Cheap material makes speedy memory

Cross the common plastic polystyrene with gold particles that aren't much bigger than molecules and you've got a thin film of material that can be used to store information.

Researchers from the University of California at Los Angeles and the Rohm and Haas Electronic Materials Company have devised a potentially low-cost, high-speed nonvolatile memory from polystyrene and gold nanoparticles. Nonvolatile memory retains information even when it is not powered.

The memory can be easily manufactured from inexpensive materials, making it potentially much cheaper than today's flash memory chips; it can be read to and written electronically, making it potentially much faster than today's CDs and DVDs, according to the researchers.

The researchers' prototype is a layer of polystyrene and gold particles sandwiched between aluminum electrodes. The device is easy to manufacture and uses little power, according to the researchers. Layers of the film can be stacked, making it possible to store even more information in a given area.

The researchers prepared a solution of polystyrene and gold nanoparticles ranging from 1.6 to 4.4 nanometers in diameter and used a common manufacturing technique -- spin-casting -- to produce a thin layer of the material. A nanometer is one millionth of a millimeter.

Applying a positive voltage of 2.8 increases the amount of electricity the device conducts by about 10,000 times. Applying a negative voltage of 1.8 returns the device to its low conductivity state. The two states can represent the 1s and 0s of computer information.

The device switches between the two states in 25 nanoseconds, or billionths of a second.

The plastic memory device could be used practically in two to five years, according to the researchers. The work appeared in the November 28, 2004 issue of Nature Materials.