Ultrathin films of Cu on ZnO(112̄0): growth and electronic structure

• Published in: Surface science 1994-04, Vol.307, p.591-596
• Main Authors: Møller, Preben J., Nerlov, Jesper
• Format: Article
• Language: English
• Subjects: Adsorbed layers and thin films; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Collective excitations (including plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electron and ion emission by liquids and solids; impact phenomena; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Photoemission and photoelectron spectra; Physics; Surface and interface electron states
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/0039-6028(94)90459-6

The growth of Cu on ZnO(112̄0) 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 0.28 e charge transfer, and a missing dangling bond of O, suggest bonding of the small Cu islands to substrate O, leading to fully coordinated O atoms and Cu(I).