Metamaterials have gained great research interest in recent years owing to their potential for property tunability, multifunctionality, and property coupling. As a new group of self‐assembled thin films, vertically aligned nanocomposite (VAN)‐based hybrid metamaterials have been demonstrated with significant anisotropic physical properties and a broad range of property tailorability, such as optical anisotropy, magnetic anisotropy, hyperbolic dispersion, and enhanced second harmonic generation properties. Herein, self‐assembled ZrO2‐Co nanocomposite films, with high epitaxial quality and ultra‐fine vertically aligned Co nanopillars (with an average diameter of ≈2 nm) embedded in a ZrO2matrix, are fabricated using a pulsed laser deposition (PLD) method. The Co pillar density can be effectively tuned by varying the Co concentration in the target, which results in tunable optical properties and magnetic properties. Specifically, a high saturation magnetization of 100 emu cm−3, strong out‐of‐plane magnetic anisotropy and tailorable magnetization properties are achieved via tuning the Co nanopillar density. Coupled with hyperbolic dispersion of dielectric constant from 950 to 1500 nm in wavelength, plasmonic Co metal nanopillars, and the unique dielectric ZrO2matrix, this new nanoscale hybrid metamaterial shows great potential for future integrated optical and magnetic device designs.
Self-assembled vertically aligned Ni nanopillars in CeO 2 with anisotropic magnetic and transport properties for energy applications
Self-assembled vertically aligned metal–oxide (Ni–CeO 2 ) nanocomposite thin films with novel multifunctionalities have been successfully deposited by a one-step growth method. The novel nanocomposite structures presents high-density Ni-nanopillars vertically aligned in a CeO 2 matrix. Strong and anisotropic magnetic properties have been demonstrated, with a saturation magnetization ( M s ) of ∼175 emu cm −3 and ∼135 emu cm −3 for out-of-plane and in-plane directions, respectively. Such unique vertically aligned ferromagnetic Ni nanopillars in the CeO 2 matrix have been successfully incorporated in high temperature superconductor YBa 2 Cu 3 O 7 (YBCO) coated conductors as effective magnetic flux pinning centers. The highly anisotropic nanostructures with high density vertical interfaces between the Ni nanopillars and CeO 2 matrix also promote the mixed electrical and ionic conductivities out-of-plane and thus demonstrate great potential as nanocomposite anode materials for solid oxide fuel cells and other potential applications requiring anisotropic ionic transport properties.
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- Award ID(s):
- 1809520
- NSF-PAR ID:
- 10092850
- Date Published:
- Journal Name:
- Nanoscale
- Volume:
- 10
- Issue:
- 36
- ISSN:
- 2040-3364
- Page Range / eLocation ID:
- 17182 to 17188
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract -
Metamaterials present great potential in the applications of solar cells and nanophotonics, such as super lenses and other meta devices, owing to their superior optical properties. In particular, hyperbolic metamaterials (HMMs) with exceptional optical anisotropy offer improved manipulation of light–matter interactions as well as a divergence in the density of states and thus show enhanced performances in related fields. Recently, the emerging field of oxide–metal vertically aligned nanocomposites (VANs) suggests a new approach to realize HMMs with flexible microstructural modulations. In this work, a new oxide–metal metamaterial system, CeO 2 –Au, has been demonstrated with variable Au phase morphologies from nanoparticle-in-matrix (PIM), nanoantenna-in-matrix, to VAN. The effective morphology tuning through deposition background pressure, and the corresponding highly tunable optical performance of three distinctive morphologies, were systematically explored and analyzed. A hyperbolic dispersion at high wavelength has been confirmed in the nano-antenna CeO 2 –Au thin film, proving this system as a promising candidate for HMM applications. More interestingly, a new and abnormal in-plane epitaxy of Au nanopillars following the large mismatched CeO 2 matrix instead of the well-matched SrTiO 3 substrate, was discovered. Additionally, the tilting angle of Au nanopillars, α , has been found to be a quantitative measure of the balance between kinetics and thermodynamics during the depositions of VANs. All these findings provide valuable information in the understanding of the VAN formation mechanisms and related morphology tuning.more » « less
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null (Ed.)Integration of highly anisotropic multiferroic thin films on silicon substrates is a critical step towards low-cost devices, especially high-speed and low-power consumption memories. In this work, an oxide–metal vertically aligned nanocomposite (VAN) platform has been used to successfully demonstrate self-assembled multiferroic BaTiO 3 –Fe (BTO–Fe) nanocomposite films with high structural anisotropy on Si substrates. The effects of various buffer layers on the crystallinity, microstructure, and physical properties of the BTO–Fe films have been explored. With an appropriate buffer layer design, e.g. SrTiO 3 /TiN bilayer buffer, the epitaxial quality of the BTO matrix and the anisotropy of the Fe nanopillars can be improved greatly, which in turn enhances the physical properties, including the ferromagnetic, ferroelectric, and optical response of the BTO–Fe thin films. This unique combination of properties integrated on Si offers a promising approach in the design of multifunctional nanocomposites for Si-based memories and optical devices.more » « less
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Oxide-metal-based hybrid materials have gained great research interest in recent years owing to their potential for multifunctionality, property coupling, and tunability. Specifically, oxide-metal hybrid materials in a vertically aligned nanocomposite (VAN) form could produce pronounced anisotropic physical properties, e.g. , hyperbolic optical properties. Herein, self-assembled HfO 2 -Au nanocomposites with ultra-fine vertically aligned Au nanopillars (as fine as 3 nm in diameter) embedded in a HfO 2 matrix were fabricated using a one-step self-assembly process. The film crystallinity and pillar uniformity can be obviously improved by adding an ultra-thin TiN-Au buffer layer during the growth. The HfO 2 -Au hybrid VAN films show an obvious plasmonic resonance at 480 nm, which is much lower than the typical plasmonic resonance wavelength of Au nanostructures, and is attributed to the well-aligned ultra-fine Au nanopillars. Coupled with the broad hyperbolic dispersion ranging from 1050 nm to 1800 nm in wavelength, and unique dielectric HfO 2 , this nanoscale hybrid plasmonic metamaterial presents strong potential for the design of future integrated optical and electronic switching devices.more » « less
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Abstract To investigate the role of interlayers on the growth, microstructure, and physical properties of 3D nanocomposite frameworks, a set of novel 3D vertically aligned nanocomposite (VAN) frameworks are assembled by a relatively thin interlayer (M) sandwiched by two consecutively grown La0.7Sr0.3MnO3(LSMO)‐ZnO VANs layers. ZnO nanopillars from the two VAN layers and the interlayer (M) create a heterogeneous 3D frame embedded in the LSMO matrix. The interlayer (M) includes yttria‐stabilized zirconia (YSZ), CeO2, SrTiO3, BaTiO3, and MgO with in‐plane matching distances increasing from ≈3.63 to ≈4.21 Å, and expected in‐plane strains ranging from tensile (≈8.81% on YSZ interlayer) to compressive (≈–6.23% on MgO interlayer). The metal‐insulator transition temperature increases from ≈133 K (M = YSZ) to ≈252 K (M = MgO), and the low‐field magnetoresistance peak value is tuned from ≈36.7% to ≈20.8%. The 3D heterogeneous frames empower excellent tunable magnetotransport properties and promising potentials for microstructure‐enabled applications.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c8nr05532g
