Self-catalytic etching of silicon: from nanowires to regular mesopores

Metal assisted etching is a new promising technique for Sili- con nanowires fabrication, but also for generating a new class of porous semiconductors with precise and controlled mor- phology, unavailable by electrochemical etching. The process and the morphology seem to be independent on substrate dop- ing, but only on the crystallographic directions and metal pat- terning at the top surface. A preliminary investigation on some possible patterning techniques is reported, using porous silicon layers as pre-patterning tool, porous alumina and polystyrene nanospheres. The influence of the masking pro- cedure on the final array of nanostructures is discussed. Final morphology resulting from polystyrene nanosphere based patterning and metal assisted etching.