Electrochemical impedance spectroscopic study of electrodeposited Bi₂Te₃-based thin films

The Bi₂Te₃-based thin films have been prepared by electrochemical deposition on stainless-steel substrates. The microstructure and composition of the films were studied by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) . The deposition mechanisms of Bi₂Te₃ thin films on stainless-steel substrates were preliminary investigated using electrochemical impedance spectroscopy (EIS). The results showed that the similar deposition mechanisms were obtained for Bi-Te binary and Bi-Te-Se ternary systems, i. e., the Bi³⁺, HTeO₂⁺ and H₂SeO₃ were electrochemically reduced to form simple substances Bi(0), Te(0) and Se(0), respectively, then the Bi₂Te₃-based compounds were formed by reacting Te(0) or Se(0) with Bi(0). For Bi-Sb-Te ternary system, the HTeO₂⁺ was first electrochemically reduced to form simple substance Te(0), and then the Bi₂Te₃-based compounds were formed by reacting Te(0) with B³⁺ and Sb (III). The deposition processes were controlled by electrochemical polarization.