Surface-relaxation-induced giant corrugation on graphite (0001)

Kawai, Shigeki; Kawakatsu, Hideki

doi:10.1103/physrevb.79.115440

Cited by 31 publications

(38 citation statements)

References 33 publications

(32 reference statements)

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“…However, they fail to reproduce the moiré contrast in the attractive regime and the dissipation in the experiments. It has been proposed that in STM or AFM experiments on layered materials as graphite, the tips could detach large areas of the last layer from the underneath substrate [9,44,45]. This tip-induced detaching could explain our dissipation signal: during tip approach, G is attached to the substrate, but, upon tip retraction, G locally adheres to the tip temporally, inducing a large-scale deformation of the sheet.…”

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confidence: 98%

“…This atomic-scale resolution allowed the observation of an inversion from attractive to repulsive atomic contrast with decreasing tip-sample distance predicted theoretically for reactive tips [14]. Except for graphite [9,10], atomic resolution in weakly coupled G-based materials using cantilever AFM with large oscillation amplitudes has not been reported.The origin of the moiré contrast in G=Ir was explored with experimental Δf vs distance curves on the atop (highest) and fcc (lowest) areas [28]. These curves have minima that differ by ∼20% and are displaced by ∼1 Å. Density-functional theory (DFT) calculations with a fiveatom W tip that do not include any atomic relaxations provide very similar interaction energy curves that are only shifted by 0.40 Å.…”

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confidence: 99%

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confidence: 99%

“…Dynamic AFM [1] in the frequency modulation (FM) mode [2] has resolved the true geometric structure of a broad range of materials [3][4][5]. FM AFM experiments on carbon-based materials [6][7][8][9][10][11][12][13] show atomic contrast in Δf images and, depending on the setup, in the dissipation channel. While the origin of the dissipation is not well understood, the Δf contrast has been linked with the nature of the tip-sample interaction [14].…”

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Atomic-Scale Variations of the Mechanical Response of 2D Materials Detected by Noncontact Atomic Force Microscopy

et al. 2016

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We show that noncontact atomic force microscopy (AFM) is sensitive to the local stiffness in the atomicscale limit on weakly coupled 2D materials, as graphene on metals. Our large amplitude AFM topography and dissipation images under ultrahigh vacuum and low temperature resolve the atomic and moiré patterns in graphene on Pt(111), despite its extremely low geometric corrugation. The imaging mechanisms are identified with a multiscale model based on density-functional theory calculations, where the energy cost of global and local deformations of graphene competes with short-range chemical and long-range van der Waals interactions. Atomic contrast is related with short-range tip-sample interactions, while the dissipation can be understood in terms of global deformations in the weakly coupled graphene layer. Remarkably, the observed moiré modulation is linked with the subtle variations of the local interplanar graphene-substrate interaction, opening a new route to explore the local mechanical properties of 2D materials at the atomic scale. DOI: 10.1103/PhysRevLett.116.245502 Atomic force microscopy (AFM) and scanning tunneling microscopy (STM) are tools of choice for characterizing the unique mechanical and electronic properties of graphene (G) and other 2D materials. Dynamic AFM [1] in the frequency modulation (FM) mode [2] has resolved the true geometric structure of a broad range of materials [3][4][5]. FM AFM experiments on carbon-based materials [6][7][8][9][10][11][12][13] show atomic contrast in Δf images and, depending on the setup, in the dissipation channel. While the origin of the dissipation is not well understood, the Δf contrast has been linked with the nature of the tip-sample interaction [14].G properties can be efficiently tuned by the interaction with metals [15,16]. The interaction strength varies widely from the strong coupling with Rh [17,18] and Ru [19] to the weak limit (Ir [20], Pt [21]), where G retains its unique electronic properties [22]. The different lattice parameters of G and the metal underneath are accommodated through the formation of commensurate structures known as moiré patterns, where C atoms become inequivalent due to their different bonding configuration with the metal. The resulting "true" topographic corrugation of G-the difference in height among the topmost and the bottom C atom-varies widely, even in the weakly interacting cases, where it ranges from ≈50 pm on Ir [23,24] to practically flat (≤ 3 pm) on Pt [21].While STM can easily resolve these moiré patterns, even in the G=Pt case [21,25], AFM experiments have only been reported in highly corrugated cases as Ru [26], Rh [27], and Ir [12,28]. Focusing on the most challenging case, G=Ir, experiments with a Kolibri sensor using a W tip clearly resolved the moiré in constant height (CH) AFM images [28]. Measurements with a tuning fork using both inert (CO-terminated) and reactive (Ir-terminated) tips [12] were able to identify the atoms with both tips at any tip-sample distance. This atomic-scale resolution allowed the ...

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Atomic-Scale Variations of the Mechanical Response of 2D Materials Detected by Noncontact Atomic Force Microscopy

et al. 2016

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“…On the other hand, in an AFM study at room temperature using higher flexural modes to operate with a similarly small amplitude [20], all of the carbon atoms were imaged.…”

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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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Three‐Dimensional Atomic Force Microscopy – Taking Surface Imaging to the Next Level

et al. 2010

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Materials properties are ultimately determined by the nature of the interactions between the atoms that form the material. On surfaces, the site-specific spatial distribution of force and energy fields governs the phenomena encountered. This article reviews recent progress in the development of a measurement mode called three-dimensional atomic force microscopy (3D-AFM) that allows the dense, three-dimensional mapping of these surface fields with atomic resolution. Based on noncontact atomic force microscopy, 3D-AFM is able to provide more detailed information on surface properties than ever before, thanks to the simultaneous multi-channel acquisition of complementary spatial data such as local energy dissipation and tunneling currents. By illustrating the results of experiments performed on graphite and pentacene, we explain how 3D-AFM data acquisition works, what challenges have to be addressed in its realization, and what type of data can be extracted from the experiments. Finally, a multitude of potential applications are discussed, with special emphasis on chemical imaging, heterogeneous catalysis, and nanotribology.

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Surface-relaxation-induced giant corrugation on graphite (0001)

Cited by 31 publications

References 33 publications

Atomic-Scale Variations of the Mechanical Response of 2D Materials Detected by Noncontact Atomic Force Microscopy

Atomic-Scale Variations of the Mechanical Response of 2D Materials Detected by Noncontact Atomic Force Microscopy

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

Three‐Dimensional Atomic Force Microscopy – Taking Surface Imaging to the Next Level

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