Browse
Submit Data
Databases
API
Help

Dataset Information

24 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

The ultrathin limit of improper ferroelectricity.

ABSTRACT: The secondary nature of polarization in improper ferroelectrics promotes functional properties beyond those of conventional ferroelectrics. In technologically relevant ultrathin films, however, the improper ferroelectric behavior remains largely unexplored. Here, we probe the emergence of the coupled improper polarization and primary distortive order parameter in thin films of hexagonal YMnO₃. Combining state-of-the-art in situ characterization techniques separately addressing the improper ferroelectric state and its distortive driving force, we reveal a pronounced thickness dependence of the improper polarization, which we show to originate from the strong modification of the primary order at epitaxial interfaces. Nanoscale confinement effects on the primary order parameter reduce the temperature of the phase transition, which we exploit to visualize its order-disorder character with atomic resolution. Our results advance the understanding of the evolution of improper ferroelectricity within the confinement of ultrathin films, which is essential for their successful implementation in nanoscale applications.

SUBMITTER: Nordlander J

PROVIDER: S-EPMC6897979 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Recipes for improper ferroelectricity in molecular perovskites.

Project description:The central goal of crystal engineering is to control material function via rational design of structure. A particularly successful realisation of this paradigm is hybrid improper ferroelectricity in layered perovskite materials, where layering and cooperative octahedral tilts combine to break inversion symmetry. However, in the parent family of inorganic ABX3 perovskites, symmetry prevents hybrid coupling to polar distortions. Here, we use group-theoretical analysis to uncover a profound enhancement of the number of improper ferroelectric coupling schemes available to molecular perovskites. This enhancement arises because molecular substitution diversifies the range of distortions possible. Not only do our insights rationalise the emergence of polarisation in previously studied materials, but we identify the fundamental importance of molecular degrees of freedom that are straightforwardly controlled from a synthetic viewpoint. We envisage that the crystal design principles we develop here will enable targeted synthesis of a large family of new acentric functional materials.

| S-EPMC6006342 | biostudies-literature

Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes.

Project description:Two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP2S6 (CIPS) with a transition temperature of ∼320 K. Switchable polarization is observed in thin CIPS of ∼4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ∼100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity.

| S-EPMC4987531 | biostudies-literature

Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films.

Project description:We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelectric PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, respectively. Resistance-voltage measurements and AC impedance analysis suggest that at high temperatures Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temperatures and lead to the self-polarization at room temperature with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelectric films and self-polarization mechanism.

| S-EPMC4730210 | biostudies-literature

Momentum-resolved observations of the phonon instability driving geometric improper ferroelectricity in yttrium manganite.

Project description:Magnetoelectrics offer tantalizing opportunities for devices coupling ferroelectricity and magnetism but remain difficult to realize. Breakthrough strategies could circumvent the mutually exclusive origins of magnetism and ferroelectricity by exploiting the interaction of multiple phonon modes in geometric improper and hybrid improper ferroelectrics. Yet, the proposed instability of a zone-boundary phonon mode, driving the emergence of ferroelectricity via coupling to a polar mode, remains to be directly observed. Here, we provide previously missing evidence for this scenario in the archetypal improper ferroelectric, yttrium manganite, through comprehensive scattering measurements of the atomic structure and phonons, supported with first-principles simulations. Our experiments and theoretical modeling resolve the origin of the unusual temperature dependence of the polarization and rule out a reported double-step ferroelectric transition. These results emphasize the critical role of phonon anharmonicity in rationalizing lattice instabilities in improper ferroelectrics and show that including these effects in simulations could facilitate the design of magnetoelectrics.

| S-EPMC5750229 | biostudies-literature

Thermooptical evidence of carrier-stabilized ferroelectricity in ultrathin electrodeless films.

Project description:Ferroelectric films may lose polarization as their thicknesses decrease to a few nanometers because of the depolarizing field that opposes the polarization therein. The depolarizing field is minimized when electrons or ions in the electrodes or the surface/interface layers screen the polarization charge or when peculiar domain configuration is formed. Here, we demonstrate ferroelectric phase transitions using thermooptical studies in ?5-nm-thick epitaxial Pb0.5Sr0.5TiO3 films grown on different insulating substrates. By comparing theoretical modeling and experimental observations, we show that ferroelectricity is stabilized through redistribution of charge carriers (electrons or holes) inside ultrathin films. The related high-density of screening carriers is confined within a few-nanometers-thick layer in the vicinity of the insulator, thus resembling a two-dimensional carrier gas.

| S-EPMC5981214 | biostudies-literature

Optical Imaging of Nonuniform Ferroelectricity and Strain at the Diffraction Limit.

Project description:We have imaged optically the spatial distributions of ferroelectricity and piezoelectricity at the diffraction limit. Contributions to the birefringence from electro-optics--linked to ferroelectricity--as well as strain--arising from converse piezoelectric effects--have been recorded simultaneously in a BaTiO3 thin film. The concurrent recording of electro-optic and piezo-optic mappings revealed that, far from the ideal uniformity, the ferroelectric and piezoelectric responses were strikingly inhomogeneous, exhibiting significant fluctuations over the scale of the micrometer. The optical methods here described are appropriate to study the variations of these properties simultaneously, which are of great relevance when ferroelectrics are downscaled to small sizes for applications in data storage and processing.

| S-EPMC4629134 | biostudies-literature

Room-temperature ferroelectricity in MoTe<sub>2</sub> down to the atomic monolayer limit.

Project description:Ferroelectrics allow for a wide range of intriguing applications. However, maintaining ferroelectricity has been hampered by intrinsic depolarization effects. Here, by combining first-principles calculations and experimental studies, we report on the discovery of robust room-temperature out-of-plane ferroelectricity which is realized in the thinnest monolayer MoTe2 with unexploited distorted 1T (d1T) phase. The origin of the ferroelectricity in d1T-MoTe2 results from the spontaneous symmetry breaking due to the relative atomic displacements of Mo atoms and Te atoms. Furthermore, a large ON/OFF resistance ratio is achieved in ferroelectric devices composed of MoTe2-based van der Waals heterostructure. Our work demonstrates that ferroelectricity can exist in two-dimensional layered material down to the atomic monolayer limit, which can result in new functionalities and achieve unexpected applications in atomic-scale electronic devices.

| S-EPMC6467908 | biostudies-literature

Evolution of ferroelectricity in ultrathin PbTiO<sub>3</sub> films as revealed by electric double layer gating.

Project description:Ferroelectricity in ultrathin films is destabilized by depolarization field, which leads to the reduction of spontaneous polarization or domain formation. Here, thickness dependence of remnant polarization in PbTiO3 films is electrically revealed down to 2.6 nm by controlling the polarization direction with employing an electric double layer gating technique to suppress leakage current in ultrathin films. The remnant polarization for a 17 nm-thick film is similar to bulk value ~ 60 μC cm-2 and reduces to ~ 20 μC cm-2 for a 2.6 nm-thick film, whereas robust ferroelectricity is clearly observed in such ultrathin films. In-situ X-ray diffraction measurements under an external electric field reveal that the reduced tetragonality in ultrathin films is mostly recovered by cancelling out the depolarization field. Electric double layer gating technique is an excellent way for exploring physical properties in ultrathin ferroelectric films.

| S-EPMC7331690 | biostudies-literature

Direct observation of room-temperature out-of-plane ferroelectricity and tunneling electroresistance at the two-dimensional limit.

Project description:Out-of-plane ferroelectricity with a high transition temperature in nanometer-scale films is required to miniaturize electronic devices. Direct visualization of stable ferroelectric polarization and its switching behavior in atomically thick films is critical for achieving this goal. Here, ferroelectric order at room temperature in the two-dimensional limit is demonstrated in tetragonal BiFeO3 ultrathin films. Using aberration-corrected scanning transmission electron microscopy, we directly observed robust out-of-plane spontaneous polarization in one-unit-cell-thick BiFeO3 films. High-resolution piezoresponse force microscopy measurements show that the polarization is stable and switchable, whereas a tunneling electroresistance effect of up to 370% is achieved in BiFeO3 films. Based on first-principles calculations and Kelvin probe force microscopy measurements, we explain the mechanism of polarization stabilization by the ionic displacements in oxide electrode and the surface charges. Our results indicate that critical thickness for ferroelectricity in the BiFeO3 film is virtually absent, making it a promising candidate for high-density nonvolatile memories.

| S-EPMC6102252 | biostudies-literature

Sub-diffraction limit localization of proteins in volumetric space using Bayesian restoration of fluorescence images from ultrathin specimens.

Project description:Photon diffraction limits the resolution of conventional light microscopy at the lateral focal plane to 0.61?/NA (??=?wavelength of light, NA?=?numerical aperture of the objective) and at the axial plane to 1.4n?/NA(2) (n?=?refractive index of the imaging medium, 1.51 for oil immersion), which with visible wavelengths and a 1.4NA oil immersion objective is -220 nm and -600 nm in the lateral plane and axial plane respectively. This volumetric resolution is too large for the proper localization of protein clustering in subcellular structures. Here we combine the newly developed proteomic imaging technique, Array Tomography (AT), with its native 50-100 nm axial resolution achieved by physical sectioning of resin embedded tissue, and a 2D maximum likelihood deconvolution method, based on Bayes' rule, which significantly improves the resolution of protein puncta in the lateral plane to allow accurate and fast computational segmentation and analysis of labeled proteins. The physical sectioning of AT allows tissue specimens to be imaged at the physical optimum of modern high NA plan-apochormatic objectives. This translates to images that have little out of focus light, minimal aberrations and wave-front distortions. Thus, AT is able to provide images with truly invariant point spread functions (PSF), a property critical for accurate deconvolution. We show that AT with deconvolution increases the volumetric analytical fidelity of protein localization by significantly improving the modulation of high spatial frequencies up to and potentially beyond the spatial frequency cut-off of the objective. Moreover, we are able to achieve this improvement with no noticeable introduction of noise or artifacts and arrive at object segmentation and localization accuracies on par with image volumes captured using commercial implementations of super-resolution microscopes.

| S-EPMC3431294 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data