Low-Temperature preparation of highly (001)-oriented PZT thin films on Pt/Ti/SiO₂/Si using LaNiO₃ as a buffer layer

LaNiO₃ (LNO) thin films on Pt/Ti/SiO₂/Si substrates were prepared by a simple chemical solution technique using lanthanum nitrate and nickel acetate as the start materials. A subsequent Pb(Zr_0.50Ti_0.50)O₃ thin film annealed at 550 degree(s)C on the LNO-coated Pt/Ti/SiO₂/Si substrate was prepared with a modified sol-gel process. The techniques of x-ray diffraction and scanning electron microscopy were used to characterize the structure of the films. All the electrical measurements were carried out in a Pt-ferroelectric-LNO/Pt configuration. Pt was sputter deposited into the sample using a mask and the bottom electrode (LNO/Pt) was etched to be exposed by ion etching technique. The resistivity of the LNO film and the ferroelectric and fatigue properties of the Pt/PZT/LNO/Pt/Ti/SiO₂/Si capacitor were measured by the four-point probe method and RT66A system, respectively. The LNO film shows good metallic property, which is comparable with the LNO films derived from physical techniques. It is found that the PZT thin film annealed at 550 degree(s)C is pure perovskite phase with highly (001) orientation, even though the LNO layer is randomly oriented polycrystalline. The ferroelectric capacitor derived from these films displayed a good P-E hysteresis loop at an electric field of 200 kV/cm with P_r and E_c of 16.6 (mu) C/cm² and 46 kV/cm. The PZT thin film capacitor does not show obvious drop in polarization up to 10⁹ switching cycles.