PSu Magazine Winter 2002

is an expert in carbon nanotubes, which may one day be used to create molecular-scale transistors and semiconductors. because of their potential use in mak– ing tiny transistors and emiconduc– tors. That's because the tubes are chemically resistant and have conduc– tive and in ulating qualitie that could make them useful as wire-either by themselves, or filled with metal. IBM has successfully made transis– tors out of this material, and Bell Lab– oratories has made a molecular- cale transistor out of another carbon sub– stance. Both of these accomplishment point to a future-perhaps a decade or more from now-when nanotubes or other forms of carbon may replace sili– con-based semiconductor . This means that thousands of times more transis– tor will be able to fill a given micro– processor than is possible today. "Twenty or 30 year ago, we never thought computer cou ld be as sma ll as they are today. But there are limita– tions; a silicon wafer cannot hold an infinite number of transistors. It will top someday. The prediction is that in 20 years or so we will have to have some new material to use," Jiao says. The problem is how to custom manufacture the tubes. ight now, there' a certain ele– ment of chance in making car– bon nanotubes, which is done in an arc discharge reaction chamber or by evaporating hydrocarbon ga es to cre– ate deposits around a catalyst. It's a nano-scale high-tech ver ion of grow– ing stalagmite crystals in a child's aquarium. Scienti ts such as Jiao can control the width of a tube' hollow core, and can manipulate and clean the tubes with the use of an ion beam that can focus down to nanometer scale. But much more need to be done in order for nanotubes to have practical use . "These tubes have strong mechani– cal propertie , but we have to develop them in a controlled manner. The cha llenge i to make them tronger, straighter, curvier-whatever the application calls for," say J iao. Imagine a transistor smaller than a speck of dust, and you begin to under– stand the scale on which she and other scientists are working. ne of tho e scientists is Rob Daasch, associate professor of electrical engineering and head of the University's Integrated Circuit Design and Test Laboratory. Daasch is an expert in analyzing how circuits and semiconductors fai I. His work has been a boon to companies such as LSI Logic, which come to him to test problem cir– cuits and po sibly to improve design. The devices Daa ch analyzes are on a scale of 10 to hundreds of nanome– ters-much bigger than the scale of J iao's research. But finding the defects in those devices requires zooming in clo e. "If I have a transistor 70 nanome– ters long, the broken part would be a WI TER 2002 P U MAGAZINE 9