New functional material: spark plasma sintered Si/SiO₂ nanoparticles - fabrication and properties

A bulk nanostructured material based on oxidized silicon nanopowder was fabricated using a spark plasma sintering technique. Structural investigations revealed that this material has the composition of ∼14 nm core Si granules inside an SiO₂ shell. Photoluminescence measurements have shown that the emission spectra lie in the energy range of 0.6-1.1 eV, which is not typical of the emissions of the Si/SiO₂ nanostructures reported in numerous papers. This result can be explained by the formation of energy states in the bandgap and the participation of these states in both electronic transport and photoluminescence emission. Annealing of the sample leads to a decrease in defect density, which in turn leads to quenching of the 0.6-1.1 eV photoluminescence. In this case ∼1.13 eV inter-band transitions in the Si core start to play a dominant role in radiative recombination. Thus, the possibility of controlling the photoluminescence emission over a broad wavelength range was demonstrated.