The Fe ultrathin film on ZnO(000-1) surface: Growth, structure, and interaction

摘要

We report the electronic structure of the interface of the ultrafilm Fe film with the O-terminated ZnO(000-1) polar surface studied by synchrotron radiation photoemission. It was found that Fe grows in a Stranski-Krastanov mode. The turning point of the growth mode was at the Fe coverage of similar to 2 angstrom. At low coverage, about 1 ML (monolayer) of iron (ca. 1.5 angstrom) was oxidized by the terminative oxygen atoms on the ZnO(000-1) surface. Analysis of the valence band and the Fe3p photoemission spectra indicates that below 2 A coverage, only Fe2+ species could be detected at the Fe/ZnO interface, after that the formation of a metallic iron overlayer was observed. A sharp Fermi edge appeared at 5.1 angstrom coverage, indicating the formation of the bulk metallic Fe film. Furthermore, work function of the sample decreased to a minimum of 4.5 eV at 0.2 angstrom Fe, and then to 4.9 eV with the formation of a dipole layer at the interface.