Bond-Order Discrimination by Atomic Force Microscopy

Leo Gross, Fabian Mohn, Nikolaj Moll, Bruno Schuler, Alejandro Criado, Enrique Guitián, Diego Peña, André Gourdon, Gerhard Meyer

We show that the different bond orders of individual carbon-carbon bonds in polycyclic aromatic hydrocarbons and fullerenes can be distinguished by noncontact atomic force microscopy (AFM) with a carbon monoxide (CO)–functionalized tip. We found two different contrast mechanisms, which were corroborated by density functional theory calculations: The greater electron density in bonds of higher bond order led to a stronger Pauli repulsion, which enhanced the brightness of these bonds in high-resolution AFM images. The apparent bond length in the AFM images decreased with increasing bond order because of tilting of the CO molecule at the tip apex.

DOI

Journal: Science