Excitation effects and luminescence stability in porous SiO2:C layers

White-light emitting porous SiO2:C layers on silicon wafers have been fabricated by oxidation of carbonized porous silicon. The study was focused mainly on the identification of the mechanism of light emission and photo-induced degradation. The effect of carbonization temperature and exposure to intense ultraviolet irradiation on the photoluminescence (PL) properties was studied by steady state and time-resolved PL measurements. Two types of photo-induced degradation phenomena were observed: reversible and irreversible. The irreversible degradation is suggested to be associated with photo-induced chemical interaction of light emitting material with atmospheric oxygen. It is demonstrated that irreversible degradation can be reduced by encapsulation of the light-emitting material. The structural configuration of light-emitting centers and mechanism of reversible degradation are discussed.