Bell Labs, where the transistor was invented in 1947, has now announced what it believes to be the smallest transistor possible. At around one billionth of a metre across -- the length of a single molecule -- the device uses organic materials and assembles itself from a chemical solution. This is effectively the smallest that a transistor can be, says Bell Labs, and thus marks the end for the smaller, faster, cheaper path that has driven the semiconductor industry for forty years. "It literally happens in a beaker on a desktop using a procedure known as chemical self-assembly. This is the ultimate in small. It's the end of Moore's Law scaling," said John Rogers, director of nanotechnology research. Moore's Law states that the number of transistors per integrated circuit will double every 18 months, and has held true since 1965.
The transistor is made from gold electrodes, a silicon dioxide layer and thiol molecules, which are carbon compounds similar to alcohols but with the oxygen replaced by sulphur. They are constructed by pouring the solution over the electrodes, whereupon the thiols align themselves and make the transistor structure. The devices can be configured as switches, amplifiers and simple logic circuits, and are potentially much cheaper to make than existing solid state semiconductors.
First applications are likely to be in devices like active paper displays and laptop screens, where the transistor's plastic-like composition means it can flex and fold where silicon would shatter. However, it is expected that it will take around 30 years for the rest of the industry to catch up with devices of this size, during which time Moore's Law will continue to apply.
"The devices have around a thousand active molecules" said Hendrick Schon, a researcher at the labs. "We need to see whether we can do amplification and switching with single molecules, to see where the ultimate limit is in making transistors. "
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