Nanotube devices in the pipeline Apr 26, 2001 The features of
conventional microelectronic circuits are getting smaller and
smaller - and they will soon reach the limit imposed by the
fundamental properties of silicon. Although physicists are
optimistic that carbon nanotubes could step into the breach,
their electronic properties are not well established and the
nanotubes are hard to manipulate. Now two teams in the US have
made substantial headway. Charles Lieber's team at Harvard
University has uncovered the electronic behaviour of several
types of nanotube. Meanwhile, Phaedon Avouris and colleagues at
IBM have devised a technique to separate metallic and
semiconducting nanotubes (Min Ouyang et al 2001 Science 292 702;
P G Collins et al 2001 Science 292 706). Carbon nanotubes are
rolled sheets of graphite just nanometres in diameter. The
electronic properties of a tube - metallic, semiconducting or a
combination of the two - depend on whether it is made from one
or many layers of graphite, and on the angle