Domain structures in highly (100)-oriented epitaxial Pb(Zr0.35,Ti0.65)O3 thin films

Abstract

Epitaxial tetragonal Pb(Zr0.35,Ti0.65)O3 films were grown on SrRuO3(100)∕SrTiO3(100) substrates by metal organic chemical vapor deposition. Their ferroelectric domain structures and microstructure were investigated using synchrotron x-ray diffraction and transmission electron microscopy. Highly a-axis oriented films were obtained by decreasing the compressive thermal strain resulting from the low growth temperature and thick film. The a and c domains were significantly tilted and had fourfold symmetry, and their tilt angles to the substrate normal were ∼0.5° and ∼0.9°, respectively. The film contained three domain structures: an a-c domain structure consisting of a periodic array of twin domains, an a1-a2 domain structure in which the a1 and a2 domains were rotated with respect to each other by 90° about the substrate normal direction, and a bilayer twinning structure coexisting with the a-c domain structure and a1-a2 domain structure. The bottom layer was the a1-a2 domain structure, and the top layer was the a-c domain structure. This bilayer structure may be due to a yet unknown domain evolution mechanism in which the strain of the films is inhomogeneous.