Special topic volume with invited peer reviewed papers only.

The lifetime of a positron inside a solid is normally less than a fraction of nanosecond. This is a very short time on a human scale, but is long enough to enable the positron to visit an extended region of the material, and to sense the atomic and electronic structure of the environment. Thus, we can inject a positron in a sample to draw from it some signal giving us information on the microscopic properties of the material. This idea has been successfully developed in a number of positron-based techniques of physical analysis, with resolution in energy, momentum, or position. The complex of these techniques is what we call now positron spectroscopy of solids. The field of application of the positron spectroscopy extends from advanced problems of solid-state physics to industrial applications in the area of characterization of high-tech materials. This volume focuses the attention on the physics that can be learned from positron-based methods, but also frames those methods in a wider context including other experimental approaches. It can be considered as a textbook on positron spectroscopy of solids, the sort of book that the newcomer takes for his approach to this field, but also as a useful research tool for the expert.

This comprehensive book reports on recent investigations of lattice imperfections in semiconductors by means of positron annihilation. It reviews positron techniques, and describes the application of these techniques to various kinds of defects, such as vacancies, impurity vacancy complexes and dislocations.

Over the years, many successful attempts have been chapters in this part describe the well-known processes made to describe the art and science of crystal growth, such as Czochralski, Kyropoulos, Bridgman, and o- and many review articles, monographs, symposium v- ing zone, and focus speci cally on recent advances in umes, and handbooks have been published to present improving these methodologies such as application of comprehensive reviews of the advances made in this magnetic elds, orientation of the growth axis, intro- eld. These publications are testament to the grow- duction of a pedestal, and shaped growth. They also ing interest in both bulk and thin- lm crystals because cover a wide range of materials from silicon and III–V of their electronic, optical, mechanical, microstructural, compounds to oxides and uorides. and other properties, and their diverse scienti c and The third part, Part C of the book, focuses on - technological applications. Indeed, most modern ad- lution growth. The various aspects of hydrothermal vances in semiconductor and optical devices would growth are discussed in two chapters, while three other not have been possible without the development of chapters present an overview of the nonlinear and laser many elemental, binary, ternary, and other compound crystals, KTP and KDP. The knowledge on the effect of crystals of varying properties and large sizes. The gravity on solution growth is presented through a c- literature devoted to basic understanding of growth parison of growth on Earth versus in a microgravity mechanisms, defect formation, and growth processes environment.

The NATO Advanced Research Workshop on Fundamental Aspects of Inert Gases in Solids, held at Bonas, France from 16-22 September 1990, was the fifth in a series of meetings that have been held in this topic area since 1979. The Consultants' Meeting in that year at Harwell on Rare Gas Behaviour in Metals and Ionic Solids was followed in 1982 by the Jiilich Inter national Symposium on Fundamental Aspects of Helium in Metals. Two smaller meetings have followed-a CECAM organised workshop on Helium Bubbles in Metals was held at Orsay, France in 1986 while in February 1989, a Topical Symposium on Noble Gases in Metals was held in Las Vegas as part of the large TMS/AIME Spring Meeting. As is well known, the dominating feature of inert gas atoms in most solids is their high heat of solution, leading in most situations to an essentially zero solubility and gas-atom precipita tion. In organising the workshop, one particular aim was to target the researchers in the field of inert-gas/solid interactions from three different areas--namely metals, tritides and nuclear fuels-in order to encourage and foster the cross-fertilisation of approaches and ideas. In these three material classes, the behaviour of inert gases in metals has probably been most studied, partly from technological considerations-the effects of helium production via (n, a) reac tions during neutron irradiation are of importance, particularly in a fusion reactor environ ment-and partly from a more fundamental viewpoint.

There is no doubt that, when it comes to the study of the structures and defects of materials, there is presently no technique that rivals positron annihilation. The increasing demands for higher accuracy and reliability provide a constant stimulus to the field, and the present work presents the newest and most important scientific discoveries made in the field of positron annihilation. Many important new results concerning positron and positronium studies of nano-materials, defects, porous materials, low-k dielectrics, polymers, liquids, atomic physics and new instrumentation are reported in the present contributions; presented by experts from all over the world. There can be no better way of keeping up with this rapidly advancing field.

Research advances in III-nitride semiconductor materials and device have led to an exponential increase in activity directed towards electronic and optoelectronic applications. There is also great scientific interest in this class of materials because they appear to form the first semiconductor system in which extended defects do not severely affect the optical properties of devices. The volume consists of chapters written by a number of leading researchers in nitride materials and device technology with the emphasis on the dopants incorporations, impurities identifications, defects engineering, defects characterization, ion implantation, irradiation-induced defects, residual stress, structural defects and phonon confinement. This unique volume provides a comprehensive review and introduction of defects and structural properties of GaN and related compounds for newcomers to the field and stimulus to further advances for experienced researchers. Given the current level of interest and research activity directed towards nitride materials and devices, the publication of the volume is particularly timely. Early pioneering work by Pankove and co-workers in the 1970s yielded a metal-insulator-semiconductor GaN light-emitting diode (LED), but the difficulty of producing p-type GaN precluded much further effort. The current level of activity in nitride semiconductors was inspired largely by the results of Akasaki and co-workers and of Nakamura and co-workers in the late 1980s and early 1990s in the development of p-type doping in GaN and the demonstration of nitride-based LEDs at visible wavelengths. These advances were followed by the successful fabrication and commercialization of nitride blue laser diodes by Nakamura et al at Nichia. The chapters contained in this volume constitutes a mere sampling of the broad range of research on nitride semiconductor materials and defect issues currently being pursued in academic, government, and industrial laboratories worldwide.