  Carbon nanosheets are mechanically stable free-standing two-dimensional
materials with a thickness of ~1 nm and well defined physical and chemical
properties. They are made by radiation induced cross-linking of aromatic
self-assembled monolayers. Here we present a route to the scalable fabrication
of multilayer nanosheets with tunable electrical, optical and chemical
properties on insulating substrates. Stacks up to five nanosheets with sizes of
~1 cm^2 on oxidized silicon were studied. Their optical characteristics were
investigated by visual inspection, optical microscopy, UV/Vis reflection
spectroscopy and model calculations. Their chemical composition was studied by
X-ray photoelectron spectroscopy. The multilayer samples were then annealed in
ultra high vacuum at various temperatures up to 1100 K. A subsequent
investigation by Raman, X-ray photoelectron and UV/Vis reflection spectroscopy
as well as by electrical four-point probe measurements demonstrates that the
layered nanosheets transform into nanocrystalline graphene. This structural and
chemical transformation is accompanied by changes in the optical properties and
electrical conductivity and opens up a new path for the fabrication of
ultrathin functional conductive coatings.
