Microelectronics | Growing up | Economist.com

Microelectronics | Growing up | Economist.com

Long, thin transistors made of silicon nanowires may be the next contribution to electronic miniaturisation

THE race in computing is a race to the bottom. The need is always to cram more components on to less “real estate”. And, like real-estate developers in the more familiar world of human cities, there comes a point where “up” seems like a good alternative to urban sprawl.

That is the thinking behind making transistors out of nanowires. The wires in question—strands of silicon—are but a few tens of nanometres thick. Though they make up for that in height (they are 2,000 nanometres tall). Their slight diameters mean that zillions of them could be crowded on to a single chip.

Those diameters are, indeed, so slight that the wires are essentially one-dimensional. That gives them interesting properties. It is much easier for electrons to pass through them than through three-dimensional wires, for two reasons. One is that there is less leeway for the electrons to scatter simply because there is less room for them to manoeuvre. The second is that the atomic surface of nanowires tends to be smoother than that of regular wires because the former are perfect crystals. That also reduces scattering

Walter Riess, a physicist at IBM’s Zurich Research Laboratory, in Switzerland, and his colleagues wanted to exploit these features to make better transistors. A transistor is, at bottom, just a switch that allows or prohibits the passage of one electric current according to instructions carried by a second current. What Dr Riess’s team has done is to make silicon nanowires switch on and off like a transistor.