Titanium nitride plasmonic nanohole arrays with polymer coating: Optical properties and their humidity-induced modifications

The use of titanium nitride (TiN) for the fabrication of plasmonic structures such as nanohole arrays (NHAs) can enable their integration into optoelectronic devices on the Silicon (Si) platform, for example, for the realization of on-chip chemical sensors and biosensors based on refractometric transducing. With a corresponding functionalization of the TiN nanohole arrays such ultra-compact devices can be used in the realization of various affinity sensors and sensor systems, for example cost-effective electronic noses for the early detection of gases in the food industry or in agriculture. In this work, we focus on two types of coating for functionalization of TiN nanohole arrays: electrochemically synthesized poly-N-methylaniline and Layer-by-Layer deposited polyacrylic-acid/poly-allylamine (PAA/PAH). Our investigation comprises the experimental characterization of the optical properties of TiN nanhole arrays coated with polymer layers of different thicknesses as well as a comparison with simulation results. We demonstrate the potential of our setup sensing applications by measuring changes in optical properties of TiN nanohole arrays coated with PAA/PAH upon exposure to air of different humidity.