DIRECT IMAGING OF MONOLAYER AND SURFACE ATOMIC-STRUCTURE BY ANGULAR-DISTRIBUTION AUGER MICROSCOPY

Presented here are complete angular distributions of Auger electrons emitted from Pt(111), Ag(111), Cu(100), and an adsorbed monolayer of iodine on Pt(111). These samples were chosen because there is agreement as to their surface structure, providing a foundation on which to compare the nature of the observed distributions to the structural properties of the surface. In particular, the dependence of the angular distribution on the Auger electron kinetic energy was investigated by obtaining data at more than one energy for each metal. In each case, angular distributions from crystalline samples contain intensity minima ("silhouettes") along the internuclear directions for Auger kinetic energies < 100 eV. Above 100 eV, the intensity minima are gradually replaced with maxima along directions parallel to the clearest channels through the crystal. Near grazing angles of detection, the angular distributions of 507 and 518 eV iodine Auger electrons emitted from a monolayer of iodine on Pt(111) contains intensity minima along directions corresponding to the I-I internuclear directions. These results indicate that the presence of intensity maxima or minima along the internuclear directions is not merely a function of Auger electron kinetic energy, but also depends upon the nature of the sample.