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Thin-Film Semiconductors Get Boost from Rocket Fuel




DAVID B. MITZI
Scientists at IBM say they have developed a new method for making high-performance semiconductors that are only a few molecules thick, potentially paving the way for a new era in electronics.

Semiconductors are central components of devices we use every day. For example, they control the flow of electricity through the 42 million transistors that power the average computer. Whereas semiconductors used in computer microprocessors are getting ever smaller, other applications, such as flat-panel displays, have led researchers on a search for semiconductors that are ever flatter. The key to features such as higher resolution in flat-panel displays, says David B. Mitzi, lead author of the study published today in the journal Nature, is the semiconductor¿s "carrier mobility"--a measure of how quickly electrical charge moves through it.

The simplest and cheapest technique for making thin-film semiconductors is a chemist¿s high-tech version of spin-art known as spin-coating, in which a solution of semiconductive material is poured onto a spinning plate and the force of the spinning motion spreads the material into a uniformly thin sheet. The trick has been getting ahold of a substance possessing the necessary properties in liquid form: scientists have been unable to find solvents to make such solutions¿until now.

Mitzi and his colleagues used hydrazine--a volatile liquid once employed as rocket fuel--to dissolve so-called metal chalcogenides, compounds comprised of tin, sulfur and selenium. The materials they produced have a charge mobility 10 times as great as that of any semiconductor film previously made with this technique. "These types of easily processed semiconducting films could eventually be used to make circuitry for very low cost or flexible displays, high-performance smart cards, sensors and solar cells, or for flexible electronics coated onto a wide variety of molded or plastic shapes," Mitzi notes.

The group is now working on replacing the hydrazine with a more environmentally friendly solvent, Mitzi reports. And although the 10-fold increase in charge mobility is a big advancement, his team believes it can be further improved upon. --Alla Katsnelson

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