HRTEM investigation of 90° domain configureuration and P-E hysteresis loop of epitaxial PZT multilayered thin films

Multi-layered epitaxial Pb(Zr_x,Ti_1-x)O₃ (PZT) films of x=0.2-0.5 were deposited on La_0.5Sr_0.5CoO_3-x (LSCO)/ (001)STO and LSCO/CeO₂/YSZ/(001)Si substrates with buffer layers. It was investigated how the 90° domain structure and the P-E hysteresis character depend on the difference of the thermal expansion coefficient by changing the Zr/Ti composition and the substrates, using HRTEM and XRD methods. XTEM analysis showed that usual lamella configuration of 90° domains of 8-30 nm in width penetrated the columnar grain and the PZT layer in the PZT stacked film of Zr/Ti=20/80, 30/70, 40/60. On the other hand, the close-packed 90° domains of 4-5 nm in width existed in a epitaxial columnar grain in the PZT50/50 stacked film. The P-E hysteresis loops of PZT20/80 stacked films deposited on STO and Si substrates show the remanent polarization of 2Pr=136 μC/cm², 2Pr=80 μC/cm², respectively. On the other hands, those of PZT50/50 stacked films deposited on STO and Si substrates show the polarization of 2Pr=125 μC/cm², 2Pr=36 μC/cm², respectively. Thus, the P-E hysteresis loop of PZT50/50 has remarkable difference of 2Pr between the substrates.