Attempts to create circuits that save what's "up" on a screen have used high voltages, which quickly wears down computer electronic components, and have been expensive.

Now scientists at Sandia National Laboratories and France Telecom have applied for a patent on a prototype memory-retention device that is inexpensive, low-powered, and simple to fabricate.

The device, referred to as "protonic," is reported in today's issue of the journal Nature.

To transmit data, the device uses embedded protons, which remain where they are when the power turns off, thus preserving the information. In devices such as D-RAMs (dynamic random access memory), typically based on electron flow, the information is lost when the power is turned off.

To create the memory-retentive chip, only a few steps must be added to the hundreds currently used to fabricate microchips. The key additional step is to bathe the hot microchip in hydrogen gas. The gas, permeating the chip, breaks up into single ions -- i.e., protons -- at defects in the silicon dioxide. (The defects were created by the heat of the manufacturing process.) The protons can roam only within the chip's central layer of silicon dioxide, where they are trapped by two layers of silicon that sandwich the silicon dioxide.

The Sandia researchers found that:

• A positive low-voltage applied to one side of the silicon repels the protons to the far side of the silicon dioxide.

• A negative low-voltage applied to the silicon attracts the protons to the near side of the silicon dioxide.

If the power is turned off, the protons stay where they are, retaining information in the chip circuit.

Development of the process had its origin on the back of a napkin at an IEEE conference in December 1995 in Charleston, S.C. The discussion, subsequent work, and patent involved Sandians Bill Warren (principal investigator), Karel Vanheusden, Dan Fleetwood, and, at France Telecom, Roderick Devine.

First observation of the effect that protons remain in silicon when it is baked at high temperatures in hydrogen gas came as part of a systematic study at Sandia and France Telecom of the effects of hydrogen on silicon.

"For defense reasons, we're always interested in radiation-hardened, low-voltage chips," said Fleetwood.

The work is funded by Sandia's Laboratory Directed Research and Development Program, which funds which finances speculative defense-related research, and the Defense Advance Research Projects Agency.

Sandia is a multiprogram DOE laboratory, operated by a subsidiary of Lockheed Martin Corp. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major research and development responsibilities in national security, energy, and environmental technologies and economic competitiveness.

Technical visuals available