Nonequilibrium Interface Dynamics:
Fundamental Physical Issues in Nonequilibrium Interface Dynamics

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Kinetic Surface Segregation and the Evolution of Nanostructures

Dr. Jerry Tersoff

IBM Research

Abstract:   The dynamics of a solid evolving exclusively by surface diffusion is a classic problem in materials physics. However, when the material is an alloy, the classic continuum equations are not directly applicable. Instead, it is necessary to consider a distinct surface layer whose properties may be discontinuous from the bulk. The resulting new continuum equations exhibit novel behavior not seen for single-component systems. Even in the simplest case, the decay of a non-planar surface profile, the system exhibits "kinetic surface segregation". This leads to a crossover between two different exponential decay rates. As a result, evolution at the nanoscale can be qualitatively faster than expected from extrapolation of macroscopic evolution. Numerical solutions of the continuum equations illustrate the rich behavior even for this simple case. Results are also presented for the more complex behavior occurring during strained-layer heteroepitaxy, e.g. alloying during formation and overgrowth of "self-assembled quantum dot" islands.