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Real-space imaging of molecular structure and chemical bonding by single-molecule inelastic tunneling probe

Science  23 May 2014:
Vol. 344, Issue 6186, pp. 885-888
DOI: 10.1126/science.1253405

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Abstract

The arrangement of atoms and bonds in a molecule influences its physical and chemical properties. The scanning tunneling microscope can provide electronic and vibrational signatures of single molecules. However, these signatures do not relate simply to the molecular structure and bonding. We constructed an inelastic tunneling probe based on the scanning tunneling microscope to sense the local potential energy landscape of an adsorbed molecule with a carbon monoxide (CO)–terminated tip. The skeletal structure and bonding of the molecule are revealed from imaging the spatial variations of a CO vibration as the CO-terminated tip probes the core of the interactions between adjacent atoms. An application of the inelastic tunneling probe reveals the sharing of hydrogen atoms among multiple centers in intramolecular and extramolecular bonding.

Probing bonding profiles with a CO tip

Greater resolution has been achieved in atomic force microscopy by terminating the tip with a sharper probe: an adsorbed CO molecule. Chiang et al. now show that the adsorbed CO tip can reveal the bonding within cobalt phthalocyanine molecules absorbed on silver or gold surfaces. Inelastic tunneling spectroscopy reveals variations in the vibration excitation of the CO molecule that can map out the internal bonding of the molecules, as well as hydrogen bonding between molecules.

Science, this issue p. 885

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