Seung-Cheol Lee

Heterointerfacial modulation in 2D transition metal dichalcogenides (TMDs) offers a unique route to introduce a portfolio of fascinating properties, allowing layered materials to manifest multi‐dimensional features for advanced device applications. Herein, functionally distinct heterostructures of 2H‐MoS ₂ are engineered via controlled Ar and O ₂ plasma treatments, resulting in 1T/2H‐MoS ₂ and MoO ₃ /2H‐MoS interfaces, respectively, which in turn facilitate selective gas chemisorption. The tailored heterointerfaces reshape local electronic and surface energy landscapes of 2H‐MoS ₂ , where electron transfer from metallic 1T domains strengthens n‐type conductivity, while hole injection from MoO ₃ reinforces p‐type behavior. Experimental measurements, supported by density functional theory, indicate that carrier‐density modulation, together with the formation of favorable adsorption sites, governs the chemisorption behavior of oxidizing NO ₂ and reducing NH3 molecules. The 1T/2H‐MoS ₂ and MoO ₃ /2H‐MoS ₂ sensors selectively detect NO ₂ and NH ₃ with minimum detection limits of 165 and 138 ppb, respectively, at room temperature. The practical applicability of the sensors, demonstrated by fabricating a portable sensor array, showcases effective NO ₂ detection in vehicular exhaust and NH ₃ sensing in spoiled meat, underscoring their potential for environmental and food‐safety monitoring. By strategically engineering heterointerfaces, this study translates tunable TMD properties into chemisorption‐controlled gas discrimination.

Van der Waals (vdW) epitaxy can integrate lattice-mismatched crystals with atomically sharp, pristine interfaces. However, translating this concept to atomic layer deposition (ALD), a standard for low-temperature, layer-by-layer growth, remains challenging because precursors adsorb transiently on chemically inert vdW basal planes, leading to physisorption-limited nucleation and poor crystalline ordering. Here, we introduce diffusion-steered epitaxial ALD (Epi-ALD), redefining vdW surfaces as programmable kinetic-thermodynamic landscapes and demonstrate highly crystalline tellurium at 150°C. Epi-ALD couples surface-potential-encoded physisorption with long-range diffusion to promote ordered nucleation and epitaxial alignment. This “soft” pathway enables strain-free tellurium epitaxy with a pristine vdW gap (∼1.4 angstrom) despite lattice mismatch (>3.6%) and generalizes across multiple vdW templates. Retaining hallmark advantages of ALD including scalability and uniformity, we further program in-plane orientation through vdW symmetry engineering to achieve quasi-single-crystalline tellurium films with pronounced anisotropy and a chiral anomaly signature. Our work establishes a universal, low-thermal-budget approach for integrating vdW materials and expands the scope of epitaxy within the ALD paradigm.

The ability of Mo ₂ C to stabilize and regenerate defective MoO ₂ surface domains without succumbing to excessive oxidation defines its alkaline HER activity.

Complete catalytic oxidation of methane is an effective strategy for greenhouse gas mitigation and clean energy conversion.

Cost-effective metal-free polymeric carbon nitride (PCN) drives various photocatalytic reactions under λ ≤ 450 nm when prepared by the conventional thermal polymerization process.Though copolymerization method is a straightforward approach to...

This study presents a first-principles and semiclassical analysis of the puzzling observation that a La_0.7Sr_0.3MnO₃ (LSMO) thin film exhibits larger Gilbert damping than an LSMO/Pt bilayer, contrary to conventional spin-pumping expectations. Density-functional theory with Wannier interpolation yields an intrinsic damping of α int LSMO ≈ 1.4 × 10 − 3 , supporting an extrinsic origin of the high experimental value. Guided by the self-induced inverse spin Hall effect demonstrated in LSMO (Gupta et al 2024 Phys. Rev. B 109 014437), we argue that the large spin Hall angle | θ SH | ≃ 0.093 and low longitudinal conductivity of LSMO enable an efficient conversion of spin current to charge current boosting the effective damping. In the LSMO/Pt heterostructures the Pt cap shunts the charge current, raising σ _xx and reducing the interfacial | θ SH | to 0.007. A Valet–Fert analysis for layer-resolved ab-initio spin accumulation gives the Pt spin-diffusion length and a non-negligible antidamping SOT coefficient, qualitatively accounting for the observed damping reduction under current bias. The seemingly anomalous damping hierarchy is thus reconciled without invoking additional interfacial mechanisms. The distinct length scales governing spin-pumping normalization, namely, the short absorption depth relevant to self-pumping in a single LSMO film versus the full magnetic thickness applicable to an LSMO/Pt bilayer, are crucial in this context. This observation suggests a practical design strategy: by simultaneously tuning the spin Hall-to-longitudinal conductivity ratio and the spin-diffusion length, one can engineer heterostructures with minimized magnetic losses for spin–orbitronics applications.

This work explores the role of oxygen in industrial methane oxidation. Oxygen, a well-known oxidizing agent, drives CH$_4$ conversion to CO$_2$ and H$_2$O. We report how oxygen influences oxidation on single Pd and PdO clusters supported on CeO$_2$(111). Oxygen is introduced by (1) lattice O in PdO and (2) O$_2$ adsorption on an isolated Pd atom, forming PdO$_x$ clusters. Density-functional theory (DFT) mapped multiple reaction pathways on the Pd$_1$/PdO$_1$@CeO$_2$(111) surface; both Pd and PdO clusters were found to thermodynamically favour methane activation. The computed barrier for CH$_4$ activation is 0.63 eV on PdO$_1$@CeO$_2$(111). A single Pd atom markedly accelerates O$_2$ dissociation to PdO$_2$, and the presence of lattice oxygen lowers this barrier by 0.36 eV relative to an oxygen-deficient surface, enhancing catalytic efficiency. Reaction selectivity, coverage-dependent production rates, degree of rate control (DRC), and intrinsic turnover frequency (TOF) were quantified through steady-state microkinetic modelling. The simulations predict full conversion of CH$_4$ to CO$_2$ and H$_2$O above 600 K, whereas partial-oxidation intermediates dominate at lower temperature and high O coverage. Rate constants for all elementary steps were derived via the Sure Independence Screening and Sparsifying Operator (SISSO) symbolic-regression method, yielding a concise predictive expression based on charge, coordination number, and key Pd-O/C-H distances. These combined DFT-microkinetic-SISSO results clarify oxygen's mechanistic participation and provide practical guidelines for designing Pd/CeO$_2$ catalysts with improved activity toward methane oxidation, a reaction of pressing environmental and industrial importance.