The surface morphology changes of silicon oxide on p-Si(111) during anodic current oscillations were investigated by in situ atomic force microscopy. Photoelectrochemically induced oxide coverage variations on n-Si(111) were observed in a separate in situ fast Fourier transform infrared spectroscopy experiment. A strong correlation between the photocurrents, the surface roughness and the silicon oxide coverage is obtained. The observed roughness changes are tentatively explained in terms of both oxide formation and local pH variations.