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

The De Haas-van Alphen effect and Fermi surface in rhodium

In this paper we suggest an approach to making new metastable ferroelectric materials and piezoelectric transducers which should be efficient in generating coherent phonons with wavelengths approaching interatomic distances. This involves the fabrication of composition‐modulated (layered) structures consisting of piezoelectric components. The coherency strain accompanying short wavelength composition modulation leads to ferroelectricity; the periodic modulation of the piezoelectric parameters leads to an anomalously strong coupling to far infrared light when the composition wavelength is an odd half‐multiple of the wavelength of a phonon at the driving frequency. Such transducers can open a new dimension in the study of phonons in dielectrics at low temperatures.

Ferroelectricity and coherent phonon generation in piezoelectric composition‐modulated structures

Surface tension anisotropy and relaxation in uniaxially compressed Langmuir monolayers

Simultaneous measurements of the surface pressure‐molecular area (Π‐A) diagrams and the shear modulus of a series of long chain aliphatic alcohols C18OH, C20OH, C21OH, and C22OH spread on water indicate that the conventional phase assignments based on the compressibility are not reliable.

The phases of insoluble monolayers: Comparison between the surface pressure‐molecular area (Π‐A) diagram and shear modulus measurements

We have investigated the spin dynamics of a sputtered Co thin film using our broadband ferromagnetic resonance (FMR) spectrometer. From FMR spectra taken at frequencies of 4–20 GHz, we found that our Co film has a g-factor of 2.25 and a Gilbert damping factor of 4.5×108 s−1, indicating an enhanced spin-orbit interaction compared to bulk material or epitaxial films. Besides the normal FMR mode in the saturated state, we also observed the evolution of the low-field hysteretic behavior in the unsaturated state, which affects the FMR mode as the excitation frequency is lowered from 5.000 to 1.636 GHz. We found that the microwave absorption process persists in the unsaturated state for frequencies higher than 1.868 GHz such that the absorption minima occur at −12 Oe on a down-field sweep and at +12 Oe on a up-field sweep, respectively.

John B Ketterson

Papers

The De Haas-van Alphen effect and Fermi surface in rhodium

Ferroelectricity and coherent phonon generation in piezoelectric composition‐modulated structures

Surface tension anisotropy and relaxation in uniaxially compressed Langmuir monolayers

The phases of insoluble monolayers: Comparison between the surface pressure‐molecular area (Π‐A) diagram and shear modulus measurements

Hysteretic characteristics of low-field microwave absorption of a Co thin film