Metallic-to-semiconducting nanotube conversion greatly improves transistor performance

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Posted on May 29, 2013
When copper nanoparticles are deposited on SWNT networks (left: aligned network; right: crossbar network), the nanoparticles create band gaps in the metallic SWNTs, which decreases leakage current and improves a transistor’s on/off ratio. Credit: D. Asheghali, et al.

When copper nanoparticles are deposited on SWNT networks (left: aligned network; right: crossbar network), the nanoparticles create band gaps in the metallic SWNTs, which decreases leakage current and improves a transistor’s on/off ratio. Credit: D. Asheghali, et al.

Future transistors made of semiconducting single-walled carbon nanotubes (s-SWNTs) have the potential to perform much better than today’s transistors. However, when SWNTs are grown in bulk, only about two-thirds of them are semiconducting, while the other one-third are metallic (m-SWNTs). Since m-SWNTs have a higher conductivity than s-SWNTs, their presence allows current leakage in a transistor’s off state, which greatly decreases the transistor’s on/off current ratio and overall performance. In a new study, scientists have demonstrated that simply decorating the m-SWNTs with copper oxide nanoparticles can convert them into s-SWNTs, resulting in a 205-fold increase in a transistor’s on/off current ratio.

 

The researchers, Darya Asheghali, Pornnipa Vichchulada, and Associate Professor Marcus D. Lay at the University of Georgia in Athens, have published their paper on converting m-SWNTs to s-SWNTs in a recent issue of the Journal of the American Chemical Society.

Previous studies have attempted to overcome the problem of m-SWNTs by using methods that are often complex and expensive. Some approaches involve using specialized SWNT growth methods that select for s-SWNTs, while other approaches involve post-growth solution processing to remove m-SWNTs.

The approach proposed in the new study could provide a simpler solution to obtain large amounts of s-SWNTs. After growing the SWNTs using a conventional bulk growth method, the researchers deposited sub-10-nm copper oxide nanoparticles on all of the nanotubes, both metallic and semiconducting. This single step converts the m-SWNTs into s-SWNTs and also improves the electric properties of the original s-SWNTs.

Read more at: Phys.org