Submolecular resolution imaging of molecules by atomic force microscopy: the influence of the electrostatic force

ROM 2016-04
Author: Corresponding Author: Ingmar Swart
Institute: Corresponding Institute: Debye Institute for Nanomaterials Science, Utrecht University, P.O. Box 80.000, 3508 TA Utrecht, The Netherlands
Publication: PRL 116, 096102 (2016) PHYSICAL REVIEW LETTERS
Instrument: LT STM

The forces governing the contrast in submolecular resolution imaging of molecules with atomic force microscopy (AFM) have recently become a topic of intense debate. Here, we show that the electrostatic force is essential to understand the contrast in atomically resolved AFM images of polar molecules. Specifically, we image strongly polarized molecules with negatively and positively charged tips. A contrast inversion is observed above the polar groups. By taking into account the electrostatic forces between tip and molecule, the observed contrast differences can be reproduced using a molecular mechanics model. In addition, we analyze the height dependence of the various force components contributing to the highresolution AFM contrast.

List of Authors and Instituttes:
Joost van der Lit,1 Francesca Di Cicco,1 Prokop Hapala,2 Pavel Jelinek,2 and Ingmar Swart1,*

1) Debye Institute for Nanomaterials Science, Utrecht University, P.O. Box 80.000, 3508 TA Utrecht, The Netherlands
2) Institute of Physics, Academy of Sciences of the Czech Republic Cukrovarnicka 10, 1862 53 Prague, Czech Republic

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