Cheap plastic grid holds promise of data storage

[Red Squirrel]

This is pretty cool. A new read only memory technology that is much cheaper to produce. Write once, read many times. This will be good for permanent applications such as roms in cameras and such.


http://www.iht.com/articles/119321.html

Electronic memory may find new home

It's just a humble plastic material, often used as an anti-static coating to keep fluff from clinging to computer screens. But researchers have made a property of this plastic, called Pedot, the basis for a new type of compact, inexpensive electronic memory that may one day store gigabytes of data on cameras, pocket-size music players and cellphones.

Memory devices that can store more data in less space are crucial to electronic gadgets. Plastics, though, have received relatively little attention as candidates for use in data storage.

Now a team of scientists at Princeton University and Hewlett-Packard has described an electronic memory based on the plastic, which changes its conductivity permanently when a high current is passed through it, in a recent article in the journal Nature. The new memory may be far cheaper to make than silicon microwafers manufactured in costly clean rooms. It could be fabricated simply and inexpensively, for example, by transferring the pattern for the memory continuously from a cylinder onto a substrate, much as newspapers are printed on a press.

"We can imagine making memory not out of expensive silicon chips but of less expensive organic materials that could be patterned in a process of continuous sheets," said Warren Jackson, a physicist at Hewlett-Packard Laboratories in Palo Alto, California, who is one of the authors of the paper.

The memory, which cannot be rewritten, is known as WORM, for "write once, read many times". Robert Sweet, a senior research fellow at the Palo Alto Research Center and an expert in chip fabrication, said the new design was a promising development.

"Because of the simple structure of the device," Sweet said, "it should be cheap to manufacture." Pedot, short for polyethylenedioxythiophene, acts somewhat like a fuse. At low voltages, the polymer conducts electricity; at higher voltages, conductivity drops, and the material gets hot. At about 200 degrees centigrade, or 390 degrees Fahrenheit, it becomes permanently nonconducting, like a blown fuse.

To make a memory device, a dollop of the polymer is placed at every intersecting point on a gridlike set of electrodes. To "write" data, voltages are applied across the grid; depending on the voltage, a particular point either remains conductive or becomes nonconductive, creating the logical ones and zeroes of digital memory, said Sven Moller, the lead author of the paper.

"A blown fuse blocks the current and can be read as a zero," Moller said.

An unblown fuse lets current pass and acts as a one. Moller, a physicist at Hewlett-Packard Labs in Corvallis, Oregon, discovered the behavior of the polymer when he was a postdoctoral researcher at the Princeton laboratory of Stephen Forrest, a professor of electrical engineering. Forrest led the current research team.

"Basically you make the polymer nonconducting by passing a lot of current through it," Forrest said of the design. "Then you go back and read it with a small current. "

The device is the first to use an architecture that combines organic and inorganic elements, he said. "This is a hybrid device that consists of the polymer - that's organic - layered on top of a thin-film silicon diode - that's inorganic - to make a compact memory application," Forrest said.

Most devices are purely inorganic or organic. "This takes advantage of the properties of both these materials," Forrest said.

The device integrates the polymer with the silicon diodes, which are deposited on a flexible foil substrate. The diodes, which allow current to flow in only one direction at each intersection of the electrode array, prevent current from leaking from one intersection to another, which could corrupt the data. The memory has the potential to store huge amounts of data in a small space.

"The whole device is superthin," Forrest said, "and we can stack many of these units on top of one another and still take up a small volume."

He estimated that 1 million bits of information could be squeezed into a square millimeter of the material. The device may have applications similar to those in which flash memory is used, said Craig Perlov, co-author of the paper and a physicist at Hewlett Packard Labs. "We can imagine it," Perlov said, "for holding maps for GPS in cars, for carrying information in a cell phone or music player, for digital cameras or a host of applications where you carry things with you with a memory that's not fragile and doesn't use a lot of power."

The New York Times

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