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

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...

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Veröffentlicht in:Advanced materials interfaces 2021-10, Vol.8 (20), p.n/a
Hauptverfasser: Eichhorn, Anna L., Dietz, Christian
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Sprache:eng
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Zusammenfassung: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. Trimodal atomic force microscopy discriminates in‐plane and out‐of‐plane forces between atomic sides of highly oriented pyrolytic graphite in air under ambient conditions. The in‐plane forces show significant differences depending on the orientation between carbon hexagons (armchair or zigzag) and the oscillation direction of the cantilever. The simultaneously determined out‐of‐plane forces do not show this anisotropy, corroborating the complementary nature of the excited cantilever eigenmodes.
ISSN:2196-7350
2196-7350
DOI:10.1002/admi.202101288