Samarium-induced enhancement of SiOx decomposition and Si nanocrystals formation.

The effect of Sm on thermally stimulated decomposition of SiO_x and the formation of silicon nanocrystals during high-temperature air annealing was studied by measuring the spectra of photoluminescence (PL), infrared (IR) reflection and transmission and Micro-Raman scattering (RS). The SiO_x: Sm films were produced by thermal co-evaporation of silicon monoxide and metallic samarium powders in a vacuum onto polished c-Si and silica substrates. The Sm concentration varied from 0.8 to 2.0 wt. %. In the SiO_x: Sm films annealed at 970 ºC, an intense PL band of silicon nanocrystals was found in the 850–900 nm region, the position and intensity of which depend on the samarium concentration. The formation of Si nanocrystals in those films is also confirmed by studying their Raman spectra. At the same time, no Si nanocrystals were found in undoped SiO_x films annealed under similar conditions. The analysis of these spectra made it possible to determine the sizes of silicon nanocrystals: 3.7 nm from the PL spectra and 3.6 nm from the Raman spectra. A possible mechanism of thermally stimulated interaction of Sm atoms with the SiO_x matrix is discussed. [ABSTRACT FROM AUTHOR]