Large piezoelectric response in (111)-oriented epitaxial Pb(Zr,Ti)O3 films consisting of mixed phases with rhombohedral and tetragonal symmetry

Abstract

$\mathrm{Pb}(\mathrm{Zr,Ti}){\mathrm{O}}_3$ films with a $\mathrm{Zr}\mathrm{/(}\mathrm{Zr}+\mathrm{Ti})$ ratio of 0.48 having 1.5 μm in thickness were grown on ${\text{(100)}}_c$ -, ${\text{(110)}}_c$ -, and ${\text{(111)}}_c$ -oriented ${\mathrm{SrRuO}}_3\mathrm{//}{\mathrm{SrTiO}}_3$ substrates by metalorganic chemical vapor deposition. It was ascertained by θ–2θ scans of x-ray diffraction that ${\text{(001)}}_T{\text{-/(100)}}_T{\text{-/(100)}}_R$ -, {110}-, and {111}-oriented films were epitaxially grown on ${\text{(100)}}_c$ -, ${\text{(110)}}_c$ -, and ${\text{(111)}}_c$ -oriented substrates. Polarization and field-induced strain in these films were simultaneously observed through a scanning probe microscope that was attached to a ferroelectric test system. About three times larger field-induced strain than that on other substrates was observed together with the largest spontaneous polarization for a film grown on a ${\text{(111)}}_c{\mathrm{SrRuO}}_3\text{//(111)}{\mathrm{SrTiO}}_3$ substrate. High-resolution x-ray diffraction analysis suggested that the film grown on the ${\text{(111)}}_c{\mathrm{SrRuO}}_3\text{//(111)}{\mathrm{SrTiO}}_3$ substrate consisted of rhombohedral and tetragonal mixture phases. Its crystal structure possibly contributed to the large piezoelectric response.