Small-period DUV plasmonic Al nanohole arrays fabricated by wet colloidal template/substrate and the interface and hole size-dependent E-field enhancement effect

The fabrication of a uniform small-period Al nanohole array with pronounced deep-ultraviolet (DUV) plasmon is highly valuable in enhancing the intrinsic fluorescence of biochemical molecules for label-free detection. Since metal nanohole arrays have distinct optical transmission properties, it is often questioned whether the maximum electric field (E-field) enhancement effect coincides with the transmission peaks or transmission troughs. We efficiently fabricated uniform DUV plasmonic Al nanohole arrays with small periods by using a wet colloidal template/substrate in a facile and low-cost way. Further, theoretical simulation demonstrates that such an Al nanohole array exhibits interface and hole size-dependent multi-band E-field enhancement effects. We have analyzed the maximum E-field enhancement effect as well as the corresponding exciting wavelength λ_{Al−air, Emax} (or λ_{Al−SiO2, Emax}). At the metal–air interface, λ_{Al−air, Emax} is close to the transmission peak wavelength when the metal hole diameter is relatively small compared to the period, while λ_{Al−air, Emax} approaches the transmission trough wavelength when the hole diameter is relatively large. At the metal–SiO₂ interface, the results are more complicated. The research will provide a reference for the simple synthesis of uniform and small-period Al nanohole arrays and promote the fundamental understanding of the E-field enhancement of the nanohole array. The multi-band E-field enhancement extended to the DUV region will be important for label-free optical detection of multiple biochemical molecules.