Domain structure transition from two to three dimensions in tensile strained (100)/(001)-oriented epitaxial tetragonal PZT film

Abstract

Pb(Zr0.05Ti0.95)O3 thin films of 30 nm thickness were epitaxially grown at 600 °C on (001) KTaO3 single crystal substrates by metal organic chemical vapor deposition. Films consist of the mixture of the a/c-domain composed of the c-domain with out-of-plane polarization and the a-domain with in-plane polarization and the a1/a2-domain formed by the combination of a-domains whose in-plane polar axes are orthogonal to each other. Films above the Curie temperature (Tc) of 550 °C were found to be under the in-plane tensile strain and transformed to a1/a2-domains at Curie temperature when the temperature decreased. This a1/a2-domain further changed to the mixture of the a/c-domain and a1/a2-domain below 350 °C. This indicated that the two-dimensional domain structures of the a1/a2-domain changed to three dimensional ones below Tc. Although the a/c-domain was induced to relax the strain, the a1/a2-domain was still unrelaxed. This is different from the widely investigated in-plane compressive strained films that have a one to three dimensional domain structure.