Surface mobility of C60 on SiO2

Moalem, M.; Balooch, M.; Hamza, A. V.; Siekhaus, Wigbert J.; Olander, D.R.

doi:10.1063/1.466032

Cited by 19 publications

(8 citation statements)

References 11 publications

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“…Whereas detailed information about cluster properties in the gas phase and surface scattering of C 60 and its derivatives ,− has been obtained, little is known about the interaction process of clusters with solid surfaces at hyperthermal energies.…”

Section: Introductionmentioning

confidence: 99%

Cluster Impact Chemistry

Christen

Even

1998

J. Phys. Chem. A

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This paper addresses the interaction of molecular cluster ions with a solid surface in the kinetic energy range of 1-100 eV/molecule. We report experimental results on the energy acquisition by the cluster following its impact on the target, the size distribution and the time scale of cluster fragmentation, and first examples of chemical reactions induced by cluster impact. In particular we show that for a p-type diamond film and moderate collision energies the elasticity of the cluster-surface impact is surprisingly high: The intact cluster recoils with typically 75% of its collision energy. Once, however, the clusters have acquired sufficient internal energy they will shatter, mostly to monomers. In the case of protonated ammonia cluster ions this shattering of clusters upon surface impact is shown to be faster than 80 ps. It provides evidence that the technique of cluster impact allows an ultrafast energy redistribution within superheated cluster ions prior to their fragmentation. The feasibility of this fascinating new approach to femtosecond chemistry is demonstrated with impact-induced chemical reactions of iodomethane clusters to molecular iodine and of trifluoromethane clusters to molecular fluorine. The detected reaction yields are surprisingly high, even for the small cluster sizes investigated so far (n < 16).

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Section: Introductionmentioning

confidence: 99%

Cluster Impact Chemistry

Christen

Even

1998

J. Phys. Chem. A

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“…The growth mode on the BN surface clearly deviates from the simple layer-by-layer model and is better described by island growth. This interpretation implicitly assumes that the sticking coefficient of the molecules is close to one, which is a reasonable assumption judging from the few available experimental data 20 . Island growth occurs if the interaction between the adsorbate molecules is favoured over the substrate-adsorbate interaction and is often triggered by surface inhomogeneities and defects 21 .…”

Section: Resultsmentioning

confidence: 99%

Interaction of C₆₀ with Isoelectronic Surfaces: Graphite and Hexagonal Boron Nitride

2002

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In the present study we focus on the interaction of C 60 with sp 2 boron nitride (BN), a surface that is isoelectronic to graphite. The nanocrystalline BN substrate was deposited by mass selected ion beam and consists of an sp 2 surface layer, which covers a cubic-BN film. The interaction and electronic properties of the C 60 -BN system are observed by photoelectron spectroscopy in the xray (XPS) and ultraviolet regime (UPS). The experiment is initiated by sequential deposition of C 60 and the overlayer growth proceeds via island formation. In a second step the sample is annealed at a rate of 5-10 K/minute while simultaneously recording the UPS spectra. The majority of C 60 desorbs from the sp 2 BN surface at 493 K. The remaining C 60 (initially about 0.6 ML) is gradually removed with increasing temperature (up to 813 K) but never completely desorbed and presumably attached at surface imperfections or grain boundaries of the nanocrystalline material. No carbide formation, preferential interaction of C 60 with either element or a charge transfer are observed. The presence of C 60 induces an upward band bending and related peak shifts in the sp 2 BN surface layer and to a lesser extent in the underlying c-BN bulk. An upward band bending is likewise observed in the C 60 overlayer, and the Fermi level has therefore to be pinned by defects in the interface region. The layered structure of the BN film allows to probe the extension of the space charge layer in the BN film. INTRODUCTIONThe application of fullerene layers as functional surface layers and as part of multilayer structures has been reported a few times 1-5 , but information on the chemical and electronic structure of the interfaces and surface is necessary to further develop this type of materials. In the present study we chose to concentrate on the interaction of C 60 with the surface of a wide-bandgap semiconductor, namely sp 2 boron nitride (BN) that is isoelectronic to graphite 6-10 . The bandgap 11 exists because of the ionicity of the BN bond in contrast to the purely covalent bonds present in graphite, which is a semimetal. BN thin films, which are grown by ion-assisted methods, feature a layered structure introduced through the ion driven growth process 12-16 . The films consist of an sp 2 bonded surface layer and a cubic BN bulk, if grown in the appropriate deposition regime defined here by the substrate temperature and ion energy. The experiments described on the following pages deal with the growth of the C 60 layer and its subsequent desorption as a function of temperature. Photoelectron spectroscopy was used to monitor the changes in surface composition and study the adsorbate-surface interaction. The electronic properties of the interface can be deduced and the layered structure of the substrate afforded information on the extension of band bending into the film.

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“…5 The source chamber houses the reactant gas, or cluster source, and the mechanical chopper that operates at 20 Hz.…”

Section: Cs8 Production From Dissociation Of C60 By Scatteringmentioning

confidence: 99%

“…[2][3][4] Several studies have used photoemission and x-ray absorption to investigate initial stages of interface formation resulting from submonolayer molybdenum deposition on atomically clean and well-defined silicon surfaces in ultrahigh vacuum 0 but have failed to define the resulting interfacial order. [5][6][7][8] We find that two distinct, welldefined, ordered superstructures are associated with this interfacial material, but that their short-range character precludes detection by conventional surface diffraction probes, such as low-energy electron diffraction (LEED).…”

Surface mobility of C60 on SiO2

Cited by 19 publications

References 11 publications

Cluster Impact Chemistry

Cluster Impact Chemistry

Interaction of C₆₀ with Isoelectronic Surfaces: Graphite and Hexagonal Boron Nitride

Chemistry and Materials Science progress report, FY 1994. Revision 2

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Surface mobility of C60 on SiO2

Cited by 19 publications

References 11 publications

Cluster Impact Chemistry

Cluster Impact Chemistry

Interaction of C60 with Isoelectronic Surfaces: Graphite and Hexagonal Boron Nitride

Chemistry and Materials Science progress report, FY 1994. Revision 2

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Interaction of C₆₀ with Isoelectronic Surfaces: Graphite and Hexagonal Boron Nitride