[Image above] Credit: Scott Swigart; Flickr CC BY 2.0
Editor’s note: This story originally appeared in print in the August 2016 ACerS Bulletin.
The potential applications for graphene are seemingly endless.
Graphene’s single-layer thickness, toughness, and supreme mechanical and thermal properties make it an ideal choice for developing electronic, optoelectronic, and electromechanical devices and sensors.
Of course we all know by now that the struggle to scale up commercially viable graphene for electronic applications is real. But in recent news, graphene’s been teaming up with other materials to boost its electronic properties.
Earlier this year, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory, Stony Brook University, and the Colleges of Nanoscale Science and Engineering at SUNY Polytechnic Institute developed a simple and powerful method for creating resilient, customized, and high-performing graphene: layering it on top of soda-lime glass.
“We believe that this work could significantly advance the development of truly scalable graphene technologies,” Matthew Eisaman, study coauthor and physicist at Brookhaven Lab and professor at SBU, said in a Brookhaven news release at the time.
And graphene’s partnerships don’t stop at glass—the material has also been known to pair up with alumina to create strong, wear-resistant ceramic composites.
Now, graphene’s upgrading its role from partnership to trio when it comes to harnessing its electronic properties for scale-up potential.
Researchers at the University of California Riverside and the University of Georgia (Athens, Ga.) say they’ve integrated graphene with two other 2-D materials—tantalum sulfide (TaS2) and hexagonal boron nitride—to create a simple, compact, and fast voltage-controlled oscillator (VCO) device—the “first useful device that exploits the potential of charge-density waves to modulate an electrical current through a 2-D material,” according a recent UCR Today article.
Although graphene’s single-layer thickness and exceptional electrical and thermal conduction capabilities make it ideal for use in electronic applications, the material itself is limited by its inability to function as a semiconductor—a property that’s crucial for the “on and off switch” operation employed by so many electronic components, the article explains.
To overcome this limitation, the researchers incorporated the use of TaS2 into the VCO device prototype—an addition that enabled the device to function as an electric switch at room temperature.
“There are many charge-density wave materials that have interesting electrical switching properties. However, most of them reveal these properties at very low temperature only. The particular polytype of TaS2 that we used can have abrupt changes in resistance above room temperature. That made a crucial difference,” Alexander Balandin, UC presidential chair professor of electrical and computer engineering in UCR’s Bourns College of Engineering and lead researcher, explains in the article.
But TaS2 requires protection from environmental damage to stand up to regular wear-and-tear—so the researchers coated it with another 2-D material, hexagonal boron nitride, to prevent oxidation. By pairing the boron nitride-capped TaS2 with graphene, the team constructed a three-layer VCO that could pave the way for post-silicon electronics in everything from computers to clocks to radios.
The team’s VCO design outlines graphene’s function as “an integrated tunable load resistor, which enables precise voltage control of the current and VCO frequency,” the article explains. And the thin, flexible nature of the device would make it ideal for use in wearable technologies.
“It is difficult to compete with silicon, which has been used and improved for the past 50 years. However, we believe our device shows a unique integration of three very different 2-D materials, which utilizes the intrinsic properties of each of these materials. The device can potentially become a low-power alternative to conventional silicon technologies in many different applications,” adds Balandin.
The research, published in Nature Nanotechnology, is “A charge-density-wave oscillator based on an integrated tantalum disulﬁde–boron nitride–graphene device operating at room temperature” (DOI: 10.1038/NNANO.2016.108).