Applications In Electronic Devices Research Articles

Low defect density in MoS2 monolayers grown on Au(111) by metal-organic chemical vapor deposition

Monolayers of transition metal dichalcogenides (TMDs) possess high potential for applications in novel electronic and optoelectronic devices and therefore the development of methods for their scalable growth is of high importance. Among different suggested approaches, metal-organic chemical vapor deposition (MOCVD) is the most promising one for technological applications because of its lower growth temperature compared to the most other methods, e.g., conventional chemical vapor or atomic layer deposition (CVD, ALD). Here we demonstrate for the first time the epitaxial growth of MoS2 monolayers on Au(111) by MOCVD at 450 °C. We confirm the high quality of the grown TMD monolayers down to the atomic scale using several complementary methods. These include Raman spectroscopy, non-contact atomic force microscopy (nc-AFM), X-ray photoelectron spectroscopy and scanning tunneling microscopy (STM). The topographic corrugation of the MoS2 monolayer on Au(111), revealed in a moiré structure, was measured as ≈20 pm by nc-AFM. The estimated defect density calculated from STM images of the as-grown MoS2 monolayers is in the order of 1012 vacancies/cm2. The defects are mainly caused by single sulfur vacancies. Our approach is a step forward towards the technologically relevant growth of high-quality, large-area TMD monolayers.

Nacre-like Anisotropic Multifunctional Aramid Nanofiber Composites for Electromagnetic Interference Shielding, Thermal Management, and Strain Sensing.

Developing multifunctional flexible composites with high-performance electromagnetic interference (EMI) shielding, thermal management, and sensing capacity is urgently required but challenging for next-generation smart electronic devices. Herein, novel nacre-like aramid nanofibers (ANFs)-based composite films with an anisotropic layered microstructure were prepared via vacuum-assisted filtration and hot-pressing. The formed 3D conductive skeleton enabled fast electron and phonon transport pathways in the composite films. As a result, the composite films showed a high electrical conductivity of 71.53 S/cm and an outstanding thermal conductivity of 6.4 W/m·K when the mass ratio of ANFs to MXene/AgNWs was 10:8. The excellent electrical properties and multi-layered structure endowed the composite films with superior EMI shielding performance and remarkable Joule heating performance, with a surface temperature of 78.3 °C at a voltage of 2.5 V. Additionally, it was found that the composite films also exhibited excellent mechanical properties and outstanding flame resistance. Moreover, the composite films could be further designed as strain sensors, which show great promise in monitoring real-time signals for human motion. These satisfactory results may open up a new opportunity for EMI shielding, thermal management, and sensing applications in wearable electronic devices.

Advances in Charge Carrier Mobility of Diketopyrrolopyrrole-Based Organic Semiconductors

In recent years, the charge carrier mobility study of organic semiconductors has seen significant progress and surpassed that of amorphous silicon thanks to the development of various molecular engineering, solution processing, and external alignment methods. These advances have allowed the implementation of organic semiconductors for fabricating high-performance organic electronic devices. In particular, diketopyrrolopyrrole-based small-molecular and polymeric organic semiconductors have garnered considerable research interest due to their ambipolar charge-carrier properties. In this article, we focus on conducting a comprehensive review of previous studies that are dedicated to the external alignment, thermal annealing, and molecular engineering of diketopyrrolopyrrole molecular structures and side-chain structures in order to achieve oriented crystal orientation, optimized thin-film morphology, and enhanced charge carrier transport. By discussing these benchmark studies, this work aims to provide general insights into optimizing other high-mobility, solution-processed organic semiconductors and sheds lights on realizing the acceleration of organic electronic device applications.

High-strength conductive hydrogels based on the Hofmeister effect for friction nanogenerators

Hydrogels have received much attention in the field of flexible electronics as materials with flexibility and multifunctionality. The mechanical strength of conventional hydrogels is usually difficult to meet the requirements of practical applications in electronic devices. How to fabricate a high-strength hydrogel should remain a challenge. Here, a strategy to enhance the mechanical properties of conductive hydrogels based on the Hofmeister effect is reported. The mechanical properties of hydrogels were enhanced by increasing the polymer chain density, enhancing the hydrophobicity and increasing the crystallinity, the high-strength and high-toughness polyvinyl alcohol/carbon nanotubes/polyethyleneimine (PVA/MWCNTs/PEI) conductive hydrogel was successfully produced. The ultimate stress of the hydrogel was as high as 3.5–6.3 MPa, the elongation at break was between 500 and 1200 %, and the toughness was up to 23.62 MJ/m3. The conductivity of high-strength, high-toughness hydrogel is 0.05–0.45 S/m. Hydrogel was manufactured into a single-electrode friction nanogenerator (TENG), and it can easily light up to 100 LEDs. Therefore, this high-strength and high-toughness conductive hydrogel has great potential for TENG applications, offering the possibility of extending the working life of TENG in harsh environments.

Research Progress of Graphene Thin Films for Heat Dissipation Applications in Electronic Devices

Research Progress of Graphene Thin Films for Heat Dissipation Applications in Electronic Devices

Electrical Control of the Valley-Layer Hall Effect in Ferromagnetic Bilayer Lattices.

The layertronics based on the layer degree of freedom are of essential significance for the construction and application of new-generation electronic devices. Although the Hall layer effect has been realized theoretically and experimentally, it is mainly based on topological and antiferromagnetic lattices. On the basis of the low-energy effective k·p model, the mechanism of the controllable valley-layer Hall effect (V-LHE) in a bilayer ferromagnetic lattice through interlayer sliding has been proposed. Due to the broken time-reversal and inversion symmetries, the V-LHE based on the valley, layer degree of freedom, ferromagnetism, and ferroelectricity can be predicted. In addition, valley and layer indexes can be controlled by magnetization orientation and slipping, respectively. The mechanism can be demonstrated in the real bilayer CrSI lattice through first-principles calculations. Moreover, V-LHE can be effectively tuned by the perpendicular external electric field in configurations without out-of-plane polarization. These findings provide a new platform for the research of valleytronics and layertronics.

Remote vapor-phase dual alkali halide salts assisted quasi-van der Waals epitaxy of m-phase ZrO2 thin films with high dielectric constant and stable flexible properties

High-κ dielectric constant and wideband gap of ZrO2 material render it as an excellent candidate for transistor gate dielectric layers. However, current reported synthesis techniques suffer the problems of high precursor volatilization rate, ultrasmall grains with low dielectric constant, and high leakage current, which largely impede its application in electronic devices. Here, the quasi-van der Waals epitaxy growth of compact m-phase ZrO2 thin films has been developed, in which the stable supply of Zr source is realized by the tuned sublimation of ZrC powder with remote vapor-phase dual halide salts assistant. The formation of m-phase ZrO2 is due to the lower Gibbs free energy, in which the crystal nucleates at the etched hole edges of mica substrate, thus forming hexagonal shape polycrystal grains and merging as the continuous thin films. The microstructures and Raman spectrum characterization reveal the two dominated growth orientations and good crystal qualities, which indicate the uniform dielectric constant. The excellent growth reproducibility could be easily adapted to thin metal substrates, such as tungsten, molybdenum, and stainless steel, where the adhesion strength is strong because of the higher density of interfacial chemical bonding. Meanwhile, the metal–insulator–metal flexible capacitors show the high dielectric constant of 23–26 and low leakage current density of 10−4 A/cm2 at large voltage and only exhibit the decreased capacitance density of 7% after several hundred bending cycles. Our work paves a way to achieve the high-quality dielectric thin films on various substrates by the unique chemical vapor deposition design strategy.

Advancing cryogenic electronic cooling: A case study on embedded manifold microchannels in micromachined Joule-Thomson coolers

Thermal management plays a crucial role in the performance of electronic devices. For devices operating at room temperatures, manifold microchannels (MMCs) are essential for heat dissipation in heat sinks due to their low thermal resistance and pressure drop. However, their application in cryogenic electronic devices to enhance thermal performance has been largely unexplored. Herein, we integrated manifold microchannels into the evaporator of a micromachined Joule-Thomson (MJT) cooler to improve its cooling performance. The results show a notable reduction in the minimum cooling temperature from 105.0 K to 95.3 K, accompanied by an approximate 20 % increase in maximum cooling power. Furthermore, the coefficient of performance (COP) exhibits a rise of over 20 %. These findings underscore the feasibility and effectiveness of using MMCs in cryogenic electronic devices.

Preparation, optical properties, room temperature ferromagnetism, and mechanism of ordered nanotube-like tantalum oxide films

Physical property changes caused by defects have recently attracted significant attention due to their potential applications in sensors, spintronic devices, and multifunctional memory. Due to their numerous surface defects, this study fabricated ordered Ta2O5 nanotube (NT) thin films on Ta foil through an anodization technique. Then, the oxygen bubble model was applied to explain the formation of NTs from the perspective of lattice orientation. Furthermore, this study investigated influence of anodization duration and annealing treatment on the crystal structure, optical properties, and magnetic behavior. Notably, room-temperature ferromagnetism was observed in the as-prepared Ta2O5 NTs for the first time. After annealing in an argon atmosphere, the band gap of the sample decreased, accompanied by an increase in ferromagnetism. The underlying mechanism for this phenomenon was elucidated using a hydrogen-like impurity model. Consequently, this study on the magnetism of Ta2O5 NTs holds excellent potential for expanding their application in spin electronic devices.

Green and solid state reduction of GO monolayers sandwiched between Arachidic acid LB layers

A novel, single step and environment friendly solid state approach for reduction of graphene oxide (GO) monolayers has been demonstrated, in which, arachidic acid/GO/arachidic acid (AA/GO/AA) sandwich structure obtained by Langmuir-Blodgett (LB) technique was heat treated at moderate temperatures to obtain RGO sheets. Heat treatment of AA/GO/AA sandwich structure at 200 °C results in substantial reduction of GO, with concurrent removal of AA molecules. Such developed RGO sheets possess sp2-C content of ∼69 %, O/C ratio of ∼0.17 and significantly reduced I(D)/I(G) ratio of ∼1.1. Ultraviolet photoelectron spectroscopy (UPS) studies on RGO sheets evidenced significant increase in density of states in immediate vicinity of Fermi level and decrease in work function after reduction. Bottom gated field effect transistors fabricated with isolated RGO sheets displayed charge neutrality point at a positive gate voltage, indicating p-type nature, consistent with UPS and electrostatic force microscopy (EFM) measurement results. The RGO sheets obtained by heat treatment of AA/GO/AA sandwich structure exhibited conductivity in the range of 2–7 S/cm and field effect mobility of 0.03–2 cm2/Vs, which are comparable with values reported for RGO sheets obtained by various chemical/thermal reduction procedures. The extent of GO reduction is determined primarily by proximity of AA molecules and found to be unaltered with either escalation of heat treatment temperature or increase of AA content in sandwich structure. The single-step GO reduction approach demonstrated in this work is an effective way for development of RGO monolayers with high structural quality towards graphene-based electronic device applications.

Controllable synthesis of TiO2/graphene composites for human voice recognition in strain sensor.

Low-dimensional materials have demonstrated strong potential for use in diverse flexible strain sensors for wearable electronic device applications. However, the limited contact area in the sensing layer, caused by the low specific surface area of typical nanomaterials, hinders the pursuit of high-performance strain-sensor applications. Herein, we report an efficient method for synthesizing TiO2-based nanocomposite materials by directly using industrial raw materials with ultrahigh specific surface areas that can be used for strain sensors. A kinetic study of the self-seeded thermal hydrolysis sulfate process was conducted for the controllable synthesis of pure TiO2 and related TiO2/graphene composites. The hydrolysis readily modified the crystal form and morphology of the prepared TiO2 nanoparticles, and the prepared composite samples possessed a uniform nanoporous structure. Experiments demonstrated that the TiO2/graphene composite can be used in strain sensors with a maximum Gauge factor of 252. In addition, the TiO2/graphene composite-based strain sensor showed high stability by continuously operating over 1,000 loading cycles and aging tests over three months. It also shows that the fabricated strain sensors have the potential for human voice recognition by characterizing letters, words, and musical tones.

A novel benzoquinone‐azo linked polymer‐based active electrode material for high‐performance symmetric pseudocapacitors

AbstractPseudocapacitors (PSCs) have attracted researcher's attention due to their potential electrochemical performance as the power source for electronic devices. However, to maintain the high electrochemical properties of pseudocapacitive materials becomes critical. Therefore, the active electrode materials design and synthesis is a challenging task. To tackle these problems, herein, we rationally designed new polymer based on benzoquinone with azo linker. The polymer AZO‐BQ‐P was synthesized and tested for their energy storage applications in combination with graphite foil (GF). In three‐electrode supercapacitor (SC) device, the AZO‐BQ‐P/GF electrode exhibits excellent specific capacitance (Csp) of about 306.27 F g−1 at 0.5 A g−1 current density and higher cycling stability. The pseudocapacitive performance of SC cells result from synergistic effect of AZO‐BQ‐P and GF and due to faster electrolyte ion diffusion and increased availability at electrode/electrolyte interfaces. Furthermore, AZO‐BQ‐P/GF electrode was employed to fabricate two‐electrode AZO‐BQ‐P/GF//AZO‐BQ‐P/GF symmetric SC device. The optimal SSC device shows a Csp reaching 200 F g−1 at 0.5 A g−1, which is an impressive value. Also, it exhibits remarkable cycling stability with 86.18% Csp retention after 5000 galvanostatic charging–discharging (GCD) cycles at 3 A g−1. The SSC device applying AZO‐BQ‐P/GF electrode delivers an excellent energy density (ED) of 25.00 Wh kg−1 at 900.00 W kg−1 power density (PD). Thus, the novel polymer design offers efficient electrode materials to enhance the pseudocapacitive electrochemical performance of the SSC device. This concept can be extended for fabricating other electrochemical systems and accelerate its applications for modern electronic devices.

Building microcracked structure fibrous cathode coated by Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) for ultra-stable fiber-shaped aqueous zinc ions batteries

Attributing to the advantages of intrinsic safety, high energy density, and good omnidirectional flexibility, fiber-shaped aqueous zinc ions batteries (FAZIBs), serving as energy supply devices, have multitude applications in flexible and wearable electronic devices. However, the detachment of active materials caused by bending stress generated during flexing process limits their practical application severely. To address the above issue, an effective integrated strategy employing microcracked activated cobalt hydroxide [A-Co(OH)2] cathode with protective coating of poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOT:PSS) was proposed in this work to enhance the cyclic and bending performances of FAZIBs. The microcracked A-Co(OH)2 cathode relieves stress concentration under bending conditions, while the PEDOT:PSS coating is responsible to maintain the structural integrity and prevents the detachment of A-Co(OH)2. The FAZIBs based on a gel electrolyte achieved a high energy density (173.5 Wh·kg−1) at a power density 90 W·kg−1 and a bending durability (94.4 % capacity retention after 500 cycles) as a consequence of the synergistic effect of microcracked A-Co(OH)2 cathode and the PEDOT:PSS coating. This work will offer a new approach for devising high-performance FAZIBs and promote the development of highly flexible and stable fiber-shaped batteries.

Exploring Aromaticity Effects on Electronic Transport in Cyclo[n]carbon Single-Molecule Junctions.

Cyclo[n]carbon (Cn) is one member of the all-carbon allotrope family with potential applications in next-generation electronic devices. By employing first-principles quantum transport calculations, we have investigated the electronic transport properties of single-molecule junctions of Cn, with n = 14, 16, 18, and 20, connected to two bulk gold electrodes, uncovering notable distinctions arising from the varying aromaticities. For the doubly aromatic C14 and C18 molecules, slightly deformed complexes at the singlet state arise after bonding with one Au atom at each side; in contrast, the reduced energy gaps between the highest occupied and the lowest unoccupied molecular orbitals due to the orbital reordering observed in the doubly anti-aromatic C16 and C20 molecules lead to heavily deformed asymmetric complexes at the triplet state. Consequently, spin-unpolarized transmission functions are obtained for the Au-C14/18-Au junctions, while spin-polarized transmission appears in the Au-C16/20-Au junctions. Furthermore, the asymmetric in-plane π-type hybrid molecular orbitals of the Au-C16/20-Au junctions contribute to two broad but low transmission peaks far away from the Fermi level (Ef), while the out-of-plane π-type hybrid molecular orbitals dominate two sharp transmission peaks that are adjacent to Ef, thus resulting in much lower transmission coefficients at Ef compared to those of the Au-C14/18-Au junctions. Our findings are helpful for the design and application of future cyclo[n]carbon-based molecular electronic devices.

Preparation of Semiconducting Films By Electrooxidation of Naphthalene

Due to promising electronic and optical properties, conductive polymers are attracting significant interest. Conductive polymers find applications in electronic devices, e.g. substituted polynaphthalenes are used as blue light sources in OLEDs1. The ability to block the substitution sites where the subsequent polymer unit may be added by functional groups allows the polymer structure to be designed2. Moreover, one of the benefits of conductive polymers is the ability to modify the band gap of these materials by adding substituents to the main chain.Naphthalene, as the smallest polycyclic hydrocarbon, is an interesting precursor for synthesis semiconducting materials. The anodic oxidation of naphthalene has been described several times in the literature3,4, however, only formation of 1,4-polynaphthalene in the form of a granular product has been reported.In our research, we performed naphthalene electrooxidation and investigated the impact of the experimental conditions such as naphthalene concentration, water content, and electrode material on the obtained semiconducting materials. We used mass spectrometry to observe mass progression and determine molecular mass of the obtained polymers. The results of electron microscopy imaging showed fine quality coating. We studied the electronic properties of the polymers by cyclic voltammetry and impedance spectroscopy. Based on the results, we discussed the possible mechanism of the reaction. Samanta, S. K. et al. Synthesis of high molecular weight 1,4-polynaphthalene for solution-processed true color blue light emitting diode. Macromolecules 51, 8324–8329 (2018).Debad, J. F. & Bard, A. J. Electropolymerization of acenaphtho[1,2-k]fluoranthene derivatives: Formation of a new conductive electroactive electrochromic hydrocarbon ladder polymer. J Am Chem Soc 120, 2476–2477 (1998).Zecchin, S., Tomat, R., Schiavon, G. & Zotti, G. Polynaphthylene films from anodic coupling of naphthalene. Synthetic Metals vol. 25 (1988).Huang, Z., Qu, L., Shi, G., Chen, F. & Hong, X. Electrochemical polymerization of naphthalene in the electrolyte of boron trifluoride diethyl etherate containing trifluoroacetic acid and polyethylene glycol oligomer. Journal of Electroanalytical Chemistry 556, 159–165 (2003).

(Invited) Ga2O3 Semiconductor Devices for High-Temperature Operation

Beta phase of gallium oxide (Ga2O3) has attracted a lot of attention as an ultra-wide band gap semiconductor for applications in high-power electronic devices. High power operation often comes with increased temperatures of the devices due to joule heating, especially in semiconductors like Ga2O3with low thermal conductivity. However, electrical performance and reliability of the Ga2O3based diodes and transistors at very high temperature, above 400C, is not well established.In this talk, I will present our recent experimental results on fabrication of Ga2O3semiconductor devices for applications as high-temperature diodes and hydrogen gas sensors. The fabricated Ga2O3/NiO p-n heterojunctions allow for device operation with >100-1000 rectification ratio up to 400-600C [1]. Despite the stable ultrathin Ohmic contact [2], the device performance degrades over tens of temperature cycles and hundreds of hours at these elevated temperatures, likely due to instability of the rectifying contact. We propose and implement alternative interfacial rectifying contact layers, that enable both high performance and long reliability of these high temperature Ga2O3 semiconductor devices.[1] Sohel, Zakutayev et al Physica Status Solidi (a) 220 2300535 (2023)[2] Callahan, Zakutayev et al J. Vac. Sci. Technol. A 41, 043211 (2023)

Ultrarobust, Self-Healing Poly(urethane-urea) Elastomer with Superior Tensile Strength and Intrinsic Flame Retardancy Enabled by Coordination Cross-Linking.

Poly(urethane-urea) elastomers (PUUEs) have gained significant attention recently due to their growing demand in electronic skin, wearable electronic devices, and aerospace applications. The practical implementation of these elastomers necessitates many exceptional properties to ensure robust and safe utilization. However, achieving an optimal balance between high mechanical strength, good self-healing at moderate temperatures, and efficient flame retardancy for poly(urethane-urea) elastomers remains a formidable challenge. In this study, we incorporated metal coordination bonds and flame-retarding phosphinate groups into the design of poly(urethane-urea) simultaneously, resulting in a high-strength, self-healing, and flame-retardant elastomer, termed PNPU-2%Zn. Additional supramolecular cross-links and plasticizing effects of phosphinate-endowed PUUEs with relatively remarkable tensile strength (20.9 MPa), high elastic modulus (10.8 MPa), and exceptional self-healing efficiency (above 97%). Besides, PNPU-2%Zn possessed self-extinguishing characteristics with a limiting oxygen index (LOI) of 26.5%. Such an elastomer with superior properties can resist both mechanical fracture and fire hazards, providing insights into the development of robust and high-performance components for applications in wearable electronic devices.

Beta-Gallium Oxide Material and Device Technologies

Beta-gallium oxide (β-Ga2O3) is a material with a history of research and development spanning about 70 years; however, it has attracted little attention as a semiconductor for a long time. The situation has changed completely in the last ten years, and the world has seen increasing demand for active research and development of both materials and devices. Many of its distinctive physical properties are attributed to its very large bandgap energy of 4.5 eV. Another important feature is that it is possible to grow large bulk single crystals by melt growth. In this article, we first discuss the important physical properties of β-Ga2O3 for electronic device applications, followed by bulk melt growth and thin-film epitaxial growth technologies. Then, state-of-the-art β-Ga2O3 transistor and diode technologies are discussed.

Superconductive and flexible antenna based on a tri-nanocomposite of graphene nanoplatelets, silver, and copper for wearable electronic devices

Printed electronics, fueled by graphene's conductivity and flexibility, are revolutionizing wearable technology, surpassing copper's limitations in cost, signal quality, size, and environmental impact. Graphene-based inks are positioned to lead in this domain, offering cost-effective solutions directly applicable to materials such as textiles and paper. However, graphene encounters a primary drawback due to its lack of an energy band gap, constraining its potential applications in various electronic devices. In this study, we present a novel formulation of a superconductive, flexible leather graphene antenna utilizing a tri-nanocomposite structure of Graphene Nanoplatelet/Silver/Copper (GNP/Ag/Cu), covering a wideband bandwidth from 5.2 GHz to 8.5 GHz. The electrical conductivity of the GNP/Ag/Cu sample was assessed using the four-point probe method. With each additional layer, conductivity increased from 10.473 × 107 S/m to 40.218 × 107 S/m, demonstrating a direct correlation between conductivity and antenna gain. The study evaluates the efficacy of various thicknesses of conductive Graphene (GNP/Ag/Cu) ink on drill fabric. Safety assurance is provided through specific absorption rate (SAR) testing, indicating 0.84 W/kg per 10 g of tissue for an input power of 0.5 W, in compliance with ICNIRP standards for wearable device safety. Additionally, a morphological analysis of the antenna was conducted, showcasing its potential for efficient signal transmission in wearable electronic devices.

Correction to “Fabrication of Highly Transparent Substrates from Waste Materials for Electronic Device Applications”

Correction to “Fabrication of Highly Transparent Substrates from Waste Materials for Electronic Device Applications”