Study of clean and oxygen-covered Ag surfaces using optical reflectance anisotropy

We report measurements of the azimuthal anisotropy in the normal incidence reflectance of clean and adsorbate-covered single crystal Ag(110) surfaces. Reflectance anisotropy spectra were taken between 1.5 and 5.5 eV photon energy. Previous studies in air had indicated a very large anisotropy in the region around the surface plasmon energy. On the clean surface this feature is strongly reduced compared to that observed on a contaminated surface. By oxygen dosage the (1 x 1) surface structure is modified to (4 x 1) and (2 x 1) as displayed by LEED. The simultaneously observed optical anisotropy shows a correlation with oxygen coverage and restores to a large extent the anisotropy observed in air.