Graphene is illuminated by a laser field (artist image). Credit: Luis E. F. Foa Torres

A
team of researchers has proposed a way to turn the material graphene
into a semiconductor, enabling it to control the flow of electrons with a
laser “on-off switch”.

   

Graphene
is thinnest and strongest material ever discovered. It’s a layer of
carbon atoms only one-atom thick, but 200 times stronger than steel. It
also conducts electricity extremely well and heat better than any other
known material. It is almost completely transparent, yet so dense that
not even atoms of helium can penetrate it. In spite of the impressive
list of promising prospects, however, graphene appears to lack a
critical property — it doesn’t have a “band gap.”

   

A
band gap is the basic property of semiconductors, enabling materials to
control the flow of electrons. This on-off property is the foundation
of computers, encoding the 0s and 1s of computer languages.

   

Now,
a team of researchers at the National University of Córdoba and CONICET
in Argentina; the Institut Catala de Nanotecnologia in Barcelona,
Spain; and RWTH Aachen University, Germany; suggest that illuminating
graphene with a mid-infrared laser could be a key to switch off
conduction, thereby improving the possibilities for novel optoelectronic
devices.

   

In
an article featured in Applied Physics Letters, the researchers report
on the first atomistic simulations of electrical conduction through a
micrometer-sized graphene sample illuminated by a laser field. Their
simulations show that a laser in the mid-infrared can open an observable
band gap in this otherwise gapless material.

   

“Imagine
that by turning on the light, graphene conduction is turned off, or
vice versa. This would allow the transduction of optical into electrical
signals,” says Luis Foa Torres, the researcher leading this
collaboration. “The problem of graphene interacting with radiation is
also of current interest for the understanding of more exotic states of
matter such as the topological insulators.”

Tuning laser-induced band gaps in graphene

   

SOURCE: American Institute of Physics