Credit: © 2007 ACS

Carbon nanotubes show great potential for electrical sensors and the miniaturization of computing. Now Adrian Bachfold and co-workers1 at Universitat Autònoma de Barcelona have used a carbon nanotube to build a transistor that detects single electrons — one of the ultimate goals of nanoscale electronics.

The new device consists of a single-walled nanotube with its ends in contact with two electrodes. A gold nanoparticle that is 30 nm in diameter was placed on top of the nanotube using an atomic force microscope and the researchers closely monitored the nanotube conductance, which is very sensitive to the presence of electric charges. When the circuit voltage was increased, the conductance dropped — typical behaviour for semiconducting nanotubes. However, several small fluctuations in conductance were also observed, caused by single electrons jumping from the nanotube to the gold nanoparticle.

The junction between the nanotube and the nanoparticle provides a resistance six orders of magnitude higher than can be achieved in conventional electronics. Furthermore, the transistor circuit is much smaller than previous single-electron detectors, has more practical operating temperatures and could be used for studying highly resistive organic molecules and semiconducting particles.