Journal of the Korean Physical Society最新文献

{"title":"Investigation of structural, optoelectronic, and thermoelectric properties of K2PdSe2, K2PdTe2, K2PtSe2, and K2PtTe2 chalcogenides","authors":"Yousfi Aissa,&nbsp;Boulebda Hicham,&nbsp;Belli Ayoub,&nbsp;Sarhani Mohammed ElSaid","doi":"10.1007/s40042-026-01601-z","DOIUrl":"10.1007/s40042-026-01601-z","url":null,"abstract":"<div><p>Potassium-based transition metal chalcogenides K₂PdSe₂, K₂PdTe₂, K₂PtSe₂, and K₂PtTe₂ represent an emerging class of layered materials with promising multifunctional properties for advanced energy conversion and optoelectronic applications. In this comprehensive first-principles study, we systematically investigate the structural, magnetic, electronic, optical, and thermoelectric properties of these compounds using the full-potential linearized muffin-tin orbitals (FPLMTO) method within density functional theory (DFT) as implemented in the WIEN2k code. Magnetic ground state determination through total energy calculations fitted to the Birch–Murnaghan equation of state reveals that K₂PdSe₂, K₂PdTe₂, and K₂PtTe₂ stabilize in the non-magnetic (NM) configuration, while K₂PtSe₂ adopts an antiferromagnetic (AFM) ground state. All four compounds crystallize in the orthorhombic Immm space group (No. 71) with two formula units per unit cell, exhibiting systematic lattice expansion from selenides to tellurides. Electronic band structure calculations reveal semiconducting behavior with direct bandgaps, with the density of states analysis showing dominant contributions from transition metal d-orbitals and chalcogen p-orbitals near the Fermi level. The optical properties, computed using the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation (GGA), demonstrate exceptional performance across the visible to near-infrared spectrum. Static dielectric constants ε1(0) range from 9.28 (K₂PtSe₂) to 12.68 (K₂PdTe₂), indicating strong polarizability and promising suitability for optoelectronic applications.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"88 11","pages":"1247 - 1257"},"PeriodicalIF":0.9,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147968161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Toward larger subband energy spacing in quantum point contacts via trench-gate engineering","authors":"Gyutae Park,&nbsp;Jihong Ju,&nbsp;Hyeon Seonwoo,&nbsp;Yunchul Chung","doi":"10.1007/s40042-026-01604-w","DOIUrl":"10.1007/s40042-026-01604-w","url":null,"abstract":"<div><p>We investigate a trench-gated quantum point contact (QPC) formed in a GaAs/AlGaAs two-dimensional electron gas (2DEG), where the trench-gate is positioned above the side gates and electrically insulated by an HfO₂ layer. This geometry enables enhanced electrostatic confinement and reduced side-gate gaps. Low-temperature transport measurements at 50 mK show that increasing the positive trench-gate voltage enhances conductance quantization and increases the subband energy spacing, reaching 5.4 meV for an 80 nm side-gate gap. Systematic measurements for side-gate gaps from 40 to 80 nm, together with electrostatic calculations based on the Davies model, reveal the existence of an optimal side-gate gap that maximizes the subband energy spacing. Extending the analysis to different 2DEG depths shows that the optimal gap scales with the 2DEG depth, while the maximum subband energy spacing decreases for deeper 2DEGs. These results indicate that both the gate geometry and the 2DEG depth critically determine the subband energy spacing, and that shallower 2DEG wafers with optimized gate gaps provide a promising route toward QPCs with larger subband energy gaps.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"88 11","pages":"1241 - 1246"},"PeriodicalIF":0.9,"publicationDate":"2026-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147968162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Operational validation of a replacement IGBT for the high voltage converter modulator in a proton accelerator at KAERI","authors":"Hae-Seong Jeong","doi":"10.1007/s40042-026-01598-5","DOIUrl":"10.1007/s40042-026-01598-5","url":null,"abstract":"<div><p>A replacement Insulated Gate Bipolar Transistor (IGBT) for the High Voltage Converter Modulator (HVCM) used in the KAERI 100-MeV proton linear accelerator was evaluated following the discontinuation of the original device. The candidate IGBT was assessed through a structured framework combining off-line switch-plate testing and on-line operation in the HVCM driving three klystrons simultaneously. Off-line measurements clarified differences in switching behavior and characteristics, while on-line measurements confirmed stable pulse generation under nominal operating conditions. Although the candidate device exhibited a modest increase in total loss energy, its lower junction-to-case thermal resistance resulted in a comparable or lower junction temperature rise. Continuous operation since August 2025 without IGBT-related faults further demonstrates the suitability and long-term reliability of the replacement device in an actual accelerator environment.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"89 on","pages":"241 - 257"},"PeriodicalIF":1.0,"publicationDate":"2026-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148459150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Beyond the curve: a machine learning approach for wobbling proton beam therapy output prediction","authors":"Kwangzoo Chung","doi":"10.1007/s40042-026-01602-y","DOIUrl":"10.1007/s40042-026-01602-y","url":null,"abstract":"<div><p>While analytical models for monitor unit prediction in wobbling proton beam therapy are well-established, they exhibit reduced accuracy in clinically extreme cases, such as large field sizes or seldom-used plan parameters. This study proposes a machine learning (ML) framework designed to act as a supportive verification tool for existing analytical models, enhancing predictive confidence across the full spectrum of treatment parameters. A pre-treatment quality assurance dataset comprising 2859 wobbling proton fields, collected between 2016 and 2024, was used to train and evaluate three ML architectures: random forest, gradient boosting machines (XGBoost), and neural networks. Input features included dosimetric and geometric variables such as distal ranges (D90, D10), spread-out Bragg peak (SOBP) length, and beam energy extracted from measurement sheets. The models were evaluated on their ability to provide reliable predictions for cases where the analytical model is known to exhibit significant deviations or fail entirely. The Machine Learning models demonstrated a strong ability to generalize from historical measurement data. For routine treatment parameters, ML predictions showed excellent agreement with the analytical fitting model. However, in extreme cases involving large field sizes and sparse data points, the ML models provided stable and reliable predictions where the analytical fitting model faltered. Among the test algorithms, XGBoost proved the most robust achieving a root mean squared percentage error of 2.79% compared to the analytical fitting model’s 5.83%. Furthermore, the ML framework successfully generated monitor unit predictions for non-standard fields where the analytical fitting model provided no output. A Machine Learning framework serves as a powerful complementary tool for monitor unit prediction in wobbling proton beam therapy. By running in parallel with established semi-empirical models, it provides an essential safety layer, offering robust predictions for non-standard fields while independently confirming results for routine cases. This synergetic approach enhances the overall reliability and safety of the clinical quality assurance workflow without discarding the proven value of traditional analytical methods.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"89 on","pages":"316 - 323"},"PeriodicalIF":1.0,"publicationDate":"2026-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148459151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Beam dynamics studies for SDTL-based 200 MeV energy upgrade of KOMAC proton linac","authors":"Seunghyun Lee,&nbsp;Seok-Ho Moon,&nbsp;Sungbin Park,&nbsp;Han-Sung Kim,&nbsp;Hyeok-Jung Kwon","doi":"10.1007/s40042-026-01599-4","DOIUrl":"10.1007/s40042-026-01599-4","url":null,"abstract":"<div><p>The Korea Multi-purpose Accelerator Complex (KOMAC) is proposing an energy upgrade for the existing 100 MeV proton linear accelerator (linac). The design for this extended linac is based on a normal-conducting separated-drift tube linac (SDTL) structure. The drift tubes (DTs) of the SDTL share the same structural configuration as those of a drift tube linac (DTL); however, they do not incorporate any quadrupole magnets within the DTs. Instead, transverse beam focusing is achieved through the incorporation of a doublet focusing structure placed between the SDTL tanks. The proposed configuration includes 5 DTs per SDTL tank, resulting in a 6-cell SDTL design. A total of 16 SDTL tanks are required to accelerate the proton beam from 100 to 200 MeV. Beam dynamics simulations and comprehensive error analyses were conducted to assess the tolerances of the linac design. Furthermore, a correction scheme was implemented to enhance the lattice tolerance by installing steerers. This paper presents preliminary studies on beam dynamics and error analysis, including orbit correction results, for the 200 MeV SDTL linac conducted at KOMAC.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"89 on","pages":"228 - 240"},"PeriodicalIF":1.0,"publicationDate":"2026-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148459152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design and optimization of a multipole-corrected mass analyzing magnet for high-current low-energy ion implantation system","authors":"Dong-Hwan Kim,&nbsp;Han-Sung Kim,&nbsp;Hyeok-Jung Kwon","doi":"10.1007/s40042-026-01564-1","DOIUrl":"10.1007/s40042-026-01564-1","url":null,"abstract":"<div><p>A modern high-current, low-energy ion implanter for semiconductor manufacturing requires a dedicated mass analyzing magnet system to achieve high beam transmission and precise mass separation. In this work, we present the design and optimization of a multipole-corrected mass analyzing magnet for a ribbon-beam-based ion implantation system. The system consists of an inductive heated cathode-type ribbon beam source, a 90°-dipole bending magnet, two quadrupole magnets, and a mass resolving slit. This horizontal ribbon beam is more susceptible to nonlinear effects such as space charge and fringe field than other conventional particle accelerator beams. Multipole fields are utilized to correct higher-order aberration and nonlinear components by multi-section design and optimization of pole shape. This paper presents magnet system design and optimization results from three-dimensional electromagnetic field and self-consistent particle tracking simulation.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"89 4","pages":"344 - 350"},"PeriodicalIF":1.0,"publicationDate":"2026-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148704215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spontaneous symmetry breaking of nano-electromechanical shuttle due to collisions","authors":"SungMin Kim,&nbsp;Sungwan Cho,&nbsp;Seong Uk Yu,&nbsp;Chulki Kim,&nbsp;Hee Chul Park","doi":"10.1007/s40042-026-01595-8","DOIUrl":"10.1007/s40042-026-01595-8","url":null,"abstract":"<div><p>We present a theoretical framework for charge transport in driven nano-electromechanical shuttles undergoing hard-wall collisions. The interplay between collisions and electric transport leads to a novel synchronization phenomenon in the shuttle dynamics. Our analysis reveals that the oscillation period increases by an integer multiple of the collision-free period, with trajectories transitioning to chaotic regimes under stronger external forces. Furthermore, rectified symmetry-breaking currents are generated when the integer multiplier is even, showing discontinuous behavior as a function of external parameters.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"88 11","pages":"1235 - 1240"},"PeriodicalIF":0.9,"publicationDate":"2026-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147968151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Predicting magnetron sputtering deposition rate through process parameters using supervised machine learning","authors":"Sri Vishnu Jami,&nbsp;Sakti Prasanna Muduli,&nbsp;Paresh Kale","doi":"10.1007/s40042-026-01596-7","DOIUrl":"10.1007/s40042-026-01596-7","url":null,"abstract":"<div><p>Magnetron sputtering, a widely used physical vapor deposition method, is a plasma-matter interaction process. The magnetron sputtering application includes semiconductor fabrication, optics, and surface coating. The key roles of sputtering in the semiconductor industry are forming interconnects, barrier layers, and electrode contacts in solar cells, integrated circuits, and other microelectronic devices. Despite wide applications and impact, rare mathematical analyses exist for predicting the deposition rate derived from first principles. A supervised machine learning approach uses process parameters such as power, target-substrate distance, and target material to determine the deposition rate. The work explains the process parameters and their impact on the deposition rate. Seven regression machine learning models are briefly discussed, with the relevance for model sputtering deposition rate, which are evaluated using parameters such as Mean Squared Error, Mean Absolute Error, and Coefficient of determination (<i>R</i>^<i>2</i>). The average performing models are tree-based regression models with <i>R</i>^<i>2</i> above 0.9 and minimal error. Random Forest and XGBoost are the top-performing models, with <i>R</i>^<i>2</i> of 0.96 and 0.97, respectively. Predicting the sputter deposition rate using optimized machine learning is a novel approach to reduce experimental time and expenditure.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"88 11","pages":"1212 - 1223"},"PeriodicalIF":0.9,"publicationDate":"2026-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147968180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bouncing universe in fractal gravity","authors":"D. D. Pawar,&nbsp;A. P. Nirwal,&nbsp;D. K. Raut,&nbsp;Shah Muhammad,&nbsp;Euaggelos E. Zotos","doi":"10.1007/s40042-026-01591-y","DOIUrl":"10.1007/s40042-026-01591-y","url":null,"abstract":"<div><p>In this study, we explore matter bounce modeling through the lens of fractal gravity. We use a non-zero parameter for the scaling factor. Also describe Type III singular bouncing cosmology evolution. The cosmological bounce occurs in such a way that the bouncing point coincides exactly with Type III singularity point. We derive the related field equations within the framework of the FRW background. Further, we obtained the deceleration parameter, expressions for pressure, density and the Equation of State parameter in terms of cosmic time <i>t</i>. We also analyze the violation of the Null and Strong energy conditions near the bounce, expressing the results in terms of cosmic time <i>t</i>. Additionally, we introduce the state-finder pair to differentiate various dark energy models. Lastly, we investigate the behavior of the adiabatic speed of sound to assess the plausibility of the proposed cosmological bouncing scenario, formulating our analysis in terms of cosmic time <i>t</i>.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"88 11","pages":"1168 - 1179"},"PeriodicalIF":0.9,"publicationDate":"2026-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147968178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhanced thermoelectric performance of Zn-doped bornite Cu5Fe1−xZnxS4","authors":"Hyeokmin Kwon,&nbsp;Il-Ho Kim","doi":"10.1007/s40042-026-01594-9","DOIUrl":"10.1007/s40042-026-01594-9","url":null,"abstract":"<div><p>Zn-doped bornite compounds (Cu₅Fe₁₋_xZn_xS₄, <i>x</i> = 0–0.06) were synthesized using mechanical alloying followed by hot pressing, and the effects of Zn substitution on phase stability, structural evolution, charge transport, and thermoelectric performance were investigated. All compositions exhibited a stable single-phase orthorhombic bornite structure without detectable secondary phases, indicating successful incorporation of Zn into the Fe sublattice. Zn substitution induced anisotropic lattice distortion, characterized by a slight contraction along the <i>a</i>-axis and expansions along the <i>b</i>- and <i>c</i>-axes, resulting in a gradual increase in unit cell volume while maintaining a homogeneous solid-solution structure. With increasing Zn content, the hole carrier concentration increased, leading to enhanced electrical conductivity, whereas the Seebeck coefficient gradually decreased, reflecting the trade-off between carrier concentration and thermopower. In contrast, the total thermal conductivity was significantly reduced by Zn substitution compared with undoped Cu₅FeS₄. The minimum total thermal conductivity of 0.32 W·m^-1·K^-1 at 523 K, with a corresponding lattice thermal conductivity of 0.24 W·m^-1·K^-1, was achieved for Cu₅Fe_0.98Zn_0.02S₄, which is attributed to enhanced phonon scattering arising from mass fluctuation and point-defect disorder induced by Zn substitution at the Fe sites. As a consequence of the combined optimization of electrical and thermal transport properties, Cu₅Fe_0.96Zn_0.04S₄ exhibited a maximum power factor of 0.51 mW·m^-1·K^-2 at 723 K, corresponding to an improvement of approximately 21% relative to undoped Cu₅FeS₄ (0.42 mW·m^-1·K^-2), while the highest dimensionless figure of merit, ZT = 0.63 at 723 K, was obtained for Cu₅Fe_0.98Zn_0.02S₄, representing an enhancement of about 34% compared with Cu₅FeS₄ (ZT = 0.47).</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"88 11","pages":"1224 - 1234"},"PeriodicalIF":0.9,"publicationDate":"2026-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147968181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}