Surface Vibrations on Clean and Hydrogen Saturated W(100)

摘要

Electron energy loss spectroscopy (EELS) and lattice dynamical calculations are used to investigate the vibrational properties of surface phonons and adsorbate phonons on clean and hydrogen-saturated tungsten (100). Two distinct intrinsic surface vibrations are observed in specular scattering geometry. One of the surface modes is attributed to a surface resonance of a bulk longitudinal phonon at the hydrogen-stabilized (1x1) surface. The second surface mode occurs only on the low-temperature-stabilized c(2x2) displacement surface. Detailed experimental studies and lattice dynamical analysis of the hydrogen-saturated W(100) surface accounts for a new hydrogen-derived loss peak at 118 meV in terms of an optic mode of the adsorbed layer. Experimental evidence of impact scattering resonances under certain kinematic conditions are observed.