Reaction of C60 with metals: W

Wertheim, G. K.; Buchanan, D. N. E.

doi:10.1016/0038-1098(93)90386-2

Cited by 59 publications

(27 citation statements)

References 12 publications

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“…The fullerenes С 60 deposition on the crystals of noble metals, refractory and some non-metals as Ir, Mo, Ni, Re, W, Si etc. have been investigated [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. It has been found experimentally that molecules С 60 hold their shape and structure up to the certain temperature, which value depends on the chemical nature of substrate.…”

Section: Introductionmentioning

confidence: 99%

The Statistical Theory of Monomolecular Fullerene Film Formation on the Crystal Surface

Zaginaichenko

Матысина

Schur

et al. 2013

Comput Thermal Scien

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The theoretical study of fullerene film production on the crystal faces of (100) type of crystals with sc, bcc, fcc lattices is the subject of this paper. The calculation of equilibrium concentration of fullerenes С 60 , С 70 and its dependence on temperature has been carried out. Investigation of processes adsorption-desorption of fullerenes on the crystal surface and possible special features of these processes has been discussed. The developed statistical theory of the process of fullerenes deposition on the metallic substrate permits to explain and justify the possibility of manifestation of these processes and reveal that passing of each process is defined to a large extent by the character and degree of interaction between fullerenes and atoms of metallic substrate.

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Section: Introductionmentioning

confidence: 99%

The Statistical Theory of Monomolecular Fullerene Film Formation on the Crystal Surface

Zaginaichenko

Матысина

Schur

et al. 2013

Comput Thermal Scien

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“…This intercalation stands in apparent contrast to an XPS study of C 60 deposited onto W(100) and heated where intercalation was not observed and a phenomenological model was introduced to predict whether intercalation into C 60 would occur for any metal based on the metal's cohesive energy. 38 This model successfully predicted the intercalation behavior of nearly all metals for which data was available, and strongly indicated W would not intercalate. This prediction is certainly true when the W atoms must first escape the surface of a finite amount of W before intercalating, but in the current investigation, it is extremely likely that the W atoms intercalate before interacting with other W atoms on the surface.…”

Section: Section 33: Discussionmentioning

confidence: 84%

“…38,83 Why the larger W clusters do not interact with adjacent C 60 in any obvious way is more of an enigma as their situation is analogous to the C 60 on top of single crystal surfaces which have in the past shown very strong interaction in X-ray Photoemission and Auger Electron Spectroscopy studies. 38,83 It is not at all clear why the interaction should be significantly less for clusters when compared to a single crystal. The fact that single atoms or very small clusters of only a few atoms of W would interact more strongly with C 60 makes intuitive sense as isolated W atoms will be looking for bonding situations to fill their valence orbitals.…”

Section: Section 33: Discussionmentioning

confidence: 99%

“…With a more accurate determination of the minimum temperature to form the nanospheres, even narrower size distributions might be achieved since excess heating seems to cause the nanospheres to slowly dissolve into the W film and it is unknown whether the nanospheres might form below 400˚C, although XPS of C 60 annealed on W rules out formation at temperatures below 225˚C. 38 To unravel why the nanospheres form in the presence of W, a model is presented for their evolution. In some ways, the evolution of the nanospheres can be compared to previously observed reconstruction of metal surfaces in the presence of C 60 .…”

Section: Section 47 Discussionmentioning

confidence: 99%

“…[38][39][40][41][42] In all cases, the effect has been attributed to electron donation from the metal to the Lowest Unoccupied Molecular Orbital (LUMO) of the C 60 molecule along with image charge screening effects. This explanation has been corroborated to some degree by ab initio calculations.…”

Section: List Of Tablesmentioning

confidence: 99%

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Synthesis and Oxidation of non-Stoichiometric Tungsten Carbide Studied by Scanning Tunneling Microscopy/Spectroscopy

McClimon¹

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Tungsten Carbide (WC) is a promising catalyst material for applications where cost is paramount, such as microbial fuel cells. Unfortunately, oxidation depresses performance which is a critical problem with respect to long term performance. In this work, non-stoichiometric carbon-rich WC is investigated to infer whether an excess of carbon near the surface can reduce or be utilized to repair oxidation of the active catalytic surface. The carbides are synthesized via a physical vapor deposition of metallic tungsten and C 60 , which allows fine control over the composition of the resulting film. The films are studied predominantly via Scanning Tunneling Microscopy/Spectroscopy (STM/STS).Prior to synthesizing the carbide, a number of RT depositions are performed onto graphite substrates to understand the interactions between the C 60 and W prior to thermallyinduced destruction of the C 60 cage and formation of the carbides. These experiments showed a surprising lack of interaction between small W clusters and adjacent C 60 molecules. This result contrasts with literature of analogous experiments showing significant charge transfer from W to C 60 and strong interaction as a result. For W deposited on top of C 60 layers, it is found that isolated W atoms diffuse easily into the interstices of the C 60 matrix and that for high coverages, interactions between the W and C 60 induce a significant reduction in the C 60 bandgap. These interactions can also stabilize very small islands of C 60 on graphite that otherwise require hundreds of molecules before a stationary C 60 island can form.Intermediate annealing at 400-500C of C 60 on epitaxial W/MgO(100) produces novel nanostructures with a very similar size and shape to C 60 but with metallic conductivity, a unique atomic-scale stripe pattern on their surface, occasional mobility under the influence of the STM iv tip, and show signs of evolving towards WO 3 under oxidation. These structures increase in diameter and slowly dissolve into the W surface under increasing annealing temperatures.Carbide thin films are synthesized by codeposition onto MgO substrates held above 600˚C. These thin films are determined to be predominantly metastable, cubic WC 1-x phase. At a C/W ratio of 60/40 and above, carbon is observed to surface segregate and form graphite on the surface of the film. At a ratio of 60/40 the surface is heavily populated with graphene, rather than graphite.Oxidation of the films at elevated temperatures in UHV shows that morphological changes, even at atomic resolution, were absent. STS shows that signs of oxidation overspread the surface immediately but that WO 3 nucleates well-defined islands which grow in size with harsher oxidation conditions. For the graphite covered surfaces, graphite appears to protect the underlying carbide from oxidation, and between 300 and 400˚C, O 2 begins to etch the graphite.The underlying carbide appears to oxidize similarly to films without a graphitized surface.Overall, the WC films oxidize much less rapidly than W cluste...

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Study of Microstructure and Interfacial Interaction in Al–C60 Co-Evaporated Films

Hou

Wang

et al. 1997

phys. stat. sol. (a)

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Al–C60 thin films were prepared in vacuum by the co‐evaporation method. The structural and physical properties of the films have been studied with transmission electron microscopy and Raman scattering spectra. The growth of C60 crystallites is significantly limited by co‐deposition of aluminum. Raman spectra showed in these films that the Ag(2) pentagon‐pinch mode of C60 splits into two peaks, corresponding to the pristine and softened Ag(2) modes, respectively. The shifts of the softened Ag(2) mode are about 6 to 9 cm—1, and depend weakly on the microstructures of the films. In addition, there is a substantial variation of the ratio between the intensity of the softened and unsoftened Ag(2) mode. The experimental results could be understood based on the model of Al–C60 interfacial interaction.

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Reaction of C60 with metals: W

Cited by 59 publications

References 12 publications

The Statistical Theory of Monomolecular Fullerene Film Formation on the Crystal Surface

The Statistical Theory of Monomolecular Fullerene Film Formation on the Crystal Surface

Synthesis and Oxidation of non-Stoichiometric Tungsten Carbide Studied by Scanning Tunneling Microscopy/Spectroscopy

Study of Microstructure and Interfacial Interaction in Al–C60 Co-Evaporated Films

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