Graphene is a one-atom-thick layer of carbon that conducts electricity with little resistance or heat generation. After its discovery in 2004 - which earned a Nobel Prize in physics - it was touted as a potential replacement for silicon, possibly leading to ultrafast devices with simplified circuits that might be less expensive to manufacture.
However, graphene's luster has dulled in recent years for digital applications as researchers have discovered that it has no "band gap," a trait that is needed to switch on and off, which is critical for digital transistors.
"The fact that graphene is a zero-band-gap material by nature has raised many questions in terms of its usefulness for digital applications," said Purdue doctoral student Hong-Yan Chen.
Electrons in semiconductors like silicon exist at two energy levels, known as the valence and conduction bands. The energy gap between these two levels is called the band gap. Having the proper band gap enables transistors to turn on and off, which allows digital circuits to store information in binary code consisting of sequences of ones and zeroes.
Chen has led a team of researchers in creating a new type of graphene inverter, a critical building block of digital transistors. Other researchers have created graphene inverters, but they had to be operated at 77 degrees Kelvin, which is minus 196 Celsius (minus 320 Fahrenheit).
"If graphene could be used in digital applications, that would be really important," said Chen, who is working with Joerg Appenzeller, a professor of electrical and computer engineering and scientific director of nanoelectronics at Purdue's Birck Nanotechnology Center.
The Purdue researchers are the first to create graphene inverters that work at room temperature and have a gain larger than one, a basic requirement for digital electronics that enables transistors to amplify signals and control its switching from 0 to 1.
Findings were detailed in a paper, "Complementary-Type Graphene Inverters Operating at Room-Temperature," presented in June during the 2011 Device Research Conference in Santa Barbara, Calif.
Thus far graphene transistors have been practical only for specialized applications, such as amplifiers for cell phones and military systems. However, the new inverters represent a step toward learning how to use the material to create graphene transistors for broader digital applications that include computers and consumer electronics.
To create electronic devices, silicon is impregnated with impurities to change its semiconducting properties. Such "doping" is not easily applicable to graphene. However, the researchers have potentially solved this problem by developing "electrostatic doping," which makes it possible for graphene inverters to mimic the characteristics of silicon inverters.
Electrostatic doping is induced through the electric field between metal gates, which are located 40 nanometers away from graphene channels. The doping can be altered by varying the voltage, enabling researchers to test specific doping levels.
"This will allow us to find the sweet spot for operating the device," Chen said.
Further work will be needed to integrate the prototype into a working graphene circuit for digital applications.
The research is based at the Birck Nanotechnology Center in Purdue's Discovery Park.
A publication-quality photo is available at http://news.uns.purdue.edu/images/2011/appenzeller-graphene.jpg
Abstract on the research in this release is available at: http://www.purdue.edu/newsroom/research/2011/110906AppenzellerGraphene.html
Emil Venere | EurekAlert!
Manchester scientists tie the tightest knot ever achieved
13.01.2017 | University of Manchester
CWRU directly measures how perovskite solar films efficiently convert light to power
12.01.2017 | Case Western Reserve University
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.
Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Power and Electrical Engineering
16.01.2017 | Information Technology
16.01.2017 | Power and Electrical Engineering