Electric-field control of a single-atom polar bond

TL;DR

This study demonstrates how an external electric field can reversibly control the strength and breaking of a single-atom polar bond between gold and graphene, combining experimental and theoretical insights.

Contribution

It provides new understanding of electric-field manipulation of atomic-scale bonds using combined experimental and computational approaches.

Findings

Electric field can strengthen or break the Au-C bond depending on orientation.

Density functional theory supports experimental bond strength observations.

Charge transfer under electric field alters bond polarity and strength.

Abstract

The polar covalent bond between a single Au atom terminating the apex of an atomic force microscope tip and a C atom of graphene on SiC(0001) is exposed to an external electric field. For one field orientation the Au-C bond is strong enough to sustain the mechanical load of partially detached graphene, whilst for the opposite orientation the bond breaks easily. Calculations based on density functional theory and nonequilibrium Green's function methods support the experimental observations by unveiling bond forces that reflect the polar character of the bond. Field-induced charge transfer between the atomic orbitals modifies the polarity of the different electronegative reaction partners and the Au-C bond strength.