The role of the transition function in a continuum model for kinetic roughening and coarsening in thin films

In the model for kinetic roughening and coarsening in high-temperature supe r-conducting thin films that Ortiz et al. suggest in (J. Mech. Phys. Solids 47(1999) 697.) a transition function is used which takes the energetics of the boundary layer at the film/substrate interface into account. Apart fro m having some basic properties, this function can be chosen quite arbitrari ly. We show that certain decay and concavity properties of this function have a major impact on the film growth. In particular, a modified decay can circu mvent the occurrence of negative film heights which is predicted in the ori ginal model, and a change in curvature alters stability properties of the f ilm. These observations not only underscore the importance of the transitio n function in the model, but they also suggest to estimate the actual trans ition function from experimental data or from atomistic simulation. (C) 200 1 Elsevier Science Ltd. All rights reserved.