Tailoring carbon nanotubes

Tom Yuzvinsky

Shrinking Carbon Nanotubes

The mechanical and electrical characteristics of carbon nanotubes depend strongly upon their diameter, with important consequences for nanotube-based devices.

Unfortunately, current nanotube growth techniques cannot reliably control nanotube dimensions, necessitating the development of a post-synthesis method for diameter selection.

To smoothly shrink carbon nanotubes while maintaining their high quality graphitic structure, we combine TEM electron beam damage with a very high temperature annealing process.

The very high temperature (in excess of 1000°C) is achieved by in situ Joule heating: electrical current is passed through the nanotube by means of metal contacts deposited on an electron transparent membrane. This device structure allows for simultaneous shrinking and high resolution imaging of the nanotubes.

By adjusting the bias applied across the nanotube we are able to precisely control the shrinking process.

Increasing the bias raises the temperature of the nanotube and allows it to reform. Lowering the bias results in a temperature drop and locks in the current diameter.

Our results demonstrate that the high-bias conductance of a multiwalled nanotube is determined strictly by its geometry, with resistance inversely proportional to cross-sectional area. This measurement confirms the "lathe model" introduced in our studies of electrical breakdown in multiwalled nanotubes.

See also:

"Shrinking a Carbon Nanotube"
TD Yuzvinsky, W Mickelson, S Aloni, GE Begtrup, A Kis and A Zettl
Nano Letters 6, 2718-2722 (2006)
Featured in: "Nanotechnology: Shrink to fit" Nature, 444 247 (2006)
"Nanotubes get that shrinking feeling" Nature Materials, 16 November 2006
"Nanotubes Grow Smaller than a Nanometer" Scientific American, 14 November 2006
"How to Shrink a Carbon Nanotube" PhysOrg.com, 30 November 2006
"Nanotube with made-to-order diameter" Materials Today, 10 (1-2) 13 (2007)

"Probing nanoscale solids at thermal extremes"
GE Begtrup, KG Ray, BM Kessler, TD Yuzvinsky, H Garcia, and A Zettl
Physical Review Letters 99, 155901 (2007) PDF

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