Effects of thermal oxidation on the photoluminescence properties of porous silicon

The effects of thermal oxidation on the photoluminescence (PL) properties of powdered porous silicon (PSi) are studied using X-ray photoelectron spectroscopy (XPS). It is found that the PL intensity is steeply quenched after annealing at ∼300∘C and recovered at above ∼700∘C. The XPS intensity of oxides formed on the PSi surface is also found to strongly depend on the annealing temperature. The comparison between the annealing temperature dependence of PL intensity and that of the oxide XPS intensity suggests that the formation of thin disordered SiO2 layer accompanies the quenching of the PL intensity, and that the formation of thick high-quality SiO2 layer results in the PL intensity recovery. These results indicate that the thickness and quality of SiO2 layer play a crucial role in the PL properties of thermally oxidized PSi.