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Silicon-Based Spintronics

First of its kind computing prototype.

Today’s computers work by moving and storing electronic charge. But manipulating another property of electrons, their quantum-­mechanical “spin,” would be faster and take far less energy. Researchers have been working on “spintronics” for years, and now electrical engineers at the University of Delaware and at Cambridge ­Nano­Tech in Cambridge, MA, have made the first proto­type device that measures spin in silicon.

Spin chip: An array of one-¬millimeter-square silicon spintronic devices sits in a chip carrier.

Electron spins come in two directions, up and down, which could represent the 1 and 0 of binary computation if spin could be controlled and detected. In the proto­type, energized electrons first hit a magnetic cobalt-iron layer, which filters out electrons with down spin. The remaining up electrons pass through a 10-micrometer silicon layer and hit a detector consisting of a nickel-iron layer on top of a copper layer; all the layers sit on a silicon substrate. “It’s a very ingenious scheme to electrically generate and transport spins in silicon, [to] electrically detect the spins, and doing all of this on a chip,” says David Awschalom, a physicist who studies semi­conductor spintronics at the University of California, Santa Barbara.

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