ACS Applied Electronic Materials最新文献

Scalable preparation of lightweight dielectric absorbers is critical for electromagnetic-interference mitigation; however, many high-performance carbon absorbers require multistep syntheses or high filler loadings that compromise processability and impedance matching. Here, defect-rich nanographitic carbon (D-NGC) is synthesized directly from acetylene/oxygen mixtures by gas-phase detonation, in which the transient high-temperature/high-pressure and rapid-cooling environment drives the formation of curled, wrinkled nanographitic domains with abundant defects and heterogeneous interfaces. When dispersed in paraffin at only 9.09 wt %, D-NGC delivers a minimum reflection loss (RL) of –67.34 dB at 10.12 GHz and an effective absorption bandwidth (EAB, RL ≤–10 dB) of 4.03 GHz at a thickness of 3.01 mm while maintaining a low apparent density of 0.89 g cm^–3. When the thickness is reduced to 2.20 mm, the EAB expands to 5.37 GHz, and the absorption peak is located at 14.42 GHz. Cole–Cole analysis and Kramers–Kronig-consistent distributed relaxation fitting reveal that defect- and interface-associated polarization relaxation dominates dielectric loss in the X/Ku bands, whereas effective conduction loss is mainly confined to low frequencies. Interfacial-reflection and perfect-matching analyses further clarify that high absorption arises from the combined optimization of moderate complex permittivity, attenuation, and impedance matching rather than from maximizing dielectric loss alone. These results identify gas-phase detonation as a rapid, potentially scalable route to defect-engineered nanocarbons and provide a quantitative framework for designing lightweight carbon-based microwave absorbers.

The strong ionic character and inherent non-centrosymmetric nature of two-dimensional (2D) scandium nitride (ScN) suggest a pronounced out-of-plane piezoelectric response, positioning it as a potential candidate for next-generation nano-energy harvesting. However, the extent to which tribologically driven interlayer interactions can modulate its electromechanical performance has not been systematically established. Here, we investigate the tribo-piezoelectric behavior of bilayer ScN using first-principles density functional theory (DFT) calculations. In-plane sliding and out-of-plane compression are systematically introduced to the ScN bilayer to probe variations in potential energy, polarization, charge redistribution, shear strength, induced voltage, and power density. The analysis indicates that interlayer sliding, accompanied by a transition in stacking configuration, promotes a marked enhancement in out-of-plane polarization, suggesting a strong coupling between structural registry and piezoelectric response. Under vertical compression, the system exhibits an energy corrugation range of 4799.12–7138.83 meV and a corresponding shear strength of 11.19–24.89 GPa, reflecting increased interlayer resistance during mechanical deformation. This behavior gives rise to an induced voltage of ∼1.44 V, highlighting the sensitivity of the bilayer to external mechanical perturbations. We proposed a compression–sliding nanogenerator model, which achieved a maximum theoretical output power density of 464.7 mW cm^–2. These findings indicate that controlled interlayer modulation in ScN provides an effective mechanism for enhancing tribo-piezoelectric energy conversion, highlighting its potential in self-powered devices, wearable systems, and miniaturized electronic technologies.

Disordered double perovskites offer a rich interplay between chemical disorder, magnetic frustration, and lattice degrees of freedom, yet the role of the average crystal structure in mediating magnetic transitions remains poorly understood. Here, we report a magnetoelastic lattice-strain anomaly in the B-site-disordered double perovskite NdSrCoFeO_6–δ, investigated by temperature-dependent high-resolution synchrotron X-ray diffraction and heat-capacity measurements. The average crystal structure remains orthorhombic Pnma from 300 to 10 K, with no symmetry-lowering structural transition. However, the lattice metrics display a clear anomaly in the temperature range of the ferromagnetic-like transition, marked by an inflection in the unit-cell volume and an anisotropic change in the thermal expansion behavior. The strongest response occurs along the orthorhombic b-axis, indicating that magnetic correlations are coupled to the octahedral-tilting degree of freedom rather than producing a crystallographic symmetry change. A volumetric strain analysis further reveals a contraction of the unit cell relative to a smooth high-temperature lattice baseline near the heat-capacity anomaly at T_C ≈ 142 K. Notably, weaker lattice anomalies persist up to 235 K, within the previously reported Griffiths-like phase regime, suggesting that the lattice may sense magnetic heterogeneity before long-range order fully develops. These results demonstrate that the average lattice in NdSrCoFeO_6–δ is not a passive host but an active component of the magnetic phase evolution, with implications for understanding magnetoelastic coupling in chemically disordered cobaltite-ferrite perovskites.

Ferroelectric and antiferroelectric hafnium and zirconium oxides have attracted considerable attention for the development of next-generation energy-storage capacitors owing to their high energy-storage density (ESD), high power density, moderately high efficiency (η), and scalability down to the ultrathin limit. Most research on dielectric energy-storage capacitors focuses on antiferroelectric hafnium oxide- and zirconium oxide-based capacitors, while ferroelectric hafnium oxide-based capacitors have been less extensively investigated. This work highlights the enhancement of the energy-storage characteristics of epitaxial ferroelectric orthorhombic lanthanum-doped hafnium oxide-based two-dimensional capacitors by introducing a thin dielectric amorphous alumina capping layer. It is revealed that the inclusion of a dielectric layer influences both the ESD and η of the fabricated capacitors due to the increased depolarization effect resulting from the presence of the alumina layer. The best balance between ESD and η is achieved through the insertion of a 2.3 nm-thick alumina layer, providing an ultra-high ESD of 142 J/cm³, with an η of 69% for an electric field of 7.7 MV/cm. Additionally, the capacitor displays an ESD greater than 120 J/cm³ after 10⁶ cycles and a stable performance up to 120 °C. Therefore, this work foresees the potential of ferroelectric epitaxial hafnium oxide-based capacitors in energy-storage technologies.

Ion migration and defect-assisted nonradiative recombination are major causes of current–voltage (J–V) hysteresis and operational instability in tin-based perovskite solar cells (PSC). In this work, a dynamic ion-migration model was developed for a conventional n–i–p device based on a methylammonium tin iodide (MASnI₃) absorber to investigate the effects of scan rate, mobile-ion density, ionic diffusivity, activation energy, and surface passivation. All reported device responses and passivation-dependent trends were obtained from the proposed simulation framework and interpreted using experimentally relevant diagnostic parameters. At an ion density of 10¹⁶ cm^–3 and a scan rate of 100 mV s^–1, methylammonium chloride (MACl) reduced the hysteresis index from 8.30% to 1.00%, corresponding to 87.9% suppression. Lead(II) chloride (PbCl₂) increased the ion-migration activation energy from 0.35 to 0.50 eV, decreasing the diffusion coefficient from 10^–10 to 3.0 × 10^–13 cm² s^–1. The combined MACl + PbCl₂ treatment provided the broadest low-hysteresis operating window. Passivation also reduced the relative trap density by approximately 75%, increased electroluminescence efficiency from 2.5% to 8.6%, extended carrier lifetime from 1200 to 3500 ns, enhanced mobility from 0.5 to 45 cm² V^–1 s^–1, and increased quasi-Fermi-level splitting (QFLS) from 1.12 to 1.25 V. These findings demonstrate that simultaneous control of ionic defects and interfacial recombination is essential for stable and efficient tin-based PSC.

Flexible microheaters are critical components for localized thermal management in wearable and soft electronic systems; however, achieving efficient electrothermal performance while maintaining multifunctionality remains challenging. Here, we report geometry-engineered porous graphene microheaters fabricated through a single-step maskless laser writing process on polyimide substrates. Finite-element simulations and experimental investigations reveal that heater geometry plays a decisive role in governing current distribution and Joule heating behavior. In particular, smooth-cornered microheater architectures suppress current crowding, resulting in improved current uniformity, reduced resistive losses, and enhanced electrothermal performance. The optimized geometry achieves a maximum temperature of ∼117 °C at 5 V, compared to ∼87 °C for conventional sharp-cornered designs. Furthermore, optimization of laser processing conditions and metal-assisted fabrication produces highly conductive porous graphene with low defect density (I_D/I_G ≈ 0.24) and low sheet resistance (∼10 Ω sq^–1), enabling rapid heating with a maximum ramp rate of ∼13 °C s^–1. Beyond thermal actuation, the same device architecture functions as an intrinsic temperature sensor, exhibiting high linearity (R² ≈ 0.99), a sensitivity of ∼0.069 % °C^–1 over 30–100 °C, rapid response (∼2.1 s), and stable operation under repeated bending. The optimized porous graphene heater also demonstrates efficient deicing performance, achieving complete ice removal within ∼240 s with a heat flux of 115.6 mW cm^–2 and an energy consumption of 27.7 J cm^–2. These results establish geometry and process engineering as effective strategies for enhancing porous graphene microheater performance and provide a scalable platform for integrated thermal actuation and temperature monitoring in flexible electronic systems.

Poly(vinylidene fluoride) (PVDF) combines flexibility, a high dielectric constant, and considerable piezoelectric responsiveness, making it promising for sensing and self-powered systems. Herein, composite nanofibers with a multiphase spatial architecture were fabricated via one-step electrospinning of PVDF and polyurethane (PU) blends. Adjusting the blending ratios induced spontaneous phase separation and thereby tuned the composition of the outer region, resulting in a composition-tunable core−shell architecture. Selective PU removal and XPS surface analysis were used to characterize the composition-dependent outer-region structure. We demonstrate that this structural variation enables the rational design of task-specific applications. At a balanced blending ratio, both components were detected within the surface region. The balanced composition reduced charge loss under high-humidity conditions and enabled sustained water-droplet energy harvesting. Conversely, a PVDF-rich composition formed a PVDF-shell architecture that was directly subjected to external mechanical stress. This configuration enabled efficient stress transfer, generating a maximum power density of 3.04 mW/m² and demonstrating its potential for piezoelectric motion sensing. Ultimately, this strategy provides a composition-tunable approach to addressing the persistent design challenge of balancing environmental stability and piezoelectric output within a single-material system, offering an adaptable framework for task-specific flexible electronics.

Isotopically enriched ¹⁰B₅C neutron absorber layers were combined with α-Al₂O₃ crystals to achieve scintillation-based neutron detection, utilizing the ¹⁰B(n,α)⁷Li nuclear reaction and ionoluminescence induced by the stopping of secondary charged particles as reaction products. The thin ¹⁰B₅C layers were deposited by DC magnetron sputtering on Si wafers. The modified near-surface region of α-Al₂O₃ contained excess oxygen vacancy-related optical centers to enhance the ionoluminescence yield in the scintillator. Neutron absorption and neutron irradiation-induced scintillation measurements were performed with cold neutrons of a 3.4 Å average wavelength. Measured and calculated values agree well for neutron absorption vs the areal density of deposited ¹⁰B atoms. The maximum neutron-to-light conversion efficiency was found at ∼20% neutron absorption for a ¹⁰B₅C layer of 2.5 μm thickness. The measured and calculated relative scintillation yields agree well and show that the maximum neutron detection efficiency is determined by the total amount of ionization energy deposited in Al₂O₃. The net scintillation light yield is a result of the interplay between neutron absorption in ¹⁰B₅C and the degree of penetration of the nuclear reaction products into Al₂O₃. The ionization profiles induced in Al₂O₃ are confined to the ¹⁰B₅C/Al₂O₃ interface; therefore, it is enough to sensitize only a thin surface region of the scintillator to achieve significant enhancement in neutron detection efficiency. This work assigns ¹⁰B₅C as an effective neutron absorber material for small-scale compact solid state neutron detectors with a wide range of possible applications.

Traditional sensor arrays face the trade-off dilemma between distribution density and circuit complexity, while strain sensors suffer from weak circuit stability under flexible deformation. Here, we propose a liquid metal elastomer resonant (LMER) sensor for frequency-domain distributed strain sensing, which employs liquid metal elastomers as the sensing elements and an RLC series circuit as the core component. The sensor enhances frequency selectivity and resonance-response stability by precisely regulating inductance and capacitance parameters, enabling stable and distinguishable resonant-frequency shifts under flexible deformation and thereby achieving efficient conversion from mechanical strain to frequency-domain signals. Experimental results demonstrate that the three LMER sensing units exhibit highly linear resonant-frequency-shift responses (R² > 0.99) within the core compressive strain range of 0–30%, along with low rate dependence (<0.5%) and excellent long-term cyclic reliability, with frequency-response attenuation below 1% after 10,000 cycles. Furthermore, a distributed sensing system is constructed based on the parallel integration of LMER sensors with distinct resonant-frequency windows, enabling spatially distributed strain responses to be discriminated in the frequency domain through a shared signal line. This work establishes a frequency-domain distributed strain-sensing strategy based on LMER sensors, offering a compact and stable route for distributed flexible sensing in applications such as human–computer interaction, soft robotics, and wearable devices.

This work presents a comparative study of heterojunctions based on 6-inch wafers between silicon carbide and silicon (including Si-face of 4H-SiC and Si, and C-face of 4H-SiC and Si) fabricated via low temperature surface-activated bonding performed on the EVG ComBond system. We systematically investigate crystallographic orientation-dependent effects on interfacial structure and rigorously characterize internal stress distributions within wafer-bonded heterojunction structures through advanced analytical techniques. The interfacial layer properties and mechanical bonding strength are quantitatively assessed. For the first time, in situ heating transmission electron microscopy reveals real-time low-temperature recrystallization at the heterogeneous bonding interface. Our results establish fundamental correlations between process parameters and interfacial integrity, providing insights into the physical mechanism of SiC/Si heterostructures using advanced low-temperature wafer bonding technology. These findings provide guidance for the robust development of SiC/Si heterojunctions and highlight their potential for next-generation wafer-level packaging in high-power and extreme-environment electronics.