US scientists have written graphene-like conductors in an insulating substrate using an atomic force microscope.
Graphene, a flat molecular sheet resembling chicken wire, is an excellent electrical conductor and a potential fast semiconductor.
The researchers, from University of Illinois at Urbana-Champaign and Georgia Institute of Technology, used thermochemical nanolithography - heating a substrate with the tip of an atomic force microscope.
In this case, the substrate was graphene oxide, which is graphene with its free electrons mopped up by bonding with oxygen atoms - rendering it an insulator.
"We've shown that by locally heating insulating graphene oxide, both the flakes and epitaxial varieties, with an atomic force microscope tip, we can write nanowires with dimensions down to 12nm. And we can tune their electronic properties to be up to four orders of magnitude more conductive. We've seen no sign of tip wear or sample tearing," said Georgia Tech scientist Dr Elisa Riedo.
The research team tested two types of graphene oxide, one made from silicon carbide, the other with graphite powder, with the reduced graphene oxide become more conductive at 130C.
"The entire process happens in one step. You go from insulating graphene oxide to a functional electronic material by simply applying a nano-heater. We think that any type of graphene will behave this way," said
"I think there are three things about this study that make it stand out," said University of Illinois scientist Dr William King. "The writing is an extremely fast technique. These nanostructures can be synthesised at such a high rate that the approach could be very useful for engineers who want to make nanocircuits."
The research appears in the June 11, 2010, issue of the journal Science.
Artist's impression of an atomic force microscope tip selectively converting insulating graphene oxide to conducting graphene.
