Navigation Links
Study quantifies the electron transport effects of placing metal contacts onto graphene
Date:2/24/2010

Using large-scale supercomputer calculations, researchers have analyzed how the placement of metallic contacts on graphene changes the electron transport properties of the material as a factor of junction length, width and orientation. The work is believed to be the first quantitative study of electron transport through metal-graphene junctions to examine earlier models in significant detail.

Information on the ways in which attaching metal contacts affects electron transport in graphene will be important to scientists studying the material and to designers who may one day fabricate electronic devices from the carbon-lattice material.

"Graphene devices will have to communicate with the external world, and that means we will have to fabricate contacts to transport current and data," said Mei-Yin Chou, a professor and department chair in the School of Physics at the Georgia Institute of Technology. "When they put metal contacts onto graphene to measure transport properties, researchers and device designers need to know that they may not be measuring the instrinsic properties of pristine graphene. Coupling between the contacts and the material must be taken into account."

Information on the effects of metal contacts on graphene was reported in the journal Physical Review Letters on February 19th. The research was supported by the U.S. Department of Energy, and involved interactions with researchers at the National Science Foundation (NSF)-supported Materials Research Science and Engineering Center (MRSEC) at Georgia Tech.

Using large-scale, first-principles calculations done at two different NSF-supported supercomputer centers, the Georgia Tech research team which included postdoctoral fellows Salvador Barraza-Lopez and Mihajlo Vanevic, and assistant professor Markus Kindermann conducted detailed atomic-level calculations of aluminum contacts grown on graphene.

The calculations studied two contacts up to 14 nanometers apart, with graphene suspended between them. In their calculations, the researchers allowed the aluminum to grow as it would in the real world, then studied how electron transfer was induced in the area surrounding the contacts.

"People have been able to come up with phenomenological models that they use to find out what the effects are with metallic contacts," Chou explained. "Our calculations went a few steps farther because we built contacts atom-by-atom. We built atomistically-resolved contacts, and by doing that, we solved this problem at the atomic level and tried to do everything consistent with quantum mechanics."

Because metals typically have excess electrons, physically attaching the contacts to graphene causes a charge transfer from the metal. Charge begins to be transferred as soon as the contacts are constructed, but ultimately the two materials reach equilibrium, Chou said.

The study showed that charge transfer at the leads and into the freestanding section of the material creates an electron-hole asymmetry in the conductance. For leads that are sufficiently long, the effect creates two conductance minima at the energies of the Dirac points for the suspended and clamped regions of the graphene, according to Barraza-Lopez.

"These results could be important to the design of future graphene devices," he said. "Edge effects and the impact of nanoribbon width have been studied in significant detail, but the effects of charge transfer at the contacts may potentially be just as important."

The researchers modeled aluminum, but believe their results will apply to other metals such as copper and gold that do not form chemical bonds with graphene. However, other metals such as chromium and titanium do chemically alter the material, so the effects they have on electron transport may be different.

Beyond the new information provided by the calculations, the research further proposes quantitative models that can be used under certain circumstances to describe the impact of the contacts.

"Earlier models had been based on physical insights, but nobody really knew how faithfully they described the material," Kindermann said. "This is the first calculation to show that these earlier models apply under certain circumstances for the systems that we studied."

Data from the study may one day help device designers engineer graphene circuits by helping them understand the effects they are seeing.

"When we modify graphene, we need to understand what changes occur as a result of adding materials," added Chou. "This is really fundamental research to understand these effects and to have a numerical prediction for what is going on. We are helping to understand the basic physics of graphene."


'/>"/>

Contact: John Toon
jtoon@gatech.edu
404-894-6986
Georgia Institute of Technology Research News
Source:Eurekalert  

Related biology technology :

1. Merrimack Pharmaceuticals Initiates Enrollment in Phase 1/2 Combination Study of MM-121 and Tarceva in Patients with Non-Small Cell Lung Cancer
2. KGI Study Reveals Diverse and Vibrant Regional Bioscience Industry
3. Study: Medicare Covers Only Half the Cost of Administering Chemotherapy to Seniors with Cancer
4. Memory Study Enrolling Participants Evaluating Memory Loss Vitamin
5. Fat Tissue May Be a Source of Valuable Blood Stem Cells, Study Says
6. Aegera Therapeutics Initiates a Randomized Phase 2 Study with AEG35156 for the Treatment of Hepatocellular Carcinoma
7. Æterna Zentaris Partner Keryx Reports a Statistically Significant Benefit in Survival from Updated Results of a Randomized, Double-Blind, Placebo-Controlled Phase 2 Study of Perifosine (KRX-0401) in the Treatment of Advanced Metastatic Colon Cancer
8. Ocean Tomo Study Ranks Top 25 Most Inventive Companies for Bloomberg BusinessWeek
9. New Study: Lp(a) Joins LDL as Heart Disease Risk Factor
10. Stroke Therapy with Corkscrew Device Most Beneficial, Study Suggests
11. Study: Era of Rapid Growth in Biomedical Research Over
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Study quantifies the electron transport effects of placing metal contacts onto graphene
(Date:2/10/2016)... WASHINGTON , Feb.10, 2016 ASAE is ... and Association Management Companies (AMC) the option of joining ... flat annual fee determined by staff size, every employee ... to join ASAE and reap all available member benefits.   ... CAE. "Our new organizational membership options will allow organizations ...
(Date:2/10/2016)... Inc. (NYSE MKT: ISR), a medical technology company and ... the treatment of prostate, brain, lung, head and neck ... the second quarter and six months of fiscal 2016, ... --> --> Revenue was $1.19 million ... December 31, 2015, a 12% increase compared to $1.07 ...
(Date:2/10/2016)... 10, 2016  Matchbook, Inc., a company specializing ... biotech companies, announced today the appointment of ... Jim brings nearly 25 years of experience in ... spent nearly two decades in executive level roles ... at Genzyme and, most recently headed global logistics ...
(Date:2/10/2016)... ... 2016 , ... HOLLOWAY AMERICA, a leading custom stainless steel ... Chapter 21st Annual Vendor Exhibition on Thursday, February 18, 2016. The Rocky Mountain ... annual event, which will run from 3:00 p.m. - 8:30 p.m. at The ...
Breaking Biology Technology:
(Date:1/22/2016)... , January 22, 2016 ... the addition of the  "Global Behavioral ... offering. --> http://www.researchandmarkets.com/research/4lmf2s/global_behavioral ) ... "Global Behavioral Biometric Market 2016-2020"  report ... Research and Markets ( http://www.researchandmarkets.com/research/4lmf2s/global_behavioral ) has ...
(Date:1/20/2016)... A market that just keeps on growing. Molecular Diagnostics ... genomics knowledge. Learn all about it in this new ... trends are pushing market growth and company valuations. Trends ... pathogen evolution - next generation sequencing - emergence of ... the role of genetic material in Disease and Health ...
(Date:1/18/2016)... 2016  Extenua Inc., a pioneering developer of ... and access of ubiquitous on-premise and cloud storage, today ... Cyber.  ... C4ISR and Cyber initiatives in support of National ... technology solutions," said Steve Visconti , Extenua ...
Breaking Biology News(10 mins):