Stability in photoluminescence of porous silicon

The effect of aging on photoluminescence (PL) of porous silicon has been studied for different storage media with a view to find suitable conditions for stabilizing the PL spectra. IR studies have been performed on both initially oxidized and oxide-free porous silicon samples to get an insight of the possible chemical changes in the porous layer after treating it in a number of environments. The changes in the PL spectra, both blue shift and red shift in appropriate environments, are ascribed to growth in Si=O bonds leading to trapped electron states at the Si/SiO2 interface in conformity with the recently proposed model [M.V. Wolkin et al., Phys. Rev. Lett. 82 (1999) 197]. In addition, a mechanism and a theoretical model for oxidation of silicon nanocrystallites in porous silicon have been proposed to explain the observed experimental results. An excellent agreement between the observed rate of shift of PL peak wavelength with storage time and that calculated from the proposed model has been found. Possibility of stabilizing the PL intensity and peak wavelength by keeping it in a non-oxidizing environment and to tune the PL peak wavelength with different storage media have also been discussed.