Nanotopography development on silicon electrodes by analysis of Brewster angle real time spectroscopy

The nanostructure formation of n type silicon photoelectrodes in fluoride containing solutions was investigated by in situ Brewster angle reflectometry BAR and atomic force microscopy AFM . The corrugation process near the first current maximum of the divalent tetravalent dissolution regime preserves the 111 surface lattice symmetry as proven by auto correlation analysis of corresponding AFM images the structure alignment is related to the terrace orientation of the original H terminated Si samples. The observed cathodic shift of the open circuit potential OCP for increased light intensities 240 mV for intensities between 1 and 40 mW cm2 allowed further shaping of the nanostructures it was possible to invoke alternately divalent and tetravalent paths of the silicon dissolution process at a constant potential. Oxidation in the tetravalent dissolution regime was observed to affect statistically rough areas faster than the nanostructures. As a result, an increase of the aspect ratio of 40 60 could be achieve