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

Abstract

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 cm2 s−1, the nucleation rate constant A and the number density of active sites N0 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.