Journal of the Korean Physical Society最新文献

In this paper, the electric field is calculated using the polarization charge induced in the tilted dielectric interface. In general, polarization charges occur at the dielectric interface when an electric field generates owing to the application of a voltage, and they come out due to the discontinuity of the dielectric constant at the dielectric media. When dielectric materials with different dielectric constants come into contact, the magnitude of the polarization charge is determined by the electric field component perpendicular to the dielectric interface. Therefore, in this paper, when calculating the electric field, the electric field at the dielectric interface is obtained using the polarization charge induced at the dielectric interface different from the obtained through the approximation or the recursive equation in most existing studies, and this is verified using a commercial numerical analysis program.

We present systematic methods for compensating gate crosstalk effects in gate-defined quantum dots (QDs), to allow the observation of Coulomb blockade peaks from the few-electron regime (N = 1) to N ≈ 20. Gate crosstalk, where adjustments to one gate voltage unintentionally affect other gate-controlled parameters, makes it difficult to control tunneling rates and energy states of the QD separately. To overcome this crosstalk effect, we present two approaches: maintaining constant conductance of two quantum point contacts (QPCs) forming the QD by compensating the effect of the plunger gate voltage on the QPCs, and interpolating between gate voltage conditions optimized for QD observation at several electron numbers. These approaches minimize crosstalk effects by dynamically adjusting barrier gate voltages as a function of plunger gate voltage. Using these methods, we successfully observed Coulomb blockade peaks throughout the entire range from N = 1 to N ≈ 20. Our methods provide a simple and effective solution for observing Coulomb blockade peaks over a wide range of electron numbers while maintaining control over the quantum states in the dot.

Advancements in semiconductor processing and material manufacturing demand innovative plasma sources capable of preventing plasma-induced damage. These industrial applications necessitate the independent generation of plasma in process regions that maintain low electron temperature and consequent low plasma potential. This study presents a plasma source that employs a magnetic filter with permanent magnets to produce a plasma with low electron temperature below 1 eV in the diffusion region under a magnetic field-free environment. Experimental results confirmed that the system maintains the electron temperature consistently below 1 eV and the plasma potential below 3 V in the diffusion region across a range of operating pressure and RF power levels, ensuring minimal sheath voltage and compatibility with sensitive processes. The plasma density demonstrated a scalable linear relationship, achieving a 40-fold increase with a 6-fold increase in RF power, while consistently maintaining low electron temperature condition. This work provides a scalable and adaptable foundation for advanced material processing techniques requiring minimal plasma-induced damage, paving the way for next-generation semiconductor fabrication and precision applications.

This study investigates the correlation between dosiomics features and Delivery Quality Assurance (DQA) results in TomoDirect radiotherapy treatments, aiming to enhance DQA accuracy and efficiency. Dosiomics features, such as shape characteristics, statistical properties, and texture metrics (e.g., GLCM, GLSZM), were extracted from RT Dose DICOM files of patients treated with TomoDirect on the Radixact X9 system. Regions of interest (ROI), such as the planning target volume (PTV), were used to isolate dose values for feature extraction. The DQA results were classified using gamma analysis (3%/3mm criteria), and statistical methods like correlation, group comparison, and regression analysis were applied to assess the relationship between these features and DQA outcomes. The analysis identified several key predictors of DQA success. Shape features, including surface area and object size, along with texture features like GLCM autocorrelation and GLDM high gray-level emphasis, showed significant correlations with DQA pass rates. The multivariate regression model explained 79.7% of the variance in DQA outcomes, emphasizing the potential of dosiomics features to predict DQA results. In addition, features related to dose uniformity and complexity, such as firstorder_10th Percentile and GLCM contrast, significantly impacted gamma pass rates. This study demonstrates that dosiomics can enhance the predictability of DQA outcomes in TomoDirect treatments. The identified features can support the development of predictive models to streamline DQA processes, improve treatment accuracy, and reduce manual verification efforts. Future research should explore integrating additional parameters and expanding these methods to other radiotherapy techniques and machines for broader applicability.

The motion of the solar system against an isotropic radiation background, such as the cosmic microwave background, induces a dipole anisotropy in the background due to the Doppler effect. Flux-limited observation of the continuum radiation from galaxies also has been studied extensively to show a dipole anisotropy due to the Doppler effect and the aberration effect. We show that a similar dipole anisotropy exists in spectral-line intensity maps, represented as either galaxy number counts or the diffuse intensity maps. The amplitude of these dipole anisotropies is determined by not only the solar velocity against the large-scale structures but also the temporal evolution of the monopole (sky-average) component. Measuring the dipole at multiple frequencies, which have mutually independent origins due to their occurrence from multiple redshifts, can provide a very accurate measure of the solar velocity thanks to the redundant information. We find that such a measurement can even constrain astrophysical parameters in the nearby universe. We explore the potential for dipole measurement of existing and upcoming surveys, and conclude that the spectral number count of galaxies through SPHEREx will be optimal for the first measurement of the dipole anisotropy in the spectral-line galaxy distribution. LIM surveys with reasonable accuracy are also found to be promising. We also discuss whether these experiments might reveal a peculiar nature of our local universe, that seems to call for a non-standard cosmology other than the simple (Lambda)CDM model as suggested by recent measures of the baryon acoustic oscillation signatures and the Alcock–Paczynski tests.

Improving carrier injection for radiative recombination in GaN light-emitting diodes (LEDs) has been a major focus for several decades. In this study, the performance of GaN LEDs was enhanced through the construction of an Si/GaN tunnel junction (TJ) via nanomembrane (NM) stacking. The n + Si nanomembrane was transfer printed onto the p + GaN layer, resulting in an n + Si/p + GaN TJ on top of the GaN epi-structure. The radiative recombination of electron–hole pairs was enhanced by the tunneling of carriers across the Si/GaN TJ into the InGaN/GaN multi-quantum wells. The improved hole injection was elucidated through the energy band diagram of the Si/GaN TJ. The increased number of injected holes in the stacked Si/GaN TJ LED leads to enhanced radiative recombination, resulting in greater output power and external quantum efficiency (EQE). Specifically, the light output power improved by 96% at 30 A/cm², and the peak EQE increased by 36% due to the formation of the stacked Si/GaN TJ on the LED. These findings can be applied to the manufacturing of electronic devices, where balancing carrier generation and injection is crucial for operational efficiency.

The development of radiative cooling paint that combines high thermal conductivity with high solar reflectance is crucial for efficient heat dissipation. However, realizing such a paint has been challenging due to the low thermal conductivity of commonly used scatterers and polymer matrices. In this work, we have successfully demonstrated a highly thermally conductive radiative cooling paint using beryllium oxide (BeO) particles as the scattering pigments. The coatings with optimized BeO content exhibit excellent thermal and optical properties, with a through-plane thermal conductivity of 4.5 Wm⁻¹ K⁻¹, solar reflectance exceeding 95%, and thermal emissivity of 0.94. The key engineering achievement was optimizing the filler content to establish a two-phase regime, where the fillers are fully embedded in the polymer matrix without the presence of air voids. Our field tests confirmed the coating’s excellent cooling performance under direct solar irradiation of ~ 1000 W m⁻², achieving a cooling temperature of around 5.6 °C. We believe this work offers valuable insights for the development of highly thermally conductive radiative cooling paints with efficient cooling performances.

The rare isotope accelerator complex for ON-line experiments uses an additional electron cyclotron resonance ion source to supply ions to users. This electron cyclotron resonance ion source can be derived from the 14.5 and 18 GHz driving frequencies. We performed an electromagnetic simulation of the plasma chamber prior to the engineering design phase. The 14.5 GHz-based electric field analysis of the model was extended to 18 GHz. We used the Drude model supported by the computer simulation technology microwave studio for the plasma simulation. The electrical field can be enhanced by accounting for the plasma effects of the Drude model despite the electric field in the vacuum being near the cylindrical wall. Therefore, we uncovered that the electric field distribution can be assessed in realistic situations by modifying the vacuum chamber shape to align with the plasma field inevitably formed by an externally applied magnetic field. In addition, the electric field in the near-axis region increased with optimization after modifying the cylindrical chamber into a plasma-shaped chamber.

This study demonstrates the fabrication and optical characterization of lithium niobate photonic devices including waveguides, beam splitters, and microring resonators on a thin-film lithium niobate platform. Through precise fabrication techniques and KOH post-cleaning following Ar-based etching, we achieved effective optical performance across key parameters such as transmission loss, splitting ratios, and Q-factors. These results show the potential of lithium niobate in advanced photonic applications, paving the way for its use in integrated on-chip photonics.

The low cost and scalability of silicon substrates have led to increasing attention to AlGaN/GaN high-electron-mobility transistors (HEMTs) on silicon wafer. We developed and simulated the GaN-based HEMT on Si wafer using the Silvaco TCAD software. The performance of rectangular-gate AlGaN/GaN HEMT on Si wafer is examined in detail with respect to the effects of channel length variation, barrier thickness variation, and gate length variation. The performance of this HEMT structure with a gate length of 100 nm and optimized channel layer thickness (CT) of 200 nm has shown a significant I_DS of 1.11 A/mm, a substantial G_m of 329.79 mS/mm, an impressive f_T of 199.40 GHz, and a notable output current of 1.71 A/mm. When the barrier layer thickness (BT) was varied from 6 to 10 nm while maintaining a 200 nm channel layer thickness, the performance declined at higher barrier thicknesses, yielding an I_DS of 0.8 A/mm, a G_m of 206 mS/mm, an f_T of 193.2 GHz, and an output current of 1.26 A/mm. Finally, this HEMT structure demonstrated superior performance with a gate length (LG) of 40 nm, exhibiting a drain current of 1.92 A/mm, a transconductance (G_m) of 465.49 mS/mm, and a cut-off frequency (f_T) of 465 GHz, and output current (I_D) of 2.11 A/mm. The optimized device structure’s high-power performance without compromising RF performance, they are suitable for millimeter-wave radar applications.