Ferroelectric Domain Structures in Epitaxial PZT Thin Films: A Review

Abstract

Heteroepitaxial growth of thin films of non-cubic ferroelectric materials on cubic single crystal substrates inevitably accompanies twin domain formation. Since the presence of twin domains strongly affects on the ferroelectric properties, studies on the twinning phenomena are crucial for controlling their properties. Ferroelectric twin-domain formation in epitaxial Pb(Zr,Ti)O 3 thin films has been investigated by changing several processing parameters such as film composition, substrate selection, and film thickness in order to determine the crucial stain factors controlling final domain structures. In order to investigate the effect of transformation strains involved in the phase transition at and below the Curie temperature, epitaxial (Pb 1 m x La x )(Zr y Ti 1 m y )O 3 thin films grown on MgO(001) have been examined as a function of composition, x and y, and temperature. The effect of misfit strain and its relaxation during film fabrication on the final domain structures of epitaxial PbTiO 3 was studied by changing cubic substrates including MgO(001), SrTiO 3 (001), and KTaO 3 (001). In particular, considering thermodynamic equilibrium relief of coherency strain at the initial growth stage based on the Mattews-Blakeslee criteria, effect of film thickness on domain formation was analyzed for the epitaxial PbTiO 3 thin films grown on MgO(001) substrates, and the correlation of final domain structures with the degree of misfit strain relaxation by dislocation generation was established. Finally, evolution of equilibrium domain structures in epitaxial PZT thin films was simulated successfully by the finite element method employing a commercial package, ABAQUS, and the strains un-relaxed during film fabrication could be reasonably estimated.