Effect of the gas ambient on the intensity of the visible photoluminescence from Si microcrystallites in a SiO 2 matrix formed by ion implantation
The intensity of the visible photoluminescence at room temperature from Si nanocrystallites formed in SiO 2 by Si + ion implantation and subsequent annealing has been enhanced by employing a second anneal step in a forming gas ambient. Two different wafers were used; one was implanted with a dose of 2 × 10 17 Si + cm -2 at an energy of 200 keV and the other was implanted at energies of 200 and 150 keV with doses of 1 × 10 17 Si + cm -2 at each energy. The implanted samples were first annealed at 1300°C for 30 minutes in a nitrogen ambient and subsequently annealed at 400°C to 1000°C for 60 to 240 minutes in forming gas. Samples from the two wafers had different peak photoluminescent wavelengths at about 750 and 620 nm, respectively, after the first anneal. Both exhibited an enhancement of peak photoluminescent intensity after the second anneal. In another experiment, nitrogen was used instead of forming gas but the increase in intensity was not as large. These phenomena are explained by bond re-ordering and the passivation of the dangling bonds by the introduction of hydrogen.