A research fellow from the Xerox Research Centre of Canada has described the design and synthesis of semiconducting organic polymers that allow the printing of electronic patterns on a plastic substrate, paving the way for the printing of integrated circuits on plastic sheets instead of etching them on silicon wafers. Beng Ong made his presentation Tuesday (Dec. 3) at the Materials Research Society's fall conference in Boston.
The research is conducted with a grant from the National Institute of Standards and Technology, under which scientists from the Xerox Research Centre of Canada and the company's Palo Alto Research Center are collaborating with teams from Motorola Labs and Dow Chemical to develop novel organic electronic materials and processing technologies for the fabrication of large-area electronic devices, using relatively inexpensive printing technologies instead of semiconductor lithography.
In contrast to other materials that degrade quickly when exposed to oxygen, Xerox said its materials are stable in air, a requirement for low-cost manufacturing under ambient conditions. No other company has been able to achieve this combination in a polymer material, Xerox said.
In his presentation Tuesday at the MRS meeting, Ong described the design and properties of new polythiophene materials, which exhibit better performance dimensions than currently established polymers. The experimental organic semiconductor material developed by his group is second-generation smectic liquid crystal with field effect transistor mobility of up to 0.12 square centimeters per volt-second a measure of the speed of electron movement an electric field. That speed could be up to an order of magnitude greater than other polymer benchmarks measured in the same device architecture, Xerox said.
In addition, the devices exhibited excellent current on-off ratios, and little bias stress, hysteresis or instability in air. The breakthrough achieved by Ong and his group is to bring together all these thin-film transistor properties simultaneously within a material that is processable in ambient conditions. That hasn't been done before, Xerox said.
"One of the main cost advantages of printed plastic transistors is that they will not need specialized, costly fabrication facilities and procedures, while silicon transistors require ultra-clean room environments, high-temperature vacuum systems, and complex, photolithographic processes," said Ong in a statement. Ong, a holder of more than 110 U.S. patents, manages the printed organic electronics group at Xerox Research Centre of Canada, in Mississauga, Ontario.