Si/SiO2 multilayers: synthesis by reactive magnetron sputtering and photoluminescence emission

This paper relates a complete study of Si/SiO2 multilayer (ML) structures. First, we suggest an original way of synthesis based on reactive magnetron sputtering of a pure silica target. The photoluminescence spectra of these MLs consist of two Gaussian bands in the visible-near infrared spectral region. The stronger one (I band) is fixed at about View the MathML source and probably due to interface states. The weaker one (Q band) is tuneable with the Si sublayer thickness and originates from a radiative recombination within the nanosized Si layers. For this latter band the peak position is a function of the Si sublayer thickness and shows a discontinuity at View the MathML source. This corresponds to an Si phase change. For thicknesses above View the MathML source, the sublayers are composed of nanocrystalline silicon whereas below View the MathML source the sublayers are made of amorphous silicon. We develop a model based on a quantum well to which we have added an interfacial region between Si and SiO2. It is characterised by an interfacial potential of View the MathML source. This model depicts the simultaneous behaviour of Q and I bands for an Si sublayer thickness below View the MathML source.