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

High resolution analytical transmission electron microscopy was used to cha racterize the structural features of light emitting Si/SiO2 multilayers. El ectron energy-loss spectra were recorded in the low-loss region 0-40 eV, ac ross Si/SiO2 interfaces in cross-sectional specimens. The Si/SiO2 multilaye r had a major volume plasmon peak at 17.5 eV and a broad feature ranging fr om 7 to 13 eV. This energy range could be deconvoluted into two different p eaks located at similar to 9 and 12 eV. These plasmon peaks could in turn b e related to the silicon nanocrystallites and surface plasmon oscillations at the interface between the nanometer size silicon and SiO2 layers, respec tively. Complex dielectric function was extracted from the experimental sin gle-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. (C) 1998 American Instit ute of Physics. [S0021-8979(98)05324-9].