Future computers may run a little sweeter, thanks to a refinement in the manufacture of graphene at Rice University.
Rice researchers have learned to make pristine sheets of graphene, the one-atom-thick form of carbon, from plain table sugar and other carbon-based substances. They do so in a one-step process at temperatures low enough to make graphene easy to manufacture.
The lab of Rice chemist James Tour reported in the online version of the journal Nature this week that large-area, high-quality graphene can be grown from a number of carbon sources at temperatures as low as 800 degrees Celsius (1,472 F). As hot as that may seem, the difference between running a furnace at 800 and 1,000 degrees Celsius is significant, Tour said.
"At 800 degrees, the underlying silicon remains active for electronics, whereas at 1,000 degrees, it loses its critical dopants," said Tour, Rice's T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science.
Zhengzong Sun, a fourth-year graduate student in Tour's lab and primary author of the paper, found that depositing carbon-rich sources on copper and nickel substrates produced graphene in any form he desired: single-, bi- or multilayer sheets that could be highly useful in a number of applications.
Sun and his colleagues also found the process adapts easily to producing doped graphene; this allows the manipulation of the material's electronic and optical properties, which is important for making switching and logic devices.
For pristine graphene, Sun started with a thin film of poly (methyl methacrylate) (PMMA) -- perhaps best known in its commercial guise as Plexiglas -- spun onto a copper substrate that acted as a catalyst. Under heat and low pressure, flowing hydrogen and argon gas over the PMMA for 10 minutes reduced it to pure carbon and turned the film into a single layer of graphene. Changing the gas-flow rate allowed him to control the thickness of the PMMA-derived graphene.
Then it got more interesting, Sun said. He turned to other carbon sources, including a fine powder of sucrose -- aka table sugar. "We thought it would be interesting to try this stuff," Sun said. "While other labs were changing the metal catalysts, we tried changing the carbon sources."
Sun put 10 milligrams of sugar (and later fluorene) on a square-centimeter sheet of copper foil and subjected it to the same reactor conditions as the PMMA. It was quickly transformed into single-layer graphene. Sun had expected defects in the final product, given the chemical properties of both substances (a high concentration of oxygen in sucrose, five-atom rings in fluorene); but he found potential topological defects would self-heal as the graphene formed.
"As we looked deeper and deeper into the process, we found it was not only interesting, but useful," Sun said.
He tried and failed to grow graphene on silicon and silicon oxide, which raised the possibility of growing patterned graphene from a thin film of shaped copper or nickel deposited onto silicon wafers.
Doped graphene opens more possibilities for electronics use, Tour said, and Sun found it fairly simple to make. Starting with PMMA mixed with a doping reagent, melamine, he discovered that flowing the gas under atmospheric pressure produced nitrogen-doped graphene. Pristine graphene has no bandgap, but doped graphene allows control of the electrical structure, which the team proved by building field-effect transistors.
"Each day, the growth of graphene on silicon is approaching industrial-level readiness, and this work takes it an important step further," Tour said.
Co-authors of the study were Rice graduate students Zheng Yan, Jun Yao and Elvira Beitler and postdoctoral research associate Yu Zhu.
The Air Force Office of Scientific Research and the Office of Naval Research Multidisciplinary Research Program on graphene supported the research.
David Ruth | EurekAlert!
Astronomers release most complete ultraviolet-light survey of nearby galaxies
18.05.2018 | NASA/Goddard Space Flight Center
A quantum entanglement between two physically separated ultra-cold atomic clouds
17.05.2018 | University of the Basque Country
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology