IN-SITU ATOMIC-FORCE MICROSCOPY OF UNDERPOTENTIALLY AND OVERPOTENTIALLY DEPOSITED CADMIUM ON CU(111)

The structure of the monolayer of Cd atoms underpotentially deposited on a Cu(111) surface in perchlorate electrolyte was revealed by an atomic force microscope (AFM). A hexagonal adlattice with a 3.43 Angstrom lattice spacing was observed. This spacing, combined with its orientation relative to the underlying Cu(111), implies that the Cd lattice has a (4 x 4) structure. The slightly open lattice of the first Cd adlayer is possibly due to the retained partial charge of Cd adatoms. In the overpotential region, both the atomic structure and large scale morphology showed the formation of the Cd(0001) hcp crystalline structure. The crystalline domains were several hundred nanometers across and grow via a modified Stranski-Krastonov mechanism.