Structure and light emission of Si-rich Al2O3 and Si-rich-SiO2 nanocomposites

• Effect of Si excess on the properties of Si-rich-Al2O3 and Si-rich-SiO2 films is investigated.
• As-deposited and annealed Si-rich-Al2O3 films are stressed contrary to relaxed Si-rich-SiO2 films.
• Crystallization of Si nanoclusters is faster in Al2O3 films than in SiO2.
• Light emission of Si-rich-SiO2 samples is governed by exciton recombination in Si nanoclusters.
• Luminescence of Si-rich-Al2O3 films is controlled mainly by carrier recombination via host defects.

This work presents the comparative investigation of Six(Al2O3)1−x and Six(SiO2)1−x films with different excess Si content, x, grown by RF magnetron sputtering. Their properties were investigated by means of Raman scattering, X-ray diffraction, Electron paramagnetic resonance and photoluminescence methods. As-deposited films with the x ⩾ 0.3 were found to be two-phase systems that contained an amorphous Si phase. Contrary to Six(SiO2)1−x films, tensile stresses were observed for Six(Al2O3)1−x samples due to lattice mismatch between the film and quartz substrate. The Si nanocrystals (Si-ncs) were formed upon annealing at 1150 °C for 30 min in nitrogen flow in both types of samples. Along with this, for the films with the x > 0.3, amorphous Si phase was also detected, but its contribution was smaller in the Six(Al2O3)1−x films. Besides, the Si-ncs embedded in Al2O3 host remained under tensile stresses after annealing. For the films with the same x values, the Si-ncs in Al2O3 were found to be larger than those embedded in SiO2. Photoluminescence spectra showed that the main radiative channel in Six(SiO2)1−x films is exciton recombination in Si-ncs, while in Six(Al2O3)1−x films the defect related emission prevails due to higher amount of interface defects in the Six(Al2O3)1−x. The nature of these defects is discussed.

Raman scattering (left) and photoluminescence (right) spectra of annealed Six(SiO2)1−x and Six(Al2O3)1−x films versus x.Figure optionsDownload as PowerPoint slide