Optical and Structural Properties of Silicon Nanocrystals and Laser-Induced Thermal Effects

Abstract

Si nanocrystals in silica are attractive for photonic applications. Various optical functions can be realized in this way (for example, light emission). The optical and structural properties of a variety of such materials are described and compared here. It is found that Si nanocrystals with diameters 3-4 nm are not a direct source of the 1.5-eV photoluminescence. Furnace annealing at temperatures up to 1200°C does not complete the Si-SiO2 phase separation, and the suboxide phase and very small Si clusters should be accounted for when discussing light-emission mechanisms. Laser-induced thermal effects on optical and structural properties of free-standing films are described in detail. Laser annealing produces macroscopic Si-SiO2 phase separation and compressive stress on Si nanocrystals. The laser-induced structural changes offer an approach to optical memory with a high data density and superior thermal stability.