Non-uniform strain in epitaxial surface gratings: Beyond the ordinary elastic description

A generalized elastic description of non-uniform strain in layered epitaxia l surface gratings is presented. The proposed total free energy of the syst em contains a surface term responsible for the interaction energy between d ifferent media, beside the ordinary bulk elastic energy density contributio n. The equilibrium equations and the related boundary conditions correspond ing to the actual deformed state are obtained. The presence of surface crys talline order induced on amorphous material by a crystalline substrate is a lso discussed. (C) 1999 Published by Elsevier Science B.V.