Brewster-angle analysis of native and photoelectrochemically grown silicon oxide nanotopographies

Brewster-angle reflectometry (BAR) is employed in-situ for the first time for investigation of the silicon oxide/silicon system during photocurrent oscillations in fluorine containing solution. Combining ex-situ Brewster-angle analysis (BAA) and atomic force microscopy (AFM) shows oxide thickness variations between 4.8 and 13.8 nm. The anodic oxide etch rate amounts to 0.1 nm s−1 in contrast to 0.01 nm s−1 for native oxide. The ambient/anodic oxide interface roughness, σ, is 2 ± 0.2 nm while σ for the oxide/silicon interface varies between 1.0 and 1.9 nm. The photocurrent onset, preceding regular current oscillations, is accompanied by roughness changes at the silicon oxide/silicon interface. A quantitative analysis of the overall system by discerning roughness and surface layer contributions is presented.