Korean researchers grow 4-inch diameter, high-quality, multi-layer graphene on desired silicon substrates, an important step for harnessing graphene in commercial silicon microelectronics
In the last decade, graphene has been intensively studied for its unique optical, mechanical, electrical and structural properties. The one-atom-thick carbon sheets could revolutionize the way electronic devices are manufactured and lead to faster transistors, cheaper solar cells, new types of sensors and more efficient bioelectric sensory devices.
As a potential contact electrode and interconnection material, wafer-scale graphene could be an essential component in microelectronic circuits, but most graphene fabrication methods are not compatible with silicon microelectronics, thus blocking graphene's leap from potential wonder material to actual profit-maker.
Now researchers from Korea University, in Seoul, have developed an easy and microelectronics-compatible method to grow graphene and have successfully synthesized wafer-scale (four inches in diameter), high-quality, multi-layer graphene on silicon substrates. The method is based on an ion implantation technique, a process in which ions are accelerated under an electrical field and smashed into a semiconductor. The impacting ions change the physical, chemical or electrical properties of the semiconductor.
In a paper published this week in the journal Applied Physics Letters, from AIP Publishing, the researchers describe their work, which takes graphene a step closer to commercial applications in silicon microelectronics.
"For integrating graphene into advanced silicon microelectronics, large-area graphene free of wrinkles, tears and residues must be deposited on silicon wafers at low temperatures, which cannot be achieved with conventional graphene synthesis techniques as they often require high temperatures," said Jihyun Kim, the team leader and a professor in the Department of Chemical and Biological Engineering at Korea University. "Our work shows that the carbon ion implantation technique has great potential for the direct synthesis of wafer-scale graphene for integrated circuit technologies."
Discovered just over a decade ago, graphene is now considered the thinnest, lightest and strongest material in the world. Graphene is completely flexible and transparent while being inexpensive and non-toxic, and it can conduct electricity as well as copper, carrying electrons with almost no resistance even at room temperature, a property known as ballistic transport. Graphene's unique optical, mechanical and electrical properties have lead to the one-atom-thick form of carbon being heralded as the next generation material for faster, smaller, cheaper and less power-hungry electronics.
"In silicon microelectronics, graphene is a potential contact electrode and an interconnection material linking semiconductor devices to form the desired electrical circuits," said Kim. "This renders high processing temperature undesirable, as temperature-induced damage, strains, metal spiking and unintentional diffusion of dopants may occur."
Thus, although the conventional graphene fabrication method of chemical vapor deposition is widely used for the large-area synthesis of graphene on copper and nickel films, the method is not suited for silicon microelectronics, as chemical vapor deposition would require a high growth temperature above 1,000 degrees Celsius and a subsequent transfer process of the graphene from the metallic film to the silicon.
"The transferred graphene on the target substrate often contains cracks, wrinkles and contaminants," said Kim. "Thus, we are motivated to develop a transfer-free method to directly synthesize high quality, multilayer graphene in silicon microelectronics."
Kim's method relies on ion implantation, a microelectronics-compatible technique normally used to introduce impurities into semiconductors. In the process, carbon ions were accelerated under an electrical field and bombarded onto a layered surface made of nickel, silicon dioxide and silicon at the temperature of 500 degrees Celsius. The nickel layer, with high carbon solubility, is used as a catalyst for graphene synthesis. The process is then followed by high temperature activation annealing (about 600 to 900 degrees Celsius) to form a honeycomb lattice of carbon atoms, a typical microscopic structure of graphene.
Kim explained that the activation annealing temperature could be lowered by performing the ion implantation at an elevated temperature. Kim and his colleagues then systematically studied the effects of the annealing conditions on the synthesis of high-quality, multi-layer graphene by varying the ambient pressure, ambient gas, temperature and time during the treatment.
According to Kim, the ion implantation technique also offers finer control on the final structure of the product than other fabrication methods, as the graphene layer thickness can be precisely determined by controlling the dose of carbon ion implantation.
"Our synthesis method is controllable and scalable, allowing us to obtain graphene as large as the size of the silicon wafer [over 300 millimeters in diameter]," Kim said.
The researchers' next step is to further lower the temperature in the synthesis process and to control the thickness of the graphene for manufacturing production.
The article, "Wafer-scale synthesis of multi-layer graphene by high-temperature carbon ion implantation," is authored by Janghyuk Kim, Geonyeop Lee and Jihyun Kim. It will be published in the journal Applied Physics Letters on July 21, 2015 (DOI: 10.1063/1.4926605). After that date, it can be accessed at: http://scitation.
ABOUT THE JOURNAL
Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology. See: http://apl.
Jason Socrates Bardi | EurekAlert!
NASA's James Webb Space Telescope completes final cryogenic testing
21.11.2017 | NASA/Goddard Space Flight Center
Previous evidence of water on mars now identified as grainflows
21.11.2017 | US Geological Survey
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
21.11.2017 | Physics and Astronomy
21.11.2017 | Physics and Astronomy
21.11.2017 | Life Sciences