Adsorption and electronic structure of single C60F18 molecule on Si(111)-7×7 surface (original) (raw)
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Surface Science, 2009
We have carried out a combined X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy(UPS), and scanning tunnelling microscopy (STM) study of the C 60 -Si(1 1 1) interaction where the XPS/UPS spectrometer and STM are integrated on a single UHV system. This enables a direct comparison of the XPS/UPS spectra with the STM data and eliminates any uncertainty in C 60 coverage measurements. X-ray standing wave measurements and density functional theory calculations have been used to support and interpret the results of the XPS/UPS/STM experiments. Our data conclusively rule out models of C 60 adsorption which involve a mixture of physisorbed and chemisorbed molecules [K. Sakamoto, et al., Phys. Rev. B 60 (1999) 2579. Instead, we find that all molecules, up to 1 monolayer coverage, bond to the surface via Si-C bonds which are predominantly of covalent character.
Decomposition of C60 molecules on Si(111) surface
Surface Science, 1997
We have investigated the adsorption and decomposition of C6o molecules on a Si(111) surface at elevated temperatures by using a molecular-dynamics computer simulation. The potential energy function used in the calculations includes both two-and threebody interactions, which are represented by Lennord-Jones and Axilrod-Teller potentials, respectively. The abrupt decomposition of C6o molecules on a Si(111) surface is obtained at 910 K.
Physical review. B, Condensed matter, 1996
A self-consistent real-space scheme for calculating the van der Waals interaction energy between a fullerene molecule and substrate with atomic surface corrugation is presented. The interaction of a single fullerene molecule with various substrates is then considered, to determine the optimum binding energy, plus the rotational and translational diffusion barriers. The van der Waals energy is calculated using linear response theory to evaluate the dipole-dipole interactions between the molecule and the substrate. The method is extended beyond the treatment of the substrate as a continuous dielectric medium to a discrete stratified substrate including the atomic nature of the surface. For C 60 on graphite the fullerene is always preferentially oriented so as to present a six-membered ring to the surface. The optimum binding energy is found to be 0.96 eV, with the molecule positioned so as to continue the natural stacking of the hexagonal planes. For C 60 on NaCl͑001͒ the most stable position is found to be above a sodium cation with a five-membered ring oriented towards the surface, and a binding energy of 0.42 eV. Unlike the situation for graphite, though, the orientation of the molecule changes with adsorption site. The energy barrier for rotation of an isolated C 60 molecule is of the order of 0.03 eV on both surfaces. Lüthi et al. ͓Science 266, 1979 ͑1994͔͒ recently reported that islands of C 60 deposited on NaCl͑001͒ could be moved by the action of the tip of a scanning force microscope, whereas for C 60 on graphite, collective motion of the islands could not be achieved, instead the islands were disrupted by the tip. These results can be explained in terms of the relative strengths of the C 60 -C 60 , C 60 -graphite, and C 60 -NaCl interactions and the reduction of the rotational barriers of the interface molecules due to collective effects.
Survey of structural and electronic properties of C60 on close-packed metal surfaces
Journal of Materials Science, 2012
The adsorption of buckminsterfullerene (C 60) on metal surfaces has been investigated extensively for its unique geometric and electronic properties. The twodimensional systems formed on surfaces allow studying in detail the interplay between bonding and electronic structures. Recent studies reveal that C 60 adsorption induces reconstruction of even the less-reactive close-packed metal surfaces. First-principles computations enable access to this important issue by providing not only detailed atomic structure but also electronic properties of the substrateadsorbate interaction, which can be compared with various experimental techniques to determine and understand the interface structures. This review discusses in detail the ordered phases of C 60 monolayers on metal surfaces and the surface reconstruction induced by C 60 adsorption, with an emphasis on the different types of reconstruction resulting on close-packed metal surfaces. We show that the symmetry matching between C 60 molecules and metal surfaces determines the local adsorption configurations, while the size matching between C 60 molecules and the metal surface lattice determines the supercell sizes and shapes; importantly and uniquely for C 60 , the number of surface metal atoms within one supercell determines the different types of reconstruction that can occur. The atomic structure at the molecule-metal interface is of crucial importance for the monolayer's electronic and transport properties: these will also be discussed for the well-defined adsorption structures, especially from the perspective of tuning the electronic structure via C 60-metal interface reconstruction and via relative inter-C 60 orientations.
Electronic structure and bonding of C60 to metals
Synthetic Metals, 1993
The electron distribution and orbital interactions of C60 with metals coordinated at different sites on the outside of the fuUerene are evaluated with the Fenske-Hall molecular orbital method. The characters and nodal properties of the frontier orbitals of C60 are first evaluated in terms of basis transformations to the C2 units that join the pentagons and to the C5 units of the pentagons in the Cso molecule. The highest occupied molecular orbital (HOMO, hu symmetry) of C60 is largely ~r bonding between the carbon atom pairs that join adjacent pentagons. The lowest unoccupied molecular orbital (LUMO, tlu symmetry) is predominantly ~-antibonding between these carbon atom pairs. These orbital characters and energies are well situated for synergistic bonding of a metal atom to the carbon-caxbon pair between the pentagons, in which the HOMO of C60 donates a electron density to the metal, and the LUMO of C60 accepts ~r electron density from the metal. The electron donation and acceptance between the individual molecular orbitals of the C60 molecule and the orbitals of a metal at different possible bonding sites of C~o are probed with a Ag ÷ ion. It is found that the bonding is favored at the site between the pentagons and that many different orbitals of C~o are involved in the interaction. The net bonding of Ag ÷ to C60 is weaker than to ethylene. Calculations are also carried out on the organometallic complexes C60Pt(PHa)2 and (C2H4)Pt(PH3)2. The net bonding of ethylene and C80 to platinum is found to be very similar in these cases. A significant difference in this case is that the net negative charge on C60 is more delocalized in the carbon cluster in contrast to the localized charge on ethylene.
Si–C60 bond in cluster-based materials
Surface Science, 2003
We investigate the binding of Si and C 60 theoretically (by ab initio calculations within the local-density approximation to the density functional theory) and confront the predictions to experimental X-ray absorption results from Si-C 60 films synthesized by the cluster beam deposition technique. The calculations predict that Si preferentially binds to hexagon-hexagon edges. The geometry with Si bound to a pentagonal face is metastable. The binding energy is in each case higher than the typical van der Waals binding energy. Extended X-ray absorption fine structure measurements reveal that in C 60 -Si obtained from (C 60 ) m Si n clusters deposition, Si is bound to the pentagonal face of two C 60 molecules. Both theoretical and experimental investigations go to show that the polymerisation of C 60 -Si clusters is possible, leading to nanostructured C 60 -based materials with high binding energy.
Electronic structure of monolayer C60 on Si(100)2 × 1 surface
Surface Science, 1996
The band structure of monolayer C6o on Si(100)2 × 1 surface is calculated by DV-Xa-LCAO method and compared with the energy bands of Si substrate and C60 isolated monolayer. The results indicate a significant hybridization between C6o and the substrate surface showing the metallic character to be consistent with experiment. According to Mulliken charge analysis, the electron is transferred from Si substrate to C6o, and the charge of a C6o molecule is about-0.66.
Strong Bonding of Single C60 Molecules to (1 × 2)-Pt(110): an STM/DFT Investigation
Journal of Physical Chemistry C, 2007
The interaction of single C 60 molecules with the (1 × 2)-Pt(110) surface has been studied by scanning tunneling microscopy and density functional theory (DFT) calculations on slab models. Molecules are observed to be frozen at room temperature and are found to be almost exclusively in the same configuration. Extensive DFT calculations show that this configuration is the global energy minimum, suggesting that adsorbed molecules have enough rototranslational freedom to escape from the numerous local minima. The adsorption energy (3.81 eV) is the strongest ever found for C 60 , and it is roughly proportional to the number of the Pt and C atoms at contact distance. Analysis of DFT results shows that the surface-adsorbate interaction is covalent in nature. A minority fraction of C 60 molecules appear to be adsorbed on surface defects. A careful investigation of their registry and height with respect to the regularly adsorbed units leads to an indirect structural characterization of the nanopits which act as their adsorption sites.
Structure of C 60 layers on the Si ( 111 ) − 3 × 3 − Ag surface
Physical Review B, 1999
The structure of a monolayer of C 60 molecules adsorbed on the Si(111)-)ϫ)-Ag surface has been investigated by scanning tunneling microscopy ͑STM͒ at room temperature and at low temperature ͑60 K͒. The C 60 molecules are arranged in a ͱ21ϫͱ21(RϮ10.9°) double domain structure and also in a 3) ϫ3)(R30°) structure in part. The intramolecular structures are observed only for the molecules adsorbed at step edges at room temperature, because the rotation of C 60 molecules is suppressed due to the strong interaction with the substrate at step edges, while the molecules adsorbed on terraces do not exhibit the internal structure because of their fast rotation. On the other hand, the internal structure of C 60 is resolved for every molecule adsorbed on terraces at low temperature because the rotation of C 60 is suppressed as in the C 60 bulk crystal. The orientations of the individual C 60 seem to be determined by the directions of underlying Si and Ag trimers of the)ϫ)-Ag surface. ͓S0163-1829͑99͒03140-9͔