Enhancing Fabry−Pérot Cavity Response with a Plasmonic Molecule−Au Nanoparticle Multilayer for Broadband UV-To-Near-IR Absorbance

Abstract

Nanostructures are of great interest as they can be readily chemically synthesized with controlled structure, and they exhibit strong structure−property relationships. In turn, this suggests that nanostructured materials and devices can be fabricated with tunable properties, including optoelectronic response. Here, we show that we can generate superabsorbance across a broadband by integrating a nanostructured filmplasmonic Au nanoparticles (NPs) cross-linked with π-conjugated 1,4-benzenedithiol (BDT) moleculesas the top layer of a trilayer Fabry−Pérot (FP) device. Components of the device that are tuned include thickness of molecule−Au NP film, the presence of a 28 nm FP dielectric spacer, and type of adhesion layer (Cr vs Ti) for the top layer. We have demonstrated that broadband absorbance (i.e., reduction in reflectance using a 100 nm thick Au film reference) from 200 nm to 1200 nm exceeds 1.0 for most wavelengths (i.e., 90% reduction in light intensity). Analysis using finite difference time domain (FDTD) modeling provides qualitative insight into the enhancement due to FP cavity formation and the effects of the adhesion layer on overall absorbance. The numerical results also separately determined the fraction of absorbed power within various layers of the device. These results demonstrate tuning and significantly extending the performance range of trilayer FP devices, an important architecture, using a nanomaterial strategy.