Domain fluctuations in a ferroelectric low-strain BaTiO3 thin film

Abstract

A ferroelectric BaTiO 3 thin film grown on a NdScO 3 substrate was studied using x-ray photon correlation spectroscopy (XPCS) to characterize thermal fluctuations near the a/b to a/c domain structure transformation present in this low-strain material, which is absent in the bulk. XPCS studies provide a direct comparison of the role of domain fluctuations in first-and second-order phase transformations. The a/b to a/c domain transformation is accompanied by a decrease in fluctuation timescales, and an increase in intensity and correlation length. Surprisingly, domain fluctuations are observed up to 25°C above the transformation, concomitant with the growth of a/c domains and coexistence of both domain types. After a small window of stability, as the Curie temperature is approached, a/c domain fluctuations are observed, albeit slower, potentially due to the structural transformation associated with the ferroelectric to paraelectric transformation. The observed time evolution and reconfiguration of domain patterns highlight the role played by phase coexistence and elastic boundary conditions in altering fluctuation timescales in ferroelectric thin films.

Interplay of domain structure and phase transitions: theory, experiment and functionality

“…Domain wall properties: in addition to the impact of phase transitions on domain spacing, also the wall properties are strongly modified in the vicinity of a phase boundary. First of all, enhanced fluctuations of domain walls (with time) occur close to transitions as, e.g., observed by x-ray photon correlation spectroscopy at the a 1 /a 2 to a/c transition and the FE to paraelectric transition in strained BaTiO 3 films [26]. This has been related to the complex energy landscape and phase coexistence.…”

“…Analogous to temperature driven transitions between different 'phases' these transitions may show a broad coexistence range with large dielectric and piezoelectric responses [25]. Furthermore, first-order thermotropic transitions between different domain structures in strained films have been observed [26].…”

Dynamic Tilting of Ferroelectric Domain Walls Caused by Optically Induced Electronic Screening

“…The a à component is predicted to exhibit a 180°rotation at the a=c domain wall. Temperature-dependent x-ray diffraction measurements described in the Supplemental Material and piezoelectric force microscopy both indicate that a=c and a=b phases coexist over a temperature range of tens of degrees below 340 K [18,19]. At 298 K, the majority of the volume of the BTO film is in the a=b phase.…”

Ultrafast Bragg coherent diffraction imaging of epitaxial thin films using deep complex-valued neural networks

“…Specifically, we employed a complex-valued convolutional neural network (C-CNN) to recover the complex-valued images from the corresponding coherent diffraction patterns in reciprocal space. For experimental coherent diffraction data, we chose to look at an LSCO sample with x ¼ 0:07 for which the HTT-LTO phase transition lies around T s ¼ 330K with an XFEL source, because there might be associated critical fluctuations reported in the previous work 31,32 . Therefore, the sample was measured on a vibration-free Peltier stage as a function of temperature near 330K.…”