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

We study annealing of Si/SiO2 superlattices on fused quartz and crystalline Si substrates. Under annealing at 1200 degreesC, the superlattices on Si u ndergo partial crystallization involving clusterization of Si layers throug h ultrathin (1 nm) oxide, and visible photoluminescence (similar to2.1 eV) strongly increases for the samples with thinner Si layers (less than or equ al to2.5 nm). The annealed superlattices on quartz exhibit a higher disorde r, tensile stress, and weaker visible photoluminescence. The results do not support assignment of the observed visible photoluminescence to quantum co nfinement in Si crystallites but rather indicate that it originates from Si =O bonds stabilized in the Si/SiO2 network. (C) 2001 American Institute of Physics.