Abstract
The possibility for a localized roughness to develop has been investigated at the intersection of the interface and the free surface of an epitaxially stressed bilayer. After a general derivation of the elastic energy variation due to a localized fluctuation of the surface described by a function h, the stability of the free surface with respect to two particular fluctuations has been characterized as a function of the lattice mismatch between the two layers. The formation of cracks from the localized roughness is finally discussed.