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2005 Nuggets
High Aspect Ratio Structures in Complex Materials
S. S. N. Bharadwaja, X. Li,D. J. won, H. Fang, V. Gopalan, T. Mayer, T. N. Jackson, and S. Trolier-McKinstry,IRG1
Mold replication is being used to make high aspect ratio structures in multicomponent
ferroelectrics like lead zirconate titanate (PZT). Hollow PZT tubes are fabricated by infiltration of
microporous Si templates (provided by collaborators at Philips Research) with diameters that
range from 1 - 3 µm, and lengths up to 50 µm. After infiltration the samples are pyrolyzed, the
mold is removed, and the electroceramic is crystallized. LaNiO3/PZT/LaNiO3 tubes with
excellent perovskite phase purity have also been prepared. During the past year, efforts have
been devoted to improving the crystalline quality of the tubes, demonstrating that the tube array
can act as a photonic band gap, and developing a strategy for integrating individual micron
diameter Pb(Zrx,Ti1-x)O3 tubes into interdigitated and core-shell structures to characterize their
dielectric properties. The aspect ratios that can be achieved by this approach are much larger than
would be possible with a more conventional processing approach such as deep reactive ion
etching. The result is that it is possible to use these structures as photonic band gap materials
(with the potential for tunability), as well as high frequency-high resolution ultrasonic imaging
arrays. Work is currently on-going to explore both of these possibilities.
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