Ultrafast Room-Temperature Nanofabrication via Ozone-Based Gas-Phase Metal-Assisted Chemical Etching for High-Performance Silicon Photodetectors

High-aspect-ratio silicon nanostructures are essential building blocks for next-generation electronics, but their fabrication remains challenging due to process complexities and structural instabilities. Here, this study presents an unprecedented gas-phase metal-assisted chemical etching (GP-MACE) strategy using high-purity ozone (O3) as an oxidizing agent. This approach achieves remarkable etching rates of approximate to 1 mu m min-1 at room temperature-70 times faster than conventional oxygen-based processes-while maintaining superior structural integrity. The enhanced oxidation potential of O3 (E0 = 2.08 V) enables precise control over the etching mechanism, yielding vertical nanowires with minimal surface defects, as confirmed by the unity critical-depth-to-maximum-depth ratio and three-fold reduction in surface porosity compared to liquid-phase processes. Leveraging this exceptional structural quality, it demonstrates high-performance photodetectors utilizing a doping-free Al2O3/Si core-shell architecture. The conformal Al2O3 coating induces an inversion layer that functions analogously to a p-n junction while simultaneously providing surface passivation, enabling efficient carrier separation without conventional thermal doping. The photodetector exhibits superior responsivity (0.45 A W-1) and stable switching characteristics even under zero-bias conditions. This room-temperature nanofabrication strategy, combining unprecedented etching rates with superior structural control, provides a promising platform for industrial-scale manufacturing of high-performance nanodevices.