Inverted optical functionality of phase change material surfaces through Mie resonances of VO2@Si core–shell structures

Vanadium dioxide (VO2) has attracted extensive attention due to its reversible transition from the insulator to metal phase at a critical temperature of 68◦C. Below the critical temperature VO2 transmits the infrared radiation in the insulator phase, whereas above the critical temperature VO2 reflects the infrared portion of the incident radiation. However, smart surface interfaces for high-temperature emitter surfaces require the opposite functionality within the 1–3 µm spectral range. Here, we demonstrate that a core–shell structure, composed of VO2@Si, which is deposited on a thin layer of Ag, achieves the inverted optical functionality within the 1–3 µm spectral range, making it ideal as smart interfaces for radiative heat applications as high-temperature emitters. The proposed material architecture also increases the thermal stability of VO2 in addition to enhancing its optical properties in near-infrared region. The results were obtained using numerical simulations. Our results indicate that in its metallic state, the core–shell structure with metallic underlayer promotes efficient absorption in the near-infrared spectrum. On the other hand, in its insulating state dielectric resonances within the core–shell structure along with the metallic underlayer, resulting in increased reflection, offer inverse optical functionalities. Our findings present a significant step toward designing dynamic filters that can efficiently capture and respond to changing conditions in the near-infrared spectrum.