Thursday, September 16, 2004

Three-dimensional self-assembly in nanotech?

A report in the September, 2004, issue of Nanoscience and Nanotechnology says that researchers Jagdish Narayan (Ph.D., Berkeley, 1971) and Ashutosh Tiwari used a pulsed laser to heat nickel until it turned into plasma - a form of matter with positively and negatively charged ions. 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.

"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."

There is discussion in the article of "patented" processes. One suspects there are patent applications.

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.


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