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Researchers create nanoscale "lightning" switches



Gaithersburg (MD) - Scientists from the National Institute of Standards and Technology (NIST) have demonstrated a prototype nanoscale electronic switch that is described to like a "lightning" and could replace nanoscale memory circuits sometime in the future.

Shrinking semiconductor structures will be increasingly difficult at levels what already are touching 45 nm and are quickly taking aim at 32 nm and below. New approaches to enable power-efficient scaling of electronic devices such as transistors and switches will be critical for the progress of the chip industry.

A new idea comes from the NIST, where scientists have created a new nanoswitch, which takes advantage of electrical reactions of silver, which generally has a high conductivity: When exposed to an electrical field, silver reacts by creating tree-like branching growths of crystals. Typically, this effect can short-out microelectronic devices, but if a silver wire is coated with a molecule that forms a self-assembled monolayer on the wire, these growths apparently can be controlled.

NIST scientists said that a critical voltage level can trigger silver ions to form and quickly branch through the organic monolayer. In a demonstration, the silver branches made contact with a gold wire "just like a lightning bolt," scientists said. When a silver filament reaches the gold, it forms a short circuit, causing a dramatic change in conductance, which is easily detectable. Reversing the voltage retracts the filament and "opens" the switch, the scientists said.

Advantages of the silver switch include that it is operational with organic monolayers that works a variety of molecule coatings, a simple construction that can be used for a large array of switches and a high efficiency between on and off states, providing electrical resistance ratios of "a million or more," the NIST said.

However, researchers conceded that there are several hurdles to overcome before the technology could be used in any product. For example, the silver switches are volatile and require the voltage has to be kept on to retain the switch state. Also, switching speeds are relatively slow at a rate of 10 KHz and switches currently freeze at the close position after "a large number of cycles."

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