Effects of ordered islands on surface resistivity: Ni on Au(111).

The change in surface resistivity due to the formation of nickel islands on gold(111) was studied by measuring the resistance of a thin film of Au as a function of Ni coverage, θ. Previous studies showed that the Au(111) herringbone reconstruction provides a template for the periodic growth of ordered islands. Ni islands grow radially until θ ≈ 0.3 ML, after which subsequent Ni atoms contribute primarily to a second layer. Since Ni atoms on Au(111) grow in ordered nanoclusters, a nonlinear dependence of resistance on θ might be anticipated. Our results, however, show a linear dependence for Ni atoms in the first layer, as if they were independent point scatterers. Above θ ≈ 0.3 ML, there is little change in resistivity, which we attribute to Ni atoms in the second layer making no significant contribution to the resistivity. Although we did not directly image the islands, our results are consistent with the growth model and structures previously observed with scanning tunneling microscopy. Our results serve as an indirect probe of the growth kinetics of this system, as well as determining the contributions of Ni islands to the surface resistivity of the Au film.