Ring Oscillator on Carbon Nanotube
As reported in Science magazine (”An Integrated Logic Circuit Assembled on a Single Carbon Nanotube”; 24 March 2006; Vol. 311, no. 5768, p. 1735), researchers at IBM in New York and co-workers have created a ring oscillator on a single carbon nanotube.
According to the BBC, running at 50 megahertz,
the circuit is 100,000 times faster than any previously recorded for a device made with a carbon nanotube […].
This article at the New Scientist explains how this research might help to increase the speed of future microprocessors with ever smaller feature sizes:
The problem is that as electrical paths shrink, electrical resistance increases proportionally. Also, the process of doping – adding impurities to the silicon to alter its electrical properties – means that the impurities left behind scatter electron flow, which becomes more of a problem at smaller scales.
The major reason behind the resistance, however, is an odd phenomenon known as plasmonic resonance, in which an electron’s path is hindered when it becomes coupled with vibrations in the surrounding lattice structure. But because the carbon nanotube is a single molecule with electrons passing along the tube, this problem is averted and resistance minimised, even at tiny scales.
Additionally, smaller silicon pathways make it easier for electrons to “jump tract” and leech into other nearby components. But in a nanotube circuit, this would be highly improbable as electrons would be carried down the molecular tract of the nanotube, Appenzeller explains.
