In Situ Fourier Transform Infrared Investigation on the Electrolytic Hydrogenation of n‐Silicon (111)

Abstract

The surface condition of Si(111) exposed to acidic fluoride solutions at fixed anodic potential (+1.1 V vs. flatband) is investigated by in situ Fourier transform infrared spectroscopy (FTIRS) in the multiple internal reflection (MIR) configuration. It is shown that a transient dark current, , can be used to monitor the degree of hydrogenation of the surface. Hydrogenation sets in shortly after the maximum of and is completed when reaches a low stationary value. The pH dependence of the hydrogenation shows larger contributions from at low pH indicating microscopic roughness at steps and smoothing after a two‐step procedure (electrochemical etching at pH 4.0 or 4.5 followed by the same procedure at pH 4.9). At pH values larger than 5.3 (up to 9), no surface hydrogen could be detected and is considerably increased.