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In modern technology, recent advances in multi-functional devices are rapidly developed for the diverse demands of human beings. Meanwhile, durability and adaptability to extreme environmental conditions are also required. In this study, a flexible magnetoelectric (ME) heterostructure based on CoFe2O4/Pb(Zr,Ti)O3 composite thin film on muscovite is presented, with two geometries of the constituents, namely laminar heterostructure, and vertical nanostructure, adopted for the comparison. On the other hand, credited to the mechanical flexibility of muscovite, the impact of flexibility on ME properties is also discussed with a series of bending tests. Moreover, the ME response sustains for 10,000 times bending without significant decrease, validating the mechanical durability of this heterostructure on muscovite. With these advantages, a flexible proximity sensor based on this heterostructure is demonstrated for motion detection. It is expected to offer a pathway for creating the next-generational flexible devices, showing potential for future practical application.

Self-assembled systems have recently attracted extensive attention because they can display a wide range of phase morphologies in nanocomposites, providing a new arena to explore novel phenomena. Among these morphologies, a bicontinuous structure is highly desirable based on its high interface-to-volume ratio and 3D interconnectivity. A bicontinuous nickel oxide (NiO) and tin dioxide (SnO2) heteroepitaxial nanocomposite is revealed here. By controlling their concentration, we fabricated tuneable self-assembled nanostructures from pillars to bicontinuous structures, as evidenced by TEM-energy-dispersive X-ray spectroscopy with a tortuous compositional distribution. The experimentally observed growth modes are consistent with predictions by first-principles calculations. Phase-field simulations are performed to understand 3D microstructure formation and extract key thermodynamic parameters for predicting microstructure morphologies in SnO2:NiO nanocomposites of other concentrations. Furthermore, we demonstrate significantly enhanced photovoltaic properties in a bicontinuous SnO2:NiO nanocomposite macroscopically and microscopically. This research shows a pathway to developing innovative solar cell and photodetector devices based on self-assembled oxides.

Amorphous materials have attracted increasing attention in diverse fields due to their unique properties, yet their controllable fabrications still remain great challenges. Here, we demonstrate a top-down strategy for the fabrications of amorphous oxides through the amorphization of hydroxides. The versatility of this strategy has been validated by the amorphizations of unitary, binary and ternary hydroxides. Detailed characterizations indicate that the amorphization process is realized by the variation of coordination environment during thermal treatment, where the M–OH octahedral structure in hydroxides evolves to M–O tetrahedral structure in amorphous oxides with the disappearance of the M–M coordination. The optimal amorphous oxide (FeCoSn(OH)6-300) exhibits superior oxygen evolution reaction (OER) activity in alkaline media, where the turnover frequency (TOF) value is 39.4 times higher than that of FeCoSn(OH)6. Moreover, the enhanced OER performance and the amorphization process are investigated with density functional theory (DFT) and molecule dynamics (MD) simulations. The reported top-down fabrication strategy for fabricating amorphous oxides, may further promote fundamental research into and practical applications of amorphous materials for catalysis.

The formation of complex hierarchical nanostructures has attracted a lot of attention from both the fundamental science and potential applications point of view. Spherulite structures with radial fibrillar branches have been found in various solids; however, their growth mechanisms remain poorly understood. Here, we report real time imaging of the formation of two-dimensional (2D) iron oxide spherulite nanostructures in a liquid cell using transmission electron microscopy (TEM). By tracking the growth trajectories, we show the characteristics of the reaction front and growth kinetics. Our observations reveal that the tip of a growing branch splits as the width exceeds certain sizes (5.5–8.5 nm). The radius of a spherulite nanostructure increases linearly with time at the early stage, transitioning to nonlinear growth at the later stage. Furthermore, a thin layer of solid is accumulated at the tip and nanoparticles from secondary nucleation also appear at the growing front which later develop into fibrillar branches. The spherulite nanostructure is polycrystalline with the co-existence of ferrihydrite and Fe3O4 through-out the growth. A growth model is further established, which provides rational explanations on the linear growth at the early stage and the nonlinearity at the later stage of growth.

Controlling ferroic orders (ferroelectricity, ferromagnetism and ferroelasticity) by optical methods is a significant challenge due to the large mismatch in energy scales between the order parameter coupling strengths and the incident photons. Here, we demonstrate an approach to manipulate multiple ferroic orders in an epitaxial mixed-phase BiFeO3 thin film at ambient temperature via laser illumination. Phase-field simulations indicate that a light-driven flexoelectric effect allows the targeted formation of ordered domains. We also achieved precise sequential laser writing and erasure of different domain patterns, which demonstrates a deterministic optical control of multiferroicity at room temperature. As ferroic orders directly influence susceptibility and conductivity in complex materials, our results not only shed light on the optical control of multiple functionalities, but also suggest possible developments for optoelectronics and related applications.

Flexible and transparent applications have become an emerging technology and have shifted to the forefront of materials science research in recent years. Transparent conductive oxide films have been applied for flat panel displays, solar cells, and transparent glass coatings. However, none of them can fulfill the requirements for advanced transparent flexible devices, such as high-frequency applications. Here, we present a promising technique for transparent flexible conducting oxide heteroepitaxial films: the direct fabrication of epitaxial molybdenum-doped indium oxide (IMO) thin films on a transparent flexible muscovite substrate. An n-type epitaxial IMO film is demonstrated with a mobility of 109 cm2 V−1 s−1, a figure of merit of 0.0976 Ω−1, a resistivity of 4.5 × 10−5 Ω cm and an average optical transmittance of 81.8% in the visible regime. This heteroepitaxial system not only exhibits excellent electrical and optical performance but also shows excellent mechanical durability. Our results illustrate that this is an outstanding way to fabricate transparent and flexible conducting elements for the evolution and expansion of next-generation smart devices. A thin, flexible material that is transparent and can conduct an electrical current has been developed by scientists in Taiwan. Materials with flexibility, transparency and conductivity are useful for wearable optoelectronics, but are rare. Indium tin oxide is a widely used transparent conductor, but when used in thin layers its electrical properties are not good enough for efficient thin-film transistors, thin-film solar cells and high-frequency devices. Ying-Hao Chu and co-workers from the National Chiao Tung University in Hsinchu used a technique called radio-frequency magnetron sputtering to deposit a thin film of indium oxide containing small amounts of molybdenum on a substrate. Measurements showed that the films had high charge mobility at room temperature, low electrical resistivity, and optical transparency, indicating that the material could be used in the next generation of smart devices. We present a promising technique for transparent flexible conducting oxide heteroepitaxial films: the direct fabrication of epitaxial molybdenum-doped indium oxide (IMO) thin films on a transparent flexible muscovite substrate. An n-type epitaxial IMO film is demonstrated with a mobility of 109 cm2 V−1 s−1, a figure of merit of 0.0976 Ω−1, a resistivity of 4.5 × 10−5 Ω cm and an average optical transmittance of 81.8% in the visible regime. IMO heterostructure not only exhibits excellent performance but also shows excellent mechanical durability. This study demonstrated an extraordinary achievement for the evolution and expansion of next-generation smart devices.

Flexible and self-powered deep ultraviolet (UV) photodetectors are pivotal for next-generation electronic skins to enrich human life quality. The fabrication of epitaxial β-Ga2O3 thin films is challenging on flexible substrates due to high-temperature growth requirements. Herein, β-Ga2O3 ($$\stackrel{-}{2}$$ 2 - 0 1) films are hetero-epitaxially grown on ultra-thin and environment-friendly muscovite mica which is the first time β-Ga2O3 epitaxy growth on any flexible substrate. Integration of Gallium oxide with muscovite enables high-temperature processing as well as excellent flexibility compared to polymer substrates. Additionally, the metal–semiconductor-metal (MSM) photodetector on β-Ga2O3 layer shows an ultra-low dark current of 800 fA at zero bias. The photovoltaic peak responsivity of 11.6 µA/W is obtained corresponding to very weak illumination of 75 μW/cm2 of 265 nm wavelength. Thermally stimulated current (TSC) measurements are employed to investigate the optically active trap states. Among these traps, trap with an activation energy of 166 meV dominates the persistence photocurrent in the devices. Finally, photovoltaic detectors have shown excellent photocurrent stability under bending induced stress up to 0.32%. Hence, this novel heteroepitaxy opens the new way for flexible deep UV photodetectors.

A series of self-assembled WO3–BiVO4 nanostructured thin films with 17, 25, 50, 67, and 100 mol% WO3 were grown on the (001) yttria-stabilized zirconia (YSZ) substrate by pulsed laser deposition method. The microstructures including crystalline phases, epitaxial relationship, interface structures, and chemical composition distributions were investigated by a combination of various electron microscopy techniques including scanning electron microscopy, transmission electron microscopy, and X-ray energy dispersive spectroscopy. The monoclinic BiVO4 formed the matrix, in which WO3 nanopillars were embedded with specific epitaxial relationships. In BiVO4-rich sample, orthorhombic Bi2WO6 was formed. However, metastable hexagonal WO3 phase and orthorhombic WO3 phase coexisted in other composite samples. The thin amorphous layer at the film/substrate interface indicated that the mismatch strain between films and substrate is released. The hydrostatic tensile strain due to thermal expansion mismatch between BiVO4 and WO3 as well as the diffusion of Bi into the WO3 stabilized the metastable h-WO3. A WO3–BiVO4 pseudobinary phase diagram was proposed based on the magnitude of the thermal expansion mismatch and the distance of Bi diffusion, which can be applied to design the microstructures of WO3–BiVO4 heterojunctions and optimize their photoelectrochemical properties.

The competition between order parameters, such as ferroelectricity, ferromagnetism, and superconductivity, is one of the most fascinating topics in condensed matter physics. Here, we report intriguing anisotropic superconductivity in YBa2Cu3O7 − x films induced by a multiferroic, BiFeO3, with periodic domain patterns. The anisotropic superconductivity was investigated by transport measurements and supported by phase-field simulations, and then the detailed local electronic structures were revealed by cross-sectional scanning tunneling microscopy. We found that the oxygen redistribution in YBa2Cu3O7 − x modulated by the ferroelectric polarization in BiFeO3 was the key mechanism driving this anisotropic superconductivity. The presented heteroarchitecture of a high-temperature superconductor and a domain-engineered multiferroic provides a new approach to tune superconductivity and offers potential advantages for the design of future multifunctional devices. Combining two unusual materials offers a way to fine-tune superconductivity, according to scientists in Taiwan, China and the USA. Multiferroics are both ferromagnetic—that is, they become permanently magnetised when exposed to a magnetic field—and ferroelectric, the electric equivalent of ferromagnetism. This combination allows the electric control of magnetism. Ying-Hao Chu from the National Chiao Tung University in Hsinchu City, Taiwan, and co-workers have shown that multiferroics can also control superconductivity. The team combined thin films of the multiferroic bismuth ferrite (BiFeO3) and a superconductor called YBCO (YBa2Cu3O7-x). They found that the different ferroelectric areas in the bismuth ferrite caused a redistribution of the oxygen atoms in the YBCO, and this created a more exotic superconductor known as an asymmetric superconductor. This ability to tune superconductivity could be harnessed in future magnetoelectric devices. The periodic domain pattern of BiFeO3 enables the anisotropic superconductivity in YBa2Cu3O7 − x. In this work, we introduce a design of periodic multiferroic domain patterns to create the anisotropic superconductivity. High TC can be found when we measured the resistance parallel to the domain wall direction and the broader transition with lower TC is found to be perpendicular to the domain walls. (a) and (b) the resistance versus temperature in YBa2Cu3O7 − x/BiFeO3 heterostructures with two different domain patterns 109° and 71°, respectively.

Control of inhomogeneity in materials in order to avoid unexpected effects to the system remains a challenge. In this study, we seek to engineer inhomogeneity in materials and anticipate new properties. Through precise control of composition at the atomic scale, an electrical polarization is induced in the composition-graded LaAlO3–SrTiO3 solid solution epitaxially deposited on NdGaO3 substrates. By tailoring the direction of compositional gradient, the relationship between structure and electrical polarization is simulated via phase-field modeling and revealed by a combination of scanning transmission electron microscopy and scanning probe microscopy. The analysis of the results indicates that the induced polarization is due to the flexoelectric effect in the compositional gradient system. The results of this study provide a new pathway for obtaining a new material genome. Moreover, by a suitable design of the new genome, that is, by using different combinations of compositional gradient geometries, local conduction can be obtained and manipulated, providing a new approach to obtain the desired properties. Controlling the crystal quality of oxide thin films offers a way to engineer unexpected and novel material properties. Altering the distance between atoms in a crystalline film, by growing it on a different substrate for example, induces a physical strain and alters its properties. The characteristics of the film can also be altered by varying its composition. Researchers led by Chun-Gang Duan from the East China Normal University, Shanghai, China, and Ying-Hao Chu from National Chiao Tung University, Hsinchu, Taiwan, combined these two approaches by controlling the atomic strain in a combination of strontium titanate and lanthanum aluminate. The team’s computer model indicated that this allowed the creation of a material with so-called flexoelectric properties, where the electric and elastic properties are interlinked. This was verified using electron and piezoresponse force microscopy. In this work we report the electrical polarization can be induced by composition-graded LaAlO3-SrTiO3 solid solution. The analysis indicates that the induced polarization is attributed to the flexoelectric effect in the compositional gradient system. By a suitable combination of compositional gradient in geometry, a local conduction can be created and manipulated, delivering a new approach to obtain unveiled properties. delivering a new pathway to acquire material genome based on material inhomogeneity.

Mesocrystal-a new class of crystals compared with conventional single crystals and randomly distributed nanocrystal systems-has captured significant attention in recent decades. Current studies have been focused on the advanced synthesis as well as the intriguing properties of mesocrystal. In order to create new opportunities upon functional mesocrystals, they can be regarded as a new functional entirety when integrated with unique matrix environments. The elegant combination of mesocrystals and matrices has enabled researchers to realize enthralling tunabilities and to derive new functionalities that cannot be found in individual components. Therefore, mesocrystal-embedded system forms a new playground towards multifunctionalities. This review article delivers a general roadmap that portrays the enhancement of intrinsic properties and new functionalities driven by novel mesocrystal-embedded oxide systems. An in-depth understanding and breakthroughs achieved in mesocrystal-embedded oxide systems are highlighted. This article concludes with a brief discussion on potential directions and perspectives along this research field.

The Mn valence in thin film La0.7Sr0.3MnO3 was studied as a function of film thickness in the range of 1–16 unit cells with a combination of non-destructive bulk and surface sensitive X-ray absorption spectroscopy techniques. Using a layer-by-layer valence model, it was found that while the bulk averaged valence hovers around its expected value of 3.3, a significant deviation occurs within several unit cells of the surface and interface. These results were supported by first principles calculations. The surface valence increases to up to Mn3.7+, whereas the interface valence reduces down to Mn2.5+. The change in valence from the expected bulk value is consistent with charge redistribution due to the polar discontinuity at the film-substrate interface. The comparison with theory employed here illustrates how this layer-by-layer valence evolves with film thickness and allows for a deeper understanding of the microscopic mechanisms at play in this effect. These results offer insight on how the two-dimensional electron gas is created in thin film oxide alloys and how the magnetic ordering is reduced with dimensionality.

Domain orientations and their volume ratios in ferroelectrics are recognized as a compelling topic recently for domain switching dynamics and domain stability in devices application. Here, an optimized second harmonic generation method has been explored for ferroelectric domain characterization. Combing a unique theoretical model with azimuth-polarization-dependent second harmonic generation response, the complex domain components and their distributions can be rigidly determined in ferroelectric thin films. Using the proposed model, the domain structures of rhombohedral BiFeO3 films with 71° and 109° domain wall, and, tetragonal BiFeO3, Pb(Zr0.2Ti0.8)O3, and BaTiO3 ferroelectric thin films are analyzed and the corresponding polarization variants are determined. This work could provide a powerful and all-optical method to track and evaluate the evolution of ferroelectric domains in the ferroelectric-based devices. An optimized optical method is developed to determine the ferroelectric domain structure and their distributions in several ferroelectric films. A team led by Xiangli Zhong and Yichun Zhou from Xiangtan University, and Jianmin Yuan from National University of Defense Technology in China, combined optimized second harmonic generation (SHG) measurements and theoretical analysis to determine the polarization components of domains and their distribution in rhobohedral BiFeO3, tetragonal BiFeO3, Pb(Zr0.2Ti0.8)O3 and BaTiO3 thin films. They first collect azimuth-polarization-dependent SHG signals with respect to both the polarization angle of the incident beam and the azimuth angle of sample relative to the beam. Then they fit the SHG signals with a theoretical model with good agreement. This work provides an effective and all-optical method to determine the domain structures and distributions for ferroelectric thin films.

The research field of oxide heteroepitaxy suffers from the characteristics of misfit strain and substrate clamping, hampering the optimization of performance and the gain of fundamental understanding of oxide systems. Recently, there are demonstrations on functional oxides epitaxially fabricated on layered muscovite substrate. In these heterostructures, due to the weak interaction between substrate and film, they show the lattice of films close to bulk with excellent strictive properties, suggesting that these critical problems can be potentially solved by van der Waals oxide heteroepitaxy. In addition, by exploiting the transparent and flexible features of muscovite, such a heteroepitaxy can deliver new material solutions to transparent soft technology. In this paper, the history, development, and current status of van der Waals oxide heteroepitaxy are addressed and discussed. In the end, new research directions in terms of fundamental study and practical application are proposed to highlight the importance of this research field.

Although the size effect in ferroelectric thin films has been known for long time, the underlying mechanism is not yet fully understood and whether or not there is a critical thickness below which the ferroelectricity vanishes is still under debate. Here, we directly measure the thickness-dependent polarization in ultrathin PbZr0.2Ti0.8O3 films via quantitative annular bright field imaging. We find that the polarization is significantly suppressed for films, Understanding ferroelectricity at reduced dimensions will be important for future sub-nanoscale devices based on ferroelectrics. Using high resolution electron microscopy; Gao et al., observe the existence of a measurable polarization at a thickness of just 1.5-unit cells

We report the study of Mg cathodic electrochemical deposition on Ti and Au electrode using a multimodal approach by examining the sample area in-situ using liquid cell transmission electron microscopy (TEM), scanning transmission X-ray microscopy (STXM) and X-ray absorption spectroscopy (XAS). Magnesium Aluminum Chloride Complex was synthesized and utilized as electrolyte, where non-reversible features during in situ charging-discharging cycles were observed. During charging, a uniform Mg film was deposited on the electrode, which is consistent with the intrinsic non-dendritic nature of Mg deposition in Mg ion batteries. The Mg thin film was not dissolvable during the following discharge process. We found that such Mg thin film is hexacoordinated Mg compounds by in-situ STXM and XAS. This study provides insights on the non-reversibility issue and failure mechanism of Mg ion batteries. Also, our method provides a novel generic method to understand the in situ battery chemistry without any further sample processing, which can preserve the original nature of battery materials or electrodeposited materials. This multimodal in situ imaging and spectroscopy provides many opportunities to attack complex problems that span orders of magnitude in length and time scale, which can be applied to a broad range of the energy storage systems.

Self-assembled vertical heteroepitaxial nanostructures (VHN) in the complex oxide field have fascinated scientists for decades because they provide degrees of freedom to explore in condensed matter physics and design-coupled multifunctionlities. Recently, of particular interest is the perovskite-spinel-based VHN, covering a wide spectrum of promising applications. In this review, fabrication of VHN, their growth mechanism, control, and resulting novel multifunctionalities are discussed thoroughly, providing researchers a comprehensive blueprint to construct promising VHN. Following the fabrication section, the state-of-the-art design concepts for multifunctionalities are proposed and reviewed by suitable examples. By summarizing the outlook of this field, we are excitedly expecting this field to rise with significant contributions ranging from scientific value to practical applications in the foreseeable future.

We present the study of the synthesis of (001) nickel oxide (NiO) epitaxial nanocrystals grown on (001) strontium titanate (SrTiO3) single crystal substrates. Pulsed laser deposition of the bismuth nickel oxide (BiNiO3, BNO) perovskite precursor followed by post-deposition processing is carried out to form the NiO nanocrystals. A detailed analysis of the dimensions of nanocrystals reveals that the morphology attained differs from the thermodynamically expected equilibrium shape. The deviations from the equilibrium shape are found to follow a systematic trend where the in-plane basal dimensions, that is, the length and width of the nanocrystals grown differ in discretized dimensions. This discretization suggests that for a given interfacial area of nanocrystals there are multiple stable basal rectangular geometries attainable.

The ultrafast dynamics in (100)-oriented BiFeO3 thin films were studied from 20 K to 300 K by using the dual-color femtosecond pump-probe spectroscopy, which were performed by the 400 nm (3.1 eV) pump pulses above the energy gap of 2.67 eV and the 800 nm (1.55 eV) probe pulses below the energy gap of 2.67 eV. From the temperature-dependent transient reflectivity changes (ΔR/R), the anomalous changes were clearly observed below 200 K caused by magnons. Thus, the femtosecond pump-probe spectroscopy could unambiguously reveal the magnetization dynamics in BiFeO3 with strong magnetoelectric coupling.

In conventional solid-state photovoltaics, electron-hole pairs are created by light absorption in a semiconductor and separated by the electric field spaning a micrometre-thick depletion region. The maximum voltage these devices can produce is equal to the semiconductor electronic bandgap. Here, we report the discovery of a fundamentally different mechanism for photovoltaic charge separation, which operates over a distance of 1-2 nm and produces voltages that are significantly higher than the bandgap. The separation happens at previously unobserved nanoscale steps of the electrostatic potential that naturally occur at ferroelectric domain walls in the complex oxide BiFeO(3). Electric-field control over domain structure allows the photovoltaic effect to be reversed in polarity or turned off. This new degree of control, and the high voltages produced, may find application in optoelectronic devices.

Multiferroic materials showing coupled electric, magnetic and elastic orderings provide a platform to explore complexity and new paradigms for memory and logic devices. Until now, the deterministic control of non-ferroelectric order parameters in multiferroics has been elusive. Here, we demonstrate deterministic ferroelastic switching in rhombohedral BiFeO(3) by domain nucleation with a scanning probe. We are able to select among final states that have the same electrostatic energy, but differ dramatically in elastic or magnetic order, by applying voltage to the probe while it is in lateral motion. We also demonstrate the controlled creation of a ferrotoroidal order parameter. The ability to control local elastic, magnetic and torroidal order parameters with an electric field will make it possible to probe local strain and magnetic ordering, and engineer various magnetoelectric, domain-wall-based and strain-coupled devices.

In the past decades, mesocrystal, a kind of nanocrystals with specific crystallographic orientation, has drawn a lot of attention due to its intriguing functionalities. While the research community keeps searching for new mesocrystal systems, it is equally crucial to develop new approaches to tune the properties of mesocrystals. In this work, a self-organized two-dimensional mesocrystal composed of highly oriented CoFe2O4 (CFO) nano-crystals with assistance of different perovskite matrices is studied as a model system. We have demonstrated that the strain state and corresponding magnetic properties of the CFO mesocrystal can be modulated by changing the surrounding perovskite matrix through their intimate structural coupling. Interestingly, this controllability is more strongly correlated to the competition of bonding strength between the matrices and the CFO mesocrystals rather than the lattice mismatch. When embedded in a matrix with a higher melting point or stiffness, the CFO mesocrystal experiences higher out-of-plane compressive strain and shows a stronger magnetic anisotropy as well as cation site-exchange. Our study suggests a new pathway to tailor the functionalities of mesocrystals.

Multiferroic materials, which offer the possibility of manipulating the magnetic state by an electric field or vice versa, are of great current interest. In this work, we demonstrate the first observation of electrical control of antiferromagnetic domain structure in a single-phase multiferroic material at room temperature. High-resolution images of both antiferromagnetic and ferroelectric domain structures of (001)-oriented multiferroic BiFeO3 films revealed a clear domain correlation, indicating a strong coupling between the two types of order. The ferroelectric structure was measured using piezo force microscopy, whereas X-ray photoemission electron microscopy as well as its temperature dependence was used to detect the antiferromagnetic configuration. Antiferromagnetic domain switching induced by ferroelectric polarization switching was observed, in agreement with theoretical predictions.

High-performance Pb(Zr,Ti)O3, PZT, thin films were synthesized on Si substrates by using low-temperature laser-assisted processes, which combine pulsed laser deposition (PLD), laser lift-off (LLO) and laser-annealing (LA) processes. The PZT films were first grown on sapphire substrates at 400 °C, using Ba(Mg1/3Ta2/3)O3, BMT, as seeding layer, by the PLD process, and were then transferred to Si substrates at room temperature by a LLO transferring process. Utilization of the BMT layer is of critical importance in those processes, since it acted as a nucleation layer for the synthesis of the PZT thin films on the sapphire substrates and, at the same time, served as a sacrificial layer during laser irradiation in the LLO process. After the LLO process, the surfaces of the PZT films were recovered by the LA process for removing the damage induced by the LLO process. A thin BMT (∼30 nm) layer is randomly oriented, resulting in non-textured PZT films with good ferroelectric properties, viz. Pr=20.6 μC/cm2 and Ec=126 kV/cm, whereas a thick BMT (∼100 nm) layer is (100) preferentially oriented, leading to (100)-textured PZT films with markedly better ferroelectric properties, viz. Pr=34.4 μC/cm2 and Ec=360 kV/cm.

Self-assembled nanocomposites have gained much attention over the past decade due to their intriguing properties and functionalities. In this work, we developed a self-assembled nanocomposite photoanode composed of an epitaxial BiVO4 matrix embedded with WO3 mesocrystals for photoelectrochemical (PEC) applications in the visible-light regime. The orientation of the crystal facet and interface provides a superior template to understand the intimate contact between the two constituent phases. We demonstrate that the interfacial coupling of the mesocrystal and matrix improves the separation of photoexcited carriers and the properties of charge transfer, resulting in a greatly enhanced PEC performance compared with their parent compounds. The current study demonstrates that the utilization of the interface-to-volume ratio to optimize charge interactions in the nanocomposite is essential for the advanced design of novel mesocrystal-embedded nanocomposite photoelectrodes. Optimizing how two photocatalysts contact each other inside an amalgamated crystal may enhance solar energy conversion strategies. Bismuth vanadium oxide (BiVO4) is a bright yellow pigment that readily turns photons into electronic charges, which can be used to split water into hydrogen and oxygen gas. The team of Ying-Hao Chu from Taiwan's National Chiao Tung University has now found that embedding tungsten oxide (WO3) nanostructures into BiVO4 crystals makes it easier for photogenerated carriers to reach their target. Using pulsed laser deposition, the researchers grew bamboo-shaped nanotubes inside a BiVO4 matrix to produce numerous heterointerfaces. Band structure analysis and transport measurements showed that the improved charge separation at these interfaces provided more carriers for catalytic water splitting. The material's tunable structure makes it a promising tool for understanding surface-to-volume effects in other nanocomposites. We developed a self-assembled nanocomposite photoanode composed of epitaxial BiVO4 (BVO) matrix embedded with WO3 (WO) mesocrystal for photoelectrochemical (PEC) water splitting in the visible-light regime. The well-defined WO3-BiVO4 interface and controllable thickness provide a template for the fundamental understanding of photoactivity in the nanocomposite. The interfacial coupling of the mesocrystal and matrix improves the separation of photoexcited carriers and the properties of charge transfer, resulting in a significantly enhanced PEC performance. The utilization of the interface-to-volume ratio to optimize the charge interaction of the nanocomposite is essential for the advance design of novel mesocrystal-embedded nanocomposite photoelectrodes.

Magnetoelectrics and multiferroics present exciting opportunities for electric-field control of magnetism. However, there are few room-temperature ferromagnetic-ferroelectrics. Among the various types of multiferroics the bismuth ferrite system has received much attention primarily because both the ferroelectric and the antiferromagnetic orders are quite robust at room temperature. Here we demonstrate the emergence of an enhanced spontaneous magnetization in a strain-driven rhombohedral and super-tetragonal mixed phase of BiFeO₃. Using X-ray magnetic circular dichroism-based photoemission electron microscopy coupled with macroscopic magnetic measurements, we find that the spontaneous magnetization of the rhombohedral phase is significantly enhanced above the canted antiferromagnetic moment in the bulk phase, as a consequence of a piezomagnetic coupling to the adjacent tetragonal-like phase and the epitaxial constraint. Reversible electric-field control and manipulation of this magnetic moment at room temperature is also shown.