Microscopy reveals 'atomic antenna' behavior in graphene

Jan 31, 2012
Electron microscopy at Oak Ridge National Laboratory has demonstrated that silicon atoms (seen in white) can act like "atomic antennae" in graphene to transmit an electronic signal at the atomic scale. Credit: ORNL

Atomic-level defects in graphene could be a path forward to smaller and faster electronic devices, according to a study led by researchers at the Department of Energy's Oak Ridge National Laboratory.

With unique properties and potential applications in areas from electronics to biodevices, graphene, which consists of a single sheet of carbon atoms, has been hailed as a rising star in the materials world. Now, an ORNL study published in Nature Nanotechnology suggests that point defects, composed of that replace individual in graphene, could aid attempts to transfer data on an by coupling light with electrons.

"In this experiment, we have shown that a tiny wire made up of a pair of single silicon atoms in graphene can be used to convert light into an electronic signal, transmit the signal and then convert the signal back into light," said coauthor Juan-Carlos Idrobo, who holds a joint appointment at ORNL and Vanderbilt University.

An ORNL-led team discovered this novel behavior by using aberration-corrected to image the plasmon response, or optical-like signals, of the point defects. The team's analysis found that the silicon atoms act like atomic-sized antennae, enhancing the local surface plasmon response of graphene, and creating a prototypical plasmonic device.

"The idea with plasmonic devices is that they can convert into ," Idrobo said. "So you could make really tiny wires, put light in one side of the wire, and that signal will be transformed into collective electron excitations known as plasmons. The plasmons will transmit the signal through the wire, come out the other side and be converted back to light."

Although other plasmonic devices have been demonstrated, previous research in has been focused primarily on metals, which has limited the scale at which the signal transfer occurs.

"When researchers use metal for plasmonic devices, they can usually only get down to 5 - 7 nanometers," said coauthor Wu Zhou. "But when you want to make things smaller, you always want to know the limit. Nobody thought we could get down to a single atom level."

In-depth analysis at the level of a single atom was made possible through the team's access to an electron microscope that is part of ORNL's Shared Research Equipment (ShaRE) User Facility.

"It is the one of only a few electron microscopes in the world that we can use to look at and study materials and obtain crystallography, chemistry, bonding, optical and plasmon properties at the atomic scale with single atom sensitivity and at low voltages," Idrobo said. "This is an ideal microscope for people who want to research carbon-based materials, such as graphene."

In addition to its microscopic observations, the ORNL team employed theoretical first-principles calculations to confirm the stability of the observed point defects. The full paper, titled "Atomically Localized Plasmon Enhancement in Monolayer Graphene," is available online here: http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2011.252.html.

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antialias_physorg
not rated yet Feb 01, 2012
In this proof of concept experiment, we have shown that a tiny wire made up of a pair of single silicon atoms in graphene can be used to convert light into an electronic signal, transmit the signal and then convert the signal back into light
At what efficiency?
Are we talking -in another context- about a potentially ultra efficient solar cell here?

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