Low temperature Ni atom adsorption on the Au(110)-(1x2) surface

Submonolayer Ni films, deposited between 130 and 180 K on the missing-row reconstructed Au(110)-(1 x 2) surface, have been analysed with STM. Al 130 K, no indication for alloying or atomic exchange is found. Both the lateral distribution of Ni atoms is determined on an atomic scale and the hopping rate of individual atoms is measured. The contribution of the initial adsorption process and of thermal diffusion are discerned. The barrier for thermal diffusion of adsorbed Ni monomers is determined to E-d = 0.52 +/- 0.1 eV, whereas Ni atoms bound in dimers are less mobile. The population of. second-layer sites compared with random adsorption is enhanced at 130 K and reduced at 180 K, when thermal interlayer mobility of. Ni adatoms sets in. After adsorption at 130 K, Ni is very evenly distributed over the surface. the local coverage being constant when approaching a step from the upper or lower adjacent terrace. Long-range transient mobility during Ni atom adsorption is ruled out. The correlation between adsorbed Ni atoms is also determined in kinetic Monte Carlo simulations based on a simple geometric adsorption model including the effects of thermal and transient adsorbate mobility. A comparison with highly resolved STM images in the middle of terraces leads to the conclusion that. at 130 K, adsorbing N atoms reach their final adsorption position with less than 0.5 additional transient hops along [1(1) over bar0$] on average. (C) 1997 Elsevier Science B.V.