Substrate-adlayer interaction at the interface studied by high-resolution synchrotron radiation

Magnano, Elena; Vandré, S.; Cepek, Cinzia; Goldoni, A.; Laine, A D; Currò, Giuseppe; Santaniello, A.; Sancrotti, M.

doi:10.1016/s0039-6028(97)01547-1

Cited by 27 publications

(20 citation statements)

References 12 publications

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“…In contrast, STS probes just the actual top C atoms. 15 It can be understood that charge transfer to the LUMO has more weight on the C atoms closer to the interface than those on top. This explanation agrees with our resonance measurement.…”

Section: B Angle-resolved Valence-band Photoemissionmentioning

confidence: 99%

Photoemission, near-edge x-ray-absorption spectroscopy, and low-energy electron-diffraction study ofC60on Au(111) surfaces

et al. 2000

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The geometric and electronic structures of C 60 adsorption on Au͑111͒ surfaces have been studied by lowenergy electron diffraction ͑LEED͒, angle-resolved photoemission, and near-edge x-ray-absorption spectroscopy. An irreversible structural transition of the C 60 overlayer on Au͑111͒ was observed by LEED upon successive annealing. These structures are 38ϫ38 ''in phase,'' R14°and (2)ϫ2))R30°, with the latter phase predominating after annealing to 350°C. Valence-band photoemission spectra reveals a state right below the Fermi level for an annealed, ordered monolayer. This peak disperses across the Fermi energy that indicates the C 60 overlayer becomes metallic. Its intensity shows a resonance that primarily follows the behavior of highest occupied molecular orbitals, identified unambiguously as lowest unoccupied molecular orbitals ͑LUMO's͒ filled by charge transfer from the substrate. An asymmetric distribution of LUMO charge is observed. The thermal-desorption energy of the monolayer is estimated from annealing experiments to be 1.9 eV, which is 0.5 eV larger than the desorption energy from multilayers. Comparison with available spectroscopic data indicates that interaction of C 60 with Au͑111͒ is slightly weaker than with Au͑110͒, and much weaker than with Cu͑111͒. The amount of charge transfer estimated from photoemission is 0.8 electrons per C 60 molecule on Au͑111͒, compared to 1.6 electrons on Cu͑111͒. We argue that charge transfer is determined by the bulk sp density of states at the Fermi energy scaled by the size of the C 60 molecule, and also modified by a clean surface electronic structure, and that charge transfer is the dominant interaction in these systems.

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Section: B Angle-resolved Valence-band Photoemissionmentioning

confidence: 99%

Photoemission, near-edge x-ray-absorption spectroscopy, and low-energy electron-diffraction study ofC60on Au(111) surfaces

et al. 2000

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“…26,27 In general, C 60 chemisorption at metal and semiconductor surfaces induces a chemical shift towards lower BE and an asymmetric line shape in the C 1s emission. 2,17,28,29 When the C 60 -substrate bond is primarily covalent, for example at Al and Pt surfaces, the value of the C 1s chemical shift is of the same order of magnitude of systems in which charge transfer takes place. 2,30 However, the C 1s line-shape asymmetry is less pronounced in the former case.…”

Section: Annealed Samplementioning

confidence: 99%

“…On the contrary, valence band photoemission data clearly show that, in that system, charge transfer from the Ag atoms to the C 60 molecules takes place. 17 Valence-band photoemission spectroscopy is the direct probe of the density of states at the FL, so it can be used to find out the exact charge state of C 60 molecules adsorbed onto the Si͑111͒ surface. However there are few valenceband photoemission data as a function of coverage 18,10 and no photoemission data as a function of annealing temperature available on this system, so far.…”

Section: Introductionmentioning

confidence: 99%

Photoemission study ofC60/Si(111)adsorption as a function of coverage and annealing temperature

et al. 1999

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We report core-level and valence-band ͑VB͒ photoemission data of C 60 molecules adsorbed at room temperature ͑RT͒ on Si͑111͒. The measurements have been carried out as a function of C 60 coverage ͓from 0.20 monolayer ͑ML͒ up to 2.2 ML͔ and annealing temperature ͑from RT up to 1300 K͒. From the VB spectra no increasing of the Fermi-level photoemission intensity has been observed for all the coverages investigated thereby indicating that no charge transfer occurs at the interface. Remarkable changes take place on the 1-ML spectrum as the annealing temperature is increased up to the disruption of the C 60 cages and the following formation of SiC. ͓S0163-1829͑99͒02623-5͔ INTRODUCTIONC 60 epitaxial growth on different metal and semiconductor substrates has attracted much interest in the last few years. Such systems can be used both as templates for the deposition of single-crystalline C 60 -thick films and to study the interaction between C 60 molecules and different elements.Solid C 60 is a molecular solid and molecules interact each other mainly through van der Waals forces. 1 The character of the bond between fullerene molecules and different substrates varies widely depending on many different factors. Strong charge transfer from metal atoms to the C 60 molecules has been observed in C 60 absorption on noble metals, Ni, etc., 2 while, for example, on Pt͑111͒ and Al͑110͒ the interaction has primarily covalent character with negligible charge transfer. 3,4 Recently, an intense experimental work has been done to study the interaction between C 60 and different Si surfaces. C 60 interaction with Si surfaces is strong: fullerene does not desorb from silicon surfaces even at 1300 K and fragment to form SiC film at temperatures above 1000 K. [5][6][7][8] One reason of this kind of research is to find the right way to use fullerenes as precursors to grow well-ordered SiC films for electronic devices with improved quality with respect to more standard methods. 9 The C 60 /Si͑111͒ system, though widely investigated is still not well understood and a series of controversies is open. The character of the bond has been found to depend on the C 60 coverage and on the annealing or growing temperature. 10,11 Scanning tunneling microscopy ͑STM͒ and Highresolution electron-energy-loss spectroscopy ͑HREELS͒ studies suggest that C 60 bond on Si(111)-(7ϫ7) surfaces is characterized by charge transfer from Si dangling bonds to C 60 when the molecules are adsorbed on the surface at RT and up to an annealing temperature of Ϸ870 K, while the bond is primarily covalent at higher annealing temperatures. 7,12-14 HREELS measurements, from the energy shift of the four dipole active modes T 1u and same H g modes, give an estimation of the charge transferred up to 4 Ϯ1 electrons/molecule. 6,13 However, these assignments have to be analyzed carefully. Actually, the energy shift of the vibrational modes depends not only on the charge state of the C 60 molecules, but also on different physical parameters, 15 such as, for example, on the structural ...

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] C 60 and C 70 act as excellent acceptors because of their low multiply degenerate LUMO states. 17 With electron donors such as aromatic amines, 6 fullerenes can form charge-transfer (CT) complexes in the ground state.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Electron Transfer from N,N-Dimethylaniline to Pyrrolidinofullerenes (C₆₀(C₃H₆N)R): Emphasized Substituent Effects with Solvent Polarity Change

et al. 1998

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Photoinduced electron-transfer reactions of pyrrolidinofullerenes {C 60 (C 3 H 6 N)R; R ) H (1), C 6 H 4 NO 2 -p (2), C 6 H 4 CHO-p (3), C 6 H 5 (4), C 6 H 4 OMe-p (5), and C 6 H 4 NMe 2 -p (6)} with N,N-dimethylaniline have been systematically studied by means of nanosecond laser photolysis. From the direct observation of the rises of the anion radicals accompanied by the decays of the triplet states of the fullerenes, the rate constants of electron-transfer reactions (k ET ) via the triplet states were evaluated in polar solvents. Although the k ET values are considerably decreased by the substituents as compared with that of pristine C 60 , the electron is accepted by the C 60 moiety. Among the derivatives, the k ET values of 2 and 3 with electron-withdrawing groups are larger than those of 4 and 1. In less polar solvent, such a substituent effect becomes prominent with decrease in the k ET values, which is in accord with the reactivity-selectivity principle. This behavior can be explained by the Rehm-Weller relation and/or Marcus equation in consideration of the solvent polarity change. Backelectron-transfer rate constants in less polar solvent are larger than those in polar solvent, which is related to the desolvation process and/or loose ion pair formation.

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Substrate-adlayer interaction at the interface studied by high-resolution synchrotron radiation

Cited by 27 publications

References 12 publications

Photoemission, near-edge x-ray-absorption spectroscopy, and low-energy electron-diffraction study ofC60on Au(111) surfaces

Photoemission, near-edge x-ray-absorption spectroscopy, and low-energy electron-diffraction study ofC60on Au(111) surfaces

Photoemission study ofC60/Si(111)adsorption as a function of coverage and annealing temperature

Photoinduced Electron Transfer from N,N-Dimethylaniline to Pyrrolidinofullerenes (C₆₀(C₃H₆N)R): Emphasized Substituent Effects with Solvent Polarity Change

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Substrate-adlayer interaction at the interface studied by high-resolution synchrotron radiation

Cited by 27 publications

References 12 publications

Photoemission, near-edge x-ray-absorption spectroscopy, and low-energy electron-diffraction study ofC60on Au(111) surfaces

Photoemission, near-edge x-ray-absorption spectroscopy, and low-energy electron-diffraction study ofC60on Au(111) surfaces

Photoemission study ofC60/Si(111)adsorption as a function of coverage and annealing temperature

Photoinduced Electron Transfer from N,N-Dimethylaniline to Pyrrolidinofullerenes (C60(C3H6N)R): Emphasized Substituent Effects with Solvent Polarity Change

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Photoinduced Electron Transfer from N,N-Dimethylaniline to Pyrrolidinofullerenes (C₆₀(C₃H₆N)R): Emphasized Substituent Effects with Solvent Polarity Change