Structural characterization and 90° domain contribution to ferroelectricity of epitaxial Pb(Zr0.35,Ti0.65)O3 thin films

Abstract

Remanent polarizations (Pr) of 200-nm-thick epitaxial Pb(Zr0.35,Ti0.65)O3 (PZT) thin films deposited on (001), (110), and (111) SrTiO3 (STO) substrates coated with SrRuO3 (SRO) were compared to the domain configurations that were precisely and quantitatively characterized by high-resolution x-ray diffraction reciprocal space mapping (HRXRD-RSM). (001)/(100), (101)/(110), and (111) oriented domains were obtained for films grown on (001), (110), and (111) STO substrates coated with SRO, respectively. HRXRD-RSM showed that the films grown on (001) and (110) STO substrates mainly consisted of (001) and (101) domains, although they also included about 32% and 25% of (100) and (110) domain, respectively. Tilt growths in the domains were found except for the (001) domain. The tilt growths in the (100), (101), and (110) domains were attributed to the geometrically induced tilt by the 90° domain that had {101} domain walls. On the other hand, the tilt in the (111) domain was attributed to the misfit strain relaxation by introducing tilt growth in the domain but not due to the 90° domain. The Pr ratios of films having different domain configurations were well explained by the estimated Pr ratios from the volume fractions of the domains, based on the assumption that the 90° domain was not reoriented by the externally applied electrical field and did not contribute to the measured Pr values. This indicates that the 90° domain is strongly pinned in epitaxial 200-nm-thick PZT films and the 180° domain switching is the dominant contribution to the total remanent polarization.