 thin films were highly oriented along (1 1 0) direction with smooth surface at the high current pulse frequency (5000 Hz) and the high duty ratio (80%). Overall, the electrical conductivities of the Bi2Te3 thin films with current pulse frequency of 5000 Hz were larger than that the thin films with 1000 Hz, whereas the Seebeck coefficients were mostly the same between the both frequencies. As a result, the highest power factor (1.1 mu W/(cm.K-2)) was observed at the Bi2Te3 thin films with a current pulse frequency of 5000 Hz and a duty ratio of 60%.