March 31, 2003
FRONTIERS IN MATERIALS SCIENCE
VINSE COLLOQUIUM SERIES
Dr. William King
Woodruff School of Mechanical Engineering
Georgia Institute of Technology
"Thermomechanical Formation of Polymer Nanostructures"
Abstract. In thermomechanical data storage, a heated atomic force microscope (AFM) cantilever tip is in contact with and scans over a thin polymer film. Electrical activation of the silicon cantilever allows resistive heating near the cantilever tip. As the cantilever is heated, the polymer beneath the cantilever tip softens and is displaced, leaving an indentation of diameter near 25 nm. The same cantilever can detect the presence of a previously written indentation: as the cantilever tip follows the contour of a previously written indentation, the change in thermal impedance between the cantilever and the substrate causes a measurable change in the cantilever temperature. Finally, highly local heating near the cantilever tip allows for single-indentation erasing. A deep understanding of thermal transport in the cantilever, cantilever tip, and polymer layer is critically important to the design of a thermomechanical data storage device. Sub-continuum heat and mass transfer physics affect nearly every aspect of thermomechanical nanostructure formation: the thermal conductivity of the highly doped thin silicon cantilever has not been measured; the temperature of the tip-polymer interface cannot be directly measured and is expected to be lower than that predicted by continuum models due to phonon-boundary scattering in the cantilever tip; air rarefaction can limit the sensitivity of thermal detection; and the heat and mass transport properties of the thin polymer film are not known, as they vary with film thickness at thickness comparable to or below the polymer radius of gyration. This talk describes progress on modeling, simulation, and measurement of thermal processes during thermomechanical data storage. The talk also reports more recent work on developing the heated AFM cantilever as a scientific instrument for nanoscale thermal processing, metrology, and manufacturing.
Short Bio. William King received his Ph.D. from Stanford University in 2002, working in the groups of Ken Goodson and Tom Kenny. Between 1999 and 2001, he spent sixteen months as an IBM Graduate Research Fellow at the IBM Zurich Research center, working on Millipede thermomechanical data storage, in the group of Peter Vettiger and Gerd Binnig. At present, Dr. King is Assistant Professor of Mechanical Engineering at the Georgia Institute of Technology, where he advises four PhD students on thermal engineering of micro/nano-mechanical devices and atomic force microscopy. He is the winner of an NSF CAREER Award.