Transparent transistors promise windshield displays

Transparent transistors promise windshield displays

Comprising transparent nanowires assembled on a transparent glass or plastic substrate, researchers at Northwestern and Purdue Universities have created transparent transistors and circuits. The important step promises new and advanced applications ranging from e-paper and flexible color screens to displays in auto windshields.

“Our study demonstrates that nanowire electronics can be fully transparent, as well as flexible, while maintaining high performance levels,” said Tobin J. Marks, the Vladimir N. Ipatieff Professor of Chemistry and a professor in the Dept. of Materials Science and Engineering at Northwestern University. “This opens the door to entirely new technologies for high-performance transparent flexible displays.”

The nanowires are transparent because they are made of made of zinc oxide or indium oxide, materials that do not absorb light in the visible range of the spectrum.

Transistors are typically connected to circuitry by tiny lines of metal that act as wires. But in the new approach, the nanowires are the transistors. “This is a different kind of wire,” said David Janes, a researcher at Purdue University’s Birck Nanotechnology Center and a professor in the School of Electrical and Computer Engineering. “It is basically taking the place of the silicon in silicon electronics.”

According to Janes, the technology owes its improved performance to a better on-off ratio, which helps conserve power. “In a transistor, you are trying to turn it off and on, like a switch,” he said. “But unlike a wall switch in your house, a transistor never really turns completely off. There is always a little bit of leakage through it, sort of like crimping a garden hose.” The nanowire transistors help to reduce this leakage while also offering the possibility of precisely controlling the pixels in displays.

The nanowires used in the research measure as small as 20 nanometers in diameter. The thin-film transistors could be produced less expensively and under lower temperatures than standard CMOS processes, making them ideal to incorporate into plastic films, which melt under high-temperature processing. “You can get high performance because the nanowires themselves give you some unique performance advantages, and you could still think of dispersing them down over large areas for displays, smart credit cards and other applications,” Janes said.

Research has been funded by NASA through the Institute for Nanoelectronics and Computing, based at Purdue’s Discovery Park, and at Northwestern University. Future research is expected to include work to integrate the thin-film transistors into large circuits and to develop ways to interconnect numerous transistors.

The technology also could be used to create new flexible antennas that unfurl like a sail and aim their signals more precisely than current antennas. Further, thetechnology exhibits “carrier mobilities” similar to conventional microprocessors, meaning electrons travel in the devices at nearly the same speed as current consumer electronics but in a low-cost, flexible package.

For more information, go to http://news.uns.purdue.edu/3month.html, call David Janes at 765-494-9263, e-mail
; or call Tobin J. Marks at 847-491-5658 or e-mail
.

Ralph Raiola