Two Dimensional Ferroelectricity And Thickness Dependent Ferroelectric Polarization In Bi₂WO₆ Thin Film

This article mainly introducing the pulsed laser deposition growth and ferroelectric characterization of the multiferroic oxide Bi₂WO₆ thin film which holds ferroelectricity and ferroelasticity simultaneously.At the first,Growing the c-axis oriented Bi₂WO₆thin film shows high quality on the traditional oxide substrate Sr Ti O3（001）successfully.Verifying the four oriented in plane ferroelectric polarization in the Bi₂WO₆thin film by the piezoelectric force microscopy.Using the local electric field applied by the AFM tip on the thin film surface,we could easily switch in plane ferroelectric polarization.In consideration of the tiny lattice mismatch between the Bi₂WO₆ and Nd Ga O₃（110）substrate,Growing the Bi₂WO₆thin film on the Nd Ga O₃（110）we could get an oxide system reserve ferroelectricity when approaching the two-dimensional limit,which demonstrated by STEM and PFM.Growing the Bi₂WO₆thin film on the Nd Ga O₃（110）substrate with various thickness,we observed a abnormal out of plane ferroelectric polarization in the c-axis oriented Bi₂WO₆thin film when thicker than 20 nm.Uniting Spherical aberration correction and PFM,we found some intriguing WO₃ intercalation in the Bi₂WO₆thin film which supposed to be the possible origin of the abnormal out of plane ferroelectric polarization.By controlling the substrate and condition in the Bi₂WO₆thin film growth,we could get lots of Bi₂WO₆ nanostructure which holds different kinds of ferroelectric polarization different with c-axis oriented Bi₂WO₆thin film.Which supposed to possess infinite potential of applications and many intriguing physics properties need to explore.