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August 1997


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FEORC Nano-Manufacturing Processes Could Alter Semiconductors, Windshields

Blue film

With new nanomanufacturing processes, FEORC researchers are producing and analyzing films that are only microns thick. Typically, the films are tested on glass, such as the 3-inch prism above.



Work on magnetic coatings for optical fibers has led Yanjing Liu, You-Xiong Wang and others in the Department's Fiber & Electro-Optics Research Center (FEORC) to develop nanomanufacturing processes that could someday provide an alternative method of making semiconductors, and affect such far-flung fields as water treatment and auto windshields.

Researchers have developed the capability to produce 2-nanometer-sized particles within a tight size distribution. They have also developed a self-assembly process for coatings based on the ultra-small particles they produce.

The significance of their work is the particles' small size and FEORC's ability to tightly control the size distribution. Currently most nanometer particle research involves sizes in the 10-nanometer range with a wider size distribution among the particles. "Ours have a diameter ratio five times smaller," said Professor Rick Claus, director of FEORC.

The work has led FEORC researchers in directions that could influence a variety of applications.

When the particles of a material get smaller, the surface area goes up relative to the volume, and some properties and characteristics of the material can change, explained Claus. "For example, the hardness goes up," he said. "In fact, we are working on a project involving ultra-hard coatings that could find applications in lenses, windshields, and headlights."

Optical properties also change with materials made from smaller particles. " UV absorption is greater, a property that could be used on windows, eyeglasses, and windshields where UV protection is important," Claus said.

"We have also seen what are called 'quantum sized effects,'" he noted. "We've developed particles smaller than a wavelength of light, which produce different emission and absorption characteristics.

As a result, the team is looking at products and devices that are related to absorption or generation of light - such as light-emitting diodes or lasers. "What makes it all work is that we can control the particle size. As engineers, if we want to design for a characteristic, we need to be able to control physical and chemical properties on the nanoscale," he said.

The group has gone beyond exploring properties of their small particles and has developed a method to produce films using a self-assembly technique developed by Liu. "We charge the particles either positive or negative, and suspend them in water. Then we take a substrate, usually glass (it's cheap), and dip it alternately in positive then negative solutions. We've built up films that way that are several microns thick."

One extension of the work is a project with the Air Force Office of Scientific Research to limit the amount of light that passes through a lens. "We're working with Randy Heflin, an expert in nonlinear optics," Claus said. "The films that we've developed have exhibited nonlinear behavior in optical device applications.

Eventually, the ability to build films from nano-particles could provide an alternative method of producing microelectronic circuits, he explained. "It's possible that we'll be able to build circuits from the ground up, instead of the current top-down method of etching a substrate."

The Bradley Department of Electrical and Computer Engineering
Virginia Tech

Last Updated, November 23, 1997
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