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Nanoscale Au layers to allow
Posted: 20 Sep 2011 ?? ?Print Version ?Bookmark and Share

Keywords:gold nanoparticle? superlattice? IC manufacturing?

A team of researchers at Rensselaer Polytechnic Institute have come up with a novel technique to create a layer of self-assembling gold nanoparticles in the scale of nanometers that could advance IC manufacturing.

Sang-Kee Eah, assistant professor at Rensselaer, showed how the gold nanoparticles combine into a superlattice. He observed a superlattice measuring 20?mwith a distance between lines of nanoparticles, or lattice constant, of 8.8nmthat he said is the largest ever documented. He added that this method could lead to even larger superlattices with even tinier features. "Thinking about semiconductors, this discovery could offer new solutions for scaling down the features of today's most advanced 32nm computer chips to have features in the range of less than 20nm, or even less than 10nm," Eah stated. He used scanning electron microscopy, with Moire interference patterns, to measure the boundaries of the superlattice.

Gold nanoparticle layers

Eah infused liquid toluene with gold nanoparticles. The nanoparticles form a flat, closely packed layer of gold on the surface of the liquid where it meets air. By putting a droplet of the gold-infused liquid on a surface, and waiting for the toluene to evaporate, the researchers were able to coat many different surfaces, including a three-inch silicon wafer, with a monolayer of gold nanoparticles.

"There has been tremendous progress in recent years in the chemical syntheses of colloidal nanoparticles. However, fabricating a monolayer film of nanoparticles that is spatially uniform at all length scalesfrom nanometers to millimetersstill proves to be quite a challenge," Eah noted.

Whereas other synthesis methods take several hours, this new method chemically synthesizes gold nanoparticles in only 10min without the need for any post-synthesis cleaning. In addition, gold nanoparticles created this way have the special property of being charged on non-polar solvents for 2D self-assembly, he added.

Previously, the 2D self-assembly of gold nanoparticles in a toluene droplet was reported with excess ligands that slows down and complicates the process. This required the non-volatile excess ligands to be removed in a vacuum. In contrast, Eah's new method ensures that gold nanoparticles float to the surface of the toluene drop in less than one second without the need for a vacuum. It then takes only a few minutes for the toluene droplet to evaporate and leave behind the gold monolayer.

James I. Basham, a graduate student at Pennsylvania State University, and Paul Chando, an incoming graduate student at the City College of New York, are co-authors of the paper.

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