Diese Arbeit beschreibt die Entwicklung einer Technologie für die Herstellung hochqualitativer sub-μm Nb/Al-AlOx/Nb-Josephson-Kontakte. Mit den dadurch entstandenen Bauteilen wurden verschiedene experimentell zuvor noch nicht beobachtete makroskopische Quanteneffekte nachgewiesen. Weiterhin wurden Nb-basierte Phasen-Qubits entworfen, hergestellt und gemessen, die längere Kohärenzzeiten als vergleichbare Bauelemente aus der Literatur aufweisen.

This book summarizes the history and present status and applications of Josephson junctions. These devices are leading elements in superconducting electronics and provide state-of-the-art performance in detection of small magnetic fields and currents, in several digital computing methods, and in medical diagnostic devices and now provide voltage standards used worldwide. Astronomical infrared (IR) telescopes, including the South Pole Telescope, use these junctions in combinations called superconducting quantum interference devices (SQUIDs).

This two-volume handbook offers a comprehensive and well coordinated presentation of SQUIDs (Superconducting Quantum Interference Devices), including device fundamentals, design, technology, system construction and multiple applications. It is intended to bridge the gap between fundamentals and applications, and will be a valuable textbook reference for graduate students and for professionals engaged in SQUID research and engineering. It will also be of use to specialists in multiple fields of practical SQUID applications, from human brain research and heart diagnostics to airplane and nuclear plant testing to prospecting for oil, minerals and buried ordnance. The first volume contains chapters presenting the theory of SQUIDs, their fabrication from low- and high-temperature superconductors, the necessary readout electronics, and the design and performance of practical direct current (dc) and radio-frequency (rf) SQUIDs. This volume concludes with an overview of the most important SQUID system issues. An appendix summarizes briefly the foundations of superconductivity that are necessary to understand SQUIDs. A glossary and tables of units and constants are also included. The second volume of the handbook will deal with applications of SQUIDs and SQUID systems.

This wide-ranging presentation of applied superconductivity, from fundamentals and materials right up to the details of many applications, is an essential reference for physicists and engineers in academic research as well as in industry. Readers looking for a comprehensive overview on basic effects related to superconductivity and superconducting materials will expand their knowledge and understanding of both low and high Tc superconductors with respect to their application. Technology, preparation and characterization are covered for bulk, single crystals, thins fi lms as well as electronic devices, wires and tapes. The main benefit of this work lies in its broad coverage of significant applications in magnets, power engineering, electronics, sensors and quantum metrology. The reader will find information on superconducting magnets for diverse applications like particle physics, fusion research, medicine, and biomagnetism as well as materials processing. SQUIDs and their usage in medicine or geophysics are thoroughly covered, as are superconducting radiation and particle detectors, aspects on superconductor digital electronics, leading readers to quantum computing and new devices.

The on-going developments, and the recent achievements of the superconducting electronics (especially in the field of Josephson junctions and the inherent nonlinear dynamics) inspired us to organize a conference where different groups working on the subject could meet and discuss the latest results of their investigations. This idea was realized as two joint workshops, the NATO Advanced Research Workshop on Superconducting Electronics with Prof. N.F. Pedersen as chairman, and the 2nd Workshop on Josephson Devices, with Profs. G. Costabile and M. Russo as chairmen, held in Capri, Italy on September 3-7, 1990. The Workshops were very successful. About 70 scientists from 12 countries (Denmark, France, Germany, Greece, Italy, Japan, People's Republic of China, Sweden, United Kingdom, USA, USSR, and Venezuela) enjoyed the many interesting and mostly informal occasions for scientific exchanges as well as the very pleasant weather of Southern Italy. We are very grateful to the Institutions which made possible the realization and the success of the conference with their financial support : NATO Science Committee through the NATO International Scientific Exchange Programmes, University of Salerno, and Istituto di Cibernetica of the Consiglio Nazionale delle Ricerche (C.N.R.) of Italy. The conference was held under the auspices of the Progetto Finalizzato "Superconductive and Cryogenic Technologies" of C.N.R. Finally special thanks go to our Conference Secretary Anna Maria Mazzarella for carrying out most of the organizative work, and for her continuous "on stage" support in solving all the problems which inevitably arise in such occasions.

Recent research on superconductors with high critical temperature has led to results that were not available when the original German edition was prepared but could be included in the present English edition. This concerns materials based on bismuth and thallium, as well as measurements of low microwave loss. The author would like to thank Mr. A. H. Armstrong for translating the book from German to English in a very dedicated and competent manner. Thanks are also due once again to Springer-Verlag for their generous support and cordial cooperation. Bad Salzdetfurth September 1989 Johann H. Rinken Preface to the German Edition The development of materials which lose their electrical resistance when cooled, even before reaching the boiling point of liquid nitrogen, has considerably in creased the interest in superconductor technology, and with it superconductor electronics. This development had not been foreseen when work on the present book started, just over a year ago. Nevertheless, recent results of research on materials with high critical temperature are included to the extent that they seem to be confirmed and to be of interest to superconductor electronics. The present book deals with the physical and technological foundations of superconductor electronics so far as they must be known in order to under stand the principal modes of operation of superconductor electronics components.

This volume is based on the proceedings of the NATO-sponsored Advanced Studies Institute (ASn on The New Superconducting Electronics (held 9-20 August 1992 in Waterville Valley, New Hampshire USA). The contents herein are intended to provide an update to an earlier volume on the same subject (based on a NATO ASI held in 1988). Four years seems a relatively short time interval, and our title itself, featuring The New Superconducting Electronics, may appear somewhat pretentious. Nevertheless, we feel strongly that the ASI fostered a timely reexamination of the technical progress and application potential of this rapid-paced field. There are, indeed, many new avenues for technological innovation which were not envisioned or considered possible four years ago. The greatest advances by far have occurred with regard to oxide superconductors, the so-called high transition-temperature superconductors, known in short as HTS. These advances are mainly in the ability to fabricate both (1) high-quality, relatively large-area films for microwave filters and (2) multilayer device structures, principally superconducting-normal-superconducting (SNS) Josephson junctions, for superconducting-quantum-interference-device (SQUID) magnetometers. Additionally, we have seen the invention and development of the flux-flow transistor, a planar three-terminal device. During the earlier ASI only the very first HTS films with adequate critical-current density had just been fabricated, and these were of limited area and had high resistance for microwave current.

High temperature superconducting (HTS) bulks and stacks of coated conductors can be magnetized to become trapped-field magnets that provide much stronger magnetic fields than those reachable with conventional permanent magnets. This work investigates the flux dynamics during the magnetization of HTS trapped-field magnets and proposes possible strategies to improve the trapped field produced by the pulsed field magnetization method that is promising for practical applications.

Within this book fabrication processes for high-quality Josephson junctions based on niobium and aluminum oxide as well as niobium nitride and aluminum nitride on various substrates are discussed. Techniques for achieving a planar chip topography and sub-μm lateral dimensions, aiding the realization of sophisticated Josephson devices such as SQUIDs, flux-flow oscillators and long Josephson junctions with artificial phase discontinuities, are presented in detail.