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. ...

/pdf/a-comprehensive-review-of-zno-materials-and-devices-21a3zjadem.pdf

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 have measured the temperature dependence of the velocity and the attenuation of sound in the range 60–700 mK. The maximum in the sound velocity observed by Abraham and Osborne is confirmed. The viscosity deduced from the attenuation measurements is in good agreement with that of Abel, Anderson, and Wheatley but differs from that of Betts, Keen, and Wilks. The sound velocity as a function of pressure at 150 mK was also measured and from this the low-temperature pressure dependence of the density was determined.

Sound propagation, density, and viscosity in liquid 3 He

The oscillatory components of the transverse magnetoresistance of single crystals of antimony has been measured at 1.15\ifmmode^\circ\else\textdegree\fi{}K in the range of magnetic fields from 4000-25 000 G using a derivative technique. Measurements were made for the field in the $x\ensuremath{-}z$, $y\ensuremath{-}z$, and $x\ensuremath{-}y$ planes. Two sets of ellipsoidal carriers are clearly observed. One of the carriers was that observed by Shoenberg for which we found: ${\ensuremath{\alpha}}_{11}{\ensuremath{\alpha}}_{22}=0.334\ifmmode\times\else\texttimes\fi{}{10}^{28}{{E}_{F}}^{2}$, ${\ensuremath{\alpha}}_{11}{\ensuremath{\alpha}}_{33}=0.563\ifmmode\times\else\texttimes\fi{}{10}^{28}{{E}_{F}}^{2}$, and ${\ensuremath{\alpha}}_{11}{\ensuremath{\alpha}}_{23}=0.352\ifmmode\times\else\texttimes\fi{}{10}^{28}{{E}_{F}}^{2}$. We also found for the second set of carriers ${\ensuremath{\beta}}_{11}{\ensuremath{\beta}}_{22}=0.0227\ifmmode\times\else\texttimes\fi{}{10}^{28}{{E}_{F}}^{2}$, ${\ensuremath{\beta}}_{11}{\ensuremath{\beta}}_{33}=0.625\ifmmode\times\else\texttimes\fi{}{10}^{28}{{E}_{F}}^{2}$, ${\ensuremath{\beta}}_{11}{\ensuremath{\beta}}_{23}=0.0424\ifmmode\times\else\texttimes\fi{}{10}^{28}{{E}_{F}}^{2}$, and ${\ensuremath{\beta}}_{22}{\ensuremath{\beta}}_{33}\ensuremath{-}{{\ensuremath{\beta}}_{23}}^{2}=0.0627\ifmmode\times\else\texttimes\fi{}{10}^{28}{{E}_{F}}^{2}$. Discussions are included relating this data to that of other experiments.

de Haas-Shubnikov Effect in Antimony

A qubit device based on manipulations of Andreev bound states in double-barrier Josephson junctions

We show that magnetization reversal in spin-injection devices can be significantly faster when using a chirped rf current, rather than a dc, pulse. Although one can use a simple sinusoidal rf pulse, an optimized series of alternating, equal-amplitude, pulses of varying width (a digitized approximation to a chirped rf pulse) produces more efficient switching.

Switching spin valves using rf currents

We present the design of a versatile rf heterodyne spectrometer covering a 100 kHz to 190 MHz frequency range, which has been useful in nuclear magnetic resonance and acoustic experiments over its whole range. Commercial instruments were used wherever possible: two units, an rf pulse generator, and a 30‐MHz IF amplifier/detector were constructed and are described in detail. Also, we briefly outline application to ultrasound and NMR measurements and interfacing to a minicomputer‐based data processing system.

John B Ketterson

Papers

Sound propagation, density, and viscosity in liquid 3 He

de Haas-Shubnikov Effect in Antimony

A qubit device based on manipulations of Andreev bound states in double-barrier Josephson junctions

Switching spin valves using rf currents

Versatile pulsed rf heterodyne spectrometer