posted on 2018-10-26, 00:00authored byCarlo Grazianetti, Stefania De Rosa, Christian Martella, Paolo Targa, Davide Codegoni, Paola Gori, Olivia Pulci, Alessandro Molle, Stefano Lupi
The
exotic electrodynamics properties of graphene come from the
linearly dispersive electronic bands that host massless Dirac electrons.
A similar behavior was predicted to manifest in freestanding silicene,
the silicon counterpart of graphene, thereby envisaging a new route
for silicon photonics. However, the access to silicene exploitation
in photonics was hindered so far by the use of optically inappropriate
substrates in experimentally realized silicene. Here we report on
the optical conductivity of silicon nanosheets epitaxially grown on
optically transparent Al2O3(0001) from a thickness
of a few tens of nanometers down to the extreme two-dimensional (2D)
limit. When a 2D regime is approached, a Dirac-like electrodynamics
can be deduced from the observation of a low-energy optical conductivity
feature owing to a silicene-based interfacing to the substrate.