Journal of the Korean Physical Society最新文献

Amorphous metal–oxide–semiconductor (MOS)-based thin-film transistors (TFTs) are gaining attention because of their favorable electrical performance and better operational stability than conventional amorphous silicon semiconductors. This study investigates the impact of the annealing temperature and multilayered structures on the performance and stability of indium–tin–zinc-oxide (ITZO) TFTs. ITZO semiconductors are fabricated under annealing temperatures of 350, 400, and 450 °C to improve the quality of metal–oxide–metal (M–O–M) bonding networks and reduce defect states. Single-, bi-, and tri-layer film configurations are used to optimize the device’s performance and stability. TFTs fabricated at 400 °C with a bi-layer coating show superior device performance and operational stability owing to superior M–O–M bonding networks and reduced charge-trapping characteristics compared to other cases. These results emphasize the importance of annealing temperature and layer thickness in achieving a high mobility, low threshold voltage, and device stability for next-generation display technologies.

This study investigates the impact of thermal radiation on the shear flow of two immiscible water-based hybrid nanofluids containing carbon nanotubes, confined within converging boundary layers of unequal strengths. The analysis focuses on comparing two widely used thermal conductivity models, namely, the Yamada–Ota and Xue models for hybrid nanofluids composed of single-walled (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). By applying appropriate similarity transformations, the governing partial differential equations are reduced to a set of nonlinear ordinary differential equations, which are solved numerically using MATLAB's bvp4c solver. The effects of key parameters, including viscosity ratio, thermal conductivity ratio, radiation, and Schmidt number on velocity, temperature, and concentration fields, are examined in detail. Results demonstrate that the Xue model predicts a steeper temperature gradient compared to the Yamada–Ota model, and that increasing the Schmidt number reduces mass transfer in both fluid layers. The comparative analysis provides valuable insights for optimizing thermal and mass transport in stratified flow systems, with potential applications in microchannel heat exchangers, layered cooling devices, and energy systems.

As the features of metal oxide semiconductor field-effect transistor (MOSFET) devices are aggressively scaled down, 3-dimensional (3D) integration is receiving significant attention for further semiconductor technology development. While hybrid bonding is a promising solution for 3D integration because it can achieve high interconnect density, thermal management of bonded dies would be a potential problem. The thermal conductivity of the interlayer dielectric is crucial for effective thermal management. With high thermal conductivity and low fabrication temperature, magnesium oxide (MgO) is one of the attractive dielectric interlayers. However, due to the high dielectric constant, crosstalk degradation is a major challenge for MgO implementation. This study proposes various strategies for MgO implementation. 2-dimensional technology, computer-aided-design, and transient thermal simulation have been utilized to investigate MgO performance as an interlayer dielectric. At the same time, the finite element method has been used to study the tradeoff with crosstalk performance. The simulated results reveal that the device operating temperature can be reduced to 7 °C by applying a MgO layer in SiO₂ intermetal dielectric, with a thickness ratio ranging from 20 to 40%. MgO single-layer implementation as a heat-conducting channel has also been studied. M4, M5, or M6 are recommended for high thermal conductivity and low crosstalk tradeoff. This study demonstrates that an optimized usage of MgO layer in the back-end-of-line can minimize crosstalk degradation while maintaining heat dissipation enhancement. These results suggest that MgO interlayer can be an attractive solution to the local heating issue in high-performance applications.

The Foucault pendulum is a highly educational experiment that provides a visible demonstration of Earth’s rotation—something difficult to perceive in everyday life. However, unlike the specially crafted Foucault pendulums exhibited in science museums, it is not easy for students to observe the precession caused by Earth’s rotation employing a simply constructed spherical pendulum made by themselves. Here, we theoretically explained that it was challenging because the precession of the spherical pendulum erased the precession caused by Earth’s rotation. We also supported this explanation by actual experimental data from our own simple pendulum. Moreover, based on this empirical and theoretical understanding, we focused on minimizing the initial angular velocity, the primary factor that makes it difficult to observe the Foucault pendulum’s precession, and successfully demonstrated Earth’s rotation. We hope that our investigation would help students carry out their own Foucault pendulum experiments and probe Earth’s rotation for themselves in a typical school setting without requiring any specialized equipment.

The Janis-Newman-Winicour (JNW) spacetime possesses a naked singularity, although it represents an exact particle-like solution to the Einstein-Klein-Gordon theory with a massless scalar field. Here, we investigate the possible formation of a naked singularity in the JNW spacetime, using the thin-shell approximation to describe the gravitational collapse. By introducing different matter contents to construct thin-shells, we demonstrate the impossibility of naked singularity formation during the gravitational collapse unless the causality or null energy condition of the thin-shell is violated. Therefore, forming a visible naked singularity is impossible, and the weak cosmic censorship is satisfied.

Neurons in the human brain exchange signals with each other through synapses, synapses transmit neurons’ information and represent various associations. In this study, the devices using quantum dots (QDs) were fabricated and presented as a synaptic mimic device. A programming/erasing process was performed to insert or remove electrons from the quantum dots by applying a gate voltage to the electrode of the device having a stack structure of Pt/Cr/Al₂O₃/QDs/Al₂O₃/SiO₂/Si. To use as a synaptic mimetic devices, analog characteristics that can express various levels of connection strength, repeatability, reproducibility, and retention are required. Therefore, the number of electrons stored in the quantum dots was adjusted by changing the applied voltage and time, and the synaptic characteristics of the device in various stages were confirmed. The state of the device was expressed through the flatband voltage shift by measuring the capacitance–voltage characteristic curves. In addition, it was observed that the device continued to operate when programming/erasing was repeated, and it was confirmed that the device’s state was maintained over time.

A rigorous theoretical investigation has been made on the propagation of nonlinear gravito-nucleus acoustic waves (shock waves) in a magnetized degenerate quantum plasma, whose constituents are noninertial degenerate electrons and inertial nondegenerate heavy nuclei. To study the nonlinear propagation of these shock waves in the plasma system under consideration, the well-known reductive perturbation technique is used. The Burgers equation is derived and the associated shock structure solution is obtained to analyze the shock profile numerically. The dissipative force is responsible for the formation of the gravito-nucleus acoustic waves (GNAWs). The basic properties (amplitude, width, steepness, etc.) of these GNAWs have also been studied, which are significantly modified by the variation of kinematic viscosity, obliqueness, and number density of the plasma species. The results obtained from our present investigation can be applied to astrophysical compact objects like white dwarfs and neutron stars.

Amorphous Ga₂O₃ thin films were deposited on c-plane sapphire substrates by RF magnetron sputtering under varying oxygen partial pressures and crystallized into the monoclinic β-phase via post-annealing at 1000 °C in an oxygen atmosphere. Atomic force microscopy revealed that films grown under low oxygen conditions exhibited surface cracks, while those deposited at higher oxygen pressures showed smooth, crack-free surfaces. Raman spectroscopy showed a progressive increase in the intensities of Ga–O vibrational modes around 200 and 415 cm⁻¹ with increasing oxygen partial pressure, indicating enhanced structural ordering. Optical transmittance measurements revealed a non-linear change in bandgap energy from 4.8 to 4.95 eV, likely due to variations in defect concentration and stoichiometry. The refractive index remained nearly constant at ~ 1.76, suggesting low film density or structural inhomogeneity. These results suggest that β-Ga₂O₃ thin films fabricated under different oxygen partial pressures may still exhibit variations in microstructure and optical properties even after post-annealing.