computer science to nanotechnology

Smaller, lighter computers and an end to worries about electrical failures sending hours of on-screen work into an inaccessible limbo mark the potential result of Argonne research on tiny ferroelectric crystals.

"Tiny" means billionths of a meter, or about 1/500th the width of a human hair. These nanomaterials behave differently than their larger bulk counterparts. Argonne researchers have learned that they are more chemically reactive, exhibit new electronic properties and can be used to create materials that are stronger, tougher and more resistant to friction and wear than bulk materials.

Improved nano-engineered ferroelectric crystals could realize a 50-year-old dream of creating nonvolatile random access memory (NVRAM). The first fruits of it can be seen in Sony's PlayStation 2 and in smart cards now in use in Brazil, China and Japan. A simple wave of a smart card identifies personnel or pays for gas or public transportation.

Computing applications

RAM – random access memory – is used when someone enters information or gives a command to the computer. It can be written to as well as read but - with standard commercial technology - holds its content only while powered by electricity.

Argonne materials scientists have created and are studying nanoscale crystals of ferroelectric materials that can be altered by an electrical field and retain any changes.

Ferroelectric materials – so called, because they behave similarly to ferromagnetic materials even though they don't generally contain iron – consist of crystals whose low symmetry causes spontaneous electrical polarization along one or more of their axes. The application of voltage can change this polarity. Ferroelectric crystals can also change mechanical to electrical energy– the piezoelectric effect – or electrical energy to optical effects.

A strong external electrical field can reverse the plus and minus poles of ferroelectric polarization. The crystals hold their orientation until forced to change by another applied electric field. Thus, they can be coded as binary memory, representing "zero" in one orientation and "one" in the other.

Because the crystals do not revert spontaneously, RAM made with them would not be erased should there be a power failure. Laptop computers would no longer need back-up batteries, permitting them to be made still smaller and lighter. There would be a similar impact on cell phones.

Achieving such permanence is a long-standing dream of the computer industry.

"Companies such as AT&T, Ford, IBM, RCA and Westinghouse Electric made serious efforts to develop non-volatile RAMs in the 1950s, but couldn't achieve commercial use," said Argonne researcher Orlando Auciello. "Back then, NVRAMs were based on expensive ferroelectric single crystals, which required substantial voltage to switch their polarity. This, and cross talk inherent in the then recently devised row matrix address concept, made them impractical.

"Working on the nanoscale changes this," said Auciello. "It means higher density memories with faster speeds and megabyte (the amount of memory needed to store one million characters of information) - or even gigabyte (one billion bytes) - capacity. It's not clear how soon such capacity will be available, but competition is heavy, stakes are high, and some companies claim they will have the first fruits of this research within two years."