ULTRATHIN FILMS OF CU ON ZNO(11(2)-OVER-BAR-0) - GROWTH AND ELECTRONIC-STRUCTURE

The growth of Cu on ZnO(1120BAR) and the related electronic-structure changes were investigated for deposits until 4 nm thickness. The growth at 300 K follows the monolayer-simultaneous-multilayer mode with a premonolayer break at 0.6 ML coverage. A surface-related plasmon excitation was observed by EELS at 6.7 eV. Core-level synchrotron-based photo-emission demonstrates a monotonic decrease in binding energy with increasing deposition thickness, approaching the bulk Cu value. Initial- and final-state considerations suggest that the shift is due to final-state effects, i.e. that Cu is present in the metallic state. By annealing 0.6 nm-deposited surfaces to 875 K, however, an observed shift in the initial 5.7 eV plasmon-energy with d(Cu) corresponding to a 0.28e charge transfer, and a missing dangling bond of O, suggest bonding of the small Cu islands to substrate 0, leading to fully coordinated 0 atoms and Cu(I).