Lublow, M. ; Lewerenz, H.J.: Nanotopography development on silicon electrodes by analysis of Brewster angle real-time spectroscopy. ECS Transactions 6 (2008), p. 1-10
10.1149/1.2831725
Abstract:
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 achieved.