Observing magnetic cobalt clusters underneath graphene on SiC(0001)

Full text: The behavior of Co nanoparticles (NPs) grown on graphene/SiC(0001) after oxygen exposure and heating in ultrahigh vacuum was investigated. The results of Photoelectron Spectroscopy (XPS) show that, as grown, the metal is on the surface of the graphene/SiC and suffers oxidation forming a single phase CoO when exposed to O₂, even at low doses (~ 10^-7 mbar). After heating in ultrahigh vacuum (UHV), there is a deoxidation of cobalt and intercalation between the graphene (G) and the buffer layer (BL), as indicated by XPS. Scanning Tunneling Microscopy (STM) images show that cobalt forms almost regular small 2D clusters between G and BL. Moreover, graphene acts as a barrier to oxidation, preserving the metallic and the magnetic character of the material even when re exposed to O₂ (~ 10^-5 mbar). The possibility to produce large-scale graphene capped ferromagnetic clusters (or films) assembled on a semiconductor substrate has enormous potential for technological applications, for example, in magnetic data storage media or other devices. (author)