Heat Treatment Effects on Electrochemically Grown Bi2Te3 Thin Films for Thermoelectric Applications

Bi2Te3 thin films were grown on a large area of n-Si/Ti/Au substrate by an electrochemical process. The synthesized film sample was cut into four different pieces and each piece underwent different heat treatments for 1 h to optimize their carrier concentration. Heat treatment experiments were performed in an inert atmosphere to prevent oxidation of the films during the treatment. X-ray diffraction showed an increase in the crystallite size with increasing annealing temperatures, which affected the thermoelectric performances of the films. At room temperature, the Seebeck coefficient and electrical resistivity were measured using a custom-built setup. Initially, the measured conductivity appeared to be n-type for all films backed by the metal buffer layer and Si substrate. A simple model that could classify the substrate contribution on the overall transport properties was then developed. The model confirmed that the actual conductivities of the films were p-type, and this was supported by their elemental analysis. [doi:10.2320/matertrans.ME201106]