Electron attenuation lengths at SiO 2/Si interfaces

Abstract

The attenuation length, λ, was measured as a function of kinetic energy for low energy electrons (8–70 eV) traveling through SiO 2 with the use of core-level soft x-ray photoemission. Two oxides of different thickness were compared, and the extra attenuation resulting from the additional oxide on the thicker sample was used to determine the attenuation length. The curve resulting from an analysis which employs an exponential attenuation model displays a minima at an electron kinetic energy of ~35 eV, which is a result of scattering from the bulk plasmon. Below 35 eV, λ increases and reaches a local maxima at ~20 eV, at which point λ begins to decrease again. The decrease in λ, at low electron energies arises in part from electron-phonon scattering. This is confirmed by the shape of the bulk Si 2p photoemission peak observed on the thicker oxide sample, which is distorted by the phonon-induced loss processes.