Photoluminescence, electron spin resonance, and high-resolution transmission electron microscopy methods were used to investigate the luminescence mechanism in Si nano-crystals. Ions were implanted (190keV Si, 3 x 1017/cm2) into SiO2 films, and an intense photoluminescence band at 755nm (1.65eV) was observed when the implanted films were annealed at temperatures above 800C in air or N. The use of high-resolution transmission electron microscopy revealed Si nano-crystals with sizes of between 1 and 6nm in the annealed samples. The use of electron spin resonance methods revealed the presence of Si dangling bonds. During annealing for a few times at 900C, in air, the particle size was reduced to less than 2nm; due to oxidation. A red photoluminescence band was attributed to emissions from Si nano-crystals.

S.Guha, M.D.Pace, D.N.Dunn, I.L.Singer: Applied Physics Letters, 1997, 70[10], 1207-9