Field Modulation Imaging of Polarization Domain Dynamics in Single-Crystalline Organic Ferroelectric Thin Films at Various Temperatures

Ferroelectrics have switchable spontaneous electric polarization, the feature of which is useful in nonvolatile memories or ferroelectric field-effect transistors. Among a variety of ferroelectric materials, proton-transfer-type organic ferroelectrics [1] are promising as key materials in flexible printed electronics due to the processability at ambient conditions. However, the studies of these materials are limited, because the ferroelectric domain dynamics as well as film fabrication methods have been unknown.
Here report a new noncontact method to visualize the ferroelectric domain structures over a wide area of ferroelectric films using CMOS image sensors. We call the technique as “ferroelectrics field modulation imaging (FFMI)”, in which the polarization domains can be visualized by detecting the change of optical absorption induced by applied ac electric fields. We demonstrate that the polarization domains are visualized in single-crystal thin films of [Hdppz][Hca], a proton-transfer-type organic ferroelectrics [1], at various temperatures. We show that the domain-wall motion is more suppressed in thin films by possible large potential barriers than in bulk crystals, based on the Arrhenius analyses of the measurements.
[1] S. Horiuchi et al. JACS 135, 4492 (2013).