Ordering dynamics of surfaces in molecular beam epitaxy

The growth of thin films under conditions typical for molecular beam epitaxy is unstable, if potential barriers at step edges suppress the diffusion of adatoms to lower terraces. In these cases the dynamic evolution of the surface morphology is characterized by slope selection leading to pyramid-like structures and coarsening. The late stages of growth can be described by Langevin equations that are similar to equations that model spinodal decomposition or Ostwald ripening with the slope of the surface profile being the order parameter. It is shown that the surface evolution can be understood in terms of domain ordering, however, the orientation of the domain walls is strongly influenced by lattice anisotropies. This coupling slows down the coarsening dynamics.