The room temperature oxidation of porous silicon

The room temperature oxidation of porous silicon was studied using isothermal methods. The oxidation was found to depend on the type of the porous silicon. The microcalorimetric signals from the oxidation of the p⁺- and n-type porous silicon in dry air were different. In humid air the signals from the oxidation could not be distinguished from the strong signal due to adsorption of water vapour, but when the samples were placed in water similar differences were observed. The reason for differences in reactions is discussed. The oxidation in different liquids was also studied. The signal from reactions in methanol and ethanol were found to be 100 times higher than in water. In FTIR studies the reaction gas produced by reactions between alcohols and the porous silicon, silane (SiH₄) was found in the gas. Traces of SiOCH₃ and SiOC₂H₅ groups were also found in FTIR spectra indicating Si---O---C_xH_y passivation of the surface.