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Start Over Author "Lee, Sang" Journal journal of the korean physical society
696 results on '"Lee, Sang"'

14. Generation of energetic ions with non-Maxwellian energy distribution from a double-layer target irradiated by an ultra-intense laser pulse

Author

Kim, Ha-Na, Lee, Kitae, Kumar, Manoj, Ryu, Woo-Je, Le, Cuong Nhat, Jeong, Young Uk, Kim, Kyung Nam, Park, Seong Hee, Jeon, Min Yong, Choi, Il Woo, Lee, Seong Geun, Kang, Seung Woo, Lee, Sang Hwa, Jeon, Cheonha, Jang, Yong Ha, Lee, Hwang Woon, Yoon, Jin Woo, Sung, Jae Hee, Lee, Seong Ku, and Nam, Chang Hee

Published
2022
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20. Enhanced figure of merit of polycrystalline PtSe2/PtSe2structures at room temperature by a facile wet-transfer stacking method

Author

Cho, Jung-Min, Kim, Yun-Ho, Lee, Won-Yong, Choi, Jae Won, Park, No-Won, Das, Sree Sourav, Zebarjadi, Mona, Kim, Gil-Sung, and Lee, Sang-Kwon

Abstract

We report a promising strategy to enhance the in-plane thermoelectric (TE) figure of merit (ZT) of few-layer semimetallic PtSe2films at 300 K by piling up PtSe2layers with the same thickness (3 nm) as stacked PtSe2/PtSe2(3-nm/3-nm) homostructures by a wet-transfer method. We observed that the Seebeck coefficient was enhanced meaningfully upon increasing the number of stacked layers and exceeded ~ 173.2 μV/K with a relatively constant electrical conductivity of ~ 18.4 S/cm at 300 K. By contrast, as the number of layers increased, thermal conductivity also showed a significant reduction, and ultimately, the ZT factor increased by ~ 380% compared to the single-stacked PtSe2structure. Such an increase in the ZT factor shows the possibility of a considerable improvement in the TE properties of semimetallic PtSe2with a new technique called facile wet-transfer stacking. The proposed method is expected to play a very important role in future microscopic cooling and energy-generating TE device applications.

Published
2024
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34. Optimization for Axial Resolution, Depth Range, and Sensitivity of Spectral Domain Optical Coherence Tomography at 1.3 µm.

Author

Lee, Sang-Won, Jeong, Hyun-Woo, Kim, Beop-Min, Ahn, Yeh-Chan, Jung, Woonggyu, and Chen, Zhongping

Subjects
Biomedical Imaging, Bioengineering, Spectral domain optical coherence tomography, Axial resolution, Depth range, Sensitivity, Mathematical Sciences, Physical Sciences, Applied Physics
Abstract

We have developed high-speed and high-resolution spectral domain optical coherence tomography at 1.3 µm using an InGaAs line-scan camera and a broadband light source with the bandwidth of 170 nm that produces a theoretical axial resolution of 4.4 µm in air. We compared axial resolutions from point spread functions (PSFs) and depth ranges while changing the full spectral bandwidth detected by the camera and describing the optimization process for the axial resolution, the depth range, and the sensitivity for SD-OCT system. We found that SD-OCT at 1.3 µm cannot satisfy the conditions both below the axial resolution of 5 µm and above the depth range of 2 mm because of the restricted pixel number of the line-scan camera. To scan a large depth range, the axial resolution has to be sacrificed. In addition, the sensitivity rolls off slowly as a function of the depth if a large depth range is scanned. On the other hand, if the axial resolution needs to be close to the theoretical one, the depth range becomes limited and the sensitivity decays quickly. Since we have to maintain a reasonable depth range of 2.0 mm, we chose the spectrum full bandwidth of 214 nm captured by the detector to balance the axial resolution of 8.2 µm. In this setting, the sensitivity of our OCT system was measured at 107.1 dB. Theoretical and experimental results are compared and presented in this paper.

Published
2009

45. Simultaneous enhancement of electromagnetic interference shielding and infrared transmittance based on SnO2thin films

Author

Lee, Sang-Seok and Park, Il-Kyu

Abstract

Mn-doped SnO2thin films were fabricated to enhance two conflicting properties of the electromagnetic interference (EMI) shielding effectiveness and the infrared (IR) wavelength ranges. As a magnetic element, manganese (Mn) was doped into the SnO2thin films at an over-doping level of 300 mM to increase its magnetic permeability. As the molar content of Mn increases, the preferred growth plane of the SnO2thin films changes from (200) to (115) planes. Although all SnO2thin films showed diamagnetic properties due to the strong diamagnetism of the substrate and SnO2, the magnetic susceptibility of the Mn-doped SnO2films slightly decreased with increasing the Mn content from 0 to 60 mM, while it increased again with the doping content above it. As the Mn doping content increased from 0 to 150 mM, the sheet resistance of SnO2films continuously increased from 98 to 128 Ω/sq. As the Mn content increases from 30 to 120 mM, the IR transmittance at 4 μm increases from 37 to 47%, while the EMI shielding effectiveness at 10 GHz increases from 8.7 to 9.0 dB. The abnormal result of increased shielding effectiveness despite increased sheet resistance was due to increased magnetic permeability due to the addition of Mn. As the Mn content exceeds 150 mM, Mn-related metal clusters are formed inside the thin film, reducing the magnetic susceptibility and EMI shielding.

Published
2024
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46. Random-singlet-like state emergent in s= 5/2 frustrated cubic lattice

Author

Lee, Chanhyeon, Lee, Sang-Kwon, Lee, Suheon, van Tol, J., and Choi, Kwang-Yong

Abstract

We employ thermodynamic and electron spin resonance (ESR) techniques to elucidate the effects of quenched disorder on a ground state of s=5/2frustrated cubic antiferromagnet La3Sb3Mn2O14. We observe the development of multiple ESR lines for temperatures below 80 K. Concomitantly, the ESR linewidth exhibits a power-law increase, accompanied by an intriguing shift in resonance fields. These observations point to the occurrence of inhomogeneous magnetism. Additionally, acmagnetic susceptibility and magnetization data obey a scaling relation of χ′(H,T)and M(H, T) in μBH/kBTwith the scaling exponent α=0.53. This scaling behavior alludes to the formation of a random-singlet-like state and the presence of abundant low-lying excitations. Our results highlight the concerted interplay of strong disorder and frustration to stabilize a putative random-singlet state even in classical and high-dimensional spin systems.

Published
2024
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