Lecturer: Jing Shi, associate professor of physics, University of Utah

Date: Wednesday Feb. 16, 2005

Time: 7:30 a.m.

Place: Little America Hotel, Ballroom A, 500 S. Main St., Salt Lake City

Note: This event is not open to the public, but media are invited to cover it.

Professor Jing Shi and colleagues have used an organic semiconductor – instead of a conventional semiconductor such as silicon – to make switch-like “spin valves” that can control the flow of electrical current. The researchers were able to change the flow of electricity through the valves by 40 percent. This advance in a field known as “spintronics” is an early step toward a new generation of miniature electronic devices such as computer memory chips, light-emitting diodes for displays and sensors to detect radiation, air pollutants, light and magnetic fields. “We are making progress toward devices that are made with organic materials and utilize a different property of electrons [their ‘spin’ rather than their electrical charge] for things like computer memory, computer processors and sensors of various types,” says Shi.

In electronic devices, information is stored and transmitted by the flow of electricity in the form of negatively charged subatomic particles called electrons. The zeroes and ones of computer binary code are represented by the presence or absence of electrons within a semiconductor or other material.

In spintronics, information is stored and transmitted using another property of electrons: their spin. Spin is the intrinsic angular momentum of a particle. One way to understand spin is to imagine that each electron contains a tiny bar magnet, like a compass needle, that points either up or down to represent the electron’s spin.

Electrons moving through a nonmagnetic material normally have random spins (half are up and half are down) so the net effect is zero. But magnetic fields can be applied so that the spins are aligned (all up or all down), allowing a new way to store binary data in the form of ones (spins all up) and zeroes (spins all down).

Spintronics “has quickly revolutionized magnetic recording technology [spin valves are used in ‘read heads’ that read computer hard drives] and is going to revolutionize random access memory (RAM) made of semiconductors,” says Shi. Compared with purely electronic computers, computers with spintronic memory should be able to store more data, consume less power and process data more quickly.

Compared with conventional semiconductors, organic semiconductors are inexpensive and simpler to make, can be manufactured at lower temperatures with fewer toxic wastes, have electronic properties that can be adjusted, and are flexible so they can be molded to desired shapes. Organic semiconductors already are used as light-emitting diodes for some flat-screen TVs, cell phone displays, some billboards and a few computer display screens.

The University of Utah College of Science Advisory Board sponsors the Science at Breakfast Lecture series.