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Increasing interest in three-dimensional nanostructures adds impetus to electron microscopy techniques capable of imaging at or below the nanoscale in three dimensions. We present a reconstruction algorithm that takes as input a focal series of four-dimensional scanning transmission electron microscopy (4D-STEM) data. We apply the approach to a lead iridate, PbIrO, and yttrium-stabilized zirconia, YZrO, heterostructure from data acquired with the specimen in a single plan-view orientation, with the epitaxial layers stacked along the beam direction. We demonstrate that Pb–Ir atomic columns are visible in the uppermost layers of the reconstructed volume. We compare this approach to the alternative techniques of depth sectioning using differential phase contrast scanning transmission electron microscopy (DPC-STEM) and multislice ptychographic reconstruction.

With the scaling of lateral dimensions in advanced transistors, an increased gate capacitance is desirable both to retain the control of the gate electrode over the channel and to reduce the operating voltage1. This led to a fundamental changein the gate stack in 2008,the incorporation of high-dielectric-constant HfO2(ref.2), which remains the material of choiceto date. Here we report HfO2-ZrO2 superlattice heterostructures as a gate stack, stabilized with mixed ferroelectric-antiferroelectric order, directly integrated onto Si transistors, and scaled down to approximately 20 ångströms, the same gate oxide thickness required for high-performance transistors. The overall equivalent oxide thickness in metal-oxide-semiconductor capacitors is equivalent to an effective SiO2 thickness of approximately 6.5 ångströms. Such a low effective oxide thickness and the resulting large capacitance cannot be achieved in conventional HfO2-based high-dielectric-constant gate stacks without scavenging the interfacial SiO2, which has adverse effects on the electron transport and gate leakage current3. Accordingly, our gate stacks, which do not require such scavenging, provide substantially lower leakage current and no mobility degradation. This work demonstrates that ultrathin ferroic HfO2-ZrO2 multilayers, stabilized with competing ferroelectric-antiferroelectric order in the two-nanometre-thickness regime, provide a path towards advanced gate oxide stacks in electronic devices beyond conventional HfO2-based high-dielectric-constant materials.

The emergence of artificial intelligence and machine-learning-based systems, in conjunction with the pervasive implementation of the internet of things has put a strong emphasis on the energy efficiency of computing. This has triggered research on multiple pathways to improve computing efficiency, spanning 3-D integration of logic and memory as well as new, physics-based pathways including those embracing the electron’s spin degree of freedom, namely spintronics. Concurrently, the proposed integration of superconductivity and spintronics emphasizes complex oxides as a promising platform which in principle can integrate spin current manipulation and high temperature superconductivity within the same complex system. Here, we report giant spin-orbit torque (SOT) discovered in the normal state of a complex oxide superconductor, Ba(Pb,Bi)O3, which provides isotropic and easily manipulated superconducting properties. Using spin-torque ferromagnetic resonance (ST-FMR) and d.c. non-linear Hall measurements, we find a robust SOT efficiency exceeding unity and demonstrate current driven magnetization switching at current densities as low as \(4\times {10}^{5}\text{A}{\text{c}\text{m}}^{-2}\). The hybridized s-p orbital character at the Fermi energy makes this an unexpectedly large value. We postulate the presence of an unconventional SOT generation in bismuthate heterostructures and anticipate our results will trigger further exploration of such complex oxides for the development of superconducting spintronics.

Competition between ground states at phase boundaries can lead to significant changes in properties under stimuli, particularly when these ground states have different crystal symmetries. A key challenge is to stabilize and control the coexistence of symmetry-distinct phases. Using BiFeO₃ layers confined between layers of dielectric TbScO₃ as a model system, we stabilize the mixed-phase coexistence of centrosymmetric and non-centrosymmetric BiFeO₃ phases at room temperature with antipolar, insulating and polar semiconducting behaviour, respectively. Application of orthogonal in-plane electric (polar) fields results in reversible non-volatile interconversion between the two phases, hence removing and introducing centrosymmetry. Counterintuitively, we find that an electric field ‘erases’ polarization, resulting from the anisotropy in octahedral tilts introduced by the interweaving TbScO₃ layers. Consequently, this interconversion between centrosymmetric and non-centrosymmetric phases generates changes in the non-linear optical response of over three orders of magnitude, resistivity of over five orders of magnitude and control of microscopic polar order. Our work establishes a platform for cross-functional devices that take advantage of changes in optical, electrical and ferroic responses, and demonstrates octahedral tilts as an important order parameter in materials interface design. ISSN:1476-1122 ISSN:1476-4660

As the length scales of materials decrease, the heterogeneities associated with interfaces become almost as important as the surrounding materials. This has led to extensive studies of emergent electronic and magnetic interface properties in superlattices1–9. However, the interfacial vibrations that affect the phonon-mediated properties, such as thermal conductivity10,11, are measured using macroscopic techniques that lack spatial resolution. Although it is accepted that intrinsic phonons change near boundaries12,13, the physical mechanisms and length scales through which interfacial effects influence materials remain unclear. Here we demonstrate the localized vibrational response of interfaces in strontium titanate–calcium titanate superlattices by combining advanced scanning transmission electron microscopy imaging and spectroscopy, density functional theory calculations and ultrafast optical spectroscopy. Structurally diffuse interfaces that bridge the bounding materials are observed and this local structure creates phonon modes that determine the global response of the superlattice once the spacing of the interfaces approaches the phonon spatial extent. Our results provide direct visualization of the progression of the local atomic structure and interface vibrations as they come to determine the vibrational response of an entire superlattice. Direct observation of such local atomic and vibrational phenomena demonstrates that their spatial extent needs to be quantified to understand macroscopic behaviour. Tailoring interfaces, and knowing their local vibrational response, provides a means of pursuing designer solids with emergent infrared and thermal responses., The vibrational states emerging at the interface in oxide superlattices are characterized theoretically and at atomic resolution, showing the impact of material length scales on structure and vibrational response.

Nanobeam electron diffraction can probe local structural properties of complex crystalline materials including phase, orientation, tilt, strain, and polarization. Ideally, each diffraction pattern from a projected area of a few unit cells would produce clear a Bragg diffraction pattern, where the reciprocal lattice vectors can be measured from the spacing of the diffracted spots, and the spot intensities are equal to the square of the structure factor amplitudes. However, many samples are too thick for this simple interpretation of their diffraction patterns, as multiple scattering of the electron beam can produce a highly nonlinear relationship between the spot intensities and the underlying structure. Here, we develop a stacked Bloch wave method to model the diffracted intensities from thick samples with structure that varies along the electron beam. Our method reduces the large parameter space of electron scattering to just a few structural variables per probe position, making it fast enough to apply to very large fields of view. We apply our method to SrTiO$_3$/PbTiO$_3$/SrTiO$_3$ multilayer samples, and successfully disentangle specimen tilt from the mean polarization of the PbTiO$_3$ layers. We elucidate the structure of complex vortex topologies in the PbTiO$_3$ layers, demonstrating the promise of our method to extract material properties from thick samples.

Supercapacitors are progressively being utilized for storage systems in sustainable nanotechnologies. A NiCoS nanostructure was synthesized on nickel foam by an in situ one-pot hydrothermal method at different reaction temperatures (80, 100, and 120 °C) keeping other reaction parameters such as pH and reaction time constant for supercapacitor applications. The SEM report revealed a plate-like nanostructures of NiCoS on nickel foam (NiCoS/NF). The electrode prepared at 100 °C exhibits better electrochemical activities compared to electrodes prepared at 80 and 120 °C. The integrated binder-free NiCoS/NF electrode for supercapacitor, optimized at 100 °C, manifested a large specific capacitance of 3309 mF cm−2 at a current density of 1 mA cm−2 with a notable rate capability of 427 mF cm−2 even at 10 mA cm−2. The asymmetric supercapacitor fabricated with optimized NiCoS/NF prepared at 100 °C exhibited an exceptionally high energy density of 2.04 mW h cm−3 at a power density of 42.64 mW cm−3.

A series of ternary ZnO hollow sphere/carbon quantum dots/reduced graphene oxide (ZnO/CQDs/r-GO) nanocomposites were successfully prepared via solvothermal technique in the presence of the polyethylene glycol 400 (PEG 400) as a solvent. The structural details of as-prepared ZnO/CQDs/r-GO nanocomposites were characterized by powder X-ray diffraction analysis. The morphological properties of the composite were analyzed using field emission scanning microscopy (FE-SEM). The visible light absorption ability of the as-prepared pristine and ternary nanocomposites was examined using UV–visible (UV–Vis) spectrophotometry. The photocatalytic activity of ZnO, ZnO/CQDs, ZnO/r-GO, and ZnO/CQDs/r-GO nanostructures were evaluated for the degradation of organic pollutants such as methylene orange (MO), rhodamine B (RhB), and methylene blue (MB). The different composites with various amounts of reduced graphene oxide (r-GO) and carbon quantum dots (CQDs) were synthesized to enhance photocatalytic activity. The ZnO/CQDs/r-GO composites showed excellent potential for photocurrent generation compared with ZnO, ZnO/CQDs and ZnO/r-GO under-stimulated sunlight. The effect of various parameters such as the effect of reaction temperature, catalyst concentration, pH, and concentration of MB dye has been also studied. The photo-assisted catalytic degradation properties of the catalyst after five cycles exhibit high stability.

ZSM-5:CeO2 nanocomposites were prepared by two-step hydrothermal method in combination with the wet impregnation method. The synthesized nanocomposites were characterized by XRD, FESEM, TEM, EDX, elemental mapping, FTIR and UV–vis analysis. The bandgap investigations were done using tauc plot and the bandgap of ZSM-5 has been reduced from 3.90 to 3.15 eV upon CeO2 loading. The synthesized nanocomposites were tested for photocatalytic activity under a halogen lamp and the effect of CeO2 loading on ZSM5 has been examined. Among the various nanocomposites synthesized, ZSM-5:CeO2 25 wt% exhibited better methyl orange degradation of about 95.6% with an initial dye concentration of 10 mg/l, pH 7, 100 mg of photocatalyst under halogen lamp for 75 min. Additionally, the effect of various reaction parameters like dye concentration (10–25 mg/l), photocatalyst dosage (25–125 mg), and pH (3–9) was probed to get better performance. Tapping experiments were conducted with various radical scavengers to get insight into the key active species responsible for the photodegradation of methyl orange. The result portrays the importance of hydroxyl radical for the degradation of methyl orange dye. Cycle test and stability studies showed that the photocatalyst was stable even after four cycles. In summary, ZSM-5:CeO2 nanocomposites can be a suitable photocatalyst for numerous applications in the field of photodegradation of organic contaminants.

Sacrificial template-assisted iron(III) oxide (Fe2O3) nanofibers have been prepared by simple electrospinning process on the surface of fluorine-doped tin dioxide (FTO) substrate and used as an efficient photoanode in photoelectrochemical water splitting. The Fe2O3 nanofibers with different thicknesses were obtained on FTO substrate by electrospinning of composite polycaprolactone-FeCl3 (0.16 g of FeCl3 in 10 ml of 15 % PCL solution) at different time durations (3, 5, 7, and 9 h). The systematic study on crystallinity, morphology, specific surface area, and charge recombination process of the photoanodes was performed. The high optical absorbance and band-gap energy were observed for the Fe2O3 photoanodes prepared from 5 h electrospun fibers on the FTO surface (E-spin Fe2O3 NFs@FTO/5 h). The Nyqust plots and Mott-Schottky plots of electrochemical impedance spectroscopy measurements were validated that E-spin Fe2O3 NFs@FTO/5 h photoanode suppresses the charge recombination rates, enhances the electron density, and subsequently improves the performance of photoelectrochemical water splitting. The E-spin Fe2O3 NFs@FTO/5 h photoanode has attained the highest photocurrent density of 0.25 mAcm−2 at 1.23 V vs. RHE applied potential. Moreover, the prepared photoanodes were well attributed to the nanofiber morphology with high crystallinity and, thus, increased the optical absorption rate with improved charge transport properties.

Hexagonal phase zinc oxide (ZnO) nanostructures were synthesized via hydrothermal method and annealed at different temperatures viz., 200, 400, 600, 800 and 1000 °C. The prepared nanostructures were characterized by XRD, FTIR, FESEM, HR-TEM, UV-DRS and XPS techniques. The crystallite sizes of the prepared nanomaterails were calculated by Williamson–Hall plots method. The ZnO annealed at 200 °C showed a crystallite size of 18.7 nm while the ZnO annealed at °C showed a 46.2 nm. It is observed that when increasing the annealing temperature the crystallite sizes were increased due to induced growth of crystallites during annealing process. Moreover, the band gaps of the ZnO annealed at different temperatures showed a decreasing trend with increasing annealing temperatures. The photocatalytic performances were studied by analyzing the degradation of methylene blue in an aqueous solution. ZnO annealed at 1000 °C exhibited better photocatalytic activity (94%) due to enhanced crystallinity, comparatively lower bandgap and high oxygen vacancy.

An escalating challenge in condensed-matter research is the characterization of emergent order-parameter nanostructures such as ferroelectric and ferromagnetic skyrmions. Their small length scales coupled with complex, three-dimensional polarization or spin structures makes them demanding to trace out fully. Resonant elastic x-ray scattering (REXS) has emerged as a technique to study chirality in spin textures such as skyrmions and domain walls. It has, however, been used to a considerably lesser extent to study analogous features in ferroelectrics. Here, we present a framework for modeling REXS from an arbitrary arrangement of charge quadrupole moments, which can be applied to nanostructures in materials such as ferroelectrics. With this, we demonstrate how extended reciprocal space scans using REXS with circularly polarized x rays can probe the three-dimensional structure and chirality of polar skyrmions. Measurements, bolstered by quantitative scattering calculations, show that polar skyrmions of mixed chirality coexist, and that REXS allows valuation of relative fractions of right- and left-handed skyrmions. Our quantitative analysis of the structure and chirality of polar skyrmions highlights the capability of REXS for establishing complex topological structures toward future application exploits. M. R. M. and R. R. were supported by the Quantum Materials program from the Office of Basic Energy Sciences, U.S. Department of Energy (DE-AC02-05CH11231). V. A. S., J. W. F., and L. W. M. acknowledge the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award No. DE-SC-0012375 for support to study complex-oxide heterostructure with x-ray scattering. L. W. M. and R. R. acknowledge partial support from the Army Research Office under the ETHOS MURI via cooperative agreement W911NF-21-2-0162. J. Í. acknowledge financial support from the Luxembourg National Research Fund through project FNR/C18/MS/12705883/REFOX. Diamond Light Source, UK, is acknowledged for beam time on beam line I10 under proposal NT24797. K. T. K., S. Y. P., and D. R. L. acknowledge support from the National Research Foundation of Korea, under Grant No. NRF-2020R1A2C1009597, NRF-2019K1A3A7A09033387, and NRF-2021R1C1C1009494. M. A. P. G. acknowledges support by the Czech Science Foundation (Project No. 19-28594X). This research used resources of the Advanced Light Source, a U.S. DOE Office of Science User Facility under Contract No. DE-AC02-05CH11231. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility at Argonne National Laboratory and is based on research supported by the U.S. DOE Office of Science-Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. S. D. gratefully acknowledges a start-up grant from Indian Institute of Science, Bangalore, India. F. G.-O., P. G.-F., and J. J. acknowledge financial support from Grant No. PGC2018-096955-B-C41 funded by MCIN/AEI/10.13039/501100011033 and by ERDF “A way of making Europe,” by the European Union. F. G.-O. acknowledges financial support from Grant No. FPU18/04661 funded by MCIN/AEI/10.13039/501100011033

In this study, we synthesized the visible-light-driven photocatalytic activity of CdO nanowires and g-C3N4/CdO hybrid nanostructure by the hydrothermal method. X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectrometry, and UV–Vis diffuse reflectance spectroscopy studies were carried out to compare the structural, morphological, and optical properties of CdO nanowires and g-C3N4/CdO hybrid nanostructure. Also, we investigated how CdO nanowires and g-C3N4/CdO hybrid nanostructure function as photocatalysts in the photocatalytic oxidation of RhB under visible light illumination, which revealed that g-C3N4/CdO hybrid nanostructure exhibits better photocatalytic oxidation on RhB than CdO nanowires with the first-order degradation kinetics. The prepared g-C3N4/CdO hybrid nanostructure can provide hybridized conduction band or valence band, which facilitates better charge transport and reduces recombination electron-hole charge carriers leading to higher photocatalytic performance. Hence, making hybrid nanostructures such as g-C3N4/CdO can be a potential approach to develop effective photocatalysts for treating effluents discharged from textile and dyeing industries.

Spin transport through magnetic insulators has been demonstrated in a variety of materials and is an emerging pathway for next-generation spin-based computing. To modulate spin transport in these systems, one typically applies a sufficiently strong magnetic field to allow for deterministic control of magnetic order. Here, we make use of the well-known multiferroic magnetoelectric, BiFeO3, to demonstrate non-volatile, hysteretic, electric-field control of thermally excited magnon current in the absence of an applied magnetic field. These findings are an important step toward magnon-based devices, where electric-field-only control is highly desirable., Comment: 34 pages, 4 figures, 9 supplemental figures

We report the synthesis of silver-integrated silica nanostructures using rice hulls and silver chloride through a facile thermal combustion process. The formation of mesoporous silica nanomatrix embedded with silver nanoparticles (SiO2:Ag 5 wt% and SiO2:Ag 10 wt%) was confirmed by XRD, FTIR, EDX, BET, and TEM analysis. Also, the obtained results from the above studies revealed that the concentration of silver ions significantly increases the particle size and number of silver nanoparticles formed in the silica matrix. The electrochemical performance was studied using silver-integrated silica nanostructures as a working electrode in KOH electrolyte. The maximum specific capacitance of SiO2:Ag 5 wt%- and SiO2:Ag 10 wt%-coated electrode was found to be 517 and 580 F/g at current density of 1 A/g. It was also found that SiO2:Ag 10 wt% electrode exhibit an excellent stability with the capacitance retention of 94% than SiO2:Ag 5 wt% (capacitance retention of 85%) after 1000 cycles at a current density of 1 A/g. These results may be attributed to the inherent characteristic of more silver nanoparticles present in the silica nanomatrix in SiO2:Ag 10 wt%. The intrinsic characteristic of rice hull-derived silica nanostructures such as high surface area and mesoporous structure along with the advantage of silver nanoparticles (conductivity) can facilitate the Faradic redox processes at electrode surface which are responsible for the supercapacitive behavior of the prepared silver-integrated silica nanostructures.

The present work reports cauliflower-shaped ZnO nanostructure, and ZnO/multi-wall carbon nanotubes/rGO (ZMG NCs) nanocomposites were synthesized by surfactant-assisted simple hydrothermal method. The structural, morphological, optoelectronic, chemical state, surface properties and its photocatalytic capability were performed using various analytical techniques. The UV–Vis DRS results revealed that optical absorption of ZMG NCs was red shifted into visible region. Furthermore, the photocatalytic removal of methylene blue (MB) dye in aqueous solution was performed using the resulting catalysts, achieves maximum degradation efficiency of 96.3% under UV–Vis light irradiation for 25 min as compared with ZnO/MWCNT (86.01%), ZnO/rGO (79.6%), and ZnO (71.9%). The enhancement in the photocatalytic degradation efficiency of ZMG NCs was attributed to the red-shifted band gap (2.89 eV) and high surface area (45.877 m2 g−1). Moreover, the ZMG ternary NCs possessed good chemical stability, and it has a great potential application for photocatalytic dye degradation and wastewater treatment.

This article is written on behalf of a large number of colleagues, collaborators, and researchers in the field of complex oxides as well as current and former students and postdocs who continue to enable and undertake cutting-edge research in the field of multiferroics, magnetoelectrics, and the pursuit of electric-field control of magnetism. What we present is something that is extremely exciting from both a fundamental science and applications perspective and has the potential to revolutionize our world. Needless to say, to realize this potential will require numerous new innovations, both in the fundamental science arena as well as translating these scientific discoveries into real applications. Thus, this article will attempt to bridge the gap between fundamental condensed-matter physics and the actual manifestations of the physical concepts into real-life applications. We hope this article will help spur more translational research within the broad materials physics community.

Erbium-doped materials can serve as spin-photon interfaces with optical transitions in the telecom C-band, making them an exciting class of materials for long-distance quantum communication. However, the spin and optical coherence times of Er3+ ions are limited by currently available host materials, motivating the development of new Er3+-containing materials. Here, we demonstrate the use of ion implantation to efficiently screen prospective host candidates, and show that disorder introduced by ion implantation can be mitigated through post-implantation thermal processing to achieve inhomogeneous linewidths comparable to bulk linewidths in as-grown samples. We present optical spectroscopy data for each host material, which allows us to determine the level structure of each site, allowing us to compare the environments of Er3+ introduced via implantation and via doping during growth. We demonstrate that implantation can generate a range of local environments for Er3+, including those observed in bulk-doped materials, and that the populations of these sites can be controlled with thermal processing.

The existence of long-range magnetic order in low-dimensional magnetic systems, such as the quasi-two-dimensional van der Waals (vdW) magnets, has attracted intensive studies of new physical phenomena. The vdW Fe_{N}GeTe_{2} (N=3, 4, 5; FGT) family is exceptional, owing to its vast tunability of magnetic properties. In particular, a ferromagnetic ordering temperature (T_{C}) above room temperature at N=5 (F5GT) is observed. Here, our study shows that, by nickel (Ni) substitution of iron in F5GT, a record high T_{C}=478(6) K is achieved. Importantly, pervasive, beyond room-temperature ferromagnetism exists in almost the entire doping range of the phase diagram of Ni-F5GT. We argue that this striking observation in Ni-F5GT can be possibly due to several contributing factors, including increased 3D magnetic couplings due to the structural alterations.