A key discovery at Rensselaer Polytechnic Institute could help advance the role of graphene as a possible heir to copper and silicon in nanoelectronics.
Graphene, a one-atom-thick sheet of carbon, eluded scientists for years but was finally made in the laboratory in 2004 with the help of everyday, store-bought clear adhesive tape. Graphite, the common material used in most pencils, is made up of countless layers of graphene. Researchers simply used the gentle stickiness of tape to break apart these layers.
Saroj Nayak, an associate professor in Rensselaer’s Department of Physics, Applied Physics and Astronomy, has worked with graduate student Philip Shemella and others for two years to determine how graphene’s extremely efficient conductive properties can be exploited for use in nanoelectronics. After running dozens of robust computer simulations, the group has demonstrated for the first time that the length, as well as the width, of graphene directly impacts the material’s conduction properties.
Nayak, Shemella, and their team outlined their findings in the report “Energy Gaps in Zero-Dimensional Graphene Nanoribbons” published in the July 23 issue of Applied Physics Letters.
In the form of a long 1-D nanoscale ribbon, which looks like molecular chicken wire, graphene demonstrates unique electrical properties that include either metallic or semiconducting behavior. When short segments of this ribbon are isolated into tiny zero-dimensional (0-D) segments called “nanorectangles,” where the width is measured in atoms, they are classified as either “armchair” or “zigzag” graphene nanoribbons. Both types of nanorectangles have unique and fascinating properties.
Nayak, Shemella and the group took 1-D nanoribbons and trimmed the length down to a few nanometers, so the length was only a few times greater than the width. The lengths of the resulting zero-dimensional graphene nanorectangles had clear and distinct effects on the material’s properties.
The team used quantum mechanical simulations with predictive capability to carry out this work. Their computational study showed for the first time that the length of graphene may be used to manipulate and tune the material’s energy gap. This is important because energy gaps determine if the graphene is metallic or semiconducting.
Generally, when graphene is synthesized, there is a mix of metallic and semiconductor materials. But Nayak’s findings give researchers a blueprint that should allow them to purposefully make entire batches of either one or the other.
This research is an important first step, Nayak and Shemella said, for developing a way to mass produce metallic graphene that could one day replace copper as the primary interconnect material on nearly all computer chips.
The size of computer chips has shrunk dramatically over the past decade, but has recently hit a bottleneck, Nayak said. As copper interconnects get smaller, the copper’s resistance increases and its ability to conduct electricity degrades. This means fewer electrons are able to pass through the copper successfully, and any lingering electrons are expressed as heat. This heat can have negative effects on both a computer chip’s speed and performance.
Researchers in both industry and academia are looking for alternative materials to replace copper as interconnects. Graphene could be a possible successor to copper, Nayak said, because of metallic graphene’s excellent conductivity. Even at room temperature, electrons pass effortlessly, near the speed of light and with little resistance, through metallic graphene. This would almost ensure a graphene interconnect would stay much cooler than a copper interconnect of the same size.
It will likely be years before a graphene interconnect is realized, but major computer companies including IBM and Intel have taken notice of the material. Nayak said graphene is also currently a “hot topic” in academia.
Carbon nanotubes, which are essentially made of rolled-up graphene, are another potential heir to replace copper as the primary material used for interconnects. But they suffer from setbacks similar to those of graphene, Nayak said. When single-walled carbon nanotubes are synthesized, about one-third of the batch is metallic and the remaining two-thirds are semiconductors. It would be extremely difficult to separate the two on a mass scale, Nayak said. On the contrary, recent research at Rensselaer and elsewhere shows graphene could be produced in a more controlled way.
“Fundamentally, at this point, graphene shows much potential for use in interconnects as well as transistors,” Nayak said.
It is also possible that semiconductor graphene could one day be used in place of silicon as the primary semiconductor used in all computer chips, but research into this possibility is still extremely preliminary, Nayak said.
Michael Mullaney | EurekAlert!
'Frequency combs' ID chemicals within the mid-infrared spectral region
16.03.2018 | American Institute of Physics
Fraunhofer HHI have developed a novel single-polarization Kramers-Kronig receiver scheme
16.03.2018 | Fraunhofer-Institut für Nachrichtentechnik, Heinrich-Hertz-Institut, HHI
Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...
On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...
The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...
At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.
When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...
At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.
Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...
16.03.2018 | Event News
13.03.2018 | Event News
08.03.2018 | Event News
16.03.2018 | Earth Sciences
16.03.2018 | Physics and Astronomy
16.03.2018 | Life Sciences