Cornell scientists review future of graphene

Nov 09, 2011 By Anne Ju
A false-color microscopy image of a 30-by-30 micron square of graphene covering a square trench to form a nanomechanical resonator. These devices, which are the thinnest possible microelectromechanical systems and are useful for sensing and signal processing, can now be batch-fabricated as a result of recent advances in graphene fabrication technology.

(PhysOrg.com) -- Graphene is sort of a scientific rock star, with countless groups studying its amazing electrical properties and tensile strength and dreaming up applications ranging from flat-panel screens to elevators in space.

The single-layer carbon sheets' stellar qualities are only just being understood in all their capacities, say scientists at Cornell -- and researchers can dream big (or rather, very small) when it comes to everything can offer.

That's what scientists in the lab of Harold Craighead, the Charles W. Lake Professor of Engineering, say in an American Vacuum Society online review article, Sept. 9, about graphene's present and future. The article made the cover of the printed journal and quickly became one of its most-downloaded pieces.

"It's becoming clear that with modern , you can imagine turning graphene into a technology," said Robert A. Barton, graduate student and lead author. "People often focus on the of graphene, and they don't really think as much of its mechanical applications."

It's precisely this area where Cornell has produced some pioneering work. In particular the Craighead group, in collaboration with others including Jiwoong Park, assistant professor of chemistry and , and Paul McEuen, the Goldwin Smith Professor of Physics, has used graphene in nanoelectromechanical systems (NEMS), analogous to an earlier generation's (MEMS).

"We've moved beyond working with little exfoliated flakes and more with grown materials that can be incorporated and connected with electronics and other mechanics," Craighead said. "So the question is, can you make these reliably, uniformly and reproducibly?"

It was only a few years ago that scientists figured out how to make arrays of hundreds of thousands of graphene devices using a process called chemical vapor deposition. This involves growing the single-layer sheets of honeycomb-latticed carbon atoms on top of copper, then manipulating the graphene to make devices.

One of the Cornell researchers' devices is like a drum head -- a piece of graphene, one atom thick, suspended over a hollow well. Although growth of graphene by on copper was invented elsewhere, Cornell researchers were the first to figure out how to make mechanical resonators from the large-area material.

"Four years ago we were able to make about one, and that took several months," Barton said. Speeding up the fabrication process has greatly increased graphene's potential in devices.

At Cornell, Barton and colleagues are working on making mass sensors out of graphene, which is atomically structured so it's sensitive to both mass and electric charge. What can result is that a bit of mass landing on a surface of suspended graphene will perturb the mechanical and electronic structure simultaneously, analogous to today's mass spectrometry but on a much smaller and more sensitive level, Barton explained.

The Cornell researchers are using optical interferometry to monitor the motion of a sheet of graphene. In this technique, the subtle device motions are read as variations in reflected light intensity, which are monitored by a fast photodiode connected to a spectrum analyzer. Another group at Cornell, led by McEuen, had earlier developed a way to "read out" carbon nanotubes, a technique that can also apply to graphene, Barton said.

The rapid progress of graphene makes its future very exciting, Craighead said.

"Graphene has gone from an oddity in a physics lab to something that can be practically incorporated into a variety of potential devices," he said. "The ability to fabricate things in these ways, to integrate them and to use them for different types of sensors, physical and chemical, is quite a step forward in a short time, and our group is one of the many that's contributed to this."

Explore further: Nanoparticles give up forensic secrets

Related Stories

Graphene grains make atom-thick patchwork 'quilts'

Jan 05, 2011

(PhysOrg.com) -- A quick look at new Cornell research hints at colorful patchwork quilts, but they are actually pictures of graphene -- one atom-thick sheets of carbon stitched together at tilted interfaces. ...

Seeing an atomic thickness

May 19, 2011

Scientists from NPL, in collaboration with Linkoping University, Sweden, have shown that regions of graphene of different thickness can be easily identified in ambient conditions using Electrostatic Force ...

Producing graphene layers using crystallization

Mar 02, 2010

(PhysOrg.com) -- Ever since it's relatively recent discovery, graphene has generated a great deal of interest. Graphene is extracted from graphite in many cases, and consists of a sheet of carbon atoms bound together in a ...

Hydrogen may be key to growth of high-quality graphene

Jul 18, 2011

A new approach to growing graphene greatly reduces problems that have plagued researchers in the past and clears a path to the crystalline form of graphite's use in sophisticated electronic devices of tomorrow.

Recommended for you

Nanoparticles give up forensic secrets

7 hours ago

A group of researchers from Switzerland has thrown light on the precise mechanisms responsible for the impressive ability of nanoparticles to detect fingermarks left at crime scenes.

Blades of grass inspire advance in organic solar cells

Sep 30, 2014

Using a bio-mimicking analog of one of nature's most efficient light-harvesting structures, blades of grass, an international research team led by Alejandro Briseno of the University of Massachusetts Amherst ...

How to make a "perfect" solar absorber

Sep 29, 2014

The key to creating a material that would be ideal for converting solar energy to heat is tuning the material's spectrum of absorption just right: It should absorb virtually all wavelengths of light that ...

User comments : 0