Low-Temperature Growth of C-60 Monolayers on Au(111): Island Orientation Control with Site-Selective Nucleation

We report a low-temperature scanning tunnelling microscopy (STM) study of the adsorption of C-60 molecules on the (111) surface of gold At 46 K, occupation of the elbow sites on Au(111) by individual C-60 molecules as well as small molecular clusters is observed at a coverage of 0 01 monolayer (ML) The molecular clusters are mostly found in the FCC regions adjacent to the bulged elbows while most of the pinched elbows remain decorated by single molecules At a higher coverage of 0 05 ML the islands nucleated at the bulged elbow sites increase in size, and at the same time, a delayed nucleation process starts around the pinched elbow sites. The C-60 islands show different azimuthal orientations similar to that found for larger islands formed at room temperature The islands in the FCC region near the bulged elbows grow with coverage, but are confined by the discommensuration lines At 180-190 K. C-60 molecules are found to preferentially attach to the bulged elbow site and island nucleation occurs exclusively on the bulged site This single-site-nucleation phenomenon leads to the formation of C-60 islands with a single orientation