Microscopic investigations of advanced thin films for photonics

We present the different approaches we recently followed to achieve intense room temperature photoluminescence (PL) from Si-based materials. On one side we obtained sub-bandgap PL from H-related defects induced by the H-2 plasma treatment of Si photonic crystal (PhC) nanocavities. We demonstrated that a strong and narrow PL emission can be obtained in the PhC nanocavities due to the formation of a damaged layer mainly consisting of nanometric platelets and bubbles. An overall 40000-fold enhancement of the PL signal, with respect to pure crystalline Si, has been achieved and moreover the signal can be tuned in a wide range by only changing the PhC parameters. On the other side, we focused our attention on the properties of SiO2 and SiOC host matrices doped with Eu ions. C addition produces a strong enhancement of the Eu PL with respect to pure SiO2 films. The chemical and structural characterization of these materials reveals an extensive Eu clustering in SiO2-based films, while C addition induces a significant reduction of this phenomenon, enhancing the fraction of optically active Eu ions. These results can be applied for the realization of efficient Si-based light sources.