ION-SCATTERING AND SCANNING-TUNNELING-MICROSCOPY STUDIES OF STEPPED CU SURFACES

The structure and dynamics of stepped Cu(115) surfaces and their behav iour under oxygen adsorption was studied by ion scattering spectroscop y (ISS) and scanning tunneling microscopy (STM). Azimuthal ion intensi ty distributions show pronounced minima along the first layer atom row s which can be reproduced by MARLOWE simulations. Detailed analysis in the backscattering mode indicates relaxation of step edge atoms. Incr easing the surface temperature leads to scattering into otherwise bloc ked regions of the azimuthal and polar intensity distributions that ca n be explained by the production of adatoms or kinks along the [1 (1) over bar 0] step edges, This thermal roughening is observed above an o nset temperature of about 390 K and is completely reversible. These re sults are supported by STM studies that show that regular monoatomic s teps are rather stable at room temperature, whereas for double steps p ronounced kink motion is observed with an activation energy of about 0 .1 eV. Oxygen adsorption causes pinning of the steps and above tempera tures of about 500 K it leads to strong faceting of the surface with ( 014), (104) and (113) faces.