Electronic Materials Letters最新文献

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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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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