Enhancing pyroelectric performance is essential for advancing thermal sensing and energy-harvesting applications. This study presents an effective strategy to achieve highly enhanced pyroelectricity in a flexible polyvinylidene fluoride/mica bimorph. Unlike conventional approaches that focus on domain-phase engineering to enhance intrinsic pyroelectric contribution, we engineer a more dominant role for the secondary pyroelectric contribution by a stress-induced shape change that couples to a change in the polarization via the piezoelectric effect. This mechanism is enabled by the favorable combination of a large thermal-expansion mismatch between the polymer (polyvinylidene fluoride) and the ceramic (mica), together with the inherent mechanical compliance of mica's flexibility, which allows interfacial thermal stresses to efficiently generate piezoelectricity. By combining experimental characterization with finite element modeling of the heterostructure's temperature-dependent curvature, interfacial thermal stress is identified as the dominant contributor to the large effects. Direct pyroelectric measurements reveal a highly enhanced pyroelectric coefficient ≈ -359 µC/m2K, more than an order of magnitude greater than that of single-layer polyvinylidene fluoride, highlighting its potential for applications in flexible electronics, thermal sensors, and energy harvesting systems.

In this work, we demonstrate a novel heteroepitaxial lithium cobalt oxide (LiCoO₂)/Pt architecture on flexible mica substrates that simultaneously achieves exceptional catalytic activity, durability, and mechanical flexibility. Through precise control of LiCoO₂ thickness (optimized at 190 nm), we fabricate an electrode exhibiting outstanding oxygen evolution reaction (OER) performance: a low overpotential of 308 mV at 10 mA cm⁻², a Tafel slope of 45 mV dec⁻¹, and remarkable stability with 97% activity retention after 30 hours in alkaline media. Especially, in-situ Raman spectroscopy investigations provide unprecedented insight into the dynamic structural evolution at the electrode-electrolyte interface, suggesting the formation of interfacial Co-O-Pt-like bonding environments. The flexible heterostructure maintains its exceptional performance even after 1,000 severe bending cycles at 5 mm radius (33% strain), demonstrating negligible degradation in linear sweep voltammetry measurements. This exceptional mechanical durability stems from the unique heteroepitaxial growth that prevents delamination under strain. Beyond presenting a high-performance flexible OER electrode, this work establishes several important design principles: (i) the critical role of lattice-matched substrates in strain-tolerant electrocatalysts, (ii) the importance of controlled epitaxial growth for interface engineering, and (iii) the value of in-situ spectroscopic techniques for understanding reaction mechanisms. These findings open new avenues for developing advanced flexible energy materials through heteroepitaxial design strategies.

Abstract The temperature and magnetic field dependences of the resistivity of polycrystalline bilayer manganite La 1.4 Sr 1.7 Mn 2 O 7 are investigated. The system exhibits an upturn in resistivity below 30 K and a metal–insulator transition at T MI = 130 K . Weak charge localization, grain boundary and electron–magnon scatterings contribute to low temperature ( T < T MI ) resistivity, while Mott variable range hopping of carriers governs the high temperature behavior. A wide temperature range ( T < T MI ) magnetoresistance is observed owing to the combined effects of tunneling and colossal magnetoresistance, whereas double-exchange (DE) within bilayers, magnetic fluctuations and incoherent-coherent carrier transition dictate the behavior for T > T MI . Field-dependent resistivity at various temperatures displays a strong correlation with M(H) data, reflecting 3D ferromagnetic (FM), quasi-2D FM, and 2D FM-paramagnetic transitions. Low and high field magnetoresistance underpin the role of spin-polarized tunneling and spin-dependent scattering contributions at low and high temperatures. An empirical relation taking into account grain boundary polarization, electron–magnon scattering, DE and spin-dependent scattering describes the observed field dependent magnetoresistance at different temperatures.

ABSTRACT Orthorhombic ferroelectric gallium oxide ε(κ)‐Ga2O3 holds significant promise for non‐volatile functionality in ultra‐wide‐bandgap electronics, yet achieving scalable epitaxy remains a challenge. This study establishes a quantitative materials‐to‐device framework by mapping the temperature‐pressure landscape of metal‐organic chemical vapor deposition, delineating a phase transformation map from amorphous to ε(κ) and β phases. A narrow stability window for phase‐pure ε(κ)‐Ga2O3 is identified between 560–590∘C and 7–23 Torr. Within this regime, phase boundaries are shown to follow an inverse T‐P trade‐off and an Ostwald step rule pathway. A critical kinetic threshold is established: when the growth rate exceeds ∼11‐12 nm/min, the system bypasses the metastable ε(κ) phase in favor of the thermodynamically stable β phase. At the optimized condition of 570°C, the films exhibit a minimum oxygen‐vacancy fraction of 2.1% and peak c‐axis crystalline coherence (rocking‐curve FWHM = 0.56°), which directly amplifies the ferroelectric response. Positive‐Up‐Negative‐Down (PUND) measurements confirm a switchable polarization of 60 nC/cm2 after excluding leakage contributions. Lateral memristors fabricated from these optimized films deliver an Ion/Ioff ratio of ∼200 and robust synaptic functions, with the spike‐voltage‐dependent plasticity index increasing by 70 percentage points. This work provides a transferable blueprint linking process kinetics to defect chemistry and device‐level performance for ε(κ)‐Ga2O3 ferroelectric memristors.

Flexible high-entropy relaxor ferroelectrics offer a promising route to overcome the long-standing challenges between mechanical flexibility, thermal stability, and electromechanical performance in piezoelectric applications. In this study, we demonstrate the novel van der Waals (vdW) epitaxial integration of a designed high-entropy oxide, Pb(Mg0.15Nb0.3Ti0.05Hf0.25Zr0.25)O3 (PMNTHZO), onto flexible muscovite (mica) and rigid silicon substrates. Through high-entropy engineering, these films exhibit excellent epitaxial crystallinity and a significantly enhanced breakdown electric field (> 4 MV cm−1 on silicon). By exploiting the vdW interfacial sliding on mica to decouple substrate clamping, the PMNTHZO films achieve an exceptionally large effective piezoelectric coefficient (d33, eff ≈ 118 ± 6 pm V−1). PMNTHZO maintains stable polarization switching above 250 °C and exhibits remarkable mechanical durability, surviving a bending radius of 3.5 mm for over 10,000 continuous deformation cycles. Validated by thickness-dependent analyses and fabricated micro-island structures that explicitly confirm the mitigation of the substrate clamping effect on mica, these results establish PMNTHZO as a robust, thermally stable, and highly flexible piezoelectric material, paving the way for next-generation harsh-environment MEMS and wearable sensors.

ABSTRACT Resistive random‐access memory (RRAM) is a promising technology for nonvolatile applications and neuromorphic computing. 2D bismuth oxyselenide (Bi2O2Se) exhibits high air stability, carrier mobility, and process compatibility. Moreover, Bi2O2Se naturally oxidizes into a high‐κ insulating oxide, Bi2O5Se, making it an ideal candidate for fabricating a dielectric layer in RRAM devices with tunable resistive properties. In this study, RRAM devices based on Bi2O2Se/Bi2O5Se bilayer dielectric thin films were epitaxially grown on (001) Nb‐doped SrTiO3 substrates. The devices exhibited an exceptional nonvolatile performance, including an endurance of 3 × 106 pulse cycles, retention exceeding 104 s, and stable multilevel resistance states. Additionally, the synaptic‐like behavior was explored by applying pulses to the devices. High‐resolution in situ transmission electron microscopy and aberration‐corrected scanning transmission electron microscopy were used to examine the bilayer structural evolution before and after electric‐field application. The electric‐field‐driven oxidation of Bi2O2Se was demonstrated, and a new oxygen‐deficient phase was explored during switching. These results established a resistance‐switching mechanism in the Bi2O2Se/Bi2O5Se platform for fast and reliable RRAM and neuromorphic operations.

Resistive random-access memory (RRAM) is considered the potential candidate for next-generation non-volatile memory owing to its simple structure, fast switching speed and high storage density. In this work, we utilize the 2D layered material, Bi2O2Se (BOSe), epitaxially grown on Nb-doped SrTiO3(Nb: STO) substrate as the switching layer for an RRAM device. The Bi2O2Se-based RRAM devices have excellent electrical performance including outstanding endurance exceed 2500 cycles, high on/off ratio over 103, long retention time up to 104 s and fast switching speed within 18 ns. To reveal the resistive switching behaviors, we used the atomic-scale scanning transmission electron microscopy (STEM) to observe the structural transformation in Bi2O2Se. Combining the chemical state analysis by HRXPS and oxygen content by EELS, after electrical measurements, oxygen vacancies increased in the dielectric layer. This study not only revealed the oxygen-ion migration in Bi2O2Se but also proved it to be the promising candidate for RRAM applications.

ABSTRACT Two‐dimensional materials with piezoelectricity and polarization‐enabled electromechanical responses provide a promising basis for multifunctional electronics, including memory devices and neuromorphic computing. In this work, we explore cryogenic physical vapor deposition (cryogenic PVD)–grown TexSe1‐x thin films, a tellurium‐based compound with a tunable bandgap and enhanced non‐centrosymmetry, and examine their polarization‐associated electromechanical characteristics. A 10 nm Te0.9Se0.1 film exhibits a clear switchable electromechanical response with a piezoelectric coefficient d33 of 33 pm/V, together with stable piezoresponse under ambient conditions. Introducing a Se ratio of 0.1 is found to enhance the polarization behavior and domain response while maintaining the crystalline quality of the TexSe1‐x films. Memory devices based on Te0.9Se0.1 show retention beyond 2000 s and remain switchable up to 1000 cycles, with an HRS/LRS ratio exceeding 102 under ± 20 V program/erase pulses when read at a drain voltage of 1 V. In addition, synaptic behavior is demonstrated with 92% image recognition accuracy at low energy consumption, suggesting potential for neuromorphic applications. These results highlight the potential of TexSe1‐x films as a polarization‐enabled piezoelectric semiconductor system for future low‐power memory and computing applications.

High-entropy oxides (HEOs) have emerged as potential candidates for resistive random-access memory (RRAM) owing to their structural robustness and highly tunable electronic configurations. In this study, a transition-metal HEO thin film composed of Ca, Ti, Sr, Ta, Nb, and O was integrated into Au/HEO-based RRAM devices that exhibited a low SET voltage, fast switching speed (30 ns), and long data retention time (104 s). The underlying resistive switching mechanism was uncovered by employing in situ transmission electron microscopy to observe the real-time structural evolution under an electrical bias. A localized monoclinic-to-cubic symmetry transition was observed during the SET process. Energy-dispersive X-ray spectroscopy and electron-energy-loss spectroscopy analyses revealed cationic rearrangements and Ti/Nb redox interactions accompanied by the generation of oxygen vacancies. These results establish the redox-structure-coupled mechanism for understanding resistive switching in complex oxides. In addition, the HEO-based memristors exhibit stable switching characteristics and synaptic plasticity, highlighting their feasibility for next-generation memory and neuromorphic applications.

Progress in 2D memristive technologies is increasingly constrained by a limited understanding of how crystallographic anisotropy governs ion migration and resistive switching. Bi2O2Se offers a compelling model system in which in-plane and out-of-plane devices display strikingly different electrical behaviors, yet the atomic-scale origins of this disparity remain unknown. Here, we engineer orientation-defined Bi2O2Se nanodevices using focused ion beam fabrication coupled with in situ aberration-corrected transmission electron microscopy, enabling simultaneous electrical probing and real-time imaging of structural evolution under bias. Supported by density functional theory (DFT) calculations, we demonstrate that anisotropic migration barriers for O2- and Se2- ions give rise to two fundamentally distinct switching pathways. Vertical fields, constrained by strong interlayer electrostatic locking, lead to localized vertical migration and the formation of a reversible, ordered conductive D-Bi2O2Se phase, producing abrupt, threshold-type switching. By contrast, lateral fields enable long-range ion diffusion, generating extended Bi/Bi4+2nSe3/Bi2O2Se heterostructures through a topotactic sequence with continuously evolving Se concentration, yielding smooth and linear conductance modulation. These results establish the microscopic principles that underpin direction-dependent transport and phase transformation in Bi2O2Se memristors. By revealing how crystallographic orientation dictates functionality, our work provides a mechanistic foundation for the rational design of directionally engineered 2D neuromorphic and memory systems with enhanced versatility and integration potential.

Bismuth oxychalcogenides (Bi2O2X, where X = S, Se, Te) have garnered significant attention recently due to their high electron mobility, air stability, and excellent photoelectric properties. Therefore, precise control and optimization over the properties of these novel quasi-2D materials are crucial for practical applications. In this study, we synthesize epitaxial films of Bi2O2(S,Se) by the monotonous alloying of sulfur (S) and selenium (Se). Our findings reveal that the lattice constants, band gaps, and electrical properties of the films vary according to the elemental composition. Further, we observed an enhanced field-effect mobility of ∼215 cm2/(V s) and an on/off ratio of ∼106 in the Bi2O2(S0.4Se0.6) heterostructures with a Bi2SeO5 (BSO) oxide layer. With these efforts, this work establishes a pathway toward developing novel designs for 2D Bi2O2X materials.

In the transitioning electricity market of China, accurate forecasting of Day-Ahead Electricity Prices (DAEP) is crucial for strategic planning and profit optimization of market participants. It plays a significant role in resource allocation and in enhancing the efficiency of the energy system. DAEP forecasting in complex electricity markets is challenging due to a multitude of factors, including end-user consumption patterns and physical elements like network losses and transmission congestion. Furthermore, DAEP bidding strategies are often entwined with strategic gaming behavior. Motivated by this, we introduce a novel enhanced linear framework designed to optimize the trade-off between preserving historical patterns (the memory function) and extending predictions to new situations (the generalization function) in DAEP forecasting. The framework employs a linear network to capture data trends and Multi-Layer Perceptron networks for the robust extraction of intricate features and generalization. The proposed enhanced linear framework is developed and evaluated using real-world data from 3 geographically distinct power plants in Guangdong, the province with the highest economic scale and electricity consumption in China. Our approach outperforms representative deep-learning methods, including the Long Short-Term Memory model and Transformer models, with improvements of RMSE up to 26.64% and 51.80%, respectively. Additionally, the results reveal that complex models do not always outperform more straightforward ones in real-world markets characterized by extensive interaction and competition. This indicates the proposed framework provides a straightforward but effective method for time-series DAEP forecasting within the competitive electricity markets. Accurate DAEP forecasting can enhance grid security, facilitate optimal resource allocation, and promote the integration of green and low-carbon power sources into the urban energy system.

The growing need for self-powered sensors in extreme environments, such as biomedical implants, industrial monitoring, and deep-sea exploration, has driven interest in triboelectric nanogenerators (TENGs) as efficient energy harvesters. However, the challenge lies in developing a scalable, cost-effective fabrication process that maintains stable performance in water and across a range of varying temperatures. This study presents a surface modification strategy that enables precise modulation of electronegativity through a scalable and straightforward immersion process. Unlike conventional methods that rely on nanostructuring to enhance triboelectric activity, our approach utilizes surface functionalization to chemically anchor elements with varying electronegativities onto the substrate. These strong chemical bonds effectively modify the substrate's electronegativity, thereby enhancing the TENG's electrical output on both sides. The process is scalable beyond A4 size, making it well-suited for roll-to-roll manufacturing. By functionalizing polydimethylsiloxane (PDMS) electrodes with fluorine (-F) and amino (-NH2) groups, we significantly increase the triboelectric potential difference, enhancing charge transfer efficiency. Experimental results demonstrate that the NH2/fluorinert-modified TENG achieves an output voltage of 2.25 V and a current of 40 nA─an output current 600 times greater than that of pristine PDMS/PDMS. Additionally, theoretical simulations confirm a 225-fold increase in triboelectric potential, demonstrating the fundamental impact of electronegativity modulation. The device exhibits stable performance across a temperature range of 25-100 °C, in underwater conditions, following surface functionalization after thermal annealing, and under prolonged mechanical stress. This work represents a major breakthrough in scalable TENG fabrication, bridging laboratory innovation with commercial application. The demonstrated large-area fabrication approach unlocks new possibilities for wearable electronics, industrial sensing, and energy-efficient IoT devices, making self-powered technology more practical and accessible.

High‐entropy silicides (HESs) are promising for applications requiring enhanced mechanical properties. Additionally, their unique design concepts make them valuable in microelectronics. However, current research primarily focuses on macroscopic investigations of chemical characteristics and mechanical properties, with limited discussion on synthesis possibilities, atomic‐scale observations, and diffusion dynamics. Herein, a novel HES, (CrFeCoNi)Si, is synthesized on a high‐entropy alloy, Al0.5CrFeCoNi2, via a solid‐state reaction. The silicidation process is examined using high‐resolution transmission electron microscopy (HRTEM) and in situ TEM. Initially, Ni diffuses into the Si substrate, forming Ni2Si at 400 °C. At 500 °C, binary silicides (Ni2Si, FeSi2, and Co2Si) form, while Al oxidizes to Al2O3. At 600 °C, binary silicides transform into ternary silicides (FeNiSi, CoNiSi, and FeCoSi). At 700 °C, Cr forms CrSi2, which reacts with other silicides to produce orthorhombic (CrFeCoNi)Si. The formation mechanism is analyzed via TEM, X‐ray diffraction, and energy‐dispersive X‐ray spectroscopy. Additionally, silicidation trends and diffusion behaviors are recorded using HRTEM. Resistivity measurements reveal that (CrFeCoNi)Si exhibits the lowest resistivity at 700 °C, confirming the cocktail effect. These findings highlight new HESs, dynamic microstructure variations, and low‐resistivity characteristics, providing insights into developing novel high‐entropy ceramic materials.

Two-dimensional (2D) materials have emerged as one of most promising candidates to meet the demands of beyond-silicon technology. Among 2D semiconductors, Bi2O2Se (BOSe) stands out as a channel material for advanced electronic applications, due to its high electron mobility and the formation of a native high-k dielectric layer. However, the fabrication of p-type 2D BOSe transistors remains challenging. Here, we report an area-selective doping method at low temperatures (~600 K, compatible with back-end-of-line processes) of pulsed laser deposited BOSe thin films, enabling the modulation of their carrier polarity via the introduction of Zn2+ substitutional dopants. Taking advantage of this doping strategy, we demonstrate the fabrication of a 2D vertical p-n homojunction with an on/off ratio in photoresponse of ~106 and planar transistors based on p-doped BOSe homojunctions. Our results help promoting the application of this material system towards the development of the next-generation electronics. Bi2O2Se is a promising 2D semiconductor with high electron mobility and native high-k dielectric layers, but its p-type doping remains challenging. Here, the authors report a low-temperature substitutional doping method to fabricate 2D Bi2O2Se p-n junctions and p-type transistors

Recent developments in resistive switching random access memory (RRAM) have gained significant attention owing to their high‐density storage, low power consumption, and fast switching. RRAM performance strongly depends on its electrode materials. Thus, high‐entropy alloys (HEAs) provide notable advantages owing to their multifunctional properties. This study investigates the resistive switching behavior of an HEA (Cr, Mn, Fe, Co, Ni) top electrode with a ZnO dielectric layer. The device exhibited a large memory window (≈10 7 ), low SET voltage (1.5 V), fast switching (30 ns), superior endurance exceeding 10 6 pulse cycles, and long retention time (10 4 s). In situ transmission electron microscopy (TEM) provided direct observation of filament formation during voltage application. Energy dispersive X‐ray spectroscopy (EDS), atom probe tomography (APT), and electron energy loss spectroscopy (EELS) analyses revealed HEA element diffusion and its role in stabilising the oxygen storage layer during switching cycles. These findings demonstrate the potential of the HEA/ZnO RRAM for next‐generation memory applications with low power consumption and exceptional stability.

This study presents a novel approach for developing flexible Cu(In, Ga)Se 2 (CIGS) solar cells on mica substrates. Leveraging mica's chemical inertness and high‐temperature resistance, we employ a one‐step sputtering deposition process to enable efficient solar cell fabrication. A strategically integrated 50 nm titanium nitride (TiN) layer serves as both an adhesion promoter and a critical enhancer of Mo crystallinity, promoting CIGS grain growth and significantly enhancing device efficiency. With the TiN layer, the device achieves 13.5% efficiency, representing a 2.7% point improvement over the reference sample. The rear‐side modification using a TiN buffer layer enhances device performance by improving film adhesion to mica, increasing back electrode conductivity, promoting defect passivation through increased crystallinity and grain size, and lowering the backside barrier height. Mechanical stability tests confirm the exceptional resilience of CIGS solar cells on mica, retaining approximately 98% of their initial efficiency after 3000 bending cycles at a 5 mm curvature radius. This robustness is attributed to mica's distinctive layered structure with weak van der Waals bonding. These findings highlight the potential of mica substrates to advance flexible photovoltaics by overcoming limitations of metal or polymer‐based substrates. Offering superior thermal stability and mechanical durability, mica paves the way for next‐generation wearable solar technologies.

Ternary metal oxide-based resistive random access memory (RRAM) is becoming increasingly popular in memory systems owing to its excellent characteristics, such as high switching speed and reliable stability. In this study, dielectric layer PbHfO3 (PHO) films were epitaxially deposited on the SrRuO3 (SRO) bottom electrode, and Au was deposited as the top electrode. PHO shows resistive switching properties, with a uniform distribution of low-resistance state (LRS) and high-resistance state (HRS), and a long retention time (over 104 s). The atomic resolution transmission electron microscope (TEM) and scanning transmission electron microscope (STEM) images demonstrate the structural evolution of PHO before and after switching. Electron energy loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS) further confirmed the resistive switching path. The results demonstrate the exploitability of PHO as a promising RRAM material, while the detailed discussion of its switching behavior provides an aspect of the RRAM switching mechanism.

Exploring the physical properties of functional materials in response to reduced-dimensional environments has attracted significant attention. In this study, we focus on the feature of van der Waals gaps in 2D layered silicate mica for intercalation. The van der Waals gaps between mica interlayers can be considered as 2D cavities, confining the growth direction of intercalants and resulting in controlled morphology and the fabrication of well-ordered 3D mesocrystal structures of NiO. In addition to the controlled morphology, Raman spectra further reveal Néel temperature of NiO can be modulated through mechanical bending in this ambient system. Furthermore, the NiO intercalants can be reduced to Ni metal under suitable thermodynamic conditions. This research introduces a strategy to control the intercalant and paves the way for tailoring the properties of nanomaterials for specific applications, establishing the concept of flexible 3D mesocrystals.