Their new paper** demonstrates how both wrinkles in the graphene sheet and/or chance contaminants from processing—possibly hiding in those folds—disrupt and slow electron flow across the sheet. The results could be important for the design of commercial manufacturing processes that exploit the unique electrical properties of graphene. In the case of contaminant molecules at least, the paper also suggests that heating the graphene may be a simple solution.
Graphene, a nanostructured material that is essentially a one-atom thick sheet of carbon atoms arranged in a hexagonal pattern, is under intense study because of a combination of outstanding properties. It's extremely strong, conducts heat very well, and has high electrical conductivity while being flexible and transparent. Graphene's electrical properties, however, apparently depend a lot on flatness and purity.
Using X-rays, the UB team produced images that show the electron "cloud" lining the surface of graphene samples—the structure responsible for the high-speed transit of electrons across the sheet—and how wrinkles in the sheet distort the cloud and create bottlenecks. Spectrographic data showed anomalous "peaks" in some regions that also corresponded to distortions of the cloud. NIST researchers, using their dedicated materials science "beam line" at the National Synchrotron Light Source (NSLS),*** contributed a sensitive analysis of spectroscopic data confirming that these peaks were caused by chemical contaminants that adhered to the graphene during processing.
Significantly, the NIST synchrotron methods group was able to make detailed spectroscopic measurements of the graphene samples while heating them, and found that the mysterious peaks disappeared by the time the sample reached 150 degrees Celsius. This, according to Dan Fischer, leader of the NIST group, showed both that those particular disturbances in the electron cloud were due to contaminants, and that there is a way to get rid of them. "They're not chemical bound, they're just physically absorbed on the surface, and that's an important thing. You have a prescription for getting rid of them," Fischer said.
"When graphene was discovered, people were just so excited that it was such a good material that people really wanted to go with it and run as fast as possible," said Brian Schultz, one of three UB graduate students who were lead authors on the paper, "but what we're showing is that you really have to do some fundamental research before you understand how to process it and how to get it into electronics."
"This is the practical side of using graphene," agrees Fischer, "It has all these remarkable properties, but when you go to actually try to make something, maybe they stop working, and the question is: why and what do you do about it? These kinds of extremely sensitive, specialized techniques are part of that answer."
For more on the study, see the UB June 28, 2011, news announcement "Researchers Image Electron Clouds on the Surface of Graphene, Revealing How Folds in the Remarkable Material Can Harm Conductivity" at www.buffalo.edu/news/12673.
* SEMATECH is a nonprofit research consortium that advances the U.S. semiconductor industry.
** B.J. Schultz, C. J. Patridge, V. Lee, C. Jaye, P.S. Lysaght, C. Smith, J. Barnett, D.A. Fischer, D. Prendergast and S. Banerjee. Imaging local electronic corrugations and doped regions in graphene. Nature Communications. V2, 372. Published on-line June 28, 2011. doi:10.1038/ncomms1376.
*** The NSLS is located at the Brookhaven National Laboratory.
Michael Baum | EurekAlert!
Argon is not the 'dope' for metallic hydrogen
24.03.2017 | Carnegie Institution for Science
Researchers make flexible glass for tiny medical devices
24.03.2017 | Brigham Young University
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy