Effects of a PbTiO3 seed layer on the structural and the electrical properties of PbZr0.35Ti0.65O3 thin films

Ten-nm-thick PbTiO3 (PTO) thin films and 150-nm-thick PbZr0.35Ti0.65O3 (PZT) thin films were coated on Pt/IrO2/Ir bottom electrodes with sol-gel solution by using a spin-on-coating method. When the baked PTO seed layers were annealed for crystallization at temperatures of 550 - 600 degrees C prior to PZT coating, randomly oriented crystallites were formed on the (111)-oriented Pt/IrO2/Ir bottom electrodes, which induced the random orientation of the PZT films on the PTO seed layers and caused poor ferroelectric properties. In contrast, the PZT films deposited on the baked PTO seed layers, which were not crystallized, showed strong (111)-orientation and rather small and uniform grains. The (111)-oriented PZT films also showed excellent ferroelectric properties. The remanent polarization (2Pr), the coercive voltage (2Vc), and the squareness of the hysteresis loop measured in the PZT capacitor annealed at a very low temperature of 550 degrees C were about 61 mu C/cm(2), 1.8 V and 0.69, respectively. The leakage current density was about 2 x 10(-6) A/cm(2).