PHOTOELECTRON AND AUGER ELECTRON DIFFRACTION OF SURFACES, INTERFACES, AND EPITAXIAL FILMS -- A BRIEF OVERVIEW. Scott A. Chambers, Environmental Molecular Sciences Laboratory Pacific Northwest National Laboratory Richland, WA 99352 USA

The closely-related techniques of Auger and photoelectron diffraction (AED/PED) have evolved into powerful and widely-utilized techniques for qualitative and quantitative surface and interface structure determination. In contrast to LEED and RHEED, which are sensitive to long-range order, AED and PED are governed by the local structural environment surrounding a particular kind of atom in the near-surface region. The elastic scattering and subsequent interference at the detector of an outgoing Auger or photoelectron from the atom of interest is used as a probe of the short-range structural environment. The two techniques share a number of strengths. These include: (i) atom specificity, (ii) no need of long-range order (although the specimen must be a single crystal), (iii) simple and direct interpretation of the most basic features (i.e. zeroth-order forward scattering peaks at high electron kinetic energies), (iv) relatively simple interpretation of higher-order interference fringes by quantum-mechanical scattering theory, and, (v) direct inversion of diffraction patterns to yield accurate, real-space (but domain-averaged) images of nearest and next-nearest neighbor atoms for certain kinds of systems. In this talk, we present the basics of the methods, and illustrate their respective utilities with a representative selection of applications. Examples will include: (i) chemisorption geometry of atoms and small molecules on surfaces, (ii) surface reconstruction geometry, (iii) foreign atom incorporation in the near-surface region, and (iv) tetragonal distortion in ultrathin epitaxial films associated with lattice mismach.