PUB - Publikationen an der Universität Bielefeld

Iron oxide monolayers are grown on Ag(001) via reactive molecular beam epitaxy (metal deposition in oxygen atmosphere). The monolayer shows FeO stoichiometry as concluded from x-ray photoemission spectra. Both low energy electron diffraction as well as scanning tunneling microscopy demonstrate that the FeO layer has a quasi-hexagonal (111) structure although deposited on a surface with square symmetry. Compared to bulk values, the FeO(111) monolayer is unidirectionally expanded by 3.4% in <11-2> directions while bulk values are maintained in <1-10> directions. In <11-2> directions, this lattice mismatch between FeO(111) monolayer and Ag(001) causes a commensurate undulation of the FeO monolayer where 18 atomic rows of the FeO(111) monolayer match 17 atomic rows of the Ag(001) substrate. In <1-10> directions, however, the FeO(111) monolayer has an incommensurate structure.