Doe Science news source
The DOE Science News Source is a Newswise initiative to promote research news from the Office of Science of the DOE to the public and news media.
  • 2017-08-31 10:05:57
  • Article ID: 680366

Controlling Traffic on the Electron Highway: Researching Graphene

Graphene may revolutionize electronics. But first, researchers need to get its electrons under control.

  • Credit: Image courtesy of Lian Li

    Scanning tunneling microscopy image shows a variable-width graphene nanoribbon. Atoms are visible as individual “bumps.”

On an otherwise normal day in the lab, Eva Andrei didn’t expect to make a major discovery. Andrei, a physics professor at Rutgers University, was using graphite – the material in pencils – to calibrate a scanning tunneling microscope. As part of the process, she turned on a very powerful magnetic field. When she looked up to see the material’s electronic spectrum, she was astonished. “We saw huge, beautiful peaks up there, just incredible. And they didn’t make any sense,” she recalled.

Remembering a lecture she’d recently attended, she realized the graphite had separated out into sheets just one atom thick. This material, known as graphene, has bizarre electronic properties. But even for graphene, the spectrum she saw was strange. In fact, no one had ever seen anything like it before. As Andrei described it, her colleague “went berserk in the corridor and just yelled ‘Graphene!’” Andrei had made a serendipitous discovery – a new electric phenomenon.

This was neither the first nor last time that electrons’ movement in graphene would surprise and elate scientists. One of the most impressive things about graphene is how fast electrons move through it. They travel through it more than 100 times faster than they do through the silicon used to make computer chips. In theory, this suggests that manufacturers could use graphene to make superfast transistors for faster, thinner, more powerful touch-screens, electronics, and solar cells.

But what makes graphene so amazing also hinders its use: Electrons flow through its honeycomb structure too easily. Unlike silicon, graphene lacks a bandgap. Bandgaps are the amount of energy an electron must gain to free itself from an atom and move to other atoms to conduct a current. Like a toll on a highway, electrons need to “pay” with energy to proceed. Electronic devices use bandgaps as gates to control where and when electrons flow. Lacking bandgaps, graphene’s structure acts like an electron superhighway with no stop signs.

“Graphene’s electrons are so wild and can’t be tamed; it’s hard to create a gap,” said Andrei.

That lack of a bandgap makes graphene currently very difficult to use in modern electronics. Researchers supported by the Department of Energy’s (DOE’s) Office of Science are investigating ways to overcome this challenge and others to direct graphene’s electron traffic.


Electrons Behaving Like Particles of Light

Materials that are just a few atoms thick act fundamentally different than larger amounts of the same material.

“The biggest challenge is having a reliable understanding of the properties of the materials,” said Lilia Woods, a physics professor at the University of South Florida.

Even for a material that flat, graphene has some odd characteristics. In most materials, electrons move at different speeds. But in graphene, they all move at the same speed. In fact, electrons in graphene act as if they have no mass – like particles of light. That’s one reason why the electrons move so fast and are so difficult to control.


Directing the Electron Traffic

Studying graphene’s behavior is one thing. Figuring out how to manipulate it is another. Scientists have been pursuing several different ways to control the electrons in graphene: developing nanoribbons, stretching it, pairing it with boron nitride (another atom-tall material), and applying electrical charges to empty spaces in it. Scientists pursue multiple approaches because they don’t know which one will work the best. In the meantime, each approach provides its own unique insight into graphene’s basic properties.


Graphene Nanoribbons

Producing graphene nanoribbons is one way to make a material that’s already unimaginably thin, even skinnier. These ribbons maintain many of graphene’s positive characteristics while potentially giving scientists better control over how the electrons behave, including creating bandgaps.

“You can view these little ribbons as electronic circuit elements,” said Michael Crommie, a physicist at DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab).

The investigation of nanoribbons began before scientists even got into the lab. Based on calculations, physicists theorized more than a decade ago that nanoribbons could offer new ways to manipulate graphene’s electronic properties. Experimentalists have confirmed this idea by developing nanoribbons with consistent, clean edges.   

For example, researchers at the University of Wisconsin and elsewhere developed graphene nanoribbons that displayed a bandgap. They showed that when the width of a nanoribbon is smaller than three nanometers, about the thickness of a strand of DNA, it develops a significant bandgap. It also becomes a semiconductor. Unlike graphene’s electron superhighway, semiconductors can switch back and forth between conducting electricity or not. The narrower the ribbon, the bigger the gap or the “energy toll” electrons need.

But one challenge is how to make a single nanoribbon that has multiple widths and therefore regions with different bandgaps. Nanoribbons of a single width won’t give scientists the level of control needed to design complex circuitry. To solve this problem, Berkeley Lab scientists fused together segments of ribbon with different widths. This “bandgap engineering” is essential to manufacturing semiconductor devices and a big step towards using graphene in circuits.

These nanoribbons can’t be used by themselves, so scientists are currently investigating how nanoribbons interact with different surfaces. University of South Florida researchers studied graphene nanoribbons on silicon carbide (SiC) substrates. They found that how certain edges of nanoribbons attach to the SiC substrate influence the bandgap. Nanoribbons with different widths and edges anchored on different substrates can allow scientists more control over electron properties than nanoribbons that aren’t anchored at all.


Stretching Graphene

Stretching graphene offers an alternative path for controlling its properties. When scientists stretch graphene in a specific way, it forms tiny bubbles in which electrons act as if they’re actually in a very powerful magnetic field. These bubbles provide scientists with new opportunities for manipulating electron traffic in graphene.

This discovery was also a complete accident. A team at Berkeley Lab happened to be growing a layer of graphene on the surface of a platinum crystal in a vacuum chamber. As researchers tested the graphene, they noticed that its electrons were acting strangely. Rather than moving as they normally do in a smooth continuum, the electrons in the graphene nanobubbles bunched up at very specific energies. When researchers compared their results to what theory suggested, they found that the electrons were behaving as if they were in an ultra-strong magnetic field. However, there was no actual magnetic field present.

With graphene, “often we’re chasing after one thing and we find something completely unexpected,” Crommie said.


Pairing with Boron Nitride

When scientists first explored graphene’s properties, they placed it on top of silicon dioxide. Because silicon dioxide is a common insulator for electronics applications, it seemed like an ideal match. However, the graphene wasn’t reaching its full potential.

James Hone, a Columbia University mechanical engineering professor, recalled thinking, “Is there a layered material like graphene that would be a natural fit?”

Hone’s team eventually discovered that graphene works much better when you put it on boron nitride instead. Like graphene, boron nitride can be made only a few atoms thick and has the same honeycomb structure. However, it’s an insulator that impedes electrons from moving through it.

They found that putting boron nitride and graphene together can produce a new material whose properties are very flexible. This combination is so promising that Alex Zettl from Berkeley Lab joked that his lab is now “Boron Nitride R Us.” He commented, “Having the boron nitride influence the graphene is a very powerful tool.”

Ordinary light may offer a way to influence electrons in this new composite material. Berkeley Lab scientists have found that they can use light from a simple lamp to create an essential semiconductor device called a “p-n junction.” P-n junctions have one side that’s positive and lacks electrons and another side that’s negative with extra electrons. By carefully designing these junctions, engineers can control how and when electrons move between the two sides of a material. They’re like the gates that lift up and down at a toll booth.

Scientists realized that if they could put fixed, static charges in the boron nitride in a specific way, they could generate a p-n junction in the nearby graphene.  To create the p-n junction, the scientists first prepared the graphene highway to have an excess of electrons, or be an n-type region. Then, by shining a light on the underlying boron nitride, they created a pothole, or p-type region, in the graphene. So with a light pulse and the boron nitride as a mediator, they could “write” p-n junctions – toll gates – into the graphene as needed. 

Even after scientists turned off the light, the activation of the boron nitride and its influence on the electron traffic in the nearby graphene, stayed in place for days. The scientists also discovered that they could erase and re-create these junctions, which could be important for designing electronic devices.

Now researchers are using scanning tunneling microscopes, which use nanometer-sized tips to conduct electricity, to do the same thing with more precision.


Charging Up Empty Spaces in Graphene

Because of its unique structure, graphene remains stable even when scientists punch holes in it. Andrei’s team from Rutgers University took advantage of this fact to create an “artificial atom” that influences nearby electrons in the undamaged part of graphene. First, researchers shot helium at graphene on a substrate, knocking out a single carbon atom. They then used a scanning tunneling microscope to apply a positive charge to the substrate under the empty space where the missing atom used to sit. Like a real atom, that positive charge influenced the orbits of electrons in the surrounding graphene. Creating these artificial atoms could be another way that future devices could control electron flow in graphene.


The Future of Graphene

Perhaps the most surprising of these twists and turns is that the future may not lie in graphene at all. As scientists investigated graphene’s unique electronic properties, they discovered new extremely thin materials made from elements other than carbon. If a material is only a few atoms thick and has a honeycomb structure, it can demonstrate many of graphene’s electronic properties. In fact, scientists have found materials made of silicon, germanium, and tin that act strikingly similar to graphene. Using these materials by themselves or in combination with graphene may offer better characteristics than graphene alone.

In the meantime, scientists will continue to investigate the strange features of this frequently surprising material. As Philip Kim, a Harvard University physics professor said, “[Graphene] always provides you with some new, exciting science that we have not expected.”

The Office of Science is the single largest supporter of basic energy research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information please visit

Shannon Brescher Shea is a Senior Writer/Editor in the Office of Science,

  • Filters

  • × Clear Filters

High-Speed Movie Aids Scientists Who Design Glowing Molecules

In a recent experiment conducted at the Department of Energy's SLAC National Accelerator Laboratory, a research team used bright, ultrafast X-ray pulses from SLAC's X-ray free-electron laser to create a high-speed movie of a fluorescent protein in action. With that information, the scientists began to design a marker that switches more easily, a quality that can improve resolution during biological imaging.

Biomass-Produced Electricity in the US Possible, but It'll Cost

If the U.S. wants to start using wood pellets to produce energy, either the government or power customers will have to pay an extra cost, a new University of Georgia study has found.

Scientists Make Atoms-Thick Post-It Notes for Solar Cells and Circuits

In a study published Sept. 20 in Nature, UChicago and Cornell University researchers describe an innovative method to make stacks of semiconductors just a few atoms thick. The technique offers scientists and engineers a simple, cost-effective method to make thin, uniform layers of these materials, which could expand capabilities for devices from solar cells to cell phones.

Titan Helps Researchers Suck Mystery Out of Cell's 'Vacuum Cleaners'

In cancer cells, a membrane transport protein called P-glycoprotein, or Pgp, actively pumps anticancer drugs out of the cell, contributing to multidrug resistance. Recently, a team led by computational biophysicist Emad Tajkhorshid from the University of Illinois at Urbana-Champaign (UIUC) used the Titan supercomputer to uncover new details about Pgp that could help the drug discovery community manipulate Pgp function.

Laser-Free Method of Ion Cooling Has Range of Potential Uses

Prof. Daniel Zajfman's universal ion trap cools to a tenth of a degree above absolute zero. The new method does not depend on the type or the weight of the ion and, thus, might be used to investigate the properties of large biological molecules or nanoparticles, among other things.

Tiny Lasers from a Gallery of Whispers

Whispering gallery mode resonators rely on a phenomenon similar to an effect observed in circular galleries, and the same phenomenon applies to light. When light is stored in ring-shaped or spherical active resonators, the waves superimpose in such a way that it can result in laser light. This week in APL Photonics, investigators report a new type of dye-doped WGM micro-laser that produces light with tunable wavelengths.

Copper Catalyst Yields High Efficiency CO2-to-Fuels Conversion

Berkeley Lab scientists have developed a new electrocatalyst that can directly convert carbon dioxide into multicarbon fuels and alcohols using record-low inputs of energy. The work is the latest in a round of studies coming out of Berkeley Lab tackling the challenge of a creating a clean chemical manufacturing system that can put carbon dioxide to good use.

Solar-to-Fuel System Recycles CO2 to Make Ethanol and Ethylene

Berkeley Lab scientists have harnessed the power of photosynthesis to convert carbon dioxide into fuels and alcohols at efficiencies far greater than plants. The achievement marks a significant advance in the effort to move toward sustainable sources of fuel.

New Evidence for Small, Short-Lived Drops of Early Universe Quark-Gluon Plasma?

UPTON, NY--Particles emerging from even the lowest energy collisions of small deuterons with large heavy nuclei at the Relativistic Heavy Ion Collider (RHIC)--a U.S. Department of Energy Office of Science User Facility for nuclear physics research at DOE's Brookhaven National Laboratory--exhibit behavior scientists associate with the formation of a soup of quarks and gluons, the fundamental building blocks of nearly all visible matter.

New Insights Into Nanocrystal Growth in Liquid

PNNL researchers have measured the forces that cause certain crystals to assemble, revealing competing factors that researchers might be able to control. The work has a variety of implications in both discovery and applied science. In addition to providing insights into the formation of minerals and semiconductor nanomaterials, it might also help scientists understand soil as it expands and contracts through wetting and drying cycles.

  • Filters

  • × Clear Filters

PPPL Physicist Francesca Poli Named ITER Scientist Fellow

Article describes new ITER Scientist Fellow.

Los Alamos Gains Role in High-Performance Computing for Materials Program

A new high-performance computing initiative announced this week by the U.S. Department of Energy will help U.S. industry accelerate the development of new or improved materials for use in severe environments.

UK Commits $88 Million to LBNF/DUNE in First-Ever Umbrella Science Agreement with U.S.

The UK has committed $88 million to the Long-Baseline Neutrino Facility and Deep Underground Neutrino Experiment as part of an umbrella science and technology agreement with the United States.

Wayne State Receives $1.2 Million NSF Grant to Develop Autonomous Battery Operating System

Researchers at Wayne State University led by Nathan Fisher, associate professor of computer science in the College of Engineering, received a $1.2 million grant from the National Science Foundation to address the need for effective, integrative battery operating systems that provide sustained and reliable power.

UAH leads effort that secures $20 million grant from the National Science Foundation

A partnership comprising nine universities in Alabama, including The University of Alabama in Huntsville (UAH) as the lead institution, has been awarded a $20 million, five-year grant by the National Science Foundation's Experimental Program to Stimulate Competitive Research (EPSCoR).

Sandia Labs Wins 5 Regional Technology Transfer Awards

Sandia National Laboratories won five awards from the 2017 Federal Laboratory Consortium for its work to develop and commercialize innovative technologies.

Tulane Receives Grant to Reduce Auto Emissions

Members of Tulane University's Shantz Lab will work with industrial scientists to assist in the development of next-generation materials designed to reduce harmful automotive emissions. The three-year old lab and its group of students have received a grant and equipment resources from SACHEM, Inc., a chemical science company.

Lab Leads New Effort in Materials Development

Lawrence Livermore National Lab will be part of a multi-lab effort to apply high-performance computing to US-based industry's discovery, design, and development of materials for severe environments under a new initiative announced by the Department of Energy (DOE) on Sept. 19.

ORNL Innovation Crossroads Program Opens Second Round of Energy Entrepreneurial Fellowships

Entrepreneurs are invited to apply for the second round of Oak Ridge National Laboratory's Innovation Crossroads program.

Los Alamos Recognized as Top Diversity Employer

For the second straight year, Los Alamos National Laboratory was recognized as a top diversity employer by LATINA Style and STEM Workforce Diversity magazine.

  • Filters

  • × Clear Filters

Fungi: Gene Activator Role Discovered

Specific modifications to fungi DNA may hold the secret to turning common plant degradation agents into biofuel producers.

First Look at a Living Cell Membrane

Neutrons provide the solution to nanoscale examination of living cell membrane and confirm the existence of lipid rafts.

High Yield Biomass Conversion Strategy Ready for Commercialization

Researchers convert 80 percent of biomass into high-value products with strategy that's ready for commercialization.

Consequences of Drought Stress on Biofuels

Switchgrass cultivated during a year of severe drought inhibited microbial fermentation and resulting biofuel production.

Clay Minerals and Metal Oxides Change How Uranium Travels Through Sediments

Montmorillonite clays prevent uranium from precipitating from liquids, letting it travel with groundwater.

Tundra Loses Carbon with Rapid Permafrost Thaw

Seven-year-study shows plant growth does not sustainably balance carbon losses from solar warming and permafrost thaw.

Crystals Grow by Twisting, Aligning and Snapping Together

Van der Waals force, which that enables tiny crystals to grow, could be used to design new materials.

Vitamin B12 Fuels Microbial Growth

Scarce compound, vitamin B12, is key for cellular metabolism and may help shape microbial communities that affect environmental cycles and bioenergy production.

Carbon in Floodplain Unlikely to Cycle into the Atmosphere

Microbes leave a large fraction of carbon in anoxic sediments untouched, a key finding for understanding how watersheds influence Earth's ecosystem.

Bacterial Cell Wall Changes Produce More Fatty Molecules

New strategy greatly increases the production and secretion of biofuel building block lipids in bacteria able to grow at industrial scales.


Thursday September 21, 2017, 03:05 PM

From Science to Finance: SLAC Summer Interns Forge New Paths in STEM

SLAC National Accelerator Laboratory

Thursday September 07, 2017, 02:05 PM

Students Discuss 'Cosmic Opportunities' at 45th Annual SLAC Summer Institute

SLAC National Accelerator Laboratory

Thursday August 31, 2017, 05:05 PM

Binghamton University Opens $70 Million Smart Energy Building

Binghamton University, State University of New York

Wednesday August 23, 2017, 05:05 PM

Widening Horizons for High Schoolers with Code

Argonne National Laboratory

Saturday May 20, 2017, 12:05 PM

Rensselaer Polytechnic Institute Graduates Urged to Embrace Change at 211th Commencement

Rensselaer Polytechnic Institute (RPI)

Monday May 15, 2017, 01:05 PM

ORNL, University of Tennessee Launch New Doctoral Program in Data Science

Oak Ridge National Laboratory

Friday April 07, 2017, 11:05 AM

Champions in Science: Profile of Jonathan Kirzner

Department of Energy, Office of Science

Wednesday April 05, 2017, 12:05 PM

High-Schooler Solves College-Level Security Puzzle From Argonne, Sparks Interest in Career

Argonne National Laboratory

Tuesday March 28, 2017, 12:05 PM

Champions in Science: Profile of Jenica Jacobi

Department of Energy, Office of Science

Friday March 24, 2017, 10:40 AM

Great Neck South High School Wins Regional Science Bowl at Brookhaven Lab

Brookhaven National Laboratory

Wednesday February 15, 2017, 04:05 PM

Middle Schoolers Test Their Knowledge at Science Bowl Competition

Argonne National Laboratory

Friday January 27, 2017, 04:00 PM

Haslam Visits ORNL to Highlight State's Role in Discovering Tennessine

Oak Ridge National Laboratory

Tuesday November 08, 2016, 12:05 PM

Internship Program Helps Foster Development of Future Nuclear Scientists

Oak Ridge National Laboratory

Friday May 13, 2016, 04:05 PM

More Than 12,000 Explore Jefferson Lab During April 30 Open House

Thomas Jefferson National Accelerator Facility

Monday April 25, 2016, 05:05 PM

Giving Back to National Science Bowl

Ames Laboratory

Friday March 25, 2016, 12:05 PM

NMSU Undergrad Tackles 3D Particle Scattering Animations After Receiving JSA Research Assistantship

Thomas Jefferson National Accelerator Facility

Tuesday February 02, 2016, 10:05 AM

Shannon Greco: A Self-Described "STEM Education Zealot"

Princeton Plasma Physics Laboratory

Monday November 16, 2015, 04:05 PM

Rare Earths for Life: An 85th Birthday Visit with Mr. Rare Earth

Ames Laboratory

Tuesday October 20, 2015, 01:05 PM

Meet Robert Palomino: 'Give Everything a Shot!'

Brookhaven National Laboratory

Tuesday April 22, 2014, 11:30 AM

University of Utah Makes Solar Accessible

University of Utah

Wednesday March 06, 2013, 03:40 PM

Student Innovator at Rensselaer Polytechnic Institute Seeks Brighter, Smarter, and More Efficient LEDs

Rensselaer Polytechnic Institute (RPI)

Friday November 16, 2012, 10:00 AM

Texas Tech Energy Commerce Students, Community Light up Tent City

Texas Tech University

Wednesday November 23, 2011, 10:45 AM

Don't Get 'Frosted' Over Heating Your Home This Winter

Temple University

Wednesday July 06, 2011, 06:00 PM

New Research Center To Tackle Critical Challenges Related to Aircraft Design, Wind Energy, Smart Buildings

Rensselaer Polytechnic Institute (RPI)

Friday April 22, 2011, 09:00 AM

First Polymer Solar-Thermal Device Heats Home, Saves Money

Wake Forest University

Friday April 15, 2011, 12:25 PM

Like Superman, American University Will Get Its Energy from the Sun

American University

Thursday February 10, 2011, 05:00 PM

ARRA Grant to Help Fund Seminary Building Green Roof

University of Chicago

Tuesday December 07, 2010, 05:00 PM

UC San Diego Installing 2.8 Megawatt Fuel Cell to Anchor Energy Innovation Park

University of California San Diego

Monday November 01, 2010, 12:50 PM

Rensselaer Smart Lighting Engineering Research Center Announces First Deployment of New Technology on Campus

Rensselaer Polytechnic Institute (RPI)

Friday September 10, 2010, 12:40 PM

Ithaca College Will Host Regional Clean Energy Summit

Ithaca College

Tuesday July 27, 2010, 10:30 AM

Texas Governor Announces $8.4 Million Award to Create Renewable Energy Institute

Texas Tech University

Friday May 07, 2010, 04:20 PM

Creighton University to Offer New Alternative Energy Program

Creighton University

Wednesday May 05, 2010, 09:30 AM

National Engineering Program Seeks Subject Matter Experts in Energy

JETS Junior Engineering Technical Society

Wednesday April 21, 2010, 12:30 PM

Students Using Solar Power To Create Sustainable Solutions for Haiti, Peru

Rensselaer Polytechnic Institute (RPI)

Wednesday March 03, 2010, 07:00 PM

Helping Hydrogen: Student Inventor Tackles Challenge of Hydrogen Storage

Rensselaer Polytechnic Institute (RPI)

Thursday February 04, 2010, 02:00 PM

Turning Exercise into Electricity

Furman University

Thursday November 12, 2009, 12:45 PM

Campus Leaders Showing the Way to a Sustainable, Clean Energy Future

National Wildlife Federation (NWF)

Tuesday November 03, 2009, 04:20 PM

Furman University Receives $2.5 Million DOE Grant for Geothermal Project

Furman University

Thursday September 17, 2009, 02:45 PM

Could Sorghum Become a Significant Alternative Fuel Source?

Salisbury University

Wednesday September 16, 2009, 11:15 AM

Students Navigating the Hudson River With Hydrogen Fuel Cells

Rensselaer Polytechnic Institute (RPI)

Wednesday September 16, 2009, 10:00 AM

College Presidents Flock to D.C., Urge Senate to Pass Clean Energy Bill

National Wildlife Federation (NWF)

Wednesday July 01, 2009, 04:15 PM

Northeastern Announces New Professional Master's in Energy Systems

Northeastern University

Friday October 12, 2007, 09:35 AM

Kansas Rural Schools To Receive Wind Turbines

Kansas State University

Thursday August 17, 2006, 05:30 PM

High Gas Prices Here to Stay, Says Engineering Professor

Rowan University

Wednesday May 17, 2006, 06:45 PM

Time Use Expert's 7-Year Fight for Better Gas Mileage

University of Maryland, College Park

Showing results

0-4 Of 2215