Scanning transmission microscopy image of the various surface domains of silicene.

The
current standard in computer architecture is based upon silicon
technology, which is what allows you to read this webpage, for instance,
and its revolutionary influence during the digital age now leaves
almost no corner of modern life untouched. In order to meet our
increasing demands for more memory and for higher speed, the dimensions
of the silicon-based devices which make up our computers continue to get
smaller. As we begin to reach the limits of the current form of this
technology, the question is what is next? According to recent work by
Alessandro Molle and co-workers in Italy, the next generation of
computing could be performed with silicene, an atomically thin form of
silicon which has the potential to revolutionize nanoelectronics.

The
silicene structure consists of one atomic layer of silicon atoms and in
this way it is analogous to graphene, the atomically thin sheet of
carbon atoms which has been the subject of high research interest in
recent years. For all of graphene’s promise, one of its limitations is
the lack of a naturally occurring band gap in its electronic states.
This band gap is of fundamental importance for creating the electronic
switches and logic circuits which make up digital electronic devices.
There has been some recent progress in inducing a band gap into
graphene, but it involves complicated methods such as bringing the
graphene sheets into contact with a strongly-interacting substrate,
which can sufficiently perturb the electronic properties. Alternatively,
silicene exhibits a band gap even without modification and, it has the
advantage of inherent compatibility with the silicon technology
infrastructure already used in manufacturing much of today’s digital
electronics.

In
Molle’s studies, his team grew thin layers of silicene on silver
substrates using molecular beam epitaxy. Using scanning tunneling
microscopy, various domains of silicene were observed, showing
drastically different surface symmetries as illustrated in the
accompanying image above. Using tunneling spectroscopy, the researchers
were able to show that the buckled structures, where the strict
2-dimensional symmetry was broken, exhibited qualitatively different
electronic properties than the non-buckled phases. Understanding the
details of these structure-property relationships is very important for
controlling the electrical properties of the silicene thin films, and
with further study, the emergence of the different silicene structures
could be controlled by tailoring the growth conditions. Once these
issues have been overcome, the next generation of computers may still be
made of silicon after all – only thinner.

Local Electronic Properties of Corrugated Silicene Phases

Source: Wiley