A level-set method for simulating island coarsening

Modeling of microstructural evolution during thin-film deposition requires a knowledge of several key activation energies (surface diffusion, island e dge atom diffusion, adatom migration over descending step edges, etc.). The se and other parameters must be known as a function of crystal orientation. In order to generate values for these parameters, we have developed a nume rical simulation in tandem with physical experiments. By tuning the simulat ion to the results from experiments Lye can extract and verify approximate values for these parameters. The numerical method we use is based upon the level set method. Our model is a continuum model in directions parallel to the crystal facet, and resolves each discrete atomic layer in the normal di rection. The model includes surface diffusion, step edge dynamics, and atta chment/detachment rates all of which may depend upon the local geometry of the step edge. The velocity field for advancing the island edges in the lev el set framework is generated by computing the equilibrium adatom density o n the flat terraces resulting in Laplace's equation with mixed boundary con ditions at the step edges. We have turned to the finite element method for solving this equation, which results in very good agreement with analytical ly known solutions and with experiment, (C) 2000 Academic Press.