Actively Tunable Metasurfaces via Plasmonic Nanogap Cavities withSub-10-nm VO2 Films

Actively tunable optical materials integrated with engineered subwavelength structures could enable novel optoelectronic devices,including reconfigurable light sources and tunable on-chip spectralfilters.The phase-change material vanadium dioxide (VO2) provides a promisingsolid-state solution for dynamic tuning; however, previous demonstrationshave been limited to thicker and often rough VO2films or require a lattice-matched substrate for growth. Here, sub-10-nm-thick VO2films arerealized by atomic layer deposition (ALD) and integrated with plasmonicnanogap cavities to demonstrate tunable, spectrally selective absorptionacross 1200 nm in the near-infrared (NIR). Upon inducing the phasetransition via heating, the absorption resonance is blue-shifted by as muchas 60 nm. This process is reversible upon cooling and repeatable over more than ten temperature cycles. Dynamic, ultrathin VO2films deposited by ALD, as demonstrated here, open up new potential architectures and applications where VO2can be utilized toprovide reconfigurability including three-dimensional, flexible and large-area structures