ELECTROCHEMICAL DEPOSITION OF COPPER ON A GOLD ELECTRODE IN SULFURIC-ACID - RESOLUTION OF THE INTERFACIAL STRUCTURE

The structure of electrochemically deposited submonolayer Cu on Au(111 ) in sulfuric acid has been extensively investigated but is still poor ly known. We report an x-ray scattering determination of this structur e that explains existing data. The Cu adatoms form a honeycomb lattice and are adsorbed on threefold hollow sites, while sulfate anions occu py the honeycomb centers. Three oxygens of each sulfate bond to Cu ato ms. This stabilizes the structure and illustrates that anion effects c an be important in electrodeposited structures. Our results indicate t hat previous scanning tunneling and atomic force microscopy measuremen ts imaged the sulfate molecules not the Cu atoms.