Near-field investigation of porous silicon photoluminescence modification after oxidation in water

Abstract : We report on local photo‐induced oxidation of porous silicon in water at room temperature. Starting from a nonluminescent sample, the oxidation process induces luminescence which was found to first increase and then decrease as a function of the oxidation time. A clear blue shift is also observed. This effect is believed to be owing to size modification of silicon nanocrystallites and thus is explained in terms of quantum confinement. Optical near‐field images and spectrum are used to monitor the photoluminescence modifications after oxidation. As the photoluminescence can be widely tuned in wavelength and intensity, this method offers a way to pattern the emission properties of the sample.