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22 results on '"Ryu, Sangkyun"'

2. Highly ordered lead-free double perovskite halides by design

Author

Ahn, Chang Won, Jo, Jae Hun, Kim, Jong Chan, Ullah, Hamid, Ryu, Sangkyun, Hwang, Younghun, Choi, Jin San, Lee, Jongmin, Lee, Sanghan, Jeen, Hyoungjeen, Shin, Young-Han, Jeong, Hu Young, Kim, Ill Won, and Kim, Tae Heon

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Lead-free double perovskite halides are emerging optoelectronic materials that are alternatives to lead-based perovskite halides. Recently, single-crystalline double perovskite halides were synthesized, and their intriguing functional properties were demonstrated. Despite such pioneering works, lead-free double perovskite halides with better crystallinity are still in demand for applications to novel optoelectronic devices. Here, we realized highly crystalline Cs2AgBiBr6 single crystals with a well-defined atomic ordering on the microscopic scale. We avoided the formation of Ag vacancies and the subsequent secondary Cs3Bi2Br9 by manipulating the initial chemical environments in hydrothermal synthesis. The suppression of Ag vacancies allows us to reduce the trap density in the as-grown crystals and to enhance the carrier mobility further. Our design strategy is applicable for fabricating other lead-free halide materials with high crystallinity.

Published
2020
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7. Effect of helium ion beam irradiation on the physical properties of Si-doped Ga2O3epitaxial thin films

Author

Mun, Yeongdeuk, Jung, Seungho, Chung, Hyeyun, Jeong, Jaehoon, Ryu, Sangkyun, Park, Jun Kue, Hong, Tae Eun, Ok, Jong Mok, Park, Sungkyun, and Jeen, Hyoungjeen

Abstract

Here, we studied the effect of the helium ion beam irradiation on the structural and transport properties of Si-doped β-Ga2O3(Si:Ga2O3) epitaxial thin films. Epitaxial Si:Ga2O3thin films were grown on (0001) Al2O3substrates by pulsed laser deposition. Despite different Si concentrations, the films remain (−201) epitaxially oriented with respect to (0001) Al2O3. Furthermore, Helium ion beam irradiation was used to mimic massive cosmic ray (e.g., α-particle) irradiation on the structural and electronic modification. As a result, it is observed that the structural and transport properties of epitaxial Si:Ga2O3thin films were degraded owing to the He ion irradiation.

Published
2025
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8. Multiferroism in strained strontium hexaferrite epitaxial thin films

Author

Lee, Joonhyuk, primary, Cho, Sam Yeon, additional, Kim, Inhwan, additional, Rouleau, Christopher M., additional, Kang, Kungwan, additional, Ryu, Sangkyun, additional, Heo, Yunseok, additional, Keum, Jong K., additional, Pajerowski, Daniel M., additional, Kim, Younghak, additional, Bu, Sang Don, additional, Lee, Jaekwang, additional, and Jeen, Hyoungjeen, additional

Published
2024
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13. Anisotropic Electrical Conductivity of Oxygen-Deficient Tungsten Oxide Films with Epitaxially Stabilized 1D Atomic Defect Tunnels

Author

Kim, Gowoon, Feng, Bin, Ryu, Sangkyun, Cho, Hai Jun, Jeen, Hyoungjeen, Ikuhara, Yuichi, Ohta, Hiromichi, Kim, Gowoon, Feng, Bin, Ryu, Sangkyun, Cho, Hai Jun, Jeen, Hyoungjeen, Ikuhara, Yuichi, and Ohta, Hiromichi

Abstract

Materials having an anisotropic crystal structure often exhibit anisotropy in the electrical conductivity. Compared to complex transition-metal oxides (TMOs), simple TMOs rarely show large anisotropic electrical conductivity due to their simple crystal structure. Here, we focus on the anisotropy in the electrical conductivity of a simple TMO, oxygen-deficient tungsten oxide (WOx) with an anisotropic crystal structure. We fabricated several WOx films by the pulsed laser deposition technique on the lattice-matched (110)-oriented LaAlO3 substrate under a controlled oxygen atmosphere. The crystallographic analyses of the WOx films revealed that highly dense atomic defect tunnels were aligned one-dimensionally (1D) along [001] LaAlO3. The electrical conductivity along the 1D atomic defect tunnels was similar to 5 times larger than that across the tunnels. The present approach, introduction of 1D atomic defect tunnels, might be useful to design simple TMOs exhibiting anisotropic electrical conductivity.

Published
2021

16. Highly ordered lead-free double perovskite halides by design

Author

Ahn, Chang Won, primary, Jo, Jae Hun, additional, Chan Kim, Jong, additional, Ullah, Hamid, additional, Ryu, Sangkyun, additional, Hwang, Younghun, additional, San Choi, Jin, additional, Lee, Jongmin, additional, Lee, Sanghan, additional, Jeen, Hyoungjeen, additional, Shin, Young-Han, additional, Jeong, Hu Young, additional, Kim, Ill Won, additional, and Kim, Tae Heon, additional

Published
2020
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19. Publisher's Note: “Growth of electronically distinct manganite thin films by modulating cation stoichiometry” [Appl. Phys. Lett. 110, 261601 (2017)]

Author

Ryu, Sangkyun, primary, Lee, Joonhyuk, additional, Ahn, Eunyoung, additional, Kim, Jiwoong, additional, Herklotz, Andreas, additional, Bae, Jong-Seong, additional, Nyung Lee, Ho, additional, Kim, Younghak, additional, Kim, Jae-Young, additional, Jeon, Tae-Yeol, additional, Cho, Jinhyung, additional, Park, Sungkyun, additional, and Jeen, Hyoungjeen, additional

Published
2017
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20. Growth of electronically distinct manganite thin films by modulating cation stoichiometry

Author

Ryu, Sangkyun, primary, Lee, Joonhyuk, additional, Ahn, Eunyoung, additional, Kim, Jiwoong, additional, Herklotz, Andreas, additional, Bae, Jong-Seong, additional, Lee, Ho Nyung, additional, Kim, Younghak, additional, Kim, Jae-Young, additional, Jeon, Tae-Yeol, additional, Cho, Jinhyung, additional, Park, Sungkyun, additional, and Jeen, Hyoungjeen, additional

Published
2017
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22. Strain-effected physical properties of ferromagnetic insulating La 0.88 Sr 0.12 MnO 3 thin films.

Author

Kim Y, Ryu S, and Jeen H

Abstract

The functional perovskite La 1- x Sr x MnO 3 (LSMO) possesses various exotic phases owing to competing physical parameters and internal degrees of freedom. In particular, the nature of the ferromagnetic insulating phase (FMI) has not been adequately explored, resulting in a limited understanding of the relationship between crystal structure and magnetism. To investigate this structure-property relationship, epitaxial La 0.88 Sr 0.12 MnO 3 thin films were grown on two different substrates, (001) SrTiO 3 and (001) (LaAlO 3 ) 0.3 (Sr 2 AlTaO 6 ) 0.7 , by pulsed laser deposition. Element-specific and surface-sensitive techniques were applied in conjunction with bulk magnetometry to investigate the inextricable link between the structures and magnetic properties of the films and the effects of tuning the strain. The results unambiguously demonstrate that structure-property relationship of a FMI LSMO tuned by strain has a crucial role for manipulating the properties in the FMI regime., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Published
2019
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