"To do successful research, you don't need to know everything. You just need to know one thing that isn't known."
"Anything worth doing is worth doing twice, the first time quick and dirty and the second time the best way you can."
Arthur Leonard Schawlow (1921 ~ 1999; Nobel Prize, 1981, in physics for his work on lasers)
Welcome to the Yo-Sep Min Group at the Department of Chemical Engineering, Konkuk University, Seoul, Korea. Our research is based on chemical approaches, notably atomic layer deposition (ALD), to prepare functional materials for electronic and/or energy devices. Additionally, through in-situ analyses of the ALD process, we are studying the mechanisms governing the deposition of diverse films.
Recent
Publications
Ultra-Strong Carbon Fibers via Atomic Layer Deposition-Induced Dual-Scale Defect Regulation
Se Youn Cho, Min Eui Leb, Zhenyu Jin, Jiho Choi, Yo-Sep Min*, and Sungho Lee*, Journal of Materials Science & Technology 2027, 289, 51.
Carbon fibers (CFs) with high tensile strength are highly desirable as reinforcement materials in advanced composites. However, their theoretical tensile strength (∼180 GPa), estimated from sp2 C–C bond strength in defect-free structures, remains unattainable because of intrinsic surface and internal defects. Here, we demonstrate an atomic layer deposition (ALD)-based strategy enabling dual-scale defect mitigation in commercial polyacrylonitrile-based CFs through simultaneous surface passivation and internal structural reinforcement. Conformal Al2O3 layers reduced surface irregularities and stress concentration sites, while infiltrated Al-containing species promoted interfacial bonding and cross-linking within the carbon microstructure. Consequently, the tensile strength of commercial CFs was significantly enhanced after ALD treatment, with T1000G fibers exhibiting a ∼41% increase in tensile strength and reaching 8.45 ± 1.35 GPa. Structural analyses using X-ray diffraction, Raman spectroscopy, small-angle X-ray scattering, field‑emission transmission electron microscopy, and energy-dispersive X-ray spectroscopy mapping revealed reduced microvoid dimensions without significant alteration of the graphitic microstructure. These findings establish ALD-induced dual-scale defect mitigation as an effective and potentially industrially applicable approach for producing next-generation ultra-strong CFs.
Static Atomic Layer Deposition for Enhanced Precursor Infiltration in Porous Materials: a Combined Experimental and Numerical Analysis
Eunsang Lee, Eunji Kang, Gaeun Kim, Jihyun Kim, Hunkyu Lee, and Yo-Sep Min*, Chemistry of Materials 2026, 38(16), 8366.
Atomic layer deposition (ALD) is widely used to coat porous materials, but conventional continuous-flow ALD often suffers from limited infiltration depth and inefficient precursor utilization in high-aspect-ratio pore networks. To address these limitations, we investigated static ALD, a modified process that introduces an additional closed-valve duration step between precursor injection and purge. This step prolongs precursor residence time, promoting deeper infiltration and greater precursor utilization, especially for low-reactivity precursors. Static ALD was evaluated using diethylzinc (DEZ) and tetraethoxysilane (TEOS) as representative precursors with contrasting sticking coefficients. To interpret the experimental behavior, we extended a continuum diffusion–reaction model by incorporating a dynamic boundary condition that accounts for progressive precursor depletion in a closed-valve chamber under finite-supply conditions. Combined experimental and numerical results show that static ALD yields significantly greater mass gain and deeper infiltration than conventional ALD at a fixed accumulated injection time for each precursor, particularly for low-reactivity precursors such as TEOS. Parametric simulations further reveal that the optimal duration time depends strongly on precursor reactivity, as low-reactivity precursors require longer residence times for efficient infiltration. Surface coverage profiles are governed primarily by the sticking coefficient, whereas process configuration determines the achievable infiltration depth. Overall, this study establishes a modeling-guided framework for tailoring static ALD to precursor properties and substrate geometries, enabling more efficient and scalable ALD in porous nanostructures.