  The ability to precisely control the electronic coupling/decoupling of
adsorbates from surfaces is an essential goal. It isimportant for fundamental
studies not only in surface science but alsoin several applied domains
including, for example, miniaturizedmolecular electronic or for the development
of various devices suchas nanoscale biosensors or photovoltaic cells. Here, we
provide atomic-scale experimental and theoretical investigations of a
semi-insulatinglayer grown on a silicon surface via its epitaxy with CaF2. We
showthat, following the formation of a wetting layer, the ensuing organizedunit
cells are coupled to additional physisorbed CaF2molecules,periodically located
in their surroundings. This configuration shapesthe formation of ribbons of
stripes that functionalize the semi-conductor surface. The obtained assembly,
having a monolayerthickness, reveals a surface gap energy of 3.2 eV. The
adsorption of iron tetraphenylporphyrin molecules on the ribbons of stripes is
used to estimate the electronic insulating properties of thisstructure via
differential conductance measurements. Density functional theory (DFT)
including several levels of complexity(annealing, DFT +U, and nonlocal van der
Waals functionals) is employed to reproduce our experimental observations.
Ourfindings offer a unique and robust template that brings an alternative
solution to electronic semi-insulating layers on metal surfacessuch as NaCl.
Hence, CaF2/Si(100) ribbon of stripe structures, whose lengths can reach more
than 100 nm, can be used as aversatile surface platform for various
atomic-scale studies of molecular devices.
