Strong photoluminescence with fine structures from sandwich-structured films of silicon nanoparticles embedded in Al2O3 matrices

Sandwich-structured thin films of silicon nanoparticles embedded in Al2O3 matrices were prepared by pulsed laser ablation on a slowly rotating target which alternately exposed the Si and Al2O3 materials to the laser beam. SIMS profile studies showed that the sharpness of the demarcation boundary between the Si and Al2O3 layers depended strongly on their annealing conditions. Correspondingly, the photoluminescence (PL) of the films was likewise found to depend strongly on annealing conditions. Very high-intensity and stable PL was achievable under the most appropriate annealing conditions. In addition, the PL spectra also contained multiple fine structures which did not depend on the annealing conditions. Annealing caused a significant blueshift of the main peak, but no corresponding blueshift of the fine structures was observed. Our results can be interpreted in relation to the quantum confinement model of the observed PL. The fine structures are attributed to the different interfacial states between the silicon nanocrystals and aluminum oxides. The intensity of the PL was strongly affected by the conditions of the Si–Al2O3 interfacial states in the films.