Crystalline structure of copper-gold alloys investigated by DEPES: Theoretical approach

We present results of calculations concerning the angle integrated electron emission from crystalline samples as a function of the incidence angle of the primary electron beam. Diffraction processes of primary electrons in directional elastic peak electron spectroscopy (DEPES) were described by the single scattering cluster (SSC) approximation applied to clusters composed of sublattices formed by different atoms. Theoretical polar profiles were calculated for Cu(0 0 1), Au(0 0 1), AuCu(0 0 1), and AuCu₃(0 0 1) in terms of phase shifts, inelastic mean free paths and scattering cross-sections. In calculations a real experimental geometry was considered concerning the acceptance angle of the analyser and polar rotation of the sample. Profiles calculated for particular incident electron beam energies depend on the structure and stoichiometry of crystalline samples. Application of above investigations is discussed in the context of superficial alloy formation and order-disorder transitions associated with the change of the concentration and order of alloy components in first few atomic layers.