SCANNING PHOTOELECTRON MICROSCOPY OF A BIMETAL SI INTERFACE - AU COADSORBED ON AG/SI(111)/

The interaction of a (root 3 x root 3)R30 degrees-Ag/Si(111) interface , containing Ag agglomerates, with Au coadsorbed at 300 K has been stu died by means of scanning photoelectron microscopy and low-energy elec tron diffraction. The high lateral resolution provided by the microsco pe allowed detailed examination of the local composition and reactivit y of the coexisting surface phases. A substantial difference in the ev olution of the ordered two-dimensional (2D) and three-dimensional (3D) phases has been observed with increasing Au coverage. The spatially r esolved Ag 3d, Si 2p and Au 4f core-level spectra taken from the root 3-Ag phase and 3D agglomerates are used for investigation of the local compositional changes after Au deposition. The results revealed the c omplexity of the formation processes involved and showed the differenc es in the local reactivity of the two phases.