Adsorbate-induced surface-phonon softening on Pt(111)

Abstract

Inelastic helium-scattering measurements have been used to investigate the influence of oxygen adsorption on the Pt(111) surface phonons. Oxygen was found to form a (1\ifmmode\times\else\texttimes\fi{}1) overlayer with nearly unity coverage at elevated surface temperatures. Such an overlayer is shown to induce a remarkable softening of the Pt surface phonons, which is interpreted as a reduction in the Pt attractive interaction arising from sp-electron donation to the oxygen overlayer.