Spatial distribution of light-emitting centers in Si-implanted SiO2

Light emission from Si-implanted SiO2 layer is a well-known phenomenon. We demonstrated that samples which were implanted with 28Si at a dose of 1.5×1017 cm−2 at 100 keV and annealed at 1050 °C for 2 h exhibit two broad photoluminescence (PL) peaks at ∼650 and 850 nm. The origin of these peaks was investigated by a controlled etch experiment in order to figure out the dependence of the PL spectrum on the location of the implanted Si atoms. It was found that the emission peak of 850 nm is correlated with the Si atom distribution in the matrix and hence with the distribution of Si nanocrystals formed upon annealing, while the emission centers for the 650 nm peak are located in the near surface region. In a parallel experiment, the dependence of the PL spectrum on the excitation wavelength was studied. PL spectrum shifted to higher energies with increasing photon energy due to the selective excitation of the light-emitting centers.