ZnO-Au _x Cu_{1- x} Alloy and ZnO-Au _x Al_{1- x} Alloy Vertically Aligned Nanocomposites for Low-Loss Plasmonic Metamaterials

Hyperbolic metamaterials are a class of materials exhibiting anisotropic dielectric function owing to the morphology of the nanostructures. In these structures, one direction behaves as a metal, and the orthogonal direction behaves as a dielectric material. Applications include subdiffraction imaging and hyperlenses. However, key limiting factors include energy losses of noble metals and challenging fabrication methods. In this work, self-assembled plasmonic metamaterials consisting of anisotropic nanoalloy pillars embedded into the ZnO matrix are developed using a seed-layer approach. Alloys of Au_xAl_1-x or Au_xCu_1-x are explored due to their lower losses and higher stability. Optical and microstructural properties were explored. The ZnO-Au_xCu_1-x system demonstrated excellent epitaxial quality and optical properties compared with the ZnO-Au_xAl_1-x system. Both nanocomposite systems demonstrate plasmonic resonance, hyperbolic dispersion, low losses, and epsilon-near-zero permittivity, making them promising candidates towards direct photonic integration.