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Abstract
A Landau-Ginsburg-Devonshire-type thermodynamic theory is used to describe dense laminar domain structures in epitaxial ferroelectric thin films grown on “tensile” substrates and to compute their small-signal dielectric responses. For PbTiO3 and BaTiO3 films, it is found that the ferroelectric phase transition results in the formation of a pseudo-tetragonal polydomain a 1/a 2/a 1/a 2 state. The stability range of the a 1/a 2/a 1/a 2 structure in the misfit strain-temperature phase diagram is determined. Effects of domain formation on the dielectric properties of ferroelectric films are analyzed by comparing permittivities of polydomain and single-domain films. Theoretical results are compared with the experimental data on (Ba1−xSrx)TiO3 films grown on platinum coated silicon substrates.