Modern Electronic Devices Research Articles

Carbon nanotube-vertical edge rich graphene hybrid sponge as multifunctional reinforcements for high performance epoxy composites

Thermal management materials with excellent electromagnetic interference (EMI) shielding performance have attracted research interest in the field of modern electronic devices. Herein, vertical edge rich graphene (VG) was in-situ grafted on the carbon nanotube (CNT) sponge to create connective 3D hybridized carbon skeleton with covalent bonding, then CNT-VG/epoxy composites were constructed to meet the needs of multifunctional application. Impressively, mainly owing to the connectivity of 3D CNT sponge, the conduction ability of interfaces and the defect-rich structure of VG, the obtained CNT-VG/epoxy composites possessed an enhanced EMI shielding effectiveness of 46.9 dB with a thickness of 1 mm and an improved thermal conductivity of 2.23 W m−1 K−1 which contributes to superior thermal management capability. In addition, the excellent structural design also increases the flexural strength by 349.39% compared to pure epoxy resin, achieving a flexural strength of 275.32 MPa and a work of fracture of 9956.98 kJ m−3. The novel multifunctional CNT-VG/epoxy composites with enhanced mechanical property show a bright application prospect in next-generation electronic devices.

Free fall drop impact analysis of board level electronic packages

The electronic failure from accidental dropping event of modern handheld electronic devices may result from various failure modes such as cracking of PCB, solder joint etc. In this work, the dynamic response characteristics of electronic packages when subjected to board level drop impacts are investigated. Initially, board level drop tests are conducted on a custom made PCB as per JEDEC standard using a drop test apparatus. A Finite Element model of the free fall drop phenomenon is developed and numerical simulation is carried out using ANSYS 16.0 software based on two simplified Finite Element (FE) methods (Input-G method and Support Excitation Scheme) reported in the literatures are compared with experimental results to identify the most suitable FE method in terms of accuracy of the results produced. Using the identified FE method, the dynamic responses of PCBs with three different support configurations commonly used are analyzed to identify the best possible support configuration that can with stand drop impact loads better.

Coupling of ferroelectric and valley properties in 2D materials

Two-dimensional (2D) valleytronic materials are both fundamentally intriguing and practically appealing to explore novel physics and design next-generation devices. However, traditional control means such as optic pumping or magnetic field cannot meet the demands of modern electron devices for miniaturization, low-dissipation, and non-volatility. Thus, it is attractive to combine the ferroelectric property with valley property in a single compound. In this paper, the recent progress of ferroelectric-valley coupling is reviewed. First, we briefly recall the development of valleytronics in the past several years. Then, various structures demonstrating ferroelectric-valley coupling, including heterostructures and intrinsic materials, are introduced. Subsequently, we describe ferroelectric-valley coupling in sliding and adsorption system and the unconventional ferroelectricity in the moiré system. Finally, we discuss the research status and outlook. We hope that this perspective will be helpful to bridge the gap between valleytronics and ferroelectrics in 2D materials and inspire further exciting findings.

High performance EMI shielding applications of Co0.5Ni0.5CexSmyFe2-x-yO4 nanocomposite thin films

The fast development in the compact and wearable opto-electronics devices need a high-performance electromagnetic (EM) shielding materials that are shows a unique feature like lightweight and flexible in characteristics that increase the problems of electromagnetic pollution. At present technological aspects, the absorption predominant microwave shielding materials are gain the huge demand for preventing the major problems of electromagnetic interference over the modern electronic devices as well as environment. In the report we presents synthesis of multifunctional composite thin film material that adequately includes the exceptional EMI shielding, mechanical flexibility and magnetic properties of composite thin film for portable and wearable electronic devices which could be operated at GHz frequencies. The Co0.5Ni0.5CexSmyFe2-x-yO4 (denoted as CNCSF) its scanning electron microscopy (SEM) micrographs revel the fact that the samples highly agglomerated characteristics features of the prepared thin film samples, this agglomerated structure of the composite film will enhance the EMI shielding performances and strain sensing responses. Further, the prepared thin films were subjected to characterized XRD and Raman spectroscopic techniques to analyse the crystallinity and different functional groups present in the prepared thin films. By doping of samarium and cesium nanoparticles into the Co0.5Ni0.5Fe2-x-yO4 forms the superior conducting islands and enhances the dielectric and magnetic properties of the composite thin films. Owing to the improved dielectric and magnetic properties this x,y = 0.02 ferrites based thin film nanocomposite with the 0.4 mm thickness exhibit the absorption predominated outstanding electromagnetic shielding responses in the order of −23 dB which is almost equal to 99.67% of shielding efficiency in broad band microwave frequencies. Furthermore, these material-based nanocomposite shields show exceptional stability in EMI shielding efficiency under the different mechanical stretching strains. In addition to superior excellent shielding material, this material-based nanocomposite thin film shows an exceptional strain sensing behaviour, which evident that multifunctional applications of this ferrites based thin material. Owing to the all-unique properties like light weight, flexibility, outstanding EMI-SE and excellent strain sensing behaviour, these ferrites-based material thin film could be employed in flexible and fortable electronic devices as crafty jacket on shield.

Spintronic Terahertz Emitters in Silicon-Based Heterostructures

Integration of active elements into silicon wafers is the first step towards their usage in modern electronic devices based on nanometric structures. Spintronic terahertz emitters, typically composed of nanometer-thin magnetic multilayer, have the outstanding capability of producing high-quality, broadband terahertz pulses using extremely simple heterostructures. A question remains on whether an efficient and cheap integration with other silicon-based technologies can be achieved. We show here that simply having a ferromagnetic layer on silicon produces remarkably efficient spintronic terahertz emission despite the low spin-orbit coupling of the individual components. We achieve this by leveraging on the natural formation of silicides at the interface of a transition metal and silicon. The cobalt silicide layer has good spin-to-charge conversion efficiency that reaches around 1/6 as that of the prototypical spintronics THz-emitter heterostructure cobalt/platinum.

Core-shell Cu@Al2O3 fillers for enhancing thermal conductivity and retaining electrical insulation of epoxy composites

Heat accumulation has emerged as a critical issue that affects the performance and reliability of modern electronic devices in their evolving toward miniaturization, high power density and high integration. The application of thermal interface materials (TIMs) as a thermal management strategy is commonly employed to tackle this problem. Herein, we report the development and characterization of highly thermally conductive but electrically insulating Cu@Al2O3/epoxy composites. Stemming from the excellent thermal conductivity of Cu, the Cu@Al2O3/epoxy composites exhibit thermal conductivity of 1.32 W/m·K at 10 vol% filler content, which is nearly 7 times higher than that of the epoxy resin. Simultaneously, the Cu@Al2O3/epoxy composites still retain a high electrical resistivity of 2.3 × 1013 Ω·cm, which is 6 orders of magnitude greater than that of Cu/epoxy composites without Al2O3 barrier layers, because the dense nanoscale insulating Al2O3 shell effectively inhibits the electron transfer. In addition, the Cu@Al2O3/epoxy composites possess lower dielectric constant and dielectric loss, and better mechanical properties than those of Cu/epoxy composites.

Carbon Nanotube-Fastened Graphene Composites with Bubble-Induced Multireflections for Electromagnetic Interference Shielding with Water Repellence

The use of light and flexible electromagnetic interference (EMI) shielding materials, particularly those considered for water repellence, is crucial in managing radiation pollution for modern electronic devices. However, the limited flexibility, weight, and water repellence of available shields constrain their applications. Herein, we demonstrated the potential of a carbon nanotube-fastened graphene composite film for EMI shielding, whose surface is adhered by a thin hydrophobic SiO2 coating. The reduced graphene with a curve and fastened morphology could be stored and form interconnected bubbles in the interior. Thus, the obtained film with flexibility and a thin thickness presents extremely high EMI shield performance of 76.4 dB due to anomalous multireflections in the interconnected bubbles, essentially different from shields that mainly reflect electromagnetic waves on a surface. In addition, the reliable roughness results in strong adhesion of the hydrophobic coating on a surface and demonstrates stable water repellence, even in severe conductions. The superhydrophobic film is a promising shield that could solve critical pollution for modern electronic devices.

Characterization of Mechanical and Electrical Properties of Polystyrene Composite Reinforced by Hybrid Reinforcement Filler

Nowadays, electrically conductive polymer plays some important roles in the modern electronic devices because the crucial importance in telecommunication and biosensors. This type of materials offers an obvious decrease in the weight of the devices and it also has an environmental compatibility. A conductive polymer composite is promising alternative materials that has several advantages in the electronic applications currently. Polyester was used as a matrix, and copper –Tin /Zink inform of particulates with Copper short wires were considered electrically conductive fillers. The study prepared two groups (A and B) using different filler materials (Cu- Tin /Zink - Polyester and Cu- Tin /Zink –Cu- short wires / Polyester) with a weight fraction percentage of up to 50%. A composite processing method was slip casting to produce rectangular and cylindrical samples; after that samples were cured at room temperature for 48 hrs. Produced samples from both mixed were tested for density, ultimate tensile strength and scan electron microscope. AC conductivity test were performed for all samples using a frequency range from 50 Hz to 50 MHz to measure the dielectrically loss factor and electrical conductivity. From the study, it has been found that filler powder almost proved better ultimate strength behavior, and the peak value was determined at 30% wt., while short wires above 40 % wt. can cause a dramatic reduction in tensile strength. The results revealed that short wires filler van improves the electrical conductivity by approximately 50%; when compared with using particulate filler only. The result from the microstructure showed that short wires with metals powder could provide a connected network for improving the conductivity in the polymer matrix.

A critical review on wireless power transfer systems using metamaterials

Recently, wireless power transfer (WPT) has been a topic of interest due to its attractive applications in modern life. Starting from Tesla’s idea about a century ago, WPT has developed tremendously and appeared in many of the most modern electronic devices. However, some WPT systems still have limitations such as short transmission distance, low transfer efficiency, and electromagnetic leakage. Magnetic metamaterial (MM) is a potential candidate that can overcome the above disadvantages of WPT. This paper is intended to present an overview of recent advances and research progress on WPT systems. Three classes of WPT consisting of short-range, mid-range, and long-range, will be analyzed in detail both in terms of fundamentals and applications. Especially, MM configurations can be used to enhance the near-field WPT efficiency and reduce the leakage of electromagnetic field will also be evaluated. This article is expected to provide a comprehensive review of the mechanism and applications as well as the future development of metamaterial-based WPT systems.

Electrical studies of thermally annealed reduced graphene oxide-polymer nanocomposites

Resistive memory devices based on organic materials embedded with polymers have attracted growing attention in modern electronic and optoelectronic devices. Herein, a simple and cost effective methods are employed for the successful synthesis of graphene oxide (GO) and reduced graphene oxide (rGO) and exploited for non-volatile resistive memory application. Resistive switching characteristics of rGO-PVDF polymer nanocomposites (PNCs) sandwiched between top electrode copper (Cu) and bottom electrode (ITO/PET), is investigated here and the fabricated device Cu/rGO-PVDF/ITO shows excellent bipolar resistive switching behavior. The device shows VSET ∼ -5.61 V and VRESET ∼ 5.99 V, with ION/IOFF ∼ 102. Different optical, structural, and morphological investigations are also reported here to analyze the material behaviour.

Dominant Energy Carrier Transitions and Thermal Anisotropy in Epitaxial Iridium Thin Films

AbstractHigh aspect ratio metal nanostructures are commonly found in a broad range of applications such as electronic compute structures and sensing. The self‐heating and elevated temperatures in these structures, however, pose a significant bottleneck to both the reliability and clock frequencies of modern electronic devices. Any notable progress in energy efficiency and speed requires fundamental and tunable thermal transport mechanisms in nanostructured metals. In this work, time‐domain thermoreflectance is used to expose cross‐plane quasi‐ballistic transport in epitaxially grown metallic Ir(001) interposed between Al and MgO(001). Thermal conductivities ranges from roughly 65 (96 in‐plane) to 119 (122 in‐plane) W m−1 K−1 for 25.5–133.0 nm films, respectively. Further, low defects afforded by epitaxial growth are suspected to allow the observation of electron–phonon coupling effects in sub‐20 nm metals with traditionally electron‐mediated thermal transport. Via combined electro‐thermal measurements and phenomenological modeling, the transition is revealed between three modes of cross‐plane heat conduction across different thicknesses and an interplay among them: electron dominant, phonon dominant, and electron–phonon energy conversion dominant. The results substantiate unexplored modes of heat transport in nanostructured metals, the insights of which can be used to develop electro‐thermal solutions for a host of modern microelectronic devices and sensing structures.

Thermal spin molecular logic gates modulated by an electric field

Logic gates are fundamental structural components in all modern digital electronic devices. Here, nonequilibrium Green’s functions are incorporated with the density functional theory to verify the thermal spin transport features of the single-molecule spintronic devices constructed by a single molecule in series or parallel connected with graphene nanoribbons electrodes. Our calculations demonstrate that the electric field can manipulate the spin-polarized current. Then, a complete set of thermal spin molecular logic gates are proposed, including AND, OR, and NOT gates. The mentioned logic gates enable different designs of complex thermal spin molecular logic functions and facilitate the electric field control of thermal spin molecular devices.

NiAl-Cl LDH in-situ grown on graphene oxide by a one-step hydrothermal method towards high performance cathode of supercapacitor

To meet the demands of modern vehicles and electronic devices, an increasing number of new materials for the cathode of high-performance supercapacitors have been studied in depth. Here, GO/NA-Cl composites were successfully fabricated by in-situ grow NiAl layered double hydroxide (NiAl LDH) nanosheets on graphene oxide (GO) flakes through one-step hydrothermal procedure for the cathode of supercapacitor. The image of scanning electron microscopy (SEM) exhibited that the NiAl-Cl LDH nanosheets were evenly and vertically arranged on the GO flakes and interlaced to form a network structure, presenting a considerable surface area, which afford abundant active sites in contact with the electrolyte and alleviate the expansion of GO/NA-Cl during the process of electrochemical reaction to improve its stability. The results of electrochemical test show that the GO/NA-Cl is a typical pseudocapacitive material, which provides a prominent specific capacity of 1573 F/g at 1 A/g, and superior rate property (the rate of capacity retention is 62% even at 20 A/g). Furthermore, the GO/NA-Cl electrode shows a superior cycling life after 1000 cycles at 1 A/g with about 80% capacitance retention.

Improved Dielectric Permittivity and Energy Density of Layered Polymer Composites through the Incorporation of Ultralow Amounts of RGO@BTO Hybrid Nanosheets

Polymer dielectric composites are extensively used in modern electronic devices because of their extremely high power density. However, unfavorable coupling between breakdown strength and dielectric permittivity can make achieving high energy density a challenge. In this study, reduced graphene oxide @ barium titanate (RGO@BTO) hybrid nanosheets have been fabricated and utilized as fillers in the design of RGO@BTO/P(VDF-HFP) single-layer films. An increase in permittivity to 24.8@10 kHz, i.e., equivalent to 253% of the P(VDF-HFP) (∼9.8@10 kHz) matrix, has been achieved with only 1 wt % RGO@BTO nanofillers due to the formation of microcapacitors. Furthermore, the RGO@BTO/P(VDF-HFP) film is hot-pressed with a PEI film and a P(VDF-HFP) film, forming a trilayer structure. Consequently, this trilayer film displays a high breakdown strength of 478 kV/mm, a high energy density of 8.25 J/cm3, and a satisfactory efficiency of 64.3%. Thus, this study provides an efficient route for designing polymer composites that combine high energy density with high permittivity.

Terahertz response of ultrafast spin polarization in semi-insulating GaAs

Due to its high sensitivity and time-resolved ability, terahertz time-domain spectroscopy is a powerful tool for investigating ultrafast carrier dynamics in semiconductors. In addition to charges, spins of ultrafast carriers provide an alternate degree of freedom to design modern electronic devices but are rarely studied by terahertz time-domain spectroscopy. Here, ultrafast spin polarization in semi-insulating GaAs is studied by optical-pump terahertz-probe experiments at room temperature. We used circularly and linearly polarized femtosecond laser pulses to inject nonequilibrium carriers in GaAs and observed that both the transmitted and reflected terahertz signals exhibited different dynamical evolutions under the excitations of linearly and circularly polarized laser pulses, which are ascribed to the generation and relaxation of spin-polarized electrons. The lifetime of the ultrafast spin polarization was obtained from our experiments, highlighting the potentialities of terahertz spectroscopy for the investigation of spin relaxation in semiconductors.

Achieving high-efficiency electrically insulating ceramic layer formed on SiCp/Al composite by bipolar pulsed PEO for novel integrated strategy

Thermal conductive insulating ceramic materials are urgently needed in the packaging applications for modern electronic devices owing to their multi-functionality. The electrically insulating Al2O3 ceramics with large thickness and high compactness is designed on SiCp/Al baseplate via plasma electrolytic oxidation (PEO) technique, which provides a new idea for the package structure of the IGBT power module. However, porous characteristics of PEO inorganic ceramics hinder effective electrical insulation and heat conduction in practical applications. Herein, the bipolar pulsed (BP) and unipolar pulsed (UP) PEO are tailored to obtain the ceramics respectively. In contrast, the BP mode enables the ceramic layer significantly thickened and densified due to the soft sparking discharge. Combined with outstanding electrical resistivity over 1012 Ω·cm, high breakdown voltage of 716 ± 38 V, high dielectric strength of 15.9 ± 0.8 V/μm, the BP ceramic layer exhibits superior performance in electrical insulation. Moreover, the BP shows excellent thermal cycling stability (>200 cycles), quite good thermal stability, and dielectric stability in the temperature range of 25 °C to 300 °C to realize high-temperature electrical insulation. This work paves a novel way to design and optimize power electronic module package materials and structures.

Selective PD Measurements on DC Cable Joints Using a HFCT-Balanced Circuit Arrangement

Due to the many advantages of medium-voltage (MV) and high-voltage (HV) DC cable transmission lines and the possibility of converting AC transmission to DC transmission, this technology is becoming increasingly relevant. One of the most important diagnosis tools used to investigate the condition of the insulation of highvoltage cables is to apply partial discharge (PD) measurements. Cable joints and terminations are of particular importance, as these represent weak spots due to human interaction. Especially under DC voltage, it is of crucial importance to determine whether the detected PD pulses occur inside or outside the cable accessories.For this purpose, a PD test method for cable joints using two high-frequency current transformers (HFCT) was optimized with modern electronic devices, including an instrumentation amplifier and a modern PD measuring instrument. Two HFCT with opposite winding directions were placed on the outer semi-conductive layer on both sides of a cable joint. The signals were fed into an instrumentation amplifier to separate the PD pulses originating from inside and outside the cable joint. This method automatically suppresses PD pulses occurring outside the cable joint and was tested on a 12/20 kV AC cable joint under DC voltage and with thermal and electrical stress.

Unique Conduction Band Minimum of Semiconductors Possessing a Zincblende-Type Framework.

Tetrahedral semiconductors such as Si adopt a diamond-type crystal structure with low packing density arising from open cavities in the crystallographic space. By taking LiAlGe as an example, we propose a zincblende-type framework as a platform for semiconductors possessing electroactive cavities. LiAlGe adopts a half-Heusler-type crystal structure including an ordered diamond-type sublattice (zincblende-type) (AlGe) and is an indirect semiconductor with a band gap of ∼0.1 eV. The conduction band minimum (CBM) is uniquely located at the cavity space surrounded by four cations (Al4) in real space. The bond ionicity and cation (Al) p orbitals located around the Fermi energy are requisite for the CBM to float in the cavity space. DFT calculations indicate the conversion of the semiconductor to a semimetallic electride under a pressure of ∼8 GPa, which is accompanied by band gap collapse due to electron transfer from valence band maximum to the cavity space. The high-pressure electride of LiAlGe formed under a very small critical pressure is derived from the presence of inherent crystallographic cavities having deep orbital levels energetically. This finding suggests the possible utilization of electroactive cavity spaces in tetrahedral semiconductors, which are widely used in modern electronic devices.

Development of a Smartphone-Based Expert System for COVID-19 Risk Prediction at Early Stage.

COVID-19 has imposed many challenges and barriers on traditional healthcare systems due to the high risk of being infected by the coronavirus. Modern electronic devices like smartphones with information technology can play an essential role in handling the current pandemic by contributing to different telemedical services. This study has focused on determining the presence of this virus by employing smartphone technology, as it is available to a large number of people. A publicly available COVID-19 dataset consisting of 33 features has been utilized to develop the aimed model, which can be collected from an in-house facility. The chosen dataset has positive and negative samples, demonstrating a high imbalance of class populations. The Adaptive Synthetic (ADASYN) has been applied to overcome the class imbalance problem with imbalanced data. Ten optimal features are chosen from the given 33 features, employing two different feature selection algorithms, such as K Best and recursive feature elimination methods. Mainly, three classification schemes, Random Forest (RF), eXtreme Gradient Boosting (XGB), and Support Vector Machine (SVM), have been applied for the ablation studies, where the accuracy from the XGB, RF, and SVM classifiers achieved , , and , respectively. As the XGB algorithm confers the best results, it has been implemented in designing the Android operating system base and web applications. By analyzing 10 users’ questionnaires, the developed expert system can predict the presence of COVID-19 in the human body of the primary suspect. The preprocessed data and codes are available on the GitHub repository.

Aramid nanofiber-induced assembly of graphene nanosheets toward highly thermostable and freestanding films for electromagnetic interference shielding

Graphene nanosheets (GNSs) hold tremendous potential for electromagnetic interference (EMI) shielding applications. However, fabricating highly conductive freestanding GNS shielding films remains challenging due to their poor dispersion and weak film-forming ability. Herein, aramid nanofibers (ANFs) were used as both a dispersant and binder to address the dispersion and film-forming problem of GNSs. Only 20 wt% ANF yielded a homogeneous GNS dispersion without precipitation after standing for 100 days. The resultant GNS/ANF films exhibited ultraflexibility and high electrical conductivity (12141.5 S/m). A superior EMI shielding effectiveness of 35.6 dB was achieved for the GNS/ANF films (20 μm thick). The GNS/ANF films also exhibited excellent thermostability and nonflammability. This study opens an avenue for the assembly of GNSs into highly conductive freestanding films, showing strong potential applications in EMI shielding for modern high-power electronic devices.