From bilayer to trilayer Fe nanoislands onCu3Au(001)

Islands of 1\char21{}2 nm lateral size and double-layer height are formed when one monolayer (ML) of Fe is deposited on ${\mathrm{Cu}}_{3}\mathrm{Au}(001)$ at low temperature [M. Canepa et al., Phys. Rev. B 62, 13 121 (2000)]. We used the photoelectron diffraction technique to investigate the atomic structure and chemical composition of these nanoislands just after the deposition at 140 K and after annealing at 400 K. We show that only bilayer islands are formed at low temperature, without any surface segregation. After annealing, the Fe atoms are reaggregated to form mainly trilayer islands. Surface segregation is shown to be inhibited also after the annealing process. The implications for the film magnetic properties and the growth model are discussed.