FULLERENES ON METAL AND SEMICONDUCTOR SURFACES: SCANNING TUNNELING MICROSCOPY STUDIES

In this paper, we review our recent scanning tunnelling microscopy studies of fullerenes C 60 and C 70. We focus our work on adsorption and reaction of these fullerenes on Si(111)7×7 and Si (100)2×1 semiconductor surfaces, as well as on Cu (111)1×1 and Ag (111)1×1 noble metal surfaces. By using STM, the adsorption geometry and reconstructions of fullerenes are directly observed on these surfaces, and the intramolecular structures are revealed in high resolution STM images. It is found that fullerenes are strongly bonded to the Si(100) and Si(111) surfaces so that the free rotation of C 60 and C 70 in their bulk phases is stopped. Local orderings with c(3×4) and c(4×4) reconstructions are observed for the first layer of C60 on the Si(100) surface. Well-ordered crystalline multilayer films can be formed on the Si(100) surface. The intramolecular structures observed for C 60 on the Si(100) surface are interpreted based on the local charge distribution on the molecule, in good agreement with a recent theoretical calculation. The Cu (111)1×1 and Ag (111)1×1 surfaces are found to be good substrates for ordered C60 and C 70 film growth. While the interaction of fullerenes with Ag(111) surface is weaker than that on the Cu(111) surface, rotation of C 60 in bulk phase is stopped on both surfaces. Well-ordered commensurate reconstructions are observed for C 60 and C 70 on both surfaces. Bias-voltage-dependent intramolecular structures are observed for the first layer of both C60 and C 70, which reveal the local charge density distribution on these molecules. The results are in good agreement with a recent theoretical calculation. The interesting behavior of the C 60/ C 70 mixture on Cu(111) surface is also reported.