Why graphene is electronic gold

U. ILLINOIS (US) — Graphene appears to be outpacing its elemental cousin, carbon nanotubes, for use in electronics and other applications.

New findings from the laboratory of University of Illinois researcher Joe Lyding are providing valuable insight into graphene, a single two-dimensional layer of graphite with numerous electronic and mechanical properties.

Lyding reports in the journal Nanoletters using a dry deposition method to deposit pieces of graphene on semiconducting substrates. He and his colleagues also describe the electronic character of graphene at room temperature that they observed while using the method.

“[Graphene] exhibits the quantum hall effect, even at room temperature, and its optical transparency is directly related to the fine structure constant,” the researchers write.

“Graphene is more and more being thought of as a fairly strong and elastic membrane (with an associated potential as a material for NEMS applications). Unlike carbon nanotubes, graphene can be patterned using standard e-beam lithographic techniques, making it an attractive prospect for use in semiconductor devices.”

To reach that goal, issues associated with graphene must be overcome, and the researchers offer insight into a much-needed step in that direction: understanding substrate-graphene interactions toward integration into future nanoelectronic devices.

The team investigated the electronic character of the underlying substrate of graphene at room temperature and reports on “an apparent electronic semitransparency.”

This semitransparency was made manifest through observation of the substrate atomic structure through the graphene.

Lyding’s research group had developed a non-chemical (dry) technique for depositing carbon nanotubes (CNTs) on a surface called Dry Contact Transfer that allowed the CNTs to maintain their electronic properties.

They later applied the method to graphene and were able to deposit pristine, nanometer-sized graphene pieces in situ onto atomically flat UHV-cleaved Gallium arsenide and Indium arsenide semiconductor substrates with low amounts of extraneous contamination.

The electronic semitransparency of the graphene pieces was observed when the UHV STM probe pushed the graphene 0.05nm closer to the surface, causing its electronic structure to mix with that of the surface.

In summary, the researchers write, their results “highlight the significance of graphene-substrate interactions and suggest that proper control of the substrate can have a major effect on the electronic properties of the graphene it supports.”

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