Evidence for oxide formation from the single and multiphoton excitation of a porous silicon surface or silicon "nanoparticles"

Potential oxidation as monitored by single and multiphoton excitation and associated with the laser induced photoluminescence (PL) from silicon nanoparticles and a porous silicon (PS) surface is considered in the light of recent in situ observations of the photoluminescence process coupled with detailed quantum chemical modeling of the silanone based oxyhydrides. Here, the enhanced oxidation of PS surface bound SiH_x moieties as they undergo multiphoton excitation through the SiH_x stretch vibrational ladder to the quasicontinuum is suggested as a source of the visible PL produced in the 600–800 nm region. Vibrational-to-electronic energy transfer within the SiH_x manifold, as previously suggested, is thought to be unlikely. However, the formation of OSiHx constituencies on the PS surface as these are associated with the silanone-based silicon oxyhydrides would appear to be significant. Evidence for these oxyhydrides may also be apparent in the laser induced PL from silicon nanoparticles. All experimental observations are explained without envoking quantum confinement.