Organic Ferroelectric Vortex–Antivortex Domain Structure

Organic ferroelectrics are attracting
tremendous interest because
of their mechanical flexibility, ease of fabrication, and low acoustical
impedance. Although great advances have been made in recent years,
topological defects such as vortices remain relatively unexplored
in the organic ferroelectric system. Here, from [quinuclidinium]­ReO4 ([Q]­ReO4), we applied the molecular design strategy
of H/F substitution to successfully synthesize the organic ferroelectric
[4-fluoroquinuclidinium]­ReO4 ([4-F-Q]­ReO4).
Through H/F substitution, the Curie temperature and spontaneous polarization
are respectively increased from 367 K and 5.83 μC/cm2 in [Q]­ReO4 to 466 K and 11.37 μC/cm2 in [4-F-Q]­ReO4. Moreover, under mechanical stress fields,
three kinds of stripelike domains with various polarization directions
emerge to form a windmill-like domain pattern in the thin film of
[4-F-Q]­ReO4, in which intriguing vortex–antivortex
topological configurations can exist stably. This work provides an
efficient strategy for optimizing the properties of organic ferroelectrics
and exploring emergent phenomena.