Jijie Huang, Bin Zhang, Danny Hermawan, Alfredo Sanjuan, Benson Kunhung Tsai, Jialong Huang, R Edwin Garcı́a, Haiyan Wang “Complex Oxide‐Metal Hybrid Metamaterials with Integrated Magnetic and Plasmonic Non‐noble Metal Nanostructures.” Advanced Functional Materials. 35 (30), 2500741, 2025. https://doi.org/10.1002/adfm.202500741

Abstract

Vertically aligned nanocomposite (VAN) thin films offer exceptional physical properties through diverse material combinations, providing a robust platform for designing complex nanocomposites with tailored performance. Considering materials compatibility issues, most of oxide-metal VANs have focused on noble metals as the secondary phase in the oxide matrix. Here, an oxide-metal hybrid metamaterials in the VAN form has been designed which combines ferroelectric BaTiO₃ (BTO) with two immiscible non-noble metal elements of Co and Cu, resulting in a three-phase BTO-Co-Cu (BTO-CC) VAN film. This film exhibits a characteristic nanopillar-in-matrix nanostructure with three distinct types of nanopillar morphologies, i.e., Co-rich cylindrical nanopillars, Cu-Co-nanolaminated Co rectangular nanopillars and Co-Cu-core–shell cylindrical nanopillars. Phase field modeling indicates the constructed structure is resulted from the interplay between thermochemical, chemomechanical, and interfacial energy driving forces. The strong structural anisotropy leads to anisotropic optical and magnetic properties, presenting potential as hyperbolic metamaterial (HMM) with transverse-positive dispersion in the near-infrared region. The inclusion of non-noble Cu nanostructure induces surface plasmon resonance (SPR) in the visible region. Additionally, ferroelectric properties have been demonstrated in a BTO/BTO-CC bilayer, confirming room-temperature multiferroicity in the film. The complex three-phase VANs offer a novel platform for exploring electro-magneto-optical coupling along vertical interfaces toward future integrated devices.