Sn nanoclusters are synthesized in 180 nm SiO2 layers after ion implantation and heat treatment. Annealings in N2 ambient at high temperatures (T≥700 °C) lead to the formation of Sn nanoclusters of different sizes in metallic and in oxidized phases. High-resolution transmission electron microscopy (TEM) analyses revealed that the formed larger nanoparticles are composed by a Sn metallic core and a SnOx shell. The corresponding blue-violet photoluminescence (PL) presents low intensity. However, for heat treatments in vacuum, the PL intensity is increased by a factor of 5 and the TEM data show a homogeneous size distribution of Sn nanoclusters. The low intensity of PL for the N2 annealed samples is associated with Sn oxidation.