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New view solves semiconductor puzzle.

By delicately parting curtains of electrons, scientists have gazed for the first time into channels on a crystal of the semiconductor gallium arsenide (SN: 8/16/97, p. 102).

Their images, plus computer models, of the uneven landscape settle a decade-long debate, say Vincent P. LaBella of the University of Arkansas in Fayetteville and his colleagues. The terrain is where microcircuit makers grow tiny lasers and high-speed electronics vital to cell phones and other communications gear.

Until now, scientists were uncertain which of four possible patterns the surface atoms of gallium arsenide assume. The arrangement of arsenic atoms seen in the channels favors a pattern known as beta-2, which earlier X-ray studies had suggested, the researchers conclude. The scientists also present supercomputer calculations supporting the beta-2 finding.

"What you really need today is agreement from many different techniques to pin it down," LaBella says.

Microelectronics makers will find it easier to craft new devices by knowing the true arrangement of atoms on the gallium arsenide surface, researchers say. By using an atomic-resolution, scanning tunneling microscope (SN: 10/24/98, p. 268) at low voltage, the team peered past electron clouds into channels, a technique that also promises to be effective for other materials whose surfaces have remained unresolved, such as indium phosphide.

The researchers describe their method and results in the Oct. 11 PHYSICAL REVIEW LETTERS.
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Publication:Science News
Article Type:Brief Article
Geographic Code:1U7AR
Date:Oct 23, 1999
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