Actively Tunable Metasurfaces via Plasmonic Nanogap Cavities with Sub-10-nm VO(2) Films

[Image: see text] Actively tunable optical materials integrated with engineered subwavelength structures could enable novel optoelectronic devices, including reconfigurable light sources and tunable on-chip spectral filters. The phase-change material vanadium dioxide (VO(2)) provides a promising solid-state solution for dynamic tuning; however, previous demonstrations have been limited to thicker and often rough VO(2) films or require a lattice-matched substrate for growth. Here, sub-10-nm-thick VO(2) films are realized by atomic layer deposition (ALD) and integrated with plasmonic nanogap cavities to demonstrate tunable, spectrally selective absorption across 1200 nm in the near-infrared (NIR). Upon inducing the phase transition via heating, the absorption resonance is blue-shifted by as much as 60 nm. This process is reversible upon cooling and repeatable over more than ten temperature cycles. Dynamic, ultrathin VO(2) films deposited by ALD, as demonstrated here, open up new potential architectures and applications where VO(2) can be utilized to provide reconfigurability including three-dimensional, flexible and large-area structures.