Highly stable and reusable ZrHfN nanorod films: An alternative SERS substrate via reactive co-sputtering with OAD technique

Transition metal nitride nanostructures have garnered significant attention as promising alternative plasmonic sensing materials for surface-enhanced Raman scattering (SERS) substrates due to their low cost and favorable physical, chemical, and plasmonic properties. This work demonstrates the deposition and characterization of zirconium hafnium nitride (ZrHfN) nanorod films as an alternative SERS substrate. The ZrHfN nanorod films were prepared using closed-field dual-cathode DC unbalanced reactive magnetron sputtering with the oblique angle deposition (OAD) technique. The influence of the sputtering current of the Hf target was investigated and comprehensively characterized using FE-SEM, GIXRD, AFM, TEM-EDS mapping, XPS, and XAS. Using Rhodamine 6G (R6G) dye as the target analyte, the SERS performance of the ZrHfN nanorod films was evaluated. Our systematic investigation shows that the optimal ZrHfN nanorod films, prepared at a sputtering current of 800 mA for the Hf target, exhibited an enhancement factor of 9.07 × 10⁵ with 4.87 %-RSD at 1512 cm⁻¹. Moreover, the limit of detection for optimal ternary nitride SERS substrate was determined to be 1.88 × 10⁻⁷ M, with excellent reusability, long-term stability, and high-temperature resistance. Additionally, detecting trace levels of toxic paraquat herbicide was demonstrated, indicating potential for practical applications.