Journal of Materials Science: Materials in Electronics最新文献

The fabrication of uniform metal bump arrays with submicron-sized diameters is crucial for achieving Micro-LED displays with ultra-high pixel density. This study presents a fabrication strategy that utilizes an undercut sacrificial layer in the lift-off process to achieve fine-pitched metal bump arrays. The influences of sacrificial layer thickness and developing time on the undercut degree, as well as their effects on the morphology and dimensional consistency of bumps, are investigated. It is observed that increasing the developing time leads to a higher degree of undercut, not only facilitating the lift-off of the sacrificial layer but also resulting in an increased base radius of the metal bumps. By optimizing process parameters, we successfully achieved Au bump arrays with a base radius around 0.99 μm, top radius around 0.3 μm, and a pitch size of 1.4 μm, exhibiting height nonuniformity below 5%. This fabrication strategy for uniform metal bump arrays with ultra-high density will greatly contribute to advancing Micro-LED technology towards high definition and high brightness.

The global negative temperature coefficient (NTC) thermistor market produces over four billion units annually, with applications spanning industrial manufacturing, aerospace, and household appliances. With the increasing adoption of new energy vehicles and energy storage systems, the demand for reliable temperature control in battery systems has grown significantly. NTC thermistors, renowned for their precision, miniaturization, and rapid response, play a crucial role in maintaining optimal battery temperatures, which contributes to prolonged battery life and enhanced system reliability. Over the past two centuries, various materials have been used to develop NTC thermistors. However, early NTC thermistors often suffered from issues such as a narrow temperature measurement range and poor stability. Therefore, it is necessary to review the effects of different materials, dopants, and manufacturing processes on the electrical properties of NTC thermistors to promote further research and applications. This paper provides a comprehensive review of the characteristics, development history, performance index, and temperature-sensing mechanisms of NTC thermistors. Additionally, it summarizes the current research status and future directions for various types of NTC thermistors.

The PVA/CeO₂ nanocomposite was prepared via the solution casting method. This work highlights the novelty of PVA/CeO₂ nanocomposites in advancing environmentally friendly and high-performance energy storage technologies. The supercapacitor with specific capacitance modified from 3 F/g to 56 F/g is applicable for moderate energy storage devices in day-to-day life. Along with this, we investigated the physio-thermal properties of the same and concluded that its efficacy is proportionate to the dopant inclusion in the matrix PVA.

Transparent pale yellow crystals of 2-methylquinolinium picrate (2MQPA) were synthesized from picric acid and 2-methylquinoline using methanol as a solvent. The salt formation occurred through hydrogen bonding between the phenolate group of picric acid and the tertiary nitrogen of 2-methylquinoline. Optical characteristics, including transmittance and photoluminescence, were examined using UV–Vis spectroscopy. Functional groups were identified through Fourier Transform Infrared (FTIR) spectroscopy, while thermal stability and decomposition behavior were analyzed via thermogravimetric-differential thermal analysis (TG–DTA) and differential scanning calorimetry (DSC). The third-order nonlinear optical (NLO) response was investigated using the Z-scan technique. Hirshfeld surface analysis highlighted significant intermolecular interactions, including H–H, C–H, O–H, and N–O contacts. Computational studies optimized the crystal structure, and density functional theory (DFT) calculations confirmed intermolecular charge transfer interactions and N–H⋯O hydrogen bonding, offering detailed insights into the electronic properties of 2MQPA.

Flower-like nickel manganese layered double hydroxide coupled with carbon nanotube arrays in-situ grown on a nickel mesh (NiMn-LDH/CNTs@Ni) has been prepared by a facile hydrothermal method. By increasing the Mn/Ni ratio, the thickness of the LDH nanosheets increased while the spherical structure built up from the interconnected LDH nanosheets degraded. The optimized NiMn-LDH/CNTs@Ni exhibits a three-dimensional flower-like structure with the CNT arrays in-situ grown on nickel mesh by chemical vapor deposition method acting as stems to connect the NiMn-LDH nanoflowers. The prepared NiMn-LDH/CNTs@Ni exhibit high specific capacitance of 1367 F g⁻¹ at 1 A g⁻¹, capacitance retention of 76% at 10 A g⁻¹ and excellent cycling performance in 3 M KOH aqueous solution. First-principles calculations show that Mn doping improves the electron transport and charge transfer capabilities by narrowing the energy gap and increasing the density of states near the Fermi level, which is conducive to enhancing the charge storage capacity. Asymmetric supercapacitors fabricated with NiMn-LDH/CNTs@Ni and nitrogen-doped carbon nanotubes exhibited energy densities as high as 31.8 W h kg⁻¹ at a power density of 800 W kg⁻¹, demonstrating the potential of the fabricated binder-free electrodes for practical applications. This study demonstrates that modulating the electronic structure and nanostructure by doping hetero metal atoms can effectively improve the charge storage capacity of LDHs.

Multiferroic composites with high magnetic and electric properties at room temperature are considered the most significant materials due to their potential applications in many electronic devices. Furthermore, ultrafast, eco-friendly, energy-efficient innovative techniques to develop multifunctional materials have attracted abundant importance. In this study, we report on ferromagnetic particulate alloy prepared via a clean, eco-friendly, ultrafast, wet ball milling method followed by annealing at different temperatures. The multiferroic properties of the annealed samples were investigated via different characterizations. X-ray diffraction confirmed the identification of face-centered cubic with L2₁ arrangement. The calculated average crystallite size of prepared Mn₂TiSn (900 °C/20 h.) Heusler alloy nanoparticles using Scherer’s formula were found to be 37 nm. A high-resolution electron microscope reveals the aggregated morphology with a particle size ranging from 80 to 120 nm. The temperature-dependent electrical resistivity and Seebeck coefficient were measured, suggesting that the alloy behaves like an n-type semiconductor. Such semiconducting behavior may be considered as an indication that Mn₂TiSn full-Heusler alloy is a spin-gapless semiconductor. Vibrating sample magnetometer measurements suggest that the alloy has soft ferromagnetic properties with low coercivity and high saturation. This result may offer an alternative technique for preparing alloys with improved magnetic and electrical properties. Thus, this work suggests that the material is feasible for spintronic applications.

Triboelectric nanogenerators (TENG) as gas sensor is a strategy for detection that does not require power source. This study prepared Ag/Bi₂WO₆ composite as a triboelectric layer in a TENG device. Incorporating Ag particles improved output performance. Additionally, self-powered gas sensor (SPGS) based on 2% Ag/Bi₂WO₆ exhibited a response of 27.6% to 100 ppm ethanol with response/recovery times (72.7/81 s). SPGS also have a lower limit of detection (LOD) as 2.7 ppm. The enhanced gas-sensitive performance to the catalytic effect of Ag, which facilitated the adsorption and desorption of ethanol gas molecules. This work demonstrating the potential application of multi-element metal oxides in ethanol detection was demonstrated.

In this work, acidified and helical carbon nanotubes were prepared by magnetron sputtering, and their electromagnetic parameters and absorption properties were analyzed. Their mechanism of electromagnetic wave-absorbing attenuation was investigated through the finite element method. The acidification and spiralization treatments reduced the diameter of the carbon nanotubes, introduced a large number of internal defects and oxygen-containing functional groups, reduced the effective conductivity, increased the penetration depth, promoted the dielectric polarization relaxation, and made the dielectric parameters more suitable for electromagnetic wave absorption, resulting in an improvement in the impedance matching characteristics and electromagnetic wave absorption performance. The finite element calculations indicated that carbon nanotubes with a helical structure exhibited a more uniform distribution of the scattering electromagnetic field and a smaller intensity. As the small ratio of length to diameter decreased, the intensity of the scattering field gradually decreased and their distribution became more uniform. Furthermore, the acidified helical carbon nanotubes exhibited excellent absorption properties with a maximum absorption bandwidth of 5.60 GHz at a matching thickness of 1.53 mm, and a minimum reflection loss of − 32.14 dB at 12.60 GHz at a matching thickness of 1.79 mm. Therefore, acidified helical carbon nanotubes showed great potential in the application of microwave absorption.

The fabrication of HfO₂-based ferroelectric films typically relies on high-temperature rapid annealing to induce ferroelectricity. The excellent ferroelectric properties of HfO₂-based films obtained by low-temperature treatment have always attracted widespread attention. Here, we deposited Ti-doped HfO₂ thin films with different concentrations on n-type highly doped Si wafers by magnetron sputtering and reported the electrical properties of Ti-doped HfO₂ films after treatment at different temperatures. Hysteresis loop measurements and piezoresponse force microscopy (PFM) confirmed that films subjected to low-temperature treatment (400 °C) exhibited strong ferroelectric behavior. X-ray photoelectron spectroscopy (XPS) analysis revealed that Ti doping effectively optimized the distribution of oxygen vacancies in the HfO₂ films. Additionally, undoped HfO₂ or Al₂O₃ was employed as a capping layer for a 20 nm thick Ti-doped HfO₂ film (Hf_0.9Ti_0.1O₂). After rapid annealing in an N₂ environment at 400 °C, a significant enhancement in the film's ferroelectric properties was observed. The development of HfO₂-based films with excellent ferroelectric performance through low-temperature processing is of great importance for enhancing the compatibility of HfO₂ films with CMOS fabrication processes.