The effect of composition on the formation of light-emitting Si nanostructures in SiOx layers on irradiation with swift heavy ions

The SiOx layers different in composition (0 < x < 2) are irradiated with Xe ions with the energy 167 MeV and the dose 1014 cm−2 to stimulate the formation of light-emitting Si nanostructures. The irradiation gives rise to a photoluminescence band with the parameters dependent on x. As the Si content is increased, the photoluminescence is first enhanced, with the peak remaining arranged near the wavelength λ ≈ 600 nm, and then the peak shifts to λ ≈ 800 nm. It is concluded that the emission sources are quantum-confined nanoprecipitates formed by disproportionation of SiOx in ion tracks due to profound ionization losses. Changes in the photoluminescence spectrum with increasing x are attributed firstly to the increase in the probability of formation of nanoprecipitates and then to the increase in their dimensions; the latter effect is accompanied with a shift of the emission band to longer wavelengths. The subsequent quenching of photoluminescence is interpreted as a result of the removal of quantum confinement in nanoprecipitates and their coagulation.