Insight into the Electrodeposition of SixGe1-x Thin Films with Variable Compositions from a Room Temperature Ionic Liquid

In this article, we investigated the electrodeposition of SixGe1-x from 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide containing different molar concentrations of SiCl4 and GeCl4. Upon the deposition of SixGe1-x using a 1:1 molar ratio of SiCl4 and GeCl4, a color change of the deposit from red to green was observed during the cyclic voltammetric scan. On increasing the concentration of SiCl4, only a reddish deposit could be seen during cyclic voltammetry. When the concentration of GeCl4 was increased, only a black deposit was obtained. Constant potential electrodeposition showed the formation of SixGe1-x with varying proportions of Si to Ge on changing the molar ratio in the solution. To further evaluate the reaction mechanism of the electrodeposition process, in situ UV visible spectroelectrochemistry was performed. From the changes in the UV spectra combined with XPS and SEM observations, a layered growth process has been proposed during the formation of SixGe1-x.