Electronic Materials Letters最新文献

In this article, we have investigated the electronic structure and magnetic properties of Sm₂MgMnO₆ prepared through auto-combustion method. The first principles of the density-functional theory have been applied to study of the electronic structure. The oxidation states of Mn and Mg are Mn³⁺/Mn⁴⁺ and Mg²⁺, respectively. The existence of Mn³⁺ is higher than Mn⁴⁺. The magnetic study reveals the sample shows ferromagnetic to paramagnetic transition at around 13.5 K which is followed by an antiferromagnetic ordering at 8.3 K. Antiferromagnetic and ferromagnetic ordering have been identified at 8.3 K and higher temperature, respectively. Sm₂MgMnO₆ shows a maximum magnetic entropy change of 1.25 J kg^-1K^-1 and relative cooling power of 86.9 J/kg for a field variation of 70 kOe near 25 K. The values are comparable to many double perovskites reported previously. This study highlights that Sm₂MgMnO₆ is a potential material for magnetocaloric refrigerant at low temperature.

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The asymmetrical gate-drain bias stress (GDBS) stability of a mesa-shaped vertical-channel thin-film transistors (VTFTs) was investigated using an In-Ga-Zn–O (IGZO) active layer prepared by atomic-layer deposition. The GDBS measurements were conducted with variations in electrode configurations and overlapped areas between the active and bottom electrode regions. The GDBS stability of the IGZO VTFTs was found to be significantly degraded, when a plasma-damaged electrode was used as the drain electrode, due to the formation of defective channel regions that are more susceptible to the hot carrier effect. To address the effect of plasma-damaged electrode, an ultrathin passivation layer was introduced, resulting in the achievement of VTFTs with excellent and uniform GDBS stability.

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Two-dimensional (2D) transition metal dichalcogenides (TMDs) are excellent candidates for electronic applications because of their high carrier mobility, tunable bandgap energy depending on the number of layers, monolayer thickness, and the absence of dangling bonds on their surfaces. Despite these advantages, the crystalline structures of TMDs contain intrinsic defects such as vacancies, adatoms, grain boundaries, and substitutional impurities, which can cause large contact resistance at the source/drain interface. Customized engineering of interfaces and defects, which provides a method to modulate the properties of TMDs, is crucial as it can significantly enhance device performance. Herein, we explored a novel electrode to enhance the interface between electrode and semiconductor materials. we report the synthesis of high-quality atomically thin MoO₂ using atmospheric pressure chemical vapor deposition (APCVD) and its application to field-effect transistors. To improve crystallinity of MoO₂, we investigated the influence of hydrogen concentration, a key parameter in the reduction process, on the synthesis of high-crystallinity MoO₂. By adding NaCl to MoO₃ powder, we optimized the synthesis of high-crystallinity MoO₂. Utilizing the optimized MoO₂, we fabricated transistors that exhibited a mobility of 29.1 cm²/V∙s and an on/off ratio of 1.78 × 10⁴, demonstrating excellent performance. Our findings confirm that single-crystal MoO₂ can be effectively applied as a contact electrode in high-performance two-dimensional semiconductor devices.

The incorporation of semi-crystalline polymers as additives with small-molecule organic semiconductors has emerged as a pioneering method for the alteration of crystallization processes, thin film morphologies, and charge carrier mobility within organic semiconductor matrices. In this paper, we utilize the intrinsic attributes of polyethylene oxide (PEO), acting as a semi-crystalline polymer additive, to modulate the crystallization, phase segregation and charge transport of 6,13-bis (triisopropylsilyl) pentacene (TIPS pentacene). To understand the synergistic effects between varying molecular weights (8, 100, 300 and 900 K) of PEO and the crystallization behavior of TIPS pentacene, we conducted a quantitative analysis of the films' relative crystallinity and crystallographic morphology employing X-ray diffraction (XRD) and optical microscopy. Our findings indicate that higher molecular weight PEOs (300K and 900K) exhibit reduced molecular chain activity, resulting in lower crystallinity at increased doping ratios. Furthermore, attributes such as a high dielectric constant and a substantial melting point, combined with favorable thermoplastic properties, predispose these films to a more susceptible phase separation within the crystalline matrix. Conversely, films with lower molecular weight PEOs (8 and 100 K) showed lesser impact from molecular chain dynamics, leading to enhanced crystal morphology, higher crystallinity, and improved charge carrier mobility by up to 11 times. This substantial enhancement underscores the potential of employing low molecular weight semi-crystalline polymers as additive agents in the development of advanced organic semiconductor devices.

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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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