Plasmonic Resonance Shifts in Gold Nanoparticles-Thermochromic VO2 Thin Film Hybrid Platforms: A Joint Experimental and Numerical Study

The combination of the phase transition in thermochromic vanadium dioxide (VO₂) with plasmonic nanoparticles paves the way for applications in various fields, including optical sensing, advanced coatings, and dynamic optical devices. This study presents a simple fabrication method to control both the size and surface coverage of NPs combined with VO₂. First, a thermochromic VO₂ coating with a phase transition at 68 °C is synthesized using reactive magnetron sputtering. Then, monodisperse 30 nm diameter gold NPs are bonded to the VO₂ surface using (3-aminopropyl)trimethoxysilane (APTMS) linkers, examining the effect of immersion duration on surface coverage. Two platforms are developed: a VO₂ thin film with a monolayer of NPs and a configuration with NPs between two VO₂ films. The temperature-dependent plasmonic response of these platforms is measured by extinction spectroscopy, showing a significant wavelength resonance shift of approximately 10 nm for the first platform and 20 nm for the second. Optical simulations analyze this shift over various geometries, from isolated NPs to fully covered NPs, achieving a 60 nm shift for NPs embedded in a thin VO₂ film. This study demonstrates an effective approach to synthesizing thermochromic VO₂ coatings with gold NPs, offering insights into the plasmonic properties of hybrid platforms.