HOW do you make transistors run faster? Add rocket fuel, of course.
Hydrazine, a toxic liquid sometimes used as a fuel in rocket motors, has turned out to be ideal for helping to make faster thin-film transistors, a crucial component of liquid crystal displays. What鈥檚 more, it does so in a novel 鈥渨et鈥� manufacturing process that should lend itself to cheaper mass production of these critical components.
Each pixel of an LCD is switched on and off by a thin-film transistor on the back of the display. These transistors are built up from fine layers of semiconductors deposited on a silicon substrate. But if the semiconductor can be deposited as a liquid blob and smeared outwards by spinning the substrate like a high-speed record turntable, displays could plummet in price. Until now, however, transistors made this way have been too slow to drive liquid crystal displays.
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Now David Mitzi and colleagues at IBM鈥檚 T. J. Watson Research Center in Yorktown Heights, New York, have managed to create fast thin-film transistors this way (Nature, vol 428, p 299). The key was the discovery that the semiconductor tin disulphide, which is insoluble in most liquids, can be dissolved in hydrazine if sulphur is added to the mix.
By applying the solution to a silicon substrate and spinning it they were able to create a coating that left a layer of tin disulphide just 5 nanometres thick when heated. When laced with electron-rich and electron-poor 鈥渄opants鈥� to turn the semiconductor into a transistor, the device was 10 times better at carrying electric charge than previous transistors.
鈥淚t is certainly a step forward,鈥� says Mercouri Kanatzidiz, at Michigan State University. 鈥淭hey have demonstrated some very clever chemistry.鈥� He predicts that 鈥渨et鈥� manufacture could become the method of choice for mass-producing thin-film transistors.
