Characterization of the Plasmonic Properties of Hafnium Nitride Single Nanoparticles on a Gold Mirror

Abstract

The plasmonic properties of HfN single nanoparticles on a gold mirror separated by an Al2O3 dielectric spacer were investigated with the FDTD simulator of Lumerical and by Integrating Sphere Microscopy. The simulations showed that decreasing the gap size, by decreasing the spacer thickness or decreasing the particle size leads to a blue shift of the gap plasmon resonance. The largest E-field enhancement was found for a HfN nanoparticle with an 80 nm diameter on a 3 nm dielectric spacer. This E-field enhancement was found to be more than 7 times higher than the field enhancement found for Au nanoparticles of the same size. HfN nanoparticles where synthesized via solid-state metathesis, which resulted in an average particle size of 22.7 nm in diameter. One HfN single nanoparticle with a diameter of 25.0 nm on a 10 nm spacer thickness was characterized by integrating sphere microscopy. The extinction spectrum of this nanoparticle seemed to contain a peak at 480.8 nm; however, due to the high degree of noise in this region, the validity of this result is uncertain. Improving the dropcasting method to obtain more suitable nanoparticles or developing a synthesis method to synthesize larger HfN nanoparticles, could allow for more data of a better quality to be collected. Currently no investigations were done into the existence of picocavities in HfN nanoparticles.