ATOMIC-STRUCTURE OF ORDERED COPPER ADLAYERS ON SINGLE-CRYSTALLINE GOLD ELECTRODES

We have investigated submonolayer electrodeposits of copper on the three low-index planes of gold in situ by STM. The atomic structure of the clean electrode surfaces and of different ordered Cu adsorbate layers were resolved. For submonolayer Cu coverages on Au(111) and Au(100), deposited under potential control from sulfuric acid solutions, various ordered structures were observed, where the Cu adatoms are arranged in hexagonal or quasihexagonal lattices. The larger Cu-Cu distances in these structures, as compared to the pseudomorphic (1 x 1) Cu islands formed in vacuum deposits even at low coverages, demonstrate the structure determining role of the coadsorbed anions. For Cu deposition on Au(110) only a (1 x 1) Cu adlayer was observed. These results are in good agreement with recent ex situ LEED data.