Correlation between structural evolution and photoluminescence of Sn nanoclusters in SiO2 layers

Sn nanoclusters are synthesized in 180 nm SiO2 layer after ion implantation and heat treatments in the 400–1100 °C temperature range. The distribution and coarsening of nanoclusters is characterized by Rutherford backscattering spectrometry and transmission electron microscopy and the results are correlated with photoluminescence (PL) measurements. After annealing in N2 in the 400–600 °C range, a monomodal array of Sn nanoclusters with diameters varying from 2 to 3.5 nm is observed in the region around the maximum of the implanted profile. With increasing temperature, this array evolves to different regions of the SiO2 layer. For T ⩾ 700 °C, a cluster band with small particles is observed near to the SiO2 layer surface, whereas the deeper region undergoes a coarsening resulting in large Sn particles of different sizes in metallic and in oxidized phases. The blue–violet (≈3.2 eV) PL of the SiO2 layers shows to be dependent of the structural evolution above mentioned. For the N2 annealed samples, the blue–violet PL intensity increases up to 600 °C and then decreases for higher temperatures. On the other hand, 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.