Formation of Armored Silicon Nanowires Array via High-Repetition-Rate Femtosecond Laser Oxidation for Robust Surface-Enhanced Raman Scattering Detection

Superhydrophobic nanostructures with dense hotspots and high concentration efficiency are of paramount importance for highly sensitive surface-enhanced Raman scattering (SERS) detection. However, their low mechanical strength makes them susceptible to damage from external interferences, leading to hotspot loss and superhydrophobicity failure. In this study, robust SERS detection is achieved using an armored superhydrophobic silicon nanowires array. A micro/nanocross-scale oxide mask is created through high-repetition-rate femtosecond laser oxidation to fabricate the armored nanowires array. The underlying mechanisms of the nanoparticle layer serving as a mask in deep reactive ion etching (DRIE) are analyzed to elucidate the formation of the silicon nanowires. The armored nanowires array SERS substrate exhibits a high contact angle of 158°, demonstrating exceptional analyte enrichment capability. Combined with the dense hotspots provided by the high aspect ratio nanostructures, the detection limit for Rhodamine 6G is 10–13 M, and the enhancement factor (EF) is 4.35 × 109. After undergoing various mechanical tests, the substrate maintains its superhydrophobicity along with a stable Raman signal enhancement, demonstrating its resistance to potential external interference in SERS detection. The sensitive detection of various analytes highlights the promising applications of the armored nanowires substrate in diverse SERS scenarios.