Scanning tunneling microscopy and atomic force microscopy can provide detailed information about the geometric and electronic structure of molecules with submolecular spatial resolution. However, an essential capability to realize the full potential of these techniques for chemical applications is missing from the scanning probe toolbox: chemical recognition of organic molecules. Here, we show that maps of the minima of frequency shift-distance curves extracted from 3D data cubes contain characteristic contrast. A detailed theoretical analysis based on density functional theory and molecular mechanics shows that these features are characteristic for the investigated species. Structurally similar but chemically distinct molecules yield significantly different features. We find that the van der Waals and Pauli interaction, together with the specific adsorption geometry of a given molecule on the surface, accounts for the observed contrast.

Condensed Matter and Interfaces Debye Institute for Nanomaterials Science Utrecht University P O Box 80000 3508 TA Utrecht The Netherlands

Department of Chemistry and Pharmaceutical Sciences VU University Amsterdam De Boelelaan 1083 1081 HV Amsterdam The Netherlands

Institute of Physics Czech Academy of Sciences Cukrovarnická 10 1862 53 Prague Czech Republic

Citace poskytuje Crossref.org

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