Semiconductor devices from polyacetylene - C&EN Global Enterprise

Sep 12, 1988 - Researchers at the University of Cambridge, U.K., have succeeded in fabricating semiconductor devices from polyacetylene, the simplest ...
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ILK's Oxford launches commercial ventures England's venerable Oxford University broke sharply with academic tradition last week when it launched two American-style private-sector initiatives. In the first case, the university created a marketing/licensing unit called Isis Innovation to facilitate a more aggressive approach to finding a market for its scientific discoveries. In the second, the university marked the formation, now nearing completion, of a British enterprise with Monsanto called Oxford Glycosystems. Isis Innovation, named after a tributary of the Thames on which Oxford is sited (as well as after the Egyptian goddess of fertility), is wholly owned by the university. Some loan funding is being advanced by two venture capital concerns, Advent Ltd. and Cogent Ltd., both London based. In return, they will be given first opportunity to invest in the discoveries. The organization is starting out with a roster of about a dozen innovative products and processes it believes companies around the world will be interested in licensing. One, for instance, centers on superconductivity. Another involves a DNA probe technique that can be used for cancer screening and prenatal monitoring of genetic defects. But Isis will serve as more than simply a broker for finding licensees for Oxford University's patented ideas and processes, explains James L. Hiddleston, its newly appointed managing director. It also will actively seek out partners for future commercial ventures. Oxford Glycosystems is such a company that Isis would have helped had it been formed sooner. The share participation of Monsanto and the university in the new concern hasn't been revealed. But some 6

September 12, 1988 C&EN

The design of the group's diodes and transistors looks conventional, except that a polyacetylene film is used in place of crystalline silicon. Because the molecular and electronic structure of polyacetylene is different from that of silicon, the polymer devices operate in a novel way not seen in silicon microchips. When charge is applied to the polymer chain, the double-bond arrangement changes in the vicinity of the charge, causing the polymer chain to buckle and kink, Friend explains. This, in turn, leads to a shift in the polymer's infrared absorption. Such behavior might be applied in electrooptic devices such as an optical computer, he notes. The Cambridge research, which is supported by British Petroleum, is described in the current issue of Researchers at the University of Nature [335,137 (1988)]. Friend says that these polymer Cambridge, U.K., have succeeded in fabricating semiconductor devices devices aren't likely to replace confrom polyacetylene, the simplest ventional inorganic semiconductors conducting organic polymer. The "in areas where inorganic semicondevices—transistors and diodes— ductors do an excellent job." But perform "several orders of magni- polyacetylene and other advanced tude better" than those previously materials will "find niches where reported for similar materials, ac- existing technologies don't work." cording to physicist David Bloor of U.S. industry has shown very litQueen Mary College in London. tle interest in developing organic Scientifically, the work is "enor- polymer-based semiconductor demously exciting," says chemistry vices. The silicon-chip industry is professor Alan G. MacDiarmid of so well tooled-up that it's not likely the University of Pennsylvania. But to accept the cost of retooling unwhether it will be technologically less a polymer technology is shown important "is difficult to say at this to be at least as good as silicon and much cheaper, MacDiarmid says. time," he adds. Allied-Signal Corp., which has the Scientists have been interested in replacing conventional inorganic largest and oldest conductive polysemiconductors such as silicon or mers group of any U.S. company, is germanium in electronic devices not interested in trying to make with conductive organic polymers. polymer-based semiconductor deBut difficulties in the chemical pro- vices, says one of the group's senior cessing and manipulation of these researchers, Larry W. Shacklette. polymeric materials have frustrated That application is too speculative, attempts to incorporate them into in his view. Although Friend's such devices. Polyacetylene, for ex- group "has really advanced the state ample, is a rigid polymer that is not of the art," he says, the performance of its polymer devices is "still far readily soluble in organic solvents. The Cambridge researchers, led below what you could obtain with by physicist Richard H. Friend, have single-crystal silicon devices." Japanese companies appear to be gotten a r o u n d this problem by adopting a stratagem invented by more interested in pursuing polya group at Durham University, U.K. mer-based electronics. Last year, for They first dissolve a precursor poly- example, researchers at Mitsubishi mer in 2-butanone and deposit it as Electric Corp. reported making a a thin, uniform film. Heating the transistor from polythiophene, anfilm causes a chemical reaction that other conducting polymer. converts it into polyacetylene. Ron Dagani

funding is being provided by the venture capital companies Advent and Alafi Capital. To be located at nearby Abingdon, Oxford Glycosystems will produce and market equipment and reagents used for screening and analyzing oligosaccharides and related compounds. These stem from a longstanding Monsanto-funded research project undertaken by Oxford University biochemistry professor Raymond Dwek. Dwek will remain in his present post while serving as a consultant to the new company. Dermot O'Sullivan

Semiconductor devices from polyacetylene