UF Engineers' Lab-Altered Silicon Could Speed Computers Dramatically

October 2, 1998

GAINESVILLE — When scientists and engineers began using silicon to make semiconductor devices more than 40 years ago, it was the first step in what would turn out to be one of the most powerful inventions of the 20th century: the computer chip.

Now, University of Florida engineers are experimenting with new silicon properties — with possible benefits ranging from dramatically accelerating computer speeds to the creation of “micro motors” thought to have potential for medical and other uses.

Rolf Hummel, a UF materials science and engineering professor, pioneered, and continues to refine, a technique called “spark processing” that causes silicon wafers to emit light and makes them magnetic, two properties they do not have naturally.

As part of the technique, first patented in 1995, researchers expose silicon wafers, thin slices of silicon used as bases for electronic components or circuits, to repeated sparks from a counter electrode in a chamber. By varying the frequency of the sparks, types of gasses in the chamber and other factors, researchers can change the silicon’s structure at will. The resulting wafers have raised, porous areas with radically different electrical, optical and magnetic properties than the surrounding silicon.

Depending on the variables the researchers choose, the process can make the altered silicon capable of emitting violet, blue or yellow-green light.

This is significant because it could one day bridge a gap between optics and electronics that currently impedes faster computers, said Mike Stora, a graduate student researching spark processing for his doctorate in materials science and engineering.

Today’s computers may have microprocessors capable of running at speeds of 400 megahertz, but copper wire and other electronic equipment connecting to the processor slows computing speeds to 100 megahertz, Stora said.

If the chips transmitted information through light rather than electronic signals — and the copper wire and other equipment were replaced with fiber optics and light sensitive materials — entire computers could run at the speeds of their processors.

“If you could have both light emitters and detectors on a silicon chip with the computer on the chip, too, you could have chips communicate with each other directly over fiber-optic lines,” Stora said. “There would be a dramatic increase in speed.”

For average computer users, that would result in faster Internet downloads and quicker access to hard-disk memory, among other benefits.

Hummel said light-emitting chips also could be used to speed up long-distance transmission over fiber-optic telephone lines, a technology that currently relies on periodic electronic amplification. By eliminating the copper wire and making the process entirely light-dependent, transmission speeds could become as much as 1,000 times faster, he said.

Spark-processed silicon chips are a step in this direction, but significant obstacles remain. The UF research team has found the chips emit the most visible light when exposed to invisible, ultraviolet light from a laser or other source. The chips do not emit as much light when exposed to electricity, a problem researchers attribute to their lack of knowledge about how to get electricity into the material. This hurdle must be overcome if spark-processed chips are to be useful in computers.

“We haven’t worked out all the bugs of this material to get it to work with electro-luminescence,” Stora said.

Spark-processing also makes chips (ferro) magnetic, which could lead to their use in “nanomachines,” tiny machines smaller than gnats believed to have promise in medicine and other fields, Stora said. No one has created the machines yet, but precursors such as miniature pressure detectors and gears mounted on computer chips have been demonstrated, he said.