Modelling of non-uniform electrical potential barriers for metal surfaces with chemisorbed oxygen

Abstract

A modelling approximation regarding the behaviour of electrons on metal surfaces with chemisorbed oxygen is presented. It is suggested that, as consequences of O-metal surface bonding, ionization, polarization and removal of metal atoms cause the non-uniformity in the surface potential barrier (SPB). The inelastic potential is formulated by using a Fermi-type spatial decay and the work function that depends on the occupied density of state. This formulation takes into account that, at energies below the plasma excitation energy, electron excitation dominates and that the electron excitation occurs in the electron-occupied space with any energy greater than the work function. The present modelling method is an improvement in that (i) the elastic potential, the spatial decay and the energy dependence of the inelastic potential are associated with the electron distribution, ρ(z); (ii) all the SPB parameters are functionalized as dependents of the origin of the image plane, z0, or the boundary of the region occupied by electrons; (iii) the spatial localization and the variation in energy state are taken into account; and (iv) the single-variable parameterized SPB simplifies the very-low-energy electron diffraction calculations and ensures the uniqueness of the solutions. This method allows us to optimize crystal structures by uniquely comparing the shapes of the geometry-dependent z0(E) curves that exhibit joint features of topography and spectroscopy revealed by STM/STS