Carbon nanotubes set for electronic applications

High-quality carbon nanotubes have been grown at significantly lower temperatures than previously achieved, paving the way for their use in electronics.

The finding is good news for all commercial applications of carbon nanotubes, which are currently held back by substantially higher costs relative to existing materials.

The real advantage, however, lies in the production of micro electronics, where temperature is critical in the manufacturing process, as Dr Vlad Stolojan of Surrey University’s Advanced Technology Institute explained.

’When you make a semiconductor chip, such as the microprocessor in your laptop, you usually end up with several layers of different materials, including silicon, doped silicon, oxide, metal contact [and so on]. The main issue with high temperature is that all these layers will expand/contract at slightly different rates, leading to high strains such as cracking, delamination… so manufacturers have to constrain the temperature that this device reaches to below 400oC.’

The research team, which is headed by Prof Ravi Silva, showed in 2002 that nanotubes can be grown while keeping the silicon below 500oC. However, the nanotubes were defective and not any better electrical and thermal conductors than copper.

Since then the team have completely redesigned the growth process, coupling the plasma energy more efficiently to the catalyst particles, allowing them to grow carbon nanotubes of excellent quality while keeping the substrate below 350oC.

Single or multi-walled carbon nanotube structures have excellent electronic properties, with conductivity better than any other known single element material, including copper, and generate much less heat while operating – a useful feature as chip manufactures try to pack components ever more densely.

Speaking about the discovery, Prof Silva said: ’This radical and novel approach to carbon nanotube growth combines a decade of top-flight research at the ATI.

’We are currently in talks with major semiconductor manufacturers to transfer this technology to the wider market and are continuing our internationally leading research into novel contacting technologies.’