Future Electronics Research Articles

Intrinsically flexible CNT-TiO2-Interlaced film for NO sensing at room temperature

Carbon nanotubes (CNTs) are potential candidates for wearable gas monitoring devices based on their large surface area, room temperature response and flexibility. Considering the demand on sensitivity and flexibility, innovated structural design is essential for realizing those applications. Here, we present a carbon nanotubes-anatase titanium dioxide (CNT/a-TiO2) film-based sensor by in situ hydrolysis and calcination. The CNT/a-TiO2 sensor exhibits good sensitivity (41% resistance change in response to 50 ppm NO), fast and reversible response at room temperature, and high selectivity toward NO among several toxic gases including NH3, NO2, CH4 and H2S. Furthermore, the continuous CNT/a-TiO2 network, consisting of numerous flexible micro-areas of CNT segments interlaced with rigid CNT/a-TiO2 active segments, can endure complex deformations while maintaining their superior sensing properties. These lightweight CNT/a-TiO2 films with high performance and intrinsic flexibility films have application potential in future wearable electronics and gas monitoring devices.

Electricity Generation and Self-Powered Sensing Enabled by Dynamic Electric Double Layer at Hydrogel–Dielectric Elastomer Interfaces

The electric double layer (EDL) at liquid-solid interfaces is fundamental to many research areas ranging from electrochemistry and microfluidics to colloidal chemistry. Here, we demonstrate the electricity generation by mechanically modulating the EDL at the hydrogel-dielectric polymer interfaces. It is found that contact electrification between the hydrogel and the dielectric polymer could charge the dielectric polymer surface at first; the mechanical deformation of the pyramid-shaped hydrogel results in the periodic variation of the EDL area and capacitance, which then induces an alternative current in the external circuits. This mechano-to-electrical energy conversion mechanism is then utilized to construct soft stretchable self-powered pressure sensors by designing dynamic EDL at hydrogel-dielectric elastomer interfaces. The sensitivity is optimized to 1.40 kPa-1 in the low-pressure range of 31-300 Pa by increasing the elastomer roughness. Its antifreeze performance is also improved by adding ethylene glycol into the hydrogel. The capability in detecting subtle human activities is further demonstrated. This mechano-electrical energy conversion and the corresponding self-powered sensor can be widely applied in future soft electronics.

Higgs production in association with a dark-Z at future electron positron colliders

In recent years there have been many proposals for new electron–positron colliders, such as the circular electron–positron collider, the international linear collider, and the future circular collider in electron–positron mode. Much of the motivation for these colliders is precision measurements of the Higgs boson and searches for new electroweak states. Hence, many of these studies are focused on energies above the hZ threshold. However, there are proposals to run these colliders at the lower W W threshold and Z-pole energies. In this paper, we study a new search for Higgs physics accessible at lower energies: e + e − → hZ d, where Z d is a new light gauge boson such as a dark photon or dark-Z. Such searches can be conducted at the W W threshold, i.e. energies below the hZ threshold where exotic Higgs decays can be searched for in earnest. Additionally, due to very good angular and energy resolution at future electron–positron colliders, these searches will be sensitive to Z d masses below 1 GeV, which is lower than the current direct LHC searches. We will show that at GeV with 10 ab−1, a search for e + e − → hZ d is sensitive to h − Z − Z d couplings of δ ∼ 9 × 10−3 and cross sections of ab for Z d masses below 1 GeV. The results are similar at GeV with 5 ab−1. These limits are better than those expected from limits on the HL-LHC limits on Higgs branching ratio into generic non-standard model final states and comparable to meson decay limits.

Photoinjector generation of high-charge magnetized beams for electron-cooling applications

Electron cooling offers a relatively simple scheme to enable high-luminosity collisions in future electron–ion and hadron colliders. Contemplated TeV-energy hadron colliders require relativistic (sub 100 MeV) high-charge [O(nC)] electron beams with a specific transverse eigenemittance partition. This paper discusses the generation of high-charge (Q≤3.2 nC) 40 MeV electron bunches with eigenemittance partition consistent with requirements associated with electron-cooling option for future electron–ion colliders. The supporting experiment was performed at the FAST facility at Fermilab. The data are compared with numerical simulations and the results discussed in the context of beam requirement for future electron–ion colliders.

Regio- and Steric Effects on Single Molecule Conductance of Phenanthrenes

Here, six phenanthrene (the smallest arm-chair graphene nanoribbon) derivatives with dithiomethyl substitutions at different positions as the anchoring groups were synthesized. Scanning tunneling microscopy break junction technique was used to measure their single molecule conductances between gold electrodes, which showed a difference as much as 20-fold in the range of ∼10-2.82 G0 to ∼10-4.09 G0 following the trend of G2,7 > G3,6 > G2,6 > G1,7 > G1,6 > G1,8. DFT calculations agree well with this measured trend and indicate that the single molecule conductances are a combination of energy alignment, electronic coupling, and quantum effects. This significant regio- and steric effect on the single molecule conductance of phenanthrene model molecules shows the complexity in the practice of graphene nanoribbons as building blocks for future carbon-based electronics in one hand but also provides good conductance tunability on the other hand.

Green Flexible Graphene–Inorganic‐Hybrid Micro‐Supercapacitors Made of Fallen Leaves Enabled by Ultrafast Laser Pulses

AbstractThe development of green flexible micro‐supercapacitors (MSCs) is one of the biggest challenges in future wearable electronics. Flexible MSCs are mainly produced from non‐biodegradable synthetic polymers, resulting in massive electronic waste. Moreover, complex multi‐step fabrication increases their production cost. Here, the direct fabrication of highly conductive, intrinsically flexible, and green microelectrodes from naturally fallen leaves in ambient air using femtosecond laser pulses without any additional materials is reported. Hierarchically porous graphene is patterned on different types of leaves via a facile, mask‐less, scalable, and one‐step laser writing. Leaves consist of biominerals, which decompose into inorganic crystals that serve as nucleation sites for the growth of 3D mesoporous few‐layer graphene. The femtosecond laser‐induced graphene (FsLIG) microelectrodes formed on leaves have lower sheet resistance (23.3 Ω sq−1) than their synthetic polymer counterparts and exhibit an outstanding areal capacitance (34.68 mF cm−2 at 5 mV s−1) and capacitance retention (≈99% after 50 000 charge/discharge cycles). The FsLIG MSCs on a single leaf could easily power a light‐emitting diode or a table clock and could be applied in wearable electronics, smart houses, and Internet of Things.

Solution-processed metal oxide dielectric films: Progress and outlook

There has been growing interest in the use of the sol-gel approach to form high-quality dielectric materials. Their tailored properties allow for developing functional electronic devices in a scalable and rapid manner. According to physicochemical principles, the displacement and response behavior of charges under an applied external field can manifest in unique dielectric properties, providing useful information to improve the process, design, and quality of electronic devices. Therefore, a systematic and in-depth investigation of the fundamentals of sol-gel dielectrics is necessary. In this Research Update, we present recent advances in various sol-gel-processed dielectric materials and their applications to functional electronic devices. A brief introduction to sol-gel chemistry to form oxide dielectric films and the basis of physical mechanisms under electrical fields are discussed. Along with the dielectric properties, recent achievements of proof-of-concept experiments and their various applications to functional electronic devices are introduced. It is expected that further innovations in solution-processed metal oxide dielectrics will achieve cost-effective high-performance functional electronics in the near future.

Highly Responsive Asymmetric Pressure Sensor Based on MXene/Reduced Graphene Oxide Nanocomposite Fabricated by Laser Scribing Technique

Flexible pressure sensors play a vital role in wearable devices, human physiological activity monitoring, smart robots and other fields. However, current flexible piezoresistive sensors typically have the disadvantages of complex preparation processes, inability to take into account sensitivity and pressure response range, and poor cycle stability. Herein, a novel flexible asymmetric pressure sensor has been proposed by adjusting sensing material and optimizing the structure of electrode. As a crucial piezoresistive material, MXene/reduced graphene oxide (MXene/rGO) nanocomposite with a layer by layer stacked structure is developed by an efficient and precise one-step laser scribing technology. Benefit from this designed layer by layer crosslinked structure, the proposed flexible MXene/rGO asymmetric pressure sensor exhibits excellent pressure-sensing performances, such as high sensitivity of 2.25 kPa^&#x2212;1 (0 &#x2013; 200 Pa), low detection limit of about 2.5 Pa, fast responsive recovery, and long cycle durability. So that our flexible MXene/rGO asymmetric pressure sensor can detect subtle body physiological motions in real time, such as wrist pulse, vocal vibration, finger movement, and breath. Additionally, the as-prepared sensor array integrated by <inline-formula> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> identical MXene/rGO asymmetric pressure sensors exhibits good multi-touch function. Therefore, such conspicuous sensing performances endow our MXene/rGO asymmetric pressure sensor for widespread practical applications in future flexible wearable electronics.

A Flexible and Transparent Zinc-Nanofiber Network Electrode for Wearable Electrochromic, Rechargeable Zn-Ion Battery.

The flexible electrochromic Zn-ion battery (FE-ZiB), a newly born energy-storage technology having both electrochromic characteristics and energy-storage capability in a single device, will be a promising technology for the future transparent wearable electronics. However, the current technology limits the fabrication of FE-ZIB because the zinc (Zn) anode material is opaque and rigid. The development of a flexible and transparent Zn anode is the key factor to overcoming the current limitation. Here, for the first time, a flexible, transparent zinc-nanofiber network anode electrode (Zn@Ni@AgNFs) is reported for an FE-ZiB device that yields a remarkable electrochemical performance of a high areal capacity of 174.82mA h m2 at 0.013mA cm-2 applied current density, high optical contrast (50%), and excellent mechanical flexibility. The fabricated FE-ZiB device also exhibits a high volumetric energy density of 378.8 W h m-3 at a power density of 562.7 W m-3 . Besides, the FE-ZiB demonstrates excellent electrochromic capability with a reversible color transition from a transparent in a discharged state (0.3V) to a dark bluish-violet in a charged state (1.6V). These results highlight a new pathway for the development of transparent batteries for smart wearable electronic devices.

Switching characteristic of fabricated nonvolatile bipolar resistive switching memory (ReRAM) using PEDOT: PSS/GO

In this study, a bipolar resistive switching random access memory cell (ReRAM) by blending PEDOT: PSS into Graphene Oxide (GO) with 1:1 wt% is reported. To compare the switching mechanism, the memory devices based on GO and PEDOT: PSS are distinctly fabricated and characterized too. The spin coated active layers are sandwiched between ITO and Al as the bottom and top electrodes, respectively. The resistive switching mechanism in PEDOT: PSS/GO memory is based on filamentary type. The SET and RESET operation of the PEDOT: PSS/GO memory is relatively symmetric but GO and PEDOT: PSS samples have a significant asymmetric hysteresis curve. The carrier transport mechanism of the bistable behaviour for the fabricated non-volatile ReRAM is described based on space charge limited current (SCLC). In our experiments, the structure ITO/PEDOT:PSS-GO/Al demonstrated good switching behaviour with approximately 100 on/off current ratio, 3.5 V set/reset voltage and, a high retention time of 6000 s. In addition, the crystallinity and surface topography of the deposited thin film was characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The simple structure and low-cost fabrication offer embedding in data storage and computing application as future electronics and printed electronics.

Computing and comparative analysis of topological invariants of Y‐junction carbon nanotubes

AbstractRecent findings of diverse forms of carbon nanostructures have encouraged research on their applications in several areas. They are used as a structural material in electronic and optical devices, involving transistors, photodetectors, plastic, biological sensors, pharmaceutical and medicine, and drug delivery systems. Since the discovery of Y‐shaped carbon nanotubes (CNTs) junctions, they have drawn interest for future electron devices, for example, three‐terminal transistors, amplifiers, and switches. A topological index is a number that is used to study the physicochemical properties of chemical structures. In this paper, we are providing topological properties of CNT Y‐junctions. The results obtained for different types of Y‐junction graphs appeared with comparisons. According to the best of our knowledge and literature, this is the first report about topological indices on this class of CNT junctions.

Flexible transparent conducting strontium vanadate/mica heteroepitaxial membranes with mechanically tunable transport behaviors

Strongly correlated metal strontium vanadate (SrVO3) was recently proposed to be used as a promising transparent conductor. Control of the optical and electrical properties of SrVO3 thin films using external stimuli is highly desired for most practical applications. Herein, flexible heteroepitaxial SrVO3 films on mica substrates were synthesized in a simple process using a pulsed laser deposition (PLD) method, showing high optical transparency and excellent electrical conductivity. The experiments demonstrate that the resistivity of flexible SrVO3 films depends strongly on the applied mechanical strain whereas the optical transmittance is retained during the bending tests. It is shown that two distinctly different resistivity values are switched back and forth repeatedly upon applying or removing a mechanical bending strain. The measured resistivity increases with increasing mechanical strain, which is attributed to the enhanced residual resistivity present in flexible SrVO3/mica membranes upon the application of a mechanical strain. We demonstrate that mechanical strain allows effective tuning of electrical conductivity in epitaxial SrVO3/mica membranes. The transparent conducting oxide SrVO3/mica membranes with highly tunable electrical conductivity show great potential for future flexible electronics and photovoltaics.

Interfacial synthesis of crystalline quasi-two-dimensional polyaniline thin films for high-performance flexible on-chip micro-supercapacitors

Quasi-two-dimensional (q2D) conducting polymer thin film synergizes the advantageous features of long-range molecular ordering and high intrinsic conductivity, which are promising for flexible thin film-based micro-supercapacitors (MSCs). Herein, we present the high-performance flexible MSCs based on highly ordered quasi-two-dimensional polyaniline (q2D-PANI) thin film using surfactant monolayer assisted interfacial synthesis (SMAIS). Owing to high electrical conductivity, rich redox chemistry, and thin-film morphology, the q2D-PANI MSCs show high volumetric specific capacitance (ca. 360 F/cm3) and energy density (17.9 mWh/cm3), which outperform the state-of-art PANI thin-film based MSCs and promise for future flexible electronics.

Van der Waals Heterostructure of Hexagonal Boron Nitride with an AlGaN/GaN Epitaxial Wafer for High-Performance Radio Frequency Applications.

While two-dimensional (2D) hexagonal boron nitride (h-BN) is emerging as an atomically thin and dangling bond-free insulating layer for next-generation electronics and optoelectronics, its practical implementation into miniaturized integrated circuits has been significantly limited due to difficulties in large-scale growth directly on epitaxial semiconductor wafers. Herein, the realization of a wafer-scale h-BN van der Waals heterostructure with a 2 in. AlGaN/GaN high-electron mobility transistor (HEMT) wafer using metal-organic chemical vapor deposition is presented. The combination of state-of-the-art microscopic and spectroscopic analyses and theoretical calculations reveals that the heterointerface between ∼2.5 nm-thick h-BN and AlGaN layers is atomically sharp and exhibits a very weak van der Waals interaction without formation of a ternary or quaternary alloy that can induce undesired degradation of device performance. The fabricated AlGaN/GaN HEMT with h-BN shows very promising performance including a cutoff frequency (fT) and maximum oscillation frequency (fMAX) as high as 28 and 88 GHz, respectively, enabled by an effective passivation of surface defects on the HEMT wafer to deliver accurate information with minimized power loss. These findings pave the way for practical implementation of 2D materials integrated with conventional microelectronic devices and the realization of future all-2D electronics.

Proton Radiation Hardness of Perovskite Solar Cells Utilizing a Mesoporous Carbon Electrode

When designing spacefaring vehicles and orbital instrumentation, the onboard systems such as microelectronics and solar cells require shielding to protect them from degradation brought on by collisions with high‐energy particles. Perovskite solar cells (PSCs) have been shown to be much more radiation stable than Si and GaAs devices, while also providing the ability to be fabricated on flexible substrates. However, even PSCs have their limits, with higher fluences being a cause of degradation. Herein, a novel solution utilizing a screen‐printed, mesoporous carbon electrode to act bi‐functionally as an encapsulate and the electrode is presented. It is demonstrated that the carbon electrode PSCs can withstand proton irradiation up to 1 × 1015 protons cm−2 at 150 KeV with negligible losses (&lt;0.07%) in power conversion efficiency. The 12 μm thick electrode acts as efficient shielding for the perovskite embedded in the mesoporous TiO2. Through Raman and photoluminescence spectroscopy, results suggest that the structural properties of the perovskite and carbon remain intact. Simulations of the device structure show that superior radiation protection comes in conjunction with good device performance. This work highlights the potential of using a carbon electrode for future space electronics which is not limited to only solar cells.

Gate induced quantum wires in GaAs/AlGaAs heterostructures by cleaved edge deposition

Electric conductors with dimensions reduced to the nanometer scale are the prerequisite of the quantum devices upon which the future advanced electronics is expected to be based. In the past, the fabrication of one-dimensional (1D) wires has been a particular challenge because they have to be defect-free over their whole length, which can be several tens µm. Excellent 1D wires have been produced by cleaving semiconductors (GaAs, AlGaAs) in ultra high vacuum and overgrowing the pristine edge surface by molecular beam epitaxy (MBE)1,2. Unfortunately, this cleaved edge overgrowth (CEO) technique did not find wide-spread use because it requires a series of elaborate steps that are difficult to accomplish. In this Letter, we present a greatly simplified variation of this technique where the cleaving takes place in ambient air and the MBE overgrowth is replaced by a standard deposition process. Wires produced by this cleaved edge deposition (CED) technique have properties that are as least as good as the traditional CEO ones. Due to its simplicity, the CED technique offers a generally accessible way to produce 1D devices.

Organic Semiconductor/Insulator Blends for Elastic Field‐Effect Transistors and Sensors

AbstractOrganic semiconductors encounter limitations in their practical applicability in future electronics due to their low environmental stability and poor charge carrier mobilities. Blending with isolation of thermoplastic polymers and elastomers circumvents these restrictions and even induces new material properties, opening the door to novel flexible and stretchable electronics that hold great potential for improving people's life. This review discusses next generation applications of solution processable organic semiconductor/insulator blends in organic field‐effect transistors (OFETs). The fundamental basis is a comprehensive understanding of the phase separation mechanism that determines the morphology formation and electronic properties of the thin blend film. Continuous charge carrier pathways in blend OFETs are established by controlled phase separation through the chemical structure of components and the processing conditions. Recent advances in organic semiconductor/insulator blends with enhanced device properties including charge carrier mobility, life‐time, sensing ability, and especially mechanical behavior are reviewed with emphasis on implication in flexible and stretchable electronics. The concept of tuning existing properties and creating new ones of electronically active materials by blending with well‐selected insulators has great potential also for other types of electronic devices and classes of semiconductors.

Spin asymmetries in electron-jet production at the future electron ion collider

We study all the possible spin asymmetries that can arise in back-to-back electron-jet production, ep → e + jet + X, as well as the associated jet fragmentation process, ep → e+jet(h)+X, in electron-proton collisions. We derive the factorization formalism for these spin asymmetries and perform the corresponding phenomenology for the kinematics relevant to the future electron ion collider. In the case of unpolarized electron-proton scattering, we also give predictions for azimuthal asymmetries for the HERA experiment. This demonstrates that electron-jet production is an outstanding process for probing unpolarized and polarized transverse momentum dependent parton distribution functions and fragmentation functions.

Experimental proof test of CW mode RF modulated grid-controlled thermionic electron gun

A CW mode RF modulated grid-controlled thermionic electron gun was proposed by Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS) for some high average current electron accelerators requirements. The RF modulated grid-controlled thermionic electron gun was selected for these purposes due to its simplicity and cost savings. The experimental proof test of this type electron gun was conducted. The RF power supply at 107.5 MHz for the grid modulation can be adjusted from 10 W to 70 W. The RF power is coupled into the gun of grid-cathode through a RF&DC modulator. The electromagnetic field and RF simulation of the modulator is presented here. The gun structure and the beam dynamics design are also shown in the paper. The cathode assembly and the electron guns are tested on a 10 kV test bench for beam characterization. The CW mode 107.5 MHz electron beam obtained from the proof test, which is important for future high average current electron injectors development.

An Artificial Nerve Capable of UV-Perception, NIR-Vis Switchable Plasticity Modulation, and Motion State Monitoring.

The first flexible organic‐heterojunction neuromorphic transistor (OHNT) that senses broadband light, including near‐ultraviolet (NUV), visible (vis), and near‐infrared (NIR), and processes multiplexed‐neurotransmission signals is demonstrated. For UV perception, electrical energy consumption down to 536 aJ per synaptic event is demonstrated, at least one order of magnitude lower than current UV‐sensitive synaptic devices. For NIR‐ and vis‐perception, switchable plasticity by alternating light sources is yielded for recognition and memory. The device emulates multiplexed neurochemical transition of different neurotransmitters such as dopamine and noradrenaline to form short‐term and long‐term responses. These facilitate the first realization of human‐integrated motion state monitoring and processing using a synaptic hardware, which is then used for real‐time heart monitoring of human movement. Motion state analysis with the 96% accuracy is then achieved by artificial neural network. This work provides important support to future biomedical electronics and neural prostheses.