Argonne research on tiny ferroelectric crystals –”Tiny” means billionths of a meter, or about 1/500th the width of a human hair–paves the way for potentially smaller and lighter computers. 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 the 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.
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.
Smart cards don’t forget
Argonne scientists are using their expertise in ferroelectrics to improve smart cards. These are the size and shape of credit cards but contain ferroelectric memory that can carry substantial information, such as its bearer’s medical history for use by doctors, pharmacists and even paramedics in an emergency. Unlike magnetic strips on credit cards, these memories do not come in contact with their readers and will not wear out.
Current smart cards carry about 250 kilobytes of memory.
Closeness breeds material changes
Changes in material behavior because the materials are so close (proximity effects) show up in giant magneto-resistance, a phenomenon discovered in 1988 and used in computer hard drives. Tiny magnetic bits are hard to read individually, but interleaved nanolayers of cobalt, copper, iron and chromium show substantial changes in resistance in magnetic fields because the layers are so close together. IBM and the magnetic recording industry have used this to create ultrasensitive hard-drive read mechanisms.
The computer world might one day be based in magnetic properties instead of electrical. This might make it possible to build computers with architectures that could be restructured depending on the task of the moment. The same machine could be configured like a Macintosh for tasks that a Mac operating system performs best and like a PC when Windows OS is preferable.
Also possible could be magnetic configurations that would not be limited by binary logic, making them more like the human brain.