Fabrication And Electrical Properties Of PbTiO₃/PbZrO₃ Ferroelectric Superlattices

Ferroelectric materials have attracted much attention for their broad application prospect in ferroelectric random access memories,thin-film capacitors,microelectro-mechanical systems and other fields.Lead zirconate titanate[Pb(ZrxTi1-x)O3,PZT]as a typical ferroelectric material is always a search hotspot for researchers since there has not formed a consistent conclusion about the ferroelectric mechanism of PZT near the morphotropic phase boundary(MPB,Zr/Ti=52/48).It was thought highly likely that the excellent electrical properties may be related to the specific strain state of PZT.With the development of the superlattice fabrication technology,researchers can fabricate a specific microstructure to make an in-depth study on some problems.In this study,we design the PTO/PZO ferroelectric superlattices to simulate the PZT phase diagram.To study the electrical properties,we changed the total thickness and the modulation period thickness to get different interface stress states of the PTO/PZO ferroelectric superlattices.We prepared a series of PTO/PZO ferroelectric superlattices with different modulation period thicknesses,the total thicknesses were 200 nm and 250 nm respectively.We found that the total thickness and the modulation period thickness jointly affected the strain states and electric properties of the PTO/PZO superlattices through the contrast experiment analysis.The overall superlattice strain relaxation state was affected by the total thickness,and when the total thickness was constant that the ferroelectric and dielectric properties were enhanced with the decrease of the modulation period thickness.The electric properties of the PTO/PZO superlattices were influenced by the increase of the number of PTO/PZO interfaces,the enhanced dipole coupling effect between the ferroelectric phase and the antiferroelectric phase,the magnitude of the lattice distortion and so on.In addition,we found that the[PTO25/PZO25]10 ferroelectric superlattice exhibited an electric-field-induced phase transition from antiferroelectric to ferroelectric.This phenomenon may be mainly due to the strain states of the Nb:STO substrate,the PTO/PZO interfaces,and the dipole coupling effects between the PTO layer and the PZO layer.