Au implantation at 32 keV into Si(100), in a fluence range of 1 x 10(15)-1 x 10(17) cm(-2), has been used to produce a gold-rich damaged Si layer of thickness around 30 nm. Local recrystallization of this layer, induced by 1.5 MeV Au irradiation, to a fluence of 1 x 10(15) cm(-2), has been studied using Raman scattering, photoluminescence (PL) and x-ray photoemission spectroscopy (XPS). For a sample with a low energy Au fluence of 5 x 10(15) cm(-2), the MeV Au irradiation has been found to result in Si nanocrystal (NC) formation. The size of the NCs, as estimated from the PL data, has been found to be about 4 nm, which agrees well with the result of a thermal spike model calculation. Annealing of the sample at 500 degrees C resulted in an enhanced PL signal, without any significant shift in peak position, indicating an increase in the local concentration of the NCs. In the case of samples with an initial Au fluence above 1 x 10(16) cm(-2), the MeV Au irradiation has been found to result in better overall recrystallization of the amorphous layer, with silicide formation as observed by XPS. However, there was no PL signal, indicating the absence of Si NCs in the system. The results suggest that the initial amorphizing Au fluence plays a crucial role in Si NC formation induced by MeV ion irradiation.

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Nanocrystalline Sn particles have been formed in silica glass through 50 keV Sn− implantation followed by annealing in N2 at 650 °C for 30 min. Samples prepared this way have been annealed in air for 1 h, separately at four different temperatures, 400, 600, 800, and 1000 °C, each at a given temperature. Annealing at temperatures higher than 400 °C has been found to result in oxidation of the Sn nanoparticles (NPs) and formation of the SnO2 phase as confirmed from optical absorption (OA), transmission electron microscopy, and Raman scattering measurements. For the sample annealed at 600 °C, Raman scattering data showed three bands at about 525, 629, and 771 cm−1, the last two corresponding to the A1g and B2g classical Raman modes of rutile SnO2. Increase in annealing temperature resulted in an increase in the intensities of the A1g and B2g modes showing better crystallinity. Also, the A1g peak shifted toward a higher wave number with a steady decrease in the intensity at 525 cm−1. This is in line with the growth in size of NPs as well as a reduction in the surface disorder. The Urbach tail width derived from the OA data also agrees with this.

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