Novel approach for synthesizing of nanometer-sized Si crystals in SiO 2 by ion implantation and their optical characterization

Abstract

Nanocrystals of Si have been fabricated inside SiO 2 by ion implantation and subsequent vacuum thermal annealing. The microstructure and optical properties of Si implanted layers have been studied by transmission electron microscopy and photoluminescence spectroscopy. The formation of Si nanocrystals after annealing at 1100°C and the growth in average size of nanocrystals with increasing annealing time have been confirmed. Strong visible photoluminescence around 1.7 eV has been achieved in specimens with Si nanocrystals in SiO 2. The shape of the emission spectrum of the photoluminescence is found to be independent of both excitation energy and annealing time. However, the luminescence intensity grows and then decreases as the annealing time increases. Based on these results, we conclude that the photons are absorbed by Si nanocrystals, for which the bandgap energy is modified by the quantum confinement effects, and the emission of photons is not due to direct electron-hole recombination inside Si nanocrystals but is related to defects probably at the interface between Si nanocrystals and SiO 2. The method for the formation of Si nanocrystals inside SiO 2 is fully compatible with silicon microelectronic technology.