ELECTROCHEMICAL SCANNING-TUNNELING-MICROSCOPY OF SILVER ADLAYERS ON IODINE-COATED AU(111) IN PERCHLORIC-ACID SOLUTION

The underpotential deposition (UPD) of Ag on an iodine-coated Au(111) surface has been examined in perchloric acid solution by electrochemic al scanning tunneling microscopy (STM). A (5 x square-root 3) structur e for the iodine adlayer was observed over wide terraces before initia ting the UPD of Ag. Two different structures of (3 x 3) were found for the first UPD layer of Ag. It was expected by STM measurements that t he iodine exchanges and exists above the layer of bulk deposited Ag. T he structure of iodine on bulk deposited Ag is a simple (square-root 3 x 3 square-root)R30-degrees with no regularly arrayed phase boundarie s.