Competing Forces during Contact Formation between a Tip and a Single Molecule

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• 作者：Nuala M. Caffrey ; Kristof Buchmann ; Nadine Hauptmann ; Cesar Lazo ; Paolo Ferriani ; Stefan Heinze ; Richard Berndt
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：August 12, 2015
• 年：2015
• 卷：15
• 期：8
• 页码：5156-5160
• 全文大小：349K
• ISSN：1530-6992

文摘

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鈥搈olecule 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.