The Theory of Modern Techniques for Surface Structure Analysis

THE THEORY OF MODERN TECHNIQUES FOR SURFACE STRUCTURE ANALYSIS 

Almost all of the existing quantitative data on surface structure was obtained through experimental techniques that involve the propagation and scattering of electrons in solids. This class of surface probes includes the whole range of fine-structure techniques, in addition to LEED and angle-resolved photoemission experiments. This chapter will provide a theoretical description of these techniques and the methods of analyzing the experimental data to determine surface structure. 

General Four-Step Description of Electron-Diffraction Techniques 

The most promising techniques for obtaining detailed surface structural information about molecular adsorbates rely on electron diffraction in one way or another. These include LEED,/27,28,29/ IV-HREELS,/30/ EAPFS,/31/ SEELFS,/32,33/ EXELFS,/34,35/ ARUPS, ARXPS, ARPEFS,/36,37,38/ PE-SEXAFS, SEXAFS, EXAFS, and NEXAFS (XANES). These and other techniques have been discussed above in part 2, and were summarized in Table I. Among these techniques, LEED has been the most productive. 

Either a photon or an electron impinges on the surface. This photon or electron may be polarized to yield additional surface information. The electron, part of a well-collimated and monoenergetic electron beam, may be multiply scattered by surface atoms before reaching step 2. Multiple scattering is most marked at kinetic energies below about 200 eV and can make the process particularly sensitive to the surface structure at these lower energies. 

---