Domain structures in highly (100)-oriented epitaxial Pb(Zr_(0.35),Ti_(0.65))O_3 thin films

摘要

Epitaxial tetragonal Pb(Zr_(0.35),Ti_(0.65))O_3 films were grown on SrRuO_3(100)/SrTiO_3(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 a_1-a_2 domain structure in which the a_1 and a_2 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 a_1-a_2 domain structure. The bottom layer was the a_1-a_2 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.