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.

/pdf/topological-insulators-with-inversion-symmetry-1vaykhe1u1.pdf

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

We investigated the spin-wave propagation in a micro-structured yttrium iron garnet waveguide of $40$ nm thickness. Utilizing spatially-resolved Brillouin light scattering microscopy, an exponential decay of the spin-wave amplitude of $(10.06 \pm 0.83)$ $\mu$m was observed. This leads to an estimated Gilbert damping constant of $\alpha=(8.79\pm 0.73)\times 10^{-4}$, which is larger than damping values obtained through ferromagnetic resonance measurements in unstructured films. The theoretically calculated spatial interference of waveguide modes was compared to the spin-wave pattern observed experimentally by means of Brillouin light scattering spectroscopy.

Spin waves in micro-structured yttrium iron garnet nanometer-thick films

We have studied the transfer of a surfactant covered film between two Langmuir troughs over a bridge-shaped glass slide when the surfactant concentrations in the two troughs were maintained at different values. We applied the Landau-Levich theory to this problem, assuming the Deryagin-Landau disjoining pressure for water films on glass. The theoretical relationship between the rate of transfer and the surface pressure differential in the two troughs is in good agreement with the experiment.

Steady transfer of a monolayer between two Langmuir troughs via the Marangoni effect

Inversion of de haas--van alphen data. i. closed surfaces with inversion symmetry.

A new technique for improving the accuracy of the angular orientation of nonsymmetry plane dHvA data on cubic systems by an order of magnitude (from 2.0° to 0.2°) has been developed. The extension of this technique to orienting dHvA data in noncubic crystallographic systems, or to orienting data for other types of experiments, viz. neutron scattering, should be straightforward.

Accurate orientation method for dHvA data

We report on a novel Magneto-Optical Trap (MOT) geometry involving the retroreflection of one of the six MOT beams in order to create an atom cloud close to the surface of a prism which does not have optical access along one axis. A MOT of Rb$^{85}$ with $\sim 4 \times 10^7$ atoms can be created 700 um from the surface. The MOT lies close to the minimum of an evanescent Gravito-Optical Surface Trap (GOST) allowing for transfer into the GOST with potentially minimal losses.

John B Ketterson

Papers

Spin waves in micro-structured yttrium iron garnet nanometer-thick films

Steady transfer of a monolayer between two Langmuir troughs via the Marangoni effect

Inversion of de haas--van alphen data. i. closed surfaces with inversion symmetry.

Accurate orientation method for dHvA data

Novel, Retroreflective, Magneto-Optical Trap Near a Surface