Nucleation and growth mechanism of tellurium electrodeposited on tin-doped indium oxide substrate

摘要

The mechanism of electrochemical deposition of tellurium on tin-doped indium oxide (ITO) substrate from a nitric acid solution containing telluryl ion (HTeO2+) has been studied in this work. The investigation, using cyclic voltammetry and chronoamperometry, shows that the electrodeposition of Te at a negative potential around - 0.42 V versus saturated calomel electrode (SCE) is a quasi-reversible reaction controlled by the diffusion process. Furthermore, by chronoamperometry, the measured current transient curves were compared with the theoretical models, proposed by Scharifker-Hills and Heerman-Tarallo models. It was found that the nucleation and growth mechanism of Te on ITO substrate changed with increasing the concentration of HTeO2+, it can be instantaneous for 2.10(-2) mol L-1 or progressive for 2.10(-3) mol L-1. The quantitative analysis (nonlinear fitting) shows that the diffusion coefficient remains between 7.10(-6) and 9.10(-6) cm(2) s(-1), the nucleation rate constant A and the number density of active sites N-0 were growth with the increase of the concentration and the deposition potential. The thin tellurium layers, electrodeposited by chronoamperometry, are characterized by X-ray diffraction. It has been identified that all the films were polycrystalline type hexagonal crystal structure with preferred orientation of (1 0 0) and (1 1 0) planes to growth. The SEM analysis reveals that the morphology of the resulting deposits is depending on the type of electrodeposition mechanism. Graphic abstract