This is worth a slow read as it points us to the future in electronic
manipulation. What is been described here is what is been observed
in UFOs.
In the future, our computer will be a magazine like object that can
be rolled up and activated with a light pen. More likely it will
simply be a sheet stuck on a wall that we activate personally with
our light pen. The sheer weight of what is now coming is stunning.
Again this is all a while down the line, but that means beginning in
about five years and then rapidly accelerating.
Light might prompt
graphene devices on demand
by Staff Writers
Houston TX (SPX) Oct 11, 2012
Rice University
researchers are doping graphene with light in a way that could lead
to the more efficient design and manufacture of electronics, as well
as novel security and cryptography devices.
Manufacturers
chemically dope silicon to adjust its semiconducting properties. But
the breakthrough reported in the American Chemical Society journal
ACS Nano details a novel concept: plasmon-induced doping of graphene,
the ultrastrong, highly conductive, single-atom-thick form of carbon.
That could facilitate
the instant creation of circuitry - optically induced electronics
- on graphene patterned with plasmonic antennas that can
manipulate light and inject electrons into the material to affect its
conductivity.
The
research incorporates both theoretical and experimental work to show
the potential for making simple, graphene-based diodes and
transistors on demand.
The work was done by
Rice scientists Naomi Halas, Stanley C. Moore Professor in Electrical
and Computer Engineering, a professor of biomedical engineering,
chemistry, physics and astronomy and director of the Laboratory for
Nanophotonics; and Peter Nordlander, professor of physics and
astronomy and of electrical and computer engineering; physicist Frank
Koppens of the Institute of Photonic Sciences in Barcelona, Spain;
lead author Zheyu Fang, a postdoctoral researcher at Rice; and their
colleagues.
"One of the major
justifications for graphene research has always been about the
electronics," Nordlander said. "People who know silicon
understand that electronics are only possible because it can be p-
and n-doped (positive and negative), and we're learning how this can
be done on graphene.
"The
doping of graphene is a key parameter in the development of graphene
electronics," he said. "You can't buy
graphene-based electronicdevices now, but there's no
question that manufacturers are putting a lot of effort into it
because of its potential high speed."
Researchers have
investigated many strategies for doping graphene, including attaching
organic or metallic molecules to its hexagonal lattice. Making it
selectively - and reversibly - amenable to doping would be like
having a graphene blackboard upon which circuitry can be written and
erased at will, depending on the colors, angles or polarization of
the light hitting it.
The ability to
attach plasmonic nanoantennas to graphene affords just such a
possibility. Halas and Nordlander have considerable expertise in the
manipulation of the quasiparticles known as plasmons, which can
be prompted to oscillate on the surface of a metal. In earlier work,
they succeeded in depositing plasmonic nanoparticles that act as
photodetectors on graphene.
These
metal particles don't so much reflect light as redirect its energy;
the plasmons that flow in waves across the surface when excited emit
light or can create "hot electrons" at particular,
controllable wavelengths. Adjacent plasmonic particles can interact
with each other in ways that are also tunable.
That effect can easily
be seen in graphs of the material's Fano resonance, where the
plasmonic antennas called nonamers, each a little more than 300
nanometers across, clearly scatter light from a laser source except
at the specific wavelength to which the antennas are tuned.
For the Rice
experiment, those nonamers - eight nanoscale gold discs arrayed
around one larger disc - were deposited onto a sheet of graphene
through electron-beam lithography. The nonamers were tuned to scatter
light between 500 and 1,250 nanometers, but with destructive
interference at about 825 nanometers.
At the point of
destructive interference, most of the incident light energy is
converted into hot electrons that transfer directly to the graphene
sheet and change portions of the sheet from a conductor to an n-doped
semiconductor.
Arrays of antennas can
be affected in various ways and allow phantom circuits to materialize
under the influence of light. "Quantum dot and plasmonic
nanoparticle antennas can be tuned to respond to pretty much any
color in the visible spectrum," Nordlander said. "We can
even tune them to different polarization states, or the shape of a
wavefront.
"That's the magic
of plasmonics," he said.
"We can tune the
plasmon resonance any way we want. In this case, we decided to do it
at 825 nanometers because that is in the middle of the spectral range
of our available light sources. We wanted to know that we could send
light at different colors and see no effect, and at that particular
color see a big effect."
Nordlander said he
foresees a day when, instead of using a key, people might wave a
flashlight in a particular pattern to open a door by inducing the
circuitry of a lock on demand. "Opening a lock becomes a
direct event because we are sending the right lights toward the
substrate and creating the integrated circuits. It will only answer
to my call," he said.
Rice co-authors of the
paper are graduate students Yumin Wang and Andrea Schlather, research
scientist Zheng Liu, and Pulickel Ajayan, the Benjamin M. and Mary
Greenwood Anderson Professor in Mechanical Engineering and Materials
Science and of chemistry. The research was supported by the Robert A.
Welch Foundation, the Office of Naval Research, the Department of
Defense National Security Science and Engineering Faculty Fellows
program and Fundacio Cellex Barcelona.
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