Electronic Materials Letters最新文献

Physical observation of electrochemical metallization (ECM) channel is required for understanding the electrical characteristics of ECM memristors. Although numerous studies have explored to identify the ECM channels, the majority of approaches have been limited to in-situ systems and localized areas, lacking a comprehensive demonstration of their findings. This study focuses on interpreting the different electrical characteristics of ECM memristors through identification of ECM channels using a new method inspired by etch pit detection on Si surface for determining copper contamination. Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) were utilized to detect and analyze conductive channels within the switching medium after real operation. Interestingly, devices with insulating amorphous carbon (a-C) as medium layer exhibited multiple channels, while devices with semiconducting a-C layers showed a single channel in the on-state. Furthermore, devices with a single channel demonstrated more uniform switching parameters, including high resistance state and set voltage, compared to devices with multiple channels. However, devices with multiple channels exhibited better retention properties .In addition, intermetallic conductive channels were confirmed, resulting from the mixing of Cu active metal ions with the Pt bottom electrode in high current density conditions. The findings of this work provide valuable insights into interpreting ECM memristor performance based on the formation of channels and inspire device design strategies for improving device performance.

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Efficient heat energy management during operation remains a critical challenge in Phase Change Memory (PCM) devices. Reducing the thermal conductivity of electrodes has emerged as a promising strategy to address this issue. Amorphous carbon (a-C) thin films present an attractive option for PCM electrodes due to their intrinsically low thermal conductivity and tunable electrical properties. This study focuses on the development of a-C thin films with optimized electrical and thermal characteristics by controlling the sputtering pressure and conducting post-annealing treatments. Various analytical techniques, including X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and Raman spectroscopy, were employed to investigate the microstructure and composition of the a-C thin films. The results demonstrate that the optimal condition for achieving improved electrical and thermal properties is at the lowest sputtering pressure (2.5 mTorr), which is attributed to the reduced impurity content (specifically oxygen and hydrogen) and denser film structure. Furthermore, post-annealing treatment at 400 °C for 30 min resulted in further improvements in thermal and electrical properties due to the formation of sp² clusters and the reduction of impurities within the film. Consequently, the post-annealed a-C thin film exhibited an outstanding low thermal conductivity of 1.34 W m⁻¹ K⁻¹ and an adequate electrical resistivity of 0.02 Ω cm. The findings of this work provide valuable insights into the underlying mechanisms governing the electrical and thermal properties of a-C thin films, paving the way for the development of energy-efficient PCM devices.

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We report the effect of deposition temperature, spanning from 30 °C to 200 °C, on the electrical properties of solid-phase crystallized Ge thin films on SiO₂/Si substrates. Our findings revealed three distinct ranges of deposition temperature, each exhibiting unique electrical properties. The initial thin films were amorphous with low density in the first range (below 100 °C), amorphous with high density in the second range (between 100 °C and 160 °C), and crystalline with high density in the third range (above 160 °C). In the first and second ranges, an increase in deposition temperature led to a fivefold increase in Hall mobility. This was attributed to the enlarged grain size and reduced energy barrier at grain boundaries possibly owing to the reduced concentration of oxygen impurities. Grain boundary scattering dominated carrier transport in the first range, while diminished energy barrier in the second range effectively mitigated grain boundary scattering. In the third range, an increase in deposition temperature resulted in a decrease in the Hall mobility. This may be linked to the reduced grain size. These results demonstrate the profound impact of deposition temperature on tailoring the electrical properties of polycrystalline Ge thin films, with potential implications for semiconductor processing.

Smart windows are significant for their energy-saving function and visual comfort in our daily lives. This review focuses on the latest advancements in reversible metal electrodeposition (RME) smart window technology, examining related issues primarily in terms of long-term operation, high-contrast, and color neutrality in the privacy state. The electrolyte condition is crucial as it significantly impacts factors like nucleation and growth, Faradaic efficiency of optical cycling, bistability, color neutrality, and repeatability. Overcoming these bottlenecks requires designing an appropriate combination of metal ions and additives in the electrolyte. Although aqueous electrolytes have been predominantly used due to their cost-effectiveness, their narrow electrochemical window has raised concerns for real applications. This limitation would lead to the generation of hydrogen or oxygen gases, potentially damaging smart windows. Recent developments have considered non-aqueous electrolytes as a solution, offering a wider electrochemical window, broader operational temperature ranges, and long-term electrolyte stability. These could be key to overcoming the current challenges in smart windows. This review summarizes recent developments in RME smart windows, addressing their current characteristics, improvements, and limitations to provide insights into future pathways for reversible metal electrodeposition-based smart window development.

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Efficient spatial separation of photocarriers is crucial for photocatalyst to achieve superior solar-driven photocatalytic H₂ production via water splitting. In this study, 3D cubic NiO hollow microspheres (HMs) was served as a free-standing supporting matrix for the co-deposition of ultrathin amorphous carbon layer and wurtzite CdS nanoparticles (NPs) to obtain the highly efficient photocatalysis system for H₂ production. The crystal structure, chemical composition, and optical and electric properties of the ternary C@CdS/NiO composite were characterized by various techniques. The results demonstrated that integrated C@CdS/NiO heteroarchitectures with flower-like morphology and double interfacial combinations are successfully constructed through a one-pot microwave heating process. Under simulated solar illumination, the photocatalytic H₂ evolution reaction (HER) efficiency of as-resulting C@CdS/NiO composite reached a remarkable 17.99 mmol∙g^− 1∙h^− 1, which was 5.7 and 163.5 times higher than that of binary CdS/NiO hybrid and single CdS, respectively. The photo-electrochemical measurements disclosed that the double interfacial interactions are beneficial for promoting the photoexcited charge carriers separation in space. Specifically, the ultrathin carbon film played multiple roles for achievement of exceptional photocatalytic activity as follows: (i) having increase of the active sites, (ii) promoting light absorption capacity, (iii) accelerating separation and transport of the photocarriers, and (iv) protecting CdS against photocorrosion. This study provides a facial synergistic modification strategy for the construction of noble-metal-free photocatalysts for efficient solar-to-fuel conversion.

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Incorporation of chromium (Cr) nanoparticle onto LaFeO₃ (LFO) photocathode to improve optical and photocatalytic activities have been successfully demonstrated. The plain LFO photocathode was prepared by spin-spray gun deposition, following the Cr-incorporated nanoparticle onto the photocathode by spin coating method. It is observed that the photocathode with the optimal composition of 1.5 mmol Cr nanoparticle enhanced the crystal growth of orthorhombic crystal structure predominantly on (121) orientation with the formation of well-connected crystal grain architecture. The structure demonstrated strong optical absorption and a high current density of -60.52 µA cm^− 2 at -0.5 V (vs. Ag/AgCl) more than twice to the untreated LFO film which recorded a maximum photocurrent of -21.83 µA cm^− 2 at -0.5 V (vs. Ag/AgCl). This subsequently led to suppressed surface recombination, lower charge resistance and good stability in the strong alkaline electrolyte. The enhancement provided that incorporating a transition metal element with plain LFO would be applicable for producing efficient photosensitive devices, particularly for photoelectrochemical (PEC) water splitting applications.

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Graphene, a promising carbon nanomaterial, has garnered significant attention owing to its chemical stability, exceptional mechanical properties, and remarkable electrical conductivity and is being used in various electrical engineering applications ranging from solar cells to touch screens. The inherent mechanical strength and electric charge capacity of graphene enable efficient designs of diaphragms used in electrostatic loudspeakers, specifically within the high-frequency domain. This study incorporated single-layer and multi-layer graphene sheets, synthesized via chemical vapor deposition, as electrically charged diaphragms in electrostatic loudspeakers paired with an indium tin oxide film electrode to produce Coulomb force. Subsequently, the sound pressure levels of these distinct graphene- based electrostatic loudspeakers were determined through frequency response measurements. Based on our findings, we propose an optimal graphene film configuration for future electrostatic loudspeaker applications.

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Increasing energy requirement and over energy consumption and further upgrading of energy transfer and storage mechanisms are the critical problem. The supercapacitor is a good candidate for applications requiring high power delivery or uptake. Metal oxides can be effective electrode materials for energy storage devices due to their multiple oxidation states, high theoretical specific capacitance, wide potential window and eco-friendliness. In this connection, here report that electrodes made of notable nanosized transition metal oxides such as Ruthenium oxide (RuO₂), Nickel oxide (NiO) and Cobalt oxide (Co₃O₄) were prepared by simple hydrothermal route and the prepared samples were confirmed through structural, vibrational, morphological, and elemental composition analysis. The modified working electrodes were then examined for electrochemical behavior, including CV, GCD, and EIS studies, using a 1 M KOH electrolyte solution after successive coating of the working material on empty Ni foil. Among them, RuO₂ has high integral area, a low sweep rate and remarkable specific capacitance value of 447.1 Fg^-1 at 5 mVs^-1 in CV analysis. In addition, the GCD curve has good charge-discharge cyclic stability with a maximum specific capacitance of 412.1 Fg^-1 at 0.5 Ag^-1 compared to NiO and Co₃O₄. RuO₂ has long charge-discharge stability and only 6.8% loss in capacitive retention compared to the other systems, NiO (11.2%) and Co₃O₄ (9.3%), even after 10,000 cycles. We except that use of nanosized metal oxide electrodes to enhance electrochemical activity will lead to further improvement in the supercapacitors.

The development of efficient and durable catalysts for the hydrogen evolution reaction (HER) is essential for sustainable energy research. Cobalt sulfides (CoS_x) have attracted significant interest as prospective catalysts for the HER owing to their promising catalytic activity and high stability. In this study, CoS_x nanocrystals embedded in nitrogen-doped carbon frameworks (NC) are fabricated using a zeolite imidazole framework precursor via a two-step pyrolysis-sulfurization process, followed by combination with carbon black (CB) to create CoS_x-NC/CB as an efficient electrocatalyst for the HER. Interestingly, this catalyst displays a higher HER activity than that of the investigated materials, with an overpotential of 282 mV at a current density of 10 mA cm^− 2, along with a Tafel slope of 57.6 mV dec^− 1 in an acidic solution. This performance is attributed to the synergistic effect of CoS_x nanoparticles, nitrogen-doped carbon, and highly conductive CB, which improves the number of active sites, electron transfer, and electrochemical surface area. This outcome has significant potential for the development of economically viable catalysts for water splitting.

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Currently, transition metal tungstates are emerging as electroactive materials for supercapacitors due to their excellent electrical conductivity and electrochemical properties. Small amounts of transition metal ions doping can affect the physical and electrical properties of transition metal tungstates. In this study, Co ion-doped NiWO₄ amorphous composites (CNWO) were synthesized using a simple and effective hydrothermal method and utilized as the cathode material for supercapacitors. The structure and electrochemical properties of NiWO₄ and CNWO composites were investigated using various testing techniques. Specifically, when the cobalt ion doping amount is 10%, the corresponding CNWO-10 electrode material exhibits a specific capacitance of 804 F g⁻¹ at 1 A g⁻¹, and at a current density of 10 A g⁻¹, the capacitance retention rate reaches 66.7%, demonstrating good rate performance. Additionally, an asymmetric supercapacitor device was constructed using CNWO-10 and activated carbon (AC) as positive and negative materials, respectively. Which could cycle reversibly under a potential window of 2.1 V. The device demonstrates a maximum specific capacitance of 76.5 F g⁻¹ at 0.5 A g⁻¹, and a high energy density of 47 Wh kg⁻¹ at a power density of 527 W kg⁻¹. Furthermore, 96% capacitance cycling stability is maintained after 5500 cycles at a trapezoidal current density. Moreover, the electrical conductivities of NiWO₄ and CNWO-10 samples are 9.01 × 10^–8 S m⁻¹ and 8.93 × 10^–6 S m⁻¹, attributed to the Co ion-doping that can reduce the gap width of the forbidden band to enhance conductivity. These results suggest that CNWO composites can serve as promising high-capacity electrode materials for high-performance supercapacitors in alkaline electrolytes.

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