The Korean Society of Surface Science and Engineering

Silicon (Si) is widely considered a promising anode material for high-energy-density lithium-ion batteries (LIBs) owing to its exceptionally high theoretical capacity (~3579 mAh g^-1) and natural abundance. However, its practical implementation is hindered by severe volume expansion and interfacial instability during lithiation, which result in electrode degradation and low initial coulombic efficiency (ICE). Silicon oxide (SiO_x) has emerged as a viable alternative, offering improved structural integrity and more stable cycling performance. Nevertheless, it still suffers from significant ICE loss due to irreversible lithium silicate formation and lithium trapping. Metal doping has recently gained increasing attention as an effective strategy to address these limitations. Incorporation of metal elements such as Mg, Sn, Ti, Li, into SiO_x has been demonstrated to enhance electrical conductivity, stabilize both the structure and the solid electrolyte interphase (SEI), and suppress the formation of electrochemically inactive phases-leading to improved ICE and prolonged cycle life. In this review, we provide a comprehensive summary of recent advances in metal doping strategies for SiO_x-based anodes. The focus is placed on doping mechanisms, synthesis methodologies, and their impact on structural and electrochemical properties, with an emphasis on practical feasibility for next-generation LIB applications.

SiO_x, Metal Doping, Anode Material, Initial Coulombic Efficiency, Lithium-Ion Battery, Commercialization

Zn plating is a technology to prevent steel corrosion, which is a major problem that can occur in various industrial fields. Zn-Mg-Al alloy-coated steel enhances corrosion resistance by incorporating small amounts of aluminum (Al) and magnesium (Mg) into zinc, thereby extending the product’s service life and reducing resource onsumption. PosMAC steel developed and commercialized by POSCO is Zn-Mg-Al hot-dip alloy coated steels for excellent corrosion resistance, and it is widely utilized in automotive and home appliance applications. Despite their widespread use, comprehensive studies on corrosion resistance under diverse environmental exposures are rarely explored. This study evaluates the corrosion behavior of PosMAC steels exposed to high-temperature dry and humid environments for extended periods. Surface chemical composition change was analyzed using energydispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Corrosion resistance was evaluated through potentiodynamic polarization and salt spray tests. Results showed that prolonged exposure to high-temperature dry conditions decrease corrosion resistance, while high-temperature humid conditions maintained stable corrosion resistance over time. These results demonstrate that more superior corrosion resistance of steel can be achieved by exposing to high-temperature humid conditions for a long time. The improvement of corrosion resistance is attributed to the formation of Mg(OH)₂ on the surface through reactions with water vapor, highlighting the importance of environmental conditions on the performance of Zn-Mg-Al alloy coated steel.

Zn-M g-Al alloy coating; Corrosion resistance; Salt-spray test; PosMAC; Environmental test.

In this study, we report a sulfur-loaded cobalt single-atom catalyst–nitrogen-doped porous carbon composite (S@Co-NC) as a promising cathode material for aluminum–sulfur batteries. The material was derived from a zeolitic imidazolate framework (ZIF) precursor and carbonized to yield a polyhedral, high-surface-area carbon structure. Cobalt atoms were atomically dispersed via nitrogen coordination, and sulfur was efficiently infused into the porous matrix. The S@Co-NC electrode exhibited a high initial discharge capacity and maintained 411 mAh g^-1over 100 cycles over 93% Coulombic efficiency. These improvements are attributed to the catalytic role of single-atom Co and the polysulfide-trapping capability of the N-doped carbon. This work highlights the potential of single-atom catalyst design for next-generation aluminum–sulfur batteries.

Polysulfide shuttle effect; ZIF; N-doped porous carbon; single atom Co catalyst; Aluminum-sulfur batteries.

Low-temperature, oxygen-based plasma etching of thick SU-8 films was systematically examined under both pure O₂ and CO/O₂ (2.4:0.6) gas environments, with substrate temperatures varied from room temperature down to –80 °C. In pure O₂ plasmas, pronounced sidewall erosion and stepwise etch-rate fluctuations—attributable to photon-induced CO desorption, viscoelastic matrix rearrangements, and formation of volatile reaction products—resulted in significant undercutting and poor reproducibility at intermediate cryogenic temperatures. The introduction of CO to promote carbon-based passivation via the Boudouard reaction markedly reduced lateral etching by depositing a protective carbon film; however, this benefit sharply declined at temperatures ≤ –30 °C owing to sluggish carbon deposition kinetics. Furthermore, independent thermal annealing of SU-8 at 250 °C for 30 min prior to etching substantially suppressed abrupt, stepwise etch-rate variations—thereby enhancing process stability—likely due to increased crosslink density and removal of residual solvent. Optimal anisotropic profiles with minimal undercut were achieved near +10 °C, where carbon passivation and oxidative etching were balanced. These findings demonstrate that realizing high-aspect-ratio SU-8 structures with robust sidewall integrity necessitates careful, multivariable optimization of substrate temperature, gas chemistry, ion energy, and polymer pretreatment.

SU8 etching; Low-temperature; Anisotropy; Carbon passivation; Thermal annealing.

Molybdenum nitride (γ-Mo₂N) thin films were deposited on silicon (100) substrates using mid-frequency magnetron sputtering (MfMS), at selected Ar:N₂ flow rates (10:1, 5:1 and 2:1 sccm). The effect of Ar:N₂ flow rate on the microstructure, mechanical and electrical properties of the γ-Mo₂N thin films were investigated using FESEM, XRD, AFM, nanoindentation tester, and semiconductor characterization system It was confirmed by XRD analysis that the thin films were produced is γ-Mo₂N with face-centered cubic crystal structure. As the flow rate of Ar:N₂ decreased down to 5:1 sccm, the growth rate of thin film thickness reduced from 1.24 μm/h to 1.13 μm/h while the crystallite size of γ-Mo₂N thin film decreased from 15.2 nm to 10.1 nm. Consequently, the surface roughness of thin film was reduced from 3.2 nm to 2.7 nm. In addition, the γ-Mo₂N thin films deposited at the Ar:N₂ flow rate studied, at 5:1 sccm; are having the lowest resistivity (324 μΩcm) and the largest nano hardness (25.4 GPa). The results articulate that Ar:N₂ flow rate was one of the important process parameters in mid-frequency magnetron sputtering that could affect the morphology, mechanical and electrical properties of γ-Mo₂N thin films.

Mid-frequency; Sputtering; Molybdenum nitride; Ar/N₂ flow ratio; Thin Films

As the technology industry developed highly due to the Fourth Industrial Revolution, the demand and importance of high-performance semiconductor devices such as FinFET (Gate All Around), and 3D NAND Flash Memory increased. However, Since the existing dry etching is impossible to precisely etch, there is a limit to the manufacture of high-performance semiconductor devices. To solve this problem, Atomic layer etching (ALE), a new method of replacing the existing dry etching, has emerged. But the process time is long and when plasma is discharged in the adsorption step, other particles such as ions and electrons are generated in addition to radicals, and are accelerated by the electric field to unintentionally etch the surface. In this study, To solve the problems of surface damage and long process time, the ALE process technology which removes ions and electrons and selectively adsorbs radicals during the adsorption step was studied. In addition, precise etching was performed by controlling the amount of ion energy and ion flux in the desorption step through the bias driving frequency and pulse. This was applied to the atomic layer etching process. Using the Ion saturation current probe, It was confirmed that Ions and electrons could be grounded through mesh-gird and radicals could be selectively adsorbed by confirming that the Ion current generated during the adsorption step is zero. In addition, It was confirmed that Ion energy and Ion flux can be adjusted with bias frequency and pulse by analyzing the Ion energy distribution function with the Retarding Field Energy Analyzer. Thereafter, Atomic layer etching process was performed with an SOI wafer using radical selective adsorption and Ion energy control. As a result, EPC(Etch per cycle)s of 1.1Å/cycle were measured for both 12.56MHz, 41.68MHz, and 60MHz bias frequency at 7V. In the case of an atomic layer etching process while applying a bias in the form of a pulse, 1.1Å/cycle was confirmed when the pulse duty was 100% and 60%. At pulse duty 30%, the EPC was reduced at 12.56MHz, 41.68MHz. because the Ion flux required for etching was insufficient. But at 60MHz, ion flux was sufficient even at pulse duty 30%, the EPC of 1.1Å/cycle was confirmed. In this study, More precise etching was possible through radical selective adsorption using mesh-grid and Ion energy controll using bias driving frequency and pulse.

Selective Adsorption; Ion Energy Control; Atomic Layer Etching.

The development of efficient catalysts for the hydrogen evolution reaction (HER) plays a critical role in water splitting for green hydrogen production. Due to the high cost of platinum, which is commonly used as an HER catalyst, extensive research has recently been conducted on non-noble metal-based catalysts. In this study, NiS₂ catalysts were synthesized via a hydrothermal method as non-noble metal HER catalysts, and their electrochemical catalytic properties were investigated. The morphology of the hydrothermally synthesized NiS₂ catalysts was controlled to form either hollow or non-hollow structures by varying the amount of sulfur precursor, L-cysteine. Structural analysis and electrochemical performance comparisons were conducted accordingly. Linear sweep voltammetry (LSV) revealed that the hollow-structured NiS₂ catalysts exhibited improved overpotential performance. Furthermore, kinetic analysis using Tafel plots indicated enhanced hydrogen adsorption kinetics in the hollow-structured NiS₂ catalysts compared to their non-hollow counterparts.

Nickel sulfide; Hollow structure; Electrocatalyst; Hydrogen evolution reaction; Water splitting.