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Thermally grown SiO2 on Si substrates implanted with Si+ ions with a dose of 6×1016 cm−2 were studied by the techniques of photoluminescence, electron paramagnetic resonance (EPR), and low-frequency Raman scattering. Distinct oxygen-vacancy associated defects in SiO2 and nonbridging oxygen hole centers were identified by EPR. The luminescence intensity in the 620 nm range was found to correlate with the number of these defects. The low-frequency Raman scattering technique was used to estimate the average size of the Si nanocrystallites formed after the implantation and thermal annealing at T>1100 °C, which are responsible for the photoluminescence band with a maximum at 740 nm. The intensity of this band can be significantly enhanced by an additional treatment in a low-temperature rf plasma.

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Photoluminescence (PL), photoluminescence excitation (PLE), and Raman spectra of Si–SiOx layers were measured as a function of Si content. Samples were prepared by co-sputtering of Si and SiO2 and post-annealing. The average size of Si nanoparticles was estimated from Raman measurements. It was shown that, in general, the PL spectra consist of two bands with maxima in the ‘red’ and ‘green’ spectral ranges. The ‘red’ PL band is complex and contains two (IR and red (R)) components. The shift of the peak position of the IR component from 1.38 to 1.54 eV correlates with the decrease of the Si nanoparticle size from 5 to 2.7 nm. It was shown that this PL component could be ascribed to carrier recombination in silicon nanoparticles. The R component of the ‘red’ band as well as the ‘green’ band have similar dependences of the peak positions and intensities on the Si content and can be ascribed to defect-related luminescence. It was concluded that the light absorption in silicon nanocrystallites plays the main role in PLE process. Hot-carrier participation in the excitation of defect-related bands was deduced.