Polarization Switching Ability Dependent on Multidomain Topology in a Uniaxial Organic Ferroelectric

Abstract

The switching of electric polarization induced by electric fields, a fundamental functionality of ferroelectrics, is closely associated with the motions of the domain walls that separate regions with distinct polarization directions. Therefore, understanding domain-walls dynamics is of essential importance for advancing ferroelectric applications. In this Letter, we show that the topology of the multidomain structure can have an intrinsic impact on the degree of switchable polarization. Using a combination of polarization hysteresis measurements and piezoresponse force microscopy on a uniaxial organic ferroelectric, α-6,6′-dimethyl-2,2′-bipyridinium chloranilate, we found that the head-to-head (or tail-to-tail) charged domain walls are strongly pinned and thus impede the switching process; in contrast, if the charged domain walls are replaced with electrically neutral antiparallel domain walls, bulk polarization switching is achieved. Our findings suggest that manipulation of the multidomain topology can potentially control the switchable polarization.

Tip-induced domain structures and polarization switching in ferroelectric amino acid glycine

“…These thermodynamically stable domains may not be easily switched under an applied electric field and thus the macroscopic remanent polarization can be reduced as compared to the single domain state. 18 The distinct feature of our b-glycine microcrystals is a presence of a large number of charged domain walls (either head-to-head or tail-to-tail). In uniaxial ferroelectrics, 180 domain walls typically separate antiparallel domains with polarization vector parallel to domain plane, so as to avoid high electrostatic energy associated with polarization discontinuity at the domain wall.…”

“…The combination of both represents a typical step-like domain structure similar to that recently observed in a-6,6 0 -dimethyl-2,2 0 -bipiridinium chloranilate. 18 Figure 2 shows a part of the step-like domain structure overlaid on the 3D topography image. It clearly indicates that the 180 domains are mostly coincident with the cleavage planes of the crystal.…”

“…19 Consequently, charged domain walls have been rarely observed in ferroelectric materials, e.g., in PbTiO 3 crystals, 20 in PZT thin films 21 and, recently, in uniaxial organic ferroelectrics. 18 An as-grown glycine crystal has both antiparallel (neutral) and charged ferroelectric domain walls appearing as a series of steps as shown schematically in Fig. 3.…”

Coplanar switching of polarization in thin films of vinylidene fluoride oligomers

“…In our case, application of an external (coplanar) electric field removes the charged domain walls; however, the compensating charges (in the bulk) still reside at the same locations as before usually at the grain boundaries (see the inset in Fig. 5), and therefore produce large internal fields, 32 triggering the relaxation of the electrically induced single-domain-states back to the as-grown domain state. Moreover, the observed relaxation is likely aided by incomplete screening of polarization at the coplanar metal electrodes because of poorly defined metal/ferroelectric interface and non-uniform film coverage.…”

“…For charged domain walls to exist, the bound charges in the bulk associated with discontinuity of polarization should be effectively screened by the mobile charges and/or immobile charged defects. Recent observations 27,32 suggest the existence of stable as-grown charged (head-to-head and tail-to-tail) domain wall configurations in organic ferroelectrics with origin of compensating screening charges yet to be understood. In our case, application of an external (coplanar) electric field removes the charged domain walls; however, the compensating charges (in the bulk) still reside at the same locations as before usually at the grain boundaries (see the inset in Fig.…”