Transmission electron energy-loss spectroscopy measurements of the dielectric function of Si/SiO2 multilayers

Abstract

High resolution analytical transmission electron microscopy was used to characterize the structural features of light emitting Si/SiO2 multilayers. Electron energy-loss spectra were recorded in the low-loss region 0–40 eV, across Si/SiO2 interfaces in cross-sectional specimens. The Si/SiO2 multilayer had a major volume plasmon peak at 17.5 eV and a broad feature ranging from 7 to 13 eV. This energy range could be deconvoluted into two different peaks located at ∼9 and 12 eV. These plasmon peaks could in turn be related to the silicon nanocrystallites and surface plasmon oscillations at the interface between the nanometer size silicon and SiO2 layers, respectively. Complex dielectric function was extracted from the experimental single-scattering distribution using Kramers–Kronig analysis. This showed the existence of an optical band gap at 1.5 eV. The first resonance peak in the imaginary part of the complex dielectric constant was seen at 1.9 eV. This resonance peak is generally related to the structural short range ordering and quantum confinement in a Si/SiO2 multilayers.