Synchrotron radiation photoemission studies on Fe/ZnO(0001) interface

The growth, interfacial reaction, and electronic structure of Fe on ZnO(0001) surface were studied using synchrotron radiation photoemission spectroscopy(SRPES). It was found that Fe layer grows in a way similar to the Stranski-Krastanov mode at room temperature. After～2? Fe deposited on the surface, the growth mode changes from the layer-by-layer to a mixed mode. At low coverage, about one monolayer of iron (ca. 1.5?) is oxidized by the outer oxygen atoms on ZnO(0001) surface. Analysis of the valence band and the Fe3p photoemission spectra indicated that below 2? coverage, Fe2+ species exists at the Fe/ZnO interface, followed by the formation of a metallic iron overlayer. A sharp Fermi edge appears at 5.1? coverage, indicating the formation of the bulk metallic Fe film. Furthermore, work-function of the sample decreases to a minimum of 4.5eV at 0.2? Fe, then goes to 4.9eV with the formation of a dipole layer at the interface.