Localized Surface Plasmonic Resonance of an Al Nanorod Array on High-Quality AlN Templates into the Far-UVC Spectral Region

Localized surface plasmon resonance (LSPR) in the far-UVC regions is demonstrated with a monolithic Al nanorod array on an AlN template. A 40 nm low-index SiO₂ spacer is inserted between the AlN and Al nanorods to reduce the ambient refractive index to blue-shift the extinction peak wavelength. To further blue-shift the extinction peak down to the far-UVC region with a resolution that is compatible with the metal lift-off process by e-beam lithography, the Al nanorods have to be sufficiently high to decouple the LSPR mode at the top corners from the conventional dominant mode at the bottom Al/SiO₂ interface. For the 60 nm-high Al nanorods, LSPR at the top corners becomes the dominant mode, and the dominant extinction peak was measured to be 236 nm with a rod diameter of 50 nm.