Indian Americans Patent First Generation Nanostructures  
by: Francis C. Assisi

Boston, 16 September -- Copper as strong as steel. Ceramics tough enough to be used in car engines. Chips holding 10 terabits of data or five hundred times the existing storage density available today. And lighting that uses one-fifth the energy of standard fluorescent lighting and last for approximately 50 years.

All this has been the promise of Nanotechnology. But, so far, the greatest impediment to developing these advances has been creating usable nanostructures that self-assemble.

Last week, Indian American engineers at North Carolina State University crossed that threshold, receiving patents for two processes that help break that barrier.

Prof Jagdish Narayan and his young colleague Ashutosh Tiwari who together developed and patented two methods for self-assembly of three-dimensional nanostructures say that the promise of nanotechnology will become true in five years, thanks to the new technology.

The September, 2004, issue of Nanoscience and Nanotechnology gives details of this technology breakthrough, with images of the newly created structures appearing on the cover of the journal.

Dr. Jagdish "Jay" Narayan is director of the NSF Center for Advanced Materials and Smart Structures at NCSU, and Dr. Ashutosh Tiwari, is Research Associate in the Department of Materials Science and Engineering.

It is worth noting that Tiwari, an expert in Photolithography and thin film preparation using Pulsed Laser Deposition, received all his education in India, including his Ph.D. (2000) from IIT Kanpur. In the case of Narayan, after receiving his B.Tech (1969) in metallurgy from IIT, he went on to receive his M.S. (1970) and Ph.D. (1971) from UC Berkeley.

Narayan is internationally known for his seminal contributions in laser processing of materials including laser annealing and pulsed laser deposition, atomic-scale characterization, and atomistic modeling of dislocations and interfaces.

The scientists report that the new methods are a breakthrough in nanotechnology that opens the door to creating new materials for a myriad of applications, including super-dense data storage, solid-state lighting, super-strong materials and advanced detection systems.

According to Narayan, three-dimensional self-assembly is the key to being able to use the nanostructures.

Their report says that the researchers used a pulsed laser to heat nickel until it turned into plasma - an amorphous form of matter with positively and negatively charged atoms. In this form, the nickel rearranged itself on two different substrates - aluminum oxide and tin titanium nitrate - as uniform dots.

The dots arranged themselves at a density that would, theoretically, allow about five terabytes of data - five thousand gigabytes - to be packed into computer drive roughly the size of postage stamp. "Now the aim should be to integrate these handouts with silicon chips," Narayan told New Scientist.

Perhaps the breakthrough by the two Indian-Americans is the latest example of a general objective of United States´ National Nanotechnology Initiative (NNI) – the systematic control of the nanoscale in order to obtain new properties and functions

Other scientists note that this is part of the first generation of passive nanostructures that illustrate how one might exploit new phenomena and behavior of materials at the nanoscale for economic advantage.

“The grand challenge is to be able to use the nanounit in the form of nanodot or nanowire,” said Narayan, who is also the John C. C. Fan Family Distinguished Chair in Materials Science at NCSU. “In the past we could make only one layer of the nanostructure with these units. There was only two-dimensional self-assembly, which is not usable for applications. We couldn’t control the properties of the medium. Now, with this development, we can control the medium and do three-dimensional self-organization. More importantly, we can change the size in different layers and change the functionality at different depths.”

He further explained, "Controlled processing and self-assembly in three dimensions is required because you cannot create these structures and then assemble them. They are too small. So to be able to use this technology, you must have self-assembly and it must be 3-D," he elaborates.

According to Narayan, the research provides the basic framework for nanostructured materials for information storage, spin transistors, single-electron transistors and hybrid devices, super hard coatings, and novel biomaterials.

"In the 6-10 nm dots created so far, we have the ability to control the spin patterns – the spin is what stores the bit of information. Assuming a 7nm magnetic nanodot will store one bit of information, we can achieve over 10 trillion bits per square inch, which is close to 500 times the existing storage density,” he said. Mihail C. Roco, Senior Advisor for Nanotechnology, NSF, commented: "Narayan has used the basic concepts of self-assembly to create a 3-D array of nanodots which may have significant applications in lighting, lasers, spintronics, and optical devices. If developed for practical applications in the next 2-3 years, the nanodot lighting systems may have significant environmental, economic and energy-saving advantages."

According to Narayan and Tiwari, the patented processes can be applied to almost any material. To create nanostructures for the different applications, the material used for the nanodots and the matrix are changed. For example, to create structures for data storage, Narayan uses nickel; for solid-state applications, gallium nitride or zinc oxide is used; for superstrong materials, copper, tungsten carbide and nickel aluminide are used; and for ceramics, aluminum oxide is used.

The most interesting application may be the development of energy-efficient, low-cost, solid-state lighting. By creating a matrix of layers of varying sizes of nanodots embedded in a transparent medium such as aluminum oxide, Narayan can create a chip that glows with white light. Solid-state lighting would use about one-fifth the energy of standard fluorescent lighting and last for approximately 50 years.

Another interesting application for the nanodots is the development of a chip that can hold 10 terabits of information - information that equals 10 million million or 10 to the 13th power bits - which is equivalent to 250 million pages of information. Narayan estimates that a chip with this storage capacity represents an increase of more than two orders of magnitude, or five hundred times the existing storage density available today.

According to Narayan, the key to moving nanotechnology from the laboratory to the consumer is keeping the cost of manufacturing low because people will not embrace a new technology if the cost is substantial. He believes that the beauty of these new patented processes is that they make it possible to build a three-dimensional matrix of nanodots that is not only more efficient but also costs less to produce. Using Narayan’s methods, all of the steps can be performed in the same processing chamber, reducing the manufacturing cost and the impact on the environment. With further development of these new processes, copper can be created that is as strong as steel, and ceramics can be made tough enough to be used in automobile engines.

Scientists note that the major difficulty with most materials is the problem of defects. However, when materials are reduced in size to nanoscale, the defects are reduced or eliminated, creating stronger materials that would last much longer and be less likely to fail.

For example, ceramics are excellent performers at high temperatures but are currently too brittle to be used in automobile engines. Applying nanotechnology would create a ceramic material that would be able to withstand the stress that affects an automobile engine. Because ceramics perform at higher temperatures, a ceramic automobile engine could run at a higher temperature and thus run more efficiently - essentially creating a more fuel-efficient vehicle.

Narayan anticipates that the first applications of his nanodots will be available to consumers within the next five years. He predicts that data storage and solid-state lighting will be the most likely consumer applications to be developed during that time.

However, others remain more cautious about the potential of the technique. "It sounds very promising," says Mark Welland, directory of Nanoscale at Cambridge University in the UK. "But there´s a big difference between having 5 nanometer dots and having them in the right structure on a surface that can be used as memory."

Welland says any new memory technology will struggle if it means completely rethinking the way computer memory already works. "Whichever technology can be most easily assimilated will win," he says. Narayan concedes that several problems still need to be overcome. For example, he says, it is important to find an alternative to nickel, as this has to be cooled in order to work effectively as a magnetic memory. But he remains confident that the method has potential.

The researchers are working with Kopin Corporation, which has licensed the patents from NCSU to manufacture next-generation, high-efficiency light-emitting diodes for economical solid-state lighting. Kopin Corporation, in collaboration with the NCSU researchers, has developed high-efficiency LED, known as Kopin’s CyberLite LED, which recently won Electronic Products Magazine’s “Product of the Year” award.

francisassisi@hotmail.com


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