Abstract
The improper ferroelectric CsNbW2O9 has recently been highlighted as the first material outside the manganite family to exhibit a similar meandering, sixfold domain structure to that responsible for enhanced and diminished conduction at charged domain walls in the rare earth manganites. While there is no current evidence for variation in domain wall conduction relative to bulk in CsNbW2O9, the similarities in microstructure strongly suggest that charged domain walls are present in this material. Herein, we report a comprehensive study of the domain microstructure of CsNbW2O9 by both piezoresponse force microscopy and transmission electron microscopy to reveal that there are, in fact, clear distinctions in the domain structure of the two systems. Constraints arising from the crystal structure of CsNbW2O9, namely, the connectivity of the BO6 polyhedra and atomic displacements occurring purely along the c axis, mean that domain walls preferentially run parallel to the c direction (the polar axis of the material) and thus remain uncharged. The characteristic cloverleaf domain structure reminiscent of the manganites is still present; however, the structure meanders predominantly in the ab plane and, therefore, appears differently depending on the projection direction from which it is viewed. As a result of this microstructural constraint, charged domain walls are not prevalent in this material.
Highlights
In recent years, ferroelectrics research has undergone a dramatic shift in focus, which has led to the development of a new field in its own right
We report a comprehensive study of the domain microstructure of CsNbW2O9 by both piezoresponse force microscopy and transmission electron microscopy to reveal that there are, clear distinctions in the domain structure of the two systems
Lateral piezoresponse force microscopy (PFM) (LPFM) images acquired at various sample orientations are displayed in Figs. 2(a)–2(d), where the relative orientation of the cantilever body and hypothesized polar axis are indicated for each scan by the cartoons alongside
Summary
Ferroelectrics research has undergone a dramatic shift in focus, which has led to the development of a new field in its own right. The conductivity can vary by up to 14 orders of magnitude between a charged and neutral wall.[4] Since their discovery, charged conducting domain walls have been observed in an abundance of ferroelectric materials, such as BiFeO3,5 LiNbO3,6 BaTiO3,7 (Ca, Sr)3Ti2O7,8 Cu3B7O13Cl,[9] and RMnO3 (R = Sc, Y, Dy–Lu).[10] With a wealth of discoveries, the field of domain wall nanoelectronics was established—a possible avenue for device miniaturization to continue in accordance with Moore’s law, using completely new device paradigms Such ideas have already come to fruition with the development of domain wall diode and tunnel junction devices.[11,12,13] To date, the hexagonal rare-earth manganites (RMnO3)
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