Study of the photoluminescence of amorphous and crystalline silicon clusters in SiOx thin films

A simple reactive evaporation method is proposed to prepare light-emitting SiOx thin films. Pure silicon is evaporated in a controlled molecular oxygen atmosphere. By changing the pressure in the preparation chamber, x can be varied from 0.7 to 1.85. The samples were annealed in the range 350-1100 °C. The composition and the structure of the films were investigated using energy dispersive X-ray, infrared absorption, Raman, X-ray photoelectron spectroscopies and X-ray diffraction. The samples contain silicon clusters dispersed inside an insulating silicon oxide matrix. For annealing temperatures lower than 950 °C, the samples are still amorphous and the photoluminescence in the visible range is obtained for x values ranging from 1.3 to 1.6. For higher annealing temperatures the silicon clusters crystallize and the photoluminescence is still observed only for x = 1.6. In the crystalline state, the photoluminescence is more intense and the confinement effect seems to be stronger than in the amorphous state.