Bypassing decades-old conventions in making computer chips, Princeton engineers developed a novel way to replace silicon with carbon on large surfaces, clearing the way for new generations of faster, more powerful cell phones, computers and other electronics.
The electronics industry has pushed the capabilities of silicon -- the material at the heart of all computer chips -- to its limit, and one intriguing replacement has been carbon, said Stephen Chou, professor of electrical engineering. A material called graphene -- a single layer of carbon atoms arranged in a honeycomb lattice -- could allow electronics to process information and produce radio transmissions 10 times better than silicon-based devices.
Until now, however, switching from silicon to carbon has not been possible because technologists believed they needed graphene material in the same form as the silicon used to make chips: a single crystal of material eight or 12-inches wide. The largest single-crystal graphene sheets made to date have been no wider than a couple millimeters, not big enough for a single chip. Chou and researchers in his lab realized that a big graphene wafer is not necessary, as long they could place small crystals of graphene only in the active areas of the chip. They developed a novel method to achieve this goal and demonstrated it by making high-performance working graphene transistors.
“Our approach is to completely abandon the classical methods that industry has been using for silicon integrated circuits,” Chou said.
Chou, along with graduate student Xiaogan Liang and materials engineer Zengli Fu, published their findings in the December 2007 issue of Nano Letters, a leading journal in the field. The research was funded in part by the Office of Naval Research.
In their new method, the researchers make a special stamp consisting of an array of tiny flat-topped pillars, each one-tenth of a millimeter wide. They press the pillars against a block of graphite (pure carbon), cutting thin carbon sheets, which stick to the pillars. The stamp is then removed, peeling away a few atomic layers of graphene. Finally, the stamp is aligned with and pressed against a larger wafer, leaving the patches of graphene precisely where transistors will be built.
The technique is like printing, Chou said. By repeating the process and using variously shaped stamps (the researchers also made strips instead of round pillars), all the active areas for transistors are covered with single crystals of graphene.
“Previously, scientists have been able to peel graphene sheets from graphite blocks, but they had no control over the size and location of the pieces when placing them on a surface,” Chou said.
One innovation that made the technique possible was to coat the stamp with a special material that sticks to carbon when it is cold and releases when it is warm, allowing the same stamp to pick up and release the graphene.
Chou’s lab took the next step and built transistors -- tiny on-off switches -- on their printed graphene crystals. Their transistors displayed high performance; they were more than 10 times faster than silicon transistors in moving "electronic holes" -- a key measure of speed.
The new technology could find almost immediate use in radio electronics, such as cell phones and other wireless devices that require high power output, Chou said. Depending on the level of interest from industry, the technique could be applied to wireless communication devices within a few years, Chou predicted.
“What we have done is shown that this approach is possible; the next step is to scale it up,” Chou said.
Steven Schultz | EurekAlert!
Researchers pave the way for ionotronic nanodevices
23.02.2017 | Aalto University
Microhotplates for a smart gas sensor
22.02.2017 | Toyohashi University of Technology
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
24.02.2017 | Life Sciences
24.02.2017 | Life Sciences
24.02.2017 | Trade Fair News