Reconfigurable Resistive Switching in VO/LaSrMnO/AlO (0001) Memristive Devices for Neuromorphic Computing.

The coexistence of nonvolatile and volatile switching modes in a single memristive device provides flexibility to emulate both neuronal and synaptic functions in the brain. Furthermore, such a device structure may eliminate the need for additional circuit elements such as transistor-based selectors, enabling low-power consumption and high-density device integration in fully memristive spiking neural networks. In this work, we report dual resistive switching (RS) modes in VO/LaSrMnO (LSMO) bilayer memristive devices.

CMOS-Compatible Ultrathin Superconducting NbN Thin Films Deposited by Reactive Ion Sputtering on 300 mm Si Wafer.

We report a milestone in achieving large-scale, ultrathin (~5 nm) superconducting NbN thin films on 300 mm Si wafers using a high-volume manufacturing (HVM) industrial physical vapor deposition (PVD) system. The NbN thin films possess remarkable structural uniformity and consistently high superconducting quality across the entire 300 mm Si wafer, by incorporating an AlN buffer layer. High-resolution X-ray diffraction and transmission electron microscopy analyses unveiled enhanced crystallinity of (111)-oriented δ-phase NbN with the AlN buffer layer.

Anisotropic Properties of Epitaxial Ferroelectric Lead-Free 0.5[Ba(TiZr)O]-0.5(BaCa)TiO Films.

As the energy demand is expected to double over the next 30 years, there has been a major initiative towards advancing the technology of both energy harvesting and storage for renewable energy. In this work, we explore a subset class of dielectrics for energy storage since ferroelectrics offer a unique combination of characteristics needed for energy storage devices. We investigate ferroelectric lead-free 0.

Self-Assembled Au Nanoelectrodes: Enabling Low-Threshold-Voltage HfO-Based Artificial Neurons.

Filamentary-type resistive switching devices, such as conductive bridge random-access memory and valence change memory, have diverse applications in memory and neuromorphic computing. However, the randomness in filament formation poses challenges to device reliability and uniformity. To overcome this issue, various defect engineering methods have been explored, including doping, metal nanoparticle embedding, and extended defect utilization.

Manipulating topological Hall-like signatures by interface engineering in epitaxial ruthenate/manganite heterostructures.

Topologically protected non-trivial spin textures ( skyrmions) give rise to a novel phenomenon called the topological Hall effect (THE) and have promising implications in future energy-efficient nanoelectronic and spintronic devices. Here, we have studied the Hall effect in SrRuO/LaCaMnO (SRO/LCMO) bilayers. Our investigation suggests that pure SRO has hard and soft magnetic characteristics but the anomalous Hall effect (AHE) in SRO is governed by the high coercivity phase.

Thin-film design of amorphous hafnium oxide nanocomposites enabling strong interfacial resistive switching uniformity.

A design concept of phase-separated amorphous nanocomposite thin films is presented that realizes interfacial resistive switching (RS) in hafnium oxide-based devices. The films are formed by incorporating an average of 7% Ba into hafnium oxide during pulsed laser deposition at temperatures ≤400°C. The added Ba prevents the films from crystallizing and leads to ∼20-nm-thin films consisting of an amorphous HfO host matrix interspersed with ∼2-nm-wide, ∼5-to-10-nm-pitch Ba-rich amorphous nanocolumns penetrating approximately two-thirds through the films.

Emergent and robust ferromagnetic-insulating state in highly strained ferroelastic LaCoO thin films.

Transition metal oxides are promising candidates for the next generation of spintronic devices due to their fascinating properties that can be effectively engineered by strain, defects, and microstructure. An excellent example can be found in ferroelastic LaCoO with paramagnetism in bulk. In contrast, unexpected ferromagnetism is observed in tensile-strained LaCoO films, however, its origin remains controversial.

Machine Learning-Enabled Superior Energy Storage in Ferroelectric Films with a Slush-Like Polar State.

Heterogeneities in structure and polarization have been employed to enhance the energy storage properties of ferroelectric films. The presence of nonpolar phases, however, weakens the net polarization. Here, we achieve a slush-like polar state with fine domains of different ferroelectric polar phases by narrowing the large combinatorial space of likely candidates using machine learning methods.

Induced Ferromagnetism in Epitaxial Uranium Dioxide Thin Films.

Actinide materials have various applications that range from nuclear energy to quantum computing. Most current efforts have focused on bulk actinide materials. Tuning functional properties by using strain engineering in epitaxial thin films is largely lacking.

Structural and Optical Properties of High Entropy (La,Lu,Y,Gd,Ce)AlO Perovskite Thin Films.

Mixtures of Ce-doped rare-earth aluminum perovskites are drawing a significant amount of attention as potential scintillating devices. However, the synthesis of complex perovskite systems leads to many challenges. Designing the A-site cations with an equiatomic ratio allows for the stabilization of a single-crystal phase driven by an entropic regime.

Two Birds with One Stone: Prelithiated Two-Dimensional Nanohybrids as High-Performance Anode Materials for Lithium-Ion Batteries.

As an inexpensive and naturally abundant two-dimensional (2D) material, molybdenum disulfide (MoS) exhibits a high Li-ion storage capacity along with a low volume expansion upon lithiation, rendering it an alternative anode material for lithium-ion batteries (LIBs). However, the challenge of using MoS-based anodes is their intrinsically low electrical conductivity and unsatisfied cycle stability. To address the above issues, we have exploited a wet chemical technique and integrated MoS with highly conductive titanium carbide (TiC) MXene to form a 2D nanohybrid.

Superconducting niobium nitride: a perspective from processing, microstructure, and superconducting property for single photon detectors.

Superconducting niobium nitride (NbN) continues to be investigated decades on, largely in part to its advantageous superconducting properties and wide use in superconducting electronics. Particularly, NbN-based superconducting nanowire single-photon detectors (SNSPDs) have shown exceptional performance and NbN remains as the material of choice in developing future generation quantum devices. In this perspective, we describe the processing-structure-property relationships governing the superconducting properties of NbN films.

Reducing leakage current and enhancing polarization in multiferroic 3D super-nanocomposites by microstructure engineering.

Multiferroic materials have generated great interest due to their potential as functional device materials. Nanocomposites have been increasingly used to design and generate new functionalities by pairing dissimilar ferroic materials, though the combination often introduces new complexity and challenges unforeseeable in single-phase counterparts. The recently developed approaches to fabricate 3D super-nanocomposites (3D-sNC) open new avenues to control and enhance functional properties.

Strain Engineering: A Pathway for Tunable Functionalities of Perovskite Metal Oxide Films.

Perovskite offers a framework that boasts various functionalities and physical properties of interest such as ferroelectricity, magnetic orderings, multiferroicity, superconductivity, semiconductor, and optoelectronic properties owing to their rich compositional diversity. These properties are also uniquely tied to their crystal distortion which is directly affected by lattice strain. Therefore, many important properties of perovskite can be further tuned through strain engineering which can be accomplished by chemical doping or simply element substitution, interface engineering in epitaxial thin films, and special architectures such as nanocomposites.

Regulating off-centering distortion maximizes photoluminescence in halide perovskites.

Metal halide perovskites possess unique atomic and electronic configurations that endow them with high defect tolerance and enable high-performance photovoltaics and optoelectronics. Perovskite light-emitting diodes have achieved an external quantum efficiency of over 20%. Despite tremendous progress, fundamental questions remain, such as how structural distortion affects the optical properties.

Proton switching molecular magnetoelectricity.

The convergence of proton conduction and multiferroics is generating a compelling opportunity to achieve strong magnetoelectric coupling and magneto-ionics, offering a versatile platform to realize molecular magnetoelectrics. Here we describe machine learning coupled with additive manufacturing to accelerate the design strategy for hydrogen-bonded multiferroic macromolecules accompanied by strong proton dependence of magnetic properties. The proton switching magnetoelectricity occurs in three-dimensional molecular heterogeneous solids.

Overcoming the Anisotropic Growth Limitations of Free-Standing Single-Crystal Halide Perovskite Films.

It is extremely challenging to grow single-crystal halide perovskite films (SCHPFs) with not only desired transport properties but also large lateral size with much thinner thickness. Here, we report the growth of freestanding single crystal CsPbBr SCHPFs with thickness less than 100 nm and a lateral size close to centimeter for the first time. A new model for growth kinetics (Ψ=Aexp[-(E -E )/(k T)]) is proposed to address the surface energy and temperature effect on the growth rate of ultrathin CsPbBr single-crystal film.

Induced ferroelectric phases in SrTiO by a nanocomposite approach.

Inducing new phases in thick films via vertical lattice strain is one of the critical advantages of vertically aligned nanocomposites (VANs). In SrTiO (STO), the ground state is ferroelastic, and the ferroelectricity in STO is suppressed by the orthorhombic transition. Here, we explore whether vertical lattice strain in three-dimensional VANs can be used to induce new ferroelectric phases in SrTiO:MgO (STO:MgO) VAN thin films.

Ti-Alloying of BaZrS Chalcogenide Perovskite for Photovoltaics.

BaZrS, a prototypical chalcogenide perovskite, has been shown to possess a direct band gap, an exceptionally strong near band edge light absorption, and good carrier transport. Coupled with its great stability, nontoxicity with earth-abundant elements, it is thus a promising candidate for thin film solar cells. However, its reported band gap in the range of 1.

Structural and Optical Properties of Phase-Pure UO, α-UO, and α-UO Epitaxial Thin Films Grown by Pulsed Laser Deposition.

Fundamental understanding of the electronic, chemical, and structural properties of uranium oxides requires the synthesis of high-crystalline-quality epitaxial films of different polymorphs of one material or different phases with various oxygen valence states. We report the growth of single-phase epitaxial UO, α-UO, and α-UO thin films using pulsed laser deposition. Both oxygen partial pressure and substrate temperature play critical roles in determining the crystal structure of the uranium oxide films.

Competing Interface and Bulk Effect-Driven Magnetoelectric Coupling in Vertically Aligned Nanocomposites.

Room-temperature magnetoelectric (ME) coupling is developed in artificial multilayers and nanocomposites composed of magnetostrictive and electrostrictive materials. While the coupling mechanisms and strengths in multilayers are widely studied, they are largely unexplored in vertically aligned nanocomposites (VANs), even though theory has predicted that VANs exhibit much larger ME coupling coefficients than multilayer structures. Here, strong transverse and longitudinal ME coupling in epitaxial BaTiO:CoFeO VANs measured by both optical second harmonic generation and piezoresponse force microscopy under magnetic fields is reported.

Nanoscale magnetization inhomogeneity within single phase nanopillars.

We report observation of a radial dependence in the magnetic anisotropy of epitaxially strained CoFeO nanopillars in a BaTiO matrix. This archetypal example of a multiferroic heterostructure with a self-assembling three-dimensional architecture possesses significant out-of-plane uniaxial magnetic anisotropy. The anisotropy originates from the large magnetostriction of CoFeO and the state of stress within the nanocomposite.

3D strain-induced superconductivity in LaCuO using a simple vertically aligned nanocomposite approach.

A long-term goal for superconductors is to increase the superconducting transition temperature, . In cuprates, depends strongly on the out-of-plane Cu-apical oxygen distance and the in-plane Cu-O distance, but there has been little attention paid to tuning them independently. Here, in simply grown, self-assembled, vertically aligned nanocomposite thin films of LaCuO + LaCuO, by strongly increasing out-of-plane distances without reducing in-plane distances (three-dimensional strain engineering), we achieve superconductivity up to 50 K in the vertical interface regions, spaced ~50 nm apart.