Self-assembling 3D Nanostructures

By Roland Piquepaille

Chips holding 10 terabits of data? Copper as strong as steel? Ceramics tough enough to be used in car engines? All this will be true in five years, thanks to two new methods to create self-assembling 3D nanostructures. These methods used pulsed laser deposition to create layers of nanodots organized in a matrix. These arrays of nanodots are consistent in shape and size -- 7 nanometers with nickel for example. But the real beauty of these methods is that they can be applied to almost any material, like nickel for data storage or aluminum oxide for ceramics. These methods also reduce drastically imperfections, leading to future superstrong materials. Read more...

Here is how the article from the Triangle Tech Journal, North Carolina

Dr. Jagdish "Jay" Narayan, the John C.C. Fan Family Distinguished Professor of Materials Science and Engineering and director of the NSF Center for Advanced Materials and Smart Structures at NC State (CAMSS), and Dr. Ashutosh Tiwari, research associate in the Department of Materials Science and Engineering, developed and patented two methods for self-assembly of three-dimensional nanostructures.

The two methods involve using pulsed laser deposition, which works with a variety of materials and reduces imperfections. The sequential growth method uses the laser pulses to ablate successive targets to create layers of nanodots in a matrix. The simultaneous growth method is based on the difference in the oxidation rate of the nanodot and matrix materials. In this method the matrix and nanodots are deposited simultaneously on a substrate. Both methods produce consistent size and shape of the nanodots and demonstrate control of the materials that cannot be achieved by previously proposed methods.

With these methods, the researchers have for example produced nanodots using nickel. Each nanodot measures only 7 nanometers in diameter.

Here is a "high-resolution image from a scanning transmission electron microscope showing a single nickel nanocrystal, a nanodot. Each 'bump' is an individual nickel atom." (Credit: Jagdish Narayan and Ashutosh Tiwari, North Carolina State University/NSF Center for Advanced Materials and Smart Structures.)

But these methods work with a great variety of materials, not only nickel.

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.

What kind of applications can we expect from this breakthrough in nanotechnology? Here are just three examples.

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.

[And] 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. 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.

When will we see these new applications?

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.

For more information, you also can read this press release from the National Science Foundation (NSF), "Not-So-Spotty Material Breakthrough," in which I found the above illustration.

Here is a quote from Mihail C. Roco, Senior Advisor for Nanotechnology at the NSF.

"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."

The research work will be published by the Journal of Nanoscience and Nanotechnology in its September 2004 issue. However, the last issue available online is from April 2004, so I can't provide you with a link to the paper.

Sources: Triangle Tech Journal, North Carolina, September 2, 2004; National Science Foundation press release, August 31, 2004