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Your search keyword '"Lee, Hyun Hwi"' showing total 119 results
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119 results on '"Lee, Hyun Hwi"'

1. Atomic arrangement of van der Waals heterostructures using X-ray scattering and crystal truncation rod analysis

Author

Kim, Ryung, Choi, Byoung Ki, Lee, Kyeong Jun, Kim, Hyuk Jin, Lee, Hyun Hwi, Rhee, Tae Gyu, Khim, Yeong Gwang, Chang, Young Jun, and Chang, Seo Hyoung

Subjects
Condensed Matter - Materials Science
Abstract

Vanadium diselenide (VSe2) has intriguing physical properties such as unexpected ferromagnetism at the two-dimensional limit. However, the experimental results for room temperature ferromagnetism are still controversial and depend on the detailed crystal structure and stoichiometry. Here we introduce crystal truncation rod (CTR) analysis to investigate the atomic arrangement of bilayer VSe2 and bilayer graphene (BLG) hetero-structures grown on a 6H-SiC(0001) substrate. Using non-destructive CTR analysis, we were able to obtain electron density profiles and detailed crystal structure of the VSe2/BLG heterostructures. Specifically, the out-of-plane lattice parameters of each VSe2 layer were modulated by the interface compared to that of the bulk VSe2 1T phase. The atomic arrangement of the VSe2/BLG heterostructure provides deeper understanding and insight for elucidating the magnetic properties of the van der Waals heterostructure., Comment: 17 pages, 4 figures

Published
2023
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7. Negative differential capacitance in ultrathin ferroelectric hafnia

Author

Jo, Sanghyun, Lee, Hyangsook, Choe, Duk-Hyun, Kim, Jung-Hwa, Lee, Yun Seong, Kwon, Owoong, Nam, Seunggeol, Park, Yoonsang, Kim, Kihong, Chae, Byeong Gyu, Kim, Sangwook, Kang, Seunghun, Moon, Taehwan, Bae, Hagyoul, Won, Jung Yeon, Yun, Dong-Jin, Jeong, Myoungho, Lee, Hyun Hwi, Cho, Yeonchoo, Lee, Kwang-Hee, Lee, Hyun Jae, Lee, Sangjun, Nam, Kab-Jin, Jung, Dongjin, Kuh, Bong Jin, Ha, Daewon, Kim, Yongsung, Park, Seongjun, Kim, Yunseok, Lee, Eunha, and Heo, Jinseong

Published
2023
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14. Dual Chalcogen‐Bonding Interaction for High‐Performance Filterless Narrowband Organic Photodetectors

Author

Kim, Hyeong‐Ju, primary, Kim, Bongsu, additional, Yun, Sungyoung, additional, Yun, Dong‐Jin, additional, Choi, Taejin, additional, Lee, Sangjun, additional, Minami, Daiki, additional, Heo, Chul‐Joon, additional, Lim, Juhyung, additional, Shibuya, Hiromasa, additional, Lim, Younhee, additional, Shin, Jisoo, additional, Hong, Hyerim, additional, Park, Jeong‐Il, additional, Fang, Feifei, additional, Seo, Hwijoung, additional, Yi, Jeoungin, additional, Park, Sangho, additional, Lee, Hyun Hwi, additional, and Park, Kyung‐Bae, additional

Published
2024
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24. Impact of molecular symmetry on crystallization pathways in highly supersaturated KH2PO4 solutions.

Author

Cho, Yong Chan, Lee, Sooheyong, Wang, Lei, Lee, Yun-Hee, Kim, Seongheun, Lee, Hyun-Hwi, Lee, John Jonghyun, and Lee, Geun Woo

Abstract

Solute structure and its evolution in supersaturated aqueous solutions are key clues to understand Ostwald’s step rule. Here, we measure the structural evolution of solute molecules in highly supersaturated solutions of KH2PO4 (KDP) and NH4H2PO4 (ADP) using a combination of electrostatic levitation and synchrotron X-ray scattering. The measurement reveals the existence of a solution-solution transition in KDP solution, caused by changing molecular symmetries and structural evolution of the solution with supersaturation. Moreover, we find that the molecular symmetry of H2PO4- impacts on phase selection. These findings manifest that molecular symmetry and its structural evolution can govern the crystallization pathways in aqueous solutions, explaining the microscopic origin of Ostwald’s step rule.The molecular symmetry of solute structure in aqueous solutions is a key clue to understand Ostwald’s step rule. Here, the authors show that molecular symmetry and its structural evolution can govern the crystallization pathways in aqueous solutions. [ABSTRACT FROM AUTHOR]

Published
2024
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29. Novel Diffusion‐Regulated Layering Methodology to Improve Blend Miscibility and Thermal Stability of Organic Photovoltaics.

Author

Lee, Chihyung, Jo, Hyeon‐Yeong, Nam, Minwoo, Hong, Janghee, Kim, Gyu‐Hee, Lee, Hyun Hwi, Kim, Jehan, Chang, Rakwoo, and Ko, Doo‐Hyun

Subjects
MISCIBILITY, PHOTOVOLTAIC power generation, GLASS transition temperature, THERMAL stability, GLASS transitions
Abstract

Extensive research on bulk‐heterojunction (BHJ) optimization has advanced organic photovoltaics (OPVs). However, the need for research addressing the issue of morphological instability and ensuring long‐term durability remains a priority. Herein, a diffusion‐governed morphological modification methodology via a sequential deposition (SD) process comprising ternary components with low miscibility is demonstrated. Sequential coating of a high glass transition temperature (Tg) material and a host binary blend induces a concentration difference between successively coated layers, allowing for effective blending of immiscible materials during solvent evaporation. The enhanced miscibility of the SD‐processed BHJ layer facilitates molecular interactions between the high Tg material and the host materials, thereby increasing the Tg of the BHJ blend. The SD‐processed OPVs exhibit superior photovoltaic performance and suppressed glass transition under thermal stress compared to reference OPVs fabricated via a conventional method. After 500 h of thermal aging at 85 °C, the SD‐BHJ OPV retains over 80% of its initial efficiency, whereas the reference device shows a drastic drop to below 80% of its initial efficiency after only 80 h. This study provides a step toward efficient, long‐term stable OPVs by overcoming the limitations of blend miscibility and poor thermal durability of conventional BHJ systems via a SD process. [ABSTRACT FROM AUTHOR]

Published
2024
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30. Hierarchical Zr-doped Fe2O3 photoanodes decorated with in situ Au nanoparticles via a surfactant-assisted one-step hydrothermal approach for efficient photoelectrochemical water splitting.

Author

Anushkkaran, Periyasamy, Mahadik, Mahadeo A., Chae, Weon-Sik, Lee, Hyun Hwi, Choi, Sun Hee, and Jang, Jum Suk

Abstract

Achieving highly effective catalytic activity in photoelectrochemical (PEC) water splitting has become a challenge in the fabrication of Fe2O3 photoanodes due to their poor electrical conductivity and surface charge recombination. This study outlines a one-step hydrothermal route for the design of surfactant-assisted in situ Au nanoparticle (NP)-integrated Zr-doped Fe2O3 photoanodes for PEC water splitting. A cetyltrimethylammonium bromide (CTAB) surfactant and Au-incorporated Zr-doped Fe2O3 photoanode achieved a photocurrent density of 2.30 mA cm−2 at 1.23 V vs. RHE (1.23 VRHE). CTAB promoted the adsorption of Au NPs on the Zr-FeOOH during the synthesis, while Au NPs accelerated the charge transfer kinetics. The loaded Au NPs enhanced the separation of photo-generated electron–hole pairs; as a consequence, Au NPs effectively shuttled the holes from the hematite to the photoelectrode/electrolyte interface, leading to improved photocatalytic activity. Further, the optimized Zr-HT/CTAB/Au photoanode exhibited an intrinsic solar-to-chemical conversion (ISTC) efficiency of 1.034%. Moreover, impressively, the deposition of a NiCo(OH)x cocatalyst enhanced the PEC performance to 2.72 mA cm−2 at 1.23 VRHE. This study presents a potentially fruitful strategy for simultaneous in situ decoration of a surfactant and Au NPs with photoanodes for PEC water splitting. [ABSTRACT FROM AUTHOR]

Published
2023
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45. Giant Orbital Anisotropy with Strong Spin–Orbit Coupling Established at the Pseudomorphic Interface of the Co/Pd Superlattice

Author

Kim, Sanghoon, primary, Pathak, Sachin, additional, Rhim, Sonny H., additional, Cha, Jongin, additional, Jekal, Soyoung, additional, Hong, Soon Cheol, additional, Lee, Hyun Hwi, additional, Park, Sung‐Hun, additional, Lee, Han‐Koo, additional, Park, Jae‐Hoon, additional, Lee, Soogil, additional, Steinrück, Hans‐Georg, additional, Mehta, Apurva, additional, Wang, Shan X., additional, and Hong, Jongill, additional

Published
2022
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