Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > 2-D electronics take a step forward: Rice, Oak Ridge labs make semiconducting films for atom-thick circuits

Schematics and experimental images produced by Oak Ridge National Laboratory show defects at the 60-degree grain boundaries in two-dimensional samples of molybdenum disulfide. The defects are 5- and 7-atom dislocation cores; the numbers refer to locations where the atomic arrangements veer from regular six-atom hexagons. Their presence indicates a one-dimensional conductive “wire” that runs along the boundary. In the illustration, the molybdenum atoms are cyan and the sulfur atoms are orange and yellow.Credit: Oak Ridge National Laboratory
Schematics and experimental images produced by Oak Ridge National Laboratory show defects at the 60-degree grain boundaries in two-dimensional samples of molybdenum disulfide. The defects are 5- and 7-atom dislocation cores; the numbers refer to locations where the atomic arrangements veer from regular six-atom hexagons. Their presence indicates a one-dimensional conductive “wire” that runs along the boundary. In the illustration, the molybdenum atoms are cyan and the sulfur atoms are orange and yellow.

Credit: Oak Ridge National Laboratory

Abstract:
Scientists at Rice University and Oak Ridge National Laboratory (ORNL) have advanced on the goal of two-dimensional electronics with a method to control the growth of uniform atomic layers of molybdenum disulfide (MDS).

2-D electronics take a step forward: Rice, Oak Ridge labs make semiconducting films for atom-thick circuits

Houston, TX | Posted on June 10th, 2013

MDS, a semiconductor, is one of a trilogy of materials needed to make functioning 2-D electronic components. They may someday be the basis for the manufacture of devices so small they would be invisible to the naked eye.

The work appears online this week in Nature Materials.

The Rice labs of lead investigator Jun Lou, Pulickel Ajayan and Boris Yakobson, all professors in the university's Mechanical Engineering and Materials Science Department, collaborated with Wigner Fellow Wu Zhou and staff scientist Juan-Carlos Idrobo at ORNL in an unusual initiative that incorporated experimental and theoretical work.

The goals were to see if large, high-quality, atomically thin MDS sheets could be grown in a chemical vapor deposition (CVD) furnace and to analyze their characteristics. The hope is that MDS could be joined with graphene, which has no band gap, and hexagonal boron nitride (hBN), an insulator, to form field-effect transistors, integrated logic circuits, photodetectors and flexible optoelectronics.

"For truly atomic circuitry, this is important," Lou said. "If we get this material to work, then we will have a set of materials to play with for complete, complicated devices."

Last year, Lou and Ajayan revealed their success at making intricate patterns of intertwining graphene and hBN, among them the image of Rice's owl mascot. But there was still a piece missing for the materials to be full partners in advanced electronic applications. By then, the researchers were already well into their study of MDS as a semiconducting solution.

"Two-dimensional materials have taken off," Ajayan said. "The study of graphene prompted research into a lot of 2-D materials; molybdenum disulfide is just one of them. Essentially, we are trying to span the whole range of band gaps between graphene, which is a semimetal, and the boron nitride insulator."

MDS is distinct from graphene and hBN because it isn't exactly flat. Graphene and hBN are flat, with arrays of hexagons formed by their constituent atoms. But while MDS looks hexagonal when viewed from above, it is actually a stack, with a layer of molybdenum atoms between two layers of sulfur atoms.

Co-author Zheng Liu, a joint research scientist in Lou's and Ajayan's labs, noted the Yakobson group predicted that MDS and carbon atoms would bind. "We're working on it," he said. "We would like to stick graphene and MDS together (with hBN) into what would be a novel, 2-D semiconductor component."

"The question now is how to bring all the 2-D materials together," said co-author Sina Najmaei, a Rice graduate student. "They're very different species and they're being grown in very different environments."

Until recently, growing MDS in a usable form has been difficult. The "Scotch tape" method of pulling layers from a bulk sample has been tried, but the resulting materials were inconsistent, Lou said. Early CVD experiments produced MDS with grains that were too tiny to be of use for their electrical properties.

But in the process, the researchers noticed "islands" of MDS tended to form in the furnace where defects or even pieces of dust appeared on the substrate. "The material is difficult to nucleate, unlike hBN or graphene," Najmaei said. "We started learning that we could control that nucleation by adding artificial edges to the substrate, and now it's growing a lot better between these structures."

"Now we can grow grain sizes as large as 100 microns," Lou said. That's still only about the width of a human hair, but in the nanoscale realm, it's big enough to work with, he said.

Once the Ajayan and Lou teams were able to grow such large MDS arrays, the ORNL team imaged the atomic structures using aberration-corrected scanning transmission electron microscopy. The atomic array can clearly be seen in the images and, more importantly, so can the defects that alter the material's electronic properties.

"In order to improve the properties of 2-D materials, it's important to first understand how they're put together at a fundamental scale," Idrobo said. "Our microscopy facility at ORNL allows us to see materials in a way they've never been seen before -- down to the level of individual atoms."

Yakobson, a theoretical physicist, and his team specialize in analyzing the interplay of energy at the atomic scale. With ORNL's images in hand, they were not only able to calculate the energies of a much more complex set of defects than are found in graphene or BN but could also match their numbers to the images.

Among the Yakobson team's interesting finds was the existence, reported last year, of conductive subnano "wires" along grain boundaries in MDS. According to their calculations, the effect only occurred when grains met at precise 60-degree angles. The ORNL electron microscopy images make it possible to view these grain boundaries directly.

The Rice researchers see many possible ways to combine the materials, not only in two-dimensional layers but also as three-dimensional stacks. "Natural crystals are made of structures bound by the van der Waals force, but they're all of the same composition," Lou said. "Now we have the opportunity to build 3-D crystals with different compositions."

"These are very different materials, with different electronic properties and band gaps. Putting one on top of the other would give us a new type of material that we call van der Waals solids," Ajayan said. "We could put them together in whatever stacking order we need, which would be an interesting new approach in materials science.

Co-authors of the Nature Materials paper are Rice research associate Xiaolong Zou, graduate students Gang Shi and Sidong Lei, and Wu Zhou at Oak Ridge National Laboratory.

The Welch Foundation, the National Science Foundation (NSF), the U.S. Army Research Office, the U.S. Office of Naval Research, the Nanoelectronics Research Corporation and the Department of Energy supported the work.

Lou is an associate professor of mechanical engineering and materials science. Ajayan is the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of mechanical engineering and materials science, chemistry and chemical and biomolecular engineering. Yakobson is the Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science and a professor of chemistry.

Computations were performed on Rice's DAVinCI system and at the Cyberinfrastructure for Computational Research, both funded by NSF.

####

About 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 3,708 undergraduates and 2,374 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 has been ranked No. 1 for best quality of life multiple times by the Princeton Review and No. 2 for "best value" among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to tinyurl.com/AboutRiceU.

Follow Rice News and Media Relations via Twitter @RiceUNews

For more information, please click here

Contacts:
Jeff Falk
713-348-6775


Mike Williams
713-348-6728

Copyright © Rice University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Read the abstract at:

Artificially Stacked Atomic Layers: Toward New van der Waals Solids:

Intrinsic Structural Defects in Monolayer Molybdenum Disulfide:

N3L Research Group (Jun Lou):

Ajayan Group:

Yakobson Group:

The Microscopy Group at Oak Ridge National Laboratory:

Related News Press

Graphene

Southampton scientists grow a new challenger to graphene September 23rd, 2014

Twisted graphene chills out: When two sheets of graphene are stacked in a special way, it is possible to cool down the graphene with a laser instead of heating it up, University of Manchester researchers have shown September 22nd, 2014

New research points to graphene as a flexible, low-cost touchscreen solution September 19th, 2014

Biosensors Get a Boost from Graphene Partnership: $5 Million Investment Supports Dozens of Jobs and Development of 300mm Fabrication Process and Wafer Transfer Facility September 18th, 2014

Nanoribbon film keeps glass ice-free: Rice University lab refines deicing film that allows radio frequencies to pass September 16th, 2014

News and information

Future flexible electronics based on carbon nanotubes: Study in Applied Physics Letters show how to improve nanotube transistor and circuit performance with fluoropolymers September 23rd, 2014

Nanotubes help healing hearts keep the beat: Rice University, Texas Children’s Hospital patch for defects enhances electrical connections between cells September 23rd, 2014

Immune system is key ally in cyberwar against cancer: Rice University study yields new two-step strategy for weakening cancer September 23rd, 2014

Los Alamos Researchers Uncover New Properties in Nanocomposite Oxide Ceramics for Reactor Fuel, Fast-Ion Conductors: Misfit dislocations are key to transport properties across material interfaces September 23rd, 2014

Production of Organometallic Frameworks in Least Possible Time September 23rd, 2014

Laboratories

Los Alamos Researchers Uncover New Properties in Nanocomposite Oxide Ceramics for Reactor Fuel, Fast-Ion Conductors: Misfit dislocations are key to transport properties across material interfaces September 23rd, 2014

Physics

Toward optical chips: A promising light source for optoelectronic chips can be tuned to different frequencies September 19th, 2014

Govt.-Legislation/Regulation/Funding/Policy

Southampton scientists grow a new challenger to graphene September 23rd, 2014

Nanotubes help healing hearts keep the beat: Rice University, Texas Children’s Hospital patch for defects enhances electrical connections between cells September 23rd, 2014

Immune system is key ally in cyberwar against cancer: Rice University study yields new two-step strategy for weakening cancer September 23rd, 2014

Los Alamos Researchers Uncover New Properties in Nanocomposite Oxide Ceramics for Reactor Fuel, Fast-Ion Conductors: Misfit dislocations are key to transport properties across material interfaces September 23rd, 2014

Chip Technology

Future flexible electronics based on carbon nanotubes: Study in Applied Physics Letters show how to improve nanotube transistor and circuit performance with fluoropolymers September 23rd, 2014

Twisted graphene chills out: When two sheets of graphene are stacked in a special way, it is possible to cool down the graphene with a laser instead of heating it up, University of Manchester researchers have shown September 22nd, 2014

SouthWest NanoTechnologies (SWeNT) Receives NIST Small Business Innovation Research (SBIR) Phase 1 Award to Produce Greater than 99% Semiconducting Single-Wall Carbon Nanotubes September 19th, 2014

Toward optical chips: A promising light source for optoelectronic chips can be tuned to different frequencies September 19th, 2014

Discoveries

Future flexible electronics based on carbon nanotubes: Study in Applied Physics Letters show how to improve nanotube transistor and circuit performance with fluoropolymers September 23rd, 2014

Nanotubes help healing hearts keep the beat: Rice University, Texas Children’s Hospital patch for defects enhances electrical connections between cells September 23rd, 2014

Immune system is key ally in cyberwar against cancer: Rice University study yields new two-step strategy for weakening cancer September 23rd, 2014

Los Alamos Researchers Uncover New Properties in Nanocomposite Oxide Ceramics for Reactor Fuel, Fast-Ion Conductors: Misfit dislocations are key to transport properties across material interfaces September 23rd, 2014

Announcements

Future flexible electronics based on carbon nanotubes: Study in Applied Physics Letters show how to improve nanotube transistor and circuit performance with fluoropolymers September 23rd, 2014

Nanotubes help healing hearts keep the beat: Rice University, Texas Children’s Hospital patch for defects enhances electrical connections between cells September 23rd, 2014

Immune system is key ally in cyberwar against cancer: Rice University study yields new two-step strategy for weakening cancer September 23rd, 2014

Los Alamos Researchers Uncover New Properties in Nanocomposite Oxide Ceramics for Reactor Fuel, Fast-Ion Conductors: Misfit dislocations are key to transport properties across material interfaces September 23rd, 2014

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals

Southampton scientists grow a new challenger to graphene September 23rd, 2014

Future flexible electronics based on carbon nanotubes: Study in Applied Physics Letters show how to improve nanotube transistor and circuit performance with fluoropolymers September 23rd, 2014

Immune system is key ally in cyberwar against cancer: Rice University study yields new two-step strategy for weakening cancer September 23rd, 2014

Los Alamos Researchers Uncover New Properties in Nanocomposite Oxide Ceramics for Reactor Fuel, Fast-Ion Conductors: Misfit dislocations are key to transport properties across material interfaces September 23rd, 2014

Military

Engineered proteins stick like glue — even in water: New adhesives based on mussel proteins could be useful for naval or medical applications September 22nd, 2014

Engineers show light can play seesaw at the nanoscale: Discovery is another step toward faster and more energy-efficient optical devices for computation and communication September 22nd, 2014

Scientists refine formula for nanotube types: Rice University theorists determine factors that give tubes their chiral angles September 17th, 2014

Nanoribbon film keeps glass ice-free: Rice University lab refines deicing film that allows radio frequencies to pass September 16th, 2014

Research partnerships

Future flexible electronics based on carbon nanotubes: Study in Applied Physics Letters show how to improve nanotube transistor and circuit performance with fluoropolymers September 23rd, 2014

Biosensors Get a Boost from Graphene Partnership: $5 Million Investment Supports Dozens of Jobs and Development of 300mm Fabrication Process and Wafer Transfer Facility September 18th, 2014

The Pocket Project will develop a low-cost and accurate point-of-care test to diagnose Tuberculosis: ICN2 holds a follow-up meeting of the Project on September 18th - 19th September 18th, 2014

Recruiting bacteria to be technology innovation partners: September 17th, 2014

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More














ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE