Simulation Analysis of Effect of Vacancies on Ferroic Domain Growth of BaTiO^3

BaTiO3 is one of the well-known ferroelectric and piezoelectric materials, which has been widely used in various devices. However, the microscopic mechanism of the ferroelectric domain growth is not understood well. We investigated the effects of point defects, mono- and di-vacancies of Ba, Ti, and O, on the domain growth of BaTiO3 using molecular dynamics simulation with the core-shell inter-atomic potential. We found the following: ｓ(1) One kind of monovacancy, VO1, located on the TiO plane perpendicular to the applied electric field direction, acts to hinder the polarization inversion induced by the applied electric field. The monopole electric field produced by VO1 either hinders or assists the local polarization inversion in accordance with the local intensity of the total electric field. (2) The 1st-neighbor divacancies VBa-VO and VTi-VO as compared to the 2nd-neighbor divacancies asymmetrically affect the domain growth with respect to the applied electric field, making the hysteresis behavior of applied electric field vs. polarization relation. The domain grows even at a small electric field when the directions of the applied electric field and the divacancy dipole are mutually the same. (3) The domain growth speed towards the applied electric field direction is about 2 orders of magnitude higher than that towards the perpendicular direction.

SGIP1α, but Not SGIP1, is an Ortholog of FCHo Proteins and Functions as an Endocytic Regulator

Src homology 3-domain growth factor receptor-bound 2-like interacting protein 1 (SGIP1), originally known as a regulator of energy homeostasis, was later found to be an ortholog of Fer/Cip4 homology domain-only (FCHo) proteins and to function during endocytosis. SGIP1α is a longer splicing variant in mouse brains that contains additional regions in the membrane phospholipid-binding domain (MP) and C-terminal region, but functional consequences with or without additional regions between SGIP1 and SGIP1α remain elusive. Moreover, many previous studies have either inadvertently used SGIP1 instead of SGIP1α or used the different isoforms with or without additional regions indiscriminately, resulting in further confusion. Here, we report that the additional region in the MP is essential for SGIP1α to deform membrane into tubules and for homo-oligomerization, and SGIP1, which lacks this region, fails to perform these functions. Moreover, only SGIP1α rescued endocytic defects caused by FCHo knock-down. Thus, our results indicate that SGIP1α, but not SGIP1, is the functional ortholog of FCHos, and SGIP1 and SGIP1α are not functionally redundant. These findings suggest that caution should be taken in interpreting the role of SGIP1 in endocytosis.

Numerical simulation of domain wall motion in a surface discharge over a ferroelectric

The article presents a simplified numerical simulation of a vacuum ferroelectric cathode operating in a low-current mode (without surface plasma formation). The field emission from the cathode was simulated for the range of applied electric field magnitudes. The polarization domain growth process during the charging of ferroelectric surface was simulated using Landau-Ginzburg-Devonshire model. Interaction of the electrons with a depolarization field of a domain wall led to an attraction of the electrons to the polarization domain boundaries. A close to the linear dependence of the equilibrium domain wall position from the applied electric field was found with the total emitted charge proportional to the domain size.

Non-Invasive Visualization of Ferroelectric Domain Structures on the Non-Polar y-Surface of KTiOPO4 via Raman Imaging

Potassium titanyl phosphate (KTP) is a nonlinear optical material with applications in high-power frequency conversion or quasi-phase matching in submicron period domain grids. A prerequisite for these applications is a precise control and understanding of the poling mechanisms to enable the fabrication of high-grade domain grids. In contrast to the widely used material lithium niobate, the domain growth in KTP is less studied, because many standard methods, such as selective etching or polarization microscopy, provides less insight or are not applicable on non-polar surfaces, respectively. In this work, we present results of confocal Raman-spectroscopy of the ferroelectric domain structure in KTP. This analytical method allows for the visualization of domain grids of the non-polar KTP y-face and therefore more insight into the domain-growth and -structure in KTP, which can be used for improved domain fabrication.