Unit-cell scale mapping of ferroelectricity and tetragonality in epitaxial ultrathin ferroelectric films
Publication Type | Journal Article
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Authors | |
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DOI |
10.1038/nmat1808
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Abstract |
Typically, polarization and strain in ferroelectric materials are coupled, leading to the generally accepted direct relation between polarization and unit-cell tetragonality. Here, by means of high-resolution transmission electron microscopy we map, on the unit-cell scale, the degree of tetragonality and the displacements of cations away from the centrosymmetry positions in an ultrathin epitaxial PbZr"0"."2Ti"0"."8O"3 film on a SrRuO"3 electrode layer deposited on a SrTiO"3 substrate. The lattice is highly tetragonal at the centre of the film, whereas it shows reduced tetragonality close to the interfaces. Most strikingly, we find that the maximum off-centre displacements for the central area of the film do not scale with the tetragonality. This challenges the fundamental belief in a strong polarization-tetragonality coupling in PbTiO"3-based ferroelectrics, at such thicknesses. Furthermore, a systematic reduction of the atomic displacements is measured at the interfaces, suggesting that interface-induced suppression of the ferroelectric polarization plays a critical role in the size effect of nanoscale ferroelectrics. © 2007 Nature Publishing Group.
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Notes |
cited By 266
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Journal |
Nature Materials
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Volume |
6
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Year of Publication |
2007
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Number |
1
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Pagination |
64-69
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Publisher |
Nature Publishing Group
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ISSN Number |
14761122
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Keywords | |
Research Areas | |
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