Investigations on the electrodeposition behaviors of Bi0.5Sb1.5Te3 thin film from nitric acid baths

The electrochemical reduction process of Bi3+, HTeO2+, SbIII and their mixtures in nitric acid medium was investigated by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The reduction products electrodeposited at various potentials were examined using X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The results show that cathodic process in the nitric acid solution containing Bi3+, HTeO2+ and SbIII involves the following reduction reactions in different polarizing potential ranges: In low polarizing potential ranges, Te0 is formed firstly on the electrode surface through the electrochemical reduction of HTeO2+; with the negative shift of the cathodic polarizing potential, the reduction reaction of Bi3+ with Te0 to form Bi2Te3 takes place; when the cathodic polarizing potential is negative enough, Bi3+ and SbIII react with Te0 to form Bi0.5Sb1.5Te3. The results indicate that Bi0.5Sb1.5Te3 films can be fabricated by controlling the electrodepositing potential in a proper high potential ranges.