Crystal structure and polarization phenomena of epitaxially grown Pb(Zr,Ti)O3 thin-film capacitors

{100} oriented Pb(Zr,Ti)O3 (PZT) thin films were deposited by metalorganic chemical vapor deposition on both Ir/MgO(100) and Ir/MgAl2O4/SiO2/Si(100) substrates. The x-ray Φ-scan spectra for the (202) reflections revealed each film had fourfold symmetry, which was epitaxially grown as cube-on-cube. The switchable polarization (Qsw) of the PZT capacitor on the MgO substrate attained 100 μC/cm2 at 1.8 V; however, PZT capacitors on Si had a Qsw of 23 μC/cm2. This difference in Qsw is attributed to the volume fraction of (001) orientation of each PZT film. The difference in orientation between the two kinds of PZT films does not seem to depend on misfit of lattice parameters between PZT and Ir, but on the stress caused by the difference in the thermal expansion coefficients of MgO and Si.