Protons as memory aids.

One of the nightmares of the computer age is losing an important document when a power outage or some other mishap shuts down the computer before the user could save the file. Researchers have now harnessed protons embedded in a layer of silicon dioxide to develop a prototype microelectronic device that stores digital data and retains that information when the power is turned off.

In conventional memory chips, data are stored as patterns of electric charge, which tends to leak away. Those wayward electrons must be replaced regularly, so if the power goes off, the information disappears.

Developed by scientists at the Sandia National Laboratories in Albuquerque and France Telecom in Meylan, the new memory device consists of a layer of silicon dioxide between layers of silicon. When the silicon sandwich is raised to a high temperature and bathed in hydrogen gas, hydrogen molecules enter the material and break up into individual protons and electrons. The protons migrate to the middle layer and stay there when the device is cooled to room temperature. Essentially, "we create a trap for protons in the oxide layer," says Sandia's Daniel M. Fleetwood.

Applying a negative charge to one of the silicon layers attracts the protons to the boundary between the silicon and silicon dioxide layers, where they congregate. A positive charge forces them to the opposite boundary. When the charge is removed, the protons remain where they are. Recent experiments show that the protons stay put for long periods and are not greatly affected by radiation or temperature changes.

"We've now built transistors based on this effect," Fleetwood says. If developed further, the new device may provide an inexpensive, low-power, radiation-tolerant, easy-to-fabricate alternative to current methods of saving data on special chips.