Competing Forces during Contact Formation between a Tip and a Single Molecule.
basic_science · Level V
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- Record sourced from PubMed, PMID 26218345.
- Also identified by DOI 10.1021/acs.nanolett.5b01383.
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Abstract
Sn-phthalocyanine adsorbs on Ag(111) in a physisorbed or a chemisorbed configuration. Both structures are contacted with the tip of a combined scanning tunneling and atomic force microscope. The tunneling conductances of both configurations exhibit similar exponential variations with the tip-molecule distance. The short-range forces, however, display nontrivial distance dependencies. First-principles calculations reproduce the experimental results. Both attractive and repulsive interactions occur between the tip and different parts of the molecule due to a combination of bond formation and electrostatic interactions with the tip electric dipole. Consequently, deformations occur and the force varies in the resulting unexpected fashion.