Defect versus nanocrystal luminescence emitted from room temperature and hot-implanted SiO2 layers

Silicon nanocrystals have been synthesized in SiO2 matrix using Si ion implantation. Si ions were implanted into 300-nm-thick SiO2 films grown on crystalline Si at energies of 30-55 keV, and with doses of 5 x 10(15), 3 x 10(16), and 1 x 10(17) cm(-2). Implanted samples were subsequently annealed in an N-2 ambient at 500-1100 degrees C during various periods. Photoluminescence 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 and time in intensity, and that weak orange luminescence (600 nm) is observed after annealing at low temperatures of 500 degrees C 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 low dose of 5 x 10(15) cm(-2). It vanishes after annealing at 800 degrees C for 30 min. We conclude that this luminescence observed around 600 nm is caused by some radiative defects formed in Si-implanted SiO2. (C) 1999 Elsevier Science B.V. All rights reserved.