ACS Applied Electronic Materials最新文献

Atomic layer deposition (ALD) of gate dielectrics on two-dimensional transition-metal dichalcogenides (2D TMDs) is challenging due to their chemically inert surfaces. Although various surface pretreatments can form nucleation sites to facilitate the precursor adsorption, preserving 2D TMDs during the pretreatments and maintaining gate stack quality with the weak 2D TMD/dielectric interface become the main concerns. In this work, we combine physisorbed-precursor-assisted (PPA)-ALD to minimize damage to 2D TMDs with a second interfacial layer for performance enhancement. Ultrathin GdAlO₃ interlayers are integrated into 2D TMD gate stacks with PPA-ALD AlO_x seeding layers and HfO₂ top dielectrics. Further, 1-nm-thick and pinhole-free GdAlO₃ can be deposited on AlO_x-seeded monolayer (1L) WS₂ by ALD at 250 °C. The material properties of 1L WS₂ are preserved, as confirmed by Raman spectroscopy. After the GdAlO₃ layer insertion, 1L MoS₂ dual-gate (DG) field-effect transistors (FETs) show improved subthreshold swing (SS), field-effect mobility, and I_d–V_g hysteresis without compromising the capacitance-equivalent thickness (CET). The proposed strategy is wafer-scale compatible and extendable to the future nanosheet gate-all-around structures.

The need for wearable electronics has remarkably increased due to the fast development of flexible tactile sensors with the unique capability of responding to external pressure stimuli while maintaining a high degree of deformability. To meet the practical wearable sensing requirement, outstanding sensitivity and a wide detection range are always highly desired. Herein, we report the design and fabrication of a flexible iontronic tactile sensor based on a stretchable silver nanowire (AgNW)/Ecoflex composite film with a sandpaper-roughened surface as the electron-conductive electrode and a porous polyurethane (PU)/poly(vinylidene fluoride) hexafluoropropylene copolymer (PVDF)/1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF₄]) composite foam as the ion-conductive electrolyte through a facile dip-coating method. Because of the supercapacitive sensing mechanism and the surface and internal microstructures, an ultrahigh sensitivity of 422.22 kPa^–1 and a maximum wide detection range of 80 kPa are simultaneously achieved after thorough compositional and structural optimization. Toward practical wearable sensing applications, the developed iontronic tactile sensor is demonstrated to be capable of detecting various subtle and large pressures caused by different parts of the human body, such as wrist pulse, swallowing, speaking, and bending of the finger, wrist, and elbow. The proposed material and structure strategy would provide a concept and methodology for the development of sensors with excellent performance.

Surface termination and defects of metal oxide semiconductors are crucial in the process of gas adsorption–desorption and signal transduction, thereby determining their sensing performance. Herein, a facile solvent-assisted surface engineering strategy was demonstrated to synthesize anatase TiO₂ nanosheets (TNS) for an ultraviolet (UV) light-activated isopropanol (IPA) gas sensor. Surface-fluorinated TiO₂ nanosheets (F-TNS) were first synthesized by the hydrofluoric acid-assisted hydrothermal method and followed by hydrothermally treating in Na₂S solutions with different concentrations. The effect of the progressive removal of fluorides was discussed in detail based on X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), and in situ Fourier transform infrared (FTIR) spectroscopy analyses. Compared with F-TNS, the chemiresistive sensor based on the TNS with a trace amount of fluorine exhibited a 324% increase in the sensitivity to 50 ppm of isopropanol at 50 °C under UV irradiation (λ = 365 nm, 30 mW/cm²), while it exhibited a 45% decrease in the recovery time. The enhanced isopropanol sensing performance could be attributed to the high surface area, rational surface terminations, oxygen vacancies, and UV photoexcited charge carriers, which further modulate the surface reaction and charge transfer. These findings offer a facile strategy for the rational design of oxide-based sensing materials, which help in understanding the function of surface terminations and defects in gas sensing.

Mimicking the human brain to achieve neuromorphic computing holds promise in the field of artificial intelligence (AI). Optoelectronic synapses are regarded as the crucial foundation stone in neuromorphic computing due to their capability to intelligently process optoelectronic input signals. Herein, two donor–acceptor (D–A)-type metallopolymers, P-Cu and P-Zn, containing porphyrin moieties are designed and synthesized, which are utilized as a resistive switching layer for preparation of memristors. The resulting memristors exhibit significantly enhanced electrical characteristics, displaying a high ON/OFF ratio, a low threshold voltage (V_th), and superior cycle-to-cycle reproducibility. This enhancement is attributed to the formation and dissociation of charge transfer (CT) states induced by inserted metal ions. Importantly, the P-Cu-based memristor demonstrates the capability to co-modulate optoelectronic signals, effectively emulating versatile synaptic functions of the nervous system. These functions include excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), short-term plasticity (STP), long-term plasticity (LTP), transition from short-term memory (STM) to long-term memory (LTM), and learning-experience behavior. Moreover, multiple Boolean logical functions were successfully implemented using the paired stimuli of electrical pulses. The neuromorphic computing function was also proven through pattern recognition, achieving a recognition rate of up to 86.08% for handwritten digits. This study offers a potent approach for developing multifunctional artificial synaptic devices and artificial neural network platforms and opens up the innovative application of metallopolymers in the fields of optoelectronics and AI.

The utilization of sensors has become indispensable in the advent of an intelligent era characterized by artificial intelligence, 5G communication, big data, and other cutting-edge technologies. Traditional sensors require external power sources or batteries, resulting in a complex sensing system that does not promote the development of sustainable and environmentally friendly applications for health monitoring. In recent years, the electrical output and stability of piezoelectric, triboelectric, thermoelectric, and hybrid nanogenerators have been significantly improved, enabling their widespread role in the development of self-powered sensors. The sensors are capable of performing sensing tasks by converting their own energy, thereby obviating the need for an external power supply. In this paper, we initially explore the operating mechanisms, device materials, and structures of diverse nanogenerators and evaluate their output efficacy. Subsequently, we showcase the latest advancements in self-powered sensor systems, spanning various fields such as biomedical and healthcare, wearable devices, sound monitoring, smart vehicles, environmental monitoring, and smart cities. The paper also explores the future potential of self-powered sensor systems, in addition to discussing their practical applications.

Realizing energy-efficient devices with sustainable and independent operation is a large challenge for next-generation photodetection systems in various environments. In this study, we present a high-response and fast-speed ultraviolet photodetector (UV PD) based on the p-AlGaN/AlN/n-GaN nanowires (NWs) heterojunction, which could operate at a 0 V bias for underwater photodetection through the photoelectrochemical (PEC) process. Compared to the UV PD without AlN insertion, the detection performance would be increased to 3–5 times for underwater solar-blind UV detection under the effect of heterostructure band engineering to prevent carrier drift and recombination at 0 V bias under 255 nm illumination. Furthermore, the photoresponsivity and response speed can be further improved by a surface modification strategy to adjust the carrier transport between the nitride semiconductor and electrolyte. These promising results lay a solid foundation for the development of III-nitride high-efficiency, self-powered PEC photosynthesis devices in the future.

Flexible pressure sensors have great application prospects in the fields of human–computer interaction and wearable electronic devices. Nowadays, the emergence of planar capacitive pressure sensors composed of an interdigital electrode has solved the problem of mechanical mismatch between the electrode layer and the dielectric layer during packaging and further realizes the miniaturization and thinness. However, there are few reports on whether adjusting the height of the interdigital electrode can improve the sensitivity of the sensor. This paper proposes a strategy based on dispensing technology to improve the performance of a capacitive pressure sensor by adjusting the height of the interdigital electrode. The results show that the optimal height of the interdigital electrode is 1.3 mm. On this basis, increasing the number of fingers of the interdigital electrode can also expand the sensitivity and detection range of the sensor. In order to further improve the performance of the sensor, we doped barium titanate with a high dielectric constant in the dielectric layer and introduced the pyramid microstructure. The test results show that our sensor has high sensitivity (0.6275 kPa^–1, ≤1 kPa), wide detection range (0.5–166 kPa), fast response time (120 ms), and good stability after 10,000 cycles. In addition, the sensor can be applied to various pressure detection scenarios such as finger pressing, human joint motion detection, and grasping object detection. Meanwhile, we also constructed a 3 × 3 pressure sensor array to identify the distribution of the spatial pressure. This work provides a solution for preparing high-performance capacitive pressure sensors using an interdigital electrode, which has great application prospects in the field of intelligent wearables.

The fabrication of advanced graphene/metal-mesh hybrid transparent electrodes (TEs) suitable for ultraviolet (UV)-range optoelectronic applications is reported herein, employing UV–ozone treatment. The UV–ozone treatment of transferred graphene is adopted to simultaneously enable oxidation doping and taint removal from the graphene surface and obtain the supplementary benefit of optical transmittance enhancement. Furthermore, the changes in the physical and chemical properties of graphene under different UV–ozone-treated times were characterized using Raman, X-ray/UV photoelectron spectroscopy, Hall measurements, and the transmission line method. Subsequently, hybrid structures combining various UV–ozone-treated graphene samples with a metal-mesh were tested as TEs in gallium nitride-based 375 nm near-UV light-emitting diodes (LEDs). Results indicate a noteworthy enhancement in light output power: a 48.3% increase relative to an untreated LED and an 18.3% increase compared to a conventional indium tin oxide (ITO)-based LED, particularly after 300 s of UV–ozone treatment. The present study provides a practical approach to overcome the limitations of existing ITO TEs for UV applications, thereby facilitating the future commercialization of graphene-based optoelectronic devices.

The circularly polarized state of light can carry encoding information through polarization modulation and structural information from the emitter or propagation medium. Therefore, the detection of the polarization state of light is a central function in various applications. One of the concise strategies is to transform left- and right-handed circularly polarized light (CPL) directly into distinguishable electronic signals using chiral structured materials. In this study, chiral films of β-In₂S₃ vertical nanosheet arrays are successfully grown using a facile solvothermal route. Chirality originates from the distortion of nanosheets with left or right-handedness controlled by the introduction of l-/d-cysteine as chiral inducers. Circularly polarized photodetectors based on chiral β-In₂S₃ films are fabricated. They exhibit good performances with a responsivity (R) of 8.0 A/W, photodetectivity (D*) of 5.0 × 10¹² Jones, the photocurrent dissymmetry factor (g_Iph) of 0.34, and external quantum efficiency (EQE) of 2.2 × 10³ (%) for a CPL of 450 nm.

This study presents a comprehensive investigation on the fabrication and characterization of piezoresistive elastomeric strain sensors using multiwalled carbon nanotubes (MWCNTs) incorporated into a silicone rubber matrix. Through meticulous experimentation and theoretical modeling, the study elucidates the intricate relationship between MWCNT concentration, mechanical properties, and electrical conductivity within the composite materials. The research reveals that composite formulations with MWCNT concentrations slightly above the percolation threshold exhibit superior strain-sensing properties. Specifically, composites containing 2 phr of MWCNTs demonstrate a remarkable gauge factor of 225, indicating enhanced sensitivity compared with higher MWCNT loadings. Mechanical testing using a tensile testing machine elucidates the complex interplay between MWCNT loading and tensile properties. However, subsequent enhancements in tensile properties with increasing MWCNT content suggest improved dispersion and reinforcing effects, highlighting the potential for tailored mechanical performance. The investigation of DC conductivity demonstrates a significant increase with rising MWCNT concentrations, indicative of the formation of conductive networks as MWCNTs reach the percolation threshold. Enhanced charge transport and constructive interface interactions facilitate efficient electron flow through the composite, which is crucial for applications requiring electrical conductivity. Moreover, the analysis of dielectric permittivity reveals its concentration-dependent increase, attributed to the large surface area of MWCNTs promoting stronger interactions with the matrix and enhanced polarization under electric fields. Drastic changes in AC conductivity at lower frequency levels within the percolation region suggest influences of dielectric relaxation, polarization effects, and formation of conductive paths. This study underscores the potential of MWCNTs-silicone rubber composites as versatile materials for advanced strain-sensing applications, offering tunable mechanical and electrical properties tailored to specific requirements.