Electrical properties of PLZT thin films formed by photochemical metal-organic deposition with various Zr/Ti ratios

Lanthanum-doped lead zirconate titanate (PLZT) films formed by photochemical metal-organic deposition using photosensitive starting precursors were characterized. The substitution of La for Pb was found to induce the improved ferroelectric properties, especially fatigue property through the reduction of oxygen vacancies with excess electrons. But remnant polarization was reduced, because the doping of La gives the same effect as shift of composition of Zr/Ti ratio in PLZT film from morphotropic phase boundary composition of PZT(Zr/Ti ratio of 56/44). The measurement results of polarization-electric field and capacitance-voltage indicate that the composition of maximum ferroelectric properties of PLZT film shifts toward Ti-rich side between 52/48 and 48/52 of Zr/Ti ratio. A decrease in Zr/Ti ratio induced an improvement in I-V and fatigue properties due to the low defect concentration such as Pb or O vacancies and the inter-grain depletion of grain boundary limited conduction.