There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Principles of Neural Science

This article reviews the current status of lattice-dynamical calculations in crystals, using density-functional perturbation theory, with emphasis on the plane-wave pseudopotential method. Several specialized topics are treated, including the implementation for metals, the calculation of the response to macroscopic electric fields and their relevance to long-wavelength vibrations in polar materials, the response to strain deformations, and higher-order responses. The success of this methodology is demonstrated with a number of applications existing in the literature.

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Phonons and related crystal properties from density-functional perturbation theory

We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Band parameters for III–V compound semiconductors and their alloys

The need to develop inexpensive renewable energy sources stimulates scientific research for efficient, low-cost photovoltaic devices.1 The organic, polymer-based photovoltaic elements have introduced at least the potential of obtaining cheap and easy methods to produce energy from light.2 The possibility of chemically manipulating the material properties of polymers (plastics) combined with a variety of easy and cheap processing techniques has made polymer-based materials present in almost every aspect of modern society.3 Organic semiconductors have several advantages: (a) lowcost synthesis, and (b) easy manufacture of thin film devices by vacuum evaporation/sublimation or solution cast or printing technologies. Furthermore, organic semiconductor thin films may show high absorption coefficients4 exceeding 105 cm-1, which makes them good chromophores for optoelectronic applications. The electronic band gap of organic semiconductors can be engineered by chemical synthesis for simple color changing of light emitting diodes (LEDs).5 Charge carrier mobilities as high as 10 cm2/V‚s6 made them competitive with amorphous silicon.7 This review is organized as follows. In the first part, we will give a general introduction to the materials, production techniques, working principles, critical parameters, and stability of the organic solar cells. In the second part, we will focus on conjugated polymer/fullerene bulk heterojunction solar cells, mainly on polyphenylenevinylene (PPV) derivatives/(1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61) (PCBM) fullerene derivatives and poly(3-hexylthiophene) (P3HT)/PCBM systems. In the third part, we will discuss the alternative approaches such as polymer/polymer solar cells and organic/inorganic hybrid solar cells. In the fourth part, we will suggest possible routes for further improvements and finish with some conclusions. The different papers mentioned in the text have been chosen for didactical purposes and cannot reflect the chronology of the research field nor have a claim of completeness. The further interested reader is referred to the vast amount of quality papers published in this field during the past decade.

Conjugated polymer-based organic solar cells

High quality InN layers suffer from extremely high electron concentrations especially on surfaces and at interfaces. Even if their electron mobility could be extremely high, this prevents the electron depletion and so the application of this outstanding material in field effect transistors. Surface treatments like oxidation assisted by UV irradiation under Ozone atmosphere results in the decrease of the surface electron concentration. This has been confirmed by a combination of resistance and AES measurements. In order to investigate the surface modification by this oxidation laterally highly resolved Auger measurements have been carried out. The Auger signal intensities give information about the growing surface oxygen concentration whereas the Auger peak positions give information about the position of the Fermi level. The results show, that the oxidation process is heavily dependent on the quality of the InN surface. The oxidation is laterally inhomogeneous and the growing oxygen concentration is accompanied by a peak shift to the rhomboedric indium oxide value. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ozone and UV assisted oxidation of InN surfaces

An AlGaN/GaN high electron mobility transistor (HEMT) stressed at 10 GHz and increased channel temperatures of T ≈ 260 °C has been analyzed by electroluminescence microscopy (ELM) and infrared thermography (IRT). After stress a negative threshold shift is seen in the electrical characteristics. Based on the current dependence of the electroluminescence (EL) intensity image and a local increase of T this shift can be assigned to the degradation of one of its gate fingers. Transmission electron microscopy (TEM) images of this gate finger revealed structural changes along the drain-side edge of the gate.

Microscopic Degradation Analysis of RF-Stressed AlGaN/GaN HEMTs

In this paper, we demonstrate an active 3D millimeter wave (mmW) imaging system used for characterization of dielectric multilayer materials. Reflectometry is used to obtain the evolution of the refractive indices of unknown materials over a frequency range between 75 GHz and 110 GHz, denoted as W-band. Depending on the measured strength of dispersion, precise localization of small defects such as voids or delamination in multilayer structures can be realized by mmW imaging using the same system.

Analysis of Dielectric Properties of Layered Plastics at W-Band Frequencies

Stability of GaN films under intense MeV He ion irradiation

A novel balanced 210 GHz mixer MMIC with a measured IF bandwidth of more than 50 GHz and an RF bandwidth of more than 100 GHz has been successfully developed in a 50 nm mHEMT technology The mixer achieves a measured conversion loss of 17 dB The measured LO-to-RF isolation is better than 17 dB in the relevant frequency range Two Lange couplers are used to balance the design The IF signal is tapped at the isolated RF coupler port to increase the IF bandwidth

Oliver Ambacher

Papers

Ozone and UV assisted oxidation of InN surfaces

Microscopic Degradation Analysis of RF-Stressed AlGaN/GaN HEMTs

Analysis of Dielectric Properties of Layered Plastics at W-Band Frequencies

Stability of GaN films under intense MeV He ion irradiation

A balanced resistive 210 GHz mixer with 50 GHz IF bandwidth