The role of nitrogen in the formation of luminescent silicon nanoprecipitates during heat treatment of SiO2 layers implanted with Si+ ions

Twenty-five kiloelectronvolt Si+ ions with doses of (1-4) x 10(16) cm(-2) a nd 13-keV N+ ions with doses of (0.2-2) x 10(16) cm(-2) were implanted into SiO2 layers, which were then annealed at 900-1100 degreesC to form lumines cent silicon nanoprecipitates. The effect of nitrogen on this process was d educed from the behavior of the photoluminescence spectra. It was found, fo r a certain ratio between the concentrations of implanted silicon and nitro gen, that the photoluminescence intensity increases significantly, and its peak shifts to shorter wavelengths. It is concluded that the number of prec ipitation nuclei increases owing to the interaction of nitrogen with excess silicon. Eventually, this results in an increase in the number of nanocrys tals and in a decrease in their average sizes. In spite of introducing addi tional precipitation nuclei, the minimal concentrations of excess Si on the order of 10(21) cm(-3) and heat treatments at temperatures higher than 100 0 degreesC were still required for the formation of nanocrystals. (C) 2001 MAIK "Nauka/Interperiodica".