Intramolecular Force Mapping at Room Temperature.

Abstract

Acquisition of dense, three-dimensional, force fields with intramolecular resolution via noncontact atomic force microscopy (NC-AFM) has yielded enormous progress in our ability to characterize molecular and two-dimensional materials at the atomic scale. To date, intramolecular force mapping has been performed exclusively at cryogenic temperatures, due to the stability afforded by low temperature operation, and as the carbon monoxide functionalization of the metallic scanning probe tip, normally required for submolecular resolution, is only stable at low temperature. In this paper we show that high-resolution, three-dimensional force mapping of a single organic molecule is possible even at room temperature. The physical limitations of room temperature operation are overcome using semiconducting materials to inhibit molecular diffusion and create robust tip apexes, while challenges due to thermal drift are overcome with atom tracking based feedforward correction. Three-dimensional force maps comparable in spatial and force resolution to those acquired at low temperature are demonstrated, permitting a quantitative analysis of the adsorption induced changes in the geometry of the molecule at the picometer level.