Jamie H. Warner

Magnesium oxide (MgO)-buffered silicon is an effective pseudo-substrate that enables the epitaxial integration of functional oxides on silicon. Its high thermal stability also serves as a good diffusion barrier that prevents silicon migration to the oxide layer and provides both electrical and optical isolation. We report on the process of forming epitaxial MgO thin films on Si(100) by molecular beam epitaxy using a Sr submonolayer to limit bulk Si oxidation even in the presence of oxygen. The films are characterized using x-ray diffraction, x-ray reflectivity, x-ray photoelectron spectroscopy, reflection-high-energy electron diffraction, scanning transmission electron microscopy, and electron energy loss spectroscopy. The in-plane epitaxial relationship is MgO 〈100〉||Si 〈100〉 with a 4:3 coincident site arrangement between the MgO and Si conventional unit cells. The effect of the Sr submonolayer on the band alignment between MgO and Si is also measured and theoretically modeled using first principles calculations.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) typically degrade through atom-by-atom removal under chemical or electron beam stimuli. Here, we report a fundamentally different degradation pathway in CVD-grown monolayer rhenium disulfide (ReS 2 ), whereby the lattice fragments into stable, discrete molecular clusters under electron irradiation and when etched with a 1 M KOH solution. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy reveals the atomic arrangement of these clusters, while single-particle analysis reconstruction resolves their three-dimensional structure with near-atomic precision. Time-resolved imaging demonstrates that both the transfer process and beam-induced effects drive the lattice-to-cluster transformation. These findings reveal an unconventional degradation pathway in ReS 2, distinct from other 2D TMDs, where its molecular-like bonding drives the production of well-defined Re–S clusters, thereby providing a direct link between 2D materials science and transition-metal cluster chemistry.

ABSTRACT Iridium‐containing complex oxides are attractive catalysts for the oxygen evolution reaction (OER) in acidic media, but the link between their structure and long‐term performance remains poorly defined. We synthesize a library of Ir‐containing double perovskites (’ with A = Sr, Ba, and B' = Fe, Co, In, Y, La, Ce, Pr, Nd, Tb) to systematically probe how composition influences restructuring dynamics and steady‐state OER activity. Using surface‐sensitive spectroscopy, electron microscopy, and rotating disk electrode measurements, we show that all compositions converge to a similar intrinsic activity for the OER after restructuring, but do so at different rates. The B'‐site cation dictates dissolution kinetics, with more oxophilic cations showing slower restructuring. These results reveal that while changing the composition of complex Ir oxides has little influence on the intrinsic OER activity of these materials, it has an important effect on dissolution rates and restructuring dynamics, offering a means to engineer catalyst durability under acidic OER conditions.

ABSTRACT Both heterojunction and core–shell photocatalysts have demonstrated promising performance in photocatalytic CO 2 conversions to fuels. However, fundamental knowledge of heterojunctions in core–shell structures is highly desired to facilitate the design of future photocatalysts. By combining advanced experimental characterizations and density functional theory (DFT) calculations, the role of the Cu 2 O@MoS 2 heterojunction in photocatalytic CO 2 conversions to fuels was investigated. We discovered that the charge dynamics and electron transfer properties of Cu 2 O@MoS 2 photocatalysts are altered by the heterojunction and Cu 2 O underlayer due to the electron transfer from Cu 2 O to MoS 2 and the change in CO 2 adsorption strength on the hybrid catalyst surface. Consequently, more electrons can travel to the surrounding liquid environment to be consumed by CO 2 reduction. This study provides experimental and theoretical investigations of the fundamental mechanisms of heterojunction core–shell photocatalysts.

Abstract Batteries consist of complex, layered interfaces, and their performance‐limiting mechanisms are best understood through nanoscale structural analysis of both anodes and cathodes in realistic full‐cell architectures. This has been challenging for liquid‐electrolyte‐based batteries due to limitations imposed by handling liquid electrolytes and size constraints in most high‐resolution electron microscopes, while cryogenic focused ion beam (cryo‐FIB) milling has typically been limited to a single electrode. Here, a full‐cell cryo‐FIB milling process is presented that reveals anode, cathode, and seprator interfaces in a liquid electrolyte cell with a sodium metal anode and Na 0.44 MnO 2 cathode. This full‐cell cryo‐milled battery stack enables visualization of interfaces at both electrodes, allowing characterization of the entire cell while comparing the effects of two solvents, ethlyene carbonat/diethyl carbonate and digylme, in a NaPF 6 salt‐based electrolyte. It is demonstrated that after moderate cycling (10–50 cycles), degradation pathways differ between carbonate‐ and ether‐based electrolytes. Carbonate‐based cells degrade rapidly, driven largely by electrolyte depletion resulting from excessive solid electrolyte interphase (SEI) formation at the anode. In contrast, diglyme‐based exhibit improved cycling stability but ultimately also experience electrolyte depletion, which instead arises from electrolyte degradation at the cathode. These findings provide insight into solvent‐specific degradation mechanisms relevant to future battery development.

Background: Aggression and irritability are common challenges in children with autism spectrum disorder (ASD), often requiring pharmacological management. Divalproex, an anticonvulsant and mood stabilizer, is used off-label for these symptoms, but its effectiveness remains unclear. This systematic review evaluates the efficacy and safety of divalproex in managing aggression and irritability in children with ASD. Methods: A systematic review was conducted following PRISMA guidelines, registered with PROSPERO (CRD420251029754). Searches were performed in PubMed, Embase, PsycINFO, and Web of Science, identifying studies involving children with ASD treated with divalproex, valproic acid, or valproate sodium. Data were extracted on study design, sample size, intervention details, outcomes, and adverse effects. Results: Ten studies met inclusion criteria, comprising three randomized controlled trials, one open-label trial, and six case reports. Intravenous (IV) divalproex demonstrated rapid reductions in aggression, suggesting potential for acute stabilization. However, oral divalproex produced inconsistent results for chronic aggression and irritability. Adverse effects included weight gain, sedation, and behavioral activation, with toxicity risks in polypharmacy settings. Discussion/Conclusion: Divalproex may offer value for acute management of aggression in children with ASD when administered intravenously. Its role in chronic management is less clear, with inconsistent outcomes and notable side effects. Clinicians should prioritize regular serum monitoring and consider alternative options for chronic use. Further research is needed to clarify its clinical role, particularly in diverse patient populations.

Reverse osmosis (RO) has constituted most of the installed desalination capacity in recent decades. Commercial membranes offer excellent selectivity and reasonable productivity. These membranes, however, suffer from several weaknesses that stem from the use of interfacial polymerization as a means of manufacturing. The inability to control thickness, adjust easily to new chemistries, and avoid surface roughness that enhances foulilng propensity are a few of the weaknesses to conventional membrane fabrication. Numerous materials have been proposed as alternatives to polyamide for RO in recent decades. However, in spite of numerous publications on these new materials, it is remarkable to see how none has even come close to succeeding in replacing conventional RO membrane materials in a commercial setting. This is largely because many of these new materials are incompatible with existing membrane manufacturing approaches such as interfacial polymerization. We must be able to process new materials into thin, defect-free films on conventional supports. This is a significant hurdle for new material adoption in membranes today. New manufacturing methods are needed to address the inherent weaknesses of interfacial polymerization for polyamide and the general processing of newly discovered materials into thin film composite membranes for RO and nanofiltration platforms.

Chromium trihalides, like CrCl 3, are part of an emerging class of van der Waals materials that have been showing promise for their magnetic properties. However, CrCl 3 has been produced only by mechanical tape exfoliation, a low yield method, and by liquid exfoliation in organic solvents, with a negative impact on the environment and human health. Here, CrCl 3 was produced for the first time by liquid-phase exfoliation (LPE) in aqueous medium, in the presence of polyvinylpyrrolidone (PVP10) or sodium dodecyl sulfate (SDS), followed by ultrasonication. It was also the first time that CrCl 3 was obtained with nanometric size (<100 nm), and its photothermal, magnetic, and water stability performances were studied. Results showed that CrCl 3 + SDS (zeta potential = −19.9 mV) had better water stability than CrCl 3 + PVP10 (zeta potential = 8.6 mV). CrCl 3 + SDS and CrCl 3 + PVP10 were obtained with a mean particle lateral size of 39.4 ± 15.9 and 65.6 ± 47.4 nm and a mean thickness of 4.4 ± 3.9 and 7.1 ± 5.3 nm, respectively. Both materials revealed a similar ability to convert near-infrared light into heat, showing a temperature increase of 4.7 °C (CrCl 3 + SDS) and 5.8 °C (CrCl 3 + PVP10) after 30 min of irradiation. Results show that the presence of SDS during production leads to a loss of Cl atoms when compared to PVP10, but crystallinity is preserved. Magnetometry measurements show a Néel temperature of 15 K ± 2.0 K for both samples, showing its antiferromagnetism. A Curie–Weiss analysis indicates a ferromagnetic dominant paramagnetic phase due to the positive Curie–Weiss temperatures, with the calculated effective moments as 4.20 μ B ± 0.63 μ B and 3.95 μ B ± 0.49 μ B for CrCl 3 + PVP10 and CrCl 3 + SDS, respectively. These results show that LPE of CrCl 3 with PVP10 or SDS produces 2D CrCl 3, preserving crystallinity and magnetic properties, and demonstrating potential for spintronic applications.

Desalination via reverse osmosis (RO) membrane technology is a preferred solution to the ongoing global challenges of freshwater scarcity. The active separation layer of RO membranes is a polyamide thin film (<200 nm), whose morphology critically influences membrane performance. However, conflicting descriptions of trends between morphology and performance abound in the literature due to the lack of a rigorous morphological description of these membranes. Notably, comprehensive three-dimensional (3D) morphological characterization of these membranes has so far been conducted exclusively under dry conditions, which contrasts with the operational, hydrated state of these membranes. Here, we present, for the first time, characterization of the hydrated 3D nanoscale morphology of polyamide films from commercial brackish water (BW) and seawater (SW) membranes using cryo-transmission electron microscopy (cryo-TEM) tomography. Our findings reveal significant morphological differences between hydrated and dry membranes, resulting in variations in key structural parameters that impact performance. Both SW and BW membranes swell and increase in total volume and thickness upon hydration, with BW membranes exhibiting more pronounced swelling (32% vs 7% in volume and 35% vs 11% in effective thickness), primarily due to the lower degree of cross-linking of BW membranes. Additionally, while the surface area decreases upon hydration for both SW and BW membranes, indicating a smoothing of surface nodules and cavities, surface roughness remains unchanged, suggesting that current roughness measurement methods such as atomic force microscopy do not capture intrinsic morphological features. Overall, this study demonstrates the feasibility of employing cryo-TEM tomography techniques to characterize RO membrane morphology under operation relevant conditions, thus enabling a better linkage between membrane morphology and performance.

Bimetallic heterostructures, including core-shell and Janus configurations, often offer unique electrocatalytic properties compared to monometallic nanoparticles. However, achieving precise control over both elemental composition and spatial arrangement within these structures remains a challenge. Here, an electrosynthesis method is introduced that enables the fabrication of heterostructured bimetallic nanoparticles with precise, independent control of their elemental distribution. By leveraging dual-channel scanning electrochemical cell microscopy (SECCM), the local ionic environment is dynamically modulated in situ, adjusting the deposition bias between channels to achieve selective electrodeposition. This approach allows temporal control over the solution conditions within the SECCM droplet, facilitating the synthesis of multi-layer core-shell nanoparticles with tunable thickness, number, and sequence of layers. This technique is demonstrated with Pt-Cu and Pt-Ni systems, synthesizing arrays of Cu@Pt and Pt@Cu core-shell structures, which are then screened for catalytic activity in hydrogen evolution (HER) and oxygen reduction (ORR) reactions. The high spatial resolution and on-demand control over the composition and structure make this method well-suitable for creating arrays of complex, multi-metallic heterostructures, which is expected to accelerate the discovery of advanced electrocatalytic materials, offering a platform for efficient and scalable electrocatalyst screening.

In the landscape of proton exchange membrane fuel cells (PEMFCs), there is a strong need for durable, low hydrogen crossover membranes that retain high current output and proton conductivity during operation. This study presents the use of UV-Ozone induced defects in graphene to eliminate the proton conductivity penalty commonly associated with traditional crossover mitigation strategies. We report a defect engineered graphene material that demonstrates an increase in hydrogen/proton selectivity of 27%, a decrease in H 2 crossover of 24%, with limited to no impact on current output. Furthermore, we demonstrate a membrane that is 39% more durable than state of the art GORE Select membranes and shows no loss in performance after a 100 h accelerated stress test (AST). This study illustrates the viability of 2D material membranes to sieve between H 2 and H 3 O + in industrial testing conditions and serve as highly scalable and durable fuel cell membranes that represent a significant upgrade over current state of the art membranes for hydrogen fuel cell vehicles and clean energy generation.

Abstract A design of experiments (DoE) approach is applied to the study of nitrogen (N)‐doped carbons prepared via a molten salt templating method using the eutectic salt lithium chloride/potassium chloride (LiCl/KCl) and the precursors sucrose and melamine (N precursor). This approach is used to deconvolute effects from surface composition and porosity on the electrocatalytic performance of N‐doped carbons as oxygen reduction reaction (ORR) electrocatalysts. Additionally, DoE is implemented to reveal the synthesis‐structure‐function relationship for the prepared materials over an entire design space. From this work, it is evident that the N precursor content has the greatest impact on the tunability of material properties (e.g., N‐content, pyridinic N content, surface area, pore size distribution, etc.) followed by pyrolysis temperature and salt mass. Additionally, without adequate porosity (surface area ≥ 500 m 2 g −1 , micropore volume &gt; 0.15 cc g −1 , etc.) and electrochemically active surface area, activity and selectivity for the ORR via N‐functionalization is significantly reduced. Optimization of the studied design space indicates that an N precursor content of 35 wt.%–38 wt.%, pyrolysis temperature ≤ 900 °C, and a salt mass &lt; 15 g would garner the necessary N‐content (∼7–8 at%) and porosity to achieve the most active and selective N‐doped carbon ORR electrocatalysts.

High Resolution Image Download MS PowerPoint Slide Nanopores embedded within monolayer hexagonal boron nitride ( h -BN) offer possibilities of creating atomically thin ceramic membranes with unique combinations of high permeance (atomic thinness), high selectivity (via molecular sieving), increased thermal stability, and superior chemical resistance. However, fabricating size-selective nanopores in monolayer h -BN via scalable top-down processes remains nontrivial due to its chemical inertness, and characterizing nanopore size distribution over a large area remains extremely challenging. Here, we demonstrate a facile and scalable approach of exploiting the chemical vapor deposition (CVD) process temperature to enable direct incorporation of subnanometer/nanoscale pores into the monolayer h -BN lattice, in combination with manufacturing compatible polymer casting to fabricate centimeter-scale nanoporous atomically thin ceramic membranes. We leverage diffusive transport of analytes including size-selective Ficoll sieving to characterize subnanometer-scale and nanoscale defects that manifest as pores in centimeter-scale h -BN membranes, overcoming previous limitations in large-area characterization of nanoscale defects in h- BN. Our approach opens a new frontier to advance atomically thin membranes to 2D ceramic materials, such as h -BN via facile and direct formation of nanopores, for size-selective separations.

surface. The experimentally observed changes in activity and surface structure after cycling are consistent with computational analysis, which shows how metal dissolution may alter the OER activation barriers. Combining experimental and computational insights, this work reveals the effects of metal dissolution on the surface atomic and electronic structure and OER activity and advances our comprehension of metal dissolution dynamics and surface reconstruction, which may have implications for other catalytic processes.

Abstract In alignment with the Materials Genome Initiative and as the product of a workshop sponsored by the US National Science Foundation, we define a vision for materials laboratories of the future in alloys, amorphous materials, and composite materials; chart a roadmap for realizing this vision; identify technical bottlenecks and barriers to access; and propose pathways to equitable and democratic access to integrated toolsets in a manner that addresses urgent societal needs, accelerates technological innovation, and enhances manufacturing competitiveness. Spanning three important materials classes, this article summarizes the areas of alignment and unifying themes, distinctive needs of different materials research communities, key science drivers that cannot be accomplished within the capabilities of current materials laboratories, and open questions that need further community input. Here, we provide a broader context for the workshop, synopsize the salient findings, outline a shared vision for democratizing access and accelerating materials discovery, highlight some case studies across the three different materials classes, and identify significant issues that need further discussion. Graphical abstract

Scalp lacerations represent a significant portion of traumatic wounds treated in emergency settings, presenting unique challenges due to the scalp's high vascularity and tension on closure. This study explores primary closure techniques for scalp defects, focusing on sutures, staples, and the hair apposition technique (HAT). Given the cosmetic and psychological implications of hair loss associated with scalp laceration repairs, effective closure methods are paramount. This systematic review evaluates the efficacy of sutures, staples, and HAT in minimizing hair loss and enhancing cosmetic outcomes. Out of an initial 21530 literature sources, 7 studies were included in this analysis, selected through a comprehensive screening process. Findings suggest that while traditional methods like sutures and staples are widely used, HAT shows promise in reducing complications and preserving hair. The study underscores the importance of selecting appropriate closure techniques to optimize patient satisfaction and overall care quality.

High Resolution Image Download MS PowerPoint Slide Atomically thin 2D materials present the potential for advancing membrane separations via a combination of high selectivity (from molecular sieving) and high permeance (due to atomic thinness). However, the creation of a high density of precise nanopores (narrow-size-distribution) over large areas in 2D materials remains challenging, and nonselective leakage from nanopore heterogeneity adversely impacts performance. Here, we demonstrate protein-enabled size-selective defect sealing (PDS) for atomically thin graphene membranes over centimeter scale areas by leveraging the size and reactivity of permeating proteins to preferentially seal larger nanopores (≥4 nm) while preserving a significant amount of smaller nanopores (via steric hindrance). Our defect-sealed nanoporous atomically thin membranes (NATMs) show stability up to ∼35 days during size-selective diffusive separations with a model dialysis biomolecule fluorescein isothiocyanate (FITC)-Ficoll 70 in phosphate buffer saline (PBS) solution as well as outperform state-of-the-art commercially available dialysis membranes (molecular-weight-cutoff ∼3.5–5 kDa and ∼8–10 kDa) with significantly higher permeance for smaller solutes KCl (∼0.66 nm) ∼5.1–6 × 10 –5 ms –1 and vitamin B12 (B12, ∼1.5 nm) ∼2.8–4 × 10 –6 ms –1 compared to small protein lysozyme (Lz, ∼4 nm) ∼4–6.4 × 10 –8 m s –1, thereby allowing unprecedented selectivity for B12/Lz ∼70 and KCl/Lz ∼1280. Our work introduces proteins as nanoscale tools for size-selective defect sealing in atomically thin membranes to overcome persistent issues and advance separations for dialysis, protein desalting, small molecule separations/purification, and other bioprocesses.

Nanowires composed of a 1:1 stoichiometry of transition metals and chalcogen ions can be fabricated from two-dimensional transition metal dichalcogenides (TMDs) by using electron beam irradiation. Wires fabricated through in situ experiments can be geometrically connected to TMD sheets in various ways, and their physical properties can vary accordingly. Understanding the structural transformation caused by electron beams is critical for designing wire-sheet structures for nanoelectronics. In this study, we report the behavior of nanowires formed inside a monolayer MoS 2 sheet by combining phase-contrast images and large-scale atomistic modeling. We investigate the effect of vacancies on the dynamic evolution of wires, such as rotations with different edge structures and breaking, by considering the interactions between MoS wires and MoS 2 nanosheets. The obtained insights can be applied to other monolayer TMDs to guide the behavior of TMD wires and fabricate favorable geometries for various applications.

• Ag enrichment at grain boundaries induces significant oxidation effects. • Enhanced performance stems from stabilized Cu δ+ species and unique electron transfer. • The CO 2 -to-CH 4 pathway and the sluggish quenching of intermediates are revealed. • Grain boundary oxidation effect on CH 4 conversion is twice that of conventional effects. The authentic active sites of oxide-derived copper (OD-Cu), namely grain boundaries (GBs) and oxidized Cu δ+ species, is still debatable, and their role in governing CH 4 conversion remains unclear. Herein, this study answers these questions using bimetallic catalysts by novel electro-shock strategy with controllable GBs for the oxidization of Cu δ+ species by modulating Ag loading. The Ag enrichment at the GBs facilitates the bonding of oxygen with the uncoordinated Cu atoms, resulting in GB oxidation effect. The obtained CH 4 selectivity is twice that of GBs or nanoalloy effect. The enhanced performance is attributed to the stable Cu δ+ species and unique electron transfer mechanism from GB oxidation structure. Operando attenuated-total-reflection Fourier-transform-infrared-spectroscopy unveils the reaction pathway of CO 2 -to-CH 4 and the sluggish reversible quenching processes of intermediates. Theoretical calculations indicate that the weak *CO adsorption on GB oxidation structure facilitates *CO hydrogenation, promoting CO 2 -to-CH 4 conversion.

Electrocatalytic CO 2 reduction is garnering significant interest due to its potential applications in mitigating CO 2 and producing fuel. However, the scaling up of related catalysis is still hindered by several challenges, including the cost of the catalytic materials, low selectivity, small current densities to maintain desirable selectivity. In this study, Fluorine (F) atoms were introduced into an N-doped carbon-supported single nickel (Ni) atom catalyst via facile polymer-assisted pyrolysis. This method not only maintains the high atom utilization efficiency of Ni in a cost-effective and sustainable manner but also effectively manipulates the electronic structure of the active Ni–N 4 site through F doping. The catalyst has also been further optimized by controlling the F states, including convalent and semi-ionic states, by adjusting the fluorine sources involved. Consequently, this catalyst with unique structure exhibited comparable electrocatalytic performance for CO 2 -to-CO conversion, achieving a Faradaic efficiency (FE) of over 99% across a wide potential range and an exceptional CO evolution rate of 9.5 × 10 4 h –1 at −1.16 V vs reversible hydrogen electrode (RHE). It also delivered a practical current of 400 mA cm –2 while maintaining more than 95% CO FE. Experimental analysis combined with density functional theory (DFT) calculations have also shown that F-doping modifies the electron configuration at the central Ni–N 4 sites. This modification lowers the energy barrier for CO 2 activation, thereby facilitating the production of the crucial *COOH intermediate.

Abstract Point defect qubits in semiconductors have demonstrated their outstanding capabilities for high spatial resolution sensing generating broad multidisciplinary interest. Hexagonal boron nitride (hBN) hosting point defect qubits have recently opened up new horizons for quantum sensing by implementing sensing foils. The sensitivity of point defect sensors in hBN is currently limited by the linewidth of the magnetic resonance signal, which is broadened due to strong hyperfine couplings. Here, we report on a vacancy-related spin qubit with an inherently low symmetry configuration, the VB2 center, giving rise to a reduced magnetic resonance linewidth at zero magnetic fields. The VB2 center is also equipped with a classical memory that can be utilized for storing population information. Using scanning transmission electron microscopy imaging, we confirm the existence of the VB2 configuration in free-standing monolayer hBN.

Given the growing emphasis on energy efficiency, environmental sustainability, and agricultural demand, there’s a pressing need for decentralized and scalable ammonia production. Converting nitrate ions electrochemically, which are commonly found in industrial wastewater and polluted groundwater, into ammonia offers a viable approach for both wastewater treatment and ammonia production yet limited by low producibility and scalability. Here we report a versatile and scalable solution-phase synthesis of high-entropy single-atom nanocages (HESA NCs) in which Fe and other five metals-Co, Cu, Zn, Cd, and In-are isolated via cyano-bridges and coordinated with C and N, respectively. Incorporating and isolating the five metals into the matrix of Fe resulted in Fe-C5 active sites with a minimized symmetry of lattice as well as facilitated water dissociation and thus hydrogenation process. As a result, the Fe-HESA NCs exhibited a high selectivity toward NH3 from the electrocatalytic reduction of nitrate with a Faradaic efficiency of 93.4% while maintaining a high yield rate of 81.4 mg h−1 mg−1. Converting nitrate from waste sources into ammonia provides an effective method for both wastewater treatment and ammonia production. Here the authors report a scalable solution-phase synthesis of high-entropy single-atom nanocage catalysts for efficient nitrate-to-ammonia conversion.

Ferroelectric strontium barium niobate (SrxBa1−xNb2O6 or SBN) is a material with high electro-optic (EO) response. It is currently of interest in low voltage silicon-integrated photonics (SiPh). We have grown strongly textured SBN films with x = 0.65 by radio frequency sputtering on (100)-oriented SrTiO3 substrates where grains with mixed (310) and (001) out-of-plane orientation form. For these mixed orientation films, we observed a maximum effective EO coefficient of 230 pm/V using a transmission EO measurement geometry that is responsive only to the in-plane polarization component coming from the (310)-oriented grains. We also demonstrate that by growing SBN on TiO2-terminated SrTiO3 substrates, we can obtain predominantly (001)-oriented SBN films with out-of-plane polarization. Transmission EO measurements on such (001)-oriented films show a reduced effective Pockels coefficient of 88 pm/V, which is consistent with the overall ferroelectric polarization becoming out-of-plane. This work shows that controlling substrate termination is effective in controlling the grain orientation of SBN films grown on top and that one can readily integrate SBN films on SrTiO3-buffered Si for use in SiPh.

Low-temperature large-area growth of two-dimensional (2D) transition-metal dichalcogenides (TMDs) is critical for their integration with silicon chips. Especially, if the growth temperatures can be lowered below the back-end-of-line (BEOL) processing temperatures, the Si transistors can interface with 2D devices (in the back end) to enable high-density heterogeneous circuits. Such configurations are particularly useful for neuromorphic computing applications where a dense network of neurons interacts to compute the output. In this work, we present low-temperature synthesis (400 °C) of 2D tungsten diselenide (WSe 2 ) via the selenization of the W film under ultrahigh vacuum (UHV) conditions. This simple yet effective process yields large-area, homogeneous films of 2D TMDs, as confirmed by several characterization techniques, including reflection high-energy electron diffraction, atomic force microscopy, transmission electron microscopy, and different spectroscopy methods. Memristors fabricated using the grown WSe 2 film are leveraged to realize a novel compact neuron circuit that can be reconfigured to enable homeostasis.

The ability to scale two-dimensional (2D) material thickness down to a single monolayer presents a promising opportunity to realize high-speed energy-efficient memristors. Here, we report an ultra-fast memristor fabricated using atomically thin sheets of 2D hexagonal Boron Nitride, exhibiting the shortest observed switching speed (120 ps) among 2D memristors and low switching energy (2pJ). Furthermore, we study the switching dynamics of these memristors using ultra-short (120ps-3ns) voltage pulses, a frequency range that is highly relevant in the context of modern complementary metal oxide semiconductor (CMOS) circuits. We employ statistical analysis of transient characteristics to gain insights into the memristor switching mechanism. Cycling endurance data confirms the ultra-fast switching capability of these memristors, making them attractive for next generation computing, storage, and Radio-Frequency (RF) circuit applications.

Batteries utilizing a sodium (Na) metal anode with a liquid electrolyte are promising for affordable large-scale energy storage. However, a deep understanding of the intrinsic degradation mechanisms is limited by challenges in accessing the buried interfaces. Here, cryogenic electron microscopy of intact electrode:separator:electrode stacks is performed and degradation and failure of symmetric Na||Na coin cells occurs through the infiltration of Na metal through the pores of the separator rather than by mechanical puncturing by dendrites is revealed. It is shown the interior structure of the cell (electrode:separator:electrode) must be preserved and deconstructing the cell into different layers for characterization results in artifacts. In intact cell stacks, minimal liquid is found between the electrodes and separator, leading to intimate electrode:separator interfaces. After electrochemical cycling, Na infiltrates into the pore free-volume, growing through the separator to create electrical shorts and degradation. The Na infiltration occurs at interfacial regions devoid of solid-electrolyte interphase (SEI), revealing SEI plays an important role in preventing Na from growing into the separator by being a physical barrier that the plated Na cannot penetrate. These results shed new light on the fundamental failure mechanisms in Na batteries and demonstrate the importance of preserving the cell structure and buried interfaces.

Bimetallic nanoparticles often show properties superior to their single-component counterparts. However, the large parameter space, including size, structure, composition, and spatial arrangement, impedes the discovery of the best nanoparticles for a given application. High-throughput methods that can control the composition and spatial arrangement of the nanoparticles are desirable for accelerated materials discovery. Herein, we report a methodology for synthesizing bimetallic alloy nanoparticle arrays with precise control over their composition and spatial arrangement. A dual-channel nanopipet is used, and nanofluidic control in the nanopipet further enables precise tuning of the electrodeposition rate of each element, which determines the final composition of the nanoparticle. The composition control is validated by finite element simulation as well as electrochemical and elemental analyses. The scope of the particles demonstrated includes Cu-Ag, Cu-Pt, Au-Pt, Cu-Pb, and Co-Ni. We further demonstrate surface patterning using Cu-Ag alloys with precise control of the location and composition of each pixel. Additionally, combining the nanoparticle alloy synthesis method with scanning electrochemical cell microscopy (SECCM) allows for fast screening of electrocatalysts. The method is generally applicable for synthesizing metal nanoparticles that can be electrodeposited, which is important toward developing automated synthesis and screening systems for accelerated material discovery in electrocatalysis.

Moiré superlattices in graphene arise from rotational twists in stacked 2D layers, leading to specific band structures, charge density and interlayer electron and excitonic interactions. The periodicities in bilayer graphene moiré lattices are given by a simple moiré basis vector that describes periodic oscillations in atomic density. The addition of a third layer to form trilayer graphene generates a moiré lattice comprised of multiple harmonics that do not occur in bilayer systems, leading to nontrivial crystal symmetries. Here, we use atomic resolution 4D-scanning transmission electron microscopy to study atomic structure in bilayer and trilayer graphene moiré superlattices and use 4D-STEM to map the electric fields to show subtle variations in the long-range moiré patterns. We show that monolayer graphene folded into an S-bend graphene pleat produces trilayer moiré superlattices with both small (<2°) and larger twist angles (7-30°). Annular in-plane electric field concentrations are detected in high angle bilayers due to overlapping rotated graphene hexagons in each layer. The presence of a third low angle twisted layer in S-bend trilayer graphene, introduces a long-range modulation of the atomic structure so that no real space unit cell is detected. By directly imaging trilayer moiré harmonics that span from picoscale to nanoscale using 4D-STEM, we gain insights into the complex spatial distributions of atomic density and electric fields in trilayer twisted layered materials.

Reclamation of coal fly ash, a legacy waste material, provides an alternative pathway for the recovery of rare earth elements (REEs) while reducing the environmental stresses that stem from traditional mining. The reactive transport processes underlying the recovery of REEs from ash wastes, however, are yet to be fully elucidated owing to the physicochemical complexity of the micro/nanoscale fly ash particles, including the crystallinity of the particulate matrix. In this work, we use transmission electron microscopy to characterize the material properties of ash particles and reveal the impact of crystallinity on the reactive transport processes governing access to and recovery of the encapsulated REEs. Our results show, for the first time, two distinct crystalline structures of REE-bearing aluminosilicate particles: dense amorphous matrices that facilitate the exchange of chemical species through their lattice interstices and porous polycrystalline matrices characterized by connected intraparticle pores and chemical inertness to leaching solutions. Notably, the presence of matrix crystallinity, or the lack thereof, governs the extent of reagents consumed parasitically by secondary reactions with the aluminosilicate matrix. Our work reveals how the variability of crystalline structures of the ash matrices hosting REEs defines the pathways for the recovery of REEs, providing key insights required for the development of targeted recovery processes.

Epitaxial BaTiO3 integrated on Si or Si-on-insulator using off-axis radio frequency sputtering is a promising material platform for building electro-optic modulators based on the Pockels effect. Barium titanate thin films with c-axis orientation have been epitaxially integrated on silicon-on-insulator wafers. They exhibit excellent structural quality with Pockels coefficient (r33) &amp;gt; 130 pm/V and propagation loss &amp;lt;2 dB/cm. Our results show that off-axis sputtered BaTiO3 films yield electro-optic modulation similar to that of high-quality films grown by molecular beam epitaxy and that the material is suitable for implementation of low-power Mach–Zehnder interferometer electro-optic modulators integrated on silicon in a Z-cut configuration.