Cathodoluminescence of SiO₂-Si nanotips fabricated via FIB milling

SiO₂-Si nanotips were controllably fabricated using focused ion beam milling technology on a 0.5 mm-thick silicon substrate with a 300 nm-thick SiO₂ layer. A milling current of 30 kV: 20 pA enabled the efficient fabrication of sub-100 nm nanotips. Cubic polynomial fittings were employed to model the relationship between target sizes and both actual sizes and milling times, facilitating outcome prediction and controllable fabrication. Successful fabrication of a 9 × 8 nanotip array and a composite structure (18 × 2 nanotip array + three nanowalls) verified the flexibility and controllability of the FIB method. Cathodoluminescence peaks at 460 and 650 nm were assigned to bridged hole-trapping oxygen deficiency centers and non-bridging oxygen hole centers in a-SiO₂, respectively, while the 560 nm peak originated from Si clusters formed by phase separation in the SiO₂ layer after FIB milling. The integrated cathodoluminescence intensities of these nanotips are 5-8 times higher than that of original samples. This study suggests an experimental and theoretical foundation for developing nanoscale optical devices and their potential applications in super-resolution imaging.