Multiple-tip interpretation of anomalous scanning-tunneling-microscopy images of layered materials

Mizes, H. A.; Park, Sang-Il; Harrison, Walter A.

doi:10.1103/physrevb.36.4491

Cited by 180 publications

(76 citation statements)

References 10 publications

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“…There are however also a number of tip-related effects that can explain the distortion of the hexagonal graphene lattice. 12,13 The geometrical shape of the tip and the type of electronic orbitals protruding from the tip apex play an important role in the apparent contrast of the lattice. Mizes et al 12 argued that the STM image of an hexagonal lattice is built up by three independent Fourier components of equal magnitude.…”

Section: Stm Data Analysismentioning

confidence: 99%

“…12,13 The geometrical shape of the tip and the type of electronic orbitals protruding from the tip apex play an important role in the apparent contrast of the lattice. Mizes et al 12 argued that the STM image of an hexagonal lattice is built up by three independent Fourier components of equal magnitude. Imaging with a multiatom tip leads to a superposition of several images, where the three components that make up the total image are not equal.…”

Section: Stm Data Analysismentioning

confidence: 99%

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Atomic structure of carbon nanotubes from scanning tunneling microscopy

et al. 2000

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The atomic structure of a carbon nanotube can be described by its chiral angle and diameter and can be specified by a pair of lattice indices (n,m). The electronic and mechanical properties are critically dependent on these indices. Scanning tunneling microscopy ͑STM͒ is a useful tool to investigate carbon nanotubes since the atomic structure as well as the electronic properties of individual molecules can be determined. This paper presents a discussion of the technique to obtain (n,m) indices of nanotubes from STM images in combination with current-voltage tunnel spectra. Image contrast, distortion effects, and determination of chiral angle and diameter are discussed. The procedure of (n,m) identification is demonstrated for a few single-walled carbon nanotubes.

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Section: Stm Data Analysismentioning

confidence: 99%

Section: Stm Data Analysismentioning

confidence: 99%

Atomic structure of carbon nanotubes from scanning tunneling microscopy

et al. 2000

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“…Although a honeycomb pattern should be recovered for larger biases, the experimental evidence accumulated over the past 25 years [9][10][11][12][13] shows that STM images with a hexagonal pattern are overwhelmingly recorded over a broad range of bias voltages and distance operation conditions. Nevertheless, several groups have reported honeycomb patterns even for small bias voltage [13][14][15][16][17].…”

mentioning

confidence: 99%

Forces and Currents in Carbon Nanostructures: Are We Imaging Atoms?

et al. 2011

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First-principles calculations show that the rich variety of image patterns found in carbon nanostructures with the atomic force and scanning tunneling microscopes can be rationalized in terms of the chemical reactivity of the tip and the distance range explored in the experiments. For weakly reactive tips, the Pauli repulsion dominates the atomic contrast and force maxima are expected on low electronic density positions as the hollow site. With reactive tips, the interaction is strong enough to change locally the hybridization of the carbon atoms, making it possible to observe atomic resolution in both the attractive and the repulsive regime although with inverted contrast. Regarding STM images, we show that in the near-contact regime, due to current saturation, bright spots correspond to hollow positions instead of atomic sites, providing an explanation for the most common hexagonal pattern found in the experiments. Fullerenes, nanotubes, graphene, and carbon nanoribbons are among the most promising materials for nanotechnological applications due to their unique mechanical and electronic properties [1,2]. Turning these expectations into real-world devices requires tools like the STM and the atomic force microscope (AFM) with true atomic resolution (FM-AFM) [3] to visualize, characterize, and manipulate these materials at the atomic scale. However, in spite of the apparent simplicity of the common honeycomb structure and the long-standing experimental research effort, we do not know yet something as fundamental as whether the maxima in the scanning probe microscopy images correspond to atoms or to the hollow sites [4][5][6][7]. Here, we use first-principles calculations to show that the rich variety of AFM and STM image patterns found in carbon nanostructures can be rationalized in terms of the chemical reactivity of the tip and the distance range explored in the experiments.The first STM images of the graphite(0001) surface did not display the expected honeycomb pattern but a hexagonal arrangement of bright spots (topographic maxima; see Fig. 1 in [8]) [9][10][11]. The accepted interpretation relies on a subtle electronic effect [12]. The Bernal stacking makes the two surface atoms inequivalent. C atoms, with a nearest neighbor right below in the second layer, do not contribute significantly to the density of states close to the Fermi level, and only the C atoms are imaged as bright spots at low bias voltages. Although a honeycomb pattern should be recovered for larger biases, the experimental evidence accumulated over the past 25 years [9][10][11][12][13] shows that STM images with a hexagonal pattern are overwhelmingly recorded over a broad range of bias voltages and distance operation conditions. Nevertheless, several groups have reported honeycomb patterns even for small bias voltage [13][14][15][16][17].The FM-AFM, relying on the forces between the tip and surface, is expected not to be so sensitive to electronic effects and to reflect the real atomic structure of the surface. However, the first reported ...

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“…The samples were prepared as previously [1] [7]. Moreover, supposing continuity from the hexagonal domain to the triangular one, we are able to confirm that the holes in the triangular domain actually correspond to the centers of the hexagons as supposed by Ibrsoff [8].…”

Section: Methodsmentioning

confidence: 73%