Highlight Articles

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  Highly sensitive UV photodetector based on Ag-doped ZnO nanorods grown by hydrothermal process

  Samer Abdulsalam Aldhehabi, Boubakeur Essedik Belkerk, Raouia Zernadji et al.

  J. Korean Phys. Soc. 86(5), 359 - 371 (2025)

  Ultraviolet (UV) photodetector based on doped ZnO are widely reported in literature. However, their sensitivity is limited due to structural defects and morphology. Herein, we present the fabrication and performance of UV photodetectors based silver (Ag)-doped ZnO nanorods. To improve the performance of UV photodetectors based on ZnO nanorods, in terms of sensitivity and current gain, we explored the impact of low Ag doping on the morphology and optical properties of these nanorods. The ZnO nanorods were grown on glass substrates using a hydrothermal process with varying Ag concentration. The I–V characteristics of the ZnO nanorod photodetectors were analyzed under a bias of 5 V. Notably, the addition of Ag significantly improved the photodetector performance, achieving a 9840% increase in photodetection sensitivity at 375 nm under 0.19 mW/cm2 UV illumination, compared to non-doped ZnO nanorods. Furthermore, the results highlight how Ag doping alters the wavelength of peak photoresponse and reduces the rise and decay time constants of the photocurrent, thus improving device response. These findings demonstrate the potential of Ag doping to address critical limitations in ZnO-based UV photodetectors and pave the way for their integration into advanced optoelectronic applications.
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  Fast-variable elimination in stochastic SIRS epidemic model with Itô processes

  Yung-Gyung Kang, Jeong-Man Park

  J. Korean Phys. Soc. 86(4), 263 - 268 (2025)

  We investigate the dynamics of the SIRS epidemic model through both deterministic and stochastic frameworks, focusing on the effects of random fluctuations in key epidemiological parameters. After presenting the deterministic SIRS model using differential equations, the model is extended to include stochasticity by incorporating Itô stochastic differential equations (SDEs), where infection, recovery, and loss-of-immunity rates are treated as random variables. The corresponding Fokker-Planck equation is derived, capturing the evolution of the probability distribution of the infected population over time. We perform a linear stability analysis of the deterministic model and apply the fast-variable elimination method to reduce the two-variable SDE system to a single slow variable, leading to a simplified Fokker-Planck equation that describes the stationary distribution of the infected population. This reduction reveals that the stochastic epidemic threshold depends on the variances in the infection and recovery rates, but not on the variability in the loss-of-immunity rate. Simulation results,
  conducted using a Gillespie-type algorithm, validate the theoretical findings.
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  Electromagnetic simulation of an electron cyclotron resonance ion source considering plasma effects

  Deok-Min Kim, In-Seok Hong

  J. Korean Phys. Soc. 86(3), 173 - 179 (2025)

  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.
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  Effective tuning methods for few-electron regime in gate-defined quantum dots

  Chanuk Yang, Hwanchul Jung, Hyung Kook Choi et al.

  J. Korean Phys. Soc. 86(2), 106 - 112 (2025)

  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.
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  smCamera: all-in-one software package for single-molecule data acquisition and data analysis

  Kyung Suk Lee, Taekjip Ha

  J. Korean Phys. Soc. 86(1), 1 - 13 (2025)

  smCamera is an all-in-one software package which aims to alleviate steep learning curves of the data acquisition
  and analysis. From recording movies through extraction of time series of single-molecule fluorescence resonance energy transfer (smFRET), everything can be done in a single program without any additional software or programming languages. Although smCamera has not been published before, it has been distributed to facilitate adaption of smFRET experiments and there has been requests for support for this software. We hope that this work answers questions from researchers using smCamera and also provides an opportunity to introduce and distribute smCamera for new users.
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  Enhanced figure of merit of polycrystalline PtSe₂/PtSe₂ structures at room temperature by a facile wet-transfer stacking method

  Jung‑Min Cho, Yun‑Ho Kim, Won‑Yong Lee et al.

  J. Korean Phys. Soc. 85(8), 643 - 649 (2024)

  We present a promising approach to significantly improve the in-plane thermoelectric (TE) figure-of-merit (ZT) of few-layer PtSe2 films at room temperature by stacking PtSe2 layers with uniform thickness. As the number of stacked layers increases, the Seebeck coefficient enhances significantly with relatively constant electrical conductivity. Meanwhile, the thermal conductivity shows a significant decrease, resulting in an increase in the ZT factor by ~380% compared to the single-layer PtSe2 film. This remarkable increase in ZT factor shows the potential for a considerable improvement in TE properties of semimetallic PtSe2 with a new technique called facile wet-transfer stacking.
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  Initial image-based approach may enhance direct reciprocity for cooperation evolution

  Sunhee Chae, Hyeong‑Chai Jeong

  J. Korean Phys. Soc. 85(6), 525 - 533 (2024)

  We explore the evolution of strategies in the iterated Prisoner’s Dilemma within finite populations, where players repeatedly interact with the same partners and have access to public records of others' actions. We analyze a variety of discriminating strategies that utilize both direct reciprocity (based on repeated interactions) and indirect reciprocity (based on public information), along with strategies of always cooperating or always defecting. Our results show that a strategy combining tit-for-tat for repeated encounters and indirect information for initial interactions is generally the most effective, except when the benefits greatly outweigh the costs, where the standard tit-for-tat strategy prevails.