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

Abstract

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 °C. The second band around 760 nm to 890 nm is detected for annealing temperatures above 500 °C. A strong red luminescence is observed for annealing temperatures above 900 °C. The origin of the different photoluminescence bands and different states of the phase separation of ultrathin SiOx layers is discussed.