Bye bye silicon
SILICON is quintessential to microelectronics. Since the first transistor, silicon has been the element of choice in the manufacture and fabrication of the chips which form the heart of all microelectronics. But now, Sander 1 Tans and his collaborators at the Delft Institute of Technology, the Netherlands, have reported the fabrication of a transistor made from a single large molecule of carbon. If the promise holds out, then carbon may well replace silicon as microelectronics1 element of the next millennium (Nature, Vol 393, No 6680).
It was in the mid-1970s that the use of single molecules was first proposed as electronic devices. The field never really took off due to technological difficulties in making electrical contact with single molecules. But recently, with the development of nanotechnology and the need for greater miniaturisation, the field has got a fresh impetus.
The key advance was the realisation that one can make tubes by rolling graphite sheets. These tubes can be both metallic or semiconducting, depending on the structural details. The use of metallic tubes for single electron transistors was reported last year, but it is for the first time that semiconducting tubes have been used for devices.
Using a silicon substrate, a single wall nanotube was attached to three platinum electrodes. This created a field effect transistor, comprising the single carbon nanotube and two metallic electrodes. Various studies carried out on the device confirmed its operation as a transistor with the desired characteristics. This is obviously the first step in developing carbon-based devices.
One expects to see diodes and other devices based on carbon nanotubes soon. Given their miniature size and properties, these devices would be much faster than conventional silicon devices. If the fabrication and doping techniques of carbon nanotubes develop adequately, there may well be a revolution in the field of microelectronics in the next century.
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