Researchers at Manchester University in the UK have made the first transistors from graphene quantum dots, suggesting that graphene is a promising replacement for silicon in the next-generation of electronic devices.
Graphene is a two-dimensional sheet of carbon just one atom thick, and is usually made by cleaving small crystals of graphite. At a molecular level it looks like a sheet of chicken wire — a continuous spread of joined-up benzene rings.
Because of its unusual physical properties, graphene is often touted to replace silicon as the electronic material of choice. These include the fact that electrons in the material behave like relativistic particles, which have no rest mass and can therefore travel at speeds of around 106 m/s. “The good thing is that these properties remain when we scale graphene devices down to a few benzene rings, which is what one needs for top-down molecular electronics,” team member Kostya Novoselov told physicsworld.com.
Until now, researchers have only been able to make transistors from ribbons of graphene. But such a long shape does not maximize the conductivity, which is why Novoselov and colleagues cut the ribbons back into sizes that can quantum confine electrons. They do this using a combination of electron beam lithography and reactive plasma etching to carve small islands out of large graphene sheets (Science 320 356). “We have demonstrated a proof of concept — that it is possible to create a transistor based on graphene quantum dots by standard technological procedures,” says Novoselov. “Furthermore, the device will be able to operate at room temperature.”
Andre Geim, another member of the team, says they can now make reproducible transistors with features as small as 10 nm, which should reduce to 1 nm in the future. “It is molecular electronics using the top-down approach. No other material allows this approach for making structures smaller than 100 nm, which is the dimension needed for operating single-electron transistors at room temperature.”
Jie Chen of the University of Alberta in Canada, whose team also works on making electronic devices from graphene, is impressed at how quickly Novoselov, Geim and colleagues are making developments with graphene. “They are the global leaders in this field,” he says.
