Modification of surface-state dispersion upon Xe adsorption: A scanning tunneling microscope study

The modification of the surface electronic structure by an adsorbate is mea sured quantitatively with scanning tunneling microscopy and spectroscopy fo r the first time. The standing wave of the Cu surface-state electrons is ut ilized to probe the subtle change in the electronic structure on the Xe-cov ered Cu(111). The observed Fermi wavelength on the Xe-covered surface is lo nger by 15% than on the bare Cu surface. The change upon Xe adsorption is e xplained with the observed modified dispersion of the Cu surface state; upw ard shift by (130+/-20) meV with almost same effective mass.