DETERMINATION OF THE SURFACE-BARRIER IMAGE-POTENTIAL ORIGIN ON Cu(001) FROM VERY LOW-ENERGY ELECTRON DIFFRACTION

Abstract

A set of experimental very low-energy electron diffraction VLEED intensities on Cu(001) for angles of incidence of 35°, 40°, 50°, 60°, 70° and 80° in the (11) azimuth obtained by Dietz, McRae and Campbell has been analyzed using a surface-barrier model which allows for the angle and energy dependence of both the saturation from the image form and the height of the barrier potential. All three parameters of the potential form were allowed to vary independently. It is found that a fit between experiment and theory of the energy position of all the features (minima and maxima) in the entire data set to ≤ 0.07 eV can be obtained with the image-plane origin at z0=-1.70± 0.05 Å from the center of the first row of atoms with a barrier height U0increasing in energy from 11.6 eV with respect to the muffin-tin zero at 35° incidence to 13.1 eV at 80°. The saturation from image form is found to show no trend in variation with respect to the energy or angle of approach of the electron to the barrier and has a value of UD=5.4± 1.0 eV with respect to the vacuum level at the jellium discontinuity. The value of z0and barrier form found here differs from that of previous work of others and the analysis uses the largest VLEED data set to date.