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The structure of C6o molecules adsorbed on the Cu(l 1 l)-(l x 1) surface has been investigated by scanning tunneling microscopy (STM). Bias voltage dependent STM images of individual C6o molecules in the monolayer film showed unique intramolecular structures with a threefold symmetry. The observed images agree well with those calculated using the local density approximation. With charge transfer from the Cu(l 11) substrate to the monolayer film, the €50 molecule ratchets to threefold hollow sites. PACS numbers: 68.35.Bs, 61.16.Ch, 61.46,+w, 68.65.+g The investigation on carbon fullerenes discovered by Kroto et al. [1] has been a growing exciting field, since Kratschmer et al. [2] succeeded in the extraction and purification of C60 and other fullerenes. Discovery of superconductivity by Hebard et al. [3] in a K-doped fullerene sample, K3C60, added further excitement with promising practical applications [4]. Scanning tunneling microscopy (STM) has been successfully used to reveal the geometric and electronic structure of the fullerenes with molecular resolution. The nucleation and growth of C60 film and its structure on various substrates, such as Au(100) [5], (111) and (110) [6], Ag(lll) [7], highly oriented pyrolytic graphite (0001) [8], GaAs(llO) [9], and Si(l 11) [10], and (100) [11] have been major interests in STM studies. Investigations on other fullerene films, such as C70 [12], Cu [13], and SCC74/SC2C74 [14], and Sc 2 C 8 4 [15] on the Si (100)-(2x 1) surface have been reported using the FI-STM (field ion scanning tunneling microscope), elucidating the growth kinetics and geometric structures.The Cu(l 11) surface is one of the ideal surfaces for the growth of C60 film similar to the bulk [16], since the lattice mismatch is small (2%) between the nearest neighbor (nn) distance (10.0 A) of the bulk Ceo crystal and 4 times of the Cu-Cu nn distance (10.2 A). A recent study of C 60 adsorption on the Cu(lll), (110), and (100) surfaces using x-ray photoemission spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS) and other techniques [17] concluded the following: (1) The Cu substrate donates charge to the lowest unoccupied molecular orbital (LUMO) band of C60 as K does in K x C6o films and (2) single-domain epitaxy with a (4x4) superlattice and successive layer-bylayer growth can be achieved on the Cu(l 11) surface.In this Letter, we report the intramolecular structure of C60 molecules on the Cudll)-(lxl) surface using the FI-STM [18]. C60 molecules ratchet to hollow sites and are ordered due to the substrate-C6o and C60-C60 interactions. Observed intramolecular structure with a unique threefold symmetry agrees well with the charge density around the molecule calculated using the local density approximation (LDA). It was confirmed in the STM images and calculated charge density that excess charge on the molecule is present on top of the pentagonal rings.The experimental details of the extraction and purification of high-purity C60 powder (purity of 99.95%, the rest being C70) [19], a...

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Adsorption of C60 molecules on the Si(111)7×7 surface was investigated using a field ion-scanning tunneling microscope. C60 adsorbs preferentially on the faulted half of the 7×7 unit and stays still without rotation at room temperature, implying the reasonably strong interaction with the Si substrate. The internal structure of individual C60 molecules can be understood if we assume that the C=C double bonds are imaged brightly. Unlike the case of its adsorption on the Si(100)2×1 surface, C60 do not form ordered mono/multi layers on the 7×7 surface.

Field ion-scanning tunneling microscopy was employed to study the monolayer and multilayer adsorption behaviors of the C60 fullerene on the Si(100)2×1 surface. The C60 molecules reside stably in the trough at room temperature without rotation, encompassing the 8 neighbouring dimer-forming surface Si atoms with the nearest neighbour distance of 12 Å. For the first and second layers, only local ordering of square and quasi-hexagonal patterns was observed. The orderly Stranski-Krastanov mode island formation with the hexagonal packing was observed above the third layer with its lattice constant of 10.4 Å.

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