Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Effects of Temperature and Current Density

Abstract

© 2018 The Electrochemical Society. The effects of temperature and current density on the electrodeposition of Si films in molten KF–KCl–K2SiF6 were investigated at 923–1073 K. The peak current density of Si deposition in cyclic voltammetry increased as the temperature rose. The diffusion coefficient of Si (IV) ions measured by chronoamperometry increased through a rise in temperature. The activation energy for the diffusion of Si (IV) ions, 28.0 kJ mol-1, agreed with that for the viscosity of KF and KCl. The crystallinity of the Si films prepared by galvanostatic electrolysis on Ag substrates was measured based on electron backscatter diffraction. The largest crystallite size in the deposited Si increased with the deposition temperature, from a submicron size at 923 K, to several tens of microns at 1073 K. Moreover, even at the same temperature of 1073 K, larger crystallite sizes were observed for the Si deposit at 100 mA cm−2 as compared with that at 300 mA cm−2, which was explained based on the crystallization rate of Si.