Study of the Silicon Electrochemical Nucleation in LiCl-KCl-CsCl-K2SiF6 Melt

Abstract

In this work, we studied the kinetics of the cathodic process and the regularities of the initial stages of silicon electrodeposition with methods of cyclic voltammetry, square-wave voltammetry, and chronoamperometry on a glassy carbon substrate from a LiCl-KCl-CsCl melt with K2SiF6 at a temperature of 545 ± 5°C. It is shown that the cathodic process of silicon reduction proceeds in one stage, and it is not electrochemically reversible. The diffusion coefficient of silicon ions found by CV and chronoamperometry was 8.44·10−11 and 1.00·10−10 m2 s−1, respectively. It was also found that the nucleation of silicon on glassy carbon is progressive; the formation of new nuclei proceeds continuously against the background of the growth of existing ones. Based on electrochemical measurements, various modes of silicon electrodeposition in the form of thin films were chosen: potentiostatic, pulse, reverse and galvanostatic with preliminary anodizing. As a result of electrolysis, silicon films were obtained, which were analyzed by SEM and XRD methods. The thickness of such deposits during electrolysis reaches several microns, and it consists of many spherical nuclei up to 0.7 microns in diameter. The content of impurities in deposits is extremely low, and the main contaminant is oxygen (0.4–1.2 wt%).