Room temperature oxidation of Si nanocrystals at dry and wet air

Oxidation of HF vapor-etched nanocrystalline silicon films, prepared by drop coating from nanocrystalline Si sol in acetonitrile, was studied. Oxidation of nanocrystalline silicon at room temperature in air with 5% and 86% relative humidity was observed by means of infrared spectroscopy for 2 days. The change in film mass after 15 h of oxidation was determined using quartz crystal microbalance. In dry air, film mass and integral intensity of bands attributed to vibrations in Si_{3 − x}–Si–H_x and Si–O–Si groups changed linearly with time. In humid air, intensity of in Si_{3 − x}–Si–H_x band decays exponentially and intensity of Si–O–Si band increases as a square root of oxidation time. Film mass gain after 15 h of oxidation corresponds to an average oxide layer thickness of 0.02 nm in dry air and 0.51 nm in wet air.