This single-atom-thick honeycomb of carbon atoms 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 computer displays, solar panels, touch screens, integrated circuits and biomedical sensors, 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 physicists 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 electronmobility – 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.University Distinguished Professor of Physics & Engineering Sokrates Pantelides and Research Associates Yevgeniy Puzyrev and Bin Wang contributed to the study.
David F. Salisbury | Vanderbilt University
An innovative high-performance material: biofibers made from green lacewing silk
20.01.2017 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Treated carbon pulls radioactive elements from water
20.01.2017 | Rice University
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences