Nanoscale Activation Energy Mapping and Leveraging for Accelerating Ferroelectric Domain Nucleation and Growth

Abstract

The dynamics of ferroelectric domain switching are directly mapped in a PbZr0.2Ti0.8O3 thin film using piezoresponse force microscopy. Employing the rastering tip as a poling electrode to locally apply a fixed bias near the coercive field, while simultaneously monitoring the evolving domain pattern during continuous imaging, the effectively independent switching dynamics for numerous domains are directly investigated. While areal poling follows the anticipated S‐curve, this is shown to be the collective outcome of linear terminal radial growth for an ensemble of independently nucleating domains. By repeating such spatially resolved measurements in the same region, but with progressively greater fields, nucleation sites and growth patterns are shown to clearly repeat. This reveals apparent defects which comparatively promote switching, and nucleation times and growth rates that accelerate exponentially. After analyzing and mapping the ratio of activation energies for nucleation to growth, a high density of nucleation sites can possibly be activated with higher poling fields—even if only at the start of a poling process—enabling faster and more efficient switching to be engineered as directly demonstrated.

Anomalously abrupt switching of wurtzite-structured ferroelectrics: simultaneous non-linear nucleation and growth model

“…Recent work from Nath et al reported n 4 4 values for select regions of epitaxial PZT thin films via scanning probe and connected the large n values with a lack of existing nucleation sites, but further mechanistic discussion was limited. 25 The extended model demonstrated in this work rationalizes the phenomena of such rapid transitions via characteristic nucleation and growth times and is also applicable to the nucleation-growth mechanism in crystallization processes beyond ferroelectric switching.…”

“…3a and b), conceptually consistent with Merz's law 46 and in a manner similar to comparable studies on perovskite oxide ferroelectric thin films. 19,25,47 In addition to the shift, the slope of the polarization increase steepens with increasing applied electric field for both materials. This slope change is also seen in conventional ferroelectrics, 19,47 though only the recent study from Nath, et al , has reported n values >3.…”

“…This slope change is also seen in conventional ferroelectrics, 19,47 though only the recent study from Nath, et al, has reported n values 43. 25 In contrast, the KAI fitted Avrami exponents of Al 0.7 Sc 0.3 N and Al 0.94 B 0.06 N films reach 7 and 11, respectively, at high electric fields (Fig. 2c, d).…”

“…1b. Several scanning probe studies 15,22–25 have reported time-varying nucleation rates inconsistent with Ishibashi's assumptions, but no work has yet addressed the scenario shown in Fig. 1c in which significant growth occurs prior to and throughout a peak in nucleation rate.…”

“…As Cahn noted in his classic rederivation, 26 the JMAK model itself has no restrictions against time-varying nucleation and growth rates, but n is often overinterpreted as necessarily being equal to either the dimensionality of growth ( n = D ) or one plus the dimensionality of growth ( n = 1 + D ). A decaying nucleation rate following the Jacobs–Thompkins equation 27 has been shown to be consistent with a mixed scenario ( D ≤ n ≤ 1 + D ) and is commonly applied to solid state chemistry and crystal growth, 28,29 but examples requiring a more nuanced description of nucleation contributions have been limited, 25,30–33 such that the D ≤ n ≤ 1 + D interpretation is pervasive. Elaboration of nucleation and growth kinetics beyond D ≤ n ≤ 1 + D is required to capture the scenario shown in Fig.…”