Self‐Assembled Ordered Three‐Phase Au–BaTiO₃–ZnO Vertically Aligned Nanocomposites Achieved by a Templating Method

Abstract

spintronics, [2] multiferroics, [3] and quantum systems. [4] Several two-phase nanocomposite systems, exhibiting multilayer or nanowire morphology, have been demonstrated for achieving enhanced physical properties, including ferroelectricity, [5] ferromagnetism, [6] magnetoresistance, [7] and exotic optical properties such as optical magnetism, [8] negative refraction, [9] and hyperbolic dispersion. [10] For example, hyperbolic metamaterials with ordered and anisotropic metal-dielectric nanocomposite designs support the propagation of high wavevectors. [11] Since very few hyperbolic materials exist naturally, this artificially engineered nanocomposite approach provides a multifunctional platform to realize such materials with applications in subdiffraction imaging, [12] sensing, [13] waveguiding, [14] and also offers an opportunity to achieve coupled electric, magnetic, and optical responses. However, due to the availability of a limited range of structures in terms of crystallinity and morphology, a greater design flexibility and a structural complexity along with versatile growth techniques are needed for developing next generation integrated photonic and electronic devices. This can be achieved by incorporating a third phase through the three-phase nanocomposite designs by judicious selection of materials and functionalities.Besides material selection, the spatial ordering of the phases has great impacts on the overall functionalities of nanocomposite materials. Previous efforts to grow ordered ceramicmetal nanocomposites have focused on applying patterning techniques such as anodized alumina oxide (AAO) templates, [15] e-beam lithography, [16] focused ion beam (FIB), [17] and substrate nanotemplate. [18] In contrast, a self-assembly approach for fabricating such ordered oxide-metal nanocomposites is costeffective and overcomes the resolution limitation and complex fabrication steps. Controlled synthesis of such self-assembled complex hybrid nanostructures with desired ordering and epitaxial quality remains a challenge. Specifically, large difference in surface energy, growth kinetics, and high tendency of oxidation and interdiffusion between vastly different phases remains as a major challenge and imposes difficulties in ordering control. Despite the recent success of the self-assembled epitaxial Complex multiphase nanocomposite designs present enormous opportunities for developing next-generation integrated photonic and electronic devices. Here, a unique three-phase nanostructure combining a ferroelectric BaTiO 3 , a wide-bandgap semiconductor of ZnO, and a plasmonic metal of Au toward multifunctionalities is demonstrated. By a novel two-step templated growth, a highly ordered Au-BaTiO 3 -ZnO nanocomposite in a unique "nanoman"-like form, i.e., self-assembled ZnO nanopillars and Au nanopillars in a BaTiO 3 matrix, is realized, and is very different from the random three-phase ones with randomly arranged Au nanoparticles and ZnO nanopillars in the BaTiO 3 matrix. The ordered three-phase "nanoman"-like structu...

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

“…As the pink arrow shows, ENZ resonance experiences a blue‐shift as the film thickness reduces from 70 to 6 nm, implying more negative dielectric constant and metallic behavior in the thinner films. The ENZ resonance wavelengths are consistent with previous experimental and theoretical studies . The real permittivity ε′(including and ) of 70 nm BTO‐Au film is plotted in Figure c.…”

“…Alternatively, a novel self‐assembly approach via a one‐step growth of high‐quality epitaxial oxide‐metal hybrid systems has been recently demonstrated with integrated optical, magnetic, and piezoelectric properties that are hard to achieve in single phase materials . Besides, by a novel two‐step templated growth via pulsed laser deposition (PLD) technique, a highly ordered Au‐BaTiO 3 ‐ZnO nanocomposite structure has been fabricated showing coupled multifunctionalities including optical and ferroelectric properties …”

Integration of highly anisotropic multiferroic BaTiO3–Fe nanocomposite thin films on Si towards device applications

“…40,41 Fascinating optical properties in pure BTO and BTO nanocomposite thin lms have previously been reported, including large Pockel's coefficients and hyperbolic dispersion. 27,28,34,42 Since the microstructural characterization and magnetic properties revealed highly anisotropic features arising from the Fe nanopillars, the optical properties of the BTO-Fe thin lms integrated on Si were also investigated in this study. Angular-dependent reectance (R%) measurements were performed at various incident angles (e.g., 30 , 40 , 50 , 60 and 70 ) using a spectroscopic ellipsometer.…”

Barium Titanate Nanostructures and Thin Films for Photonics

“…[205] By a novel two-step templated growth, a highly ordered Au-BaTiO 3 -ZnO nanocomposite of self-assembled ZnO nanopillars and Au nanopillars in a BaTiO 3 matrix, was realized. [206] They introduced a design of an epitaxial ordered trilayer film (Au-BaTiO 3 -ZnO), by employing the vaporliquid-solid (VLS) mechanism, in combination with pulsed laser deposition, the three-phase ordering was realized via a combined self-assembly and templating method. BaTiO 3 and ZnO allow the possibility of growing vertically aligned nanocomposite BaTiO 3 -ZnO structure because of their phase immiscibility and chemical compatibility.…”