Morphological Control of Polar Orientation in Single-Crystal Ferroelectric Nanowires

In an attempt to explore and understand domain configurations that occur in idealized ferroelectric nanowires, a focused ion beam microscope has been used to directly cut columns in a variety of sizes from single-crystal barium titanate. The scanning transmission electron microscope has then been us...

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Bibliographic Details
Published in:Nano letters 2007-12, Vol.7 (12), p.3787-3791
Main Authors: Schilling, A, Bowman, R. M, Catalan, G, Scott, J. F, Gregg, J. M
Format: Article
Language:English
Subjects:
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Dielectric, piezoelectric, ferroelectric and antiferroelectric materials
Dielectrics, piezoelectrics, and ferroelectrics and their properties
Exact sciences and technology
Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties
Materials science
Nanocrystalline materials
Nanoscale materials and structures: fabrication and characterization
Physics
Surfaces and interfaces
thin films and whiskers (structure and nonelectronic properties)
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Summary:In an attempt to explore and understand domain configurations that occur in idealized ferroelectric nanowires, a focused ion beam microscope has been used to directly cut columns in a variety of sizes from single-crystal barium titanate. The scanning transmission electron microscope has then been used to image the ferroelectric domain patterns evident after cooling through the Curie temperature in the vacuum environment of the electron microscope. As the overall length of the wires is physically constrained, the observed length-conserving packets of 90° domains with {110}pseudocubic domain-wall orientations can easily be rationalized. Such domain structures necessarily dictate that although half of the domains can be such that their polarization direction lies parallel to the axis of the wire, the other half of the domains will have polarization directions approximately perpendicular to the wire axis (nonaxial). This situation introduces a depolarizing field and associated energy, which is minimized when the nonaxial polarization is oriented perpendicular to the smallest dimension of the column. Locally changing the aspect ratio of the column dimensions therefore allows local variations in the direction of polarization to be introduced. This was demonstrated by fabricating wire structures in which dimensions were varied along their length. Such wires did indeed show morphologically controlled polar reorientation. The study suggests that shape engineering alone could be used to create complex heterogeneous dipole configurations in ferroelectrics at the nanoscale without the need for externally applied poling electric fields. Possibilities for the further development of this observation might include introducing chiral variations in wire thickness, for example, to create dipole helices.
ISSN:1530-6984
1530-6992
DOI:10.1021/nl072260l