Growing Silicon Nanowires Where You Want Them

By Roland Piquepaille

A research group led by Raj Solanki, professor of electrical engineering in OHSU's OGI School of Science & Engineering, recently demonstrated it is possible to grow silicon nanowires exactly where you want them on an electrode using electrical fields. Solanki's team also can grow silicon-based nanowires in the exact direction necessary to fabricate electronic devices.

Here is a photo of such silicon nanowires (Credit: OHSU).

The researchers now are exploring electrical properties of the silicon nanowires. "Now that we know we can grow silicon nanowires in a precise location and in a specific direction, we want to know what happens to the nanowire when it contacts the metal on the electrode," said Solanki. "We also are studying how any kind of coating or contamination on the nanowire surface affects the passage of charges through it."

As Moore's law cannot continue to be verified for ever, the traditional electrical engineering methods to build transistors need to be complemented.

"A completely new approach needs to be developed to go beyond the current limit," noted Solanki. "One possible solution is to develop electronic devices that incorporate silicon nanowires or carbon nanotubes as active components operating under physics laws of quantum mechanics."

"Growing silicon nanowires in a specific location in whatever direction you desire, which we have done, is much more practical for gigascale integration -- putting a billion transistors on a chip -- in the long term," said Solanki.

How does this new approach work? It's surprisingly easy.

Solanki grows his silicon nanowires in a quartz reactor using a technique developed decades ago by Bell Labs called vapor-liquid-solid deposition. "The addition of the electrical fields is what's new," said Solanki. "We have also grown nickel silicide conducting nanowires, which will be useful for contacting the silicon semiconductor nanowires."

And what's next?

Besides growing ultra-thin films for fabricating nanowire devices, Solanki and his team at OGI (John Freeouf and John Carruthers) recently have demonstrated that atomic layer deposition can be used to grow semiconductor heterostructure nanowires consisting of very thin alternating layers of two materials, which has potential for optoelectronics applications.

Source: Oregon Health & Science University news release, via EurekAlert!, February 22, 2004