The single electron transistor or SET is type of switching device that uses
controlled electron tunneling to amplify current. A SET is made from two tunnel
junctions that share a common electrode. A tunnel junction consists of two
pieces of metal separated by a very thin (~1 nm) insulator. The only way for
electrons in one of the metal electrodes to travel to the other electrode is to
tunnel through the insulator. Since tunneling is a discrete process, the
electric charge that flows through the tunnel junction flows in multiples of e,
the charge of a single electron.
[Source:
Single-Electron Transistors, MITRE Nanosystems Group]
