Blue luminescent silicon nanocrystals prepared by nanosecond laser ablation and stabilized in electronically compatible spin on glasses

Abstract

We investigated the blue luminescent silicon nanocrystal (Si-nc) preparation in liquid spin on glass (SOG) by nanosecond laser ablation of the Si target in SOG. The confinement of laser-generated plasma in liquids significantly enhanced the formation of Si-nc. Furthermore, the silicon-dioxide-based SOG inhibited Si-nc aggregation compared to the case of laser ablation in de-ionized water. The silicon-dioxide-based SOG during the solidification process accelerated Si-ncs surface oxidation and passivation. As a result, visible room temperature photoluminescence (PL) of stabilized Si-ncs in solid SOG was achieved with a maximum located at 2.9eV. This PL spectrum was very similar to that from the Si-nc colloidal solution obtained by laser ablation of the Si target and subsequent aging for six months in de-ionized water. The mathematical description of dynamical Si-nc formation processes within laser plasma confined by liquid SOG was applied to qualitatively describe the obtained results. A Si-nc formation scheme could be described as serial processes of rapid formation and growth of embryotic Si particles, consecutive quick oxidation in SOG, and growth termination by quenching. The quantum confinement size effect and surface∕defect states in the surrounding silicon oxide were responsible for efficient blue PL. The solidification of Si-nc in SOG solution enabled the formation of self-supporting films with well-defined Si-nc concentrations that could be simply varied by laser fluence. The controllability of blue luminescent intensity from a film by laser fluence during laser ablation is of significance for optoelectronic applications.