Nanoscale Domain Structures Research Articles

Boosting Low-E Electro-strain via High-Electronegativity B-Site Substitution in lead-free K0.5Na0.5NbO3-based ceramics

Lead-free piezoelectric actuators emerge as promising substitutes for their lead-containing counterparts to address environmental concerns. However, they often confront a trade-off between low driving electric fields and high electro-strain. Herein, a novel strategy to boost electro-strain under low electric fields is proposed by doping high-electronegativity B-site atoms into perovskite potassium sodium niobate-based ceramics. Our findings reveal that high-electronegativity B-site atoms elevate the covalency of B-O bonding, softening the short-range repulsion and introducing local multiphase coexistence. This leads to more nanoscale domain structures and lower coercive field, thereby enabling large strains to be produced at lower electric fields. Notably, a substantial 0.2% bipolar electro-strain and 0.1% unipolar electro-strain under 10kV cm-1 is achieved in Sr, Sb co-doped potassium sodium niobate ceramics, with a broad working frequency and temperature range, as well as excellent fatigue resistance. This study unveils innovative insights into designing lead-free piezoelectric ceramics with remarkable electro-strain performance and low driving electric field, promising a significant advancement in lead-free piezoelectric materials science and piezoelectric actuators.

A Small-Angle Neutron Scattering, Calorimetry and Densitometry Study to Detect Phase Boundaries and Nanoscale Domain Structure in a Binary Lipid Mixture

Techniques that can probe nanometer length scales, such as small-angle neutron scattering (SANS), have become increasingly popular to detect phase separation in membranes. But to extract the phase composition and domain structure from the SANS traces, complementary information is needed. Here, we present a SANS, calorimetry and densitometry study of a mixture of two saturated lipids that exhibits solidus-liquidus phase coexistence: 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (dDPPC, tail-deuterated DPPC) and 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC). With calorimetry, we investigated the phase diagram for this system and found that the boundary traces for both multilamellar vesicles (MLVs) as well as 50 nm unilamellar vesicles overlap. Because the solidus boundary was mostly inaccessible by calorimetry, we investigated it by both SANS and molecular volume measurements for a 1:1 dDPPC:DLPC lipid mixture. From the temperature behavior of the molecular volume for the 1:1 dDPPC:DLPC mixture, as well as the individual molecular volume of each lipid species, we inferred that the liquidus phase consists of only fluid-state lipids while the solidus phase consists of lipids that are in gel-like states. Using this solidus-liquidus phase model, the SANS data were analyzed with an unrestricted shape model analysis software: MONSA. The resulting fits show irregular domains with dendrite-like features as those previously observed on giant unilamellar vesicles (GUVs). The surface pair correlation function describes a characteristic domain size for the minority phase that decreases with temperature, a behavior found to be consistent with a concomitant decrease in membrane mismatch between the liquidus and solidus phases.

Correlation between Nanoscale Domain Structures and Superconducting Phase Transitions in Highly Crystalline 2D Superconductors

AbstractThe domains and domain boundaries in 2D materials are known to play essential roles in investigating intriguing physical properties and have potential applications in nanoscale devices. Understanding the influence of individual domains on the superconducting properties of ultrathin 2D superconductors is of crucial importance for fundamental studies on mesoscopic superconductivity as well as applications in superconducting nanoelectronics. Here, low‐temperature electronic transport measurements of high quality ultrathin Mo2C crystals are presented that show clear evidence for the presence of multiple superconducting phase induced by the nanoscale domain structures. In particular, the observation of an anomalous resistance peak in the vicinity of the onset of the superconducting transition is reported. This resistive anomaly is interpreted as a consequence of nonequilibrium charge imbalance near the domain boundaries, which could induce effective normal‐superconducting interfaces in 2D Mo2C crystals. Moreover, the magnetic field‐tuned superconductor‐metal transition for ultrathin Mo2C crystals is examined. The observed scaling behavior is consistent with the appearance of quantum Griffiths singularity in 2D superconducting systems. This study sheds light on the understanding of the domain boundaries and their role on the transport properties of highly crystalline 2D superconductors, which may open potential application of domain structure in functional superconducting nanodevices.

Multi-type nanoscale domain switching dynamics in tetragonal PIN-PMN-PT single crystal under electrical bias

Domain switching coupled with polarization reorientation allows ferroelectrics to exhibit high potential for use in nonvolatile memories, electro-optic devices, and nanoelectronics. Although several studies have elucidated domain switching, the research on switching dynamics of complex nanoscale domain structures in relaxor-based ferroelectric materials has been lacking. Herein, the domain structure and domain switching dynamics in tetragonal PIMN-PT single crystals were systemically studied via piezoresponse force microscopy. An interlocking multi-type domain pattern comprising irregular 180° ferroelectric domains and regular 90° ferroelastic domains was observed and its formation mechanism was explored. Different domain switching dynamics of field-dependent responses were investigated. The results indicate that T-phase PIMN-PT single crystals exhibit a hierarchical domain switching process. Under a low electrical-bias stimuli (<10 V), the nucleation and growth of 180° domains dominate the switching process. By increasing the electrical bias from 10 V to 80 V, 90° domain switching was gradually completed and the sample achieved a single-domain state. The nucleation and growth mechanism of ferroelectric domains under electrical-bias stimuli were also discussed. Overall, our results deepened the understanding of ferroelectric switching in complex nanoscale domain structures and facilitate the use of precise domain tailoring technology for fabricating T-phase relaxor-based ferroelectric single crystals.

Patterning of large area nanoscale domains in as-grown epitaxial ferroelectric PbTiO3 films

Effective tuning of nanoscale domain structures provides fundamental basis for controlling and engineering of various functionalities in ferroelectric materials. In this work, we demonstrate the precise patterning of nanoscopic domain structures in as-grown epitaxial PbTiO3 (PTO) films by merely introducing an ultrathin pre-patterned doping layer (e.g., Fe-doped PTO). The doping layer can effectively reverse the interfacial built-in bias, consequent to a reversed initial polarization reorientation in the as-grown film, which makes it possible to transfer the nano-patterns in the doping layer into the domain structure of ferroelectric films. For instance, we have successfully fabricated large area ordered array of nanoscale cylindrical domains (downward polarization) embedded in the matrix domain with opposite polarization (upward polarization) in PTO film. These nanoscale cylinder domains also allow deterministic and reversible erasure and creation induced by biased tip scanning. The results provide an effective pathway for on-demand patterning of large area nanoscale domains in the as-grown films, which may find applications in a wide range of nanoelectronic devices.

Crystal symmetry enables high thermoelectric performance of rhombohedral GeSe(MnCdTe2)x

High symmetry favors high power factor by virtue of the balanced Seebeck coefficient and carrier mobility, nonetheless, the role of crystal symmetry in enhancing the material’s thermoelectric performance is abstruse. Here, we employ the interplay between crystal symmetry and native point defects towards high zT of IV-VI semiconductor GeSe, which is scarce in thermoelectric study. Pristine orthorhombic GeSe has a low zT ~ 0.05 due to the high formation energy of Ge vacancy and thus the low carrier concentration (~ 1016 cm−3). Alloying GeSe with MnCdTe2 stabilizes higher-symmetry rhombohedral structure at ambient conditions, thereby effectively lowering the formation energy of Ge vacancy and raising the carrier concentration by four orders of magnitude. Meanwhile, compared to orthorhombic GeSe, the rhombohedral Ge1-yBiySe(MnCdTe2)x own higher valley degeneracy and smaller band effective mass, rendering the decent Seebeck coefficient and larger carrier mobility, respectively. Moreover, the generated multiscale microstructures in rhombohedral Ge0.96Bi0.04Se(MnCdTe2)0.10, including atomic-scale native Ge vacancies and substitution point defects, nanoscale domain structures, and micron-sized secondary phases effectively depress the lattice thermal conductivity. As a result, a state-of-the-art zT ~ 1.0 at 723 K is achieved in Ge0.96Bi0.04Se(MnCdTe2)0.10. These results attest to the efficacy of the interplay between crystal symmetry and native point defects towards high performance GeSe-based and other thermoelectric materials.

Thermally stable poly(3‐hexylthiophene): Nonfullerene solar cells with efficiency breaking 10%

AbstractSolar cells featuring polythiophenes as donors are one of the optoelectronic devices that hold notable promises for commercial application, profiting from the lowest synthetic complexity and excellent scalability. However, the complex phase behaviors of polythiophenes and their blends put constraints on modulating electrical performance and thus realizing stable performance under thermal stress. In this contribution, we present a multi‐technique approach that combines calorimetry, scattering, spectroscopy, and microscopy to thoroughly probe the thermodynamic mixing, thermal properties of materials, the evolution of nanoscale domain structure, and device performance of poly(3‐hexylthiophene) (P3HT) with a range of nonfullerene acceptors (NFAs) such as ITIC, IDTBR, and ZY‐4Cl. Accordingly, two blending guidelines are established for matching these popular NFAs with P3HT to enable highly efficient and thermally stable cells. First, blend systems with weak vitrification and hypo‐miscibility are excellent candidates for efficient solar cells. Furthermore, high thermal stability can be achieved by selecting NFAs with diffusion‐limited crystallization. The P3HT:ZY‐4Cl blend was found to endow the best performance of over 10% efficiency and an exceptionally high T80 lifetime of &gt;6000 h under continuous thermal annealing, which are among the highest values for P3HT‐based solar cells. This realization of high thermal stability and efficiency demonstrates the remarkable potentials of simple polythiophene :nonfullerene pairs in electronic applications.

Enhanced strains by flexible nanoscale domain structure in BNKT-SBT relaxor ferroelectrics

The flexible domain structure and coexistence of R and T nanodomains are responsible for the enhanced strains and strong relaxor.

Temperature- and electric-field-dependent electrical properties and nanoscale domain structures in PIN-0.49PMN-0.27 PT single crystal

The effect of temperature and electric field on phase transitions, dielectric relaxation behavior, and macroscopic electrical performances of Pb(In1/2Nb1/2)O3-0.49 Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 (PIMNT27) single crystals were studied. The nanosized domains of unpoled crystals and the engineered domains of DC electric field poled crystals were intuitively recorded by piezoresponse force microscopy (PFM). The distribution of nanosized domains with different sizes and patterns induced by domain switching and domain wall motion under different poling fields and temperatures were also studied to understand the effect of nanosized domains on phase transitions, piezoelectric, and electromechanical properties.

Structural and microstructural features of lead‐free BNT–BT thin films: Nanoscale electromechanical response analysis

AbstractThe structural, microstructural, and electromechanical properties have been investigated at the nanoscale, as a function of the lanthanum concentration, in Bi0.506Na0.46Ba0.08–3x/2LaxTiO3 (x = 0, 2 and 3 at %) (BNLBT–x) lead‐free thin films. The structural characterization, investigated from X‐ray diffraction and Raman spectroscopy, confirmed the formation of the perovskite structure and suggests the coexistence of both antiferroelectric (tetragonal) and ferroelectric (rhombohedral) phases. The surface morphology, characterized by atomic force microscopy, has shown a dense and crack‐free nanostructured surface for all the studied compositions, noting that the increase in the lanthanum content promoted a decrease in both the grain size and surface roughness. PFM imaging analyses have evidenced the ferroelectric domain structure over the surface, as well as the presence of non–piezoelectric regions attributed to the antiferroelectric phase. PFM spectroscopy measurements revealed a reliable switching behavior for locally probed ferroelectric domains, yielding a noticeable local piezoactivity, which indeed shows to increase with the increase in the doping content. The static domain wall was also analyzed in terms of the nanoscale domain structure, and the obtained dimensionality indicated a local electric field‐induced structural disorder. The clear local piezo/ferroelectric nature highlighted on the studied materials underlines the potential for applications of the BNLBT–x films for their integration into advanced electronic nanodevices.

Nanoscale Domain Structure in a Binary Lipid Mixture: A Small Angle Neutron Scattering and Calorimetry Study

In biological membranes the lipid composition is extraordinarily complex and this complexity provides proteins with the optimal lipid micro environment for physiological activity. The complexity of lipid composition and the consequences for biological systems has attracted significant interest in the past four decades. Here, however, we chose to revisit a simple binary mixture of lipids (DPPC and DLPC) which is still relevant since some biological systems can be relatively simple, composed of only a few different lipid species which form nanodomain when the temperature is decreased.

Evolution of domain structure and ferroelectric polarization in praseodymium doped BiFeO3 ceramics

Nanoscale domain structure, electric-field-induced polarization switching and electromagnetic strain in lead-free perovskite bismuth ferrite are substantial parameters for nonvolatile magnetoelectric applications. This work highlights nano-to-micro domain morphology, polarization switching and electromechanical mechanisms in (Bi1-xPrx)FeO3 ceramics in the vicinity of the morphotropic phase boundary (MPB). A coexistence of ferroelectric rhombohedral R3c and antiferroelectric orthorhombic Pbam symmetries was identified in conjunction with antiphase domain boundaries and polar nano-regions in the interiors of grains as the system crosses the MPB. Out-of-plane piezoresponse force microscopy indicates decreased ferroelectric polarization and capability of polarization switching as the system approaches the MPB. Frequency- and temperature-dependent dielectric permittivity indicates a relaxor characteristic in all compositions. The O 2p-Fe 3d and O 2p-Bi 6s(p) orbital hybridizations play key roles for evolution of structural distortion, polarization and electromechanical.

Layered perovskite with compact morphology and reduced grain size via vacuum assisted crystallization for luminescence applications

Perovskite materials have gained a lot of interest in LED application because of their excellent properties, such as direct band gap nature, high photoluminescence quantum efficiency (PLQE), high charge carrier mobility, pure color emission with small full width at half maximum, and low non-radiative recombination rate. In this work, we for the first time, developed a new protocol called vacuum assisted crystallization (VAC) for perovskite luminescence applications and optimized different parameters i.e. vacuum pressure, holding time, and annealing time. VAC is an after-deposition process applicable to control nanoscale domain structure and improve phase distribution for various deposition techniques, causing small grain size and dense formation beneficial for high luminescence. Large PLQE enhancement, smooth bright emission, high stability, and good surface morphology were obtained with VAC treatment.

Nanoscale domain structure evolution and magnetoelectric coupling for PMN-33PT/Terfenol-D multiferroic composite

Multiferroic composites of Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) single crystal and Tb0.3Dy0.7Fe2 (Terfenol-D) possess strong magnetoelectric (ME) coupling at room temperature and hold promises as magnetic field sensors, and energy harvesting devices, etc. The nanoscale domain structure evolution upon the applied magnetic field determines the ME coupling. Via introducing of the PLM (Polarized Light Microscope) into the commercialized Piezoelectric Force Microscope (PFM) (named as PLM-PFM system), in-situ observations of domain structure evolution and ME coupling are investigated for [001]-oriented PMN-33PT/Terfenol-D composites. Upon the magnetic loadings, via strain transfer, domains of orthorhombic (O) phase first expands in area, and then a phase transition from O to monoclinic (M) phase takes place in PMN-33PT. Correspondingly, modulation of the electric field-induced displacement (or the inverse piezoelectric response) can be achieved by the magnetic field. Finite-element simulations are performed to calculate the magnetic field-induced displacement, which demonstrate its dependence on the piezomagnetic coefficient of Terfenol-D. The results provide insight into the magnetic field induced domain switching in nanoscale and magnetoelectric coupling for the PMN-PT/Terfenol-D multiferroic composites.

Contrasting the solvation properties of protic ionic liquids with different nanoscale structure

The limiting activity coefficients of several hydrocarbons and aliphatic alcohols in protic ionic liquids: 2-hydroxyethylammonium nitrate (EOAN), propylammonium nitrate (PAN), butylammonium nitrate (BAN), and butylammonium thiocyanate (BASCN), were determined at 298K using gas chromatographic headspace analysis. The activity coefficients of hydrocarbons in EOAN turned out to be much higher than in BASCN or alkylammonium nitrates. The methylene group increments for the Gibbs free energies of solvation of various homological series in EOAN are also much higher than in BASCN, BAN, PAN as well as in aprotic ionic liquids or molecular solvents except water. Water-like solvation properties of EOAN are linked with the presence of a three-dimensional network of hydrogen bonds, high concentration of ion pairs, and the absence of nanoscale domain structure that exists in liquid alkylammonium salts and favors solvation of hydrocarbons in apolar domains. The sensitivity of solvation properties of PILs to their nanostructure suggests that the presence of apolar and polar domains in a liquid can be probed with the studies of solvation thermodynamics.

Ferroelectric domain engineering of lithium niobate single crystal confined in glass

Abstract

Magnetic domain writing defined by electrical gating in Pt/Co film

There is a need to control magnetic properties at a desired location in a magnetic film towards a realization of fundamental devices, such as domain wall logic or magnonic applications. Here, we demonstrate the formation of a magnetic domain structure at a desired location in a Pt/Co film, using electrical gating with a meshed gate electrode and sweeping the applied magnetic field. As the magnetic properties can be changed by modulating the electron density at the surface of the Co layer, this method in principle provides higher speed and power-efficient operation in inducing a nanoscale domain structure or in configuring a volatile magnonic crystal.

Machine Detection of Enhanced Electromechanical Energy Conversion in PbZr0.2 Ti0.8 O3 Thin Films.

Many energy conversion, sensing, and microelectronic applications based on ferroic materials are determined by the domain structure evolution under applied stimuli. New hyperspectral, multidimensional spectroscopic techniques now probe dynamic responses at relevant length and time scales to provide an understanding of how these nanoscale domain structures impact macroscopic properties. Such approaches, however, remain limited in use because of the difficulties that exist in extracting and visualizing scientific insights from these complex datasets. Using multidimensional band-excitation scanning probe spectroscopy and adapting tools from both computer vision and machine learning, an automated workflow is developed to featurize, detect, and classify signatures of ferroelectric/ferroelastic switching processes in complex ferroelectric domain structures. This approach enables the identification and nanoscale visualization of varied modes of response and a pathway to statistically meaningful quantification of the differences between those modes. Among other things, the importance of domain geometry is spatially visualized for enhancing nanoscale electromechanical energy conversion.

The indispensable role of the transversal spin fluctuations mechanism in laser-induced demagnetization of Co/Pt multilayers with nanoscale magnetic domains

The switching of magnetic domains induced by an ultrashort laser pulse has been demonstrated in nanostructured ferromagnetic films. This leads to the dawn of a new era in breaking the ultimate physical limit for the speed of magnetic switching and manipulation, which is relevant to current and future information storage. However, our understanding of the interactions between light and spins in magnetic heterostructures with nanoscale domain structures is still lacking. Here, both time-resolved magneto-optical Kerr effect experiments and atomistic simulations are carried out to investigate the dominant mechanism of laser-induced ultrafast demagnetization in [Co/Pt]20 multilayers with nanoscale magnetic domains. It is found that the ultrafast demagnetization time remains constant with various magnetic configurations, indicating that the domain structures play a minor role in laser-induced ultrafast demagnetization. In addition, both in experiment and atomistic simulations, we find a dependence of ultrafast demagnetization time τM on the laser fluence, which is in contrast to the observations of spin transport within magnetic domains. The remarkable agreement between experiment and atomistic simulations indicates that the local dissipation of spin angular momentum is the dominant demagnetization mechanism in this system. More interestingly, we made a comparison between the atomistic spin dynamic simulation and the longitudinal spin flip model, highlighting that the transversal spin fluctuations mechanism is responsible for the ultrafast demagnetization in the case of inhomogeneous magnetic structures. This is a significant advance in clarifying the microscopic mechanism underlying the process of ultrafast demagnetization in inhomogeneous magnetic structures.

Domain shape instabilities and dendrite domain growth in uniaxial ferroelectrics.

The effects of domain wall shape instabilities and the formation of nanodomains in front of moving walls obtained in various uniaxial ferroelectrics are discussed. Special attention is paid to the formation of self-assembled nanoscale and dendrite domain structures under highly non-equilibrium switching conditions. All obtained results are considered in the framework of the unified kinetic approach to domain structure evolution based on the analogy with first-order phase transformation.This article is part of the theme issue 'From atomistic interfaces to dendritic patterns'.