skip to main content


The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 10:00 PM ET on Friday, December 8 until 2:00 AM ET on Saturday, December 9 due to maintenance. We apologize for the inconvenience.

Search for: All records

Award ID contains: 1565822

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Abstract

    The integration of highly luminescent CsPbBr3quantum dots on nanowire waveguides has enormous potential applications in nanophotonics, optical sensing, and quantum communications. On the other hand, CsPb2Br5nanowires have also attracted a lot of attention due to their unique water stability and controversial luminescent property. Here, the growth of CsPbBr3nanocrystals on CsPb2Br5nanowires is reported first by simply immersing CsPbBr3powder into pure water, CsPbBr3−γ Xγ(X = Cl, I) nanocrystals on CsPb2Br5−γ Xγnanowires are then synthesized for tunable light sources. Systematic structure and morphology studies, including in situ monitoring, reveal that CsPbBr3powder is first converted to CsPb2Br5microplatelets in water, followed by morphological transformation from CsPb2Br5microplatelets to nanowires, which is a kinetic dissolution–recrystallization process controlled by electrolytic dissociation and supersaturation of CsPb2Br5. CsPbBr3nanocrystals are spontaneously formed on CsPb2Br5nanowires when nanowires are collected from the aqueous solution. Raman spectroscopy, combined photoluminescence, and SEM imaging confirm that the bright emission originates from CsPbBr3−γ Xγnanocrystals while CsPb2Br5−γ Xγnanowires are transparent waveguides. The intimate integration of nanoscale light sources with a nanowire waveguide is demonstrated through the observation of the wave guiding of light from nanocrystals and Fabry–Perot interference modes of the nanowire cavity.

    more » « less
  2. Abstract

    Magneto‐optical (MO) coupling incorporates photon‐induced change of magnetic polarization that can be adopted in ultrafast switching, optical isolators, mode convertors, and optical data storage components for advanced optical integrated circuits. However, integrating plasmonic, magnetic, and dielectric properties in one single material system poses challenges since one natural material can hardly possess all these functionalities. Here, co‐deposition of a three‐phase heterostructure composed of a durable conductive nitride matrix with embedded core–shell vertically aligned nanopillars, is demonstrated. The unique coupling between ferromagnetic NiO core and atomically sharp plasmonic Au shell enables strong MO activity out‐of‐plane at room temperature. Further, a template growth process is applied, which significantly enhances the ordering of the nanopillar array. The ordered nanostructure offers two schemes of spin polarization which result in stronger antisymmetry of Kerr rotation. The presented complex hybrid metamaterial platform with strong magnetic and optical anisotropies is promising for tunable and modulated all‐optical‐based nanodevices.

    more » « less
  3. Abstract

    Light coupling with patterned subwavelength hole arrays induces enhanced transmission supported by the strong surface plasmon mode. In this work, a nanostructured plasmonic framework with vertically built‐in nanohole arrays at deep‐subwavelength scale (6 nm) is demonstrated using a two‐step fabrication method. The nanohole arrays are formed first by the growth of a high‐quality two‐phase (i.e., Au–TiN) vertically aligned nanocomposite template, followed by selective wet‐etching of the metal (Au). Such a plasmonic nanohole film owns high epitaxial quality with large surface coverage and the structure can be tailored as either fully etched or half‐way etched nanoholes via careful control of the etching process. The chemically inert and plasmonic TiN plays a role in maintaining sharp hole boundary and preventing lattice distortion. Optical properties such as enhanced transmittance and anisotropic dielectric function in the visible regime are demonstrated. Numerical simulation suggests an extended surface plasmon mode and strong field enhancement at the hole edges. Two demonstrations, including the enhanced and modulated photoluminescence by surface coupling with 2D perovskite nanoplates and the refractive index sensing by infiltrating immersion liquids, suggest the great potential of such plasmonic nanohole array for reusable surface plasmon‐enhanced sensing applications.

    more » « less
  4. Abstract

    Integration of nanoscale photonic and plasmonic components on Si substrates is a critical step toward Si‐based integrated nanophotonic devices. In this work, a set of unique complex 3D metamaterials with intercalated nanolayered and nanopillar structures with tunable plasmonic and optical properties on Si substrates is designed. More specifically, the 3D metamaterials combine metal (Au) nanopillars and alternating metal‐nitride (Au‐TiN and Au‐TaN) nanolayers, epitaxially grown on Si substrates. The ultrafine Au nanopillars (d≈ 3 nm) continuously grow throughout all the nanolayers with high epitaxial quality. Novel optical properties, such as highly anisotropic optical property, high absorbance covering the entire visible spectrum regime, and hyperbolic property in the visible regime, are demonstrated. Furthermore, a waveguide based on a silicon nitride (Si3N4) ridge with a multilayer structure is successfully fabricated. The demonstration of 3D nanoscale metamaterial design integrated on Si opens up a new route toward tunable metamaterials nanostructure designs with versatile material selection for various optical components in Si integrated photonics.

    more » « less
  5. 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.

    more » « less
  6. Abstract

    Memristors with excellent scalability have the potential to revolutionize not only the field of information storage but also neuromorphic computing. Conventional metal oxides are widely used as resistive switching materials in memristors. Interface‐type memristors based on ferroelectric materials are emerging as alternatives in the development of high‐performance memory devices. A clear understanding of the switching mechanisms in this type of memristors, however, is still in its early stages. By comparing the bipolar switching in different systems, it is found that the switchable diode effect in ferroelectric memristors is controlled by polarization modulated Schottky barrier height and polarization coupled interfacial deep states trapping/detrapping. Using semiconductor theories with consideration of polarization effects, a phenomenological theory is developed to explain the current–voltage behavior at the metal/ferroelectric interface. These findings reveal the critical role of the interaction among polarization charges, interfacial defects, and Schottky interface in controlling ferroelectric resistive switching and offer the guidance to design ferroelectric memristors with enhanced performance.

    more » « less
  7. 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
  8. Multiferroic materials are an interesting functional material family combining two ferroic orderings, e.g. , ferroelectric and ferromagnetic orderings, or ferroelectric and antiferromagnetic orderings, and find various device applications, such as spintronics, multiferroic tunnel junctions, etc. Coupling multiferroic materials with plasmonic nanostructures offers great potential for optical-based switching in these devices. Here, we report a novel nanocomposite system consisting of layered Bi 1.25 AlMnO 3.25 (BAMO) as a multiferroic matrix and well dispersed plasmonic Au nanoparticles (NPs) and demonstrate that the Au nanoparticle morphology and the nanocomposite properties can be effectively tuned. Specifically, the Au particle size can be tuned from 6.82 nm to 31.59 nm and the 6.82 nm one presents the optimum ferroelectric and ferromagnetic properties and plasmonic properties. Besides the room temperature multiferroic properties, the BAMO-Au nanocomposite system presents other unique functionalities including localized surface plasmon resonance (LSPR), hyperbolicity in the visible region, and magneto-optical coupling, which can all be effectively tailored through morphology tuning. This study demonstrates the feasibility of coupling single phase multiferroic oxides with plasmonic metals for complex nanocomposite designs towards optically switchable spintronics and other memory devices. 
    more » « less
  9. Transition metal nitrides such as titanium nitride (TiN) possess exceptional mechanical-, chemical-, and thermal-stability and have been utilized in a wide variety of applications ranging from super-hard, corrosion-resistive, and decorative coatings to nanoscale diffusion barriers in semiconductor devices. Despite the ongoing interest in these robust materials, there have been limited reports focused on engineering high-aspect ratio TiN-based nanocomposites with anisotropic magnetic and optical properties. To this end, we explored TiN–Fe thin films with self-assembled vertical structures integrated on Si substrates. We showed that the key physical properties of the individual components (e.g., ferromagnetism from Fe) are preserved, that vertical nanostructures promote anisotropic behavior, and interactions between TiN and Fe enable a special magneto-optical response. This TiN–Fe nanocomposite system presents a new group of complex multifunctional hybrid materials that can be integrated on Si for future Si-based memory, optical, and biocompatible devices. 
    more » « less