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

A-Si films with a constant optical band gap were prepared by plasma CVD from silane at deposition rates up to 17 A/s under controllably varied conditons and characterized by a number of techniques. Photodegradation under AM1 simulator has been done for 50 hours and for 4-17 hours under 2 Watt/cm2 dye laser illumination at a wavelength corresponding to an absorption coefficient of about 104 cm-1 up to saturation. Samples with different initial value of σ(d) and σ(ph) show different rates of photodegra-dation, but they reach very similar saturation values. The fast photode-gradation with the dye laser is equivalent to a long term (several thousand hours) photodegradation under AM1. The AMI photodegradation for 50 to 100 hours does not yield any reliable measure of the stability of the films. The best films, which were prepared at a high deposition temperature show a low saturation defect density of about 5·1016 cm-3 (CPM-data).

Photodegradataion and Stability of a-Si Prepared at High Deposition Rates

In this paper a broadband high-efficiency Class-BJ GaN HEMT-PA for wireless communication applications is realized. Influences of packaging and bond wires on the PA performance are investigated in order to demonstrate and use accurate package models. A novel optimization of bond wires for packaged powerbars is therefore performed and, subsequently a fully characterized PA is effectively designed. For the fully assembled PA module, measurement results demonstrated targeted broadband performance reaching approximately 50% operation bandwidth in the frequency range 1.7-2.8 GHz with 52-59% PAE, 58-66% drain efficiency and 43-44.5 dBm delivered output power while maintaining over 10 dB of GT.

Broadband 1.7–2.8 GHz high-efficiency (58%), high-power (43 dBm) Class-BJ GaN power amplifier including package engineering

Cubic InN on r-plane sapphire

In this paper we demonstrate an antenna for 300 GHz. The antenna is processed on quartz and consists of 2 quartz layers with 2 metal layers each, which are separated by benzocyclobutene (BCB). The edge length is 2 millimeters. Design, simulation and the analysis is done in CST Microwave Studio. Measurement is done after packaging on a brass disk. This work shows the design details, simulated results and measurement data of the presented antenna.

A 300 GHz microstrip multilayered antenna on quartz substrate

Two subharmonically pumped 210 GHz I/Q mixer MMICs have been successfully realized in a 100 nm gate length metamorphic high electron mobility transistor (mHEMT) technology. The mixers have been designed using a branchline and a Lange coupler to generate the 90° phase shift between the I and Q ports. A conversion gain of more than 19 dB has been achieved with both mixers. The measured LO to RF isolation of the second harmonic is better than 21 dB.

Oliver Ambacher

Papers

Photodegradataion and Stability of a-Si Prepared at High Deposition Rates

Broadband 1.7–2.8 GHz high-efficiency (58%), high-power (43 dBm) Class-BJ GaN power amplifier including package engineering

Cubic InN on r-plane sapphire

A 300 GHz microstrip multilayered antenna on quartz substrate

Subharmonically Pumped 210 GHz I/Q Mixers