이준희
Lee, Jun Hee

이준희

Graduate School of Semiconductor Materials and Devices Engineering(반도체 소재ㆍ부품 대학원)

  • Quantum Materials for Energy Conversion Lab.
  • Website
Research Interests
Quantum simulation;materials genome;Li battery;photocatalyst;fuel cell;Catalytic materials;Ferroelectrics;Magnetic materials;Ferroelectricity;Magnetism;Topology;Density Functional Theory;QUANTUM ESPRESSO;Molecular Dynamics;Numerical Analysis;자성체;강유전체;촉매 재료;위상;자성;강유전성;수치 해석;분자동역학;밀도범함수이론
Lab Description
The recently discovered orthorhombic HfO2 has prompted research to develop devices that utilize its robust ferroelectricity at reduced dimensions. HfO2 has attractive advantages compared to conventional perovskite ferroelectrics in its compatibility with Si-based CMOS (Complementary Metal-Oxide Semiconductor) technique, in addition to its scalability to thin films with substantial ferroelectric polarizations (~10nm)However, there are setbacks to devices, such as its large coercive field compared to that of conventional perovskites by one order of magnitude. The large coercive fields used to switch ferroelectric polarization can damage HfO2 films, resulting in electric breakdown and shortening their endurance. A recent research trend focuses on reducing the coercive fields using various dopants. Various factors from dopants are studied to tune the coercive fields such as volume change, the monoclinic phase fraction, and the dopant size effects. Still, the mechanism of why some elements (such as Si), significantly reduce the coercive field has not been fully understood. Hence, we explore on how to reduce the coercive field of HfO2 by substitution doping and why Si is a critical element in lowering coercive fields using first-principle simulations. Furthermore, Our laboratory plans to apply this study to the tons of ultra-dense semiconductor memory materials.
Using first-principles density functional theory calculations, we explore the chemical activity of various oxide films focusing on the oxygen evolution reaction (OER), the bottleneck of water splitting. Especially the reactivity of the surface is tuned by electric dipoles dynamically induced by the adsorbed species during the intermediate steps of the reaction while the initial and final steps remain unaffected. In order to investigate OER reaction material and mechanism, the combined effects of the dynamically induced dipoles and epitaxial strain strongly reduce rate-limiting thermodynamic barriers and significantly improve the efficiency of the reaction.
Nd2Fe14B is well known permanent magnet for its high coercive field and large magnetic moment, thereby it has been used steadily for a long time. Using DFT calculation, we will analyze how doping elements affect magnetic properties when other rare earth metal such as Tb, Ce, and Y are doped into Nd2Fe14B. Ultimately, based on these predictions, we aim to develop a permanent magnet that has better coercive field and magnetic moment but low cost.

Kim, ChanseokJeon, DasomKim, NayeongRyu, JungkiLee, Jun Hee

Article Issue Date2024-03 View2

Park, K.Kim, J.Choi, S.Fan, S.Kim, C.Oh, D. G.Lee, N.Cheong, S. -WKiryukhin, V.Choi, Y. J. , et al

Article Issue Date2023-05 View11

Yoon, Ki-YongPark, JuhyungLee, HosikSeo, Ji HuiKwak, Myung-JunLee, Jun HeeJang, Ji-Hyun

Article Issue Date2022-05 View8

Yang, HyemiLee, Hyun-JaeJo, JinhyeongKim, Chang HoonLee, Jun Hee

Article Issue Date2020-12 View4
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