Chance discovery increases electric conductivity exponentially

Accidental exposure to light led to a 400-times increase in the conductivity of a crystal.
By Ananth Baliga  |  Nov. 14, 2013 at 11:33 AM
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Nov. 14 (UPI) -- Researchers at Washington State University have accidentally increased the conductivity of a crystal 400 times, simply by exposing it to light.

Doctoral student Marianne Tarun noticed that the conductivity of strontium titanate, an oxide of strontium and platinum, shot up after she happened to leave it out one day. After assuming the sample was contaminated, she conducted further experiments and found it was actually caused by the light.

"It came by accident," said Tarun. "It's not something we expected. That makes it very exciting to share."

The phenomenon, called persistent photoconductivity, does not produce the same effect as superconductivity, which is zero electrical resistance achieved at temperatures reaching absolute zero. The fact that photoconductivity can be achieved at room temperature makes this finding more practical.

While other researchers have created persistent photoconductivity in other materials, this is the most dramatic display of the phenomenon.

"The discovery of this effect at room temperature opens up new possibilities for practical devices," said co-author Matthew McCluskey. "In standard computer memory, information is stored on the surface of a computer chip or hard drive. A device using persistent photoconductivity, however, could store information throughout the entire volume of a crystal."

The effect, which lasted for days after the light source was turned off, could herald an drastic improvement in the performance of devices like computer chips. The findings have been published in Physical Review Letters.

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