NIST questions carbon nanotube reliability

MANHASSET, NY -- National Institute of Standards and Technology researchers have found in recent reliability tests that carbon nanotubes device reliability is a major issue.

NIST test results from numerous nanotube interconnects between metal electrodes show that nanotubes can sustain extremely high current densities -- tens to hundreds of times larger than that in a typical semiconductor circuit -- for several hours but slowly degrade under constant current.

And in about 40 hours the researchers found that the metal electrodes fail when currents rise above a certain threshold.

NIST is developing measurement and test techniques and studying a variety of nanotube structures, zeroing in on what happens at the intersections of nanotubes and metals and between different nanotubes.

"The common link is that we really need to study the interfaces," said Mark Strus, a NIST postdoctoral researcher, in a statement.

The NIST paper is being presented at Nano 2011 today.

In a related study NIST researchers identified failures in carbon nanotube networks, where electrons physically hop from tube to tube. Failures in this case seemed to occur between nanotubes, the point of highest resistance, Strus said.

By monitoring the starting resistance and initial stages of material degradation, researchers could predict whether resistance would degrade gradually—allowing operational limits to be set—or in a sporadic, unpredictable way that would undermine device performance.

NIST developed electrical stress tests that link initial resistance to degradation rate, predictability of failure and total device lifetime. The test can be used to screen for proper fabrication and reliability of nanotube networks.

Strus speculates that carbon nanotube networks may ultimately be very useful for some electronic applications such as interconnects for flexible electronic displays or photovoltaics.