TY - JOUR
T1 - Anomalous Motion of Charged Domain Walls and Associated Negative Capacitance in Copper–Chlorine Boracite
AU - Guy, Joseph G. M.
AU - Cochard, Charlotte
AU - Aguado-Puente, Pablo
AU - Soergel, Elisabeth
AU - Whatmore, Roger W.
AU - Conroy, Michele
AU - Moore, Kalani
AU - Courtney, Eileen
AU - Harvey, Alan
AU - Bangert, Ursel
AU - Kumar, Amit
AU - McQuaid, Raymond G. P.
AU - Gregg, J. Marty
N1 - Funding Information:
The assistance of C. J. Brierley at Plessey Research (Caswell) Ltd. in growing the boracite crystals is gratefully acknowledged, as is the assistance of J. P. V. McConville in discussing transmission electron microscopy data. The authors thank Prof. M. A. Carpenter and Dr. C. M. Fernandez‐Posada for their invaluable help with the derivation of Landau potentials. Exploratory phase field modeling of the data performed by J. Hu and S. Zhuang (University of Wisconsin) is gratefully recognized. The authors acknowledge funding from the Engineering and Physical Sciences Research Council (EPSRC: EP/P02453X/1; EP/P020194/1), the US‐Ireland Research and Development Partnership Programme (USI 120), the Science Foundation Ireland (SFI: 16/US/3344 and 18/IF/6282) and the joint Department for Employment‐Science Foundation Ireland programme (15/IA/3160).
Publisher Copyright:
© 2021 The Authors. Advanced Materials published by Wiley-VCH GmbH
PY - 2021/4/22
Y1 - 2021/4/22
N2 - 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.
AB - 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.
KW - boracites
KW - domain walls
KW - negative capacitance
UR - http://www.scopus.com/inward/record.url?scp=85102653150&partnerID=8YFLogxK
U2 - 10.1002/adma.202008068
DO - 10.1002/adma.202008068
M3 - Article
C2 - 33734520
AN - SCOPUS:85102653150
VL - 33
JO - Journal of Optoelectronics and Advanced Materials
JF - Journal of Optoelectronics and Advanced Materials
SN - 1454-4164
IS - 16
M1 - 2008068
ER -