Band gap tuning in Si-SiO₂ nanocomposite: Interplay of confinement effect and surface/interface bonding

Highlights: • Si-SiO₂ nanocomposites studied using Raman mapping, XPS and absorption spectroscopy. • Correlation between size and Si−O bonding at the Si-SiO₂ interface is established. • Both electron confinement and oxidation bonding environment play an important role. • Lowering of direct band-gap ∼2.8 and 2.95 eV in a Si nanocrystal is understood. • This can allow easy optical microscopy monitoring of Si-SiO₂ based devices. - Abstract: Correlation between size, bonding of Si and O at the surface/interface of Si nanocrystals and frequency of Si phonons in Si-SiO₂ nanocomposites is established using Raman mapping and X-ray photoelectron spectroscopy. Corroboration of these results with absorption spectroscopy shows that lowering of direct transition of light electron conduction band to heavy hole valence band ∼2.8 and 2.95 eV is a result of the interplay between effect of electron confinement (increases band gap) and oxidation bonding environment at the surface/interface (decreases band gap) of a nanocrystal in Si-SiO₂ nanocomposites. These studies have generated deeper insight into the fundamental understanding of the nanocomposite, which can allow easy optical microscopy monitoring of Si-SiO₂ based device fabrication.