Tunable Optical Properties in Self‐Assembled Oxide‐Metal Hybrid Thin Films via Au‐Phase Geometry Control: From Nanopillars to Nanodisks

Abstract Plasmonic oxide‐metal hybrid nanostructures exhibit unprecedented optical properties because of the nanoscale interactions between the oxide and metal components. Precise control of the geometry and arrangement of optical building blocks is key to tailoring system properties toward various nanophotonic applications. Herein, self‐assembled BaTiO₃‐Au vertically aligned nanocomposite thin films with a series of thicknesses are fabricated using a one‐step pulsed laser deposition technique. By reducing the film thickness, the geometry of Au phase is effectively tailored from nanopillars to nanodisks, with the aspect ratio (height/width) varied from ≈4.0 to ≈1.0. The experimental optical spectra and numerical simulation results demonstrate that localized surface plasmon resonance and hyperbolic dispersion wavelength can be effectively tuned in the visible to near‐infrared regime by varying the film thickness due to the change of Au aspect ratio and free electron density. This study demonstrates a feasible approach in tuning the optical responses in hybrid oxide‐metal nanostructures, and opens up enormous possibilities in design and fabrication of novel optical components toward all optical integrated devices.