Laser Induces Conduction in Graphene
COLLEGE PARK, Md., June 20, 2011 — By illuminating graphene with a mid-infrared laser, researchers now can open an observable bandgap in the otherwise gapless material, enabling it to become a semiconductor.
Graphene is the thinnest and strongest material ever discovered. It is a layer of carbon atoms only 1 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. Despite the impressive list of promising prospects, however, graphene appears to lack a critical property: a "bandgap."
Graphene is illuminated by a laser field. (Image: Luis E.F. Foa Torres)
A bandgap 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 0's and 1's of computer languages.
Now, a team of researchers at National University of Córdoba and CONICET in Argentina; Catalan Institute of Nanotechnology in Barcelona, Spain; and RWTH Aachen University in 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-size graphene sample illuminated by a laser field. Their simulations show that a laser in the mid-infrared can open an observable bandgap 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," said lead researcher Luis Foa Torres. "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."
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- In a semiconductor material, the minimum energy necessary for an electron to transfer from the valence band into the conduction band, where it moves more freely.
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