Effect of ferroelectric domain walls on the dielectric properties of PbZrO3 thin films

We review dielectric properties of BaZrO3/BaTiO3 (BZ/BT) superlattices deposited on a single-crystal MgO substrate, and having a period of 13.32 nm. These superlattices have specific properties distinguishing them from BZ or BT bulk materials, and from thin films, with a ferroelectric phase transition around 393-395 °?, significantly higher than in bulk samples and thin films of BT, and appearing of second order. The polarization switching occurs in two stages and the precise analysis of experimental data demonstrates that the motion of the domain walls causes the switching processes. We conclude that the mobility of the domain walls decreases on heating. The presence of an internal bias field has been demonstrated and shown to be directed from the superlattice to the substrate, in agreement with an analysis based on the flexoelectric effect. The switching current has been shown to vary in weak fields as 1/E? with the exponent ? much smaller than in thin ferroelectric films. The appearance of the power index ?, which is significantly different from unity, may be due to a decrease in the average value of the switched polarization due to the boundaries between layers of different materials.

Download Full-text

Electron Holographic Characterization of Ferroelectric Thin Films

MRS Proceedings ◽

10.1557/proc-284-487 ◽

1992 ◽

Vol 284 ◽

Author(s):

Xiao Zhang ◽

David C. Joy

Keyword(s):

Thin Films ◽

Domain Wall ◽

Domain Walls ◽

Ferroelectric Domain ◽

Electron Holography ◽

Contrast Imaging ◽

Thin Specimen ◽

Wall Width ◽

Domain Wall Width

ABSTRACTIn this paper we will present recent experimental results, using electron holography and electron interferometry, of studies of ferroelectric domain walls in BaTiO3 thin films. Unlike conventional TEM diffraction contrast imaging of ferroelectrics, the new technique that we have developed not only allows direct visualization of ferroelectric domain walls and electrostatic field distributions in the vicinity of the domain wall, but also enables quantitative measurement of domain wall width and local polarization. We have measured 90° domain wall width to be between 20 to 50 Å for a BaTiO3 thin specimen. The variation of polarization across the domain wall will be shown to be close to that predicted by the Zhirnov model. The value of the measured spontaneous polarization is about 1.5×10−5 C/cm2, which is closed to the bulk macroscopically measured value.

Download Full-text

Imaging of ferroelectric domain walls by electron holography

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121636 ◽

1992 ◽

Vol 50 (1) ◽

pp. 246-247

Author(s):

Xiao Zhang

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Domain Walls ◽

Ferroelectric Domain ◽

Object Wave ◽

Electron Holography ◽

High Resolution Imaging ◽

Quantitative Measurements ◽

Resolution Imaging ◽

Electron Microscopes

Electron holography has recently been available to modern electron microscopy labs with the development of field emission electron microscopes. The unique advantage of recording both amplitude and phase of the object wave makes electron holography a effective tool to study electron optical phase objects. The visibility of the phase shifts of the object wave makes it possible to directly image the distributions of an electric or a magnetic field at high resolution. This work presents preliminary results of first high resolution imaging of ferroelectric domain walls by electron holography in BaTiO3 and quantitative measurements of electrostatic field distribution across domain walls.

Download Full-text