Anomalous light-induced enhancement of photoluminescence from Si nanocrystals fabricated by thermal oxidation of amorphous Si

A band of similar to 1.6 nm diameter Si nanocrystals (NCs) has been prepared at a depth of about 5 nm within SiO2 by atomic-layer deposition of 2 nm amorphous Si on 5 nm SiO2 and subsequent thermal oxidation at 900 degrees C. After 4 h light exposure of 5.66 W/cm(2), photoluminescence (PL) spectrum of the Si NCs is almost 60 times enhanced with its peak blueshifted by about 30 nm. The enhancement rate of the PL intensity with illumination time increases as the oxidation time increases. The PL intensity and its peak wavelength are partially recovered by annealing the samples at 440 K for 1 h, suggesting the effect is metastable. It is proposed that the anomalous light-induced effect is originated from the defect states at the Si NCs/SiO2 interfaces. (C) 2007 American Institute of Physics.