Domain-wall nanoelectronics requires control not only over wall creation but also over the field-off evolution of written configurations. Here, crystallographic anisotropy is used to achieve reversible domain-wall programming in the uniaxial triple-well ferroelectric Sn2P2S6. Single-crystal orientation, macroscopic polarisation, electrostrain, and piezoelectric measurements identify a low-E·Ps geometry in which bulk field-polarisation coupling is strongly reduced relative to a high-E·Ps reference. In situ piezoresponse force microscopy reveals a reproducible wall displacement near a nominal tip bias of 50-100 V, while the topographic channels remain unchanged. Following 100 V writing, field-off recovery was tracked for 90 min in three regions representing (i) isolated domain, (ii) a domain near a larger neighbour, and (iii) domain bridged to the extended matrix. The normalised area trajectories were evaluated using three nested models: an ordinary exponential, a zero-offset Kohlrausch-Williams-Watts (KWW) function without and with a retained-fraction correction. The isolated case exhibits slow stretched recovery (τ = 29.8 min, β = 0.83) without a resolved offset. The neighbouring and bridged cases require retained-fraction KWW descriptions and show faster compressed recovery, with τ = 13.2 and 16.9 min, β = 1.14 and 1.08, and operational retained fractions of 0.065 and 0.111, respectively. Thus, local domain topology governs the recovery rate, kinetic form, and residual written fraction. The study therefore provides a purely geometrical, material-modification-free approach to resolving low-E·Ps and high-E·Ps states for domain-wall dynamics in non-oxide uniaxial ferroelectrics, while a triad of kinetic models is proposed to examine DW field-off relaxation processes.
Dynamic thermal radiation is crucial for modern self-adaptive intelligent thermal management applications. However, they typically require large emissivity change, requirements frequently conflict with the design principles of nanophotonic strategies in integrated composites. Achieving materials with superior thermal emission properties is therefore vital for applications requiring dynamic thermal radiation. Dynamic thermal radiation of materials can be achieved by reasonable structural design and use of phase change materials. In this review, we survey the work that has been based on phase change materials in dynamic thermal radiation, focusing on their classification, realization and various applications in self-adaptive intelligent thermal management. Finally, we highlight current research challenges and propose future directions, such as dynamic thermal radiation performance balancing and artificial intelligence design of dynamic thermal radiation materials.
Graphene has been proposed as an atomically thin barrier for suppressing metal oxidation. However, its effectiveness under combined thermal treatment and oxygen plasma exposure, as well as the mechanisms governing its degradation, remain insufficiently explored. Here, we reveal how defect- and grain boundary-mediated oxygen transport governs the breakdown of oxidation protection in monolayer graphene-coated copper (Cu-Gr). Raman spectroscopy confirms high-quality monolayer graphene with ≈ 3.21. Oxygen-plasma exposure (6, 8, and 10 s) progressively increases the graphene defect density from 2.50 × 1011, 2.80 × 1011, and 3.78 × 1011 cm-2, while reducing the crystallite size from 16.58 to 14.81 and 10.95 nm, thereby activating oxygen transport. SEM reveals localized oxide nucleation at graphene defects and grain boundaries, while cross-sectional TEM confirms localized interfacial oxidation beneath graphene. Arrhenius analysis shows that Cu-Gr exhibits lower oxidation rate constants than bare Cu over 100–300 °C. Graphene effectively suppresses oxidation at 100–200 °C, whereas its protective function degrades at 300 °C. Optical microscopy shows homogeneous CuO formation on bare Cu at 300 °C, whereas Cu-Gr exhibits only localized interfacial oxidation without bulk CuO formation. Cu K-edge XANES and EXAFS further reveal enhanced interfacial Cu-O coordination with increasing plasma exposure while preserving dominant Cu-Cu coordination, confirming oxidation localized at the Cu-graphene interface. Quantitative XPS analysis shows that oxygen-plasma exposure increases the CuO fraction from 63.86% to 69.88% while decreasing from 36.14% to 30.12%. Thermal annealing further accelerates the -to-CuO transformation, increasing the CuO fraction from 74.55% at 100 °C to 83.54% at 300 °C, providing direct chemical evidence for progressive defect-mediated oxidation Overall, these results demonstrate that defect-activated oxygen transport is the dominant mechanism controlling the degradation of graphene-based oxidation protection and define the operational limits of graphene as an atomically thin oxidation barrier for copper.
In transition-metal systems, the Jahn-Teller (JT) framework governs local symmetry and structure-property relations via vibronic coupling between electronic states and lattice vibrations, inducing symmetry-lowering distortions. The static JT model is robust, but becomes insufficient when high average symmetry coexists with local distortions. This necessitates the dynamic JT concept, in which local distortions fluctuate among symmetry-related states and apparent symmetry depends on averaging. Cu-based hybrid perovskites are typically interpreted within the static JT framework; however, their behavior under compression remains incompletely understood as the octahedral environment evolves toward higher symmetry. Here, we study (C8H12N)2CuCl4 using combined high-pressure spectroscopic, diffraction, and computational approaches. The results reveal that pressure-driven JT evolution cannot be captured by a single static model, but proceeds through an intermediate regime at 4-8 GPa. In this regime, the combined results support a dynamic JT contribution, with local Cu-Cl configurations fluctuating despite a strongly reduced static distortion. Spectral broadening, peak convergence, modified d-d absorption and band gap narrowing support this interpretation. Consequently, the material exhibits an apparently simplified average structure, even though spectroscopic response retains pronounced local JT complexity. This work demonstrates that pressure-tuned competition between static distortions and dynamic vibronic averaging provides a framework for interpreting structure-spectroscopy correlations and functionality.
Deep-level defects govern the efficiency, stability, and reliability of power and radio-frequency devices built on wide- and ultrawide-bandgap semiconductors. Deep-level transient spectroscopy (DLTS) and its variants remain the most sensitive electrical probes of these states, resolving trap activation energy, capture cross-section, and concentration with a sensitivity reaching parts in 105 of the doping density. This review consolidates the DLTS-derived defect landscape of the three leading wide-bandgap systems: gallium nitride (GaN), 4H silicon carbide (4H-SiC), and β-phase gallium oxide (β-Ga2O3) within a single comparative framework. We first set out the measurement physics and the method family that has grown around conventional capacitance DLTS: high-resolution Laplace DLTS, current and drain-current DLTS, minority-carrier and optical transient spectroscopy, deep-level optical spectroscopy, admittance spectroscopy, and high-temperature DLTS suited to ultrawide gaps. We then catalog the established defect fingerprints of each material: the carbon-vacancy Z1/2 and EH6/7 lifetime killers and the HK/UK hole-trap series in 4H-SiC; the E1/E2/E3 electron traps, Fe and C-related centres, and yellow-luminescence-linked states in GaN; and the E1/E2/E2*/E3 majority traps, the dominant EC−2.0 eV compensating center, and the gallium-vacancy hole traps in β-Ga2O3. A material-spanning synthesis identifies which assignments are secure, which rest on combined experiment-theory agreement, and which remain contested. We connect specific traps to device pathologies: current collapse and dynamic on-resistance in GaN transistors; lifetime limitation and threshold instability in SiC; carrier removal and radiation response in Ga2O3; and close with the methodological and materials challenges that limit chemical identification of deep levels. An exhaustive, individually referenced table of DLTS-detected defects across the three materials is provided as a reference resource.
Developing lightweight microwave absorbers with strong attenuation capability, broad effective absorption bandwidth, and structural adaptability remains a critical challenge for electromagnetic protection applications. Herein, a hierarchical material–structure design strategy is proposed by integrating cavity-tailored Fe3O4@C particles with MXene-based aerogels and a periodic closely arranged truncated-cone absorber. Fe3O4@C particles with different cavity degrees, denoted as FC-0, FC-15, and FC-120, are synthesized by regulating the hydrochloric acid etching time and subsequently assembled with MXene nanosheets to construct lightweight porous MFC aerogels. The partially hollow Fe3O4@C particles in MFC-15 retain sufficient magnetic Fe3O4 cores while introducing internal air–solid interfaces and local scattering cavities, enabling optimized magnetic–dielectric balance, interfacial polarization, impedance matching, and electromagnetic attenuation. As a result, MFC-15 exhibits a minimum reflection loss of −54.15 dB, and the effective absorption bandwidth can cover 3.28–18 GHz by adjusting the matching thickness. CST simulation further reveals a radar cross-section reduction of 24.5 dB m2 at 9.36 GHz, indicating its potential for practical electromagnetic wave attenuation. Inspired by insect compound eyes, a periodic closely arranged truncated-cone absorber is further designed and optimized to introduce gradient impedance transition, multi-resonance coupling, field localization, and extended propagation pathways. The optimized structure achieves an ultra-wide simulated effective absorption bandwidth of 15.19 GHz and a peak absorption intensity of −53 dB, while the fabricated prototype delivers a measured effective absorption bandwidth of 13.7 GHz. This work demonstrates that coupling tunable cavity engineering with periodic absorber architecture is an effective route toward lightweight, broadband, and high-efficiency microwave absorbing devices.
Self-powered solar-blind ultraviolet (UV) photoelectrochemical (PEC) devices have great potential in underwater optical communication (UOC) due to their resistance to visible light interference. Gallium oxide (Ga2O3) with extremely wide band gap is a natural solar-blind photosensitive material and has been widely used in PEC devices. However, Ga2O3-based PEC devices suffer from low responsivity and poor stability due to photocorrosion at the solid-liquid interface. Particle modification techniques are considered an effective measure to improve the transport path of photogenerated charge carriers and mitigate negative reactions. Here, we constructed a uniformly distributed cobalt tetroxide (Co3O4) nanoparticle modification layer on a Ga2O3 nanopillar arrays via in-situ photodeposition. Beyond serving as a protective layer that shields Ga2O3 from liquid contact and suppresses lattice degradation, Co3O4 nanoparticles also form a staggered type-Ⅱ heterojunction with Ga2O3, which promotes the extraction of photogenerated holes for redox reactions and thus enhances carrier separation kinetics. The response rise time and responsivity of the optimized PEC device are 34.6 ms and 17.27 mA·W-1 which are 4.3 and 1.6 times higher than the original ones. Notably, in a continuous 7200s optical switching test, the photocurrent attenuation degree improved from 67% to 0.3%, exhibits significantly enhanced long-term stability. This significantly outperforms existing reports on Ga-based solar-blind UOC devices. Stimulatingly, a UOC system based on Co3O4@Ga2O3 photoanode achieves high-fidelity, self-powered signal transmission and real-time decoding even in long-term liquid operating environments, providing a foundation for achieving high-performance solar-blind systems.
The performance enhancement of conventional thermoelectric thin films is typically limited by the strong coupling between thermal and electrical transport. To effectively decouple electron and phonon transport, regulating crystallographic orientation to improve carrier mobility has been recognized as a critical strategy for achieving high-efficiency thermoelectric conversion. In this work, by combining radio-frequency magnetron sputtering with a selenization process, the preferred orientation of crystal planes of Ag2Se thin films can be regulated by varying the selenization temperature, which significantly enhances the thermoelectric conversion efficiency of the films. The Ag2Se thin films fabricated using this method simultaneously exhibit nearly parallel () planes, which are favorable for enhancing carrier mobility, and () planes with high charge accumulation, resulting in a power factor of up to 43.34 μW·cm-1·K-2 at room temperature. Furthermore, the proposed device delivers an output power of 3.50 μW and an outstanding power density of 26.37 W·m-2 under a temperature difference of 48.8 K. It can also harvest energy from low-grade waste heat released by the human body and beakers containing hot water, enabling effective thermoelectric conversion even under small temperature differences. This study provides a valuable reference for the design of high-performance flexible thermoelectric thin films for practical applications.
Wide-bandgap (WBG) perovskite solar cells (PSCs) are essential top subcells in all-perovskite tandem solar cells (TSCs), where they provide spectral complementarity with narrow-bandgap bottom subcells. However, the considerable performance losses associated with WBG PSCs remain a major obstacle to the further advancement of all-perovskite TSCs. This review begins with the fundamental design principles of all-perovskite tandem architectures, focusing on subcell configuration and bandgap engineering of WBG perovskites. Particular attention is subsequently devoted to the loss mechanisms governing the key photovoltaic parameters of WBG PSCs, including open-circuit voltage, short-circuit current density, and fill factor. Strategies for mitigating these losses are systematically discussed in terms of crystallization control and interfacial engineering, with emphasis on defect passivation, energy-level alignment, and efficient interfacial charge extraction. The operational stability of WBG perovskites under illumination, electrical bias, thermal stress, and humid conditions is further evaluated, together with representative approaches for suppressing performance degradation. Beyond the individual subcell level, the review examines the remaining device-level challenges of all-perovskite TSCs, particularly optical management in four-terminal architectures and interconnection-layer design and current matching in two-terminal architectures. By integrating recent progress in materials, interfaces, and device engineering, this review provides a comprehensive framework for the continued development of high-performance WBG PSCs and all-perovskite TSCs.
