A Soft/Hard X-ray Beamline for Photoabsorption, Photoemission, and Standing Waves: 0.5-15 keV :

Ten years ago the idea of measuring the local structure of surface atoms with EXAFS was suggested, and since that time the technique of surface-EXAFS, or SEXAFS, has been successfully applied to a growing number of gases, molecules, and solids adsorbed on metal and semiconductor surfaces. The primary factors responsible for the techniques utility derive from the straightforward analysis and information content of the data. The analysis relies on the same single-scattering and theory-independent procedures used in bulk EXAFS, and thus the same short-range information and high degree of accuracy is obtained. In addition, the method is inherently surface sensitive because only adsorbate-specific photoabsorption is monitored, it is polarization dependent because absorption of synchrotron radiation from a 2D layer is anisotropic, and it uses essentially the same equipment (sans synchrotron) as that found in typical UHV systems for preparing and characterizing surfaces. The present overview will highlight the ongoing development of SEXAFS with selected examples obtained at the latest generation of synchrotron facilities and will also draw attention to the inherent and practical limitations of the method. A current assessment of these factors will be aimed at forecasting directions for future study.