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The effect of the annealing temperature and the SiO 2 barrier thickness of silicon nanocrystal (NC)/SiO 2 superlattices (SLs) on their structural and optical properties is investigated. Energy-filtered transmission electron microscopy (TEM) revealed that the SL structure is maintained for annealing temperatures up to 1150 C, with no variation on the nanostructure morphology for different SiO 2 barrier thicknesses. Nevertheless, annealing temperatures as high as 1250 C promote diffusion of Si atoms into the SiO 2 barrier layers, which produces larger Si NCs and the loss of the NC size control expected from the SL approach. Complementary Raman scattering measurements corroborated these results for all the SiO 2 and Si-rich oxynitride layer thicknesses. In addition, we observed an increasing crystalline fraction up to 1250 C, which is related to a decreasing contribution of the suboxide transition layer between Si …