Effects of domain formation on the dielectric properties of ferroelectric thin films

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.