Effects of Processing Atmosphere on FemtosecondLaser-Induced Microstructuring and SurfaceOxidation of Mo, Ta, and W Refractory Metals

<title>Abstract</title> <p>The quality of the aperture walls, surface oxidation, and redeposition defects in metal grids can affect electron extraction, beam modulation, and long-term operational stability. This study conducted femtosecond laser scribing and cutting experiments in air and low-oxygen argon atmospheres to compare their surface structural evolution, laser-induced penetration zone (LIPSS) width, cut cross-sectional morphology, and oxidation behavior for three candidate refractory metal grid materials-molybdenum (Mo), tantalum (Ta), and tungsten (W). The results indicate: Mo is more prone to oxidation particles, spatter redeposition, and localized melt droplets in air; an Argon atmosphere improves surface cleanliness and cross-sectional continuity; Ta is most sensitive to oxygen; LIPSS can form at relatively low energy densities in air, accompanied by a large-scale, weakly influenced zone, while an Argon atmosphere significantly suppresses surface oxidation and reduces pore wall roughness; W exhibits minimal differences in morphology and cross-sections under both atmospheres, with its processing behavior primarily governed by energy density and ablation thresholds. Energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) results further indicate that the O signal in air-processed samples is generally stronger than in argon-processed samples, with the percentage of oxygen atoms in Ta decreasing from 33.02\((%)\) to 6.65\((%)\), demonstrating the highest atmosphere sensitivity. A comprehensive analysis of surface morphology, cross-sectional profiles, and elemental analysis reveals that a low-oxygen argon atmosphere is conducive to low-oxidation, low-redeposition grid cutting of Mo and Ta, whereas process optimization for W should prioritize control of energy density and heat accumulation. This study provides a basis for material and atmosphere selection in the femtosecond laser precision machining of refractory metal grids.</p>