Plastic memory retains data

Researchers from Johannes Kepler University in Austria have borrowed a technique from audio recording technology to fashion a new type of computer memory made from organic, or plastic materials.

The memory works in a way similar to common ferroelectric transistor memory elements, which store the 1s and 0s of computer information as one of two electric polarization directions. The researchers' device uses a charge electret, or material that stores electric charge, rather than ferroelectric material to store information. Electret material is more commonly used in a type of microphone.

The method could eventually be used to make inexpensive plastic computer memory for devices like radiofrequency ID tags, smart cards, electronics devices that can be integrated into textiles, and plastic computer chips, according to the researchers.

The researchers' prototype stored data for more than 15 hours after power to the device was turned off.

The prototype memory cell consists of an indium tin oxide gate electrode, a layer of polyvinyl alcohol, a semiconductor layer containing the spherical carbon molecules dubbed buckyballs, and chromium source and drain electrodes. When a voltage is applied to the device, an electric charge is trapped in or on the polyvinyl alcohol layer.

The device has a charge carrier mobility of about 10 square centimeters per volt second. Existing organic semiconductor devices have carrier mobilities ranging from less than one to about 10. Carrier mobility is a measure of a device's ability to conduct electricity.

It will be five to ten years before the memory can be used in practical applications, according to the researchers. The work appeared in the November 29, 2004 issue of Applied Physics Letters.