  The surface diffusion potential landscape plays an essential role in a number
of physical and chemical processes such as self-assembly and catalysis.
Diffusion energy barriers can be calculated theoretically for simple systems,
but there is currently no experimental technique to systematically measure them
on the relevant atomic length scale. Here, we introduce an atomic force
microscopy based method to semiquantitatively map the surface diffusion
potential on an atomic length scale. In this proof of concept experiment, we
show that the atomic force microscope damping signal at constant
frequency-shift can be linked to nonconservative processes associated with the
lowering of energy barriers and compared with calculated single-atom diffusion
energy barriers.
