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

We have carried out infrared magnetotransmission measurements on a 5000-A-thick bismuth film grown by molecular beam epitaxy onto a CdTe substrate. The data for photon energies below 300 meV display at least ten orders of minima due to interband transitions at the L points. In contrast to previous results from magnetoreflectivity experiments on bulk Bi, two concurrent series of resonances separated by a nearly constant energy of ≃5 meV are observed. An additional series of strong oscillations emerges at somewhat higher photon energies, due to interband transitions at the T point

Magneto-optical determination of the T-point energy gap in bismuth.

We have prepared YBa2Cu3O7−δ (YBCO) superconducting wires by electrophoretic deposition. Ag wire was used as a substrate. Adding a small amount of BaF2 tends to remove cracks in the YBCO layer which develop during the heating process. The suppression of cracks produced a dramatic improvement in the critical current density (Jc). At 77 K, Jc increased from 18 A/cm2 for BaF2‐free YBCO wire to 646 A/cm2 for a critical concentration of 2.7 wt% BaF2 after which it decreased monotonically with increasing BaF2 content.

Jc enhancement of electrophoretically deposited YBa2Cu3O7−δ superconducting wire by BaF2 addition

Propagation of magnetostatic spin waves in an yttrium iron garnet film for out-of-plane magnetic fields

Sound Propagation in the Heavy Fermion Superconductors

This work was supported by the Office of Naval Research under Grant No. N00014-82-K-52-98 and the Northwestern Materials Research Center under National Science Foundation Grant No. DMR79-23573

John B Ketterson

Papers

Magneto-optical determination of the T-point energy gap in bismuth.

Jc enhancement of electrophoretically deposited YBa2Cu3O7−δ superconducting wire by BaF2 addition

Propagation of magnetostatic spin waves in an yttrium iron garnet film for out-of-plane magnetic fields

Sound Propagation in the Heavy Fermion Superconductors

Logarithmic transport behavior in new pbte-bi superlattice films