Ferroelastic domain wall dynamics in ferroelectric bilayers

Abstract

High-performance piezoelectric devices based on ferroelectric materials rely heavily on ferroelastic domain wall switching. Here we present visual evidence for the local mechanisms that underpin domain wall dynamics in ferroelastic nanodomains. State-of-the-art band excitation switching spectroscopy piezoforce microscopy (PFM) reveals distinct origins for the reversible and irreversible components of ferroelastic domain motion. Extrapolating the PFM images to case for uniform fields, we posit that, while reversible switching is essentially a linear motion of the ferroelastic domains, irreversible switching takes place via domain wall twists. Critically, real-time images of in situ domain dynamics under an external bias reveal that the reversible component leads to reduced coercive voltages. Finally, we show that junctions representing three-domain architecture represent facile interfaces for ferroelastic domain switching, and are likely responsible for irreversible processes in the uniform fields. The results presented here thus provide (hitherto missing) fundamental insight into the correlations between the physical mechanisms that govern ferroelastic domain behavior and the observed functional response in domain-engineered thin film ferroelectric devices.

Domain Wall Conduction and Polarization‐Mediated Transport in Ferroelectrics

“…Finally, phase field allows for dynamic effect to be explored. For vortex and wall the dominant mode of evolution is the twist of the in‐plane polarization component, in agreement with previous studies 108, 187, 197, 207. The dynamics can be parameterized by voltage dependence of average (through thickness) polarization and average potential.…”

“…The long‐range influence of the domain wall on local switching is thought to be from local bending or bowing of the domain wall under applied field. A similar observation was reported in PZT thin films where the presence of a ferroelastic domain wall critically reduced the nucleation bias 108…”

Domain-reorientation-induced polarization wake-up of PbTiO3 based ferroelectric thin films

“…1(c) and (g)) piezoresponse force images correspond to vertical PFM (VPFM) and lateral PFM (LPFM) patterns, respectively. The bright (white) and the dark (yellow) contrast in the amplitude and the phase PFM images represent the orientation of the polarization vector [26,27]. Both amplitude and phase LPFM images show a strong contrast, while the VPFM images show a poor contrast at the same region.…”

Dynamic Control of Thermal Transport via Phonon Scattering at Ferroelastic Domain Walls

“…We also point out that the thermal conductivities of the BiFeO 3 films are most likely affected by size effects due to the thin film geometry; that is, phonon scattering at the film boundaries of the BiFeO 3 can cause a reduction in the thermal conductivity of the films as compared to a thicker or "bulk" sample. [27][28][29] However, since all samples are 30 nm, the finite size of the sample has the same effect in all of the films, therefore, highlighting the domain wall effects on thermal transport in BiFeO 3 .…”

“…(c) Plan-view SEM image os the 1x1 bilayer heterostructure, illustrating the anomalously large grain sizes and complex, ultra-fine ferroelastic domain structure of these bilayers. [12,27,28] . .…”