Surface templating by electrostatic surface potentials is the least invasive way to
design large-scale artificial nanostructures. However, generating sufficiently large
potential gradients remains challenging. Here, we lay the groundwork for significantly
enhancing local electrostatic fields by chemical modification of the surface. We consider
the hexagonal boron nitride (h-BN) nanomesh on Rh(111), which already exhibits small
surface potential gradients between its pore and wire regions. Using photoemission
spectroscopy, we show that adding Au atoms to the Rh(111) surface layer leads to a
local migration of Au atoms below the wire regions of the nanomesh. This significantly
increases the local work function difference between the pore and wire regions that
can be quantified experimentally by the changes in the h-BN valence band structure.
Using density functional theory, we identify an electron transfer from Rh to Au as
the microscopic origin for the local enhancement of potential gradients within the
h-BN nanomesh.
