Magazine article Science News

Electrons Trip on Tiny Semiconductor Steps

Magazine article Science News

Electrons Trip on Tiny Semiconductor Steps

Article excerpt

Increasingly, engineers refer to the heads that read computer hard disks as "spintronics devices." That's because these sensors use the orientations of electrons' magnetic fields, or spins, to read the ones and zeros of digital information.

If scientists could extend spintronics to semiconductor chips, faster, cooler-running, lower-power devices might result. However, efforts to make spintronic components have stalled because electrons injected into semiconductors often don't maintain their up or down spin orientations.

In the May 25 SCIENCE, a team at the University of Arkansas in Fayetteville reveals a surface feature of semiconductors that appears responsible for flipping those electronic spins. Using a scanning tunneling microscope (STM) to probe gallium arsenide, Vincent P. LaBella and his colleagues have found that a surface step only two dozen atoms high can disrupt the spin orientation of more than 80 percent of the electrons injected there.

"This is the first time, I believe, that people have observed on the nanometer scale the disruption of spin injection," LaBella says.

To determine the fate of electrons' spins, the Arkansas researchers scanned the semiconductor surface while injecting electrons into it. To acquire information about the electrons, they simultaneously measured light rays emitted from the material. Melding those approaches "is really quite a beautiful idea," comments David D. Awschalom of the University of California, Santa Barbara. …

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