Application of two-electron spectroscopy in reflection for studying electronic structure of surfaces and thin films

Since first observations of the (e,2e) reaction in reflection geometry on solid surfaces this phenomenon was thoroughly investigated in order to understand the mechanism of two correlated electrons emission. At the same time this technique has been developing to become a spectroscopic tool for studying solid surfaces. In this contribution we present two examples of how valuable information on electronic structure of solid surface can be extracted from the (e,2e) spectra. The first concerns a dielectric LiF film and the second a ferromagnetic ultra-thin Co film. The combination of (e,2e) and electron energy loss spectroscopy allows the measurement of the energy gap E-g, valence bandwidth Delta E, electron affinity X and excitonic levels position E-ex of the dielectric. These parameters depend on the thickness, morphology and crystallinity of the film that were studied by transmission and scanning electron microscopy. In case of the Co film a spin-polarized incident electrons were used to probe spin-dependent features of the cobalt valence band. (c) 2007 Elsevier B.V. All rights reserved.