Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

UWM discovery advances graphene-based electronics

17.04.2012
Scientists and engineers at the University of Wisconsin-Milwaukee (UWM) have discovered an entirely new carbon-based material that is synthesized from the “wonder kid” of the carbon family, graphene. The discovery, which the researchers are calling “graphene monoxide (GMO),” pushes carbon materials closer to ushering in next-generation electronics.
Graphene, a one-atom-thick layer of carbon that resembles a flat sheet of chicken wire at nanoscale, has the potential to revolutionize electronics because it conducts electricity much better than the gold and copper wires used in current devices. Transistors made of silicon are approaching the minimum size at which they can be effective, meaning the speed of devices will soon bottom out. Carbon materials at nanoscale could be the remedy.

Now all three characteristics of electrical conductivity – conducting, insulating and semiconducting – are found in the carbon family, offering needed compatibility for use in future electronics.
Currently, applications for graphene are limited because it’s too expensive to mass produce. Another problem is that, until now, graphene-related materials existed only as conductors or insulators.

“A major drive in the graphene research community is to make the material semiconducting so it can be used in electronic applications,” says Junhong Chen, professor of mechanical engineering and a member of the research team. “Our major contribution in this study was achieved through a chemical modification of graphene.”

GMO exhibits characteristics that will make it easier to scale up than graphene. And, like silicon in the current generation of electronics, GMO is semiconducting, necessary for controlling the electrical current in such a strong conductor as graphene. Now all three characteristics of electrical conductivity – conducting, insulating and semiconducting – are found in the carbon family, offering needed compatibility for use in future electronics.

Mixing theory and experiments
The team created GMO while conducting research into the behavior of a hybrid nanomaterial engineered by Chen that consists of carbon nanotubes (essentially, graphene rolled into a cylinder) decorated with tin oxide nanoparticles. Chen uses his hybrid material to make high-performance, energy-efficient and inexpensive sensors.

To image the hybrid material as it was sensing, he and physics professor Marija Gajdardziska used a high-resolution transmission electron microscope (HRTEM). But to explain what was happening, the pair needed to know which molecules were attaching to the nanotube surface, which were attaching to the tin oxide surface, and how they changed upon attachment.

So the pair turned to physics professor Carol Hirschmugl, who recently pioneered a method of infrared imaging (IR) that not only offers high-definition images of samples, but also renders a chemical “signature” that identifies which atoms are interacting as sensing occurs.

Chen and Gajdardziska knew they would need to look at more attachment sites than are available on the surface of a carbon nanotube. So they “unrolled” the nanotube into a sheet of graphene to achieve a larger area.

That prompted them to search for ways to make graphene from its cousin, graphene oxide (GO), an insulator that can be scaled up inexpensively. GO consists of layers of graphene stacked on top of one another in an unaligned orientation. It is the subject of much research as scientists look for cheaper ways to replicate graphene’s superior properties.

Puzzling outcome
Physics senior scientist Marvin Schofield (standing), physics doctoral student Eric Mattson, and Graduate School associate dean and physics professor Marija Gajdardziska examine the images of GMO using Selected Area Electron Diffraction (SAED) in a transmission electron microscope.

In one experiment, they heated the GO in a vacuum to reduce oxygen. Instead of being destroyed, however, the carbon and oxygen atoms in the layers of GO became aligned, transforming themselves into the “ordered,” semiconducting GMO – a carbon oxide that does not exist in nature.

It was not the result they expected.

“We thought the oxygen would go away and leave multilayered graphene, so the observation of something other than that was a surprise,” says Eric Mattson, a doctoral student of Hirschmugl’s.

At different high temperatures, the team actually produced four new materials that they collectively refer to as GMO. They captured video of the process using Selected Area Electron Diffraction (SAED) in a transmission electron microscope.

Because GMO is formed in single sheets, Gajdardziska says the material could have applications in products that involve surface catalysis. She, Hirschmugl and Chen also are exploring its use in the anode parts of lithium-ion batteries, which could make them more efficient.

Laborious process

But the next step is more science. The team will need to find out what triggered the reorganization of the material, and also what conditions would ruin the GMO’s formation.

“In the reduction process, you expect to lose oxygen,” says Michael Weinert, professor of physics and director of UWM’s Laboratory for Surface Studies. “But we actually gained more oxygen content. So we’re at a point where we’re still learning more about it.”

Weinert points out that they have only made GMO at a small scale in a lab and are not certain what they will encounter in scaling it up.

The team had to be careful in calculating how electrons flowed across GMO, he adds. Interactions that occur had to be interpreted through a painstaking process of tracking indicators of structure and then eliminating those that didn’t fit.

“It was a long process,” says Weinert, “not one of those ‘Eureka!’ moments.”

This work was published in the journal ACS Nano (5[12], 9710-9717, 2011). In addition to the four UWM faculty members and Mattson (the lead author), the team included UWM physics research associate Marvin Schofield and postdoctoral associate Michael Nasse, UWM engineering graduate students Haihui Pu and Shumao Cui, UWM engineering research associate Ganhua Lu, and Rodney Ruoff of the University of Texas at Austin.

Junhong Chen | EurekAlert!
Further information:
http://www.uwm.edu

More articles from Physics and Astronomy:

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

nachricht Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Machine-learning predicted a superhard and high-energy-density tungsten nitride

18.07.2018 | Materials Sciences

NYSCF researchers develop novel bioengineering technique for personalized bone grafts

18.07.2018 | Life Sciences

Why might reading make myopic?

18.07.2018 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>