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A recipe for microwave semiconductors.

Two researchers have discovered that the kitchen-counter microwave can be a handy tool for making bulk materials used in semiconductors.

Andrew R. Barron and Christopher C. Landry of Harvard University found a faster and easier way to make chalcopyrites, materials used in semiconductors for solar ceils.

Scientists prepare extremely thin films of chalcopyrite and layer them to build semiconductors. Making the chalcopyrite is the hard part, though. The conventional method requires days of high-temperature and high-pressure conditions to convert a mixture of elements to crystalline chalcopyrite.

In the June 11 SCIENCE, Barron and Landry report that they can now make chalcopyrites in just three minutes. They mix the proper ratio of copper, indium, and sulfur powders and seal them in a quartz tube. Then they place this reddish mixture in a microwave oven and zap it for one minute. (Metals usually explode in a microwave oven, but not if they are in powder form.) After shaking up the contents, the researchers cook the mixture for another two minutes. The result is a bluish-gray crystalline powder.

Analysis by X-ray diffraction shows the product to be a chalcopyrite called copper indium disulfide. The pure elements no longer exist, according to the results of X-ray photoelectron spectral analysis. The researchers also made a chalcopyrite with selenium in place of sulfur.

Avariety of interesting compounds can probably be made in a microwave, says Barron. Because the oven allows scientists to heat and cool a substance very rapidly, researchers can create and study unusual phases, he says. "You can make phases that perhaps nature never intended:' he adds.

Barron and Landry are now trying to develop their method to make chalcopyrites of consistently high quality for use in semiconductor devices.
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Title Annotation:microwave used to make batches of chalcopyrites
Publication:Science News
Article Type:Brief Article
Date:Jun 19, 1993
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