Defect vs. Nanocrystal Luminescence Emitted in Si-Implanted SiO2 Layers

Visible photoluminescence is observed from thin Si-implanted SiO2 films. Si ions were implanted into 300-nm-thick SiO2 films grown on crystalline Si at energies of 30 and 55 keV, and with doses of 5 x 10(15) and 1 x 10(17) cm(-2). Implanted samples were subsequently annealed in N-2 ambient at 500-1100 degrees C. PL spectra for the sample implanted with 1 x 10(17) cm(-2) at 55 keV show that red luminescence (750 nm) related to Si-nanocrystals clearly increases with annealing temperature in intensity, and that a weak orange luminescence (600 nm) is observed after annealing at low temperatures of 500 and 800 degrees C. The luminescence around 600 nm becomes very intense when a thin SiO2 sample is implanted at a substrate temperature of 400 degrees C with an energy of 30 keV and a dose of 5 x 10(15) cm(-2). After annealing the sample in forming gas the PL intensity remarkably decreases. It indicates that defects are passivated by hydrogen. We conclude that this luminescence observed around 600 nm is caused by some radiative defects formed in Si-implanted SiO2.