Barrier to faster graphene devices identified and suppressed

Mar 13, 2012
An image of a suspended graphene device made by a scanning probe microscope. The graphene sheet is the orange-colored layer suspended between six rectangular columns made of silicon dioxide and capped by gold. Credit: A.K.M. Newaz, Bolotin Lab / Vanderbilt

These days graphene is the rock star of materials science, but it has an Achilles heel: It is exceptionally sensitive to its electrical environment.

This single-atom-thick of is lighter than aluminum, stronger than steel and conducts heat and electricity better than copper. As a result, scientists around the world are trying to turn it into better , , touch screens, and , among other possible applications. However, it has proven extremely difficult to reliably create graphene-based devices that live up to its electrical potential when operating at room temperature and pressure.

Now, writing in the Mar. 13 issue of the journal Nature Communications, a team of Vanderbilt reports that they have nailed down the source of the interference inhibiting the rapid flow of electrons through graphene-based devices and found a way to suppress it. This allowed them to achieve record-levels of room-temperature – the measure of the speed that electrons travel through a material – three times greater than those reported in previous graphene-based devices.

According to the experts, graphene may have the highest electron mobility of any known material. In practice, however, the measured levels of mobility, while significantly higher than in other materials like silicon, have been considerably below its potential.

"The problem is that, when you make graphene, you don't get just graphene. You also get a lot of other stuff," said Kirill Bolotin, assistant professor of physics, who conducted the study with Research Associate A.K.M. Newaz. "Graphene is extraordinarily susceptible to external influences so the electrical fields created by charged impurities on its surface scatter the electrons traveling through the graphene sheets, making graphene-based transistors operate slower and heat up more."

A number of researchers had proposed that the charged impurities that are omnipresent on the surface of graphene were the main culprits, but it wasn't completely certain. Also, several other theories had been advanced to explain the phenomenon.

"Our study shows without question that the charged crap is the problem and, if you want to make better graphene devices, it is the enemy that you need to fight," Bolotin said.

At the same time, the experiment didn't find evidence supporting one of the alternative theories, that ripples in the graphene sheets were a significant source of electron scattering

In order to get a handle on the mobility problem, Bolotin's team suspended sheets of graphene in a series of different liquids and measured the material's electric transport properties. They found that graphene's electron mobility is dramatically increased when graphene is submerged in electrically neutral liquids that can absorb large amounts of electrical energy (have large dielectric constants). They achieved the record-level mobility of 60,000 using anisole, a colorless liquid with a pleasant, aromatic odor used chiefly in perfumery.

"These liquids suppress the electrical fields from the impurities, allowing the electrons to flow with fewer obstructions," Bolotin said.

Now that the source of the degradation in electrical performance of graphene has been clearly identified, it should be possible to come up with reliable device designs, Bolotin said.

According to the physicist, there is also a potential advantage to graphene's extraordinary sensitivity to its environment that can be exploited. It should make extremely sensitive sensors of various types and, because it is made entirely of carbon, it is biocompatible and so should be ideal for biological sensors.

Explore further: Solar cells made from polar nanocrystal inks show promising early performance

Related Stories

Scientists make magnetic new graphene discovery

Apr 14, 2011

(PhysOrg.com) -- University of Maryland researchers have discovered a way to control magnetic properties of graphene that could lead to powerful new applications in magnetic storage and magnetic random access ...

The secrets of tunneling through energy barriers

Nov 07, 2011

Electrons moving in graphene behave in an unusual way, as demonstrated by 2010 Nobel Prize laureates for physics Andre Geim and Konstantin Novoselov, who performed transport experiments on this one-carbon-atom-thick material. ...

Flaky graphene makes reliable chemical sensors

Jan 17, 2012

Scientists from the University of Illinois at Urbana-Champaign and the company Dioxide Materials have demonstrated that randomly stacked graphene flakes can make an effective chemical sensor.

Shining light on graphene sensors

Jan 10, 2011

National Physical Laboratory, together with an international team of scientists, have published research showing how light can be used to control graphene's electrical properties. This advance is an important ...

Recommended for you

First direct observations of excitons in motion achieved

1 minute ago

A quasiparticle called an exciton—responsible for the transfer of energy within devices such as solar cells, LEDs, and semiconductor circuits—has been understood theoretically for decades. But exciton movement within ...

Shiny quantum dots brighten future of solar cells

Apr 14, 2014

(Phys.org) —A house window that doubles as a solar panel could be on the horizon, thanks to recent quantum-dot work by Los Alamos National Laboratory researchers in collaboration with scientists from University ...

User comments : 5

Adjust slider to filter visible comments by rank

Display comments: newest first

TombSyphon2317
4 / 5 (1) Mar 13, 2012
God I love graphene I can't wait for the first graphene based computer.
blownfuse
not rated yet Mar 13, 2012
Almost always in recent years excessive sensitivity has eventually
developed into extrodinary increase in band width
Ojorf
not rated yet Mar 14, 2012
Our study shows without question that the charged crap is the problem


Funny, I like it.
SteveL
5 / 5 (1) Mar 14, 2012
Our study shows without question that the charged crap is the problem


Funny, I like it.
Reminds me of some folks' credit card issues.
Intensero
not rated yet Mar 21, 2012
"Our study shows without question that the charged crap is the problem and, if you want to make better graphene devices, it is the enemy that you need to fight," Bolotin said.

I think they need to pick a new spokesperson. Using crap to describe material is...

That aside, sounds like another graphene breakthrough. The problem now is mass production and purification?

More news stories

Shiny quantum dots brighten future of solar cells

(Phys.org) —A house window that doubles as a solar panel could be on the horizon, thanks to recent quantum-dot work by Los Alamos National Laboratory researchers in collaboration with scientists from University ...

Polymer microparticles could help verify goods

Some 2 to 5 percent of all international trade involves counterfeit goods, according to a 2013 United Nations report. These illicit products—which include electronics, automotive and aircraft parts, pharmaceuticals, ...

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.