Excess Si concentration dependence of the photoluminescence of Si nanoclusters in SiO2 fabricated by ion implantation

A method for the fabrication of luminescent Si nanoclusters in an amorphous SiO2 matrix by ion implantation and annealing, and the detailed mechanisms for the photoluminescence are reported. We have measured the implanted ion dose, annealing time and excitation energy dependence of the photoluminesc ence from implanted layers. The samples were fabricated by Si ion implantat ion into SiO2 and subsequent high-temperature annealing. After annealing, a photoluminescence band below 1.7 eV has been observed. The peak energy of the photoluminescence is found to be independent of annealing time and exci tation energy, while the intensity of the luminescence increases as the ann ealing time and excitation energy increase. Moreover, we found that the pea k energy of the luminescence is strongly affected by the dose of implanted Si ions especially in the high dose range. These results indicate that the photons are absorbed by Si nanoclusters, for which the band-gap energy is m odified by the quantum confinement effects, and the emission is not simply due to direct electron-hole recombination inside Si nanoclusters, but is re lated to defects probably at the interface between Si nanoclusters and SiO2 , for which the energy state is affected by Si cluster-cluster interactions . It seems that Si nanoclusters react via a thin oxide interface and the lo cal concentrations of Si nanoclusters play an important role in the peak en ergy of the photoluminescence. (C) 1999 Published by Elsevier Science B.V. All rights reserved.