Exploiting hafnium nitride nanostructures for polarization-insensitive and wideband infrared absorption

Investigating new plasmonic materials for the design of nanostructured absorbers is in high demand. This study explores the possibility of using transition metal nitride, HfN, in the implementation of an infrared nanostructured absorber. To design and analyze a broadband absorber, a simple and easily fabricable HfN-based circular ring is mounted over a dielectric substrate with a metal backing. The designed HfN-based metasurface absorber manifests a good absorption characteristic, maintaining an absorption rate above 90% over the wide operational wavelength range of 700 nm to 1700 nm. When the incident angles of the optical light are changed from normal to higher values, the absorption characteristics of the metasurface absorber remain stable and even at θ = 60°, it shows a reasonable absorption rate of over 70%. Furthermore, it also performs insensitive behavior to the varying polarization angles owing to its inherent four-fold symmetry. Additionally, the multi-reflection cavity model has been used to validate the simulation results of the metasurface absorber. Its broad absorption bandwidth, mechanical stability, and thermal robustness make it a promising material for thermophotovoltaics and solar cells applications.