SYNTHESIS AND LUMINESCENCE OF SILICON REMNANTS FORMED BY TRUNCATED GLASSMELT-PARTICLE REACTION

We have obtained nanometer sized silicon remnants sequestered in glass matrices by terminating the reaction of pure silicon powders disperse d in the viscous melt at a temperature of 1400-degrees-C. Repeated use of this truncated melt-particle reaction process dilutes the amount a nd size of silicon remnants, and bulk samples containing nanosize sili con crystallites embedded in a glass matrix were eventually obtained. These quantum dot sized silicon-in-glass materials emit greenish lumin escence with peak wavelengths from almost-equal-to 480 to 530 nm, cons iderably shorter than the reddish luminescence (at about 700-850 nm) o bserved in porous silicon structures prepared by electrochemical etchi ng techniques; upon complete digestion of Si particles by the melt, th e luminescence peaks disappear. Since our silicon-in-glass preparation method does not involve etching, the origin of the luminescence is no t likely to be due to Si-O-H compounds (e.g., siloxene) postulated rec ently. The location of the luminescence peaks and the observed silicon crystallite size suggest quantum confinement leading to a widened sil icon band gap arising from remnants in the glass matrix smaller than t he exciton diameter of bulk silicon (10 nm).