Nanoscale Structures: Lability, Length Scales, and Fluctuations

Abstract

This article is an edited transcript based on the David Turnbull Lecture given by Ellen D. Williams of the University of Maryland on December 2, 2003, at the Materials Research Society Fall Meeting in Boston. Williams received the award for “groundbreaking research on the atomic-scale science of surfaces and for leadership, writing, teaching, and outreach that convey her deep understanding of and enthusiasm for materials research.” This article focuses on the special properties of small structures that provide much of the exciting potential of nanotechnology. One aspect of small structures—their susceptibility to thermal fluctuations—may create or necessitate new ways of exploiting nanostructures. The advent of scanned probe imaging techniques created new opportunities for observing and understanding such structural fluctuations and the related evolution of nanostructure. Direct observations show that it is relatively easy for large numbers of atoms—the kinds of numbers that are present in nanoscale structures— to pick up and move about on the surface cooperatively with substantial impact on nanoto micron-scale structures. Such labile evolution of structure can be predicted quantitatively by using length-scale bridging techniques of statistical mechanics coupled with scanned probe observations of structural and temporal distributions.The same measurements also provide direct information about the stochastic paths of structural fluctuations that can be used outside of the traditional thermodynamic framework. Future work involves moving beyond the classical thermodynamic picture to assess the impact that the stochastic behavior has on the physical properties of individual nanostructures.