Intramolecular Force Mapping at Room Temperature

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.