Anomalous Motion of Charged Domain Walls and Associated Negative Capacitance in Copper–Chlorine Boracite

Joseph G. M. Guy, Charlotte Cochard, Pablo Aguado-Puente, Elisabeth Soergel, Roger W. Whatmore, Michele Conroy, Kalani Moore, Eileen Courtney, Alan Harvey, Ursel Bangert, Amit Kumar, Raymond G. P. McQuaid, J. Marty Gregg (Lead / Corresponding author)

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Abstract

During switching, the microstructure of a ferroelectric normally adapts to align internal dipoles with external electric fields. Favorably oriented dipolar regions (domains) grow at the expense of those in unfavorable orientations and this is manifested in a predictable field-induced motion of the walls that separate one domain from the next. Here, the discovery that specific charged 90°domain walls in copper–chlorine boracite move in the opposite direction to that expected, increasing the size of the domain in which polarization is anti-aligned with the applied field, is reported. Polarization–field (P–E) hysteresis loops, inferred from optical imaging, show negative gradients and non-transient negative capacitance, throughout the P–E cycle. Switching currents (generated by the relative motion between domain walls and sensing electrodes) confirm this, insofar as their signs are opposite to those expected conventionally. For any given bias, the integrated switching charge due to this anomalous wall motion is directly proportional to time, indicating that the magnitude of the negative capacitance component should be inversely related to frequency. This passes Jonscher's test for the misinterpretation of positive inductance and gives confidence that field-induced motion of these specific charged domain walls generates a measurable negative capacitance contribution to the overall dielectric response.

Original languageEnglish
Article number2008068
Number of pages10
JournalAdvanced Materials
Early online date18 Mar 2021
DOIs
Publication statusE-pub ahead of print - 18 Mar 2021

Keywords

  • boracites
  • domain walls
  • negative capacitance

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