Interdisciplinary team to investigate the modification of electrical properties by adding molecules to silicon semiconductor surfaces
January 16, 2008 — An interdisciplinary term of researchers at the University of Virginia has been awarded $1.3 million by the National Science Foundation to study a problem that threatens the continued evolution of microelectronics.
John Bean, the J. M. Money Professor of Electrical and Computer Engineering in U.Va.'s School of Engineering and Applied Science, is the principal investigator for the Nanoscale Interdisciplinary Research Team, which proposes adding organic molecules to silicon surfaces as a means of controlling its electrical conduction, and as the basis for new forms of quantum conduction.
Other team members are Lloyd Harriott, Virginia Microelectronics Consortium Professor of Electrical and Computer Engineering and chairman of the Charles L. Brown Department Professor of Electrical and Computer Engineering; Avik Ghosh, assistant professor of electrical and computer engineering; Lin Pu, professor of chemistry; and Keith Williams, assistant professor of physics.
“Silicon, by itself, is a poor conductor: its electrons are almost entirely locked in its atoms or their bonds,” said Bean. “So, instead, the silicon transistors of integrated circuits depend on mobile electrons liberated from a sprinkling of special impurities. But as transistors shrink in volume, the number of these randomly positioned impurities is no longer predictable, and the transistors cease to function as designed.”
A draconian solution is to discard 50 years of silicon transistor technology and try to substitute something else. One suggestion has been to use organic molecules that act as electrical switches, but no one has succeeded in assembling more than a handful of these switches – much less the hundreds of millions or even billions now required in a single integrated circuit.
"So rather than relying on organic molecules as a long-shot replacement for transistors," said Harriott, "we are combining the two ideas — adding molecules to the surface of silicon where they may be able to supply the necessary electrons for even the smallest of future transistors."
Being able to design custom molecules with exactly the conductive properties you want, and to arrange those molecules on a silicon surface in an organized, controllable way, could restore the uniformity of transistors even as they shrink to the near atomic dimensions desired in future mass-produced electrical devices such as computer chips.
"The implications of this research will be seen in years to come," says James H., Aylor, dean of U.Va.'s Engineering School. "The ability to design molecules and then count them on the surface of semiconductors to influence conductivity will influence computer memory, sensors and a whole host of entirely new electronic devices on the nano scale."
The NSF grant is building on previously work on nanoscience education that was begun with an earlier grant from the NSF. Bean and his team are working with the Science Museum in Richmond, Va. to develop hands-on educational displays to explain the intricacies of nanoscience to visitors. The team is also continuing its development of a prototype "Hands-On Introduction to Nanoscience" for undergraduate students of all majors early in their college careers. The innovative class's subtitle is "We're Not in Kansas Anymore!" and it emphasizes the need to show students that at the nanoscale the familiar rules of Newtonian physics no longer apply as the weirdness of quantum mechanics takes its place.
This course is now being adapted by the team and the museum for the training of Commonwealth K-12 science teachers. It is also being used to anchor nanoscience curricula at other Virginia colleges, including Danville Community College's effort to train employees for new nanotech start-up companies being recruited into Southside Virginia.
This is the second Nanoscale Interdisciplinary Research Team grant for U.Va.'s Engineering School. A similar interdisciplinary group was awarded funding five years ago to manipulate memory devices by synthesizing organic molecules.
About the University of Virginia School of Engineering and Applied Science
Founded in 1836, the University of Virginia School of Engineering and Applied Science combines research and educational opportunities at the undergraduate and graduate levels. Within the undergraduate programs, courses in engineering, ethics, mathematics, the sciences and the humanities are available to build a strong foundation for careers in engineering and other professions. Its abundant research opportunities complement the curriculum and educate young men and women to become thoughtful leaders in technology and society. At the graduate level, the Engineering School collaborates with the University's highly ranked medical and business schools on interdisciplinary research projects and entrepreneurial initiatives. With a distinguished faculty and a student body of 2,200 undergraduates and 700 graduate students, the Engineering School offers an array of engineering disciplines, including cutting-edge research programs in computer and information science and engineering, bioengineering and nanotechnology.