Study on the electrodeposition of Bi2Te3 thin film thermoelectric material in dimethyl sulfoxide

Abstract

In this paper, the electrochemical behaviors of Bi3+ and Te4+ ions in dimethyl sulfoxide (DMSO) organic solvent were studied by testing the cyclic voltammetry curves and cathodic polarization curves. The diffusion coefficients of Bi3+ and Te4+ ions were investigated and calculated, and reduction difficulty of them was compared. Then, bismuth telluride thermoelectric thin films were prepared using potentiostatic electrodeposition mode in the electrolytes with different compositions at different potentials. The structure, morphology and compositions of the prepared thermoelectric materials were characterized and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (EDS). The results show that the redox processes of Bi, Te and bismuth telluride on Au electrode are all completely irreversible processes. The diffusion coefficient of Bi3+ ion has an order of magnitude of approximately 10−7 while that of Te4+ ion is about 10−5. The reduction of Bi3+ ion is more difficult than that of Te4+ ion in dimethyl sulfoxide organic solvent. The prepared thin film thermoelectric materials are bismuth telluride alloy, and the electrolyte composition and deposition potential have great influence on the structure, morphology and composition of the films. Increasing the concentration of Bi3+ ions in the electrolyte can greatly increase the content of element Bi in the deposits. In the electrolyte containing 20 mol·L−1 Bi(NO3)3·5H2O and 10 mol L−1 TeCl4, the bismuth telluride film electrodeposited at − 1.2 V has uniform grain size and compact structure, shows good surface morphology, and the atomic fraction ratio of Bi/Te element in the film is 1:1.80.