Properties Of Devices Research Articles

Nanostructured Thin Films Enhancing the Performance of New Organic Electronic Devices: Does It Make Sense?

Electronics have evolved significantly with the development of semiconductor materials and devices, with emerging areas such as organic and flexible electronics showing great promise, particularly in applications such as wearable devices and environmental sensors. Since the discovery of conducting polymers in the late 1970s, organic electronics have paved the way for innovations such as organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs), and organic solar cells (OPVs). Recent advances have focused on nanostructuring techniques to enhance device properties, such as charge mobility and luminescence efficiency. The growing concern for sustainability has also led to the exploration of biodegradable organic electronics as a potential solution to electronic waste. This perspective briefly discusses the impact of nanostructuring on the performance of both conventional and biodegradable organic devices, exploring the challenges and opportunities associated with using alternative substrates like paper. This perspective emphasizes the importance of understanding molecular organization at the nanoscale to optimize device performance and ensure stability under practical conditions.

Impacts of material design on heat dissipation and power handling of acoustic-wave devices based on bonding wafers

Heat dissipation in surface acoustic wave (SAW) devices has never been researched in detail previously. With the arrival of the 5G era, more SAW devices with more complicated structures such as bonding wafers need to be integrated, easily leading to heat accumulation, so investigating heat dissipation in SAW devices is now necessary and urgent. Learning from the thermal-management researches in other fields and considering the mechanism and properties of SAW devices, this work believes that optimizing material design is efficient for heat dissipation enhancement. Therefore, this work for the first time systematically investigates the impacts of material design on heat dissipation and power handling which is significantly influenced by heat dissipation, building up a thermal-management theory for SAW devices based on bonding wafers. This work proposes a theoretical thermal calculation method for SAW devices, building a model and coding a calculation program. This work develops an experimental method by which the impacts of material design on heat dissipation can be deduced from those on power handling, designing and fabricating band-8 duplexers based on bonding wafers with different material designs. This work reveals that SiO2 and epoxy both weaken heat dissipation and impair power handling, while Si, sapphire, and SiC can all be chosen as heat-sink materials. Cost-efficient Si is quite proper for supporting substrates, and metal bumps are effective for thermal dissipation. This work gives guidance on enhancements of heat dissipation and power handling, helping researchers manage thermal properties in SAW devices and promoting the development of 5G communication.

Enhanced emission and surface modification in ZnO treated with Ar, H, and O plasmas

Plasma treatment is a crucial technique for manipulating the optoelectronic properties of ZnO devices by modifying surface defects. The choice of plasma gas in the treatment process significantly influences these defects, as evidenced by the luminescence characteristics. In this paper, significant differences have been observed in the photoluminescence spectra of ZnO films and single crystals before and after treatment with three kinds of plasma gas. After Ar and H plasma treatment, the UV emission is significantly enhanced up to 1000 times, while the visible emission is suppressed. Conversely, after O plasma treatment, the UV emission remains unchanged, but the deep level emission exhibits a subtle transformation. Since the influence depth of plasma treatment is confined to the surface, all these alterations of typical luminescence are strongly dependent on surface-related defects, thereby challenging the previous interpretation that they originate from bulk defects. The modification effects of various plasmas on surfaces are confirmed from multiple perspectives, and the mechanisms behind the enhancement or suppression of luminescence are systematically analyzed. A comprehensive understanding of plasma treatment, along with precise control of surface defects, is crucial for optimizing the performance of ZnO devices.

Modulating the Electrical Transport in Superconducting NbC Crystals by Fractal Morphology.

The self-similar fractal morphology mediated by nonequilibrium processes is widely observed in low-dimensional materials grown by various techniques. Understanding how these fractal geometries affect the physical and chemical properties of materials and devices is crucial for both fundamental studies and various applications. In particular, the interplay between superconducting phase fluctuations and disorder can give rise to intriguing phenomena depending on the dimensionality. However, current experimental studies on low-dimensional superconductors are limited to two- and one-dimensional systems, leaving fractional dimensional systems largely unexplored. Here, we use chemical vapor deposition to successfully synthesize ultrathin NbC crystals with a well-defined fractal geometry at the nanoscale. By performing electrical transport measurements, we find that both the superconducting and normal-state properties are strongly affected in the fractal samples, where the intrinsic and geometric disorder is induced. In contrast to the 2D crystal, the fractal NbC crystals show a significant low-temperature resistive upturn before the onset of superconducting transition, which can be attributed to the disorder-enhanced electron-electron interaction effect. From transport data analysis, we demonstrate that the superconducting transition in NbC is correlated to the strength of disorder and the fractional dimensions, revealing that nanoscale fractal structures can significantly modify the electronic properties of low-dimensional superconductors. Our work paves the way for the explorations of mesoscopic transport and intriguing superconducting phenomena in fractional dimensions.

Single-molecule Magnets (SMM) spin channels connecting FeMn antiferromagnet and NiFe ferromagnetic electrodes of a tunnel junction

The integration of single-molecule magnets (SMMs) into magnetic tunnel junctions (MTJs) offers significant potential for advancing molecular spintronics, particularly for next-generation memory devices, quantum computing, and energy storage technologies such as solar cells. In this study, we present the first demonstration of SMM-induced spin-dependent properties in an antiferromagnet-based MTJ molecular spintronic device (MTJMSD). We engineered cross-junction-shaped devices comprising FeMn/AlOx/NiFe MTJs. The AlOx barrier thickness where the exposed junction edges meet was comparable to the SMM length, facilitating the incorporation of SMM molecules as spin channels for spin-dependent transport. The SMM channels enabled long-range magnetic moment ordering around molecular junctions, which were precisely engineered via fabrication processes. The SMM, composed of a [Mn6(μ3-O)2(H2N-sao)6(6-atha)2(EtOH)6] (H2N-saoH = salicylamidoxime, 6-atha = 6-acetylthiohexanoate) complex, featured thioester groups at the ends that upon hydrolysis they form bonds with the magnetic electrodes. SMM-treated junctions demonstrated a significant current enhancement, reaching up to 7 μA at an input voltage of 60 mV. Furthermore, SMM-doped junctions exhibited current stabilization in the μA range at lower temperatures, whereas the bare electrodes showed current suppression to the picoampere range. Magnetization measurements conducted at 55 K and 300 K on pillar-shaped devices revealed a reduction in magnetic moment at low temperatures. Additionally, Kelvin probe atomic force microscopy (KPAFM) measurements confirmed that SMM integration transformed the electronic properties over long ranges.These findings are attributed to the spin channels formed between magnetic metal electrodes, which enhance spin polarization at each magnetic electrode. Our research highlights the potential of using antiferromagnetic materials, characterized by minimal stray fields and zero net magnetization, to transform MTJMSD devices.

Spin-torque nano-oscillators and their applications

Spin-torque nano-oscillators (STNOs) have emerged as an intriguing category of spintronic devices based on spin transfer torque to excite magnetic moment dynamics. The ultra-wide frequency tuning range, nanoscale size, and rich nonlinear dynamics have positioned STNOs at the forefront of advanced technologies, holding substantial promise in wireless communication, and neuromorphic computing. This review surveys recent advances in STNOs, including architectures, experimental methodologies, magnetodynamics, and device properties. Significantly, we focus on the exciting applications of STNOs, in fields ranging from signal processing to energy-efficient computing. Finally, we summarize the recent advancements and prospects for STNOs. This review aims to serve as a valuable resource for readers from diverse backgrounds, offering a concise yet comprehensive introduction to STNOs. It is designed to benefit newcomers seeking an entry point into the field and established members of the STNOs community, providing them with insightful perspectives on future developments.

Atomic structure of self-buffered BaZr(S, Se)3 epitaxial thin film interfaces

Understanding and controlling the growth of chalcogenide perovskite thin films through interface design is important for tailoring film properties. Here, the film and interface structure of BaZr(S,Se)3 thin films grown on LaAlO3 by molecular beam epitaxy and postgrowth anion exchange is resolved using aberration-corrected scanning transmission electron microscopy. Epitaxial films are achieved from self-assembly of an interface “buffer” layer, which accommodates the large film/substrate lattice mismatch of nearly 40% for the alloy film studied here. The self-assembled buffer layer, occurring for both the as-grown sulfide and post-selenization alloy films, is shown to have rock-salt-like atomic stacking akin to a Ruddlesden–Popper phase. These results provide insights into oxide-chalcogenide heteroepitaxial film growth, illustrating a process that yields relaxed, crystalline, epitaxial chalcogenide perovskite films that support ongoing studies of optoelectronic and device properties.

Compact Physical Implementation of Spiking Neural Network Using Ambipolar WSe2 n-Type/p-Type Ferroelectric Field-Effect Transistor.

Spiking neural networks (SNNs) are attracting increasing interests for their ability to emulate biological processes, offering energy-efficient computation and event-driven processing. Currently, no devices are known to combine both neuronal and synaptic functions. This study presents an experimental demonstration of an ambipolar WSe2 n-type/p-type ferroelectric field-effect transistor (n/p-FeFET) integrated with ferroelectric Hf0.5Zr0.5O2 (HZO) to achieve both volatile and nonvolatile properties in a single device. The nonvolatile n-FeFET, driven by the stable ferroelectric properties of HZO, exhibits highly linear synaptic behavior. In contrast, the volatile p-FeFET, influenced by electron self-compensation in the ambipolar WSe2, enables self-resetting leaky-integrate-and-fire neurons. Integrating neuronal and synaptic functions in the same device allows for compact neuromorphic computing applications. Additionally, simulations of SNNs using experimentally calibrated synaptic and neuronal models achieved a 93.8% accuracy in MNIST digit recognition. This innovative approach advances the development of SNNs with high biomimetic fidelity and reduced hardware costs.

Modulation of bandgap and transport properties by stacking symmetry in bilayer binary materials

The interlayer interactions in layered two-dimensional materials, which are formed by Van der Waals forces, significantly influence the control of electronic and transport properties. The manipulation of the stacking order can modulate these interlayer interactions by altering the atomic arrangement in different layers. In this study, we conducted a systematic examination of the bandgap modulation of bilayer two-dimensional binary materials at high symmetry stackings. A general trend of bandgap modulation has been proposed through a tight-binding model and corroborated by density functional calculations. The mechanisms of bandgap modulation can be leveraged to control the transport properties of devices built with bilayer two-dimensional binary materials. Our research findings offer valuable insights for the control of bandgap in layered two-dimensional materials and their application in transport devices.

Multifunctional Reconfigurable Operations in an Ultra-Scaled Ferroelectric Negative Transconductance Transistor.

The integration of functional materials into electronic devices has become a key approach to extending Moore's law by increasing the functional density of electronic circuits. Here, we present a device technology based on ultrascaled ferroelectric, antiambipolar transistors (ferro-AAT) with robust negative transconductance, enabling a wide range of reconfigurable functionalities with applications in both the digital and analog domains. The device relies on the integration of a hafnia-based ferroelectric gate stack on a vertical nanowire tunnel field-effect transistor. Through intentional gate/source overlap and tunnel-junction engineering, we demonstrate enhanced antiambipolarity with a high negative transconductance that is reconfigurable using the nonvolatile remanent polarization of the ferroelectric. Experimental validation highlights the versatility of this ferro-AAT in two implementation scenarios: content addressable memory (CAM) for high-density data search and reconfigurable signal processing in analog circuits. As a single-transistor cell for CAMs, the ferro-AAT shows subpicojoule operation for one search with a compact footprint of ∼0.01 μm2. For single-transistor-based signal modulation, multistate reconfigurations and high power conversion (>95%) are achieved in the ferro-AAT, resulting in a significant reduction in the complexity of analog circuit design. Our results reveal that the distinctive device properties allow ferro-AATs to operate beyond conventional transistors with multiple reconfigurable functionalities, ultrascaled footprint, and low power consumption.

Dielectric analysis of unpolymerized and photopolymerized NOA65 in a parallel-plate cell

The flourishing development of liquid crystal research in recent decades has highlighted the importance of polymer materials in enhancing liquid–crystal material and device properties, demonstrating tremendous potential in a wide range of industries. One of the polymer materials widely used in polymer-dispersed liquid crystal is Norland UV-curable optical adhesive (NOA65). This study focuses on the dielectric behavior of the optical adhesive in a parallel-plate cell. Given the broadness and asymmetry of the dielectric dispersion curve, the two-relaxation Havriliak–Negami model was employed to analyze the complex dielectric spectra of NOA65 before and after photocuring. Experimental results indicate that as temperature rises, the dielectric relaxation of NOA65 undergoes a blue shift, leading to an eventual overlap with pseudo-dielectric relaxation at a higher frequency. This brings about an increase in the obtained signal in the dielectric loss spectrum, implying that the observed feature of pseudo-dielectric relaxation is actually superposed or contributed by the intrinsic relaxation signal. Furthermore, as temperature continues to rise, the intrinsic dielectric loss signal of NOA65 becomes untraceable beyond the frequency span within which the pseudo-dielectric relaxation signal lies.

Doping-induced electronic transport properties in tetracene-based molecular device

Doping-induced electronic transport properties in tetracene-based molecular device

Manipulating Charge-to-Spin conversion via insertion layer control at the interface of topological insulator and ferromagnet

Strong spin–orbit coupling and highly spin-polarized surface states in topological insulators (TIs) are key parameters that explain their extremely high charge-to-spin conversion (CSC) efficiency at interfaces with ferromagnetic materials (FMs). This study focused on the influence of the insertion layer on the proximity effect occurring in a Co4Fe4B2/Bi2Se3 interface. Various insertion layers, including Au, MgO, and Se, were introduced to modulate the proximity effect from TI to FM and vice versa. X-ray photoelectron spectroscopy and transmission electron microscopy revealed that the Se insertion layer effectively suppresses the formation of an additional Bi layer, reducing intermixing against Co4Fe4B2. Electrical transport properties such as RXX and RXY under a vertical magnetic field show that the Se-inserted structure features the lowest anomalous Hall angle and exhibits a pristine topological surface state, indicating its potential for improving CSC efficiency. The Se-inserted structure exhibits the highest spin Hall angle among various heterostructures, according to results obtained from spin-torque ferromagnetic resonance. These findings highlight the importance of selecting an insertion layer and controlling the interface to optimize the spin-transport properties of TI-based spintronic devices and provide insights into the design of future spin devices.

Characterization and modeling of the mobility, threshold voltage, and subthreshold swing in p-GaN gate HEMTs at cryogenic temperatures

This study presents a comprehensive investigation of the electrical properties of p-GaN gate HEMT devices under cryogenic operations, spanning a temperature range from 300 K all the way down to 10 K. We report achievement of a low sub-60 mV/dec sub-threshold swing (SS) (33.2 mV/dec at 10 K), a high ION/IOFF ratio (∼3.5 × 1010 at 10 K), and a remarkable ID,max (∼358 mA/mm at 10 K) in p-GaN gate HEMTs operating under cryogenic conditions. Furthermore, the mobility, threshold voltage shifts, and SS characteristics at cryogenic temperatures are modeled in p-GaN HEMTs. In summary, p-GaN gate HEMTs are promising for cryogenic applications due to their low SS, high gm,max, impressive ION/IOFF ratio, and substantial ID,max. Furthermore, the modeling achieved in this work can pave the way for future characteristic prediction in p-GaN HEMTs at cryogenic temperatures.

Ab initio study of LiMn2O4 cathode: electrochemical and optical properties for li-ion batteries and optoelectronic devices

Ab initio study of LiMn2O4 cathode: electrochemical and optical properties for li-ion batteries and optoelectronic devices

Dielectric properties of low-temperature co-fired capacitor ceramics and MLCC devices with Ag inner electrodes

Low-temperature sintered 0.99((1−x)Bi0.5Na0.5TiO3-xNaNbO3)-0.01Sr0.8Na0.4Nb2O6 (100xNN, x = 0.25 and 0.30) ceramics and MLCC were successfully prepared, and the dielectric properties were systematically investigated. The dielectric permittivity at 25 °C (ε′25 °C) of 25NN ceramic is 1088, and the dielectric variation is small between −88 °C and 400 °C (|△ε′/ε′25 °C| ≤ 15%, △ε′=ε′-ε′25 °C). The dielectric loss tangent (tanδ) of 25NN ceramic is less than 0.02 between -65 °C and 358 °C. The MLCC with 25NN ceramic dielectrics and Ag inner electrode also has excellent dielectric stability, of which |△ε′/ε′25 °C| is less than 15 % between −100 °C and 400 °C, and the dielectric loss is less than 0.02 between −88 °C and 373 °C. All these results indicate that the low-temperature sintered MLCC with Ag inner electrodes is a promising capacitor in automobile engines and aerospace fields, where the usage temperature is often above 300 °C.

Taguchi Method Statistical Analysis on Characterization and Optimization of 18-nm Double Gate MOSFETs

A bi-layer graphene with a multigate structure was intensified and analysed on an 18-nm Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) device to obtain an optimal performance parameter. The device has a gate structure made of Titanium Dioxide (TiO2) that serves as a high-k material and a metal gate made of Tungsten Silicide (WSix). The Silvaco TCAD Software which are ATHENA and ATLAS modules were used to enhance the fabrication process of virtual devices and to verify the electrical properties of a specific device. According to the International Technology Roadmap Semiconductor (ITRS) specifications of 0.179 V ± 12.7% for threshold voltage (VTH) and 20 nA/m for leakage current (ILEAK), the Taguchi L9 orthogonal array strategy was used to improve the device process parameters for optimum VTH and ILEAK. For the NMOS device, the process parameter of VTH Adjust Implant Dose was used as the dominant factor while Source/Drain (S/D) Implant Energy was used as the adjustment factor whereby for PMOS device, S/D Implant Energy was the dominant factor while S/D Implant Tilt was the adjustment factor in order to achieve a robust design through the Taguchi method implementation. The percentage affecting the process parameter is then applied to the results of the signal to noise ratio (SNR) of Nominal-the-best (NTB) for VTH and Smaller-the-better (STB) for ILEAK.

Energy barriers govern catheter herniation during endovascular procedures: a 2.5D vascular flow model analysis.

Endovascular procedures rely on navigating guidewires, catheters and other devices through tortuous vasculature to treat disease. A critical challenge in these procedures is catheter herniation, in which the device deviates from its intended path, often irrecoverably. To elucidate the mechanics of herniation, we developed a physical flow model of the aortic arch that enables direct measurement of device curvature during experimentally simulated neuroendovascular procedures conducted from an upper arterial access. Combined with measurements of initial, unstressed device shapes and flexural rigidities, the method enables the experimental estimation of the device bending energies during these simulated procedures. Characteristic energy profiles revealed distinct stages in both herniation and successful navigation, governed by the interplay between device properties and vascular anatomy. A deterministic progression from successful navigation to herniation was identified, with catheter systems following paths determined by measurable energy barriers. Increasing guidewire stiffness or decreasing catheter stiffness reduced the energy barrier for successful navigation while increasing that for herniation. This framework enables the prediction of endovascular herniation risk and offers unique insight into improved device design and clinical decision-making.

Initial variations and optimization of electro-optic properties in CdSe/ZnS quantum-dot light-emitting diodes with ZnO nanoparticle electron transport layers

This study delves into the performance and stability of quantum-dot light-emitting diodes (QLEDs), with a specific focus on the initial variations in device properties and the effectiveness of various stabilization strategies. We assess the impact of initial bias conditions, reverse bias treatment, thermal annealing of the zinc oxide electron transport layer (ZnO electron transporting layer), and the effects of shelf storage on device reliability and efficiency. Our findings reveal that QLEDs are highly sensitive to initial bias conditions, yet this sensitivity can be significantly reduced through strategic interventions such as thermal annealing and reverse bias applications. These treatments are shown to markedly enhance the operational reliability of the devices. By providing deep insights into the mechanisms behind the initial variations in QLED properties, our research outlines practical measures for improving their performance and reliability, with profound implications for the advancement of high-performance display technologies.

Enhanced SWIR Absorption in PMMA‐Coated TiN‐Based Metamaterial

AbstractAchieving highly efficient absorption in the short wavelength infrared (SWIR) spectral region is crucial for advancing numerous technologies. SWIR absorption enhances energy harvesting in solar cells, improves the sensitivity of infrared sensors, and enables precise control of thermal radiative properties in thermal emission devices. These advancements are essential for applications such as thermal imaging, night vision, and thermophotovoltaic systems. The study presents a simple, cost‐effective design of a polymer‐coated multilayer perfect absorber (MPA) metamaterial optimized for the SWIR spectral region. The proposed MPA structure is composed of four distinct layers: a top layer made of polymethyl methacrylate (PMMA) polymer, a second layer featuring arrays of circular titanium nitride (TiN) disks, a dielectric middle layer consisting of a pure zinc oxide (ZnO) film, and a bottom metallic layer formed by a thin film of TiN. The results demonstrate that the MPA achieves near‐perfect absorption, with a remarkable 99% efficiency centered at a wavelength of 1.3 µm. The absorption properties are further investigated with respect to various structural parameters to ensure better performance of the absorber. These absorbers hold great promise for applications in energy absorption, infrared sensing, thermal emission, and related fields.