|Linear and Nonlinear Dielectric Microscopy|
We have developed a near-field scanning microwave microscope to quantitatively image the dielectric permittivity and tunability of thin-film dielectric samples on a length scale of 1 µm (papers 72, 76, 100, 114, 119). We have demonstrated this technique with permittivity images and local hysteresis loops of a Ba0.6Sr0.4TiO3 thin film at 7.2 GHz. We also observe the role of annealing in the recovery of dielectric tunability in a damaged region of the thin film. We can measure changes in relative permittivity er as small as 2 at er = 500, and changes in dielectric tunability der/dV as small as 0.03 V-1.
We have developed a new method to image ferroelectric domains with high spatial resolution (papers 76, 84, 114). 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.
This work is supported by the National Science Foundation and the Maryland Center for Nanophysics and Advanced Materials. Additional support comes from the Maryland Industrial Partnerships Program.
Some relevant papers: (All papers can be downloaded from the full publication list)
72. 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).
76. 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. Ins t rum. 71, 2751-2758 (2000).
84. David E. Steinhauer and Steven M. Anlage, "Microwave Frequency Ferroelectric Domain Imaging of Deuterated Triglycine Sulfate Crystals," J. Appl. Phys. 89, 2314-2321 (2001).
100. Alexander Tselev , Charles M. Brooks, Haimei Zheng , Lourdes Salamanca-Riba , Steven M. Anlage, R. Ramesh , and M. A. Subramarian, “Evidence for power-law frequency dependence of intrinsic dielectric response in the CaCu3Ti4O12, ” Physical Review B 70, 144101 (2004). pdf
114. Steven M. Anlage, Vladimir V. Talanov, Andrew R. Schwartz, "Principles of Near-Field Microwave Microscopy," in Scanning Probe Microscopy: Electrical and Electromechanical Phenomena at the Nanoscale, Volume 1, edited by S. V. Kalinin and A. Gruverman (Springer-Verlag, New York, 2007, ISBN: 978-0-387-28667-9 ), pages 215-253. pdf
119. Yi Qi , Steven M. Anlage, H. Zheng, R. Ramesh, “Local Dielectric Measurements of BaTiO3-CoFe2O4 Nano-composites Through Microwave Microscopy,” J. Mat. Res. 22 , 1193-1199 (2007). pdf DOI : 10.1557/JMR.2007.0174
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