Structural investigations by means of directional elastic peak electron spectroscopy

Abstract

We present examples of structural investigations performed with the use of directional elastic peak electron spectroscopy (DEPES). In this method the intensity of elastically backscattered electrons is recorded as a function of the incidence angle of the primary electron beam by using a retarding field analyzer. Due to the forward focusing of primary electrons at energies in the range of 0.5-2.0keV the identification of the short-range order within the first few atomic layers of crystalline samples is possible. The data recorded for the clean Cu(111), Pt(111), Ru(10-10), and Ru(0001) surfaces, as well as for the Cu/Ru(10-10), O/Ru(10-10), Cu/Pt(111), and Pb/Ru(0001) adsorption systems are presented in the form of stereographic distributions, which reveal the characteristic intensity maxima associated with the close packed rows of atoms. The experimental data are compared with the theoretical results obtained by applying the multiple scattering theory. In this work we present the experimental and theoretical issues associated with the incident electron beam scattering effects, and give examples of investigations performed for different substrates and adsorption systems. The qualitative and quantitative analysis of the data is presented. The contribution of different sample layers to the DEPES intensity distribution is shown and the anisotropy distributions are analyzed. The identification of the crystalline structure of samples, determination of domain and terrace populations, as well as adsorption sites of adatoms on the substrate are presented.