Study of electronic structure of ultrathin Co films epitaxially grown on Cu(111) by angle-resolved photoemission spectroscopy

Electronic structure of Co films grown by molecular-beam epitaxy on Cu (111) surface was studied by Synchrotron Radiation angle-resolved Photoemission Spectroscopy. The peak intensity of the surface state at the Γ-bar point of Cu (111) surface Brillouin zone still can be distinguished even at the coverage of 2ML, which means that the growth mode is not the two-dimensional layer-by-layer mode. With changing the momentum along the direction of Γ-Λ-L of Brillouin zone of bulk copper by varying photon energy, we find that the most prominent peak of cobalt film both at the coverage of 1 ML and 2 ML disperses like that of the surface of Co(0001). With a fixed photon energy for the coverage of cobalt from 1 ML to 2 ML, the changes of cobalt energy band were obtained. It shows that the 3d-band modification do exist because of the interaction of substrate and film atoms at the initial stage of growth. Compared with theoretical calculations, we find that films show ferromagnetic characters even at 1 ML thickness, and they might grow as bilayer island at the initial period of growth