Electron‐Beam‐Induced Nanopatterning of J‐Aggregate Thin Films for Excitonic and Photonic Response Control

Abstract Excitons play a crucial role in the optical response of various materials. Molecular aggregates, such as J‐aggregates, exhibit strong optical responses via exciton generation and coherent transport. Planar J‐aggregate thin films can even show an optically metallic response in the visible region and may be considered as alternative materials for plasmonics. However, a direct method to control the optical properties of J‐aggregate films using a top‐down approach is not reported. Here, it is shown that the excitonic response of J‐aggregate films can be locally modified by electron beam exposure, leading to a gradual change in the dielectric constant: from optically metallic (Re[ε] < 0) to dielectric (Re[ε] > 0). Nanoscale patterned films that exhibit clear polarization‐dependent transmission and photoluminescence spectra are demonstrated. The remarkable spectral features can be attributed to the excitation of optical modes in excitonic films. This work suggests that nanopatterned excitonic films may be used as functional elements in various photonic systems to achieve the collaborative synergy between excitonic and photonic elements on a single platform.