Mechanical-force-induced non-local collective ferroelastic switching in epitaxial lead-titanate thin films

Abstract

Ferroelastic switching in ferroelectric/multiferroic oxides plays a crucial role in determining their dielectric, piezoelectric, and magnetoelectric properties. In thin films of these materials, however, substrate clamping is generally thought to limit the electric-field- or mechanical-force-driven responses to the local scale. Here, we report mechanical-force-induced large-area, non-local, collective ferroelastic domain switching in PbTiO 3 epitaxial thin films by tuning the misfit-strain to be near a phase boundary wherein c/a and a 1 / a 2 nanodomains coexist. Phenomenological models suggest that the collective, c - a - c - a ferroelastic switching arises from the small potential barrier between the degenerate domain structures, and the large anisotropy of a and c domains, which collectively generates much larger response and large-area domain propagation. Large-area, non-local response under small stimuli, unlike traditional local response to external field, provides an opportunity of unique response to local stimuli, which has potential for use in high-sensitivity pressure sensors and switches.

Phase transition enhanced superior elasticity in freestanding single-crystalline multiferroic BiFeO 3 membranes

“…The fact that T phase (i.e., c+ domain) only appears at the bottom, which is a highly compressive region, and R phase (i.e., R1+ domain) in the tensile strained region reveals that the polarization orientation (or the phase state) is related to the strain state. Unlike the sharp boundary from the conventional R-T mix-phase observed in the system of the BiFeO 3 film/substrate ( 7 , 18 , 26 , 27 ), the phase boundary between T phase and R phase is a rather thicker transitional region where polarization rotates continuously from c+ domain to R1+ domain, possibly arising from both the relaxed elastic strain to decrease the elastic energy at this specific mechanical boundary and the local flexoelectric field ( 28 – 30 ) from strain gradient for the bending state of the BiFeO 3 film. Also, the magnitude of the polarization increases continuously from the bottom to the top surface along the z axis for all bent cases shown in the left panels of Fig.…”

“…The temporal evolution of P i ( i = 1, 2, 3) in a (001)-oriented BiFeO 3 freestanding film is calculated by numerically solving the time-dependent Ginzburg-Landau equation ( 36 ) where r is the spatial position, L is a kinetic coefficient, and F tot is the total free energy of the BiFeO 3 film, expressed as where V BFO denotes the volume of the BiFeO 3 film and f land , f elect , f grad , f elastic , and f flexo represent the local densities of landau, electrostatic, gradient, elastic, and flexoelectric energies, respectively. The mathematical expressions for the f land , f elect , f grad , and f elastic of the BiFeO 3 film are given in the literature ( 7 , 27 – 30 , 37 ). f flexo can be given as where f ijkl ( i , j , k , l = 1 to 3) denote the flexoelectric coupling coefficients (or flexovoltage coefficients) ( 28 ).…”

“…where V BFO denotes the volume of the BiFeO 3 film and f land , f elect , f grad , f elastic , and f flexo represent the local densities of landau, electrostatic, gradient, elastic, and flexoelectric energies, respectively. The mathematical expressions for the f land , f elect , f grad , and f elastic of the BiFeO 3 film are given in the literature (7,(27)(28)(29)(30)37). f flexo can be given as…”

Subthreshold Characteristics of a Metal-Oxide–Semiconductor Field-Effect Transistor with External PVDF Gate Capacitance

“…At least two different approaches have been proposed: (1) to use the tunnel junction at the source/channel end of the MOSFET (called the tunnel field-effect transistor or tunnel FET) [11][12][13][14]; and (2) to use the negative gate capacitance of the MOSFET. Negative capacitance has been observed in many different materials and device structures including ferroelastic switches, oxidesuperlattices, supercrystals, and light-emitting diodes [15][16][17][18][19][20][21]. It can be practically achieved by utilizing ferroelectric dielectric materials such as AlInN [8], BiFeO 3 [9], and HfZrO 2 [14], due to the lag of the polarization charge inside the ferroelectric materials with respect to the change of applied voltage.…”

Toppling dynamics of a mass-varying domino system

“…Domino phenomenon is usually used to describe the cumulative effect in a marginally stable system when one event sets off a chain of similar events, such as the wave propagation in earthquake [1,2], the transitions within a cell cycle [3], the collapsing of carbon nanotube [4,5], the ruck in a rug [6,7], nuclear and chemical reactions [8,9], energy transmission in meta-material [10][11][12][13][14], and the chain effect in economics and sociology [15,16]. These phenomena can be physically represented by the domino falling problem [17], i.e., a group of regularly spaced dominoes fall down one by one if an initial push is given leading to a domino wave.…”