Scientists Move Graphene Closer To Transistor Applications


Scientists at the U.S. Department of Energy's Ames
Laboratory successfully manipulated the electronic structure of graphene, which
may enable the fabrication of graphene transistors-- faster and more reliable
than existing silicon-based transistors.

The researchers were able to theoretically calculate the
mechanism by which graphene's electronic band structure could be modified with
metal atoms. The work will guide experimentally the use of the effect in layers
of graphene with rare-earth metal ions "sandwiched" (or intercalated) between
graphene and its silicon carbide substrate. Because the metal atoms are
magnetic the additions can also modify the use of graphene for spintronics.

"We are discovering new and more useful versions of
graphene," said Ames Laboratory senior scientist Michael C. Tringides. "We
found that the placement of the rare earth metals below graphene, and precisely
where they are located, in the layers between graphene and its substrate, is
critical to manipulating the bands and tune the band gap."

Graphene, a two-dimensional layer of carbon, has been
extensively studied by researchers everywhere since it was first produced in
2004 because electrons travel much faster along its surface, making it an ideal
potential material for future electronic technologies. But the inability to
control or tune graphene's unique properties has been an obstacle to its

Density Functional Theory calculations predicted the
configurations necessary to demonstrate control of the band gap structure.
"Ames Laboratory is very good at synthesis of materials, and we use theory to
precisely determine how to modify the metal atoms," said Minsung Kim, a
postdoctoral research associate. "Our calculations guided the placement so that
we can manipulate these quantum properties to behave the way we want them to."

The research is further discussed in the paper "Manipulation
of Dirac cones in intercalated epitaxial graphene," authored by Minsung Kim,
Michael C. Tringides, Matthew T. Hershberger, Shen Chen, Myron Hupalo, Patricia
A. Thiel, Cai-Zhuang Wang, and Kai-Ming Ho; and published in the journal Carbon.

The work was supported by the U.S. Department of Department
of Energy's Office of Science. Computations were performed through the support
of the National Energy Research Scientific Computing Center (NERSC), a DOE
Office of Science User Facility at Lawrence Berkeley National Laboratory.

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