Nanowire Transistors Faster than Silicon

Advances in nanowires show they can be fast enough to use as ultrasmall transistors in cheap, high-performance electronics.

Researchers at Harvard University have shown that nanowire transistors can be at least four times speedier than conventional silicon devices. The principal researcher, chemistry professor Charles Lieber, says this could lead to inexpensive, high-performance, flexible electronic circuitry for cell phones and displays. It could also save space and further increase speed, he says, by allowing memory, logic, and sensing layers to be assembled on the same chip.

Nanowires have been considered a promising contender for use on future logic chips because of their very small size (about 10 nanometers wide) and because they can be made without complicated lithography, says Peidong Yang, professor of chemistry at University California, Berkeley. Until now, though, the performance of nanowire-based transistors has lagged far behind that of other potential nano devices, such as carbon nanotubes, and even conventional devices. But the new Harvard research suggests that nanowires have surpassed conventional transistors and nearly caught up with nanotubes.

This may give nanowires an edge over carbon nanotubes (see "Carbon Nanotube Computers"). Nanowires are made with regular crystal structures and uniform electronic properties -- a level of predictability essential for manufacturing high-performance electronics. Nanotubes, however, come in batches of different sizes and structures, each of which can perform very differently -- so until a good sorting method can be found, it will be difficult to use nanotubes in high-end processors.

The first applications for nanowires will likely be ultra-sensitive sensors for single molecule detection (when molecules bind to the nanowires they create a detectable change in the current flowing through the wires). Such applications could be ready in two to three years, Lieber says (see "Drugstore Cancer Tests").

Nanowire transistors may never replace more conventional devices in computer chips used in laptops and personal computers -- the cost of developing large-scale manufacturing would probably not be justified by a 4 to 5 times improvement in performance, Lieber says. But, he adds, the new performance figures suggest it will be well worth scaling up the technology to manufacture them for applications where the ability to assemble nanowire transistors at room temperature on various surfaces, including plastic, will bring an added advantage. For instance, in flexible displays nanowire transistors could be used to embed information-processing in the screen itself.