April 6, 2009 Since its discovery in 2004 graphene has promised some truly astounding developments in the realm of computer technology. We’ve previously looked at how graphene could provide the means to keep pace with Moore’s Law. Now engineers at Ohio State University are developing a technique for mass-producing computer chips made from graphene that meshes with standard chip-making practices.
Graphene is a one-atom-thick gauze of carbon atoms resembling chicken wire made from the same material found in pencils. It has been dubbed the ‘new silicon’ as experts believe it holds the key to smaller, faster electronics and might also deliver quantum mechanical effects that could enable new kinds of electronics. Until now, most researchers could only create tiny graphene devices one at a time, and only on traditional silicon oxide substrates. They couldn't control where they placed the devices on the substrate, and had to connect them to other electronics one at a time for testing. Now College of Engineering Distinguished Professor in Materials Science and Engineering, Nitin Padture and his colleagues believe they have come up with a technique for stamping many graphene sheets onto a substrate at once, in precise locations.
Researchers have shown that a single sheet of graphene, which measure just a few tenths of a nanometer, or even a few sheets, can exhibit special properties. One such property is very high mobility, in which electrons can pass through it very quickly - a good characteristic for fast electronics. Another is magnetism, which would enable magnetic fields to be used to control the spin of graphene electrons, which would enable spin-based electronics, also called spintronics. Graphene's properties also change dramatically when it touches other materials making it a good candidate material for chemical sensors.
In their method, Padture and his Ohio State colleagues carved graphite into different shapes, such as a field of microscopic pillars, and then stamped the shapes onto silicon oxide surfaces. If you think of a stack of graphene sheets in graphite as a deck of cards then bringing it contact with the silicon oxide and pulling it away allows the 'splitting of the deck' near the point of contact, leaving some layers of graphene behind. Through computer simulations the team found that the graphene surface interacts so strongly with the silicon oxide surface that the chemical bonds between the graphene layers weaken, and the lower layers split off.
In this first series of experiments, the Ohio State researchers were able to stamp high-definition features that were ten layers thick, or thicker. The graphite stamp can then be used repeatedly on other predetermined locations on the same or other substrates, potentially making this a mass-production method. They eventually hope to stamp narrow features that are only one or two layers thick, by stamping on materials other than silicon oxide. Computer simulations also showed that each material interacts differently with the graphene. So success might rely on finding just the right combination of substrate materials to coax the graphene to break off in one or two layers, which would also tailor the properties of the graphene.
So the breakthrough could see the next generation of computer chips made from the same material used in pencils – just be sure to be careful with those erasers.
The team’s paper can be found in the March 26 issue of the journal Advanced Materials.
Darren Quick
