A mathematical evidence-in a statistically significant sense-of a geometric scenario leading to criticality of the Navier-Stokes problem is presented. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752170]
We investigate electron transport properties in large-area, single-layer graphene embedded in dielectric media, using free-space terahertz (THz) imaging and time-domain spectroscopy. Sandwiched between a thin polymethyl methacrylate (PMMA) layer and a Si substrate, graphene layers of different growth recipes exhibit distinctive spatial inhomogeneity of sheet conductivity. The non-contacting, non-destructive THz...
We demonstrate time-resolved terahertz transmission ellipsometry of vertically aligned multi-walled carbon nanotubes. The angle-resolved transmission measurements reveal anisotropic characteristics of the terahertz electrodynamics in multi-walled carbon nanotubes. The anisotropy is, however, unexpectedly weak: the ratio of the tube-axis conductivity to the transverse conductivity, sigma[subscript z]/sigma[subscript xy] [similar or equal to]...
The growth of YMn₀.₃₅In₀.₆₅O₃ thin films and their optical and magnetic behavior are reported. The YMn₀.₃₅In₀.₆₅O₃ thin film grows along the (0001) orientation with hexagonal structure similar to YMnO₃ on c-plane sapphire. The film shows paramagnetic behavior in the temperature range measured. The film exhibits a blue color due to...
Metal-insulator-insulator-metal tunnel diodes with dissimilar work function electrodes and nanolaminate Al₂O₃-Ta₂O₅ bilayer tunnel barriers deposited by atomic layer deposition are investigated. This combination of high and low electron affinity insulators, each with different dominant conduction mechanisms (tunneling and Frenkel-Poole emission), results in improved low voltage asymmetry and non-linearity of current...
We demonstrate a four-channel on-chip true-time-delay module based on a photonic crystal waveguide array. Using the photonic crystal taper to minimize the coupling loss, the delay lines with 1-3 mm long photonic crystal waveguides can operate up to a group index n(g) similar to ~23 without significant loss. The large...
The piezoelectric fatigue behavior of Pb-free ceramics based on solid solutions of Bi(Zn₀.₅Ti₀.₅)O₃-(Bi₀.5K₀.₅)TiO₃-(Bi₀.₅Na₀.₅)TiO₃ was characterized at 50 kV/cm after 10⁶ bipolar cycles. Ferroelectric compositions containing 2.5% Bi(Zn₀.₅Ti₀.₅)O₃ exhibited only minor losses in maximum strain (~10%). In compositions with 5% Bi(Zn₀.₅Ti₀.₅)O₃ that exhibit large electric field-induced strains, the electromechanical strain actually...
Magnetic nanocomposites, composed of magnetic nanoparticles in an insulating matrix, can have
properties not achievable in bulk, single-phase materials. This work reports on ferromagnetic
resonance (FMR) measurements as a tool to investigate the internal magnetic field in nanocomposite
samples of varying particle packing fractions. The ferromagnetic resonance frequency changes with...
We demonstrate a surface enhanced Raman scattering (SERS) substrate by integrating plasmonic-active SiO₂ nanotubes into Si₃N₄ gratings. First, the dielectric grating that is working under guided mode resonance (GMR) provides enhanced electric field for localized surface plasmon polaritons on the surface of metallic nanoparticles. Second, we use SiO₂ nanotubes with...
SnS is a potential earth-abundant photovoltaic (PV) material. Employing both theory and experiment to assess the PV relevant properties of SnS, we clarify on whether SnS has an indirect or direct band gap and what is the minority carrier effective mass as a function of the film orientation. SnS has...
We develop a classical density functional for water which combines the White Bear fundamental-measure theory (FMT) functional for the hard sphere fluid with attractive interactions based on the statistical associating fluid theory variable range (SAFT-VR). This functional reproduces the properties of water at both long and short length scales over...
Increase in energy demand has led towards considering lignocellulosic feedstocks as potential for ethanol production. Aim of this study was to estimate the potential of grass straws from conservation reserve program (CRP) lands as feedstocks for ethanol production. The CRP was initiated to ensure reduction in soil erosion with a...
Solid solutions ceramics of the Bi(Zn0.5Ti0.5)O-3-(Bi0.5K0.5)TiO3-(Bi0.5Na0.5)TiO3 ternary system for <20 mol. % BZT were created and confirmed to be single phase using x-ray diffraction. The dielectric dispersion showed decreasing T-max of the dielectric spectrum with a broadening of the transition with increasing BZT content. At 2.5BZT-40BKT-57.5BNT, a secondary transition commonly...
This article was originally published online and in print with an incorrect version of Fig. 1. AIP apologizes for this error. All online versions of the article have been corrected.
The defect mechanisms that underpin the high energy density dielectric 0.8BaTiO₃–0.2Bi(Zn₁/₂Ti₁/₂) O₃
were investigated. Characterization of the nominally stoichiometric composition revealed the
presence of a Ti³⁺-related defect center, which is correlated with lower resistivities and an
electrically heterogeneous microstructure. In compositions with 2 mol. % Ba-deficiency, a barium
vacancy-oxygen vacancy...
Full Text:
online 28 September 2012)
[http://dx.doi.org/10.1063/1.4757256]
This article was originally published
Future quantum technologies will require high-efficiency, on-demand sources of entangled photons. A possible route to building such light sources employs two-dimensional (2D) semiconductors interfaced with a source of Cooper pairs. To investigate the possibility of such devices, we are testing methods to make high transparency n-type contacts, p-type contacts, and...
Passively generated lateral motion of fluid during pool boiling on asymmetrically textured mesoscale structures is discussed in this Letter. The surface texture is in the form of 30°–60° mm-scale ratchets with re-entrant cavities located on the 30° face. High speed visualization of growing bubbles from cavities indicates growth and departure...
The energy barrier heights between two recently reported Ta-based amorphous metals (TaWSi and TaNiSi), TaN, and atomic layer deposited Al2O3 and HfO2 insulators are measured in metal/insulator/metal (MIM) structures with Au top electrodes using internal photoemission (IPE) spectroscopy. For Al2O3, the Ta-based metal barrier heights, phi(Bn), increase with increasing metal...
A novel patterning technique that creates magnetization patterns in a continuous magnetostrictive
film with surface acoustic waves is demonstrated. Patterns of 10 μm wide stripes of alternating
magnetization and a 3 μm dot of reversed magnetization are written using standing and focusing
acoustic waves, respectively. The magnetization pattern is size-tunable,...
3-D printing processes, which use drop-on-demand inkjet printheads, have great potential in
designing and prototyping magnetic materials. Unlike conventional deposition and lithography,
magnetic particles in the printing ink can be aligned by an external magnetic field to achieve both
high permeability and low hysteresis losses, enabling prototyping and development of...
A method for measuring the magnetostriction of thin films using a vibrating sample
magnetometer is described. We describe the design of a custom sample holder to apply an
adjustable bending stress to the sample during measurement and observe the resulting change in
the M-H loop.
We compare characteristics of electron impact ionization (EI) and multiphoton ionization (MPI) of doped super fluid helium droplets using the same droplet source. Selected dopant ion fragments from the two ionization schemes demonstrate different dependence on the doping pressure, which could be attributed to the different ionization mechanisms. While EI...
We investigated the thermal stability of a new ternary amorphous metal thin film, Ta₂.₄Ni₂.₂Si, and assessed its suitability as a Cu diffusion barrier for semiconductor device applications. Transmission electron microscopy was coupled with atom probe tomography to provide a detailed understanding of the atomic-scale evolution of both structure and composition...
Using in-situ synchrotron X-ray scattering, we show that the structural evolution of various bulk metallic glass-forming liquids can be quantitatively connected to their viscosity behavior in the supercooled liquid near T[subscript g]. The structural signature of fragility is identified as the temperature dependence of local dilatation on distinct key atomic...
We examined sub-nanosecond time-scale charge carrier dynamics in crystalline films of a functionalized anthradithiophene (ADT) donor (D) with three different acceptor (A) molecules. A four-fold enhancement in ultrafast charge carrier separation efficiency was observed in D/A blends with a fullerene acceptor added at 7–10 wt. % concentrations, whereas a gradual...
The kinetics of laser-induced, liquid-mediated crystallization of amorphousGe thin films were studied using multi-frame dynamic transmission electron microscopy (DTEM), a nanosecond-scale photo-emission transmission electron microscopy technique. In these experiments, high temperature gradients are established in thin amorphousGe films with a 12-ns laser pulse with a Gaussian spatial profile. The hottest...
Full Text:
:10.1063/1.4938751
10.1063/1.4938751
American Institute of Physics
Version of Record
http
The need for miniaturization without compromising cost and performance continues to motivate research in advanced capacitor devices. In this report, multilayer ceramic capacitors based on relaxor BaTiO₃-Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) were fabricated and characterized. In bulk ceramic embodiments, BT-BZT has been shown to exhibit relative permittivities greater than 1000, high resistivities (ρ > 1...
Ferromagnetic resonance (FMR) characterization, using a vector network analyzer (VNA), is widely used to determine anisotropy, g-factor, and Gilbert damping parameter of magnetic thin films, but results are typically reported without calculation of the measurement accuracy. We present a method of processing VNA-FMR measurements to determine both the value and...
We show that the transmission of a terahertz (THz) pulse through single-layer graphene is strongly
nonlinear. As the peak electric field of the THz pulse exceeds 50 kV/cm, the graphene becomes
increasingly transparent to the THz radiation. When field strength reaches 800 kV/cm, the increased
transparency corresponds to a two-fold...
We present a modification to our recently published statistical associating fluid theory-based classical
density functional theory for water. We have recently developed and tested a functional for the
averaged radial distribution function at contact of the hard-sphere fluid that is dramatically more accurate
at interfaces than earlier approximations. We now...
We demonstrate active control of plasmonic bandgap on a metallic photonic crystal slab using thermo-optic effects. The Au grating, which is milled by focused-ion beam on a glass substrate, is designed to exhibit an extraordinary optical transmission and a sharp transitional edge for high modulation efficiency. Only a moderate refractive...
We demonstrate a versatile and efficient setup to perform femtosecond stimulated Raman spectroscopy (FSRS). Technical innovations are implemented to achieve the wavelength tunability for both the picosecond narrowband Raman pump pulse and femtosecond broadband Raman probe pulse. Using a simplified one-grating scheme in a home-built second harmonic bandwidth compressor followed...
Emergence of a terawatt scalable photovoltaic (PV) thin film technology is currently impeded by
the limited supply of relatively rare elements like In or Te, which has spurred active research in
recent years on earth-abundant PV materials. Instead of searching for alternative PV materials,
we approach the problem here by...
All-optical switching has myriad applications in optoelectronics, optical communications, and
quantum information technology. To achieve ultrafast optical switching in a compact yet versatile
setup, we demonstrate distinct sets of two-dimensional (2D) broadband up-converted multicolor
arrays (BUMAs) in a thin type-I β-barium-borate crystal with two noncollinear near-IR
femtosecond pulses at various...
The role of back channel surface chemistry on amorphous zinc tin oxide (ZTO) bottom gate thin film transistors (TFTs) has been characterized by positive bias-stress measurements and x-ray photoelectron spectroscopy. Positive bias-stress turn-on voltage shifts for ZTO-TFTs were significantly reduced by passivation of back channel surfaces with self-assembled monolayers of...
Poly-3-hydroxybutyrate (PHB) is a renewable, biodegradable biopolymer that has
shown great promise to offset the use of hydrocarbon-derived plastics. The genes
encoding the bacterial PHB production pathway have been engineered into several
higher order plant species providing an opportunity to produce PHB as a
co-product on an industrial, agricultural scale....
The diffusion behavior of arsenic (As) and gallium (Ga) atoms from semi-insulating GaAs (SI-GaAs) into ZnO films upon post-growth annealing vis-`a-vis the resulting charge compensation was investigated with the help of x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy. The films, annealed at 600 °C and 700 °C showed...
p-type conducting films of α- BaCu₂S₂ have been deposited onto glass and KBr substrates, yielding a conductivity of 17 S/cm and a Hall mobility of 3.5 cm²/Vs. For a 430-nm-thick film, the optical transparency approaches 90% in the visible portion of the spectrum at 650 nm, and a transparency of...
We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 10⁴ ion-doped droplets (one ion per droplet) can...
A model is developed to describe the reversible nature of gecko dry adhesion. The central aspect of this model is that the seta can be easily peeled away from the contacting surface by a small moment at the contact tip. It is shown that this contact condition is very sensitive,...
We report vibrational information of both the first electronically excited state and the ground
cationic state of jet-cooled triphenylene via the techniques of resonantly enhanced multiphoton
ionization (REMPI) and zero kinetic energy (ZEKE) photoelectron spectroscopy. The first excited
electronic state S₁ of the neutral molecule is of A₁' symmetry and...
Epitaxy of III-V semiconductors on Si gets recent interest for next generation system on
heterogeneous chip on wafer. The understanding of band offset is thus necessary for describing
the charge transport phenomenon in these heterojunctions. In this work, x-ray photoemission
spectroscopy has been used to determine the band offsets in...
Lead-free Bi(Mg₁/₂Ti₁/₂)O₃-(Bi₁/₂K₁/₂)TiO₃-(Bi₁/₂Na₁/₂)TiO₃ (BMT-BKT-BNT) ceramics have
been shown to exhibit large electromechanical strains under high electric fields along with
negligible fatigue under strong electric fields. To investigate the role of point defects on the
fatigue characteristics, the composition 5BMT-40BKT-55BNT was doped to incorporate acceptor and
donor defects on the A and...
Cryopreservation of human red blood cells (RBCs) in the presence of 40% glycerol
allows a shelf-life of 10 years, as opposed to only 6 weeks for refrigerated
RBCs. Nonetheless, cryopreserved blood is rarely used in clinical therapy, in part
because of the requirement for a time-consuming (~1 h) post-thaw wash...
In situ photoemission spectroscopy experiments are used to characterize the interface between ZnTe and the wide band gap p-type semiconductor BaCuSeF. The contact is characterized by a null valence-band offset, a large conduction-band offset, and a chemically graded interface. By applying the transitivity rule for band offset and on the...
We perform two-dimensional linear elastic finite element analysis to investigate the mechanical stability of ultrathin Ge/Si film grown on or bonded to SiO₂, using imperfect interface elements between Si and SiO₂ to model Si/SiO₂ interfacial slippage. We demonstrate that the overall composite film is stable when only the tangential slippage...
The recent quest for improved functional materials like high permittivity dielectrics and/or
multiferroics has triggered an intense wave of research. Many materials have been checked for their
dielectric permittivity or their polarization state. In this report, we call for caution when samples are
simultaneously displaying an insulating behavior and a...
The dielectric spectra of CaCu₃Ti₄O₁₂ is characterized by a large permittivity (εᵣ>10 000) with only a weak dependence on temperature over the temperature range 200–400 K. In this work, doping with 0.1–1.0 wt % ZrO₂ has been shown to dramatically reduce the dielectric loss. At 0.5 wt % ZrO₂, tan...
The crystal structure and multiferroic properties of single-phase (Bi₀.₉La₀.₁)FeO₃–Ba(Fe₀.₅Nb₀.₅)O₃ ceramics were investigated. The rhombohedral-type structure of 1.0(Bi₀.₉La₀.₁)FeO₃) was transformed to a monoclinic-type structure for the 0.5(Bi₀.₉La₀.₁)FeO₃–0.5Ba(Fe₀.₅Nb₀.₅)O₃) composition. It shows the coexistence of ferroelectricity and magnetism at room temperature, represented by a high dielectric constant with ferroelectric hysteresis and clear magnetic...
Deformation of metallic glasses requires the existence of free volume to allow atomic movement under mechanical loading. Accordingly, quantification of the free volume state of the alloy is crucial to understand it's mechanical behavior. By annealing below the glass transition temperature, the free volume of a Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅ bulk metallic glass...
We employ two different methods to generate controllable elliptical polarization of teraherz (THz) pulses. First, THz pulses are generated via optical rectification in nonlinear crystals using a pair of temporally separated and perpendicularly polarized optical pulses. The THz ellipticity is controlled by adjusting the relative time delay and polarization of...
We demonstrate a technique for terahertz pulse shaping via optical rectification in the pre-engineered domain structure of poled lithium niobate crystals. The terahertz wave forms coincide with the crystal domain structures. The one-dimensional nonlinear wave equation simulates the experimental results with a good qualitative agreement.
The authors demonstrate an efficient room temperature source of terahertz radiation using femtosecond laser pulses as a pump and GaAs structures with periodically inverted crystalline orientation, such as diffusion-bonded stacked GaAs and epitaxially grown orientation-patterned GaAs, as a nonlinear optical medium. By changing the GaAs orientation-reversal period (504–1277 μm), or...
BaCuQF (Q=S,Se) materials, candidate transparent p-type conductors, were prepared by solid-state reaction, and their bulk electrical and optical properties were evaluated. The room-temperature Seebeck coefficient and electrical conductivity of undoped BaCuQF pellets were +56 μV/K and 0.088 S/cm, respectively, for the sulfide fluoride, and +32 μV/K and 0.061 S/cm, respectively,...
The authors demonstrate a flexible terahertz pulse-shaping technique, manipulating spatially dispersed multifrequency components generated by optical rectification in a fanned-out periodically poled lithium niobate crystal. Spatial masks of low pass, high pass, and double slit in front of the crystal manipulate the spatial pattern of the optical excitation beam on...
Sputter deposited amorphous Ge thin films had their nanostructure altered by irradiation with high-energy Ar⁺ ions. The change in the structure resulted in a reduction in medium range order (MRO) characterized using fluctuation electron microscopy. The pulsed laser crystallization kinetics of the as-deposited versus irradiated materials were investigated using the...
We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He₂ ⁺ and He₄ ⁺, which...
We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs⁺ is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient...
The performance of thin film metal-insulator-metal (MIM) diodes is investigated for a variety of large and small electron affinity insulators using ultrasmooth amorphous metal as the bottom electrode. Nb2O5, Ta2 O5, ZrO2, HfO2, Al2 O3, and SiO2 amorphous insulators are deposited via atomic layer deposition (ALD). Reflection electron energy loss...
Kelvin-Helmholtz (KH) instability, characterized by the distinctive finite-amplitude billows it generates, is an important mechanism in the development of turbulence in the stratified interior of the ocean. In particular, it is often assumed that the onset of turbulence in internal waves begins in this way. Clear recognition of the importance...
Desferrioxamine B (DFOB) was reversibly and covalently conjugated to polystyrene microspheres via N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP) crosslinker. DFOB retained post-immobilization activity with at least 89% able to bind Fe(III)-citrate under pH 7.4 and a citrate:iron molar ratio = 100:1. Comparing iron capture by DFOB-activated beads and sulfhydryl (−SH) control beads demonstrated...
Internal‐tide generation is usually predicted from local topography, surface tides, and stratification. However, internal tides are often observed to be unrelated to local spring‐neap forcing, appearing intermittently in 3–5 day bursts. Here we suggest a source of this intermittency by illustrating how remotely‐generated shoaling internal tides induce first‐order changes in...
The defect mechanisms that underpin the high energy density dielectric 0.8BaTiO₃–0.2Bi(Zn₁/₂Ti₁/₂) O₃
were investigated. Characterization of the nominally stoichiometric composition revealed the
presence of a Ti³⁺-related defect center, which is correlated with lower resistivities and an
electrically heterogeneous microstructure. In compositions with 2 mol. % Ba-deficiency, a barium
vacancy-oxygen vacancy...
Full Text:
homogeneous microstructure. VC 2012 American Institute of Physics.
[http://dx.doi.org/10.1063/1.4752452]
For
We used simulated magnetic displacements to test orientation preferences of
juvenile steelhead trout (Oncorhynchus mykiss) exposed to magnetic fields
existing at the northernmost and southernmost boundaries of their oceanic
range. Fish reared in natural magnetic conditions distinguished between
these two fields by orienting in opposite directions, with headings that
would...
Full Text:
–882.
(doi:10.1063/1.1137480)
14. Light JT, Harris CK, Burgner RL. 1989 Ocean
distribution and
We demonstrate that unidirectionally aligned, free-standing multi-walled carbon nanotubes (CNTs) exhibit highly anisotropic linear and nonlinear terahertz (THz) responses. For the polarization parallel to the CNT axis, strong THz pulses induce nonlinear absorption in the quasi-one-dimensional conducting media, while no nonlinear effect is observed in the perpendicular polarization configuration. Time-resolved...
We report electron diffraction of ferrocene doped in superfluid helium droplets. By taking advantage of the velocity slip in our pulsed droplet beam using a pulsed electron gun, and by doping with a high concentration of ferrocene delivered via a pulsed valve, we can obtain high quality diffraction images from...
We report an ultra-compact, cost-effective on-chip near-infrared spectroscopy system for CO₂ sensing using narrow-band optical filter array based on plasmonic gratings with a waveguide layer. By varying the periodicity of the gratings, the transmission spectra of the filters can be continuously tuned to cover the 2.0 μm sensing window with high...
Coherent phonon dynamics in condensed-phase medium are responsible for important material properties including thermal and electrical conductivities. We report a structural dynamics technique, time-resolved surface third-harmonic generation (TRSTHG) spectroscopy, to capture transient phonon propagation near the surface of polycrystalline CaF₂ and amorphous borosilicate (BK7) glass. Our approach time-resolves the background-free,...
A shell model for ferroelectric perovskites fitted to results of first-principles density functional theory (DFT) calculations is strongly affected by approximations made in the exchange-correlation functional within DFT, and in general not as accurate as a shell model derived from experimental data. We have developed an isotropic shell model for...
We demonstrate remarkably strong nonlinear terahertz (THz) effects in an intrinsic GaAs wafer patterned with a nanometer-width slot antenna array. The antenna near-field reaches 20 MV/cm due to the huge field enhancement in the plasmonic nano-structure (field enhancement factor, α ≅ 50). The THz fields are strong enough to generate high density...
The electrode size dependence of the effective large signal piezoelectric response coefficient (d(33,f)) of lead zirconate titanate (PZT) thin films is investigated by using double beam laser interferometer measurements and finite element modeling. The experimentally observed electrode size dependence is shown to arise from a contribution from the substrate. The...
The origin of high hole conduction in BaCuQF (Q=S,Se) was investigated by photoemission
measurements and full-potential linearized augmented plane wave band-structure calculations. In
both compounds, the large dispersion near the top of the valence band is realized by admixed states
of Cu 3d and S 3p or Se 4p orbitals,...
CuCr₁₋ₓMgₓO₂, a wide band gap semiconductor with the delafossite structure, has been synthesized
in bulk and thin-film form. Bulk undoped CuCrO₂ is almost black and has moderate conductivity
with p-type carriers. Upon doping with 5% Mg, the conductivity increases by a factor of 1000. In
films, the best p-type conductivity...
Lead-free ceramics of composition Bi(Mg₁/₂Ti₁/₂)O₃-(Bi₁/₂K₁/₂)TiO₃-(Bi₁/₂Na₁/₂)TiO₃ were prepared
using solid state synthesis techniques. The dielectric spectra showed a Tmax of more than 320 °C
for all compositions, and the transitions became increasingly diffuse as the Bi(Mg₁/₂Ti₁/₂)O₃
content increased. A lower temperature transition, indicating a transformation from an ergodic to a
non-ergodic...
Molybdenum disulfide (MoS₂) field effect transistors (FET) were fabricated on atomically smooth large-area single layers grown by chemical vapor deposition. The layer qualities and physical properties were characterized using high-resolution Raman and photoluminescence spectroscopy, scanning electron microscopy, and atomic force microscopy. Electronic performance of the FET devices was measured using...
We demonstrate the generation of broadband up-converted multicolor array (BUMA) in a thin BK7 glass slide using two noncollinear weak near-IR laser pulses with various crossing angles. The BUMA signal arises from cubic nonlinear χ⁽³⁾:χ⁽³⁾ processes via cascaded four-wave mixing of the two incident beams. Broad and continuous tunability of...
A definition is suggested for affine symmetry tensors, which generalize the notion of affine vectors in the same way that (conformal) Killing tensors generalize (conformal) Killing vectors. An identity for these tensors is proven, which gives the second derivative of the tensor in terms of the curvature tensor, generalizing a...
We measure the thermal conductivities of nano-grained strontium titanate (ng-SrTiO₃) films deposited on sapphire substrates via time-domain thermoreflectance. The 170 nm thick oxide films of varying grain-size were prepared from a chemical solution deposition process. We find that the thermal conductivity of ng-SrTiO₃ decreases with decreasing average grain size and attribute...
Depth-profiled Doppler broadening spectroscopy of positron annihilation on the cyclic fatigue-induced fracture surfaces of three amorphous Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅ metallic glass specimens reveals the presence of a 30–50 nm layer of increased free volume that is generated by the propagating fatigue crack tip. The presence and character of this fatigue transformation zone...
Highly transparent ZnO-based thin-film transistors (TFTs) are fabricated with optical transmission (including substrate) of ~75% in the visible portion of the electromagnetic spectrum. Current–voltage measurements indicate n-channel, enhancement-mode TFT operation with excellent drain current saturation and a drain current on-to-off ratio of ~10⁷. Threshold voltages and channel mobilities of devices...
Transparent thin-film transistors (TTFTs) with an amorphous zinc tin oxide channel layer formed via rf magnetron sputter deposition are demonstrated. Field-effect mobilities of 5–15 and 20–50 cm² V‾¹ s‾¹ are obtained for devices post-deposition annealed at 300 and 600 °C, respectively. TTFTs processed at 300 and 600 °C yield devices...
The authors analyze electromagnetic modes in multilayered nanocomposites and demonstrate that the response of a majority of realistic layered structures is strongly affected by the nonlocal effects originating from strong field oscillations across the system, and is not described by conventional effective-medium theories. They develop the analytical description of the...
The authors study perspectives of nanowire metamaterials for negative-refraction waveguides, high-performance polarizers, and polarization-sensitive biosensors. They demonstrate that the behavior of these composites is strongly influenced by the concentration, distribution, and geometry of the nanowires, derive an analytical description of electromagnetism in anisotropic nanowire-based metamaterials, and explore the limitations of...
We report on the effect of various guest molecules added to a functionalized anthradithiophene (ADT) host on photoexcited charge carrier dynamics in solution-deposited thin films, from ~100 ps to >100 μs after photoexcitation with 100 fs laser pulses. An addition of 2 and 5 wt % of C60 to a...
We derive an approach to determine the causal direction of wavevectors of modes in optical metamaterials, which, in turn, determines signs of refractive index and impedance as a function of real and imaginary parts of dielectric permittivity and magnetic permeability. We use the developed technique to demonstrate that the interplay...
We analyze the performance of a planar lens based on realistic negative index material in a generalized geometry. We demonstrate that the conventional superlens design (where the lens is centered between the object and the image) is not optimal from the resolution point of view, develop an analytical expression for...
High electron mobility thin films of In₂₋ₓWₓO₃₊y(0≤x≤0.075) were prepared on amorphous SiO₂ and single-crystal yttria-stablized zirconia (001) substrates by pulsed laser deposition. Mobilities ranged between 66 and 112 cm² /Vs depending on the substrate type and deposition conditions, and the highest mobility was observed at a W-dopant concentration of x~0.03....
The authors demonstrate the generation of multicycle narrow-bandwidth terahertz pulses in periodically inverted GaAs structures using optical rectification of 2 μm, 100 fs pump pulses. Three different types of orientation-inverted samples are employed: optically contacted multilayer, orientation-patterned, and diffusion-bonded GaAs. The terahertz pulses are characterized by two-color (pump at 2...
Aqueous, two-phase systems (ATPSs) may form upon mixing two solutions of independently water-soluble compounds. Many separation, purification, and extraction processes rely on ATPSs. Predicting the miscibility of solutions can accelerate and reduce the cost of the discovery of new ATPSs for these applications. Whereas previous machine learning approaches to ATPS...
We present a model that describes nanosecond (ns) time-scale photocurrent dynamics in functionalized anthradithiophene (ADT) films and ADT-based donor-acceptor (D/A) composites. By fitting numerically simulated photocurrents to experimental data, we quantify contributions of multiple pathways of charge carrier photogeneration to the photocurrent, as well as extract parameters that characterize charge...
This study addresses the relationship between thermal microfronts and coherent vortex structures in homogeneous turbulence. The turbulence is created by mean shear in a weakly stratified flow. The data set is generated by direct numerical simulation providing highly resolved instantaneous three‐dimensional fields of fluctuating velocity and temperature (1603 data points...
Transparent p – i – n heterojunction diodes are fabricated using heavily doped, p-type CuYO₂ and
semi-insulating i-ZnO thin films deposited onto a glass substrate coated with n-type indium tin
oxide. Rectification is observed, with a ratio of forward-to-reverse current as high as 60 in the range
−4–4 V. The...
Carbon 1s photoelectron spectra for 2-butyne (CH3C CCH3) measured in the photon energy range from threshold to 150 eV above threshold show oscillations in the intensity ratio C2,3/C1,4. Similar oscillations have been seen in chloroethanes, where the effect has been attributed to EXAFS-type scattering from the substituent chlorine atoms. In...
Epitaxial LaRh₁/₂Mn₁/₂O₃ thin films have been grown on (001)-oriented LaAlO₃ and SrTiO₃ substrates using pulsed laser deposition. The optimized thin film samples are semiconducting and ferromagnetic with a Curie temperature close to 100 K, a coercive field of 1200 Oe, and a saturation magnetization of 1.7μB per formula unit. The...
We report on a novel class of semiconductor metamaterials that employ a strongly anisotropic dielectric function to achieve negative refraction in the midinfrared region of the spectrum, ~8.5–13 μm. We present two types of metamaterials, layered highly doped/undoped heterostructures and quantum well superlattices that are highly anisotropic. Contrary to other...
Solvent extraction is an integral chemical and biochemical separation process that is drastically intensified in microfluidic systems. A novel high-throughput micro-separator was additively manufactured for the intensification of liquid–liquid separation. The micro-posts array within the flow plate generated a capillary pressure gradient on the non-wetting organic phase, enabling continuous, membrane-free,...
The present article establishes connections between the structure of the deterministic Navier-Stokes equations and the structure of (similarity) equations that govern self-similar solutions as expected values of certain naturally associated stochastic cascades. A principle result is that explosion criteria for the stochastic cascades involved in the probabilistic representations of solutions...
This study conducted well-to-pump and well-to wheel life-cycle assessment of fossil energy use and greenhouse gas (GHG) emissions during ethanol production from tropical Banagrass (Pennisetum purpureum) using green-processing (with the use of fresh feedstocks) and dry or conventional processing (with the use of dried feedstocks) in the state of Hawaii....
The undertow is one of the most important mechanisms for sediment transport in
nearshore regions. As such, its formulation has been an active subject of research for
at least the past 40 years. Still, much debate persists on the exact nature of the forcing
and theoretical expression of this current....
Resilient interdependent critical infrastructures (CIs) can better withstand cascading failures in disruptive events. This study proposes network expansion as a resilience improvement strategy for interdependent CIs and evaluates the influence of topology in interdependent network design for resilience optimization under disruption uncertainty. A resilience score consisting of network complexity and...