The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

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A comprehensive review of zno materials and devices

Every few years, a new material with unique properties emerges and fascinates the scientific community, typical recent examples being high-temperature superconductors and carbon nanotubes. Graphene is the latest sensation with unusual properties, such as half-integer quantum Hall effect and ballistic electron transport. This two-dimensional material which is the parent of all graphitic carbon forms is strictly expected to comprise a single layer, but there is considerable interest in investigating two-layer and few-layer graphenes as well. Synthesis and characterization of graphenes pose challenges, but there has been considerable progress in the last year or so. Herein, we present the status of graphene research which includes aspects related to synthesis, characterization, structure, and properties.

Graphene: The New Two-Dimensional Nanomaterial

Topological insulators are materials with a bulk excitation gap generated by the spin-orbit interaction that are different from conventional insulators. This distinction is characterized by ${Z}_{2}$ topological invariants, which characterize the ground state. In two dimensions, there is a single ${Z}_{2}$ invariant that distinguishes the ordinary insulator from the quantum spin-Hall phase. In three dimensions, there are four ${Z}_{2}$ invariants that distinguish the ordinary insulator from ``weak'' and ``strong'' topological insulators. These phases are characterized by the presence of gapless surface (or edge) states. In the two-dimensional quantum spin-Hall phase and the three-dimensional strong topological insulator, these states are robust and are insensitive to weak disorder and interactions. In this paper, we show that the presence of inversion symmetry greatly simplifies the problem of evaluating the ${Z}_{2}$ invariants. We show that the invariants can be determined from the knowledge of the parity of the occupied Bloch wave functions at the time-reversal invariant points in the Brillouin zone. Using this approach, we predict a number of specific materials that are strong topological insulators, including the semiconducting alloy ${\mathrm{Bi}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x}$ as well as $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Sn}$ and HgTe under uniaxial strain. This paper also includes an expanded discussion of our formulation of the topological insulators in both two and three dimensions, as well as implications for experiments.

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Topological insulators with inversion symmetry

We have used the pH-induced self-assembly of a peptide-amphiphile to make a nanostructured fibrous scaffold reminiscent of extracellular matrix. The design of this peptide-amphiphile allows the nanofibers to be reversibly cross-linked to enhance or decrease their structural integrity. After cross-linking, the fibers are able to direct mineralization of hydroxyapatite to form a composite material in which the crystallographic c axes of hydroxyapatite are aligned with the long axes of the fibers. This alignment is the same as that observed between collagen fibrils and hydroxyapatite crystals in bone.

http://science.sciencemag.org/content/sci/294/5547/1684.full.pdf

Self-assembly and mineralization of peptide-amphiphile nanofibers

Nano-optics of surface plasmon polaritons

Susceptibility measurements on the Kondo alloy La:Ce show that X = cF(T,H) for 1.3 K ≤ T ≤ 300 K, c ≤ 15 at %, H ≤ 20 kG where F is independent of concentration c. At high temperatures (T > 30 K), F(T,O), like other Kondo systems, obeys a Curie‐Weiss law 1/(T + 27). At low temperatures (0.6 ≤ T ≤ 30 K), f (T,0) ∝ T−1/2. To test the sensitivity of this result to local environment and the effect of spin‐orbit scattering, measurements were made on Ce .01ThxLa.99−x (x ≤ 0.4) alloys. These measurements show that the Ce contribution to the susceptibility, cF(T,0), is unchanged by the addition of Th. The magnetic field dependence of X does not fit a Brillouin function. Generalizing Anderson's suggestion, a phenomenological model is developed which assumes that the density of states N(E) ∝ (e2 + Δ)−1/4 whwrw Δ−1 is a lifetime. The calculated numerical results from this model for F(T,H) are in good agreement with the experimental results. Qualitatively F ∝ (T2 + μ2H2 + Δ)−δ where δ = 1/4. The Hirschkoff et al. data on Cu:Fe also fits this form with δ = l/3 and Δ∝c2 . The value δ = 1/3 does not fit our data. The importance of crystalline fields and the value of TK will be discussed. Other work on this system is briefly reviewed.

AN EQUATION OF STATE FOR THE KONDO SYSTEM La:Ce

Electro-, magneto-, and other rheological effects can be used to externally control fluid viscosity. However, they are largely reversible and in addition subject to colloidal settling, electrostatic breakdown, or high cost. In the experiments described here the dependence of the viscosity of a polymer solution under pulsed laser photocrosslinking as a function of radiation dose is determined using the Brownian motion of colloidal polystyrene tracers that were optically confined to a one dimensional channel. The system studied was a transparent aqueous solution of poly(ethylene glycol) dimethacrylate together with a 1-hydroxycyclohexyl phenyl ketone photoinitiator. An increase in the viscosity of the solution with the laser fluence was observed. The growth was exponential, stable between pulses, and spanned nearly three orders of magnitude. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40690.

Optorheological thickening under the pulsed laser photocrosslinking of a polymer

Magnetic field investigation of the acoustic impedance resonance near 2Δ(T) in 3He-A

Doppler-Shifted Ultrasonic Spin Resonance in Metals

We present the results of an experimental and theoretical study of spin wave dynamics in three-fold vertices made of permalloy nano-ellipses, with thicknesses ranging from 7.5 nm to 40 nm. For the most symmetric modes, a non-trivial variation of their frequency and intensity with the ellipse thickness is found. Simulations involving the dynamical matrix approach are in good agreement with the experiments.

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John B Ketterson

Papers

AN EQUATION OF STATE FOR THE KONDO SYSTEM La:Ce

Optorheological thickening under the pulsed laser photocrosslinking of a polymer

Magnetic field investigation of the acoustic impedance resonance near 2Δ(T) in 3He-A

Doppler-Shifted Ultrasonic Spin Resonance in Metals

Thickness dependence of spin wave dynamics in three-fold nano-ellipse clusters