Strumming a Single Chemical Bond

Weymouth, Alfred J.; Riegel, Elisabeth; Gretz, Oliver; Giessibl, Franz J.

doi:10.1103/physrevlett.124.196101

Cited by 10 publications

(21 citation statements)

References 39 publications

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“…On the other hand, such a behavior of the lateral frequency shift was also observed by Weymouth et al. [ 55 ] on the carbon bonds of 3,4,9,10‐perylenetetracarboxylic dianhydride (PTCDA). A completely different distribution was observed if the torsional oscillation direction was approximately along the armchair direction of the carbon bonds, such as visible in Figure 6d,f.…”

Section: Resultssupporting

confidence: 59%

Simultaneous Deconvolution of In‐Plane and Out‐of‐Plane Forces of HOPG at the Atomic Scale under Ambient Conditions by Multifrequency Atomic Force Microscopy

Eichhorn

Dietz

2021

Adv Materials Inter

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Multifrequency atomic force microscopy (AFM) is shown to be an excellent tool for imaging crystal structures at atomic resolution in different spatial directions. However, determining the forces between single atoms remains challenging, particularly in air under ambient conditions. Developed here is a trimodal AFM approach that simultaneously acquires torsional and flexural frequency‐shift images and spectroscopic data to transfer these observables into in‐plane and out‐of‐plane forces between single bonds of highly oriented pyrolytic graphite (HOPG) at atomic resolution in air under ambient conditions based on the Fourier method. It is found that the cantilever mean deflection is an excellent indicator to understand that strong attractive interactions between the tip and the surface of HOPG in dynamic AFM imply a local lift of the topmost carbon layer when using higher eigenmodes for the topographical feedback. Cross‐talk between torsional and flexural‐oscillation modes is shown to be negligible. Interestingly, significant differences are observed in the in‐plane forces depending on the orientation of the carbon bonds relative to the direction of torsional oscillation.

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Section: Resultssupporting

confidence: 59%

Simultaneous Deconvolution of In‐Plane and Out‐of‐Plane Forces of HOPG at the Atomic Scale under Ambient Conditions by Multifrequency Atomic Force Microscopy

Eichhorn

Dietz

2021

Adv Materials Inter

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“…At this point, a full image was acquired with no switching and the molecule remained in the rotated state, as shown in the STM image in Figure E. The LFM image and evaluated potential energy landscape are shown in Figure F and G. The overall interaction is still strongly attractive above the molecule as can be seen with a minimum potential energy over the molecule of −90 meV, but the intramolecular contrast seen in Δ f is an indication of short-range repulsive forces between the tip and molecule …”

Section: Resultsmentioning

confidence: 99%

“…The probe-particle model was described in ref for simulating AFM data. We modified it to simulate LFM data as described in ref .…”

Section: Methodsmentioning

confidence: 99%

“…To perform LFM, we constructed a sensor so that the tip oscillates laterally above the surface . By oscillating with amplitudes small relative to the distance between atoms, we can also achieve intramolecular resolution . Above a flat terrace, LFM is not sensitive to long-range forces and we can determine the potential energy landscape over isolated molecules with it .…”

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confidence: 99%

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Lateral Force Microscopy Reveals the Energy Barrier of a Molecular Switch

et al. 2021

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Copper phthalocyanine (CuPc) is a small molecule often used in organic light emitting diodes where it is deposited on a conducting electrode. Previous scanning tunneling microscopy (STM) studies of CuPc on Cu(111) have shown that inelastic tunneling events can cause CuPc to switch between a ground state and two symmetrically equivalent metastable states in which the molecule is rotated. We investigated CuPc on Cu(111) and Ag(111) with STM and lateral force microscopy (LFM). Even without inelastic events, the presence of the tip can induce rotations and upon closer approach, causes the rotated states to be favored. Combining STM measurements at various temperatures and LFM measurements, we show that the long-range attraction of the tip changes the potential energy landscape of this molecular switch. We can also determine the geometry of the rotated and ground states. We compare our observations of CuPc on Cu(111) to CuPc on Ag(111). On Ag(111), CuPc appears flat and does not rotate. Stronger bonding typically involves shorter bond lengths, larger shifts of energy levels, and structural stability. Although the binding of CuPc to Cu(111) is stronger than that on Ag(111), the nonplanar geometry of CuPc on Cu(111) is accompanied by two metastable states which are not present on the Ag(111) surface.

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“…In our group, we have used this method to quantify molecular stiffness at low temperature [ 9 ] and to evaluate the potential energy landscape above a molecule at room temperature [ 10 ]. More recently, we used LFM with a CO-terminated tip to investigate the internal structure of a molecular adsorbate [ 11 – 12 ]. Moreover, other methods, including the use of a long tip on a qPlus sensor that oscillates laterally at a higher flexural mode are also possible [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

Determining amplitude and tilt of a lateral force microscopy sensor

Gretz¹,

Weymouth²,

Holzmann³

et al. 2021

Beilstein J. Nanotechnol.

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In lateral force microscopy (LFM), implemented as frequency-modulation atomic force microscopy, the tip oscillates parallel to the surface. Existing amplitude calibration methods are not applicable for mechanically excited LFM sensors at low temperature. Moreover, a slight angular offset of the oscillation direction (tilt) has a significant influence on the acquired data. To determine the amplitude and tilt we make use of the scanning tunneling microscopy (STM) channel and acquire data without and with oscillation of the tip above a local surface feature. We use a full two-dimensional current map of the STM data without oscillation to simulate data for a given amplitude and tilt. Finally, the amplitude and tilt are determined by fitting the simulation output to the data with oscillation.

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Strumming a Single Chemical Bond

Cited by 10 publications

References 39 publications

Simultaneous Deconvolution of In‐Plane and Out‐of‐Plane Forces of HOPG at the Atomic Scale under Ambient Conditions by Multifrequency Atomic Force Microscopy

Simultaneous Deconvolution of In‐Plane and Out‐of‐Plane Forces of HOPG at the Atomic Scale under Ambient Conditions by Multifrequency Atomic Force Microscopy

Lateral Force Microscopy Reveals the Energy Barrier of a Molecular Switch

Determining amplitude and tilt of a lateral force microscopy sensor

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