Argonne Theorist Gains New Insight Into The Nature Of Nanodiamond

Argonne researcher Amanda Barnard, theorist in the Center forNanoscale Materials, is working with colleagues at two Italianuniversities who produced innovative diamond-coated nanotubes.

The diamond-coated tubes resemble a stick of rock candy,holding a layer of diamond 20 to 100 nm thick. A nanometer is onemillionth of a millimeter. The period at the end of this sentence isabout one million nanometers long. The technology in its fledglingstate has already caught the eye of the electronics industry for thepromise of ultra thin televisions with cathode ray tube-like qualitypicture at a fraction of today's current flat panel television costs.

Diamond offers an amazing array of medical and technologicalpossibilities. Wire molecules can be attached to it and diamond hassuperior light emission properties. While diamond is an insulatingmaterial, the surface is highly electronegative. A nanodiamond coatingconsists of pure surface diamond. This gives a diamond coated nanowireconductance from the nanotubes and the superior conduction from thediamond. Add to this superior light emission properties and very lowvoltage requirements, and the possibility exists for very flat, lowenergy displays.

"By using a more efficient conductor, nanotubes, with a moreefficient field emitter, in this case nanodiamonds, you get moreefficient devices," said Barnard. "A lot of groups are looking forsomething better to make electronic displays out of, and this is justanother candidate that looks very promising."

Researchers from the University La Sapienza and theUniversity Tor Vergata discovered the ability for a nanotube to grownanodiamond under certain conditions in 2004, but did not know thespecifics of how the diamond grew. To better understand the conditionsthat brought them their discovery, researchers from the group broughttheir discovery to Barnard.

Barnard, a postdoc from the Royal Melbourne Institute ofTechnology University, published her original results on the modelingof diamond nanowires in the October 2003 issue of Nano Letters. Hertheories earned her the recognition of the Italian group and she wasapproached in March of 2004 to help with calculations on theirdiscovery.

"They could make them, but they couldn't understand exactlywhat was happening or how they were forming," said Barnard. "They knewwhat it was, they could characterize it, but they didn't know how thegrowth progressed."

Barnard calculated that during the process of etching -- theterm for the degradation of nanotubes -- atomic hydrogen can change thehybridization of chemical bonds between carbon atoms of a nanotube.

"Traditionally in a hydrogen environment carbon nanotubeswould fall apart and disintegrate, but something different washappening. We actually established that if the amount of hydrogenpresent [is in correct proportion], the defects that form will nucleateinto diamond before there is a chance to etch."

These imperfections that form uniformly across the nanotube'ssurface allow for the bonding of diamond molecules, which then begin togrow the length of the tube. An added bonus property is that the end ofthe nanotube is coated with a thicker bulb of nanodiamond and uponformation the structures stand upright without manipulation.

Barnard is now on a fellowship at Oxford University, but iscontinuing to conduct research at the Center for Nanoscale Materials,now under construction. Barnard has great expectations for theopportunities the new center will open up for nanoscale research.

"I hope that the CNM will give me more opportunity to collaborate withexperimental groups," said Barnard. "I am a great advocate of doingexperimentally relevant theory, and the CNM will be a great place fordoing that."

The Center for Nanoscale Materials at Argonne is being builtwith funding from the Department of Energy Office of Science and theState of Illinois, each of which is contributing $35 million toconstruction and instrumentation of the facility.

The nation's first nationallaboratory, Argonne National Laboratory conducts basic and appliedscientific research across a wide spectrum of disciplines, ranging fromhigh-energy physics to climatology and biotechnology. Since 1990,Argonne has worked with more than 600 companies and numerous federalagencies and other organizations to help advance America's scientificleadership and prepare the nation for the future. Argonne is operatedby the University of Chicago for the U.S. Department of Energy's Officeof Science.