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The Compton profile (CP) of polycrystalline CuO has been measured using 60 keV gamma -rays. In the absence of rigorous theoretical results the obtained data have been analysed in terms of CPS calculated within the framework of the renormalized-free-atom model, employing several wavefunctions for the 0 2p state. Compared with 3d102p5, the CP for the 3d92p6 configuration was found to be in better agreement with the experimental data. As in MgO, here also Watson's+1 well solution of the 0 2p state was found to provide better results than the rest. However, the best results were obtained with a configuration given by 3d9.42p5.6. The implications of this are discussed.

Ultraviolet (UV) photoluminescence (PL) data taken on a double Au implanted Si matrix are reported. This has been studied over a wide temperature range of 28–220 K. At low temperature, the spectrum shows four peaks corresponding to a zero-phonon line (ZPL) and three low-energy phonon-assisted lines. At 28 K the ZPL has an energy of 3.362 eV with a lifetime of ∼240 ps suggesting transitions across a direct gap. The temperature variation of the ZPL intensity indicates an activation energy ∼10 meV comparable to the binding energy of excitons in crystalline Si (c-Si). For T > 100 K, it shows a redshift which can be understood as coming from exciton–phonon interaction. At lower temperatures the corresponding line broadening shows evidence of interaction with low-energy phonons of average energy ∼7 meV as suggested earlier. All the above results indicate the emission to be coming from Si nanoclusters (NCs) embedded in the matrix.

The effects of annealing atmosphere (argon or oxygen) on Zn nanoparticles (NPs), embedded in silica glass, synthesized by implanting 50 keV ZnO− ions to a fluence of 7 × 1016 cm−2 have been studied. Optical absorption (OA) measurements carried out on the as-implanted samples have been found to result in a surface plasmon resonance (SPR) band centred at ∼255 nm due to the presence of Zn NPs in the silica glass. An increase in SPR peak intensity with a corresponding reduction of its full width at half maximum have been seen in the OA spectrum taken from the as-implanted sample following annealing in Ar ambient at 700 °C for 2 h, indicating a growth in the size of Zn NPs. However, annealing the as-implanted sample in O2 gas at 700 °C for 2 h has been found to result in a steep absorption edge at ∼364 nm in the OA spectrum which indicates the formation of ZnO NPs. These ZnO NPs show quantum confinement effects due to their small sizes. No observable photoluminescence (PL) emission has been seen from Zn NPs, whereas an excitonic band at ∼368 nm and three deep-level PL emission bands at ∼453 nm, ∼521 nm and ∼650 nm, respectively, have been seen from ZnO NPs. It was argued that the deep-level PLs were due to the singly ionized oxygen vacancies located at ZnO NPs' surfaces. These observations suggest that ZnO NPs were formed due to oxidation of Zn NPs via interaction with the indiffusing O2 molecules during annealing in O2 ambient, but not with the interaction of the implanted oxygen in silica glass.

We have studied the influence of substrate surface roughness on the growth of Ge on self-affine fractal Si surfaces. Self-affine fractal surfaces can be prepared by irradiating surfaces of solid materials with an energetic ion beam, which modifies the surface morphology predominantly via an erosion process. By tuning the ion beam energy, surface parameters such as surface roughness (σ0) and correlation length (ξ), can be controlled. Values of σ0 and σ0/ξ affect the effective free energy of the surface. When materials are grown on surfaces with different values of surface roughness parameters, the morphology of the deposited layer is expected to be influenced. In comparison with an earlier study where 2 MeV Si ion irradiation was used, we have produced surfaces with larger values of σ0 and σ0/ξ by irradiating the surfaces with 45 keV Si ions. We have made a comparison for Ge growth on Si surfaces irradiated with 2 MeV and 45 keV Si ions and have observed remarkably different growth behaviour. Upon Ge deposition, in the former case, the surface roughness decreases at smaller length scales and remains practically unchanged at larger length scales. This indicates that Ge has grown preferentially within the valleys of the rough surface. In the latter case, where σ0 is large and ξ is small on the substrate surface, the roughness increases at all length scales by almost a factor of 2, upon Ge deposition, indicating the lack of preferential growth within the surface valleys. Following Ge deposition, in the former case the roughness exponent increases from 0.82 to 0.99, while in the latter case it remains practically unchanged (~0.83). Roughness parameters of the substrate surface are found to have a significant influence on the morphology of the overlayers.

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.