Ferroelectric Domain Imaging with a Scanning Near-Field Microwave Microscope

We have developed a new method to image ferroelectric domains with high spatial resolution. The technique makes use of a scanning near-field microwave microscope and exploits the nonlinear dielectric response of the ferroelectrics to image the polarization direction normal to the surface. We validated this technique through measurements of domains in periodically poled Lithium Niobate. We used the microscope to image the formation of domains in Deuterated Tri-Glycine Sulfate (DTGS) as it was cooled below its Curie temperature. Coarsening of the ferroelectric domains was observed by repeatedly imaging the same area of the sample.

Domain imaging is achieved by exploiting the effects of the internal depolarization field on the nonlinear microwave dielectric response of the material as shown in the upper right of the figure. Images are shown of two sides of a periodically-poled Lithium Niobate crystal. Note that the domain direction is reversed upon imaging opposite sides of the crystal, as expected.

This shows a sequence of polarization images of a single 40 μm by 40 μm area of a DTGS crystal. The crystal shows no domain structure at 380 K, above its Curie (ferroelectric ordering) temperature. Upon quenching to below the Curie temperature, the domains grow as long narrow stripes. Eventually the domains become well-defined and the polarization in them increases in magnitude. This process is called domain coarsening.

This shows a sequence of polarization images of a single 100 μm by 100 μm area of a DTGS crystal. The crystal has been quenched to below the Curie temperature, and the domains grow as long narrow stripes. Eventually a single domain orientation takes over the entire image area in this case.

Further details about this work can be found in the following references:

David E. Steinhauer and Steven M. Anlage, "Microwave Frequency Ferroelectric Domain Imaging of Deuterated Triglycine Sulfate Crystals," J. Appl. Phys. 89, 2314-2321 (2001).

D. E. Steinhauer, C. P. Vlahacos, F. C. Wellstood, Steven M. Anlage, C. Canedy, R. Ramesh, A. Stanishevsky, and J. Melngailis, "Quantitative Imaging of Dielectric Permittivity and Tunability with a Near-Field Scanning Microwave Microscope," Rev. Sci. Instrum. 71, 2751-2758 (2000) . cond-mat/0004439.

D. E. Steinhauer, C. P. Vlahacos, C. Canedy, A. Stanishevsky, J. Melngailis, R. Ramesh, F. C. Wellstood, and Steven M. Anlage, "Imaging of Microwave Permittivity, Tunability, and Damage Recovery in (Ba,Sr)TiO3 Thin Films," Appl. Phys. Lett. 75, 3180-3182 (1999). cond-mat/9910014.

This work is supported by the NSF Materials Research Science and Engineering Center at the University of Maryland. Additional support comes from the Maryland Industrial Partnerships Program and Neocera, Inc.

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