Structural and electronic characterisation of Cu/Au(111) near-surface alloys

Geometrical structure and electronic characteristics of ultrathin metallic films of one metal on another are strongly influenced by factors such as lattice mismatch and formation of near-surface alloys. Doped systems often show modified chemical-physical properties which may be amenable to different reactivity routes. Copper-gold surface alloys have received the attention of several studies, only a few of which have been undertaken in an UHV environment, using surface sensitive techniques. In this contribution, systems produced upon room temperature deposition of copper on the (22×√3)-Au(111) surface, at various copper loadings and annealed to different temperatures, are investigated using scanning tunnelling microscopy and synchrotron radiation based techniques (X-ray photoelectron diffraction, photoemission), with comparison with some theoretical modelling. Overall the fcc lattice is essentially maintained on preparation. Upon thermal treatments structural and compositional changes, in favour of alloyed structures with tetragonal packing, are seen.