Looks good on paper

PHOTO COURTESY OF XEROX

Beng Ong examines a sheet of printed-plastic transistors, the results of lab work conducted at the Xerox Research Centre of Canada (XRCC). The Xerox research fellow is overseeing efforts to print circuits on polymer sheets rather than etch them on silicon wafers. Ong, an inventor with more than 110 U.S. patents, unveiled the breakthrough in semiconducting organic polymers at a Materials Research Society conference in December.

The Xerox researchers are using NIST funds to explore novel materials and printing technologies. In collaboration with Xerox's Palo Alto Research Center, the scientists are working with teams from Motorola and Dow Chemical to develop new organic electronic materials and processes for large-area electronic devices. These devices include flexible electric paper displays and portable TV screens the size of posters, Xerox says.

The technology dispenses with cleanrooms, high-temperature vacuums, and photolithography. The materials are stable in air, a key to low-cost manufacturing, Ong points out. "One of the main cost advantages of printed-plastic transistors is that they will not need specialized, costly fabrication facilities and procedures," he asserts. The scientist manages the printed organic electronics group at XRCC in Mississauga, Ontario.

Ong says the new polythiophene materials perform significantly better than established polymers. His research group developed second-generation smectic liquid crystal with FET mobility of up to 0.12 cm²/V•s, or the speed of electron movement per unit electric field. Ong says that speed could reach an order of magnitude greater than other polymer materials measured in the same device architecture. The experimental material also shows little bias stress or hysteresis.

Xerox claims it is the first time these breakthrough thin-film transistor properties have been combined within a material that can be processed in air.

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