Structural and Electronic Properties of Graphite and Graphite Intercalation Compounds MC8 (M = K, Rb, Cs) Governing Their Scanning Tunneling Microscopy Images

Whangbo, M.‐H.; Ren, Jun; Magonov, S. N.; Wawkuschewski, A.

doi:10.1021/j100082a034

Cited by 52 publications

(44 citation statements)

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“…An asymmetry of STM images with respect to ␤ site carbons in graphite has been observed by several groups. 18,19 Whangbo et al 27 concluded from experimental work that this feature of STM images derived from both mechanic and electronic effects. Our findings of surface polarization and deformation induced by deposited particles support this theory.…”

Section: Discussionmentioning

confidence: 99%

Gold adatoms and dimers on relaxed graphite surfaces

et al. 2004

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The interaction of deposited gold adatoms and dimers with multilayer relaxed graphite surfaces is investigated through a density functional approach with numerical orbitals and a relativistic core pseudopotential. The energy landscape for a gold adatom along ͓110͔ agrees with scanning tunneling microscopy observations including the preferred ␤ binding site for adatoms and the mobility difference between silver and gold adatoms. Deposited particles are shown to induce surface deformation and polarization. Static relaxation and dynamic simulations indicate that the energetically preferred binding orientation for a gold dimer is normal rather than parallel to the graphite surface. The dimer response to a simulated scanning tunneling microscopy tip is investigated by molecular dynamics simulations.

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Section: Discussionmentioning

confidence: 99%

Gold adatoms and dimers on relaxed graphite surfaces

et al. 2004

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“…A simple analysis would lead one to expect the opposite, because the ␣ sites have a direct neighbor underneath and thus should be harder. However, Whangbo et al (29) found that for large tip atoms such as tungsten, the ␤ sites appear to be harder. Fig.…”

Section: Figurementioning

confidence: 99%

Revealing the hidden atom in graphite by low-temperature atomic force microscopy

Hembacher

Giessibl

Mannhart

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

160

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Carbon, the backbone material of life on Earth, comes in three modifications: diamond, graphite, and fullerenes. Diamond develops tetrahedral sp 3 bonds, forming a cubic crystal structure, whereas graphite and fullerenes are characterized by planar sp 2 bonds. Polycrystalline graphite is the basis for many products of everyday life: pencils, lubricants, batteries, arc lamps, and brushes for electric motors. In crystalline form, highly oriented pyrolytic graphite is used as a diffracting element in monochromators for x-ray and neutron scattering and as a calibration standard for scanning tunneling microscopy (STM). The graphite surface is easily prepared as a clean atomically flat surface by cleavage. This feature is attractive and is used in many laboratories as the surface of choice for ''seeing atoms.'' Despite the proverbial ease of imaging graphite by STM with atomic resolution, every second atom in the hexagonal surface unit cell remains hidden, and STM images show only a single atom in the unit cell. Here we present measurements with a low-temperature atomic force microscope with pico-Newton force sensitivity that reveal the hidden surface atom. T he question of the existence of atoms is of central importance to the natural sciences, and the American Nobel physics laureate Richard P. Feynman has stated that in all scientific knowledge, the atomic hypothesis that "all things are made of atoms, little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another" contains the most information in the fewest words (1). Nevertheless, only 100 years ago some of the most distinguished scientists of that time were engaged in heated debates about the existence of atoms (2). To ''see'' atoms is therefore an important endeavor. E. W. Müller (3) achieved an important breakthrough 50 years ago with the invention of the field ion microscope that could later image single atoms on sharp tips with atomic resolution (4). Observing single atoms in real space on flat surfaces became possible 20 years ago with the invention of a marvelous instrument: the scanning tunneling microscope (STM) (5). (For a discussion of the relation between STM and other highresolution electron microscopy techniques, see chapter 1.8 in ref.6.) In particular, low-temperature STM provides exciting possibilities for arranging and studying matter on the nanoscale (7). STM creates images of the charge density of electrons at the Fermi level (8). In some cases, all surface atoms develop a local maximum of the charge density at the Fermi level and thus all surface atoms are observable by STM. In other cases, like GaAs (110), one type of surface atoms (As) is observable at negative sample bias and the other type (Ga) at positive sample bias (9). The graphite (0001) surface also has two types of atoms in the basis of the hexagonal surface unit cell (␣ and ␤, see Fig. 1A), but only one of these atom types is observed by STM, independent of the bias polarity. The...

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“…[1][2][3][4][5][6] The most common stoichiometry is C 8 K. [7] Although, initially, C 8 K was used as a catalyst in polymerization reactions, [8] and in the nuclear and side-chain alkylation of aromatic compounds by ethylene, [9] the use of C 8 K as a reducing agent has also been investigated. [10][11][12][13][14][15][16][17][18][19][20] The use of C 8 K as a metallation agent in the alkylation of nitriles, esters, [21] and oxazines, [22] and in the reductive cleavage of carbonsulfur bonds in vinylic and allylic sulfones has been reported.…”

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confidence: 99%