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Image shows graphene, which can
act as an atomic-scale billiard table, with electric charges
acting as billiard balls.
Helium-3 refrigerator at UCR that was used by
Lau and her research team in the graphene experiments.
Images � by Lau lab, UC-Riverside |
Study results appeared in a issue of Science.
The research team, led by Chun Ning (Jeanie) Lau, found that the
electrons in graphene are reflected back by the only obstacle they
meet: graphene�s boundaries.
�These electrons meet no other obstacles and behave like quantum
billiard balls,� said Lau, an assistant professor who joined UCR�s
Department of Physics and Astronomy in 2004. �They display properties
that resemble both particles and waves.�
Lau observed that when the electrons are reflected from one of the
boundaries of graphene, the original and reflected components of the
electron can interfere with each other, the way outgoing ripples in a
pond might interfere with ripples reflected back from the banks.
Her lab detected the �electronic interference� by measuring graphene�s
electrical conductivity at extremely low (0.26 Kelvin) temperatures.
She explained that at such low temperatures the quantum properties of
electrons can be studied more easily.
�We found that the electrons in graphene can display wave-like
properties, which could lead to interesting applications such as
ballistic transistors, which is a new type of transistor, as well as
resonant cavities for electrons,� Lau said. She explained that a
resonant cavity is a chamber, like a kitchen microwave, in which waves
can bounce back and forth.
In their experiments, Lau and her colleagues first peeled off a single
sheet of graphene from graphite, a layered structure consisting of
rings of six carbon atoms arranged in stacked horizontal sheets. Next,
the researchers attached nanoscale electrodes to the graphene sheet,
which they then refrigerated in a cooling device. Finally, they
measured the electrical conductivity of the graphene sheet.
Graphene, first isolated experimentally less than three years ago, is
a two-dimensional honeycomb lattice of carbon atoms, and, structurally,
is related to carbon nanotubes (tiny hollow tubes formed by rolling up
sheets of graphene) and buckyballs (hollow carbon molecules that form
a closed cage).
Scientifically, it has become a new model system for condensed-matter
physics, the branch of physics that deals with the physical properties
of solid materials. Graphene enables table-top experimental tests of a
number of phenomena in physics involving quantum mechanics and
relativity.
Bearing excellent material properties, such as high current-carrying
capacity and thermal conductivity, graphene ideally is suited for
creating components for semiconductor circuits and computers. Its
planar geometry allows the fabrication of electronic devices and the
tailoring of a variety of electrical properties. Because it is only
one-atom thick, it can potentially be used to make ultra-small devices
and further miniaturize electronics.
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