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.
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