Effect of ion dose and annealing mode on photoluminescence from SiO2 implanted with Si ions

This paper discusses the photoluminescence spectra of 500-nm-thick layers o f SiO2 implanted with Si ions at doses of 1.6 x 10(16), 4 x 10(16), and 1.6 x 10(17) cm(-2) and then annealed in the steady-state region (30 min) and pulsed regime (1 s and 20 ms). Structural changes were monitored by high-re solution electron microscopy and Raman scattering. It was found that when t he ion dose was decreased from 4 x 10(16) cm(-2) to 1.6 x 10(16) cm(-2), ge neration of centers that luminesce weakly in the visible ceased. Moreover, subsequent anneals no longer led to the formation of silicon nanocrystallit es or centers that luminesce strongly in the infrared. Annealing after heav y ion doses affected the photoluminescence spectrum in the following ways, depending on the anneal temperature: growth (up to similar to 700 degrees C ), quenching (at 800-900 degrees C), and the appearance of a very intense p hotoluminescence band near 820 nm (at >900 degrees C). The last stage corre sponds to the appearance of Si nanocrystallites. The dose dependence is exp lained by a loss of stability brought on by segregation of Si from SiO2 and interactions between the excess Si atoms, which form percolation clusters. At low heating levels, the distinctive features of the anneals originate p redominantly with the percolation Si clusters; above similar to 700 degrees C these clusters are converted into amorphous Si-phase nanoprecipitates, w hich emit no photoluminescence. At temperatures above 900 degrees C the Si nanocrystallites that form emit in a strong luminescence band because of th e quantum-well effect. The difference between the rates of percolation and conversion of the clusters into nanoprecipitates allows the precipitation o f Si to be controlled by combinations of these annealings. (C) 1998 America n Institute of Physics. [S1063-7826(98)01611-1].