ACS Applied Electronic Materials最新文献

The thermal stability of a metal-oxide thin-film transistor (TFT) can be improved by enclosing its channel region within an oxygen-rich local environment and preventing oxygen depletion from its channel region. Specific techniques for maintaining an oxygen-rich local environment include storing oxygen in an adjacent silicon oxide passivation layer, capping this passivation layer with a diffusion-barrier layer to prevent stored oxygen loss to the atmosphere, and incorporating an oxidation-resistant conducting liner beneath the source/drain electrodes to prevent oxygen consumption through electrode reactions. Additional improvements are achieved by maintaining a hydrogen-deficient local environment. These measures are applied to the design and construction of top-gate TFTs with sidewall spacers that act as barriers to the diffusion of both oxygen and hydrogen, thus enhancing the thermal stability of the transistors.

The growing demand for advanced, personalized wearable health monitoring technologies has driven the development of innovative fabrication methods for flexible electronics. Here, we present electrically conductive 3D-printed piezoresistive metastructure lattice sensors combining structural programmability with tunable electromechanical performance. Leveraging high-resolution stereolithography, metastructure lattices are fabricated with microscale precision, offering design freedom to orthogonally tune mechanical stiffness and deformation through microstructural design. Piezoresistive functionality is imparted via two complementary coating strategies─titanium carbide (TiC) ink dip coating and oxidative chemical vapor deposition (oCVD) of doped polypyrrole (PPy), representing contrasting wet and dry processing routes. These coatings yield distinct interfacial architectures and sensing mechanisms: microcrack-mediated piezoresistivity in TiC-coated lattices and continuous, positive piezoresistivity in conformal oCVD PPy coatings. Both versions achieved good gauge factors (12–13), broad detection ranges (up to 180 N), and excellent cyclic repeatability under both low (0.2 N) and high (90 N) cyclic compressive forces (<5% variation in output). The applicability of these sensors was demonstrated through real-time human gait monitoring with monolithically integrated shoe insoles, underscoring their potential in wearable technology. This study highlights the effectiveness of combining advanced manufacturing techniques with conductive coatings to develop mechanically robust and sensorized wearable devices for applications in healthcare and rehabilitation.

Wide-bandgap (WBG) semiconductors are increasingly investigated for optoelectronic applications requiring stability under harsh electrical and radiation conditions. Among them, 4H-SiC, with its high thermal conductivity, strong radiation tolerance, and large critical electric field, is particularly attractive for ultraviolet (UV) and X-ray sensing. In this work, Ni/4H-SiC Schottky barrier diodes (SBDs) were fabricated and comprehensively examined through electrical, defect, optical, and radiation-response analyses. Forward current density–voltage (J–V) characteristics revealed efficient carrier transport, while reverse bias operation demonstrated a breakdown voltage (BV) exceeding 1 kV. Deep-level transient spectroscopy (DLTS) identified two dominant defect states, Z_1/2 (E_C-0.664 eV) and EH_6/7 (E_C-1.54 eV), governing charge transport and leakage behavior. Under UV illumination, the devices exhibited a responsivity of 0.13 A/W and external quantum efficiency (EQE) of 64.8% at −5 V, with visible-light rejection ratios >10³. X-ray testing across dose rates from 0.1 to 3.8 mGys^–1 confirmed linear photocurrent scaling, while high-energy radiation measurements spanning diagnostic (∼100 kVp) to therapeutic (6–15 MV) X-rays and electron beam (6–20 MeV) demonstrated stable charge collection and reproducible response (RSD < 10%). These results confirm the strong radiation hardness and electrical stability of Ni/4H-SiC SBDs, highlighting their potential for dual-mode UV and high-energy radiation detection in environments where ionizing radiation or high-voltage stress limit the use of conventional semiconductors.

Scaling of accumulation-mode amorphous indium–gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) is increasingly important but seems not easy with a decreased cell size. It is because oxygen-vacancy donors may uncontrollably shorten channel length (L_ch) by a lateral extension (2ΔL) during an n⁺ source/drain (S/D) forming process, causing short-channel effects (SCE). A minimum L_ch guideline is thus necessary based on ΔL estimation. Here, industry-fabricated a-IGZO TFTs with nominal channel lengths of 2.5 to 10 μm were analyzed to extract an effective length, L_eff (≡ L_ch–2ΔL). The threshold voltage (V_th) of our a-IGZO TFTs has rarely shifted until L_ch is reduced to ∼3 μm; however, further scaling to L_ch = 2.5 μm, the V_th appears to drastically shift to a negative voltage. Concomitantly, serious drain-induced barrier lowering (DIBL) is observed for devices with an L_ch of 2.5 μm. We attribute such SCE features to 2ΔL-reduced channel length, L_eff, because an estimated 2ΔL appears over 1.5 μm. Finally, through experiments and Poisson’s equation treatment for incipient accumulation, we first suggest a practical L_eff guideline that enables reliable device operations: minimum L_eff = ∼0.96 μm and a nominal L_ch ≥ 3 μm.

While bismuth telluride (Bi₂Te₃) demonstrates excellent thermoelectric performance in p-type systems, its n-type variants are limited by the inherent conductivity-thermal conductivity trade-off. Here, we employ a dual-doping strategy that incorporates the rare earth element cerium (Ce) and antimony (Sb) to simultaneously optimize the electrical and thermal transport properties of n-type Bi₂Te₃. We demonstrate that Ce and Sb codoping serve as an effective electronic modifier, converting Bi₂Te₃ to an n-type conductor while suppressing bipolar conduction through dynamic carrier concentration tuning, achieving an enhanced peak figure of merit (zT) of ∼0.93 at 473 K in Bi_2–x$(\mathrm{CeSb}{)}_{2x/3}$Te₃ (x = 0.05) through improved power factor optimization. Moreover, Sb codoping not only enhances the carrier mobility through strain compensation but also significantly reduces the lattice thermal conductivity to 0.37 W m^–1 K^–1 at 480 K through synergistic mass fluctuation and strain field phonon scattering. The combined effects yield a 63% enhancement in zT compared to conventional In–Sb-doped systems. Importantly, this performance enhancement is achieved through a scalable synthesis process that maintains phase purity and materials design with structural stability. As a result, the optimized Bi_1.95(CeSb)_0.033Te₃ not only exhibits a higher peak zT value but also maintains high performance across both wearable (ΔT < 100 K) and industrial waste-heat recovery (400–500 K) temperature ranges. This work presents an approach for active strain engineering in the development of high-performance thermoelectric materials, surpassing traditional doping methods.

Gallium oxide (Ga₂O₃) is a solar-blind photodetector material widely used in people’s daily lives and the field of national defense due to its wide and direct band gap, excellent chemical stability, and good thermal conductivity. However, vacancies of Ga and lattice O atoms in the film significantly degrade device performance. Here, high-quality β-Ga₂O₃ thin films were grown on MgO and Al₂O₃ substrates by pulsed laser deposition (PLD) method. The microstructure and chemical composition were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that Mg in the MgO substrate diffuses into the β-Ga₂O₃ thin film, while atoms in the Al₂O₃ substrate do not diffuse. The diffused Mg will suppress the loss of O, which can increase the proportion of lattice O. Photodetector performance measurements reveal that due to the diffusion of Mg, the β-Ga₂O₃ photodetector grown on MgO substrate has higher photocurrent (6.03 × 10^–5 A) and detectivity (1.2 × 10¹³ Jones) at a response wavelength of 254 nm. Importantly, the responsivity and external quantum efficiency (EQE) of the heteroepitaxial β-Ga₂O₃/MgO film-based photodetector are as high as 7.94 A/W and 3900% which are more than 25 times higher than the photodetector based on the β-Ga₂O₃/Al₂O₃ and are one of the best values of β-Ga₂O₃ based photodetectors at present. Our findings shed light on applying high-performance solar-blind photodetectors and related optoelectronic devices.

Water resources, as an environmentally friendly and renewable energy source that does not emit greenhouse gases or other pollutants, have driven the development of triboelectric nanogenerators (TENGs) for liquid-based energy harvesting into a significant research and application trend. Compared to solid–solid TENGs, solid–liquid TENGs offer enhanced durability and stability by mitigating issues related to material wear and performance degradation. A single-electrode GaN-based solid–liquid triboelectric nanogenerator was designed to investigate the energy conversion mechanisms of droplet interactions with gallium nitride under different contact modes, including dripping, sliding, and jetting. The study systematically analyzed the effects of droplet motion mode, flow rate, volume, and surface inclination angle on the output performance of the GaN-based solid–liquid TENG. By adjusting the water flow rate, droplet volume, and salt solution concentration, we effectively optimized the output performance of the TENG. The GaN-based solid–liquid TENG utilizing a salt solution exhibited the highest output current, demonstrating the enhancement of charge separation due to the increased ion concentration in the droplets. Furthermore, rectification circuit experiments validated its capability to power low-power electronic devices such as LEDs and digital watches. This research provides a theoretical foundation for the application of GaN-based solid–liquid TENGs and the advancement of solid–liquid interface energy harvesting technologies.

Flexible strain sensors based on hydrogel materials have attracted considerable interest for their potential in human motion detection, human–machine interaction, and electronic skin. However, traditional hydrogels suffer from limited mechanical performance and severe dehydration, which greatly hinder their practical application in wearable electronics. In this study, a P(DMA-co-AM)/LiCl organohydrogel with exceptional mechanical strength, water retention, and adhesion and sensing properties was developed via one-step ultraviolet (UV)-initiated copolymerization using acrylamide (AM), N,N-dimethylacrylamide (DMA), and lithium chloride (LiCl) in a water–glycerol (Gly) binary solvent system. The introduction of DMA significantly increased the cross-linking density, resulting in a 202% improvement in tensile strength compared to PAM-based organohydrogels. Simultaneously, the incorporation of Gly endowed the organohydrogel with superior water retention, allowing it to maintain excellent flexibility and stretchability even after 8 days of ambient exposure. In addition, the organohydrogel exhibited excellent adhesion (48.61 kPa on copper) and outstanding sensing performance, including high sensitivity (gauge factor (GF) = 3.09), rapid response and recovery (40 and 30 ms), and stable signal output. These features enabled the precise detection of human motion. Furthermore, the organohydrogel-based strain sensor was successfully applied to a sitting posture feedback device and a smart glove for robotic arm control, demonstrating promising prospects for wearable health monitoring devices and human–machine interaction.

Solar-blind ultraviolet (SBUV) optical communication system leverages atmospheric ozone absorption to fulfill low background noise, enabling high anti-interference and security in complex environments, which has gradually attracted widespread attention. Gallium oxide (Ga₂O₃) as an ultrawide bandgap semiconductor possesses excellent physicochemical stability and electron mobility, making it an ideal choice for photodetectors in SBUV communication systems due to its intrinsic spectral alignment with the solar-blind spectrum. Nevertheless, high-concentration oxygen vacancy defects and deep intrinsic acceptor levels, respectively, constrain conventional Ga₂O₃-based photodetectors’ responsivity and block homojunction formation via p-doping. Furthermore, externally biased metal–semiconductor-metal structure devices pose challenges in attaining miniaturization and integration simplicity. To address these constraints, this study employed plasma-enhanced chemical vapor deposition combined with spin-coating processes to fabricate an annealing-optimized β-Ga₂O₃/Lu₂O₃ heterojunction photodetector with a precisely modulated oxygen vacancy concentration. The 650 °C-annealed detector realized a low dark current, a 5.1 × 10³ photo-to-dark current ratio, and a 7.07 × 10¹¹ Jones detectivity under 254 nm illumination at 0 V. First-principles calculations corroborated that carrier transport across the heterojunction interface is governed by a type-II band alignment. Significantly, a high-fidelity solar-blind ultraviolet communication system using a β-Ga₂O₃/Lu₂O₃ heterojunction detector achieved accurate baseband transmission via on–off keying modulation. The present work supplies a key foundation for the design and fabrication of subsequent-generation self-powered SBUV optical communication systems.

Inverted perovskite solar cells (PSCs) have garnered significant attention in the photovoltaic industry due to their exceptional environmental stability and compatibility with scalable manufacturing. Recently, electrodeposition has emerged as a perovskite fabrication strategy, offering distinct advantages, such as simplified processing, cost-effectiveness, and large-area compatibility. However, existing research predominantly focuses on conventional structural configurations, while the exploration of electrodeposition for inverted PSCs remains in its infancy with unclear mechanistic insights and performance optimization pathways. Addressing this gap, we developed a synergistic electrodeposition approach to fabricate inverted PSCs in air. The PbO₂ film was electrodeposited on the nickel oxide/indium tin oxide (NiO_x/ITO) substrate; then the hydroiodic acid (HI) was used to convert the electrodeposited PbO₂ to PbI₂, followed by reacting with FAI to form perovskite films. This sequential approach effectively eliminates byproduct formation during the direct reaction between the organic halide and PbO₂. Moreover, the introduced methylammonium bromide (MABr) additive can reduce pinhole density, optimize film quality, strengthen light absorption, and suppress defect density in the electrodeposited perovskite film. Thereby, the resultant champion device achieved a power conversion efficiency of 11.05%, representing a 112.9% enhancement compared to nonoptimized devices (5.19%).