Polarized luminescence of silicon nanoparticles formed in (SiOx–SiOy)n superlattice

Abstract

This work studies the polarization properties of nc-Si nanoparticle radiation in (nc-Si–SiOx–SiOy)n superlattices, formed by successive thermal deposition in a vacuum of solid SiOx and porous SiOy (x < y ≤ 2) nanolayers, and subsequent thermal annealing at 975 °C. Passivation of dangling bonds of silicon atoms at the nc-Si–SiOx interface was carried out by aging in air for 6 months. It was found that, upon excitation of (nc-Si–SiOx–SiOy)n structures with linearly polarized light, the photoluminescence polarization memory effect is observed. It is isotropic in the sample plane. This indicates the presence of anisotropic silicon nanoparticles without preferential orientation in that plane. The spectral dependence of the PL polarization degree (ρ) is investigated at different thicknesses of the active (SiOx) and spacer (SiOy) layers. A dielectric model was used to calculate the asymmetry parameter of the nc-Si in the long-wavelength region of the PL spectrum. The calculations reveal that, with increase in the radiation wavelength (which corresponds to an increase in the size of nc-Si), along with an increase in ρ, the eccentricity of the nanoparticles increases as well.