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A microelectronic breakthrough: chips that need no semiconductor

Using this new technology, scientists may someday be able to build faster and more powerful electronic devices, such as solar panels.

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    Engineers at the University of California San Diego have fabricated the first semiconductor-free, optically-controlled microelectronic device. Using metamaterials, engineers were able to build a microscale device that shows a 1,000 percent increase in conductivity when activated by low voltage and a low power laser.
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Scientists at the University of California San Diego have created the world's first microelectronic device that needs no semiconductors. Instead, this chip is made of metamaterials that can be activated by a weak laser pulse and low voltage.

The device, described last week in the journal Nature Communications, is 1,000 percent more conductive than a standard transistor. Using this new technology, scientists may someday be able to build faster and more powerful microelectronics such as solar panels.

“This certainly won’t replace all semiconductor devices, but it may be the best approach for certain specialty applications, such as very high frequencies or high power devices,” co-author Dan Sievenpiper, a professor of electrical engineering at UCSD, said in a statement.

Since the 1950s, transistors have powered nearly every commercial electronic on the market. When powered by an electrical current, these little metalloid devices can switch between on and off states in a circuit and amplify electronic signals.

But these devices can only be as powerful as the materials that compose them. Transistors are made of semiconductors – that is, any solid more conductive than an insulator but less conductive than most metals. Semiconductive materials have a band gap, which means they need plenty of outside energy to start the flow of electrons. Those electrons collide with atoms as they race through the transistor, limiting their velocity and hindering the speed of the device.

There’s room for improvement, to be sure. In September, researchers from the University of Wisconsin-Madison developed the first carbon nanotube transistor to outperform the usual silicon variety.

The Christian Science Monitor’s Weston Williams reported:

The material consists of carbon atoms linked together in a cylindrical molecular structure, forming microscopic tubes. The structure of these nanotubes makes them extremely strong proportional to their size and weight, giving them have extraordinary electrical semiconductive properties.

But Dr. Sievenpiper’s device goes a step further, ditching the semiconductor altogether. Instead, researchers etched tiny nanostructures into an array of gold strips. They attached this metasurface to a silicon “wafer,” and added a layer of silicon dioxide in between the two.

This metamaterial can be “excited” by less than 10 volts of power and a low-energy infrared laser. That creates “hot spots” on the gold nanostructure, which in turn produce strong enough electrical fields to decouple electrons from the metastructure. The electrons can then move about freely.

The chip, of course, is only a proof-of-concept. To optimize performance for practical electronic devices, researchers will first need to design different metasurfaces.

“Next we need to understand how far these devices can be scaled and the limits of their performance,” Sievenpiper said.

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