AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuA

Paper SS2-TuA2
Dislocation-Driven Surface Dynamics on Solids

Tuesday, November 16, 2004, 1:40 pm, Room 210C

Session: Welch Award Symposium: Nucleation and Growth
Presenter: S. Kodambaka, University of Illinois at Urbana-Champaign
Authors: S. Kodambaka, University of Illinois at Urbana-Champaign
S.V. Khare, University of Illinois at Urbana-Champaign
J. Bareno, University of Illinois at Urbana-Champaign
W. Swiech, University of Illinois at Urbana-Champaign
I. Petrov, University of Illinois at Urbana-Champaign
J.E. Greene, University of Illinois at Urbana-Champaign
Correspondent: Click to Email
Using low-energy electron microscopy, we investigate the near-equilibrium dynamics of surface-terminated dislocations. We observe, in real time, the thermally-driven (1500-1700 K) nucleation and shape-preserving growth of spiral steps rotating at constant temperature-dependent angular velocities (@omega@(T)) around cores of dislocations terminating on TiN(111) in the absence of applied external stress or net mass change. We measure @omega@ as a function of spiral geometry, N@sub2@ partial pressure, annealing time, and temperature. We find that @omega@ is independent of the local environment and ambient, and decreases linearly with time. From the temperature-dependent @omega@ data, we obtain an activation barrier of 4.9±0.3 eV for the growth of spirals. This phenomenon, attributed to point-defect migration from the bulk to the surface along dislocation lines, is both qualitatively and quantitatively different from step curvature-driven surface dynamics and "standard" Burton-Cabrera-Frank (BCF) spiral growth.@footnote 1@ Our results demonstrate that dislocation-mediated surface roughening can occur even in the absence of deposition or evaporation, and provide fundamental insights into mechanisms controlling nanostructural stability. We expect that this process is general and that it occurs in other materials.@footnote 1@ S. Kodambaka, S.V. Khare, W. Swiech, K. Ohmori, I. Petrov, and J.E. Greene, Nature, May 6th issue, 2004.