Adhesion‐Engineering‐Enabled “Sketch and Peel” Lithography for Aluminum Plasmonic Nanogaps

Abstract Aluminum is one of the most significant plasmonic materials for its advantage of low cost, natural abundance, as well as the ultraviolet optical response. However, it is still very challengeable for the fabrication of aluminum plasmonic nanogaps, which greatly limits the applications of aluminum plasmonics considering the essential role of nanogaps for electric field enhancement. Here, the reliable patterning of aluminum plasmonic nanogaps employing a modified “Sketch and Peel” lithography strategy is demonstrated. By introducing a self‐assembled monolayer to engineer the surface energy of the substrate, the adhesiveness of the aluminum film outside outline template is significantly decreased to implement the selective peeling process. Besides, the near‐infrared Fano resonance in the periodic aluminum heptamers has been first revealed by enabling the strong electric field and plasmon coupling in the aluminum nanostructures with 10 nm scale nanogaps. In addition, surface‐enhanced Raman spectroscopy and infrared spectroscopy are also illustrated in the rationally designed aluminum dimers. The present work provides a robust method to obtain aluminum plasmonic nanogaps, which may play an important role on the practical applications of aluminum plasmonics, such as surface‐enhanced vibration spectroscopy and nonlinear optics.