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

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

/pdf/spintronics-fundamentals-and-applications-2dx38n6phu.pdf

Spintronics: Fundamentals and applications

Organizational Citizenship Behaviors: A Critical Review of the Theoretical and Empirical Literature and Suggestions for Future Research

We test the relationship between shareholder value, stakeholder management, and social issue participation. Building better relations with primary stakeholders like employees, customers, suppliers, and communities could lead to increased shareholder wealth by helping firms develop intangible, valuable assets which can be sources of competitive advantage. On the other hand, using corporate resources for social issues not related to primary stakeholders may not create value for shareholders. We test these propositions with data from S&P 500 firms and find evidence that stakeholder management leads to improved shareholder value, while social issue participation is negatively associated with shareholder value. Copyright © 2001 John Wiley & Sons, Ltd.

http://faculty.wwu.edu/dunnc3/rprnts.shareholdervaluesocialissues.pdf

Shareholder value, stakeholder management, and social issues: what's the bottom line?

In the past ten years we have witnessed a revival of, and subsequent rapid expansion in, the research on zinc oxide (ZnO) as a semiconductor. Being initially considered as a substrate for GaN and related alloys, the availability of high-quality large bulk single crystals, the strong luminescence demonstrated in optically pumped lasers and the prospects of gaining control over its electrical conductivity have led a large number of groups to turn their research for electronic and photonic devices to ZnO in its own right. The high electron mobility, high thermal conductivity, wide and direct band gap and large exciton binding energy make ZnO suitable for a wide range of devices, including transparent thin-film transistors, photodetectors, light-emitting diodes and laser diodes that operate in the blue and ultraviolet region of the spectrum. In spite of the recent rapid developments, controlling the electrical conductivity of ZnO has remained a major challenge. While a number of research groups have reported achieving p-type ZnO, there are still problems concerning the reproducibility of the results and the stability of the p-type conductivity. Even the cause of the commonly observed unintentional n-type conductivity in as-grown ZnO is still under debate. One approach to address these issues consists of growing high-quality single crystalline bulk and thin films in which the concentrations of impurities and intrinsic defects are controlled. In this review we discuss the status of ZnO as a semiconductor. We first discuss the growth of bulk and epitaxial films, growth conditions and their influence on the incorporation of native defects and impurities. We then present the theory of doping and native defects in ZnO based on density-functional calculations, discussing the stability and electronic structure of native point defects and impurities and their influence on the electrical conductivity and optical properties of ZnO. We pay special attention to the possible causes of the unintentional n-type conductivity, emphasize the role of impurities, critically review the current status of p-type doping and address possible routes to controlling the electrical conductivity in ZnO. Finally, we discuss band-gap engineering using MgZnO and CdZnO alloys.

/pdf/fundamentals-of-zinc-oxide-as-a-semiconductor-1s4l8bh009.pdf

Fundamentals of zinc oxide as a semiconductor

Poniendo el Balanced Scorecard en acción

Bulk ZnO Schottky rectifiers with Pt rectifying contacts were exposed to 40 MeV protons at fluences from 5 x 109 to 5 x 10 10 cm -2 . These doses correspond to that received in more than 10 or 100 years, respectively, in low earth satellite orbit. The reverse breakdown voltage of the ZnO diodes increased from ∼3.2 V (taken at a current density of 0.1 A/cm2) in unirradiated devices to ∼3.9 V after the highest proton dose. The effective barrier height decreased with proton dose from 0.37 eV to 0.35 eV while the diode ideality factor increased from 1.8 to 1.9 for the 5 × 10 10 dose. The very high tolerance of the ZnO diodes to high doses of energetic protons suggests that this material is well-suited to applications requiring high radiation tolerance.

Effects of high dose proton irradiation on the electrical performance of ZnO Schottky diodes

${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ films grown on both ${\mathrm{SrTiO}}_{3}$ single-crystal and rolling-assisted biaxially textured (Ni) substrates (RABiTS) carry high critical current densities ${J}_{c}.$ A geometrical barrier to vortex motion raises the apparent ${J}_{c},$ but also increases power loss associated with ac transport current through such tape above that expected from Norris's 1970 theory of hysteretic energy loss. Present theoretical estimates of the geometrical barrier have insufficient magnitude to account for our observations at low ac current levels. Evidence is reported that the ferromagnetic Ni substrate makes no significant contribution to the tape self-field loss. Loss is enhanced, and ${J}_{c}$ modestly reduced by the presence of low-angle grain boundaries. Application of dc magnetic field further lowers ${J}_{c}$ and raises loss in films.

Alternating transport-current flow in superconductive films: The role of a geometrical barrier to vortex motion

The microstructural properties of secondary phase particles formed in epitaxial CoxTi1−xO2 anatase thin films grown on (0 0 1)LaAlO3 by a reactive RF magnetron co-sputter deposition are examined. These films exhibit ferromagnetic behavior in magnetization measurements, showing a M–H loop at room temperature with a saturation magnetization on the order of 0.7 μB /Co. X-ray photoemission spectrometry indicates that the Co cations are in the Co2+ valence state. Cross-section electron microscopy reveals that a significant fraction of the cobalt segregates into Co–Ti–O secondary phase particles. Selected area electron diffraction shows that the secondary phase particles are cobalt-rich anatase. While the cobalt is concentrated in the segregated particles, local energy dispersive spectrometry indicates some Co throughout the film.

David P. Norton

Papers

Poniendo el Balanced Scorecard en acción

Effects of high dose proton irradiation on the electrical performance of ZnO Schottky diodes

Alternating transport-current flow in superconductive films: The role of a geometrical barrier to vortex motion

Structure and composition of secondary phase particles in cobalt-doped TiO2 films

Deposition of WN x C y Using the Allylimido Complexes Cl 4 "RCN…W"NC 3 H 5 …: Effect of NH 3 on Film Properties