Effect of manganese oxide insertion layer on the dielectric and ferroelectric properties of Pb_0.92La_0.08Zr_0.52Ti_0.48O₃ films grown by a sol-gel process

We incorporated a ≈5-nm-thick MnO_x insertion layer in the middle of a ≈1.38-μm-thick Pb_0.92La_0.08Zr_0.52Ti_0.48O₃ (PLZT) film grown by a modified sol-gel process and measured the dielectric and ferroelectric properties of PLZT films with and without MnO_x insertion layer. By incorporation of the MnO_x layer, residual stress was reduced from ≈350 MPa to ≈125 MPa, dielectric permittivity decreased from ≈1300 to ≈950, while dielectric loss increased from ≈0.04 to ≈0.07 as measured at 10 kHz. Also, remanent polarization increased from ≈9.1 μC/cm² to ≈11.7 μC/cm², coercive field increased from ≈28.7 kV/cm to ≈40.3 kV/cm, and internal bias field from ≈3 kV/cm to ≈14 kV/cm. We have observed decreased irreversible Rayleigh coefficient and dielectric nonlinearity on samples with MnO_x insertion layer. These changes in properties are attributable to Mn cation doping as acceptors near the MnO_x/PLZT interface, which forms oxygen vacancies and defect induced dipoles like 2Mn′_Ti-V_O^•• (or Mna″_Ti-V_O^••), acting effectively as pinning centers to hinder domain wall movement.