Surface superstructure formation, electronic structure modification and magnetic stability of Co films on oxygen-rich Cu(0 0 1): confirmation of oxygen-surfactant effect

Low energy electron diffraction, core level photoemission spectroscopy and magnetic dichroism have been applied to study Co films grown on oxygen-rich Cu(0 0 1) surfaces. The surface superstructure, electronic structure, chemical phase and magnetic stability in Co films were investigated. It was found that the initial oxygen was mostly segregated on top of the deposited Co films and promoted formation of a well-ordered c(2×2) phase. Besides, the correlation-induced satellite structure in Co2p photoemission spectra for a 1 ML (monolayer) Co film on O/Cu was found to be stronger than that for a 1 ML Co film on Cu. It is predicted that the growth conditions in both cases alter the Co d–d interaction and adatom (Co3d)-substrate (Cu4s) hybridization, and hence the observed satellite intensities. Additionally, a 5 ML film on oxygen-rich Cu(0 0 1) showed a magnetically stable phase at room temperature with in-plane magnetization. This is proof of an oxygen surfactant effect for Co epitaxial growth on Cu(0 0 1).