Boffins at Britain's University of Manchester have created a transistor out of an atom-thick sheet of carbon. The high-speed device is so small only one electron can pass through at once. Crucially, the transistor operates at room temperature making it potentially viable for future microprocessors.
Details of the breakthrough were announced in the science journal Nature this week. The team, led by Professor Andre Geim of the Manchester Centre for Mesoscience and Nanotechnology, built the transistor from graphene, an allotrope of carbon that essentially fits all its constituent carbon atoms into a single plane. Discovered only three years ago, graphene is highly conductive.
The transistor itself is of a type known as the single-electron transistor. The controlling gate electrode is capacitively coupled to an electrode called the island, which sits between the source and the drain. At a certain voltage the island forms what's known as a Coulomb blockade, preventing an electron in the source quantum mechanically tunneling through to the island and then through to the drain. Apply a positive voltage to the gate, and the electron is free to pass from source to island to drain.
The single-electron transistor design is not only inherently very small, but the tiny voltages required to switch it on and off make it very sensitive, to the extent that it's seen as a possible fast yet low-power successor to today's chip transistors.
The single-electron transistor isn't a new design, but past attempts to create one have used more standard semiconductor materials, all of which have needed cooling to near absolute zero to operate. The graphene single-electron transistor operates at room temperature.
There's still some way to go to create a working chip from graphene single-electron transistors. Etching the transistor isn't a certain process - most attempts produce transistors that are too large to allow just one electron to pass through, and the process makes structural changes to the graphene around the transistor that can scatter electrons, the effect of which is not yet fully understood.
However, the research may well show how chip designers may continue their work once they have exceeded the limits of silicon.