IMAGING SURFACE ATOMIC LAYERS BY MEANS OF AUGER ELECTRONS

Auger electron angular distributions yield images of surface atomic and molecular structure. Angular distribution Auger microscopy (ADAM) produces silhouettes of near-surface atoms by illuminating them with Auger electrons originating from atoms located deeper in the solid. The silhouettes are then observed by measurement and display of the complete angular distribution of Auger electrons. The locations and shapes of these silhouettes directly reveal the relative positions of atoms near the surface, and also provide important new information regarding the interaction of electrons with matter. Interpretation of ADAM images is straightforward in terms of atoms behaving as point emitters and spherical scatterers of Auger electrons. Consequently, ADAM is an exciting new technique for structural characterization of materials surfaces, thin films, molecular layers and crystals, and also for fundamental studies of electron physics, provided that certain important experimental criteria are met. We will illustrate the ADAM technique by describing its recent application to determination of the structure of metal single-crystal surfaces and epitaxial atomic layers.