Effect of the annealing atmosphere on the Au site in Er + Au-implanted silica

The Au site in Er + Au-implanted silica has been investigated by X-ray absorption spectroscopy, after annealing at 600 °C in either neutral N2 or reducing H2 (4%):N2 (95%) atmosphere. High-resolution X-ray fluorescence spectra collected near the Au LIII-edge indicate the presence of oxidized Au atoms in the N2-annealed sample. Correspondingly, the EXAFS analysis shows a weak Au–O coordination only for the sample annealed in neutral atmosphere. For both cases, the EXAFS results evidence the presence of sub-nanometer metallic Au clusters: the cluster size, always below 1 nm, is smaller for the sample annealed in reducing atmosphere. The Au clusters embedded in the Er-doped layer promote a strong enhancement of the Er photoluminescence emission at 1.5 μm.