AFM Imaging of Mercaptobenzoic Acid on Au(110): Submolecular Contrast with Metal Tips

NADINE HAUPTMANN; R. ROBLES; P. N. ABUFAGER; N. LORENTE; R. BERNDT

The Journal of Physical Chemistry Letters

American Chemical Society

Año: 2016 vol. 7 p. 1984 - 1990

ABSTRACT: A self-assembled monolayer of mercaptobenzoic acid (MBA) on Au(110) is investigated with scanning tunneling and atomic force microscopy (STM and AFM) and density functional calculations. High-resolution AFM images obtained with metallic tips show clearcontrasts between oxygen atoms and phenyl moieties. The contrast above the oxygen atoms is due to attractive covalent interactions, which is different than previously reported high-resolutionimages, where Pauli repulsion dominated the image contrast. We show that the bonding of MBA to the substrate occurs mainly through dispersion interactions, whereas the thiol−Au bond contributesonly a quarter of the adsorption energy. No indication of Au adatoms mediating the thiol−Au interaction was found in contrast to other thiol-bonded systems. However, MBA lifts the Au(110)-(2 × 1) reconstruction.