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Graphene Transistors Do Triple Duty in Wireless Communications


Triple transistor: Single graphene transistors like this one can be made to operate in
three modes and perform functions that usually require multiple transistors in a
circuit.

Credit: Alexa
nder Balandin

Communications

Graphene Transistors Do Triple Duty in Wireless Communications

A single graphene transistor that does the job of many conventional ones could lead to
compact chips for cell phones.



Friday, October 22, 2010



By Katherine Bourzac

Graphene
's potential was recognized earlier this month when those who first studied it
in the lab won the 2010 Nobel Prize in Physics. But researchers are just beginning to
figure out how to

take advantage of the novel carbon material in electronic devices.

Researchers have already made
blisteringly fast

graphene
tra
nsistors
. Now they've
used graphene to make a transistor that can be switched between three different
modes of operation, which in conventional circuits must be performed by three
separate transistors. These configurable transistors could lead to more com
pact chips
for sending and receiving wireless signals.

Chips that use fewer transistors while maintaining all the same functions could be less
expensive, use less energy, and free up room inside portable electronics like smart
phones, where space is tight.

The new graphene transistor is an analog device, of the
type that's used for wireless communications in Bluetooth headsets and radio
-
frequency identification (RFID) tags.

Graphene's perfect structure at the atomic level provides smooth sailing for electro
ns,
and the material conducts electrons better than any other materials do at room
temperature. So far, it's been used to make transistors that switch at about 100
gigahertz, or 100 billion times per second, 10 times faster than the best silicon
transistor
s; it's predicted the material could be made into transistors that are even
1,000 times faster than this. And because graphene is smooth and flat, it should be
compatible with the chip
-
making equipment at semiconductor fabs.

But graphene offers other prope
rties besides just being a great conductor of electrons,
says
Kartik Mohanram
, professor of electrical and computer engineering at Rice
University. It's also possible to change the behavior of a

graphene transistor on the
fly, something that can't be done with conventional silicon transistors. The transistors
that make up conventional silicon logic circuits can only behave in one of two ways,
called "n" for negative or "p" for positive
--
they eith
er control the flow of electrons or
the flow of "holes," or positive charges. Whether a conventional transistor is p
-
type or
n
-
type is determined during fabrication. But graphene is ambipolar: it can conduct
both positive and negative charges.

Mohanram has

designed a transistor that can be changed, and has made and tested it
with
Alexander Balandin
, professor of materials science and engineering at the
University of California, Riv
erside. By changing the voltage applied to a sheet of
graphene using three electrical gates, they could switch the graphene between three
different modes: n
-
type, p
-
type, and a mode where it conducted positive and negative
charge equally. This triple
-
mode
transistor acts as an amplifier and can be used to
encode a data stream by changing the frequency and the phase of a signal. Changes in
phase and frequency are used to encode data in telecommunications devices such as
Bluetooth headsets and RFID tags.

Moha
nram and Balandin's device is the first that can do this level of signal processing
in a single transistor. Usually such signaling requires multiple transistors. Their
transistor is a proof
-
of
-
concept device, but Mohanram says it demonstrates what
might be

possible with graphene.

Other groups have demonstrated multimode transistors using graphene, carbon
nanotubes, and organic molecules. The researchers say that the new graphene triple
-
mode circuit can be controlled better than those devices.

Control is cri
tical when designing transistors that are ambipolar, says
Subhasish
Mitra
, professor of electrical engineering and computer science at Stanford
University. "People used to consider ambipolarity a

bad thing" because it's typically
difficult to control how an ambipolar transistor will behave, which makes it difficult
to use them at all, he says.

Mitra notes that the benefits shown at the single
-
transistor level must now be
demonstrated in systems. T
he electrical gates needed to control the behavior of arrays
of ambipolar transistors might end up making circuits much harder to design and
fabricate. "Now that they have shown that they can do this, we need to see what
benefit it brings at a system level
," he says.

Balandin and Mohanram are now working on graphene circuits to test the benefits of
ambipolarity at a higher level. They're also changing the design of the transistors
themselves to make them more efficient.

No one has yet published any articles

on the creation of integrated circuits made of
graphene transistors, but Balandin says researchers are now on the verge of putting it
all together. As materials scientists and device fabricators work on overcoming the
challenges of working with graphene,
says Mohanram, circuit designers should keep
pace with them and think creatively about ambipolarity and other possibilities opened
up by graphene and other nanomaterials. "New designs and new ways of thinking can
lag behind the development of new materials
," he says.



Making Graphene Nanomachines Practical


Machine making:

A transparent sheet of graphene is stretched over the surface of
this silicon wafer. The
graphene can oscillate over holes in the silicon beneath, acting
as a nanomechanical device called a resonator.

Credit: ACS/Nano Letters

Computing

Making Graphene Nanomachines Practical

Graphene devices could make extremely sensitive sensors and superfas
t electronic
switches for consumer electronics.



Wednesday, December 1, 2010



By Katherine Bourzac

Many of today's consumer electronics rely on microscopic machines. These tiny
devices are found in smart
-
phone motion sensors, inkjet printheads, and the switc
hes
that activate some display pixels, to name just a few components.

Shrinking these electromechanical machines down to the nanoscale would enable new
devices, such as extremely sensitive chemical sensors, incredibly precise
accelerometers, and super
-
fast

integrated circuit switches. In an important step toward
this goal, researchers at Cornell University have made large arrays of nanoscale
resonators using graphene.

An atom
-
thin form of carbon called graphene is among the most promising materials
for mak
ing nanoelectromechanical systems (NEMS). Graphene is the strongest known
material, and the most electrically conductive. Graphene's atom
-
thin size means it is
also incredibly lightweight and can move very fast. Cornell physics professor
Paul
McEuen

says graphene can be used to build large numbers of nanodevices with
equipment developed for etching silicon chips on flat wafers. But building mech
anical
nanomachines from graphene is challenging, and most of the devices created so far
have been one
-
offs.

McEuen and fellow Cornell professor
Harold Craighead

have now sh
own that they
can make graphene nanodevices called resonators on the surface of a silicon wafer.
Each resonator is made of a film of graphene that oscillates back and forth, like a
trampoline moving up and down, in response to a mechanical force applied to

its
surface or to an electrical field.

The Cornell group first etched trenches into the surface of a silicon wafer. They then
topped the wafer with a film of graphene grown on top of copper. The graphene sticks
to the surface of the silicon wafer like pla
stic cling wrap would. The researchers
finally add electrical contacts to the graphene to complete the resonators. The work is
described online in the journal
Nano Letters
.

"We're making large numbers of identical resonators, which demonstrates a transitio
n
from a lab experiment to a technology," says McEuen. Previous nanoresonators made
at this scale were either much thicker and less sensitive, or they had to be made one at
a time. "The two major obstacles in implementing nanodevices are scale
-
up and
repro
ducibility in performance," says
Alex Zettl
, professor of physics at the
University of California, Berkeley. Ze
ttl has made similar devices from carbon
nanotubes, including a radio made from a single carbon nanotube. "Using single
-
layer
graphene allows many devices to be made in one shot, with similar performance,"
Zettl says.

Graphene nanoresonators could make ver
y sensitive chemical detectors or
accelerometers. The suspended graphene films respond dramatically when any weight
is added

even just a molecule or an atom. "It couples very strongly to the outside
world," which makes for a good sensor, says McEuen.

Rod Ruoff
, professor of mechanical engineering at the University of Texas at Austin,
who pioneered the graphene growth
-
and
-
transfer technique used by the Cornell group,
says this work demonstrates
that this type of graphene performs well in
nanomechanical systems. But Ruoff says he sees room for improvement in the
performance of the resonators.

The Cornell researchers are now working to push the graphene resonators to their
ultimate performance limi
ts. The crystalline structure of graphene, which determines
its strength and electrical conductivity, is not perfect in the Cornell devices made so
far.

The researchers also hope to take advantage of quantum effects that occur at the
nanoscale. This could
improve their sensitivity, McEuen says.












Writing Circuits on Graphene


Hot wire:

An AFM tip heated to over 150 °C can etch an insulating
graphene oxide
surface to create thin conductive nanoscale wires.

Credit: Debin Wang, Georgia Tech

Computing

Writing Circuits on Graphene

A heated AFM tip can draw nanometers
-
wide conductive lines on graphene oxide.



Tuesday, June 15, 2010



By Prachi Patel

Using a heated atomic force microscope tip, researchers have drawn nanoscale
conductive patterns on insulating graphene oxide. This simple trick to control
graphene oxide's conductivity could pave the way for etching electronic circuits into
the carbon ma
terial, an important advance toward high
-
speed, low
-
power, and
potentially cheaper computer processors.

Graphene, an atom
-
thick carbon sheet, is a promising replacement for silicon in
electronic circuits, since it transports electrons much faster. IBM rese
archers have
already
made

transistors
, the building blocks of electronic circuits, with graphene t
hat
work 10 times faster than their silicon counterparts. But to make these transistors,
researchers first have to alter the graphene's electronic properties by cutting it into
thin ribbons, which are then incorporated into devices. Researchers have made t
hese
nanoribbons with lithography, with chemical
solution
-
based

processes, or by
unzipping

carbon
nanotubes.

In the new
Science

paper, researchers at the Georgia Institute of Technology and the
U.S. Naval Research Laboratory instead "write" such nanoribbons on a s
urface rather
than cutting graphene. The researchers start with a graphene oxide sheet, which
doesn't conduct electric current. When they pull an AFM tip heated to between 150 °C
and 1060 °C across the sheet, oxygen atoms are shed at the spots that the tip

touches.
This leaves behind lines of almost
-
pure graphene that are 10,000 times more
conductive than the surrounding graphene oxide.

"It's a fast, reproducible technique, it's one
-
step, it's simple," says Paul Sheehan, who
led the work at the
Naval Research Laboratory
. "Instead of putting down resist and
trying to cut graphene in different ways, you can use local heat and write the lines
exactly where you want them." Sheehan says that an array of thousa
nds of AFM tips
could sketch circuits on graphene oxide at the same time.

Lithographic methods to make nanoribbons are cumbersome and expensive, says
Jing
Guo
, an electrical and computer engineering
professor at the University of Florida in
Gainesville. These methods can also create ribbons with rough edges, which affect
graphene's electronic properties and result in low
-
quality transistors. "This is a new
way to [make nanoribbons] that's very simple
and reliable and potentially scalable to
large scale," he says. "You basically have a paper and take a pencil to scratch it, and
you have a very narrow line."

The researchers wrote lines as narrow as 12 nanometers across and at speeds of up to
0.1 millimet
ers per second. The writing speed increased with temperature. "It is
exciting to see that this conversion can be done and controlled at the nanoscale," says
Yu
-
Ming Lin
, a nanos
cale science and technology group researcher at IBM's Watson
Research Center in Yorktown Heights, NY. "This is an important step for graphene
-
based [electronics]."

Starting with graphene oxide sheets rather than graphene is easier and cheaper, says
Elisa Riedo
, a physics professor at Georgia Tech who led the work with Sheehan.
Pristine graphene sheets are typically obtained by mechanically separating flakes from
graphite or

by growing graphene on two
-
inch silicon carbide wafers. "Graphene oxide
was cheaper to produce in large areas compared to graphene," Riedo says. "It's a
different path to arrive to graphene."

The researchers plan to make transistors using their technique,

but they might need
additional processing first, says
Yanwu Zhu
, a graphene researcher at the University
of Texas at Austin. For one thing, they will have to find a way to remove gr
aphene
oxide remnants from the conductive ribbons.














Making Graphene More Practical


Bigger, better graphene:

A new way to coat large areas of s
ilicon with single
-
layer
sheets of graphene makes it easy to fabricate an array of field
-
effect transistors by
depositing gold electrodes on top of the graphene. The SEM image (bottom) shows
graphene spanning the seven
-
micrometer gap between the source and

drain
electrodes.

Credit: Yang Yang Laboratory, UCLA

Computing

Making Graphene More Practical

A novel process yields big pieces of single
-
ply graphene for smaller, faster
electronics.




Tuesday, November 18, 2008



By Prachi Patel

Researchers at the Univer
sity of California, Los Angeles, have found a simple way to
make large pieces of the carbon material graphene. Graphene, a flat, one
-
atom
-
thick
sheet of carbon, can transport electrons at very high speeds, making it an attractive
material for electronic de
vices. But producing sufficient quantities of large, uniform
single
-
layer sheets of graphene has been a challenge. So far, processes to make
graphene create small quantities of graphene flakes or films made of overlapping
pieces.

Using the new method, pres
ented online in
Nature Nanotechnology
, the researchers
report making single
-
layer 0.6
-
nanometer
-
thick pieces that are tens of micrometers
wide. Materials
-
science and engineering professor
Yang
Yang

and his colleagues
deposit the sheets on silicon wafers to make prototype field
-
effect transistors.

Testing at least 50 such transistors, the researchers found that the devices had an
output current of a few milliamperes. That is 1,000 times higher
than the output
current of the devices that others have recently reported while using similar
techniques to make graphene. "We believe this is a game
-
changing approach which
will significantly improve graphene electronics in the future," Yang says.

Electr
ons flow through graphene sheets tens of times faster than they flow in silicon.
The material could lead to electronic devices that are smaller, faster, and less power
hungry than are those made of silicon. Thin and transparent, graphene is also a
promisin
g replacement for the indium tin oxide electrodes and the silicon thin
-
film
transistors used in flat
-
panel displays.

The easiest way to make single sheets of graphene is by using adhesive tape to peel
graphene flakes off of pieces of graphite, which is a s
tack of multiple graphene layers.
This process results in a very small amount of tiny flakes of graphene. The pieces
would have to be much larger for any practical use. "If you can coat an entire silicon
wafer with a single sheet of graphene, then you can
do lithography or patterning and
have little devices," says
James Tour
, a chemistry professor at Rice University.

About two years ago, researchers came up with a
chemical method

that yields larger
graphene pieces. They oxidize graphite to make graphite oxide and dissolve it in
water. The oxygen atoms pry apart the individual graphene sheets, which get
dispersed in the solution
. After the researchers deposit the sheets on a substrate, the
oxygen is removed using another chemical or by heating.

Manish Chhowalla
, a materials
-
science and engineering professor at Rutgers
Uni
versity, has made one
-
to
-
two
-
nanometer
-
thick films with
this method
. He uses
vapors of a chemical called hydrazine to remove the oxygen groups from the
deposited film. The fil
ms, made of slightly overlapping graphene pieces, are a few
centimeters wide.

Yang points out that the quality of the sheets made so far has not been very good.
Because the graphene sheets are deposited on a substrate first, many oxygen groups
get trapped

between the sheets and the substrate underneath and are not removed.
"These are detrimental to electrical properties," he says.

Yang and his colleagues have simplified the method. They dissolve graphite oxide
pieces in pure hydrazine. This splits apart th
e individual graphene sheets and gets rid
of nearly all the oxygen groups in a single step. The researchers then deposit the
pieces on a silicon wafer. They could also deposit the flakes on flexible surfaces.

"The main contribution is that they've figured

out a better way of [removing oxygen
groups]," Chhowalla says.

The researchers uniformly cover large areas of silicon wafers about 1.5 centimeters in
length and width with graphene sheets. Then they deposit gold electrodes on top of
the flakes to make fie
ld
-
effect transistors.

The researchers are working to further improve the quality of the graphene sheets.
Pure, flat graphene sheets have a thickness of 0.34 nanometers. The 0.6
-
nanometer
thickness of the sheets that the researchers make implies that a fe
w oxygen groups
remain stuck to the graphene. "So it still might not be as good as the graphene you
want, but it's getting close," Tour says. "It's certainly good enough for lots of
devices."

Researchers now need to refine the process so that they can cove
r even larger areas
with single graphene sheets, Tour adds. That would be key for practically using
graphene in electronic devices. "What you want to be able to do is cover a whole 12
-
inch wafer with graphene cleanly," he says. "The Intels won't touch it u
ntil you can do
that."



















Biomedicine

Graphene Could Improve DNA Sequencing

The atom
-
thick material may be ideal for a new sequencing technique.



Thursday, August 19, 2010



By Prachi Patel

Layers of graphene that are only as thick as an atom
could help make human DNA
sequencing faster and cheaper. Harvard University and MIT researchers have shown
that sheets of graphene could be a big improvement over membranes that are
currently used for
nanopore sequencing
--
a technique that promises to speed up and
simplify the sequencing of long strands of DNA.

Today's sequencing techniques involve chopping up DNA, making many copies of
the pieces, and reading fluorescent molecules attached
to them. This approach takes
days and costs tens of thousands of dollars. In contrast, nanopore sequencing could, in
theory, parse an entire human genome in a few hours.

Nanopore sequencing involves
pulling

a DNA strand through a tiny hole in a
membrane that's suspended in a salt solution with a voltage applied across it. Ions
moving from one side of the membrane to the other create an electric current. As each
of four different DNA bases p
asses through the pore, the current strength decreases to
a different extent, making it possible to rapidly sequence the bases.

The nanopores currently used for DNA sequencing are typically made from bacterial
proteins or are etched in silicon
-
nitride memb
ranes. Such membranes are 20 to 30
nanometers thick. But since the distance between two DNA bases is 0.5 nanometers,
40 to 60 bases could be stuck in the pore at a time.

A thinner membrane, such as graphene, might allow for more accurate base
identificati
on. A single layer of graphene is just one nanometer thick. It's "the thinnest
membrane that has ever been applied to this problem," says
Jene Golovchenko
, a
physics professor at Harvard who l
ed the new work, published in
Nature

this week.

The researchers create their membrane by placing a graphene flake over a 200
-
nanometer
-
wide opening in the middle of a silicon
-
nitride surface. Then they drill a
few pores, just nanometers wide, in the graph
ene with an electron beam. The
membrane is finally immersed in a salt solution that's in contact with silver electrodes.
The researchers observed dips in the current when a DNA strand passed through the
pore, showing that the method could eventually be use
d to identify DNA bases.

Two other research groups have demonstrated similar feats recently:
one

group at the
Kavli Institute of Nanoscience and the
other

at the University of Pennsylvania. These
advances were both published in the journal
Nano Letters

in July.

Identifying individual DNA bases as they pass through the pore will take much more
work, however. Eac
h of the four different DNA bases should block the current
passing through the pore by a different amount. Any device should be able to
distinguish these varying amounts. But doing that will mean precisely controlling the
speed with which DNA flies through

the pore. Such control is the biggest hurdle to
making nanopore sequencing practical.

In the
Nature

paper, each DNA molecule, containing thousands of bases, passes
through the pore in hundreds of microseconds (about four nanoseconds per base). To
read a s
ingle base, one at a time, would mean the strand would have to be in the pore
more than 1,000 times longer, says
John Kasianowicz
, a biophysicist at the Nat
ional
Institute of Standards and Technology who invented nanopore sequencing.
Kasianowicz works with natural membranes and pores made from bacterial proteins.
These can hold molecules for tens of milliseconds, but are less stable than silicon
nitride and g
raphene.

"They've taken nanopore technology to the next level," he says of the recent graphene
efforts. "Making solid
-
state nanopores was a great idea, and doctoring them with
graphene is a great first step." But he adds: "To be able to sequence, you need
to be
able to control the flow of DNA through it and slow it down."
























Bigger, Stretchier Graphene


Big and bendy: A transparent gr
aphene film, two centimeters on each side, stretches
and flexes when transferred to a rubber stamp. The stamp can be used to deposit the
film on any substrate.

Credit: Ji Hye Hong

Computing

Bigger, Stretchier Graphene

High
-
quality, clear graphene films a
re a leap toward bendable OLED displays.



Thursday, January 15, 2009



By Prachi Patel

Korean researchers have found a way to make large graphene films that are both
strong and stretchy and have the best electrical properties yet. These atom
-
thick sheets
of c
arbon are a promising material for making flexible, see
-
through electrodes and
transistors for flat
-
panel displays. Graphene could also lead to foldable organic light
-
emitting diode (OLED) displays and organic solar cells. However, it has not been
easy fin
ding a way make large, high
-
quality sheets of graphene.

Researchers from the Sungkyunkwan University and the Samsung Advanced Institute
of Technology, in Suwon, Korea, have made centimeters
-
wide graphene films that are
80 percent transparent and can be ben
t and stretched without breaking or losing their
electrical properties. Others have made large graphene films using
simpler techniques
,
but the new films are 30 times more conduct
ive. In addition, it is easy to transfer the
new films onto different substrates. "We have demonstrated that graphene is one of
the best materials for stretchable transparent electronics," says
Byung Hee Hong
, who
led the work, which is published in
Nature
.

Graphene is an excellent conductor, and it transports electrons tens of times faster
than silicon does. It could replace the brittle indium tin oxide (ITO) electrodes that are
currently u
sed in displays, organic solar cells, and touch screens. Graphene transistors
could also
replace

silicon thin
-
film transistors, which are not transparent and are hard
to fabricate
on plastic.

The easiest way to make tiny flakes of high
-
quality graphene is to peel off graphene
layers from graphite (which is, essentially, just a stack of graphene sheets). Last year,
a group led by Rutgers University materials
-
science and engineering p
rofessor
Manish Chhowalla

devised a
method

for making centimeters
-
scale pieces for practical
applications. The resear
chers dissolved graphite oxide in water, creating a suspension
of individual graphene
-
oxide sheets, which they deposited on top of a flexible
substrate.

The Korean researchers use a method called chemical vapor deposition. First, they
deposit a 300
-
nanomet
er
-
thick layer of nickel on top of a silicon substrate. Next, they
heat this substrate to 1,000 Cº in the presence of methane, and then cool it quickly
down to room temperature. This leaves behind graphene films containing six to ten
graphene layers on top

of the nickel. By patterning the nickel layer, the researchers
can create patterned graphene films.

Others, such as MIT electrical
-
engineering professor
Jing Kong
, are worki
ng on
similar approaches

to making large graphene pieces. But the Korean researchers have
taken the work a step further, transferring the films to flexible substra
tes while
maintaining high quality. The transfer is done in one of two ways. One is to etch away
the nickel in a solution so that the graphene film floats on its surface, ready to be
deposited on any substrate. A simpler trick is to use a rubber stamp to t
ransfer the
film.

Columbia University physics professor
Philip Kim
, who is a coauthor of the new
paper, says that chemical vapor deposition is one of the cheapest ways to make
quality graphene
on a large scale and should be compatible with existing
semiconductor fabrication technologies. Right now, the researchers can make four
-
inch pieces, but Hong says that they could easily scale up the process.

The new graphene films are less defective than

ones made in the past, Hong says,
which is why they are about 30 times more conductive and have about 20 times
higher mobility than do previous graphene sheets. "The conductivity is sufficient for
some entry
-
level applications in small LCD displays and to
uch
-
panel displays," says
Yang Yang
, a materials
-
science and engineering professor at the University of
California, Los Angeles. However, he adds, the conductivity would still need to be 10
ti
mes better in order to replace ITO in organic solar cells and OLEDs.

Many other materials are being considered for transparent, bendable electronics.
Carbon nanotubes could be a tough competitor. For example, researchers are making
headway with creating
flexible nanotube transistors
, and
Unidym
, based in Menlo
Park, CA, will soon start selling nanotube
-
coated plastic films, which c
ould be used
instead of ITO coatings on displays.

Others have made flexible, see
-
through transistors using indium
-
oxide
coatings
, or
zinc
-
oxide and indium
-
oxide
nanowires
. Meanwhile, University of Michigan
researchers have made
transparent electrodes

using a grid of very th
in metal wires.

Graphene's advantage could be its exceptional strength and high mobility (predicted
to be twice that of nanotubes). Tao He, a graphene researcher at Rice University, says
that the conductivity and mobility values of the new films are impres
sive. "I didn't see
any [other work] similar or comparable to this one," he says, adding that the new
work could make large
-
scale, low
-
cost manufacture of flexible graphene electronics
possible.


A Step Toward Superfast Carbon Memory


Ones and zeros:

By depositing a ferroelectric material on top of graphene,
researchers have coaxed graphene into holding on to two different levels of electrical
conductivit
y, which could serve as bits 1 and 0 in computer memory.

Credit: Barbaros Özyilmaz, National University of Singapore

Computing

A Step Toward Superfast Carbon Memory

Graphene could make computer hard drives denser and speedier.



Wednesday, April 1, 2009



By

Prachi Patel

Graphene, a flat sheet of hexagonally arranged carbon atoms, can transport electrons
very quickly. This has made it a promising material for
high radio
-
frequency

log
ic
circuits, transparent
electrodes

for flexible flat
-
panel displays, and high
-
surface
-
area
electrodes for
ultracapacitors
.

Now researchers at the National University of Singapore have made computer
memory devices using graphene. This is the first step toward memory that could be
much denser and faster than the magnetic memory used in today's hard drive
s. The
researchers have made hundreds of prototype graphene memory devices, and they
work reliably, according to
Barbaros Özyilmaz
, the physics professor who led the
work presented at

a recent American Physical Society meeting in Pittsburgh.
"Graphene is going to change the electronic industry," he says. "What was missing
was a way to use graphene as a memory element. So far there was almost no interest
because it wasn't [thought] doab
le."

The key to making memory elements is a material that can have two different states.
That is because computer memory is stored as two bits: 1 and 0. Hard drives also need
to be nonvolatile, which means the material should be able to hold on to those st
ates
without requiring power. Today's hard disks are made of magnetic cobalt alloys, and
they store bits as one of two magnetic orientations of a small area on the disk.

Özyilmaz and his colleagues came up with an easy way to make graphene hold its two
di
fferent levels of conductivity, or resistance. Switching between these levels requires
applying and removing an electric field. The researchers deposit a thin layer of a
ferroelectric material on top of the graphene. Ferroelectrics have an intrinsic electr
ic
field, and applying a voltage changes the direction of the field. The ferroelectric's
field helps graphene sustain its conductivity. And, Özyilmaz explains, "we can change
the polarization of the ferroelectric, which in turn changes the conductivity of
graphene."

The new memory idea is "thrilling because it's very simple," says
Andre Geim
, professor of
physics at the University of Manchester, UK, who first isolated graphene sheets from
graphite.

"Ferroelectrics are well known. It's also known that an electric field changes
graphene's resistivity by a factor of typically 10. [Özyilmaz] combines those two very well
-
known facts."

Graphene memory would have significant advantages over today's magneti
c memory.
Bits could be read 30 times faster because electrons move through graphene quickly.
Plus, the memory could be denser. Bit areas on hard disks are currently a few tens of
nanometers across. At densities of 1 terabit per square inch, they will be a
bout 25
nanometers across, too small to hold their magnetization direction. With graphene,
bits could shrink to 10 nanometers or even smaller. In fact, the memory devices would
work better with smaller graphene areas. Stanford University researchers have s
hown
that cutting graphene into
ribbons

a few nanometers wide enhances the difference
between its two conductivity states.

The new prototype memory devices, however, are rudiment
ary. The Singapore
researchers take graphene flakes that are 2 micrometers wide and place them on
silicon. Then they deposit gold electrodes and add a top layer of the ferroelectric.
Özyilmaz says that the device readout time is five times faster than curr
ent magnetic
memory. The researchers can switch graphene between its two conductivities 100,000
times
--
practical memory devices go through millions of cycles.

This is not the first attempt at making graphene memory. In an August 2008
IEEE
Electron Device L
etters

paper, researchers at the German nanotechnology company
AMO

described devices that could switch between two conductivity states using an
electric field. "We could cycle 20 to 30 times, but not tens of t
housands of times,"
says physicist Max Lemme, lead author of the paper. Lemme speculates that hydroxyl
groups and hydrogen attached to the graphene surface detach when current is applied,
changing the sheet's conductivity. Why the graphene sheets nonethele
ss maintain their
conductivity when the power is switched off is not well understood.

Geim, who was involved in the AMO work, says that "when you don't know the
mechanism, it's hard to judge whether you can in principle make this mechanism
reliable to be
reproducible on many devices in an identical manner." With the
Singapore researchers' approach, however, "we know the physics behind it and its
limitations. With well
-
known fundamentals behind it, it looks like a very good idea."










Detecting Light w
ith Graphene


Light detector:

A scanning
-
electron
-
microscope image and an optical image (inset)
show a high
-
bandwidth graphene photodetector. Metal conta
cts deposited on the
graphene create an electric field that separates electrons, allowing the device to detect
light.

Credit: IBM T. J. Watson Research Center

Computing

Detecting Light with Graphene

The atom
-
thick carbon material could have optoelectroni
c applications.



Tuesday, October 13, 2009



By Prachi Patel

Researchers have explored graphene's extraordinary electronic properties for
numerous applications over the past few years, from
superfast transistors

to extremely
dense
memory chips
. Now, for the first time, IBM researchers are exploiting
graphene's unique properties for optoelectronics, using graph
ene sheets to make
photodetectors.

Light detectors are typically made using III
-
V semiconductors
--
materials made of
multiple elements such as gallium and phosphorus. When light hits these materials,
each photon absorbed creates an electron
-
hole pair, and t
he electrons are then shuttled
out of the material to produce an electrical current.

Graphene
--
a sheet of carbon atoms linked in a honeycomb structure
--
transports
electrons tens of times faster than III
-
V semiconductors. That means that graphene
photodete
ctors could work at extremely high frequencies, making them highly
efficient at detecting light and transporting the resulting electrons to an external
circuit. The material also absorbs wavelengths ranging from visible to infrared,
whereas thin layers of
III
-
V semiconductors don't absorb many infrared frequencies.

Graphene has already been used to make several kinds of transistors, including
ultrahigh
radio
-
frequency

devices. The

highly conductive atom
-
thick sheets could also
replace expensive and brittle indium tin oxide as the
electrode material

in flexible flat
-
panel displays and thin solar cells. Peop
le are also considering graphene for
ultracapacitor

electrodes and for dense and superfast
computer
memory
.

Yet despite all these electronic applications, many experts considered graphene less
than ideal for optical devices. This is because the electrons and holes generated by
incoming photons normally combine in graphene within tens of picoseconds, lea
ving
no free electrons for current. This also happens in a metal. But the speed with which
the charged particles travel in graphene is key, says
Phaedon Avouris
, manager for
nanometer sca
le science and technology at IBM's T. J. Watson Research Center and
the researcher who led the work, which is described in a paper published online in
Nature Nanotechnology
. "If we can have

some kind of an electric field to separate the
electron
-
hole pairs, we can collect them fast enough [for current]."

It is already known that when metal contacts are deposited on graphene, electric fields
are generated at the interface between the two mate
rials. So the researchers took
advantage of this field. Their device is a piece of multilayered graphene with metal
contacts on top. When they shine light near the contact, the field separates the
electrons and holes, and a current is generated.


Light detector
: A graphene photodetector takes advantage of the electric field that is
created at the interface between metal contacts (gold) and graphene. When
light falls
on graphene, the field helps to separate electrons from holes, leading to an electric
current.

Credit: IBM T. J. Watson Research Center

A single sheet of graphene absorbs 2.3 percent of the light falling on it, a significant
amount for a one
-
atom
-
thick material. "You have a photodetector that has a number
of advantages: it absorbs over a wide wavelength range, it's very fast, it has a high
absorbance, it's a single atomic layer," Avouris says. "This combination makes it
rather unique."

Ultrafa
st photodetectors could find use in future optical communications networks
with data rates beyond 40 gigabits per second; right now, optical networks have data
rates of about 10 gigabits per second. The photodetectors could also be used in optical
computer
s that compute with electrons but transfer data
using light

instead of sending
it over heat
-
prone copper wires. Fengnian Xia, a coauthor of the paper, says that
graphene would also

make a better detector for
terahertz radiation
, which has shown
promise for medical and security imaging.

"Graphene is a great material for electronics," says
Andre Geim
, a professor of
physics at the University of Manchester, U.K. "Very few people could think about
optoelectronics being of any interest with this material. This is like fresh

air."

The researchers get current in response to light pulses at a frequency of 40 gigahertz.
Frequencies higher than this are not possible with today's electronics, says Avouris,
but graphene could, in theory, enable photodetectors that work at frequenci
es even
higher than 0.5 terahertz.























Faster Graphene Transistors


Speedy carbon devices:

Researchers at HRL Laboratories create hi
gh
-
frequency
transistors on top of two
-
inch
-
wide graphene pieces by patterning metal electrodes
and depositing insulating aluminum oxide on top of the graphene.

Credit: Jeong
-
Sun Moon, HRL Laboratories

Computing

Faster Graphene Transistors

Graphene circu
its could lead to high
-
speed wireless devices and advanced weapons
detectors.



Wednesday, December 17, 2008



By Prachi Patel

A pair of research groups, working independently, report making graphene
-
based
transistors that work at the highest frequencies repor
ted to date. The new transistors
are a promising first step toward ultrahigh radio
-
frequency (RF) transistors, which
could be useful for wireless communications, remote sensing, radar systems, and
weapons imaging systems.

The reports come from researchers

at the IBM
T. J. Watson Research Center

in
Yorktown Heights, NY, and at the
HRL Laboratories

in Malibu, CA. The IBM
transistors work at frequ
encies up to 26 gigahertz. Both the IBM and HRL work was
funded by the U.S. military's Defense Advanced Research Projects Agency
(
DARPA
). Kostya Novoselov, a physicist and graphene researcher at the Univers
ity
of Manchester, in the U.K., says that the results are "a really big step forward to
demonstrating that high
-
frequency graphene transistors should work."

Graphene, a flat sheet of carbon atoms, is a promising material for RF transistors.
Typical RF tra
nsistors are made from silicon or more expensive semiconductors like
indium phosphide. In graphene, for the same voltage, electrons zip around 10 times
faster than in indium phosphide, or 100 times faster than in silicon.

Graphene transistors will also con
sume less power and could turn out to be cheaper
than those made from silicon or indium phosphide.
Yu
-
Ming Lin
, who led the work at
IBM, says that silicon technology is extremel
y mature, but graphene could "achieve
device performance that may never be obtained with conventional semiconductors."



The eventual goal of the DARPA program is to demonstrate an amplifier circuit for
signals with frequency greater than 90 gigahertz. The

circuit should be made using
transistors on an eight
-
inch
-
wide wafer employing processes compatible with the
current fabrication methods for silicon circuits.

Andre Geim
, a professor of physics
at the University of Manchester, who discovered
graphene and fabricated some of the
first graphene transistors
, says that even "90
gigahertz is really nothing for graphene. Th
e frequency could be 10 times higher
--
around the terahertz range." Such extremely high
-
frequency transistors would be
useful for terahertz imaging, which could detect hidden weapons.

The HRL researchers make their transistors on two
-
inch
-
wide graphene piec
es. They
grow these two
-
inch pieces by heating a silicon carbide wafer to extremely high
temperatures
--
over 1,200 °C. The silicon evaporates and leaves behind carbon atoms,
which arrange themselves in a single layer and form graphene. The researchers
fabri
cate the transistors by depositing insulating aluminum oxide and metal electrodes
on top of the graphene.

Lin and his colleagues at IBM use graphene made by peeling single graphene sheets
off graphite, which is a stack of graphene sheets. This gives small
but very high
-
quality flakes. As a result, the researchers can shrink transistor features, resulting in
devices that work at higher frequencies.

Many challenges remain in order for the researchers to meet DARPA goals. One is a
practical way to cover larger

areas with graphene. Jeong
-
Sun Moon, who led the HRL
efforts, says that even though the silicon carbide method results in subpar
-
quality
graphene, it has potential for evolving into an eight
-
inch wafer
-
scale process. "The
method would be crucial to gettin
g graphene to become a real technology," he says.
Others are also using
various

tricks to
make

wafer
-
size graphene for circuits.

"The achieved frequencies are very far from what is possible," Geim says.
Nevertheless, he believes that it shouldn't be too long before graphene transistors
exceed expectations and come close to their terahertz capacity.

"I personally believe
this is a done deal," he says. "The fundamentals are all there. Now it's down to
engineers to polish the processes involved."











Graphene Transistors that Can Work at Blistering Speeds


Speedy switches:

These arrays of transistors, printed on a silicon carbide wafer,
operate at speeds of 100 gigahertz.

Credit:
Science
/AAAS

Computing

Graphene Transistors that Can Work at Bliste
ring Speeds

IBM shows that graphene transistors could one day replace silicon.



Friday, February 5, 2010



By Katherine Bourzac

IBM has created graphene
transistors

that leave silicon ones in the dust. The prototype
devices, made from atom
-
thick sheets of carbon, operate at 100 gigahertz
--
meaning
they can switch on and off 100 billion times each second, about 10 times as fast as the
speediest

silicon transistors.

The transistors were created using processes that are compatible with existing
semiconductor manufacturing, and experts say they could be scaled up to produce
transistors for high
-
performance imaging, radar, and communications devices

within
the next few years, and for zippy computer processors in a decade or so.

Researchers have previously made graphene transistors using laborious
mechanical
methods
, for
example by flaking off sheets of graphene from graphite; the fastest
transistors made this way have reached speeds of up to
26 gigahertz
. Transistors made
using similar meth
ods have not equaled these speeds.

Growing transistors on a wafer not only leads to better performance, it's also more
commercially feasible, says
Phaedon Avouris
, leader of the

nanoscale science and
technology group at the IBM Watson Research Center in Ossining, NY where the
work was carried out.

Ultimately, graphene has the potential to replace silicon in high
-
speed computer
processors. As computers get faster each year, silico
n is getting closer and closer to its
physical limits, and graphene provides a promising potential replacement because
electrons move through the material much faster than they do through silicon. "Even
without optimizing the design, these transistors are
already 2.5 times better than
silicon," says
Yu
-
Ming Lin
, another researcher at IBM Watson who collaborated with
Avouris.

Other researchers have made very fast transistors using

expensive semiconductor
materials such as indium phosphide, but these devices only operate at low
temperatures. In theory, graphene has the material properties needed to let transistors
run at terahertz speeds at room temperature.

The IBM researchers grew

the graphene on the surface of a two
-
inch silicon
-
carbide
wafer. The process starts when they heat the wafer until the silicon evaporates,
leaving behind a thin layer of carbon, known as epitaxial graphene. This technique
has been used to make transistors

before, but the IBM team improved the process by
using better materials for the other parts of the transistor, in particular the insulator.

"Graphene's properties are very sensitive to its environment," says Lin. This is why
the IBM group focused on desig
ning a new insulating layer
--
the part of the transistor
that prevents short circuits. They found that adding a thin layer of a polymer between
the dielectric and the graphene improved performance. The work is described this
week in the journal
Science
.

Walter de Heer
, a professor of physics at Georgia Tech in Atlanta who pioneered
methods used to work with epitaxial graphe
ne, says the IBM device is a milestone
because of its speed and because it was made using practical fabrication techniques.
"This is not pie
-
in
-
the
-
sky stuff, this is real," he says. "This development is really
going to turn into a communications device no
t too long from now."

"One can apply the same processing technologies to get much closer to a product,"
says Avouris.
Last year
, the same IBM group, and an independent group at
HRL
Laboratories

in Malibu, CA, both made 10 gigahertz graphene transistors using an
involved method called mechanical exfoliation. This process involves peeling away
layers from a small piece of graphite until

a single, atom
-
thick sheet remains, then
setting that down on a substrate and carving it to form a transistor. The problem with
this approach is that it compromises graphene's electrical properties and is not
commercially scalable, says Avouris.

The first

applications of graphene transistors will likely be as switches and amplifiers
in analog military electronics. Indeed, the IBM group's work is supported in part by
the Defense Advanced Research Projects Agency. But the researchers say it will be
years bef
ore the company begins commercial development on carbon electronics.

De Heer notes that the IBM devices don't yet realize graphene's full potential. By
carefully controlling the growing conditions, his group has made graphene that
conducts electrons 10 tim
es faster than the material used by the IBM team. This
higher
-
quality graphene could, in theory, be used to make transistors that reach
terahertz speeds, though de Heer says many things could go wrong during scale
-
up.

Avouris says the IBM team will work to

improve its transistors' speed by
miniaturizing them. The ones it has made so far are 240 nanometers long, which is
relatively large
--
silicon electronic components are down to about 20 nanometers.
Avouris also believes that their performance could be impr
oved by making the
insulating layer thinner. "The next step is to try and integrate these transistors into a
truly operational circuit," he says.




Building Super
-
Fast Electronics Components


Graphene strips:

The zigzag
-
shaped graphene nanoribbons in this image are a
nanometer wide, 50 nanometers long.

Credit: Empa, Switzerland

Computing

Building Super
-
Fast Electronics Components

Making graphene with
clean edges will be key to using it for high
-
speed electronics.



Wednesday, July 21, 2010



By Nidhi Subbaraman

For years, researchers have touted graphene as the magic material for the next
generation of high
-
speed electronics, but so far it hasn't proved pr
actical. Now a new
way of making nanoscale strips of carbon
--
the building block of graphene
--
could
kick
-
start a shift toward superfast graphene components.

The new method, which involves building from the molecular scale up, comes from
researchers at the
Max Planck Institute for Polymer Research in Germany and Empa
in Switzerland. With atomic
-
level precision, the researchers made graphene
nanoribbons about a nanometer wide.

The molecule
-
thick carbon material called graphene outperforms silicon, which is
cu
rrently used in electronic components, in every way. It conducts electricity better
than silicon, it bends more easily, and it's thinner. Using graphene instead of silicon
could lead to faster, thinner, more powerful electronic devices. However, unless
gra
phene sheets are less than 10 nanometers wide and have clean edges, they lack the
electronic properties needed before manufacturers can use them for devices like
transistors, switches, and diodes
--
key components in circuitry.

The Swiss team fabricated the
se skinny graphene strips by triggering molecular
-
scale
chemical reactions on sheets of heated gold. This let the team precisely control the
width of the nanoribbons and the shape of their edge. Molecules were arranged into
long fibers on the gold surface.

When that surface was heated, adjacent strings linked
and fused to form ribbon structures about one nanometer across, with a uniform
zigzag edge.

"The beauty of that is that it can be done with atomic precision," says
Roman Fasel
,
the corresponding author on the study. "It's not cutting, it's assembling."

Other ways of making nanoribbons involve peeling strips of graphene from a larger
sheet, etching them with lit
hography, or unzipping cylinder
-
shaped carbon nanotubes.
But such nanoribbons are thicker and have random edges.

"In nanoribbons, he who controls the edges wins," says
James Tour
, a graphene expert
at Rice

University, who was not involved with the work. "There is no way yet to take
a big sheet of graphene and chop it up with this level of control."

"This type of nanoribbon would enrich and open up new possibilities for graphene
electronics," says
Yu
-
Ming Lin
, a researcher working on graphene
-
based transistors at
the IBM T. J. Watson Research Center in New York.

Graphene nanoribbons are still a long way from practical applicatio
n, says Tour. "The
next step is to make a handful of devices. That's not hard to do the big step is to orient
it en masse."

But the success of Fasel and his team's chemical method, Tour says, will encourage
more research into fine
-
tuning the steps so that

nanoribbons of this quality can be
produced on a large scale. For instance, researchers can now experiment with the finer
edge structure and electronic effects of the new nanoribbons, testing theories that, to
date, they could only simulate on computers.

"It points the direction rather than being a final result," says
Walter de Heer
, a
researcher at the Georgia Institute of Technology who has developed a way to grow
graph
ene on silicon chips. "It's a first step in a long chain of steps that will lead to
graphene electronics."
















Silicon's Long Good
-
bye


Na
noribbons:

Strips of indium arsenide have been chemically etched so that they
release from the surface beneath. They can then be transferred to silicon wafers to
make speedy, low
-
power transistors.

Credit: Nature Publishing Group

Computing

Silicon's Long

Good
-
bye

Researchers make transistors out of a material that's better than silicon.



Friday, November 19, 2010



By Katherine Bourzac

Sometime in the coming decades, chipmakers will no longer be able to make silicon
chips faster by packing smaller transisto
rs onto a chip. That's because silicon
transistors will simply be too leaky and expensive to make any smaller.

People working on materials that could succeed silicon have to overcome many
challenges. Now researchers at the University of California, Berkele
y, have found a
way past one such hurdle: they've developed a reliable way to make fast, low
-
power,
nanoscopic transistors out of a compound semiconductor material. Their method is
simpler, and promises to be less expensive, than existing ones.

Compound se
miconductors have better electrical properties than silicon, which means
that transistors made from them require less power to operate at faster speeds. These
materials are already in some expensive niche applications such as military
telecommunications eq
uipment, which gives them a leg up over more exotic potential
silicon replacements like graphene and carbon nanotubes.

But wafers of compound semiconductor materials are also very fragile and expensive,
"which is only okay where cost doesn't matter," says
Ali Javey
, associate professor of
electrical engineering and computer sciences at the University of California, Berkeley.
Compound semiconductors are on the market in exp
ensive communications chips for
the military, for example.

Researchers believe they can overcome this fragility and expense by growing
compound
-
semiconductor transistors on top of a supportive silicon wafer

a trick that
should be compatible with existing m
anufacturing infrastructure.

However, compound semiconductors cannot be grown on silicon

there's a mismatch
between the crystalline structures of the two materials that makes this difficult to do
well. The Berkeley group has now shown that transistors made

from compound
semiconductors can be grown on another surface and then transferred to a silicon
wafer. "That's a plausible path for dealing with the fact that compound
semiconductors are difficult to grow," says
Jesús del Alamo
, professor of electrical
engineering and computer science at MIT who was not involved with Javey's work.

The Berkeley researchers demonstrated their technique using indium arsenide. They
grow the material on top of a wafer
of gallium antimonide protected by a sacrificial
top layer of aluminum gallium antimonide. The wafer enables the growth of a high
-
quality, crystalline indium
-
arsenide film, and the sacrificial layer can then be
chemically etched away, releasing nanoscale i
ndium
-
arsenide strips. The researchers
pick up the nanoribbons with a rubber stamp and place them on top of the silicon
wafer. The silicon provides structural support for the indium arsenide. It's coated with
silicon dioxide, which will act as the insulato
r in the transistors. The transistors are
completed by laying down metal gates to bring electricity in and out.

Javey's group describes the performance of indium
-
arsenide transistors made in this
way in a paper published online last week in the journal
Nature
. The transistors,
which are 500 nanometers long, perform as well as compound
-
semiconductor
transistors made using more complex techniques, Javey says. And

the Berkeley
group's indium
-
arsenide transistors are much faster than their silicon equivalents,
while requiring less power

half a volt as compared with 3.3 volts. Their
transconductance

how responsive they are to changes in voltage

is eight times
better
than that for a silicon transistor this size. "Given how these devices were
prepared, this performance is quite impressive," says MIT electrical engineering
professor
Dmitri Anto
niadis
.

Javey notes that the process required to make the indium
-
arsenide transistors is
similar to that used to make a class of chips called silicon
-
on
-
insulator (SOI)
electronics, which require a slice of silicon to be placed on a wafer of another mater
ial
during manufacturing. For that reason he's named them XOI

anything on insulator.

The process for making the XOI devices at wafer
-
scale would be more complex than
SOI because it might require integrating several different types of materials built on
waf
ers of different sizes, says
Michael Mayberry
, director of components research at
Intel. "There are lots of ways that process could go wrong," he says. For the past three
ye
ars, Intel has been working on processes for growing compound semiconductors on
silicon wafers directly, by growing a buffer layer in between them. So far, they have
to use a very thick buffer that impedes the performance of the transistors, but
Mayberry s
ays they have proven that the concept can work.

The value of Javey's work, Mayberry says, is that it demonstrates that the indium
-
arsenide transistors perform well when shrunk down to the nanoscale. "We don't
know how these devices will behave," he says. T
heorists have made guesses, he says,
but at the nanoscale, unexpected quantum effects can crop up.

Javey plans to make the transistors much smaller and see whether they maintain their
performance. MIT's del Alamo and Antoniadis are trying to determine the
ultimate
scaling of compound
-
semiconductor transistors; the pair have made transistors that
are 30 nanometers long. "I would like to see what perfection of materials can be
achieved at a small scale," says Antoniadis.




TR10: Graphene Transistors


Credit: Maxwell Guberman, Georgia Tech

Who:

Walter de Heer, Georgia Tech
Definition:

Transistors based on graphene, a
carbon material one atom thick, coul
d have extraordinary electronic properties.

Impact:

Initial applications will be in ultrahigh
-
speed communications chips, with
computer processors to follow.

Context:

A number of academic researchers and several electronics companies are
studying graphen
e
-
based electronics.

Business

TR10: Graphene Transistors

A new form of carbon being pioneered by Walter de Heer of Georgia Tech could lead
to speedy, compact computer processors.



March/April 2008



By Kevin Bullis

The remarkable increases in computer speed

over the last few decades could be
approaching an end, in part because silicon is reaching its physical limits. But this
past December, in a small Washington, DC, conference room packed to overflowing
with an audience drawn largely from the semiconductor
industry, Georgia Tech
physic
s professor Walter de Heer described his latest work on a surprising alternative
to silicon that could be far faster. The material: graphene, a seemingly unimpressive
substance found in ordinary pencil lead.

Theoretical models

had previously predicted that graphene, a form of carbon
consisting of layers one atom thick, could be made into transistors more than a
hundred times as fast as today's silicon transistors. In his talk, de Heer reported
making arrays of hundreds of graph
ene transistors on a single chip. Though the
transistors still fall far short of the material's ultimate promise, the arrays, which were
fabricated in collaboration with MIT's Lincoln Laboratory, offer strong evidence that
graphene could be practical for f
uture generations of electronics.

Today's silicon
-
based computer processors can perform only a certain number of
operations per second without overheating. But electrons move through graphene with
almost no resistance, generating little heat. What's more,

graphene is itself a good
thermal conductor, allowing heat to dissipate quickly. Because of these and other
factors, graphene
-
based electronics could operate at much higher speeds. "There's an
ultimate limit to the speed of silicon
--
you can only go so far
, and you cannot increase
its speed any more," de Heer says. Right now silicon is stuck in the gigahertz range.
But with graphene, de Heer says, "I believe we can do a terahertz
--
a factor of a
thousand over a gigahertz. And if we can go beyond, it will be
very interesting."

Besides making computers faster, graphene electronics could be useful for
communications and imaging technolo
gies that require ultrafast transistors. Indeed,
graphene is likely to find its first use in high
-
frequency applications such
as terahertz
-
wave imaging, which can be used to detect hidden weapons. And speed isn't
graphene's only advantage. Silicon can't be carved into pieces smaller than about 10
nanometers without losing its attractive electronic properties. But the basic physic
s of
graphene remain the same
--
and in some ways its electronic properties actually
improve
--
in pieces smaller than a single nanometer.

Interest in graphene was sparked by research into carbon nanotubes as potential
successors to silicon. Carbon nanotubes,

which are essentially sheets of graphene
rolled up into cylinders, also have excellent electronic properties that could lead to
ultrahigh
-
performance electronics. But nanotubes have to be carefully sorted and
positioned in order to produce complex circui
ts, and good ways to do this haven't
been developed.
Graphene is far easier to work with.

In fact, the devices that de Heer announced in December were carved into graphene
using techniques very much like those used to manufacture silicon chips today.
"Th
at's why industry people are looking at what we're doing," he says. "We can
pattern graphene using basically the same methods we pattern silicon with. It doesn't
look like a science project. It looks like technology to them."

Graphene hasn't always looked
like a promising electronic material. For one thing, it
doesn't naturally exhibit the type of switching behavior required for computing.
Semiconductors such as silicon can conduct electrons in one state, but they can also
be switched to a state of very low

conductivity, where they're essentially turned off.
By contrast, graphene's conductivity can be changed slightly, but it can't be turned off.
That's okay in certain applications, such as high
-
frequency transistors for imaging and
communications. But such
transistors would be too inefficient for use in computer
processors.

In 2001, however, de Heer used a computer model to show that if graphene could be
fashioned into very narrow ribbons, it would begin to behave like a semiconductor.
(Other researchers, h
e learned later, had already made similar observations.) In
practice, de Heer has not yet been able to fabricate graphene ribbons narrow enough
to behave as predicted. But two other methods have been shown to have similar
promise: chemically modifying grap
hene and putting a layer of graphene on top of
certain other substrates. In his presentation in Washington, de Heer described how
modifying graphene ribbons with oxygen can induce semiconducting behavior.
Combining these different techniques, he believes,
could produce the switching
behavior needed for transistors in computer processors.

Meanwhile, the promise of graphene electronics has caught the semiconductor
industry's attention. Hewlett
-
Packard, IBM, and Intel (which has funded de Heer's
work) have al
l started to investigate the use of graphene in future products.




Ultradense, 3
-
D Data Storage


Cracking memory
: These scanning electron microscope ima
ges of the graphite strip
show an unaltered memory cell (top) and a cell that holds a bit of data (bottom), as
represented by the crack.

Credit: James Tour

Computing

Ultradense, 3
-
D Data Storage

Chips that use graphite show promise for storing more bits
than flash memory.



Wednesday, September 16, 2009



By Kate Greene

For decades, engineers have tweaked chip design to store more data in a smaller
space. But as chip components continue to shrink, engineers are looking at
alternatives to silicon that might pr
ovide better performance at small sizes. One
possible approach is to use carbon in the form of nanotubes
--
tiny, rolled
-
up sheets of
carbon atoms
--
or in the form of graphene
--
single, flat sheets of the atoms. However,
neither of these structures is easy to
mass
-
produce and to integrate onto chips using
existing manufacturing processes.

But now, researchers at Rice University in Houston have shown that graphene's
cousin, graphite, can be used to make a fast, high
-
density memory device with some
of the advanta
ges of flash memory typically found in memory cards and MP3 players.
Graphite, the same material found in pencils, comes in multiple sheets and flakes, and
can be deposited onto silicon using standard deposition processes, unlike nanotubes
and graphene.

Th
e graphite memory device, built by
James Tour
, professor of chemistry at Rice
University, and postdoctoral researcher Alexander Sinitskii, is similar to flash in that
it has no moving parts, which means it
's more robust than a magnetic hard drive. But
unlike flash memory, which stores bits as electrical charge, graphitic memory won't
wear out as quickly. And graphite memory cells can be vertically aligned and stacked,
which means that a chip using graphite
has the potential to store 10 times more bits in
the same space than today's flash memory.

A graphite memory cell is composed of sheets of graphite deposited between two
electrodes. The two
-
electrode design of graphitic memory differs from that of flash
me
mory, which requires a "source," a "drain," and a "gate" to hold electric charge
--
essentially the bits of data. Because flash memory must store charge on the gates,
which tend to leak, the cells wear out over time.

Graphitic memory works differently. When
a certain voltage is applied to a memory
cell, the strip of graphite cracks, explains Tour. The presence or absence of a crack
--
represented as a 0 or a 1
--
can be read by applying a lower voltage across the
electrodes. Applying a larger voltage smoothes the

crack, essentially erasing the bit.
Tour admits that he isn't sure of the exact mechanism that occurs during the process of
writing data, but he suspects that the voltage creates a filamentary structure within the
carbon that interacts with the surroundin
g silicon, producing a characteristic electrical
signature.

The two
-
electrode structure of graphitic memory is what enables it to be built in a
three
-
dimensional memory cell, explains Tour. The three
-
component structure of
flash memory makes it overly comp
licated to connect memory cells vertically.
Graphitic memory, on the other hand, can easily be deposited between two layers of
electrodes.

Tour's group isn't the only one exploring three
-
dimensional memory. IBM's Stuart
Parkin is developing so
-
called
racetrack memory

that stores data by altering the
magnetic properties of nanowires deposited on silicon. And chip manufacturer
SanDisk is developing a three
-
dimensional memory that

uses vertically stacked arrays
of diodes.

In the coming years, it will be increasingly important to develop three
-
dimensional
memory, says Tour. "If you're not in the 3
-
D memory business in five years, you're
not going to be in the memory business."

The w
ork has gotten the attention of industry forecasters. "The concept is interesting
and potentially promising," says Victor Zhirnov of the
Semiconductor Research
Corporation
. He notes, though, that i
t's still too early to give the technology a full
endorsement, as the underlying mechanism of the memory is not yet clear.

Nonetheless, performance of the early prototypes of graphitic memory is promising,
says Tour. The cells can be written to and read fr
om at speeds comparable to today's
flash memory. And the voltages that are required to operate them are lower than those
required for flash.

In addition, the technology could extend beyond memory to another part of the
electronics industry that builds chip
s called field
-
programmable gate arrays (FPGAs).
These chips are reconfigurable for different tasks, from controlling radios to
crunching numbers, but today's FPGAs are limited in the number of times they can be
reconfigured. If the components between laye
rs in FPGAs were connected using
graphitic pillars or strips, says Tour, then they could be almost infinitely rewritable.

The Rice University researchers have partnered with startup NuPGA, a company that
will use the graphite technology to make FGPAs. In a
ddition, Tour says, an unnamed
company supports the memory work. Tour suspects that it could take at least eight
years to turn the prototypes into products, because of the need to ensure reliability and
optimize the manufacturing process.

Flexible Touch Sc
reen Made with Printed Graphene


See through:

Researchers have created a flexible graphene sheet with silver
electrodes printed on it (top) that can be

used as a touch screen when connected to
control software on a computer (bottom).

Credit: Byung Hee Hong, SKKU.

Computing

Flexible Touch Screen Made with Printed Graphene

Sheets of atom
-
thick carbon could make displays that are super fast.



Monday, June
21, 2010



By Nidhi Subbaraman

Graphene, a sheet of carbon just one atom thick, has spectacular strength, flexibility,
transparency, and electrical conductivity. Spurred on by its potential for application in
new devices like touch screens and solar cells, r
esearchers have been toying with
ways to make large sheets of pure graphene, for example by shaving off atom
-
thin
flakes and chemically dissolving chunks of graphite oxide. Yet in the thirty
-
some
years since graphene's discovery, laboratory experiments hav
e mainly yielded mere
flecks of the stuff, and mass manufacture has seemed a long way away.

"The future of the field certainly isn't flaking off pencil shavings," says
Michael
Strano
, a professor
of chemical engineering at MIT. "The large
-
area production of
monolayer graphene was a serious technological hurdle to advancing graphene
technology."

Now, besting all previous records for synthesis of graphene in the laboratory,
researchers at Samsung and

Sungkyunkwan University
, in Korea, have produced a
continuous layer of pure graphene the size of a large television, spooling it out
through rollers on top of a flexible, see
-
through, 63
-
centimeter
-
wide

polyester sheet.

"It is engineering at its finest," says
James Tour
, a professor of chemistry at Rice
University who has been working on ways to make graphene by dissolving chunks of
graphite. "[People ha
ve made] it in a lab in little tiny sheets, but never on a machine
like this."

The team has already created a flexible touch screen by using the polymer
-
supported
graphene to make the screen's transparent electrodes. The material currently used to
make tra
nsparent electronics, indium tin oxide, is expensive and brittle. Producing
graphene on polyester sheets that bend is the first step to making transparent
electronics that are stronger, cheaper, and more flexible. "You could theoretically roll
up your iPho
ne and stick it behind your ear like a pencil," says Tour.

The Korean team built on rapid advances in recent months. "The field really has
advanced in the past 18 months," says Strano. "What they show here is essentially a
monolayer over enormous areas
--
mu
ch larger than we've seen in the past."


Roll and reel:

A freshly made sheet of graphene is transferred onto a polyester sheet
as it passes between hot

rollers.

Credit: Byung Hong Hee, SKKU.

Last year,
Rodney Ruoff

and his team at the University of Texas in Austin showed
that graphene could be grown on copper foil. Carbon vaporize
d at 1,000 degrees
would settle atom
-
by
-
atom on the foil, which was a few centimeters across.
Byung
Hee Hong
, a professor at Sungkyunkwan University and corresponding author on the
paper, says th
e use of a flexible base presented a solution to the graphene mass
-
manufacturing dilemma.

"[This] opened a new route to large
-
scale production of high
-
quality graphene films
for practical applications," says Hong. "[Our] dramatic scaling up was enabled by
the
use of large, flexible copper foils fitting the tubular shape of the furnace." And the
graphene sheets could get even bigger. "A roll
-
to
-
roll process usually allows the
production of continuous films," says Hong.

In Hong's method, a sheet of copper foi
l is wrapped around a cylinder and placed in a
specially designed furnace. Carbon atoms carried on a heated stream of hydrogen and
methane meet the copper sheet and settle on it in a single uniform layer. The copper
foil exits the furnace pressed between h
ot rollers, and the graphene is transferred onto
a polyester base. Silver electrodes are then printed onto the sheet.

The technique shows some potential to be scaled up for mass production. "They
particularly show that they are able to grow the graphene [i
n a way] that is compatible
with manufacturing," says Strano. "It's a very economical way to manufacture
materials."

Hong sees application for the method in the production of graphene
-
based solar cells,
touch sensors, and flat
-
panel displays. But he says p
roducts will be a while in coming.
"It is too early to say something about mass production and commercialization," he
says. Current manufacturing processes for indium tin oxide use a spreading
technology that is different from roll
-
to
-
roll printing. "Howev
er, the situation will be
changed when bigger flexible
-
electronics markets are formed in the near future,"
Hong says.




















A Better Way to Make Graphene


Making material:

Sheets of graphene lay atop a mat of single
-
walled carbon
nanotubes.

Credit: N. Behabtu/Rice University

Computing

A Better Way to Make Graphene

A new method could allow more practical manufacturing of the material.



Tuesday, Ju
ne 8, 2010



By Katherine Bourzac

Single
-
atom
-
thick sheets of carbon called graphene have some amazing properties:
graphene is strong, highly electrically conductive, flexible, and transparent. This
makes it a promising material to make flexible touch screen
s and superstrong
structural materials. But creating these thin carbon sheets, and then building things out
of them, is difficult to do outside the lab.

Now an advance in making and processing graphene in solution may make it practical
to work with the mat
erial at manufacturing scale. Researchers at Rice University have
made graphene solutions 10 times more concentrated than any before. They've used
these solutions to make transparent, conductive sheets similar to the electrodes on
displays, and they're cur
rently developing methods for spinning the graphene
solutions to generate
fibers

and structural materials for airplanes and other vehicles
that promise to be less expensive than t
oday's carbon fiber.

Whatever the end product, it's ideal to start with a high
-
concentration solution of
graphene, but existing methods can't achieve this, says
James Tour
, professor of
chemistry at Rice U
niversity. Graphene isn't very soluble, partly because of its
dimensions, and partly because of its chemistry. Graphene is just one atom thick, but
its surface area is huge. "If you want to work with graphene, you're working dilute,
which makes sense, beca
use this is a huge whopping molecule," Tour says.

Most methods for making graphene start with graphite and involve flaking off atom
-
thin sheets of graphene, usually using chemical means. "The key is to make single
-
layer graphene, to not destroy it in the p
rocess, and to do it in high volume," says
Yang Yang
, professor of materials science and engineering at the University of
California, Los Angeles. Some of the existing methods for makin
g graphene from
graphite and then manipulating it in solution involve adding soluble groups to the
surface of the molecule, but this chemical change destroys graphene's electrical
properties.

The Rice researchers make graphene solutions using a method they

initially
developed for working with carbon nanotubes. About five years ago, researchers led
by the late Nobel laureate
Richard Smalley

discovered that highly conce
ntrated
sulfuric acid, so strong it's called a "superacid," can bring
carbon nanotubes

into
solution by coating their surfaces with ions.
Last year
, the Rice group, now led by
chemist
Matteo Pasquali
, showed they could use superacid solutions of carbon
nan
otubes to make fibers hundreds of meters long; the group has contracted with a
major chemical company to commercialize the process.

The Rice researchers recently demonstrated that even stronger superacids can separate
graphite into sheets of graphene and b
ring them into solution. Unlike other methods
involving chemical reactions that alter graphene, the superacid solution does not
degrade the material's properties. The group has used the solutions to make sheets of
graphene with low electrical resistance an
d is now "full steam ahead" using these
solutions to make graphene fibers, says Tour.

Tour expects the graphene processing method to have two major applications:
transparent electrodes and structural materials. In both areas, it may bring down costs.
Indi
um tin oxide, the transparent conducting material most commonly found in touch
screens and solar cells, is expensive and brittle, says Benji Maruyama, senior
materials research engineer at the Air Force Research Laboratory in Ohio. The U.S.
Air Force is fu
nding the Rice research. Many groups have demonstrated the
advantages of graphene electrodes in terms of conductivity and flexibility; the Rice
method should make it possible to manufacture them over large areas.

The process could also be used to bring dow
n the costs of lightweight, tough
structural materials made from carbon fiber. These materials have been around for
decades, but they remain expensive because the processes used to manufacture them
are complex and result in lost material. Instead of making

pure carbon into fibers
directly, as in the Rice process, the current process starts with a nitrile polymer fiber
that's heated to turn it into graphite. These fibers are then woven into mats and glued
together to make a bulk material. "They're used in ai
rcraft, but not in automobiles,
because the costs are too high," says Tour. "If we can do this more cheaply and get as
good or better properties, there is the potential for a real advance in carbon fibers."







Graphene Wins Nobel Prize


Prize winner:

The Nobel Prize in physics this year went to U.K. researchers who
pioneered the study of graphene. This scanning
-
electron microscope image shows a
cru
mpled graphene sheet of the single
-
atom
-
thick material.

Credit: University of Manchester

Computing

Graphene Wins Nobel Prize

A pair of U.K. physicists are awarded the prize for demonstrating the material's
unusual properties.



Wednesday, October 6, 2010



B
y Katherine Bourzac

The
2010 Nobel Prize in Physics

has been awarded to the two researchers who
performed the first experiments on graphene, a two
-
dimensional sheet of c
arbon
atoms. The award, given to University of Manchester physicists
Andre Geim

and
Konstantin Novoselov
, recognizes work that began less than a decade ago on a
material that's since been used to make record
-
breaking transistors and stretchy
electrodes.

Graphene is a material of many superlatives: it's the best conductor of electric
ity at
room temperature and the strongest material ever tested. It's also an excellent heat
conductor, and is transparent and flexible. Before Geim and Novoselov's work,
researchers had theorized the material's existence, and had predicted that it could be

used to make transistors more than 100 times faster than those in today's silicon
-
based
chips. But until the U.K. researchers made and tested graphene in 2004, many
physicists guessed that materials one
-
atom thick would be unstable.

In 2004, Geim and Novo
selov made graphene in the lab by using adhesive tape to
peel a chunk of graphite into ever
-
thinner sheets, as in
this video
. A graphene sheet is
a single layer of carbon atoms enmeshed in a ho
neycomb
-
like, repeating hexagon
pattern.

Graphene is a naturally occurring material. Layers of graphene make up the graphite
found in pencil lead. When you trace a pencil on a piece of paper, these layers are
cleaved, leaving thin layers of these carbon sh
eets. By crushing graphite and peeling it
with tape into ever
-
thinner flakes and eventually into pieces just one atom thick, Geim
and Novoselov were able to make usuable quantities of graphene that could be studied
and to lay to rest doubts about graphene'
s stability.

In their initial work, in 2004, they not only demonstrated that they had made
graphene, but also elucidated its electrical properties by patterning it and connecting it
to electrodes. "They were not the first ones ever to see graphene, but cer
tainly it was
Geim and Novoselov who really opened the door to be able to study it," says
James
Tour
, professor of chemistry at Rice University.

Once they developed this experimental system for studying th
e material, Geim and
Novoselov, and other researchers who followed, found some remarkable things. First,
electrons in graphene behave as if they have no mass, careening forward at speeds of
one million meters per second. (Compare that to the speed of light

in a vacuum, 300
million meters per second.) And while electrons usually bounce off obstacles inside a
conductive material, electrons traveling through the perfect honeycomb lattice of
graphene have smooth sailing.

Graphene's perfect structure gives rise
to exotic quantum effects that are being studied
by physicists. However, the material's electrical properties, its transparency, and its
strength have been seized on by engineers working to make everything from touch
screens to solar cells to lightweight s
tructural materials. Researchers at IBM are
developing arrays of
graphene transistors

that leave conventional silicon in the dust,
and a group at Samsung is developing
printed graphene electrodes

for use in
transparent, flexible touch screens.

In recognition of the promise of the material,
TR

featured work at Georgia Tech on
graphene transistors

as one of the most promising emerging technologies in 2008; in
the same year we recognized
Novoselov

with our young innovator award, the TR35.

Geim

and Novoselov's technique can be used to make graphene in relatively small
quantities, enough to study it in the lab and make test devices, but nowhere near
enough for manufacturing. In the intervening years, researchers have developed
methods for making
larger quantities of the material, and now they're learning how to
use it to make devices.

"Now we have to find ways of synthesizing graphene reliably on a large scale, and
making these technologies reproducibly in a way that makes economic sense," says
Ph
aedon Avouris, a researcher developing graphene transistors and photodetectors at
IBM's Watson Research Center in Yorktown Heights, New York.



Source:
www.
technology
review.com








نيفارجلا

*
وهو ،نيفارغلا
يلاتلا ليجلل ةقراخلا ةداملا ربتعا نوبركلا نم عون



*
يف رغصلا ةيهانتم ةدام ىوقاو عفرا يهو ،ةرذلا ةكامس اهتكامس زواجتت لا نيفارغلا ةدامو
هنأب نيفارغلا فصو انه نمو . ةرارحلاو ءابرهكلا لقن اهنكميو ةفافش نوكت داكت اهنأ امك ،ملاعلا
بشا لحم لحت نلأ ةحشرملا ةداملا
ةينوكيليسلا تلاصوملا ها



*
عم ملقأتلاو ربكا ةعرسب لمعلا نم ،نيفارغلا نم ةبكرملا تاروتسيزنارتلا نكمتت نا عقوتيو


ايلاح ةمدختسملا رتويبمكلا تاقاقر نم ىلعأ ةرارح تاجرد


*
لاجم يف لمعلا آدب ناذللا ،ناملاعلا نكمت ؛ مويلا ةيميداكلأا نع ردص يفحص نايب بسحبو
لا ثوحب
نم ةيدايتعاةعطق نم نيفارجلا ةدام صلاختسا نم قباسلا يف ،ايسور يف ءايزيف
كلذو ،رصنعلا اذه نم ةدحاو ةرذ ةكامس اهتكامس يف لداعت نوبركلا نم ةقاقر يهو ،تيفارجلا
يرولبلا ءانبلا اذه ةيتابث ةلاحتساب نوريثكلا دقتعي ناك يذلا تقولا يف

تلا ةعورو نوبركلا رحس .. نيفارجلا
ليكش

كلتمي ذإ ،ةداملا ملع لاجم يف ةدعاولا داوملا نم وهو ،نوبركلا لاكشأ نم لكش نيفارجلا ربتعي
،ءابرهكلا ليصوت ىلع هتردق يف ساحنلا ىلع قوفتي وهف ؛داوملا ةيقب عم ةنراقم ةديرف صئاصخ
ىرخلأا داوملا ةرارحلا ليصوت ىلع هتردق قوفت اميف
.

*
س داوملا لقأ نيفارجلا دعيو
نم ةكبش نم فلأتت ةفاثكلا ةيلاع ةفافش ةدام وهو ،ةوق اهدشأو ةكام
ءانبلا ةدحو دعي وهو ،ةصارتملا لحنلا تويب لكشل هباشم لكش اهل ،داعبلأا ةيئانث نوبركلا تارذ
ةريهشلا تيفارجلا ةدامل ةيساسلأا
.

*
تت نا نكمي لا نيفارجلا ةدام نأ ةليوط تارتفل نيثحابلا نم ديدعلا دقتعاو
اذل ،تباث لكشب دجاو
وأ ،اهضعب قوف فتلت دق اهتكامس ةقر ببسبو اهنأ ذإ ؛"ةيميداكأ "ةدام ةيلمعلا ةيحانلا نم يهف
اهلزع لبق ىشلاتت ىتحوأ ،رسكتت
.


قصلا طيرشو صاصر ملقب يملع قارتخا


*
وسلا داحتلاا ديلاوم نم امهو ،"فوليسوفون نيتناتسنوك"و "مييج هيردنأ" ناملاعلا نكمت
يتايف
نيفارجلا ةدام صلاختسا نم ،

اقباس
-

تباث لكشب دجاوتت نأ لاحملا نم هنأب دقتعي ناك يتلا
-

نم
ةلسلس ةياهن يف انكمت ثيح ،يداع قصلا طيرش مادختسا قيرط نع كلذو ،تيفارجلا نم ةعطق
ةدحاو ةرذ ةكامس لدعت ةكامسب نوبركلا نم ةقاقر صلاختسا نم براجتلا نم
.

*
نيصتخم بسحبو
قوف ةصارتم نيفارج ةقبط نييلام ةثلاث نم تيفارجلا نم رتيملم لك فلأتي ؛
زربي يذلا رملأا ،اهضعب نع اهلصف لهسلا نم اذل ،ةوقب ةكسامتم ريغ يهو ،ضعبلا اهضعب
تيفارجلا ةدام نم هسأر نوكتي ثيح ،صاصرلا ملقب ةباتكلا دنع
.

*


ق يملع بولسأب تممص ةبرجت للاخ ناملاعلا مدختساو
،ةيداعلا ةقصلالا ةطرشلأا نم

اعط
ةرم لك يف لاصحي اناكو ،رركتم لكشب تيفارجلا نم تاقاقر عزن ىلع اهتطساوب اولمع ثيح
نيفارجلا نم ةددعتم تاقبط نم فلأتت تاقاقر ىلع
.

*
نوكيليسلا ةدام نم حطسب تيفارجلا نم ةلصفنملا عطقلا طبر ىلإ ناثحابلا دمع مث نمو
ختسملاو ،دسكاتملا
عيدبلا هلكشب نيفارجلا ةيؤر نم

اريخأ انكمتيل ،تلاصوملا هابشأ ةعانص يف مد
هدوجو نم ققحتلاو نيفارجلا لصف نم انكمت امهنأ ينعي ام ،يداعلا يئوضلا رهجملا ةسدع تحت
ةفرغلا ةرارح ةجرد ىلع تباث لكشب
.


ةلهذم تاقيبطت .. نيفارجلا


*
هنم لعجت ةديرف صئاصخ نيفارجلا كلتمي
،تاقيبطتلا نم ديدعلل ةبسنلاب مامتهلال ةريثم ةدام
ةقئافلا اهتوقو ةيلاعلا اهتنورمب زاتمتو ،)ةكامسلا ةليلق( ةقرلا ةغلاب ةفافش ةدام وهف
.

*
ةرانلإا تاحول ،سمللاب لمعت يتلا تاشاشلا عينصت يف هتيفافشل نيفارجلا مادختسا نكميو
ذه نم ةدافلإا نكمي امك ،ةيئوضلا ايلاخلاو
تاذ تاينورتكللإاو زاغلا تاسجم ةعانص يف ةداملا ه
يف اهلامعتسا ةيناكمإ عم ،)ةينورتكللإا تاشاشلاو لومحملا ةزهجأك(يطلل ةلباقلاو ةيلاعلا ةنورملا
ةفخب عتمتت داوم نم عنصت نأ بجوتي يتلا ةيعانصلا رامقلأاو تارئاطلا ءازجأ ضعب عينصت
ةيوقلا ةبيكرتلاو نزولا
.

*
ا دعت امك
يف قوفتتل ،لهذم لكشب بيساوحلا ريوطتب نيفارجلا نم ةعنصملا تاروتسيزنارتل
ريبك لكشب ةيلاحلا بيساوحلا ىلع اهئادأ
.

*
لثم داوملا ضعب ريوطت يف نيفارجلا مادختسا ةيناكمإ نأ ىلإ تاساردلا حملت كلذ بناج ىلإ
ا ىلإ )ةئاملا يف دحاو( ةطيسب ةبسنب نيفارجلا ةفاضإف ،كتيسلابلا
ةنورم نم ديزيس ،كيتسلابل
حتفي ام ،ءابرهكلل ةلصوملا داوملا نم اهلعجيو ،ةرارحلا لمحت ىلع اهتردق نم عفريو ةريخلأا
سرب سدق(.ةريثملا تاقيبطتلا نم ديدعلا يف ةروطملا داوملا نم عونلا اذه مادختسا مامأ لاجملا
)


لأا هذه يف بساحلا تاجلاعم اهل تلصو يتلا ةقئافلا ةعرسلاف
نوكيليسلا نلأ كلذ و فقوتت دق ماي
ءدب ىلع نيثحابلاب ىدأ امم ةيئايزيفلا هتاردق دافنتسا ىلع براق تاجلاعملا هذه هيلع ىنبت يذلا
ليدب نع ثحبلا
.

*
نع

اضوع نيفارجلا مادختسا نأ اهدافم ةجيتنل لصوتلاب كت ايجروج ةعماج نم روسفورب ماق
فعاضيس تاجلاعملا ءانب يف نوكيليسلا

يف ةديدج

اقافآ حتفي و ةريبك ةبسنب تاجلاعملا هذه ةعرس
داوملا نم ديدعلا عينصت يف مدختست لب ةديدج ةدامب سيل نيفارجلا .تاروتسزنارتلا هذه عنص
صاصرلا ملاقأ اهنمو
.

*
اهترارح ةجرد عفترت نأ نودب ةيناثلا يف ةديدع تايلمعب موقت نوكيليسلا ىلع ةينبملا تابساحلا
حل نكل و
ةجرد عفترت و

ابيرقت ةمواقم نودب هيف رمت تانورتكللاا نإف نيفارجلا امأ ،نيعم د


ابسانم هلعجي ةعرسب ةرارحلل هدقف و ةرارحلل ديج لصوم هنلأ كلذ و

ادج ةليلق ةبسنب هترارح
ةروصحم ىقبتس نوكيليسلا ىلع ةينبملا تاجلاعملا ةعرس نإف

اضيأ .تاينورتكللاا يف همادختسلا
ن يف
ـلا قاط

GigaHertz
ـلا قارتخا نم اهنكميس نيفارجلا امأ
TeraHertz.

تاينقتل دتمتس اهنكل و تاروتسزنارتلا و تاجلاعملا يف ةروصحم نوكت نل نيفارجلا تامادختسا
ه عيمج نلأ كلذ و ةحلسلأا نع فشكلا و يجوملا فشكلا و ريوصتلا و تلااصتلاا
تاقيبطتلا هذ
نلآا ىتح اهل لصوتلا متي مل ةقئاف ةعرس بلطتت
.

*
امك

امامت لصوم هبشب سيل هنأ وهو ،نيفارجلا مادختسا يف أديحو

اقئاع ءاملعلا هجاوي
تايمك ةراسخب ببستتس اهنإف لاإ و تاروتسزنارتلا يف اهدجاوت مهم ةيصاخلا هذه و نوكيليسلا
ملعلا نكلو ،ةدئاف نود ةقاطلا نم
نوكيليسلا براقي هلعج و ةبقعلا هذه زواجت ىلع اوبراق ءا
ليصوتلا يف هصئاصخب
.

*
ةقلعتملا ثاحبلأا يف تاروطتلا بقرتت يتلا ةينقتلا تاكرش نم ريثكلا يملعلا حتفلا اذه بذج دقل
لتنا و ما يب يا ، يب شتا : اهنمو اهضعب معدت و نيفارجلاب
.

*
ن رخآ ليدب نع لايوط اوثحبنوثحابلاف
تايلمعب موقت نوكيليسلا ىلع ةينبملا تابساحلا نلأ

ارظ
نيعم دحل نكلو اهترارح عفترت نأ نود نم ةيناثلا يف ةديدع
.


*
نم اوفرعي مل امو اوفرع ام لك اوبرجيو اوليختي نأ نع نويئايزيفلا ناوتي مل تاونس ةدع ذنمو
فو ةريبك ةبسنب تاجلاعملا ةعرس نم ديزت ةدام ىلإ لصوتلل داوم
عنص يف ةديدج قافآ حت
تاجلاعملا هذه اهنم نوكتت يتلا تاروتسزنارتلا
.


*
نم ديدعلا عينصت يف مدختست يتلا نيفارجلا ةدام ىلإ نيثحابلا لصوت ثاحبلأا هذه ةجيتن تناك
ةداملا ربتعي ةيكبشلا ةيوينبلا ةيحانلا نم هنأ نيفارجلا تازيمم نمو ،صاصرلا ملاقأ لثم داوملا
ولا ةرلبتملا
سدسم لكش ىلع ةبترم اهيف نوبركلا تارذ نأ ىنعمب غارفلا يف نيدعبلا تاذ ةديح
ةدحاو ةرذ كمسبو

احطسم

ائيزج نوكي هلعجي رملأا اذه .

امامت لحنلا ةيلخك علاضلأاو اياوزلا
لداعي ام يأ
1،0

رتمونان
.


*
يف لاصوت رنجاو تربرهو نيمرم ديفيد نايكيرملأا ناثحابلا ناكو
0611

ىلإ
تيفارجلا نأ
ةدحاو ةقبط نأ يأ ،ةيرارحلا ةراثتسلاا وأ ةرارحلا لماعب رثأتي ،صاصرلا ملاقأ هنم عنصت يذلا
ىلإ لوحتت نأ نكمي اهسفن ةداملا نإف يلاتلابو ،ةيلكشلا اهتينب يف برطضت نأ نكمي تارذلا نم
اهلزع نكمي لا هنلأ

ارظن ةعئام ةدام وأ لئاس
.


*
يفلا عنمي مل رملأا اذه
ةعماج نم يملعلا هقيرفو مياج هيردنأ يسورلا لصلأا اذ يدنلوهلا يئايز


امامت

احطسم سيل نيفارجلا نأ لاإ مهللا ،نيفارجلا ةرولب لزع يف اوحجني نأ نم ،رتسشنام
ةيرارحلا ةراثتسلاا ةقاط صاصتما ىلع ةرداق

ادج ةقيقد تاجومت نع رهظيو
.


*
ظإ نع نيفارجلا فكي مل هفاشتكا ذنمو
هنأ نيبت هصئاصخف ،ةقوبسم ريغ ةديدج صئاصخ راه
نأ امك ةلئاسلا تارولبلا وأ ةيسمشلا حاوللأا ةعانص لاجم يف ةيلاثمو ةلصومو ةفافش ةدام
هصاوخ نإف كلذ نع

لاضف ،ةبلاصلا ةقئاف داوملا نم نوكيس هنأب رشبت ةيكيناكيملا هتمواقم
رس نلأ لعفلاب ءاملعلا ةشهد تراثأ ةينورتكللإا
قدصي لا لكشب ةعفترم هيف ينورتكللإا لقنلا ةع
كلذو

ادج ةليلق ةبسنب هترارح ةجرد عفترتو

ابيرقت ةمواقم نود نم هربع رمت تانورتكللإا نأ يأ
يف مادختسلال

ابسانم هلعجي يذلا رملأا

ادج عيرس اهل هدقفو ةرارحلل ديج لصوم هنلأ
تاينورتكللإا
.


*
ةعرس نأ ىلإ نوثحابلا ريشيو

نيثلاثب نوكيليسلا يف اهتعرس ىلع ديزت هيف تانورتكللإا لاقتنا
قاطن يف ةروصحم ىقبتس نوكيليسلا ىلع ةينبملا تاجلاعملا ةعرس نإف كلذ ىلع ةولاع .ةرم
زترهارتيسلا قاطن قارتخا نم اهنكميسف نيفارجلا امأ زترهافيجلا
.


*
يفارجلا جاتنلإ ةيملعلا تاربتخملا طشنت ةنولآا هذه يف
اهنم ىلولأا :نيتقيرطب ةيراجت تايمكب ن
ديبرك ةرولب ةرارح عفر يف لثمتتو ةيكيرملأا اتنلاتأ ةيلاوب يجولونكتلا ايجروج دهعم اهريدي
نم رثكأ ىلإ )نوكيليسلا( مويسيليسلا
0111

هذه نع جتنيو .رخبتتو ككفتت نأ ىلإ ةيوئم ةجرد
هنيب اميف طبترت يتلا نوبركلا تارذ ءاقب ةيلمعلا
.نيفارجلا نم ةيسادس ةكبش ةلكشم يئاقلت لكشب ا
:رخفب دهعملا اذه يف لمعت يتلا هيجرب ريلك لوقتو

اهجتني يتلا نيفارجلا تاقيرو ضرع غلبي
نأ ةنسلا هذه للاخ انعطتسا اننأ وه كلذ نم مهلأا نكل ،رتموركيملا نم تارشع عضب ربتخملا
ك تناك اهانجتنأ يتلا تانيعلا ةواقن نأ تبثن
ام ،ةينورتكلإوركيملا تاقيبطتلا يف اهمادختسلا ةيفا
لولأا نوناك /ربمسيد يف لعفلاب تقلطنا دق يراجتلا ىوتسملا ىلع جاتنلإا ةلحرم نأ ينعي
8112

اتنلاتأ يف
”.


*
ةيقيبطتلا ثاحبلأا ربتخم نم وراوب يريت ثحابلا اهل ريضحتلا ىلإ ىعسي يتلا ةيناثلا ةقيرطلا
نورتكللإا لاجم يف
هنأ نييسنرفلا نيثحابلا فاشتكا نم ديفتست ،ةيسنرفلا لبونورغ ةنيدمب تاي
هنإف يلاتلابو نيفارج ىلإ لوحتتو ككفتت هتاقيرو نإف يضمح طسو يف تيفارجلا دسكؤن امدنع
نم نيثحابلا نم قيرف نكمت ،ةريخلأا ةنولآا يفو .لزتخم لولحم مادختساب ةرولبلا ةيقنت يفكي
م اينروفيلاك ةعماج
نيجورديهلاو توزلآا نم بكرم( نيزارديهلا ةدام نأ فاشتكا ن
)
ىلع ةرداق
تاقبط ىلع لوصحلا نيثحابلل نكمي ثيح زاتمم لكشب نيفارجلا هب موقت يذلا رودلاب موقت نأ
ىلولأا ةقيرطلا نم صخرأ رعسبو ةيلاع ليصوت ةجرد تاذ
.


*
ارتلاو تاجلاعملا يف ةروصحم ىقبت نل نيفارجلا تامادختسا
تاينقت ىلإ دتمتس لب تاروتسزن
نع فشكلل ايجولويبلاو ةحلسلأا نع فشكلاو يجوملا فشكلاو ريوصتلاو تلااصتلااك ىرخأ
ةقئاف ةعرس بلطتت تاقيبطتلا هذه عيمج نلأ كلذو يوونلا ضمحلا تايلاتتم
.


*
لا ةيحانلا نم هنلأ يئايزيفلل ةمحرلا ةباثمب نيفارجلا نإ مياج هيردنأ ثحابلا لوقيو
هنكمي ةيرظن
نم ةدحاو ةقيرو يفف ،لصوتلا ةقئافو داعبلأا ةيئانث ةدام ىلع لصوحلا ةدحاو ةرذ للاخ نم
اهتلتك تدقف ةقيقحلا يف اهنأكو ةيوبسنلا ةيمومكلا تاميسجلاك ةيبرهكلا تانحشلا كرحتت نيفارجلا
يرذلا ءايزيفلا نم عونلا اذه نأ مياج فيضيو .ءوضلا ةعرسب كرحتت اهلعجي امم
ديعب ناك ة
سمخلا تاونسلا نوكتسو ،تاميسجلل لجعمك لمعي هنأب نيفارجلا هيبشت يننكمي اذلو ،لانملا
لا فيك ..صاخ لكشب رتويبمكلا ملاع اهدهشيس يتلا تاروطتلا عوضوم يف ةلصاف ةلبقملا ةرشع
؟ةرم يتئامب ذلاوفلا نم ةمواقم دشأ وهو

سامللاا نم هبلاص دشا هدام ىهف




























Graphene

&

Its

effects on various fields