Substrate-dependent crystallization and enhancement of visible photoluminescence in thermal annealing of Si/SiO2 superlattices

Abstract

We study annealing of Si/SiO2 superlattices on fused quartz and crystalline Si substrates. Under annealing at 1200 °C, the superlattices on Si undergo partial crystallization involving clusterization of Si layers through ultrathin (1 nm) oxide, and visible photoluminescence (∼2.1 eV) strongly increases for the samples with thinner Si layers (⩽2.5 nm). The annealed superlattices on quartz exhibit a higher disorder, tensile stress, and weaker visible photoluminescence. The results do not support assignment of the observed visible photoluminescence to quantum confinement in Si crystallites but rather indicate that it originates from Si=O bonds stabilized in the Si/SiO2 network.