Effect of composition on the properties of bismuth telluride thin films produced by galvanostatic electrodeposition

Abstract

Bismuth telluride thin films were prepared on nickel plate by galvanostatic electrodeposition from hydrochloric acid-based electrolyte. It was found that the structural and thermoelectric properties of the thin films were strongly dependent on the Te content in the electrolyte. All thin films with various Te contents exhibited peaks in their X-ray diffraction patterns corresponding to the reflections of the rhombohedral phase of Bi2Te3. The surface morphology of the thin films with nearly stoichiometric composition was formed by dendritic crystallites, and that of the Te-rich thin film revealed a granular structure. The electrical conductivity of these thin films seemed to be influenced by both the Te content and the morphology. The Seebeck coefficient of the thin films exhibited both negative and positive values in dependence of the quantity of Te in the electrolyte. This behavior is advantageous because only by changing the Te content of the electrolyte, the material composition can be manipulated to yield either p-type or n-type semiconductors suitable for thermoelectric devices.