Electronic Materials

A helium ion microscope (HIM) with a focused He⁺-ion beam of variable flux and energy can be used as a tool for local nanoscale surface modification. In this work, we demonstrate a simple but versatile use of the HIM focused He ion beam to fabricate conducting metallic nano- and microstructures on arbitrary substrates of varied types and shapes by directly patterning pre-deposited initially discontinuous and highly insulating (>10 TΩ/sq.) ultrathin metal films. Gold or silver films, measuring 3 nm in thickness, thermally evaporated on solid substrates have a discontinuous nanocluster morphology. Such highly resistive films can be made locally conductive using moderate doses (2 × 10¹⁶–10¹⁷ cm⁻²) of low-energy (30 KeV) ion bombardment. We show that an HIM can be used to directly “draw” Au and Ag conductive lines and other patterns with a variable sheet resistance as low as 10 kΩ/sq. without the use of additional precursors. This relatively straightforward, high-definition technique of direct writing with an ion beam, free from complex in vacuo catalytic or precursor chemistries, opens up new opportunities for directly fabricating elements of conformal metallic nanocircuits (interconnects, resistors, and contacts) on arbitrary organic or inorganic substrates, including those with highly curved surfaces. Full article

An efficient cooling system is necessary for the reliability and safety of modern microchips for a longer life. As microchips become smaller and more powerful, the heat flux generated by these chips per unit area also rises sharply. Traditional cooling techniques are inadequate to meet the recent cooling requirements of microchips. To meet the current cooling demand of microelectromechanical systems (MEMS) devices and microchips, microchannel heat sink (MCHS) technology is the latest invention, one that can dissipate a significant amount of heat because of its high surface area to volume ratio. This study provides a concise summary of the design, material selection, and performance parameters of the MCHSs that have been developed over the last few decades. The limitations and challenges associated with the different techniques employed by researchers over time to enhance the thermal efficiency of microchannel heat sinks are discussed. The effects on the thermal enhancement factor, Nusselt number, and pressure drop at different Reynold numbers in passive techniques (flow obstruction) i.e., ribs, grooves, dimples, and cavities change in the curvature of MCHSs, are discussed. This study also discusses the increase in heat transfer using nanofluids and how a change in coolant type also significantly affects the thermal performance of MCHSs by obstructing flow. This study provides trends and useful guidelines for researchers to design more effective MCHSs to keep up with the cooling demands of power electronics. Full article

In this study, we investigated the density of states extraction method for atomic-deposited ZnO thin-film transistors (TFTs) by analyzing gate-dependent field-effect mobility. The atomic layer deposition (ALD) method offers ultra-thin and smooth ZnO films, but these films suffer from interface and semiconductor defects, which lead to disordered localized electronic structures. Hence, to investigate the unstable localized structure of ZnO TFTs, we tried to derive the electronic state relationship by assuming field-effect mobility can be expressed as a gate-dependent Arrhenius relation, and the activation energy in the relation is the required energy for hopping. Following this derived relationship, the DOS of the atomic-deposited ZnO transistor was extracted and found to be consistent with those using temperature-dependent measurements. Moreover, to ensure the proposed method is reliable, we applied methods for the extraction of DOSs of doped ZnO transistors, which show enhanced mobilities with shifted threshold voltages, and the results show that the extraction method is reliable. Thus, we can state that the mobility-based DOS extraction method offers practical benefits for estimating the density of states of disordered transistors using a single transfer characteristic of these devices. Full article

Waste printed circuit boards (WPCBs) hold great recycling value, but improper recycling can lead to environmental issues. This study combines pyrolysis and microwave technologies, leveraging the unique phenomenon where metal materials tend to “spark” in a microwave field, to develop a microwave pyrolysis process for WPCBs that incorporates metal fillers. The research analyzes the effects of microwave power, metal filler addition, and pyrolysis time on the efficiency of microwave pyrolysis. It explores the mechanisms of microwave pyrolysis and the pathways of pyrolysis product formation, and the kinetics of the pyrolysis reaction of WPCBs. The results indicate that microwave-assisted pyrolysis greatly improves efficiency. Within the experimental range, the optimal conditions are found to be a microwave power of 1600–1800 W, a metal filler addition of 10%, and a pyrolysis time of 10 min. Under these conditions, the yield of pyrolysis liquid was 12.8%, with approximately 5–12 different components, while the yield of pyrolysis gas was 12.7–13.4%, with about 9–11 different components. Compared to conventional pyrolysis products, the liquid products from microwave pyrolysis are simpler and more advantageous for resource utilization. Theoretical calculations show that the average activation energy for the microwave pyrolysis process is 81.05 kJ/mol, with an average reaction order of 0.93, which is greatly better than the 147.75 kJ/mol of the conventional pyrolysis process. Full article

Power modules can occasionally be exposed to brief power peaks, causing overheating and premature failure of the power semiconductor devices. In order to overcome this issue without oversizing the module or its cooling system, this study aims to design a new class of power modules with integrated Phase Change Material (PCM) in a container serving as a top device interconnection. Simulations and experiments are performed with two organic PCMs, and the interest in adding copper foam is discussed. Under various test conditions, the results show that the simulations agree well with the experiments. Hence, virtual prototyping can be very useful for sizing containers based on a specific mission profile. For a constant selected PCM volume (around 1 cm³/device) and with a convection heat transfer coefficient value of 800 W.m⁻².K⁻¹, the solution allows achieving a junction temperature reduction of about 35 °C (erythritol and 90% porosity copper foam) compared to a wire-bonded conventional technique. Repetitive power cycles can be achieved with both materials, but the selection of the PCM should be conducted cautiously based on the mission profile. The two selected organic PCMs show degradation of their latent heat of fusion and mass loss during high-temperature isothermal aging in air above 130 °C. By assuming as endpoint criterion the reduction of energy storage by 50% compared to the initial state, the lifetime of erythritol and RT100 is evaluated to be about 100 and 340 h, respectively, during aging at 150 °C. Full article

Polymer composites are engineered materials that combine polymers with diverse fillers to enhance their physicochemical properties. The electrical conductivity of polymer composites is a vital characteristic that significantly broadens their use, particularly in electronic applications. The addition of ionic liquids into polymer composites represents a new method to enhance their functional properties, particularly in terms of electrical conductivity. In this brief review, several polymer matrices, conductive fillers, and ionic liquids utilized in polymer composites are categorized. Additionally, the effect of ionic liquids on the electrical conductivity of polymer composites is concisely explained. This review gives brief information that increases the understanding of electrical conductivity in polymer composites containing ionic liquids. In summary, most studies show that adding ionic liquids enhances the electrical conductivity of polymer composites regardless of the polymer matrix or conductive filler type. This enhancement is due to ionic liquids improving filler dispersion and promoting the creation of effective three-dimensional conductive networks within the matrix, thus boosting electron transport and mobility throughout the structure. This review provides new insights into the behavior of ionic liquids in composite systems, highlighting their role in improving properties for advanced applications. It encourages innovation in next-generation conductive materials and assists future research and development of more efficient materials for electronics. Full article

We have investigated the influence of the relative proportions of glass formers in a series of lithium alumino-borosilicate glasses with respect to electrical conductivity (σ) and glass transition temperature (T_g) as functions of glass structure, as determined using Raman spectroscopy. The ternary lithium alumino-borate glass exhibits the highest σ and lowest T_g among all the compositions of the glass series, 30Li₂O•3Al₂O₃• (67−x) B₂O₃•xSiO₂. However, as B₂O₃ is replaced by SiO₂, a shallow minimum in σ, as well as a shallow maximum in T_g, are observed near x = 27, where the Raman spectra indicate that isolated diborate/tetraborate/orthoborate groups are being progressively replaced by danburite/reedmergnerite-like borosilicate network units. Overall, as the glasses become silica-rich, σ is minimized, while T_g is maximized. In general, these findings show correlations among T_g (sensitive to network polymerization), σ (proportional to ionic mobility), and the different borate and silicate glass structural units as determined using Raman spectroscopy. Full article

In this work, a gate insulator poly (4-vinylphenol) (PVP) of an organic field effect transistor (OFET) was deposited using an inkjet printing technique, realized via a high printing resolution. Various parameters, including the molecular weight of PVP, printing direction, printing voltage, and drop frequency, were investigated to optimize OFET performance. Consequently, PVP with a smaller molecular weight of 11 k and a printing direction parallel to the channel, a printing voltage of 18 V, and a drop frequency of 10 kHz showed the best OFET performance. With a direct ink writing-printed organic semiconductor, this work paves the way for fully inkjet-printed OFETs. Full article

This work presents a copper zinc tin sulfide (CZTS)-based solar cell structure (AI/ITO/C₆₀/CZTS/SnS/Pt) with C₆₀ as a buffer layer, developed using the SCAPS-1D simulator by optimizing each parameter to calculate the output. Optimizing the parameters, the acceptor concentration and thickness were altered from 6.0 × 10¹⁵ cm⁻³ to 6.0 × 10¹⁸ cm⁻³ and 1500 nm to 3000 nm, respectively. Although, in this simulator, we can tune the value for the acceptor concentration to 6.0 × 10²², higher doping might present an issue regarding adjustment in the physical experiment. Thus, tunable parameters need to be chosen according to the reliability of the experimental work. The defect density varied from 1.0 × 10¹⁴ cm⁻³ to 1.0 × 10¹⁷ cm⁻³ and the auger hole/electron capture coefficient was determined to be 1.0 × 10⁻²⁶ cm⁶ s⁻¹ for the maintenance of the minorities in theoretical to quasi-proper experimental measurements. Although the temperature was intended to be kept near room temperature, this parameter was varied from 290 K to 475 K to investigate the effects of the temperature on this cell. The optimization of the proposed structure resulted in a final acceptor concentration of 6.0 × 10¹⁸ cm⁻³ and a thickness of 3000 nm at a defect density of 1.0 × 10¹⁵ cm⁻³, which will help to satisfy the desired experimental performance. Satisfactory outcomes (V_OC = 1.24 V, J_SC = 27.03 mA/cm², FF = 89.96%, η = 30.18%) were found compared to the previous analysis. Full article

In this paper, a new method for evaluating hot-electron degradation in p-GaN gate AlGaN/GaN power HEMTs is proposed. The method exploits a commercial parameter analyzer to study V_TH and R_ON drifts induced by on-state stress at V_DS = 50 V. The results show that V_TH drift and part of the R_ON degradation induced by the on-state stress are recoverable and likely due to the ionization of C-related acceptors in the buffer. This was confirmed by a preliminary characterization of C-related buffer traps. Conversely, the remaining part of R_ON degradation (not recovered in 1000 s) was strongly affected by the surface treatment. The current level set during on-state stress affected the amount of non-recoverable degradation, confirming the involvement of hot electrons. Thanks to the monitoring of the parameters’ recovery, the proposed method provides important insights into the physical mechanisms governing the parameters’ degradation. This extends the capabilities of state-of-the art systems, without the need for custom setup development. Full article

Conductive hydrogels combine the properties of both hydrogels and conductors, making them soft, flexible, and biocompatible. These properties enable them to conform to irregular surfaces, stretch and bend without losing their electrical conductivity, and interface with biological systems. Conductive hydrogels can be utilized as conductive traces, electrodes, or as a matrix for flexible electronics. Exciting applications in sensors, tissue engineering, and human-machine interaction have been demonstrated worldwide. This review comprehensively covers the progress in this field, focusing on several main aspects: functional materials, performance improvement strategies, and wearable applications in human-related areas. Furthermore, the major approaches and challenges for improving their mechanical properties, conductivity, and long-term stability are systematically summarized. Full article

The rising demand for increased integration and higher power outputs poses a hidden risk to the long-term reliable operation of third-generation semiconductors. Thus, the power cycling test (PCT) is widely regarded as the utmost critical test for assessing the packaging reliability of power devices. In this work, low-thermal-resistance packaging design structures of SiC devices are introduced, encompassing planar packaging with dual heat dissipation, press-pack packaging, three-dimensional (3D) packaging, and hybrid packaging. PCT methods and their control strategies are summarized and discussed. Direct-current PCT is the focus of this review. The failure mechanisms of SiC devices under PCT are pointed out. The electrical and temperature-sensitive parameters adopted to monitor the aging of SiC devices are organized. The existing international standards for PCT are evaluated. Due to the lack of authoritative statements for SiC devices, it is difficult to achieve comparison research results without consistent preconditions. Furthermore, the lifetimes of the various packaging designs of the tested SiC devices under PCTs are statistically analyzed. Additionally, problems related to parameter monitoring and test equipment are also summarized. This review explores the broader landscape by delving into the current challenges and main trends in PCTs for SiC devices. Full article

In this study, the bipolar switching behaviors in ZnO/HfO₂ bilayer resistive random-access memory (RRAM), depending on different metal top electrodes (TE), are analyzed. For this purpose, devices with two types of TE–TiN/Ti and Pd, which have varying oxygen affinities, are fabricated. X-ray diffraction (XRD) analysis shows that ZnO has a hexagonal wurtzite structure, and HfO₂ exhibits both monoclinic and orthorhombic phases. The average grain sizes are 10.9 nm for ZnO and 1.55 nm for HfO₂. In regards to the electrical characteristics, the I–V curve, cycling test, and voltage stress are measured. The measurement results indicate that devices with TiN/Ti TE exhibit lower set and higher reset voltage and stable bipolar switching behavior. However, a device with Pd TE demonstrates higher set and lower reset voltage. This phenomenon can be explained by the Gibbs free energy of formation (∆G_f°). Additionally, the Pd TE device shows unstable bipolar switching characteristics, where unipolar switching occurs simultaneously during the cycling test. This instability in devices with Pd TE could potentially lead to soft errors in operation. For guaranteeing stable bipolar switching, the oxygen affinity of material for TE should be considered in regards to ZnO/HfO₂ bilayer RRAM. Full article

All-inorganic perovskite semiconductors have received significant interest for their potential stability over heat and humidity. However, the typical CsPbI₃ displays phase instability despite its desirable bandgap of ~1.73 eV. Herein, we studied the mixed halide perovskite CsPbI₂Br by varying the silver doping concentration. For this purpose, we examined its bandgap tunability as a function of the silver doping by using density functional theory. Then, we studied the effect of silver on the structural and optical properties of CsPbI₂Br. Resultantly, we found that ‘silver doping’ allowed for partial bandgap tunability from 1.91 eV to 2.05 eV, increasing the photoluminescence (PL) lifetime from 0.990 ns to 1.187 ns, and, finally, contributing to the structural stability when examining the aging effect via X-ray diffraction. Then, through the analysis of the intermolecular interactions based on the solubility parameter, we explain the solvent engineering process in relation to the solvent trapping phenomena in CsPbI₂Br thin films. However, silver doping may induce a defect morphology (e.g., a pinhole) during the formation of the thin films. Full article

The functionalization of conductive inks has been carried out through the decomposition of hydrogen peroxide (H₂O₂) onto the surface of silver nanoparticles (AgNPs). The ink prepared using this eco-friendly chemical reagent has been characterized structurally, chemically, and morphologically, showing the presence of stable AgNPs with suitable properties as well as the absence of residual contamination. The electrical conductivity of such a solution-processable ink is evidenced for patterns designed on flexible photographic paper substrates, using a refillable fountain pen that is implemented as a printing mechanism for the fabrication of simple printed circuit boards (PCBs). The functionality and durability of the tested systems are demonstrated under various mechanical constraints, aiming to basically reproduce the normal operation conditions of flexible electronic devices. The obtained results indicate that the implementation of these AgNP-based inks is relevant for direct applications in inkjet printing technology, thus paving the way for the use of greener chemicals in ink preparation. Full article

The impact of N₂ purging in the CdS deposition bath and subsequent N₂ annealing is examined and contrasted with conventional CdS films, which were deposited without purging and annealed in ambient air. All films were fabricated using the chemical bath deposition method at a temperature of 80 °C on fluorine-doped tin oxide glass slides (FTO). N₂ purged films were deposited by introducing nitrogen gas into the deposition bath throughout the CdS deposition process. Subsequently, both N₂ purged and un-purged films underwent annealing at temperatures ranging from 100 to 500 °C for one hour, either in a nitrogen or ambient air environment. Photoelectrochemical (PEC) cell studies reveal that films subjected to both N₂ purging and N₂ annealing exhibit a notable enhancement of 37.5% and 27% in I_SC (short-circuit current) and V_OC (open-circuit voltage) values, accompanied by a 5% improvement in optical transmittance compared to conventional CdS thin films. The films annealed at 300 °C demonstrate the highest I_SC, V_OC, and V_FB values, 55 μA, 0.475 V, and −675 mV, respectively. The improved optoelectrical properties in both N₂-purged and N₂-annealed films are attributed to their well-packed structure, enhanced interconnectivity, and a higher sulfur to cadmium ratio of 0.76 in the films. Full article

This article investigates resistive random access memory (ReRAM) crossbar memory arrays, which is a notable development in non-volatile memory technology. We highlight ReRAM’s competitive edge over NAND, NOR Flash, and phase-change memory (PCM), particularly in terms of endurance, speed, and energy efficiency. This paper focuses on the architecture of crossbar arrays, where memristive devices are positioned at intersecting metal wires. We emphasize the unique resistive switching mechanisms of memristors and the challenges of sneak path currents and delve into the roles and configurations of selectors, particularly focusing on the one-selector one-resistor (1S1R) architecture with an insulator–metal transition (IMT) based selector. We use SPICE simulations based on defined models to examine a 3 × 3 1S1R ReRAM array with vanadium dioxide selectors and titanium dioxide film memristors, assessing the impact of ambient temperature and critical IMT temperatures on array performance. We highlight the operational regions of low resistive state (LRS) and high resistive state (HRS), providing insights into the electrical behavior of these components under various conditions. Lastly, we demonstrate the impact of selector presence on sneak path currents. This research contributes to the overall understanding of ReRAM crossbar arrays integrated with IMT material-based selectors. Full article

In this work, we demonstrate the preparation of easy-to-fabricate nanogranular strontium ferromolybdate/strontium molybdate core-shell ceramics and examine their properties, including tunnel magnetoresistance, magnetic field sensitivity, and temperature coefficient of the tunnel magnetoresistance. The tunnel magnetoresistance of nanogranular strontium ferromolybdate/strontium molybdate core-shell ceramics was modeled, yielding values suitable for magnetoresistive sensor applications. Such structures possess a narrow peak of magnetic flux sensibility located at about 80 mT. For magnetic flux measurement, single-domain granules with superparamagnetic behavior should be applied. The predicted TMR magnetic flux sensitivities for granules with superparamagnetic behavior amount to about 7.7% T⁻¹ and 1.5% T⁻¹ for granule sizes of 3 nm and 5 nm, respectively. A drawback of the tunnel magnetoresistance of such nanogranular core-shell ceramics is the unacceptably large value of the temperature coefficient. Acceptable values, lower than 2% K⁻¹, are obtained only at low temperatures (less than 100 K) or large magnetic flux densities (exceeding 6 T). Therefore, a Wheatstone bridge configuration should be adopted for magnetoresistive sensor design to compensate for the effect of temperature. Full article

A triboelectric nanogenerator (TENG) is one of the most significantly innovative microdevices for built-in energy harvesting with wearable and portable electronics. In this study, the forcespinning technology was used to synthesize a nanofiber (NF) mat-based TENG. Polyvinylidene fluoride (PVDF) membrane was used as the negative triboelectric electrode/pole, and chemically designed and functionalized thermoplastic polyurethane (TPU) was used as the positive electrode/pole for the TENG. The electronic interference, sensitivity, and gate voltage of the synthesized microdevices were investigated using chemically modified bridging of multi-walled carbon nanotubes (MWCNT) with a TPU polymer repeating unit and bare TPU-based positive electrodes. The chemical functionality of TPU NF was integrated during the NF preparation step. The morphological features and the chemical structure of the nanofibers were characterized using a field emission scanning electron microscope and Fourier-transform infrared spectroscopy. The electrical output of the fabricated MWCNT-TPU/PVDF TENG yielded a maximum of 212 V in open circuit and 70 µA in short circuit at 240 beats per minute, which proved to be 79% and 15% higher than the TPU/PDVF triboelectric nanogenerator with an electronic contact area of 3.8 × 3.8 cm², which indicates that MWCNT enhanced the electron transportation facility, which results in significantly enhanced performance of the TENG. This device was further tested for its charging capacity and sensory performance by taking data from different body parts, e.g., the chest, arms, feet, hands, etc. These results show an impending prospect and versatility of the chemically functionalized materials for next-generation applications in sensing and everyday energy harvesting technology. Full article