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

Area of Science:

• Optoelectronics and Nanophotonics
• Materials Science and Engineering

Background:

• Actively tunable optical materials are crucial for advanced optoelectronic devices like reconfigurable light sources and spectral filters.
• Vanadium dioxide (VO2) is a phase-change material offering solid-state dynamic tuning, but previous applications were limited by film thickness and substrate requirements.

Purpose of the Study:

• To demonstrate tunable, spectrally selective absorption in the near-infrared (NIR) using ultrathin VO2 films integrated with plasmonic nanogap cavities.
• To overcome limitations of previous VO2 demonstrations by utilizing atomic layer deposition (ALD) for sub-10-nm-thick films.

Main Methods:

• Fabrication of sub-10-nm-thick VO2 films using atomic layer deposition (ALD).
• Integration of these ultrathin VO2 films with plasmonic nanogap cavities.
• Characterization of spectral absorption tuning via the VO2 phase transition induced by heating.

Main Results:

• Achieved spectrally selective absorption tuning across 1200 nm in the NIR.
• Demonstrated a reversible blue-shift of the absorption resonance by up to 60 nm upon inducing the VO2 phase transition.
• Confirmed repeatability of the tuning process over more than ten temperature cycles.

Conclusions:

• Ultrathin VO2 films deposited by ALD are effective for creating tunable optical absorption in plasmonic nanogaps.
• This approach enables novel architectures for reconfigurable optoelectronic devices, including 3D, flexible, and large-area applications.
• The demonstrated dynamic tuning capabilities of ALD-grown VO2 open new avenues for advanced optical material integration.