Metal Oxide Layer Research Articles

Bottom-up Filling of Nanosized Trenches with Silver to Fabricate Transparent Conducting Electrodes

Transparent conducting electrodes (TCEs) are essential in many optoelectronic devices including solar cells, sensors, displays, and LEDs. The use of transparent metal oxide layers, in particular Indium tin oxide (ITO), is the most common used approach. However, ITO comes with numerous drawbacks such as the relatively rarity of indium and hence high cost, fragility, strong UV absorption and relative high sheet resistance. An exciting alternative TCE is the use of interconnected metallic nanowires, where their sub-wavelength cross-sections makes them transparent to visible light, where especially silver nanowires are a good candidate because of their high conductivity.Here we show a promising cost-effective method called selective-area electrochemical deposition (SAEC) for the fabrication of these metal nanostructures. SAEC is based on a through-the-mask electrochemical deposition method, where the mask is made using substrate conformal imprint lithography. Next to the inherent low fabrication cost of the electrochemical deposition, it has numerous advantages such as bottom-up growth, scalability, operate at ambient conditions, control over nucleation, and yields high purity deposits. While submicron sized features have been already demonstrated by SAEC, obtaining homogeneous void free filling of features below 100 nm using direct plating is a major challenge because of the terminal effect and the poor control of nucleation of the seed layer.In this work, we have explored the SAEC fabrication of large area silver nanowire grids on ITO substrates and on TOPCon solar cells. We show that the nucleation density of the silver nanoparticles is the key parameter for the successful homogenous void-free filling of the trenches. The nucleation density namely determines the coalescence thickness, which sets a minimum thickness for the silver nanowires in order to be connected. We control the nucleation density of the silver nanoparticles by making use of the double pulse method, where a high overpotential nucleation pulse is applied for controlling the nucleation density. After nucleation, we merge the silver nuclei by applying a low overpotential growth pulse.After the successful filling of the trenches, we have compared the optical and electrical performance of the SAEC fabricated silver nanowire grids to those using conventional thermal or e-beam evaporation followed by lift-off. The SAEC-fabricated TCEs show high transmission (>96%) and extreme low resistance (as low as 3 Ω/sq), resulting into a superior figure of merit (FoM). Due to the bottom-up nature of this technique, arbitrary high aspect ratio nanowires can be achieved and therefore the relationship of decreasing transmission with decreasing sheet resistance is broken.Furthermore, we have also incorporated the silver NW grids in TOPCon cells and compared the performance to similar cells based on ITO. This work represents a low-cost and scalable strategy to fabricate sub 100 nm predefined metal structures, enabling the commercial viable fabrication of nanostructure based transparent conductive electrodes for optoelectronic devices.

Synthesis of Single Crystalline Spike Shaped Nano-Rod Structured Cathode for High Performance SIB

The increasing need for energy, the widespread adoption of electric vehicles and renewable energy storage systems, and the search for cost-effective, reliable energy storage options are all factors in the dynamic nature of the global energy landscape and energy storage industry. As more and more people switch to using electric vehicles and other kinds of renewable energy storage, there has been a corresponding increase in demand for LIBs all around the globe. Despite increasing demand, there are geopolitical and supply-chain risks as most LIBs are still manufactured in only a few countries, namely China, Japan, and South Korea. Sodium-ion batteries, also known as SIBs, have recently come to the forefront as a potentially advantageous candidate for the large-scale storage of electric energy due to the potential advantages of widespread availability and low cost of sodium resources. SIB research and development are still at an early stage, and there are few opportunities for their commercialization. SIBs do, however, confront a number of issues that need to be addressed, including as their short cycle life and rate capability, the restricted availability of high-performance materials, and the need for more research and development to maximize their performance and dependability. Nonetheless, tremendous progress has been made recently, and several businesses and research centers across the globe are attempting to enhance SIB technology. The high theoretical specific capacity and quantity of component elements make layered metal oxides suitable cathode materials for SIBs. In order to enhance their electrochemical performance, however, further exploration is required to deal with their drawbacks, such as limited rate capability and voltage fading. As the cathode materials play such a large role in determining the energy density of SIBs, the primary issue in developing high-energy SIBs is discovering cathode materials with plentiful active sites, high reaction potential, unhindered ionic channels, and stable structures. Tailoring the morphology of materials using nanostructure engineering opens up hitherto unimagined possibilities for exploiting the functional features such as enhanced electrode's specific surface area, decreased sodium-ion diffusion distance, and boost in electronic conductivity. This study demonstrates a quaternary 1D layered transition metal oxide-based cathode with a composition of Na0.67Fe0.25Mn0.5Ti0.2V0.05O2 synthesized by a facile sol-gel strategy. From the SEM results, it is seen that 1D spoke like nanorods are evolved with a tiny fraction of 3D hexagonal lattice which is due to the excessive presence of vanadium in the stoichiometry ratio of the composite. Such nanorod framework configuration facilitates large surface area in contact with the electrolyte that is suitable for charge migration and rapid diffusion of sodium ions through short solid-state route. The P2- Na0.67Fe0.25Mn0.5Ti0.2V0.05O2 microstructure, with its high crystallinity and nanorod structure, showed off a high specific capacity and outstanding rate capability which is visible through electrochemical analysis results.

Multielectrode electrochemical cell for in situ structural characterization of amorphous thin-film catalysts using high-energy X-ray scattering

A multielectrode-based electrochemical cell allows the structural characterization of an amorphous thin-film water oxidation catalyst under various electrochemical potentials using high-energy X-ray scattering and atomic pair distribution function (PDF) techniques. A multielectrode with five electrodes provides a sufficiently low background signal to enable high-energy X-ray scattering (HEXS) measurements and amplifies the extremely low HEXS signals from samples for high-resolution PDF analysis of in situ data from thin-film catalysts. Glassy carbon (GC) creates a relatively low intensity HEXS pattern and is used as a working electrode. Instead of a three-dimensional (3D) porous electrode architecture, the flat geometry of the electrode enables various deposition techniques to be used for the preparation of a highly conductive metal oxide layer. PDF analysis demonstrates high spatial resolution for a 230 nm thick amorphous iridium oxide film deposited on two roughened 60 µm thick GC electrodes. The PDF analysis resolves the domain size and distinguishes changes in fine structure which are directly correlated with the structure and function of the catalysts. The results bring the opportunity to analyze the structure of nanometre-scale amorphous thin-film catalysts in an electrolyte-compatible and compact 3D-printed electrochemical cell in a three-electrode configuration.

Gas-Sensing Properties of Graphene Functionalized with Ternary Cu-Mn Oxides for E-Nose Applications

Chemiresistive gas sensors were produced by functionalizing graphene with a ~3 nm layer of mixed oxide xCu2O⸱yMnO using pulsed laser deposition (PLD) from a hopcalite CuMn2O4 target. Sensor response time traces were recorded for strongly oxidizing (NO2, O3) and reducing (NH3, H2S) poisonous gases at ppb and ppm levels, respectively. The morphology of the MOX layer was modified by growth temperature during PLD, resulting in the optimization of the sensor response. Differences in decomposition or oxidation rates on catalytically active metal oxide (MOX) were utilized to achieve partial selectivity for pairs of gases that have similar adsorption and redox properties. The predominant selectivity towards ozone in most samples at different measuring conditions remained difficult to suppress. A distinct selectivity for H2S emerged at higher measurement temperatures (100–150 °C), which was assigned to catalytic oxidation with O2. Several gas–MOX interaction mechanisms were advanced to tentatively explain the sensor behavior, including reversible electron transfer in the simplest case of NO2, decomposition via ionic transients for O3, and complex catalytic oxidative transformations for NH3 and H2S.

Molecular Mechanism of Selective Al2O3 Atomic Layer Deposition on Self-Assembled Monolayers.

Area-selective atomic layer deposition (AS-ALD) of insulating metallic oxide layers could be a useful nanopatterning technique for making increasingly complex semiconductor circuits. Although the alkanethiol self-assembled monolayer (SAM) has been considered promising as an ALD inhibitor, the low inhibition efficiency of the SAM during ALD processes makes its wide application difficult. We investigated the deposition mechanism of Al2O3 on alkanethiol-SAMs using temperature-dependent vibrational sum-frequency-generation spectroscopy. We found that the thermally induced formation of gauche defects in the SAMs is the main causative factor deteriorating the inhibition efficiency. Here, we demonstrate that a discontinuously temperature-controlled ALD technique involving self-healing and dissipation of thermally induced stress on the structure of SAM substantially enhances the SAM's inhibition efficiency and enables us to achieve 60 ALD cycles (6.6 nm). We anticipate that the present experimental results on the ALD mechanism on the SAM surface and the proposed ALD method will provide clues to improve the efficiency of AS-ALD, a promising nanoscale patterning and manufacturing technique.

Porphyrin-Based MOF Thin Film on Transparent Conducting Oxide: Investigation of Growth, Porosity and Photoelectrochemical Properties.

Synthesizing metal-organic frameworks (MOFs) composites with a controlled morphology is an important requirement to access materials of desired patterning and composition. Since the last decade, MOF growth from sacrificial metal oxide layer is increasingly developed as it represents an efficient pathway to functionalize a large number of substrates. In this study, porphyrin-based Al-PMOF thin films were grown on conductive transparent oxide substrates from sacrificial layers of ALD-deposited alumina oxide. The control of the solvent composition and the number of atomic layer deposition (ALD) cycles allow us to tune the crystallinity, morphology and thickness of the produced thin films. Photophysical studies evidence that Al-PMOF thin films present light absorption and emission properties governed by the porphyrinic linker, without any quenching upon increasing the film thickness. Al-PMOF thin films obtained through this methodology present a remarkably high optical quality both in terms of transparency and coverage. The porosity of the samples is demonstrated by ellipsometry and used for Zn(II) insertion inside the MOF thin film. The multifunctional transparent, porous and luminescent thin film grown on fluorine-doped tin oxide (FTO) is used as an electrode capable of photoinduced charge separation upon simulated sunlight irradiation.

High‐Performance Semitransparent Color Organic Photodiodes Enabled by Integrating Fabry–Perot and Solution‐Processed Distributed Bragg Reflectors

AbstractOrganic photodiodes (OPDs) have recently garnered attention as a competitive alternative to their inorganic counterparts, given their inherent advantages in solution processability, mechanical flexibility, and cost‐effective manufacturing. In this work, a novel method for fabricating high‐performance semitransparent color OPDs by integrating Fabry–Perot (FP) interferometer‐based color‐filtering electrodes and solution‐processed distributed Bragg reflectors (sDBRs) is introduced. The FP electrode provides color control by modulating the metal oxide layer thickness, irrespective of the photoactive layer's color. To overcome limitations related to light absorption and device transparency, this work employs a sDBR as a selective window reflector, allowing the OPD to retain its color while preserving semitransparency. The experimental findings demonstrate the successful integration of these components, resulting in semitransparent red, green, and blue (RGB) OPDs exhibiting significantly improved detectivity. The fabricated RGB‐OPDs achieve detectivity values of 4.07, 3.49, and 4.22 × 1010 cm Hz1/2 W−1 for red, green, and blue, respectively. This research highlights the efficacy of FP and sDBR color filters in realizing high‐performance color sensors and offer novel opportunities for semitransparent OPD integration with other optoelectronic devices.

Oxide vacancy passivation through interface engineering of Tetraphenylethylene-Based Small-Molecule with sulfonate functional group for efficient organic photodetector

In this study, an alcohol-soluble tetraphenylethylene (TPE) unit-based luminogen with sulfonate chains is developed as a passivation layer for the oxygen vacancies of zinc oxide (ZnO) to obtain efficient organic photodetectors (OPDs). Given that the TPE-4 is designed to have four sulfonate chains, it can effectively fill the oxygen vacancy in ZnO, as confirmed by the results of X-ray photoelectron spectroscopy. The OPD device with the combination of ZnO and TPE-4 buffer layer exhibited decreased dark current and increased photocurrent owing to the prevention of trap-assisted recombination and shunt leakage caused by oxygen vacancies, as proved by electrical analysis. Moreover, the TPE-4 buffer layer exhibited excellent noise attenuation, leading to a signal-to-noise ratio of 50.35 dB and high device speeds of 0.77 μs and 137 kHz. The proposed TPE-based luminogen, designed to highlight the advantages of the widely used metal oxide layer while compensating for its limitations, is an effective strategy for realizing excellent photodetectors through chemical bonding.

Microscopic Analysis of the Wetting Morphology and Interfacial Bonding Mechanism of Preoxidised Kovar Alloys with Borosilicate Glass

This paper investigates the wettability of Kovar alloys with high-borosilicate glass and microscopically analyses the mechanism of wettability and diffusion between Kovar and borosilicate glass. First, Kovar was oxidised at 800 °C for 5, 15, 25, 35, and 60 min to observe the oxide morphology of the Kovar surface layer and to analyse the composition of the oxide layer. To investigate the wetting pattern formations of Kovar and high-borosilicate glass under different wetting temperatures, times, and preoxidation conditions, Kovar and high-borosilicate glass obtained from different oxidation treatments were held at 1060 °C for 20 min for wetting experiments, and the glass–metal wetting interface morphology and elemental distribution were observed using SEM and EDS. The elemental diffusion at the wetting interface between the borosilicate glass and the Kovar with different preoxidation and at the glass spreading boundary was investigated. The longitudinal diffusion of the liquid glass in the metal oxide layer formed a new tight chemical bond of Fe2SiO4, and the lateral diffusion of the liquid glass in the Kovar surface layer formed a black halo.

Designing water/air-stable Co-free high-entropy oxide cathodes with suppressed irreversible phase transition for sodium-ion batteries

Layered transitional metal oxides are promising cathode materials for sodium-ion batteries that benefit from their high energy densities. Nevertheless, the complicated irreversible phase transitions and poor air stability limit their energy efficiency and implementation in practical devices. Here, a new Co-free high-entropy oxide (HEO) layered cathode NaFe0.2Cu0.1Ni0.2Mn0.3Ti0.2O2 is proposed to enhance the reversible phase transition, improve the air stability, and further decrease the cost. The HEO cathode displays excellent sodium-ion storage performance with a capacity of 121 mAh g−1, competitive cycling stability (∼83.8% capacity retention after 200 cycles at 2 C), and enhanced water resistance (capacity of 105.2 mAh g−1 after soaking in water for 2 h and capacity retention of 83% after 200 cycles at 1 C). Moreover, the as-obtained NFCNMT‖hard carbon full cells exhibit superior performance with reversible specific capacity 115 mAh g−1 and approximately ∼73% capacity retention after 100 cycles at 1C. Ex-situ X-ray diffraction and transmission electron microscopy reveal the completely reversible O3 → P3 → O3 structure evolution and suppressed violent changes in lattice parameters owing to the high-entropy design. Furthermore, the galvanostatic intermittent titration technique and in-situ electrochemical impedance spectroscopy reveal that the HEO cathode exhibits fast Na+ diffusion kinetics. For sodium-ion batteries, this work provides a new strategy for suppressing irreversible phase transformation and enhancing air stability.

Self-Adaptation of Oxygen Adsorption and Sub-Surface Junction Formation in Thin Nanometric Sheets of Metal Oxides

Oxygen adsorption at metal oxide (MOX) surfaces and the formation of sub-surface depletion zones in thin nanometric sheets of MOX materials are theoretically investigated. It is shown that—under conditions of sufficient oxygen mobility—the bulk thermal generation of oxygen vacancy donors and the adsorption of surface oxygen ions cooperate in a self-organizing manner to form narrow sub-surface depletion zones which optimally fit into the limited spaces of MOX layers with nanometric cross sections. With this self-organization process in place, both the oxygen adsorption at free surfaces and the bulk generation of oxygen vacancy donors continuously increases as the MOX sheet thickness L is reduced, maintaining at the same time overall electro-neutrality and a state of perfect volume depletion of free carriers in bulk. This process comes to an end when MOX sheet thicknesses of L ≈ 1 nm are approached and when 3d-volumes of about 1 nm3 contain only one single double-donor and two surface oxygen ions on average. It is argued that at this limit of miniaturization, different interpretations of MOX gas sensing phenomena might be required than on larger length scales.

Corrosion Performance of Ti6Al7Nb Alloy in Simulated Body Fluid for Implant Application Characterized Using Macro- and Microelectrochemical Techniques

In this paper, the applicability of Ti6Al7Nb as a more biocompatible alternative for bone and dental implants than Ti6Al4V and pure titanium in terms of corrosion resistance and electrochemical inertness is investigated. The chemical inertness and corrosion resistance of the Ti6Al7Nb biomaterial were characterized by a multi-scale electrochemical approach during immersion in simulated physiological environments at 37 °C comparing its behavior to that of c.p. Ti, Ti6Al4V, and stainless steel. The establishment of a passive regime for Ti6Al7Nb results from the formation of a thin layer of metal oxide on the surface of the material which prevents the action of aggressive species in the physiological medium from direct reaction with the bulk of the alloy. Conventional electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) provide quantified information on the surface film resistance and its stability domain that encompasses the potential range experienced in the human body; unfortunately, these methods only provide an average estimate of the exposed surface because they lack spatial resolution. Although local physiological environments of the human body are usually simulated using different artificial physiological solutions, and changes in the electrochemical response of a metallic material are observed in each case, similar corrosion resistances have been obtained for Ti6Al7Nb in Hank’s and Ringer’s solutions after one week of immersion (with a corrosion resistance of the order of MΩ cm2). Additionally, scanning electrochemical microscopy (SECM) provides in situ chemical images of reactive metal and passive dielectric surfaces to assess localized corrosion phenomena. In this way, it was observed that Ti6Al7Nb exhibits a high corrosion resistance consistent with a fairly stable passive regime that prevents the electron transfer reactions necessary to sustain the metal dissolution of the bulk biomaterial. Our results support the proposition of this alloy as an efficient alternative to Ti6Al4V for biomaterial applications.

Interface-Engineered Organic Near-Infrared Photodetector for Imaging Applications.

We report a high-speed low dark current near-infrared (NIR) organic photodetector (OPD) on a silicon substrate with amorphous indium gallium zinc oxide (a-IGZO) as the electron transport layer (ETL). In-depth understanding of the origin of dark current is obtained using an elaborate set of characterization techniques, including temperature-dependent current-voltage measurements, current-based deep-level transient spectroscopy (Q-DLTS), and transient photovoltage decay measurements. These characterization results are complemented by energy band structures deduced from ultraviolet photoelectron spectroscopy. The presence of trap states and a strong dependency of activation energy on the applied reverse bias voltage point to a dark current mechanism based on trap-assisted field-enhanced thermal emission (Poole-Frenkel emission). We significantly reduce this emission by introducing a thin interfacial layer between the donor: acceptor blend and the a-IGZO ETL and obtain a dark current as low as 125 pA/cm2 at an applied reverse bias of -1 V. Thanks to the use of high-mobility metal-oxide transport layers, a fast photo response time of 639 ns (rise) and 1497 ns (fall) is achieved, which, to the best of our knowledge, is among the fastest reported for NIR OPDs. Finally, we present an imager integrating the NIR OPD on a complementary metal oxide semiconductor read-out circuit, demonstrating the significance of the improved dark current characteristics in capturing high-quality sample images with this technology.

Cable bacteria regulate sedimentary phosphorus release in freshwater sediments

Previous studies have demonstrated that e-SOx can regulate the sedimentary release of phosphorus (P) in brackish and marine sediments. When e-SOx is active, an iron (Fe) and manganese (Mn) oxide rich layer is formed near the sediment surface, which prevents P release. When e-SOx becomes inactive, the metal oxide layer is reduced via sulfide-mediated dissolution, and P is subsequently released to the water column. Cable bacteria have been shown to also occur in freshwater sediments. In these sediments, sulfide production is limited, and the metal oxide layer would thus dissolve less efficiently, leaving the P trapped at the sediment surface. This lack of an efficient dissolution mechanism implies that e-SOx could play an important role in the regulation of P availability in eutrophied freshwater streams. To test this hypothesis, we incubated sediments from a eutrophic freshwater river to investigate the impact of cable bacteria on sedimentary cycling of Fe, Mn and P. High-resolution depth profiling of pH, O2 and ΣH2S complemented with FISH analysis and high-throughput gene sequencing showed that the development of e-SOx activity was closely linked to the enrichment of cable bacteria in incubated sediments. Cable bacteria activity caused a strong acidification in the suboxic zone, leading to the dissolution of Fe and Mn minerals and consequently a strong release of dissolved Fe2+ and Mn2+ to the porewater. Oxidation of these mobilized ions at the sediment surface led to the formation of a metal oxide layer that trapped dissolved P, as shown by the enrichment of P-bearing metal oxides in the top layer of the sediment and low phosphate in the pore and overlying water. After e-SOx activity declined, the metal oxide layer did not dissolve and P remained trapped at the surface. Overall, our results suggested cable bacteria can play an important role to counteract eutrophication in freshwater systems.

Proton Conducting Organic-Inorganic Composite Membranes for All-Vanadium Redox Flow Battery.

The quest for a cost-effective, chemically-inert, robust and proton conducting membrane for flow batteries is at its paramount. Perfluorinated membranes suffer severe electrolyte diffusion, whereas conductivity and dimensional stability in engineered thermoplastics depend on the degree of functionalization. Herein, we report surface-modified thermally crosslinked polyvinyl alcohol-silica (PVA-SiO2) membranes for the vanadium redox flow battery (VRFB). Hygroscopic, proton-storing metal oxides such as SiO2, ZrO2 and SnO2 were coated on the membranes via the acid-catalyzed sol-gel strategy. The membranes of PVA-SiO2-Si, PVA-SiO2-Zr and PVA-SiO2-Sn demonstrated excellent oxidative stability in 2 M H2SO4 containing 1.5 M VO2+ ions. The metal oxide layer had good influence on conductivity and zeta potential values. The observed trend for conductivity and zeta potential values was PVA-SiO2-Sn > PVA-SiO2-Si > PVA-SiO2-Zr. In VRFB, the membranes showcased higher Coulombic efficiency than Nafion-117 and stable energy efficiencies over 200 cycles at the 100 mA cm-2 current density. The order of average capacity decay per cycle was PVA-SiO2-Zr < PVA-SiO2-Sn < PVA-SiO2-Si < Nafion-117. PVA-SiO2-Sn had the highest power density of 260 mW cm-2, while the self-discharge for PVA-SiO2-Zr was ~3 times higher than Nafion-117. VRFB performance reflects the potential of the facile surface modification technique to design advanced membranes for energy device applications.

Understanding the Influence of Metal Oxide Layer Thickness and Defects on Resistive Switching Behavior Through Numerical Modeling

Understanding the Influence of Metal Oxide Layer Thickness and Defects on Resistive Switching Behavior Through Numerical Modeling

Resistive Switching: Physics, Devices and Applications

Resistive Switching: Physics, Devices and Applications

Interfacial Molecular Compatibility for Programming Organic-Metal Oxide Superlattices.

Artificially programming a sequence of organic-metal oxide multilayers (superlattices) by using atomic layer deposition (ALD) is a fascinating and challenging issue in material chemistry. However, the complex chemical reactions between ALD precursors and organic layer surfaces have limited their applications for various material combinations. Here, we demonstrate the impact of interfacial molecular compatibility on the formation of organic-metal oxide superlattices using ALD. The effects of both organic and inorganic compositions on the metal oxide layer formation processes onto self-assembled monolayers (SAM) were examined by using scanning transmission electron microscopy, in situ quartz crystal microbalance measurements, and Fourier-transformed infrared spectroscopy. These series of experiments reveal that the terminal group of organic SAM molecules must satisfy two conflicting requirements, the first of which is to promptly react with ALD precursors and the second is not to bind strongly to the bottom metal oxide layers to avoid undesired SAM conformations. OH-terminated phosphate aliphatic molecules, which we have synthesized, were identified as one of the best candidates for such a purpose. Molecular compatibility between metal oxide precursors and the -OHs must be properly considered to form superlattices. In addition, it is also important to form densely packed and all-trans-like SAMs to maximize the surface density of reactive -OHs on the SAMs. Based on these design strategies for organic-metal oxide superlattices, we have successfully fabricated various superlattices composed of metal oxides (Al-, Hf-, Mg-, Sn-, Ti-, and Zr oxides) and their multilayered structures.

Chemo-Mechanical Analysis of Lithiation/Delithiation of Ni-rich Single Crystals

Single crystal, Ni-rich layered lithium metal oxides are promising candidates for next-generation cathodes in lithium-ion batteries. However, these Ni-rich materials display anisotropic swelling and contraction during cycling, and this may lead to the generation of internal stresses and thereby to fracture and capacity loss. In this work, the spatio-temporal evolution of lithium concentration and stress state within a (NMC811) single crystal are predicted using a fully coupled chemo-mechanical model. The stress state in the crystal arises from a spatially non-uniform distribution of Li concentration, and from a non-linear dependence of intercalation strain upon lithium concentration. The peak tensile stress is greatest near top-of-charge, due to the high sensitivity of intercalation strain upon lithium occupancy at low concentrations, and the peak tensile stress increases with both cycling rate and particle dimension. Significantly, the predicted peak tensile stress is insufficient to cause basal plane fracture of single crystals when their diameter is below 2.5 μm and the charging and discharging rates are below 5C. This suggests that intraparticle fracture is not a significant degradation mode for well-designed NMC811 single crystals.

Performance investigation of low-power flexible n-ZnO/p-CuO/n-ZnO heterojunction bipolar transistor: Simulation study

Oxide semiconductor-based heterojunction bipolar transistors are widely applicable in flexible, printable, and cost-effective circuit applications. Among earth-abundant metal oxides, zinc oxide and copper oxide inherently show n-type and p-type characteristics, respectively, and their electronic properties can be easily modified during the fabrication process. Accordingly, a planar-type HBT can be achieved by low-temperature growth of the metal-oxide layers on a flexible substrate without the need for further sophisticated processes. In this paper, a double heterojunction bipolar transistor (DHBT) comprised of ZnO layers serving as the emitter and collector regions, along with the CuO layer functioning as the base area is presented. Simulation results demonstrate that the proposed all-metal oxide transistor based on p-CuO/n-ZnO heterojunction enjoys low power consumption owing to the low threshold voltage. High-frequency characterization and DC analysis of the proposed NPN configuration are carried out using the ATLAS/SILVACO package. Our findings reveal that at the base-emitter voltage of 0.55 V, the current gain factor of the device reaches 155, which is larger than those reported in the literature. Furthermore, an ideality factor at the base-emitter voltage of 0.7 V was obtained for the collector-base and emitter-base junctions equal to 1.5 and 1.2, respectively.