CHARACTERIZATION OF SUPERCRITICALLY DRIED POROUS SILICON

Porous silicon (PS) has been formed by electrochemical etching of p-ty pe silicon. During drying in air the sponge-like structure of the poro us layers is exposed to capillary forces which will partially destroy the microstructure of highly PS. One possibility for avoiding the part ial structural collapse is by supercritically drying the PS. This tech nique is already known from the formation of highly porous aerogels an d has now been applied to PS. Porosities of 90% can be achieved. These highly porous layers were investigated using photoluminescence, Raman , reflectance and X-ray photoemission spectroscopy. The porosity was d etermined by gravimetric measurements. The effect of the drying proces s on the properties of PS was also studied.