Electrical properties of highly strained epitaxial Pb(Zr,Ti)O3 thin films on MgO(100)

The film thickness (20-200 nm) dependence of the crystalline structure? lattice parameters and electrical properties of highly strained Pb(Zr,Ti)O-3 (PZT) thin films on MgO(100) was investigated. The PZT films were practically c-axis orientation. As the film thickness decreased (<100 nm), the tetragonality ratio of PZT also decreased owing to the inner expanding strain in the inplane direction. The dielectric constant decreased and the structural phase transition temperature shifted to a lower temperature corresponding with the decrease in the tetragonality ratio. The electric displacement-electric field (D-E) hysteresis curves for the thick (>40 nm) films exhibited a certain amount of remanent polarization in the in-plane direction, implying the formation of a-domains. The relationship between electrical properties and the inner strain is discussed.