Confined Ni film on a Pd/Si(111)-(√3 x √3)R30° surface:: spatially resolved XPS study of the surface reactions

We used scanning photoelectron microscopy with lateral resolution of 0.15 mu m to study the interactions of a (root 3 x root 3)R30 degrees-Pd/Si(111) surface with a rectangular 2 ML Ni film deposited at 300 K and after stepwise annealing to 1120 K. The evolution in the surface composition and electronic structure inside, outside and across the edge of the Ni film was examined by mapping the lateral changes of the valence band, Ni 3p. Si 2p and Pd 3d core levels. The results showed that up to 780 K the changes at both interfaces are determined by temperature-induced interactions leading to formation of new silicide phases. Edge effects at the forefront of the patch are identified and the composition of microscopic three-dimensional silicide islands formed after annealing to 1120 K is determined as well. (C) 2000 Elsevier Science B.V. All rights reserved.