Control of embedded Si nanocrystals in SiO2 by rapid thermal annealing and enhanced photo luminescence characterization

It is well known that Si implantation into SiO2, and subsequent high temperature annealing induce the formation of embedded luminescent Si nanocrystals. In this work, potentialities of rapid thermal annealing to enhance the photoluminescence have been investigated. Ion implantation was used to synthesize specimens of SiO2 containing supersaturated Si with different concentrations. The implanted samples were subsequently annealed at 1050 degrees C for several hours using a conventional tube furnace. Some of the samples were rapidly thermal annealed at 1050 degrees C or 1100 degrees C for only 5 min with different rising ratio from 10 to 50 degrees C/s. Photoluminescence spectra were measured at various stages of annealing processes. The luminescence intensity is strongly enhanced with a rapid thermal annealing before conventional furnace annealing. Moreover, the luminescence peak energy is found to be dependent, but a little, on thermal history of specimens. The luminescence intensity is known to be determined by the number of Si nanocrystals. In forming the Si nanocrystals in a SiO2 matrix by high temperature annealing, decomposition, diffusion, nucleation, growth and crystallization processes are clearly important. The experimental results indicate that the rapid thermal annealing is effective for the initial process in forming Si nanocrystals, especially for low dose specimens. Based on the results, we discuss about the mechanism of an enhancement of the photo luminescence from embedded Si nanocrystals with rapid thermal annealing. (C) 2007 Elsevier B.V. All rights reserved.