A Kinetic Monte Carlo study on the decaying of nanostructures by surface diffusion

MARCOS F. CASTEZ

Mar del Plata

Conferencia; XV Conference on Nonequilibrium Statistical Mechanics and Nonlinear Physics” (Medyfinol 06); 2006

Universidad Nacional de Mar del Plata

Changing shapes in the nano-world is a very fascinating and active field both from the technological and scientific points of view. Within this general topic, the decaying of nanostructures by surface diffusion, since this the leading surface relaxation mechanism at the nanoscale, has received considerable attention in the last years. In this work, we consider a stochastic (1+1)-dimensional discrete model for the study of the decay of periodic patterns by surface diffusion on a bi-dimensional triangular lattice, that mimics a terrace between rectilinear steps on a (111) face of a FCC solid. The model was implemented in the Kinetic Monte Carlo framework, witha proper relationship between real time and Monte Carlo steps; activation barriers for atom-hopping were taken from a simple harmonic model. Simulations on this model for pattern decay in the low temperature regime show interesting deviations from linear theory of surface diffusion, including non-exponential decay of pattern amplitudes and spontaneous overhangs formation, and acceptable qualitative description of such theory as well (for instance, we obtain, for small aspect-ratio patterns, the well-known dependence k~lambda^4 from linear theories of surface diffusion for the decay constant as a function of the wavelength of a sine-like pattern), depending on whether or not the interfaces are under the small slopes approximation. The emergence of metastable states in the form of nano-island and nano-voids is also discussed.Finally, we compare model results with those from a continuous (deterministic and non-linear) model for which surface diffusion currents are driven by curvature.