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Micromarval: wires thinned to nanometers.

Picture a magnetic carpet, each strand a wire only a few atoms thick.

This image is purely figurative. Yet it conveys a sense of what may soon be possible on a molecular scale with newly developed nanometer-size wires embedded in a thin film -- for example, higher quality audio and video tapes.

Such one-dimensional nanowires can now be made, says T.M. Whitney, a chemist at Johns Hopkins University in Baltimore. "We call them one-dimensional nanowires because they're small wires, only a few tens of nanometers thick, and because they're nearly one-dimensional structures," says Whitney. "They're not quite a string of atoms, but they behave like a string of atoms."

He and his colleagues report their work in the Sept. 3 SCIENCE.

Scientists have long wanted to make semiconductors this size, Whitney says. But making them has proved quite difficult. The Hopkins group set out to create such structures with ordinary metals. They etched long, thin tracks into a polycarbonate membrane, or film. The tracks ranged in width from 30 to 200 nanometers. Using a technique called electrochemical deposition, they placed nickel and cobalt into the narrow tracks, creating tiny metal wires.

"Most scientists make nonometer-size structures by physically putting things together," says Peter C. Searson, a chemist at Hopkins and a coauthor of the report. "But that technique doesn't work well for wires. What's important about our technique, using electrochemical deposition, is that we can make structures that others can't make using physical deposition. So this is a new, easy, and cheap processing technique for making hard-to-build nanometer-size structures."

These nanowires may prove useful for storing information because of their unique magnetic properties. "Their magnetic field is perpendicular to the film in which they're embedded, meaning that the field is much stronger along their length than along their width," Whitney says.

This feature could, potentially improve magnetic recording materials, such as video or audio tape. To make a better magnetic recording material, Whitney notes, "you want the wires embedded in the film, standing up parallel to each other, perpendicular to the film surface." That way, recording head, like the ones in a tape recorder or VCR, could glide right over the tops ofthe nanowires.

The limitation here is the size of the recording head. "No one has made a recording head that small yet," Whitney says.
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Title Annotation:nanometer-size wires embedded in thin film may improve magnetic recording materials
Author:Lipkin, Richard
Publication:Science News
Article Type:Brief Article
Date:Sep 11, 1993
Words:386
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