Kinetic aspects of thermodynamical instabilities

The instability of a coherent (i.e., without misfit dislocations), epitaxial film with respect to surface shape modulation is, in the absence of growth, an activated process if the surface has a singular orientation, e.g., (001). If the misfit is small, the activation energy is very large and practically forbids the instability. It was recently pointed out by Tersoff that the nature of the instability is deeply modified by growth. In the case of a small misfit, Tersoff used the theory of capillary effects elaborated by Nozières and Gallet in 1987 to argue that the growing surface becomes linearly unstable as in the case of a non-singular surface. In the following pages, the effect of time is addressed in the case of singular, initially planar surface. It is claimed that the instability is neither linear, nor thermally activated, but of a third type. In fact, it appears after a well-defined time. To cite this article: J. Villain, C. R. Physique 4 (2003).