ON THE ORIGIN OF BLUE LUMINESCENCE ARISING FROM ATMOSPHERIC IMPREGNATION OF OXIDIZED POROUS SILICON

When heavily oxidized porous silicon is stored in ambient air for prol onged periods, a broad blue photoluminescence band with nanosecond dec ay times gradually appears. Not only PL intensity, but peak position, half-width and temperature dependence evolve with material aging. Very similar photoluminescence is shown to be characteristic of many high surface area materials stored in air for months. We stress here that h ydrocarbon contamination can occur during air exposure, in addition to hydration by water vapour. Preliminary Fourier transform infrared spe ctroscopy and secondary ion mass spectrometry studies, together with p ublished data on blue-emitting porous alumina and organics, suggest th at the gradual build-up of low concentrations of carbonyl-related chro mophores could give rise to the emergence of blue-green luminescence i n aged oxidized porous Si structures.