Paper NS+NC-FrM3
Fullerene Growth on N-adsorbed Cu(001) Nanopatterned Surfaces

Friday, October 24, 2008, 9:00 am, Room 311

Nitrogen (N)-adsorbed Cu(001)-c(2x2) nanopatterned surfaces are used as templates to guide the growth of low-dimensional C₆₀ molecular nanostructures. The detailed nucleation and growth behaviors are studied by in situ scanning tunneling microscopy(STM). At room temperature, on the 0.3 ML-N-covered surface, where 5x5 nm² patches of the c(2x2)-N surface are squarely arranged and bare Cu(001) surface. In other word, the bare Cu surface forms a nanogrid. Here ML is defined as the Cu atom density of the clean Cu(001) surface. During the initial stages of growth, C₆₀ molecules preferentially adsorb on the bare Cu regions on a partially N-covered grid surface. Subsequently a two-dimensional molecular nanomesh is formed after C₆₀ covers all the bare Cu regions. Further deposition leads to C₆₀ growth on the c(2x2)-N areas until the first molecular layer is completed. For N-saturated surface with trench structures, the <010> steps of these structures serve as initial anchoring sites for C₆₀ growth. From there, the growth proceeds two-dimensionally until a single C₆₀ layer is achieved due to island coalescence. In contrast, no nucleation site was observed when the <110> steps were predominant on the surface. At least up to 6 mono-molecule layer, the growth proceeds layer-by-layer i.e., the overlayer morphologies are directed by the underlying substrate pattern in both (partially and fully N-covered) surfaces. Four rotational domains are observed for the quasi-hexagonally close-packed C₆₀ overlayer with a nearest-neighbor C₆₀-C₆₀ distance of 1.02 nm. It is found that the interaction between C₆₀ and the c(2x2)-N surface is fairly weak, likely to be dominated by van der Waals forces, whereas the C₆₀-Cu interface is chemisorbed. Site-specific electronic effects between these two regions can be resolved by STM even for thick films.