Strain relaxation by domain formation in epitaxial ferroelectric thin films

The origin of strain-induced, modulated domain structures observed in epitaxial ferroelectric lead titanate thin films is discussed using a phenomenological total-energy calculation. Linear elasticity is used to account for the substrate contribution while a free-energy functional of the Landau-Ginzburg-Devonshire type is used to calculate the domain-wall and the polarization contributions from the film. Good agreement between the predictions of this model and the experimental results is found for thickness-dependent properties such as the relative domain population and spontaneous strain.