Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ultra-flat circuits will have unique properties

26.07.2016

Rice University lab studies 2-D hybrids to see how they differ from common electronics

The old rules don't necessarily apply when building electronic components out of two-dimensional materials, according to scientists at Rice University.


Hybrids of two-dimensional materials like the graphene-molybdenum disulfide illustrated here have electronic properties that don't follow the same rules as their 3-D cousins, according to Rice University researchers. The limited direct contact between the two materials creates an electric field that greatly increases the size of the p/n junction.

Credit: Henry Yu/Rice University

The Rice lab of theoretical physicist Boris Yakobson analyzed hybrids that put 2-D materials like graphene and boron nitride side by side to see what happens at the border. They found that the electronic characteristics of such "co-planar" hybrids differ from bulkier components.

Their results appear this month in the American Chemical Society journal Nano Letters.

Shrinking electronics means shrinking their components. Academic labs and industries are studying how materials like graphene may enable the ultimate in thin devices by building all the necessary circuits into an atom-thick layer.

"Our work is important because semiconductor junctions are a big field," Yakobson said. "There are books with iconic models of electronic behavior that are extremely well-developed and have become the established pillars of industry.

"But these are all for bulk-to-bulk interfaces between three-dimensional metals," he said. "Now that people are actively working to make two-dimensional devices, especially with co-planar electronics, we realized that the rules have to be reconsidered. Many of the established models utilized in industry just don't apply."

The researchers led by Rice graduate student Henry Yu built computer simulations that analyze charge transfer between atom-thick materials.

"It was a logical step to test our theory on both metals and semiconductors, which have very different electronic properties," Yu said. "This makes graphene, which is a metal -- or a semimetal, to be precise -- molybdenum disulfide and boron nitride, which are semiconductors, or even their hybrids ideal systems to study.

"In fact, these materials have been widely fabricated and used in the community for almost a decade, which makes analysis of them more appreciable in the field. Furthermore, both hybrids of graphene-molybdenum disulfide and graphene-boron nitride have been successfully synthesized recently, which means our study has practical meaning and can be tested in the lab now," he said.

Yakobson said 3-D materials have a narrow region for charge transfer at the positive and negative (or p/n) junction. But the researchers found that 2-D interfaces created "a highly nonlocalized charge transfer" -- and an electric field along with it -- that greatly increased the junction size. That could give them an advantage in photovoltaic applications like solar cells, the researchers said.

The lab built a simulation of a hybrid of graphene and molybdenum disulfide and also considered graphene-boron nitride and graphene in which half was doped to create a p/n junction. Their calculations predicted the presence of an electric field should make 2-D Schottky (one-way) devices like transistors and diodes more tunable based on the size of the device itself.

How the atoms line up with each other is also important, Yakobson said. Graphene and boron nitride both feature hexagonal lattices, so they mesh perfectly. But molybdenum disulfide, another promising material, isn't exactly flat, though it's still considered 2-D.

"If the atomic structures don't match, you get dangling bonds or defects along the borderline," he said. "The structure has consequences for electronic behavior, especially for what is called Fermi level pinning."

Pinning can degrade electrical performance by creating an energy barrier at the interface, Yakobson explained. "But your Schottky barrier (in which current moves in only one direction) doesn't change as expected. This is a well-known phenomenon for semiconductors; it's just that in two dimensions, it's different, and in this case may favor 2-D over 3-D systems."

Yakobson said the principles put forth by the new paper will apply to patterned hybrids of two or more 2-D patches. "You can make something special, but the basic effects are always at the interfaces. If you want to have many transistors in the same plane, it's fine, but you still have to consider effects at the junctions.

"There's no reason we can't build 2-D rectifiers, transistors or memory elements," he said. "They'll be the same as we use routinely in devices now. But unless we develop a proper fundamental knowledge of the physics, they may fail to do what we design or plan."

###

Rice postdoctoral research associate Alex Kutana is a co-author of the paper. Yakobson is the Karl F. Hasselmann Professor of Materials Science and NanoEngineering and a professor of chemistry.

The Office of Naval Research supported the research.

David Ruth
713-348-6327
david@rice.edu

Mike Williams
713-348-6728
mikewilliams@rice.edu

Read the abstract at http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.6b01822

This news release can be found online at http://news.rice.edu/2016/07/25/ultra-flat-circuits-will-have-unique-properties/

Follow Rice News and Media Relations via Twitter @RiceUNews

Related materials:

Yakobson Research Group: http://biygroup.blogs.rice.edu

George R. Brown School of Engineering: http://engr.rice.edu

Image for download:

http://news.rice.edu/files/2016/07/0725_CARRIER-1-web-1ede6hv.jpg

Hybrids of two-dimensional materials like the graphene-molybdenum disulfide illustrated here have electronic properties that don't follow the same rules as their 3-D cousins, according to Rice University researchers. The limited direct contact between the two materials creates an electric field that greatly increases the size of the p/n junction. (Credit: Henry Yu/Rice University)

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for best quality of life and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

Media Contact

David Ruth
david@rice.edu
713-348-6327

 @RiceUNews

http://news.rice.edu 

David Ruth | EurekAlert!

More articles from Power and Electrical Engineering:

nachricht Did you know that the wrapping of Easter eggs benefits from specialty light sources?
13.04.2017 | Heraeus Noblelight GmbH

nachricht To e-, or not to e-, the question for the exotic 'Si-III' phase of silicon
05.04.2017 | Carnegie Institution for Science

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

DGIST develops 20 times faster biosensor

24.04.2017 | Physics and Astronomy

Nanoimprinted hyperlens array: Paving the way for practical super-resolution imaging

24.04.2017 | Materials Sciences

Atomic-level motion may drive bacteria's ability to evade immune system defenses

24.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>