Journal of the Korean Physical Society最新文献

The negatively charged state of nitrogen vacancy centre (NV^–) in diamond have been exploited in recent studies of magnetometry and quantum information processing. Nevertheless, the useful signal of NV^– for these applications can be deteriorated by the neutrally charged state (NV⁰) which acts as backgrounds. In recent studies, it has been reported that simultaneous excitation of green (532 nm) laser combined with infrared (1030, 1040, 1064 nm) laser can enhance the emission from NV^– while suppressing signal from NV⁰. Under such laser excitation conditions, however, the underlying mechanism of the photo-induced conversion between two charged states is still not fully understood. In our work, based on multi-photon absorption of IR, we propose a simple model to explain the mutual contribution of green and IR lasers to promote the NV^– population. Our model recovers the detailed featured observed in our experiment, and also can reconcile the results in previous literatures.

Heterostructure materials have gained significant research interest due to their distinct physical properties. Toxic gases severely affect the respiratory system of the human body. We propose an in-plane monolayer heterostructure based on transition metal dichalcogenides (TMD) to investigate the effect of toxic gas adsorption. The toxic gas molecules are adsorbed on top of the chalcogen-atom of the in-plane TMD heterostructure. The electronic structure calculations reflect that the band gap of the proposed host material remains almost unchanged upon the adsorption of gas molecules. The gas adsorption leads to the nearly unaltered valance band and conduction band. This is due to the lack of hybridization between the molecular orbitals of the adsorbate and the host material. The Mulliken population method confirms the charge transfer between the host in-plane TMD heterostructure and the adsorbed gas molecules. Furthermore, it is observed that the adsorption of gas molecules significantly changes the dielectric and optical response of the TMD in-plane heterostructure. Our investigations demonstrate that the proposed material has the potential for toxic gas sensing.

Weak value amplification (WVA) is a powerful technique in quantum metrology, enabling the detection of small signals that are typically challenging to measure. However, conventional WVA methods often suffer from low post-selection probabilities, which diminish the practical advantages of amplified signals. In this work, we propose and demonstrate an improved WVA scheme using photon recycling, where non-post-selected photons are reused in additional amplification processes. By implementing this recycling-enhanced method with effectively three photon recycling rounds, we achieve improvement of a factor of 1.66 ± 0.01 in post-selection probability and 1.56 ± 0.01 in amplification of the weak value. Additionally, we simulate the impact of optical path losses on the WVA probability. This allows us to determine the saturation limits of our photon recycling approach. This work provides a pathway toward more efficient WVA, significantly advancing precision measurement capabilities in quantum metrology and related sensing applications.

Calculations of electric field strength in various structures are essential in the design of most electrical and electronic equipment and devices, because electric field tendencies vary greatly with respect to a given voltage, dielectric constants of insulating media, and the geometry of the structure. Electric field simulation is very convenient to calculate and predict electric field tendencies, but it is time-consuming, expensive, and difficult to understand the physical meaning with. To address this problem in a simpler way than time-consuming and costly electric field simulations, we derive analytical equation-based solutions for pre-designing electrical and electronic devices. In this paper, we consider a simple mathematical model based on Laplace equation, particularly with respect to asymmetrically arranged dielectric structures. In these structures, we analyze electric field tendencies using axis rotation and Legendre polynomials associated with each fitted axis, especially in asymmetrically arranged models.

X-ray irradiators are used to inactivate T-cell function to prevent the risk of transfusion-associated graft-versus-host disease (TA-GVHD). Absorbed dose of 25–50 Gy within 5 min with a dose uniformity ratio (DUR) below 1.5 are recommended for inactivating T cells while sparing other blood components. In this study, different backscatter plate materials were utilized to improve dose uniformity within the entire blood phantom for a single X-ray blood irradiator using Monte Carlo simulation (MCNP6). Based on the simulation results, Be, acrylic, and Al were selected as backscatter plates for their high backscatter ratios. Dose uniformity across the entire blood phantom improved by 29.56%, 21.43%, and 10.44% when using 10 cm Be, 10 cm acrylic, and 4 cm Al as backscatter plates, respectively. Using a backscatter plate improved dose uniformity across the entire blood phantom hence improving blood irradiation efficiency. However, DUR exceeding 1.5 is due to substantial dose difference between the surface and bottom regions of the blood phantom. In future studies, additional filters will be explored to improve DUR and achieve the recommended value.

As a thin film encapsulation method, atomic layer deposition (ALD) has the potential to provide superior protection for organic light-emitting diodes (OLEDs). However, the application of H₂O and O₂ plasma in the traditional ALD process has not yet resulted in a successful moisture barrier. The large dipole moment of H₂O may result in excess residual hydroxyl groups, and the flux of charged particles from O₂ plasma can damage organic materials. Here, we suggest the use of ozone (O₃) as an alternative reactant to mitigate these limiting factors. It is a powerful oxidizer and is much more volatile than other oxidizing agents. Thus, O₃ is a promising oxygen source to improve moisture barrier properties for OLEDs. This work describes the dependence of O₃ concentration on the moisture barrier properties of Al₂O₃ thin films prepared by ozone-based ALD at 100 °C. Trimethylaluminum and O₃ were utilized as aluminum and oxygen precursors, respectively. The O₃ concentration varied from 100 to 400 g/m³ in increments of 100 g/m³. An increase in O₃ concentration resulted in a significant enhancement in the moisture barrier performance of Al₂O₃, with values improving from 7.1 × 10⁻⁴ to 1.9 × 10⁻⁵ g/m²/day. Further characterization indicated that Al₂O₃ thin films produced at elevated O₃ concentrations exhibited superior physical and chemical properties compared to those generated at lower O₃ concentrations.

Proton minibeam radiation therapy (pMBRT) has emerged as a promising radiation treatment modality, offering enhanced tissue-sparing effects compared to conventional proton therapy. For clinical application, we developed a pMBRT system with the largest field size (30 × 40 cm2) in the world, and conducted a comprehensive dosimetric evaluation of its characteristics. Our system consists of a large-area multi-slit collimator (MSC), a depth-dose modulator, a neutron absorber, a range shifter, and a custom snout compatible with the conventional proton therapy machines. We investigated two energy conditions (170 MeV with and 200 MeV without a range shifter), varying air gap and scatterer configurations to simulate clinical treatments. Lateral dose profiles showed peak and valley dose standard deviations below 5.5% of their respective means. Analysis of scatterer characteristics using the peak-to-valley dose ratio (PVDR) showed that as scatterer thickness increased, the PVDR approached 1 just beneath the phantom surface. Conversely, under low-scattering conditions, the PVDR at the phantom surface exceeded 15. For shallow tumors, a high PVDR at the surface is desired, with a rapid decrease near the tumor's depth. The depth-dose modulation effect was analyzed using air gaps and lead scatterers to amplify multiple Coulomb scattering. Monte Carlo simulations confirmed a significant reduction in secondary neutrons due to the neutron absorber. In conclusion, our system generates minibeams with a uniform dose envelope. Excellent depth-dose modulation using scatterers facilitates simultaneous skin protection and shallow-depth tumor treatment. By mitigating secondary neutrons, the system can also reduce radiation toxicity, enhancing its clinical viability.

The purpose of the research presented is to investigate the protective capacities against gamma-ray and X-ray of high-density polyethylene materials reinforced with different concentrations oxide of lead and bismuth. The materials under study were exposed to a range of gamma ray energy levels and their protective efficiency is quantitatively evaluated through the analytical measurement of several parameters, including mass attenuation coefficient, linear attenuation coefficient and half-value layer. The results derived from both theoretical calculations by Phy-x and simulated outcomes by the Geant4 simulation tool demonstrate a commendable level of correlation and consistency, thereby reinforcing the validity of the findings reported in this study. As photon energy increased, the radiation protection efficiency decreased, while as thickness increased, the radiation protection efficiency increased. It is particularly noteworthy that high-density polyethylene composites, reinforced with specific concentrations of lead and bismuth, exhibit superior radiation shielding properties. This remarkable performance can be attributed to the strategic dispersion of heavy metals as well as their associated density characteristics, which together contribute to the effectiveness of these materials in reducing harmful radiation. Finally, the fast neutron removal cross section was also calculated for polymer composites. In conclusion, these findings emphasize the potential of lead–bismuth-reinforced high-density polyethylene composites as promising materials for radiation shielding applications.

The electrical property changes in monolayer MoS₂ transistors were analyzed after bistriflimide (H-TFSI) treatment, which dissociates into hydrogen cations and TFSI anions in solution, followed by intensive acetone rinsing. Charge trapping effects were examined by varying the delay time (0.1, 1, 5 s) between voltage application and current measurement, revealing changes in electrical hysteresis. While degradation in device performance was primarily attributed to TFSI anion adsorbates, a transition to counterclockwise hysteresis was observed as H⁺ ion effects became more pronounced, leading to a reduction of degradation or slight improvement in performance. To further assess interface trap characteristics, low-frequency noise modeling was conducted for each device condition, enabling the extraction of trap density and Coulomb scattering effects. The reversibility of H-TFSI treatment effects was also evaluated through a 24-h acetone rinse. The results indicated that the impact of H⁺ ions was almost entirely reversed, restoring the interface trap density to its initial state. However, carrier mobility did not fully recover, suggesting that residual TFSI anion adsorbates remained on the surface, contributing to persistent degradation. These findings demonstrate that hydrogen cations can sufficiently penetrate and exit from both MoS₂ and SiO₂, allowing defect neutralization to be reset through aggressive rinsing. In contrast, TFSI anions, which adsorb onto the surface, are not fully removable using liquid-phase cleaning methods. This highlights a potential processing strategy in which a passivation layer, impermeable to large molecules, is placed on top of the device before H-TFSI treatment, enabling selective defect passivation solely by H⁺ ions.

This study gives our calculation of the (T-X) phase diagram for the mainly smectic–hexatic phase transitions in the binary mixtures of THI14 + MPR6. By expanding the free energy in terms of the order parameters with the biquadratic coupling in the Landau mean field model, the phase line equations are obtained and they are fitted to the experimental (T-X) data from the literature. The first-order and the second-order transitions are considered between the smectic and hexatic phases in the existence of the triple and tricritical (TCP) points in those binary mixtures. Our study indicates that the observed behavior of the first-order and the second-order (smectic–hexatic) transitions can be characterized in the binary mixtures studied by the Landau models given here.