Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Two-Dimensional Semiconductor Comes Clean


In 2013 James Hone, Wang Fong-Jen Professor of Mechanical Engineering at Columbia Engineering, and colleagues at Columbia demonstrated that they could dramatically improve the performance of graphene—highly conducting two-dimensional (2D) carbon—by encapsulating it in boron nitride (BN), an insulating material with a similar layered structure.

In work published this week in the Advance Online Publication on Nature Nanotechnology’s website, researchers at Columbia Engineering, Harvard, Cornell, University of Minnesota, Yonsei University in Korea, Danish Technical University, and the Japanese National Institute of Materials Science have shown that the performance of another 2D material—molybdenum disulfide (MoS2)—can be similarly improved by BN-encapsulation.

Gwan-Hyoung Lee/Yonsei University

Schematic cross-section view of atomic layer of molybdenum disulfide contacted by graphene, and encapsulated between layers of insulating hexagonal boron nitride.

“These findings provide a demonstration of how to study all 2D materials,” says Hone, leader of this new study and director of Columbia’s NSF-funded Materials Research Science and Engineering Center. “Our combination of BN and graphene electrodes is like a ‘socket’ into which we can place many other materials and study them in an extremely clean environment to understand their true properties and potential. This holds great promise for a broad range of applications including high-performance electronics, detection and emission of light, and chemical/bio-sensing.”

Two-dimensional (2D) materials created by “peeling’” atomically thin layers from bulk crystals are extremely stretchable, optically transparent, and can be combined with each other and with conventional electronics in entirely new ways. But these materials—in which all atoms are at the surface—are by their nature extremely sensitive to their environment, and their performance often falls far short of theoretical limits due to contamination and trapped charges in surrounding insulating layers. The BN-encapsulated graphene that Hone’s group produced last year has 50× improved electronic mobility—an important measure of electronic performance—and lower disorder that enables the study of rich new phenomena at low temperature and high magnetic fields.

“We wanted to see what we could do with MoS2—it’s the best-studied 2D semiconductor, and, unlike graphene, it can form a transistor that can be switched fully ‘off’, a property crucial for digital circuits,” notes Gwan-Hyoung Lee, co-lead author on the paper and assistant professor of materials science at Yonsei. In the past, MoS2 devices made on common insulating substrates such as silicon dioxide have shown mobility that falls below theoretical predictions, varies from sample to sample, and remains low upon cooling to low temperatures, all indications of a disordered material. Researchers have not known whether the disorder was due to the substrate, as in the case of graphene, or due to imperfections in the material itself.

In the new work, Hone’s team created heterostructures, or layered stacks, of MoS2 encapsulated in BN, with small flakes of graphene overlapping the edge of the MoS2 to act as electrical contacts. They found that the room-temperature mobility was improved by a factor of about 2, approaching the intrinsic limit. Upon cooling to low temperature, the mobility increased dramatically, reaching values 5-50× that those measured previously (depending on the number of atomic layers). As a further sign of low disorder, these high-mobility samples also showed strong oscillations in resistance with magnetic field, which had not been previously seen in any 2D semiconductor.

“This new device structure enables us to study quantum transport behavior in this material at low temperature for the first time,” added Columbia Engineering PhD student Xu Cui, the first author of the paper.

By analyzing the low-temperature resistance and quantum oscillations, the team was able to conclude that the main source of disorder remains contamination at the interfaces, indicating that further improvements are possible.

“This work motivates us to further improve our device assembly techniques, since we have not yet reached the intrinsic limit for this material,” Hone says. “With further progress, we hope to establish 2D semiconductors as a new family of electronic materials that rival the performance of conventional semiconductor heterostructures—but are created using scotch tape on a lab-bench instead of expensive high-vacuum systems.”

Funding acknowledgements: This research was supported by the U.S. National Science Foundation (DMR-1122594), the NSF MRSEC program through Columbia in the Center for Precision Assembly of Superstratic and Superatomic Solids (DMR-1420634), and in part by the FAME Center, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA. G.H.L was supported by Basic Science Research Program (NRF-2014R1A1A1004632) through the National Research Foundation (NRF) funded by the Korean government Ministry of Science, ICT and Future Planning, and in part by the Yonsei University Future-leading Research Initiative of 2014. P.Y.H. acknowledges support from the NSF Graduate Research Fellowship Program under grant DGE-0707428. Additional support was provided through funding and shared facilities from the Cornell Center for Materials Research NSF MRSEC program (DMR-1120296). F.P. and B.S.J. acknowledged the Center for Nanostructured Graphene (CNG), which is funded by the Danish National Research Foundation, Project DNRF58. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan. T.T. acknowledges support a Grant-in-Aid for Scientific Research on Grant 262480621 and on Innovative Areas “NanoInformatics” (Grant 25106006) from JSPS.

Contact Information
Holly Evarts
Director of Strategic Communications and Media Rel
Phone: 212-854-3206
Mobile: 347-453-7408

Holly Evarts | newswise
Further information:

Further reports about: Applied Science Engineering materials semiconductor structure temperature

More articles from Power and Electrical Engineering:

nachricht 'Super yeast' has the power to improve economics of biofuels
18.10.2016 | University of Wisconsin-Madison

nachricht Engineers reveal fabrication process for revolutionary transparent sensors
14.10.2016 | University of Wisconsin-Madison

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: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>