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The Chemical Structure of a Molecule Resolved by Atomic Force Microscopy

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Resolving individual atoms has always been the ultimate goal of surface microscopy. The scanning tunneling microscope images atomic-scale features on surfaces, but resolving single atoms within an adsorbed molecule remains a great challenge because the tunneling current is primarily sensitive to the local electron density of states close to the Fermi level. We demonstrate imaging of molecules with unprecedented atomic resolution by probing the short-range chemical forces with use of noncontact atomic force microscopy. The key step is functionalizing the microscope’s tip apex with suitable, atomically well-defined terminations, such as CO molecules. Our experimental findings are corroborated by ab initio density functional theory calculations. Comparison with theory shows that Pauli repulsion is the source of the atomic resolution, whereas van der Waals and electrostatic forces only add a diffuse attractive background.
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... ) along with HOMA of each ring. The AFM image is reproduced from Ref. [119] with permission from AAAS. The EDDB(r) representation is reproduced from Ref. [99] with permission from the PCCP Owner Societies. ...
... [53]) along with HOMA of each ring. The AFM image is reproduced from Ref. [119] with permission from AAAS. The EDDB(r) representation is reproduced from Ref. [99] with permission from the PCCP Owner Societies. ...
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... Therefore, we expect that the demonstrated atomic resolution can be further expanded with the nc-AFM developments; for instance, improving lateral resolution of force spectroscopy shown in Fig. 1 might allow chemical identification of atoms with the advantage of a direct measurement of the force acting between tip apex and surface atoms [ Fig. 1(a)] [50,51]. Also, like nc-AFM, we expect that the resolution and reproducibility might be further improved by improving the control over the tip apex structure [52,53]. ...
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