Improved dielectric and electrical insulating properties in Pb(Mg _1/3Nb _2/3) _0.62Ti _0.38O ₃ based multilayer ferroelectric thin films

The dielectric, ferroelectric, and electrical insulating properties of Pb(Mg _1/3Nb _2/3) _0.62Ti _0.38O ₃ thin film and Pb(Mg _1/3Nb _2/3) _0.62Ti _0.38O ₃-PbZr _0.53Ti _0.47O ₃ (PMNT-PZT) multilayer thin films including PMNT/PZT, PZT/PMNT and PZT/PMNT/PZT prepared on LaNiO ₃/SiO ₂/Si substrates were investigated. It is found that the PMNT based multilayer films show larger dielectric constant and lower dielectric loss compared with the monolayer PMNT film. Moreover, the multilayer thin films exhibit little temperature dependence of dielectric properties over a broad temperature range from 30 to 270 °C. In addition, well saturated polarization-versus-electric field hysteresis loops with large spontaneous polarization of 22.2-23.9 μC/cm ² for the multilayer films are obtained due to their good electrical insulating properties. The leakage current densities in the multilayer films are about three orders of magnitude lower than those in the monolayer PMNT thin film under electric field E > 70 kV/cm. We argue that the reduction of the leakage current densities is mainly attributed to the formation of a depletion zone/layer between layers by incorporating layers of PZT in multilayer structures acting as a potential barrier for free carriers to transport as well as carrier scattering at interfaces supported by the measurements on dielectric and electrical insulating properties. The results demonstrate that the multilayered thin films exhibit enhanced dielectric, ferroelectric and electrical insulating properties for ferroelectric memory devices.