The C60/Au(1Â 1Â 1) interface at room temperature: A scanning tunnelling microscopy study

The interface between adsorbed C60 molecules and the (1 1 1) surface of gold at room temperature has been studied with the scanning tunnelling microscopy (STM). The first monolayer of C60 on Au(1 1 1) is known to exist in several phases: in phase, 23×23R30°, and R14°, depending on the direction of the close-packed C60 molecules in relation to the close-packing direction of the gold atoms. For the in-phase C60 overlayer where the close-packing direction of the C60 molecules is aligned with that of the gold atoms, we find that the 22×3 reconstruction of the underlying Au(1 1 1) surface remains largely unchanged. For the 23×23R30° phase, the surface reconstruction is also preserved to a great extent if the molecular layer sits on a region consisting of small 22×3 domains. On a larger domain, the 23×23R30° structure is found to lift the surface reconstruction of Au(1 1 1). The R14° structure is observed for the first time in STM and a structural model consistent with findings from both STM and LEED is presented. A fairly regular pattern of atomic re-arrangement with a quasi-period of ∼6 nm is found in regions of the Au(1 1 1) surface underneath the R14° C60 layer.