Si rings, Si clusters, and Si nanocrystals-different states of ultrathin SiOx layers

Amorphous SiO/SiO2 superlattices were prepared by reactive evaporation of SiO powder in an oxygen atmosphere. Infrared absorption and photoluminescence spectra were measured as a function of annealing temperature. Three photoluminescence emission bands were observed. A band centered at 560 nm is present in as-prepared samples and vanishes for annealing above 700 degreesC. The second band around 760 nm to 890 nm is detected for annealing temperatures above 500 degreesC. A strong red luminescence is observed for annealing temperatures above 900 degreesC. The origin of the different photoluminescence bands and different states of the phase separation of ultrathin SiOx layers is discussed. (C) 2002 American Institute of Physics.