While there are many announcements about breakthroughs in the synthesis and manipulation of carbon nanotubes and other carbon-based nanostructures, the ability to grow silicon nanomaterials gets less press. Partly that's because it's much more challenging to make them. However, French researchers have figured out how to synthesize them at much lower temperatures.
In the lab, silicon nanowires are usually created by flowing silane gas, the silicon precursor, over gold particles. The metal catalyzes the growth of silicon nanowires as long as the gas is present and, in fact, 99% of lab studies use this approach. However, there may come a time when these silicon nanowires need to be fabricated using traditional CMOS technology, in which case you can't use gold. Gold, it turns out, creates electron traps in the silicon, lessening the material's semiconductor properties.
For industry compatibility, it's better to use either aluminum or copper as the metal catalyst but that presents further problems. In this case, silicon nanowires only grow at temperatures above 450°C. But at these higher temperatures, metal interconnects and devices (such as transistors) present in traditional CMOS electronics break down. Therefore, to create silicon nanowires using methods compatible with traditional CMOS technology, the temperature at which nanowire formation is catalyzed needs to be lower.
And that's exactly what Vincent T. Renard, Michael Jublot, Patrice Gergaud, Peter Cherns, Denis Rouchon, Amal Chabli, and Vincent Jousseaume—researchers at Leti, a French research and development institute—have achieved by adopting a rather counterintuitive approach to the copper catalyst. Traditionally, the one thing you don't want to do is to oxidize your metal catalyst. As it happens, and as the team discovered, copper oxide rather than copper results in silicon nanowire formation at temperatures as low as 400°C. Their article, published in Nature Nanotechnology, describes the catalyst preparation method behind this advance.
We're still many years away from nanodevices but this development moves us an important step closer to incorporating nanomaterials and nanoscale structures into commercial CMOS devices.