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Developing reliable and tunable metamaterials is fundamental to next-generation optical-based nanodevices and computing schemes. In this review, an overview of recent progress made with a unique group of ceramic-based functional nanocomposites, i.e., vertically aligned nanocomposites (VANs), is presented, with the focus on the tunable anisotropic optical properties. Using a self-assembling bottom-up deposition method, the as-grown VANs present great promise in terms of structural flexibility and property tunability. Such broad tunability of functionalities is achieved through VAN designs, material selection, growth control, and strain coupling. The as-grown multi-phase VAN films also present enormous advantages, including wafer scale integration, epitaxial quality, sharp atomic interface, as well as designable materials and geometries. This review also covers the research directions with practical device potentials, such as multiplex sensing, high-temperature plasmonics, magneto-optical switching, as well as photonic circuits.

Two-dimensional (2D) materials with robust ferromagnetic behavior have attracted great interest because of their potential applications in next-generation nanoelectronic devices. Aside from graphene and transition metal dichalcogenides, Bi-based layered oxide materials are a group of prospective candidates due to their superior room-temperature multiferroic response. Here, an ultrathin Bi 3 Fe 2 Mn 2 O 10+ δ layered supercell (BFMO322 LS) structure was deposited on an LaAlO 3 (LAO) (001) substrate using pulsed laser deposition. Microstructural analysis suggests that a layered supercell (LS) structure consisting of two-layer-thick Bi–O slabs and two-layer-thick Mn/Fe–O octahedra slabs was formed on top of the pseudo-perovskite interlayer (IL). A robust saturation magnetization value of 129 and 96 emu cm −3 is achieved in a 12.3 nm thick film in the in-plane (IP) and out-of-plane (OP) directions, respectively. The ferromagnetism, dielectric permittivity, and optical bandgap of the ultrathin BFMO films can be effectively tuned by thickness and morphology variation. In addition, the anisotropy of all ultrathin BFMO films switches from OP dominating to IP dominating as the thickness increases. This study demonstrates the ultrathin BFMO film with tunable multifunctionalities as a promising candidate for novel integrated spintronic devices.

Two-phase nanocomposites have gained significant research interest because of their multifunctionalities, tunable geometries and potential device applications. Different from the previously demonstrated oxide–oxide 2-phase nanocomposites, coupling nitrides with metals shows high potential for building alternative hybrid plasmonic metamaterials towards chemical sensing, tunable plasmonics, and nonlinear optics. Unique advantages, including distinct atomic interface, excellent crystalline quality, large-scale surface coverage and durable solid-state platform, address the high demand for new hybrid metamaterial designs for versatile optical material needs. This review summarizes the recent progress on nitride–metal nanocomposites, specifically targeting bottom-up self-assembled nanocomposite thin films. Various morphologies including vertically aligned nanocomposites (VANs), self-organized nanoinclusions, and nanoholes fabricated by additional chemical treatments are introduced. Starting from thin film nucleation and growth, the prerequisites of successful strain coupling and the underlying growth mechanisms are discussed. These findings facilitate a better control of tunable nanostructures and optical functionalities. Future research directions are proposed, including morphological control of the secondary phase to enhance its homogeneity, coupling nitrides with magnetic phase for the magneto-optical effect and growing all-ceramic nanocomposites to extend functionalities and anisotropy.