Surface-plasmon studies on Al (111) and Al (001) single-crystal surfaces using inelastic low-energy electron diffraction

Abstract

Inelastic low-energy-electron-diffraction measurements on single-crystal Al (111) and Al (001) were made. The data required for comparison of the short-wavelength surface-plasmon dispersion on these two faces was obtained. Ultrahigh-vacuum procedures, including in situ sample cleaning and Auger analysis, were used to insure sample cleanliness. The elastic (00) beam energy profiles from Al (001) were measured over extensive ranges of energy and incidence angles in four azimuths. These profiles, which show abundant dynamical effects, were used to select conditions amenable to a kinematic analysis of the inelastic data. The inelastic data from Al (001), which is in the form of angular-selective loss profiles, is similar to that previously obtained from Al (111) except for an additional loss peak found on the former face. A close comparison of the energy positions of the surface-plasmon loss peak on the two faces, using simple conservation-law data analysis, shows the dispersion to be face dependent. The results of a more sophisticated kinematic analysis, which supports and quantifies this conclusion, are discussed briefly.