Metamaterials made of nanoscale inclusions or artificial unit cells exhibit exotic optical properties that do not exist in natural materials. Promising applications, such as super-resolution imaging, cloaking, hyperbolic propagation, and ultrafast phase velocities have been demonstrated based on mostly micrometer-scale metamaterials and few nanoscale metamaterials. To date, most metamaterials are created using costly and tedious fabrication techniques with limited paths toward reliable large-scale fabrication. In this work, we demonstrate the one-step direct growth of self-assembled epitaxial metal-oxide nanocomposites as a drastically different approach to fabricating large-area nanostructured metamaterials. Using pulsed laser deposition, we fabricated nanocomposite films with vertically aligned gold (Au) nanopillars (∼20 nm in diameter) embedded in various oxide matrices with high epitaxial quality. Strong, broad absorption features in the measured absorbance spectrum are clear signatures of plasmon resonances of Au nanopillars. By tuning their densities on selected substrates, anisotropic optical properties are demonstrated via angular dependent and polarization resolved reflectivity measurements and reproduced by full-wave simulations and effective medium theory. Our model predicts exotic properties, such as zero permittivity responses and topological transitions. Our studies suggest that these self-assembled metal-oxide nanostructures provide an exciting new material platform to control and enhance optical response at nanometer scales.

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Phase transitions, crystal structures and chemical reactions of β-HMX under extreme conditions were described systematically.

Integrating oxide thin films on flexible substrates is a critical step toward future applications of multifunctional oxides for flexible electronics and spintronic devices. As a demonstration, multifunctional La0.67Sr0.33MnO3 (LSMO) thin films have been deposited on flexible mica substrates. The crystallinity and microstructure of the films have been characterized to show the good epitaxial quality of the films. The LSMO thin films on mica present excellent ferromagnetic and magnetoresistance properties (such as saturation magnetization M s of 125–400 emu/cm3 at 10 K and a high MR value of ∼45% at 5 K under 1 T for the 50 mTorr deposited sample), which is even better than the ones on conventional rigid single-crystal oxide substrates. More interestingly, no deterioration of the properties is observed under mechanically bending condition, which demonstrates the good mechanical stretchability and property stability of the LSMO thin films on mica. The demonstration of functional oxides integrated on flexible mica substrates paves a route toward future flexible spintronics and electronics.

A B S T R A C TLead-free perovskite oxide thin films prepared by alloying of titanates and materials with lower melting points are shown to have enhanced ferroelectric and dielectric properties. BaTiO 3 (or SrTiO 3 ) with 25% addition of BiFeO 3 has much improved crystalline perfection because of the lower melting point of the BiFeO 3 giving enhanced growth kinetics. The maximum dielectric peak temperature of BaTiO 3 is increased by~200°C and leakage currents are reduced by up to a factor of~100. The loss tangent reduces up to 300°C, with a factor of > 14 reduction at room temperature. The dielectric breakdown strength is higher by a factor of~3 (> 2200 kV cm ) and from room temperature up to 500°C the dielectric constant is > 1000. Also, a low variation of dielectric constant of~9% from room temperature to 330°C is obtained, compared to~110% for BaTiO 3 . The maximum polarization (P max ) is double that of BaTiO 3 , at 125.3 μC cm −2. The film has high energy storage densities of > 52 J cm −3 at 2050 kV cm −1 , matching Pb-based ferroelectric films. The strongly improved performance is important for applications in energy storage and in high temperature (up to 300°C) capacitors as well as wider application in other electronic and energy technologies.