1.1 Preface Organic chemistry had its origin in chemicals which are synthesized by living cells. These chemicals consist of molecules whose skeletons are built up of carbon atoms. The remaining valences are connected with ligands such as hydrogen, halo gens, -OH,==O, -NH . Some of the skeletal carbon atoms can be replaced by non 2 metals such as oxygen, nitrogen, or sulfur {"heteroatoms"}. It is characteristic for the living world, not to be in a crystalline state. However it is possible to obtain single crystals from many organic compounds both of natural and synthetic origin. For a number of years the physics and chem istry of these crystals have stimulated fundamental research on a rapidly growing scale. The great variety of possible organic structures {as compared to inorganics} opens up a large field of new materials and of novel material properties; for previous literature reviews and data compilations see 1-40) and Chap. 6. The art of producing good and pure organic single crystals has developed hand in-hand with the ever growing requirements of basic research, arising from its interest in fundamental interactions in the solid state. Interactions manifest themselves in a very detailed way by energy transfer.

Springer-Verlag, Berlin Heidelberg, in conjunction with Springer-Verlag New York, is pleased to announce a new series: CRYSTALS Growth, Properties, and Applications The series presents critical reviews of recent developments in the field of crystal growth, properties, and applications. A substantial portion of the new series will be devoted to the theory, mechanisms, and techniques of crystal growth. Occasionally, clear, concise, complete, and tested instructions for growing crystals will be published, particularly in the case of methods and procedures that promise to have general applicability. Responding to the ever-increasing need for crystal substances in research and industry, appropriate space will be devoted to methods of crystal characterization and analysis in the broadest sense, even though reproducible results may be expected only when structures, microstructures, and composition are really known. Relations among procedures, properties, and the morphology of crystals will also be treated with reference to specific aspects of their practical application. In this way the series will bridge the gaps between the needs of research and industry, the pos sibilities and limitations of crystal growth, and the properties of crystals. Reports on the broad spectrum of new applications - in electronics, laser tech nology, and nonlinear optics, to name only a few - will be of interest not only to industry and technology, but to wider areas of applied physics as well and to solid state physics in particular. In response to the growing interest in and importance of organic crystals and polymers, they will also be treated.

This textbook provides a basic understanding of the principles of the field of organic electronics through to their applications in organic devices. Useful for the student and practitioner, it is both a teaching text and a resource that is a jumping-off point for learning, working and innovating in this rapidly growing field.--Provided by publisher.

In the first contribution to this volume we read that the world-wide production of single crystal silicon amounts to some 2000 metric tons per year. Given the size of present-day silicon-crystals, this number is equivalent to 100000 silicon-crystals grown every year by either the Czochralski (80%) or the floating-zone (20%) technique. But, to the best of my knowledge, no coherent and comprehensive article has been written that deals with "the art and science", as well as the practical and technical aspects of growing silicon crystals by the Czochralski technique. The same could be said about the floating-zone technique were it not for the review article by W. Dietze, W. Keller and A. Miihlbauer which was published in the preceding Volume 5 ("Silicon") of this series (and for a monograph by two of the above authors published about the same time). As editor of this volume I am very glad to have succeeded in persuading two scien tists, W. Zulehner and D. Huber, of Wacker-Chemitronic GmbH - the world's largest producer of silicon-crystals - to write a comprehensive article about the practical and scientific aspects of growing silicon-crystals by the Czochralski method and about silicon wafer manufacture. I am sure that many scientists or engineers who work with silicon crystals -be it in the laboratory or in a production environment - will profit from the first article in this volume.

1.1 The Role of Silicon as a Semiconductor Silicon is unchallenged as a semiconductor base material in our present electronics indu stry. The reasons why it qualifies so strongly for this particular purpose are manyfold. The attractive combination of physical (electrical) properties of silicon and the unique properties of its native oxide layer have been the original factors for its breathtaking evolution in device technology. The majority of reasons, however, for its present status are correlated with industrial prosessing in terms of charge units ( economy), reliability (reproducibility), and flexibility, but also its availability. The latter point, in particular, plays an important role in the different long-term projects on the terrestrial application of solar cells. Practically inexhaustive resources of silicon dioxide form a sound basis even for the most pretentious programs on future alternatives to relieve the present situation in electrical power generation by photovol taics. Assuming a maximum percentage of 10% to be replaced by the year 2000 would roughly mean a cumulative annual production of 2 million metric tons of crude silicon (based on present solar cell standards)!). To illustrate the orders of magnitude that have to be discussed in pertinent programs: Today, the industrial silicon capacity of non-communistic countries (including ferrosili con and other alloys by their relative Si-content) amounts to some 2 million tons per year.

Science and art of crystal growth represent an interdisciplinary activity based on fundamental principles of physics, chemistry and crystallography. Crystal growth has contributed over the years essentially to a widening of knowledge in its basic disciplines and has penetrated practically into all fields of experimental natural sciences. It has acted, more over, in a steadily increasing manner as a link between science and technology as can be seen best, for example, from the achievements in modern microelectronics. The aim of the course "Crystal Growth in Science and Technology" being to stress the interdisciplinary character of the subject, selected fundamental principles are reviewed in the following contributions and cross links between basic and applied aspects are illustrated. It is a very well-known fact that the intensive development of crystal growth has led to a progressive narrowing of interests in highly specialized directions which is in particular harmful to young research scientists. The organizers of the course did sincerely hope that the program would help to broaden up the horizon of the participants. It was equally their wish to contribute within the traditional spirit of the school of crystallography in Erice to the promotion of mutual understanding, personal friendship and future collaboration between all those who were present at the school.

Hydrothermal and Supercritical Water Processes presents an overview on the properties and applications of water at elevated temperatures and pressures. It combines fundamentals with production process aspects. Water is an extraordinary substance. At elevated temperatures (and pressures) its properties change dramatically due to the modifications of the molecular structure of bulk water that varies from a stable three-dimensional network, formed by hydrogen bonds at low and moderate temperatures, to an assembly of separated polar water molecules at high and supercritical temperatures. With varying pressure and temperature, water is turned from a solvent for ionic species to a solvent for polar and non-polar substances. This variability and an enhanced reactivity of water have led to many practical applications and to even more research activities, related to such areas as energy transfer, extraction of functional molecules, unique chemical reactions, biomass conversion and fuel materials processing, destruction of dangerous compounds and recycling of useful ones, growth of monolithic crystals, and preparation of metallic nanoparticles. This book provides an introduction into the wide range of activities that are possible in aqueous mixtures. It is organized to facilitate understanding of the main features, outlines the main applications, and gives access to further information - Summarizes fundamental properties of water for engineering applications - Compares process and reactor designs - Evaluates processes from thermodynamic, economic, and social impact viewpoints