Gas-aggregated core–shell ZrN@SiN nanoparticles with enhanced thermal stability for plasmonic applications at high temperatures

Group IV metal nitrides are often considered a viable replacement for gold in numerous plasmonic applications that require high temperatures. However, despite exhibiting a high melting point, these materials are prone to oxidation in an oxygen-rich environment, leading to an undesirable change or loss of the plasmonic response. This work developed an environmentally friendly method based on reactive magnetron sputtering of Zr for the synthesis of ZrN nanoparticles (NPs) with their in-flight coating by an rf-sputtered SiN shell. The resultant core–shell NPs are characterized by cubic morphology, with a 15 nm ZrN core enveloped by a 5–15 nm SiN shell. The ZrN@SiN NPs demonstrate localized surface plasmon resonance (LSPR), which can be adjusted from 580 to 850 nm by tuning the porosity and, consequently, the effective refractive index of SiN. The SiN shell attenuates the plasmonic sensitivity of ZrN NPs, but protects them from postdeposition oxidation in air, preserving LSPR at temperatures above 400°C. Thus, this research proposes a one-step synthesis of ZrN@SiN NPs with controllable optical properties, enhanced thermal stability, and promising features for plasmonic applications at high temperatures.