PHOTOLUMINESCENCE FROM NANOPARTICLES OF SILICON EMBEDDED IN AN AMORPHOUS-SILICON DIOXIDE MATRIX

We have investigated visible photoluminescence related to nanometre-sized Si crystals in thermal oxide films grown on a crystalline Si wafer, created by Si+-implantation and subsequent annealing in a vacuum at 1100-degrees-C (the temperature at which SiO(x) decomposes into Si and SiO2). Evidence for the formation of Si nanocrystals by annealing at 1100-C is presented by transmission electron microscopy. The shape of the emission spectrum of the photoluminescence is found to be independent of both excitation energy and annealing time. while the excitation spectrum of the photoluminescence increases as the photon energy increases and its shape depends on annealing time. The results indicate that the photons are absorbed by nanometre-sized Si crystals, for which the band gap is modified by the quantum confinement, and that 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 SiO2.