The fundamental concept of quantum coherence plays a central role in quantum physics, cutting across disciplines of quantum optics, atomic and condensed matter physics. Quantum coherence represents a universal property of the quantum s- tems that applies both to light and matter thereby tying together materials and p- nomena. Moreover, the optical coherence can be transferred to the medium through the light-matter interactions. Since the early days of quantum mechanics there has been a desire to control dynamics of quantum systems. The generation and c- trol of quantum coherence in matter by optical means, in particular, represents a viable way to achieve this longstanding goal and semiconductor nanostructures are the most promising candidates for controllable quantum systems. Optical generation and control of coherent light-matter states in semiconductor quantum nanostructures is precisely the scope of the present book. Recently, there has been a great deal of interest in the subject of quantum coh- ence. We are currently witnessing parallel growth of activities in different physical systems that are all built around the central concept of manipulation of quantum coherence. The burgeoning activities in solid-state systems, and semiconductors in particular, have been strongly driven by the unprecedented control of coherence that previously has been demonstrated in quantum optics of atoms and molecules, and is now taking advantage of the remarkable advances in semiconductor fabrication technologies. A recent impetus to exploit the coherent quantum phenomena comes from the emergence of the quantum information paradigm.

Thermoelectric devices could play an important role in making efficient use of our energy resources but their efficiency would need to be increased for their wide scale application. There is a multidisciplinary search for materials with an enhanced thermoelectric responses for use in such devices. This volume covers the latest ideas and developments in this research field, covering topics ranging from the fabrication and characterization of new materials, particularly those with strong electron correlation, use of nanostructured, layered materials and composites, through to theoretical work to gain a deeper understanding of thermoelectric behavior. It should be a useful guide and stimulus to all working in this very topical field.

The Advanced Research Workshop on the Physical Properties of Semiconductor Interfaces at the Sub-Nanometer Scale was held from 31 August to 2 September, 1992, in Riva del Garda. Italy. The aim of the workshop was to bring together experts in different aspects of the study of semiconductor interfaces and in small-scale devices where the interface properties can be very significant It was our aim that this would help focus research of the growth and characterization of semiconductor interfaces at the atomic scale on the issues that will have the greatest impact on devices of the future. Some 30 participants from industrial and academic research institutes and from 11 countries contributed to the workshop with papers on their recent wode. . 'There was ample time for discussion after each talk. as well as a summary discussion at the end of the meeting. The major themes of the meeting are described below. The meeting included several talks relating to the different growth techniques used in heteroepitaxial growth of semiconductors. Horikoshi discussed the atomistic processes involved in MBE, MEE and MOCVD, presenting results of experimental RHEED and photoluminescence measurements; Foxon compared the merits of MBE, MOCVD, and eBE growth; Molder described RHEED studies of Si/Ge growth by GSMBE, and Pashley discussed the role of surface reconstructions in MBE growth as seen from STM studies on GaAs. On the theoretical side, Vvedensky described several different methods to model growth: molecular dynamics, Monte Carlo techniques, and analytic modeling.

The drive toward new semiconductor technologies is intricately related to market demands for cheaper, smaller, faster, and more reliable circuits with lower power consumption. The development of new processing tools and technologies is aimed at optimizing one or more of these requirements. This goal can, however, only be achieved by a concerted effort between scientists, engineers, technicians, and operators in research, development, and manufac turing. It is therefore important that experts in specific disciplines, such as device and circuit design, understand the principle, capabil ities, and limitations of tools and processing technologies. It is also important that those working on specific unit processes, such as lithography or hot processes, be familiar with other unit processes used to manufacture the product. Several excellent books have been published on the subject of process technologies. These texts, however, cover subjects in too much detail, or do not cover topics important to modem tech nologies. This book is written with the need for a "bridge" between different disciplines in mind. It is intended to present to engineers and scientists those parts of modem processing technologies that are of greatest importance to the design and manufacture of semi conductor circuits. The material is presented with sufficient detail to understand and analyze interactions between processing and other semiconductor disciplines, such as design of devices and cir cuits, their electrical parameters, reliability, and yield."

This book focuses on the importance of mobile ions presented in oxide structures, what significantly affects the metal-oxide-semiconductor (MOS) properties. The reading starts with the definition of the MOS structure, its various aspects and different types of charges presented in their structure. A review on ionic transport mechanisms and techniques for measuring the mobile ions concentration in the oxides is given, special attention being attempted to the Charge Pumping (CP) technique associated with the Bias Thermal Stress (BTS) method. Theoretical approaches to determine the density of mobile ions as well as their distribution along the oxide thickness are also discussed. The content varies from general to very specific examples, helping the reader to learn more about transport in MOS structures.

The book is based on the lectures given at the CIME school "Quantum many body systems" held in the summer of 2010. It provides a tutorial introduction to recent advances in the mathematics of interacting systems, written by four leading experts in the field: V. Rivasseau illustrates the applications of constructive Quantum Field Theory to 2D interacting electrons and their relation to quantum gravity; R. Seiringer describes a proof of Bose-Einstein condensation in the Gross-Pitaevski limit and explains the effects of rotating traps and the emergence of lattices of quantized vortices; J.-P. Solovej gives an introduction to the theory of quantum Coulomb systems and to the functional analytic methods used to prove their thermodynamic stability; finally, T. Spencer explains the supersymmetric approach to Anderson localization and its relation to the theory of random matrices. All the lectures are characterized by their mathematical rigor combined with physical insights.

Chapter I describes deposition as a basic microelectronics technique. Plasma enhanced chemical vapor deposition (PECVD) is a technique widely accepted in microelectronics for the deposition of amorphous dielectric films such as silicon nitride and silicon oxide. The main advantage of PECVD stems from the intro duction of plasma energy to the CVD environment, which makes it possible to promote chemical reactions at relatively low temperatures. A natural extension of this is to use this plasma energy to lower the temperature required to obtain a crystalline deposit. This chapter discusses the PECVD technique and its ap plication to the deposition of dielectric, semiconductor, and conductor films of interest to microelectronics. Chapter 2 acquaints the reader with the technology and capabilities of plasma processing. Batch etching reactors and etching processes are approaching ma turity after more than ten years of development. Requirements of anisotropic and selective etching have been met using a variety of reactor configurations and etching gases. The present emphasis is the integration of plasma etching processes into the overall fabrication sequence. Chapter 3 reviews recent advances in high pressure oxidation technology and its applications to integrated circuits. The high pressure oxidation system, oxi dation mechanisms, oxidation-induced stacking faults, impurity segregation, and oxide quality are described. Applications to bipolar and MOS devices are also presented."

Stochastic Energetics by now commonly designates the emerging field that bridges the gap between stochastic dynamical processes and thermodynamics. Triggered by the vast improvements in spatio-temporal resolution in nanotechnology, stochastic energetics develops a framework for quantifying individual realizations of a stochastic process on the mesoscopic scale of thermal fluctuations. This is needed to answer such novel questions as: Can one cool a drop of water by agitating an immersed nano-particle? How does heat flow if a Brownian particle pulls a polymer chain? Can one measure the free-energy of a system through a single realization of the associated stochastic process? This book will take the reader gradually from the basics to the applications: Part I provides the necessary background from stochastic dynamics (Langevin, master equation), Part II introduces how stochastic energetics describes such basic notions as heat and work on the mesoscopic scale, Part III details several applications, such as control and detection processes, as well as free-energy transducers. It aims in particular at researchers and graduate students working in the fields of nanoscience and technology.

Semiconductors have been used widely in signal-level or "brain" applications. Since their invention in 1948, transistors have revolutionized the electronics industry in computers, information processing, and communications. Now, however, semiconductors are being used more and more where consid erable "brawn" is required. Devices such as high-power bipolar junction tran sistors and power field-effect transistors, as well as SCRs, TRlACs, GTOs, and other semiconductor switching devices that use a p-n-p-n regenerative effect to achieve bistable action, are expanding the power-handling horizons of semicon ductors and finding increasing application in a wide range of products including regulated power supplies, lamp dimmers, motor drives, pulse modulators, and heat controls. HVDC and electric-vehicle propulsion are two additional areas of application which may have a very significant long range impact on the tech nology. The impact of solid-state devices capable of handling appreciable power levels has yet to be fully realized. Since it first became available in late 1957, the SCR or silicon-controlled rec tifier (also called the reverse blocking triode thyristor) has become the most popular member of the thyristor family. At present, SCRs are available from a large number of manufacturers in this country and abroad. SCR ratings range from less than one ampere to over three thousand amperes with voltage ratings in excess of three thousand volts."

Since its invention in 1962, the semiconductor laser has come a long way. Advances in material purity and epitaxial growth techniques have led to a variety of semiconductor lasers covering a wide wavelength range of 0. 3- 100 ILm. The development during the 1970s of GaAs semiconductor lasers, emitting in the near-infrared region of 0. 8--0. 9 ILm, resulted in their use for the first generation of optical fiber communication systems. However, to take advantage of low losses in silica fibers occurring around 1. 3 and 1. 55 ILm, the emphasis soon shifted toward long-wavelength semiconductor lasers. The material system of choice in this wavelength range has been the quaternary alloy InGaAsP. During the last five years or so, the intense development effort devoted to InGaAsP lasers has resulted in a technology mature enough that lightwave transmission systems using InGaAsP lasers are currently being deployed throughout the world. This book is intended to provide a comprehensive account of long-wave length semiconductor lasers. Particular attention is paid to InGaAsP lasers, although we also consider semiconductor lasers operating at longer wave lengths. The objective is to provide an up-to-date understanding of semicon ductor lasers while incorporating recent research results that are not yet available in the book form. Although InGaAsP lasers are often used as an example, the basic concepts discussed in this text apply to all semiconductor lasers, irrespective of their wavelengths.

Since the discovery of superconductivity in 1911 by H. Kamerlingh Onnes, of the order of half a billion dollars has been spent on research directed toward understanding and utiliz ing this phenomenon. This investment has gained us fundamental understanding in the form of a microscopic theory of superconduc tivity. Moreover, superconductivity has been transformed from a laboratory curiosity to the basis of some of the most sensitive and accurate measuring devices known, a whole host of other elec tronic devices, a soon-to-be new international standard for the volt, a prototype generation of superconducting motors and gener ators, and magnets producing the highest continuous magnetic fields yet produced by man. The promise of more efficient means of power transmission and mass transportation, a new generation of superconducting motors and generators, and computers and other electronic devices with superconducting circuit elements is all too clear. The realization of controlled thermonuclear fusion is perhaps totally dependent upon the creation of enormous magnetic fields over large volumes by some future generation of supercon ducting magnets. Nevertheless, whether or not the technological promise of superconductivity comes to full flower depends as much, and perhaps more, upon economic and political factors as it does upon new technological and scientific breakthroughs. The basic science of superconductivity and its technological implications were the subject of a short course on "The Science and Technology of Superconductivity" held at Georgetown University, Washington, D. C., during 13-26 August 1971."

For some time there has been a need for a semiconductor device book that carries diode and transistor theory beyond an introductory level and yet has space to touch on a wider range of semiconductor device principles and applica tions. Such topics are covered in specialized monographs numbering many hun dreds, but the voluminous nature of this literature limits access for students. This book is the outcome of attempts to develop a broad course on devices and integrated electronics for university students at about senior-year level. The edu cational prerequisites are an introductory course in semiconductor junction and transistor concepts, and a course on analog and digital circuits that has intro duced the concepts of rectification, amplification, oscillators, modulation and logic and SWitching circuits. The book should also be of value to professional engineers and physicists because of both, the information included and the de tailed guide to the literature given by the references. The aim has been to bring some measure of order into the subject area examined and to provide a basic structure from which teachers may develop themes that are of most interest to students and themselves. Semiconductor devices and integrated circuits are reviewed and fundamental factors that control power levels, frequency, speed, size and cost are discussed. The text also briefly mentions how devices are used and presents circuits and comments on representative applications. Thus, the book seeks a balance be tween the extremes of device physics and circuit design."

Joseph F. White has studied, worked, and taught in all aspects of microwave semiconductor materials, control diodes, and circuit applications. He is thoroughly grounded in the physics and math ematics of the field, but has primarily the engineer's viewpoint, combining basic knowledge with experience and ingenuity to gen erate practical designs under constraints of required performance and costs of development and production. As a result of his teach ing experience and numerous technical papers and oral presenta tions, he has developed a clear, well-organized writing style that makes this book easy to use as a self-teaching text, a reference volume, and a design handbook. Dr. White believes that an engineer must have a good understand ing of semiconductor physics, a thorough knowledge of microwave circuit theory, at least an elementary acquaintance with transistor drivers, and the ability to check and refine a microwave circuit on a computer terminal to be qualified for modern, creative design of microwave semiconductor control components. These subjects are well covered in approximately the first half of the book; the second half treats the general and specific design of switches, at tenuators, limiters, duplexers, and phase shifters, with many ex amples drawn from his experience and that of others."

IC designers appraise currently MOS transistor geometries and currents to compromise objectives like gain-bandwidth, slew-rate, dynamic range, noise, non-linear distortion, etc. Making optimal choices is a difficult task. How to minimize for instance the power consumption of an operational amplifier without too much penalty regarding area while keeping the gain-bandwidth unaffected in the same time? Moderate inversion yields high gains, but the concomitant area increase adds parasitics that restrict bandwidth. Which methodology to use in order to come across the best compromise(s)? Is synthesis a mixture of design experience combined with cut and tries or is it a constrained multivariate optimization problem, or a mixture? Optimization algorithms are attractive from a system perspective of course, but what about low-voltage low-power circuits, requiring a more physical approach? The connections amid transistor physics and circuits are intricate and their interactions not always easy to describe in terms of existing software packages. The gm/ID synthesis methodology is adapted to CMOS analog circuits for the transconductance over drain current ratio combines most of the ingredients needed in order to determine transistors sizes and DC currents.

The aim of this book is to acquaintthe reader with the phenomenon of sup- conductivity and the high temperature superconductors discovered in 1986 by Bednorz and Muller. Just after this discovery, a lot of research work was carried out by the scientists worldwide over for more than about 10 years. This book describes the superconductivity phenomenon (Chap. 1), the structureofhighT superconductors(Chap.2), thecriticalcurrents(Chap.3), c synthesis of high T superconductors (Chap. 3), the superconductivity in c cuprates (Chap. 4), proximity e?ect and SQUID devices, their design criteria and noise aspects (Chap. 6), theories (Chap. 7) and applications (Chap. 8). TheauthorisgratefultoProfessorO.N.Srivastava, BanarasHinduUniv- sity, VaranasiforvaluableguidanceanddiscussionsduringPh.D.tenureofthe author andalsothankful to Prof.R.S. Tiwari, Dr. K.Ramakrishna, Dr. Balak Das, Dr. K.K. Verma, Dr. G.D. Varma andDr. H.K. Singh, who workedalong with the author during researchat B.H.U., leading to his Ph.D. The author is thankful to Prof. D.P. Tiwari (Head, Physics Department, A.P.S. University, Rewa), Dr. A.P. Mishra and Dr. S.L. Agrawal, Physics Department, A.P.S. University, for boosting the morale. The author is thankful to scientists and researchers whose work/papers have been consulted for preparing the manuscript. Further I wish to express thanks to Mr. Dharmendra Saxena for preparing type-sc

Spin wave theory of magnetism and BCS theory of superconductivity are typical theories of the time before renormalization group (RG) theory. The two theories consider atomistic interactions only and ignore the energy degrees of freedom of the continuous (infinite) solid. Since the pioneering work of Kenneth G. Wilson (Nobel Prize of physics in 1982) we know that the continuous solid is characterized by a particular symmetry: invariance with respect to transformations of the length scale. Associated with this symmetry are particular field particles with characteristic excitation spectra. In diamagnetic solids these are the well known Debye bosons. This book reviews experimental work on solid state physics of the last five decades and shows in a phenomenological way that the dynamics of ordered magnets and conventional superconductors is controlled by the field particles of the infinite solid and not by magnons and Cooper pairs, respectively. In the case of ordered magnets the relevant field particles are called GSW bosons after Goldstone, Salam and Weinberg and in the case of superconductors the relevant field particles are called SC bosons. One can imagine these bosons as magnetic density waves or charge density waves, respectively. Crossover from atomistic exchange interactions to the excitations of the infinite solid occurs because the GSW bosons have generally lower excitation energies than the atomistic magnons. According to the principle of relevance the dynamics is governed by the excitations with the lowest energy. The non relevant atomistic interactions with higher energy are practically unimportant for the dynamics.

The study of cooperative phenomena is one of the dominant features of contem porary physics. Outside physics it has grown to a huge field of interdisciplinary investigation, involving all the natural sciences from physics via biology to socio logy. Yet, during the first few decades following the advent of quantum theory, the pursuit of the single particle or the single atom, as the case may be, has been so fascinating that only a small number of physicists have stressed the importance of collective behaviour. One outstanding personality among these few is Professor HERBERT FROHLICH. He has made an enormous contribution to the modern concept of cooperativity and has stimulated a whole generation of physicists. Therefore, it seemed to the editors very appropriate to dedicate a volume on "cooperative phenomena" to him on the occasion of his official retirement from his university duties. Nevertheless, in the course of carrying out this project, the editors have been somewhat amazed to find that they have covered the essentials of contemporary physics and its im pact on other scientific disciplines. It thus becomes clear how much HERBERT FROHLICH has inspired research workers and has acted as a stimulating discussion partner for others. FROHLICH is one of those exceptional scientists who have wor ked in quite different fields and given them an enormous impetus. Unfortunately, the number of scientists of such distinctive personality has been decreasing in our century."

Electronic Properties of Fullerenes and other Novel Materials gives an overview of the state-of-the-art research. It presents most recent results on preparation, experimental analysis by electron spectroscopy, infrared and Raman spectroscopy, luminescence, and nonlinear optical, as well as possible technological applications. Emphasis is also placed on the superconducting properties of Fullerenes. The introductory and advanced contributions provide a good survey of the current status of this rapidly developing field.

This short Introduction into Space Charge E?ects in Semiconductors is designed for teaching the basics to undergraduates and show how space charges are created in semiconductors and what e?ect they have on the el- tric?eldandthe energybanddistributioninsuchmaterials, andconsequently on the current-voltage characteristics in semiconducting devices. Such space charge e?ects were described previously in numerous books, fromtheclassicsofSpenkeandShockleytothemorerecentonesofSeegerand others.Butmanymoredetailedinformationwereonlyavailableintheoriginal literatureandsomeofthemnotatall.Itseemstobeimportanttocollectallin a comprehensive Text that can be presented to students in Physics, Electrical Engineering, and Material Science to create the fundamental knowledge that is now essential for further development of more sophisticated semiconductor devices and solar cells. This book will go through every aspect of space charge e?ects and - scribe them from simple elementaries to the basics of semiconductor devices, systematically and in progressing detail. For simplicity we have chosen this description for a one-dimensional se- conductorthatpermitsasimpledemonstrationoftheresultsgraphicallywi- out requiring sometimes confusing perspective rendering. In order to clarify the principles involved, the book starts with a hy- thetical model, by assuming simple space charge distributions and deriving their e?ects on ?eld and potential distributions, using the Poisson equation. Itemphasizestheimportantsignrelationsoftheinterreactingvariables, space charge, ?eld, and potential (band edges). It then expands into simple semiconductor models that contain an abrupt nn-junction and gives an example of important space chargelimited currents, + as observed in nn -junction

Semiconductor lithography is one of the key steps in the manufacturing of integrated silicon-based circuits. In fabricating a semiconductor device such as a transistor, a series of hot processes consisting of vacuum film deposition, oxidations, and dopant implantation are all patterned into microscopic circuits by the wet processes of lithography. Lithography, as adopted by the semiconductor industry, is the process of drawing or printing the pattern of an integrated circuit in a resist material. The pattern is formed and overlayed to a previous circuit layer as many as 30 times in the manufacture of logic and memory devices. With the resist pattern acting as a mask, a permanent device structure is formed by subtractive (removal) etching or by additive deposition of metals or insulators. Each process step in lithography uses inorganic or organic materials to physically transform semiconductors of silicon, insulators of oxides, nitrides, and organic polymers, and metals, into useful electronic devices. All forms of electromagnetic radiation are used in the processing. Lithography is a mUltidisciplinary science of materials, processes, and equipment, interacting to produce three-dimensional structures. Many aspects of chemistry, electrical engineering, materials science, and physics are involved. The purpose of this book is to bring together the work of many scientists and engineers over the last 10 years and focus upon the basic resist materials, the lithographic processes, and the fundamental principles behind each lithographic process.

The occurrence of superconductivity among the d- and f-band metals remains one of the unsolved problems of physics. The first Rochester conference on this subject in October 1971 brought together approximately 100 experimentalists and theorists, and that conference was considered successful; the published proceedings well-represented the current research at that time and has served as a "handbook" to many. In the four and one half years since the first conference, impressive progress has been made in many areas (although Berndt Matthias would be one of the first to point out that raising the m"aximum transition temperature by a significant amount was not one of them). For a variety of reasons, I decided that it was time for a Second Rochester Conference on Superconductivity in d- and f-Band Metals and it was held on April 30 and May 1, 1976. It would appear that this conference was even more successful judging from the quality of the talks and various comments made to me. I believe that this was due to the fact that the subject matter is exciting and that the timing was particularly appropriate for several areas of research that were discussed. However, I cannot rule out other factors such as the one advanced humorously by J.

Five years have passed since the breakthrough in the critical temperature for superconductors. During this period, many superconducting materials have been discovered and developed, and our knowledge of the physical and other properties of oxide superconductors has deepened through extensive and intensive research. This knowledge has advanced superconductivity science and technology from the initial questioning stage to a more developed but still uncertain second stage where research activity in superconductivity now overlaps with fields of application. Generally speaking, science resonates with technology. Science not only complements but also competes with or stimulates technology. New scientific knowledge has triggered the second technological research stage. Much progress has been made in the development of practical devices, encouraging the application of superconductors in areas such as human levitation, a high speed levitated bearing, large current transforming leads, and high frequency devices. This technological progress has increased our understanding of the science involved, such as flux pinning and dynamics, and anomalous long-range superconducting interactions. At this important stage, international cooperation and collaborative projects can effectively sustain aggressive research and development in order to advance superconductivity to the next stages. The ISS Symposium is expected to serve as a venue for increasing our knowledge of superconductivity and for exchanging visions for future research and applications, through the presentation and discus of the latest research results. These proceedings also aim to summarize sion annual progress in high-Tc superconductivity in all fields."

Polymer semiconductor is the only semiconductor that can be processed in solution. Electronics made by these flexible materials have many advantages such as large-area solution process, low cost, and high performance. Researchers and companies are increasingly dedicating time and money in polymer electronics. This book focuses on the fundamental materials and device physics of polymer electronics. It describes polymer light-emitting diodes, polymer field-effect transistors, organic vertical transistors, polymer solar cells, and many applications based on polymer electronics. The book also discusses and analyzes in detail preparation techniques and device properties of polymer electronics.

This monographdeals with metastable states in amorphoussemiconductors- ma- rials which lack long-range periodicity in the atoms' positions, which are in th- modynamic nonequilibrium and which, in addition, have several metastable states. Thesestates giverise tovariouspropertiesandeffects- namelya widerangeofp- toinduced changes and high photosensitivity and X-ray sensitivity - that are unique among solid-state semiconductors.Historically, amorphousselenium and seleni- based materials have played an important role in physics and technology, and they continue to do so. In these materials there exist inherent intermediate (metastable) states, structural and electronic in origin, which lead to interesting properties and effects different from those of their crystalline counterparts. In this volume, the metastable states and related effects are investigated in depth against the background of a detailed consideration of local atomic and electronic structure, and taking into account a wide range of light-induced effects. Although the rst publications on amorphous semiconductors date back to the early 1970s, studies of metastable states in these materials had not been analyzed systematically up to now, which led to erroneous ideas, even among specialists. In the present book, experimental investigations of metastable states are reported in detail for elemental selenium and selenium-based materials.

While basic features of polarons were well recognized a long time ago and have been described in a number of review papers and textbooks, interest in the role of electron-phonon interactions and polaron dynamics in di?- ent materials has recently gone through a vigorous revival. Electron-phonon interactions have been shown to be relevant in many inorganic and organic semiconductors and polymers, colossal magnetoresistance oxides, and tra- port through nanowires and quantum dots also often depends on vibronic displacements of ions. These interactions presumably play a role in hi- temperature superconductors as well. The continued interest in polarons extends beyond the physical description of advanced materials. The ?eld has been a testing ground for analytical, semi-analytical, and numerical techniques, such as path integrals, strong-coupling perturbation expansion, advanced variational methods, exact diagonalization, Quantum Monte Carlo, and other techniques. This book reviews some recent developments in the ?eld of polarons, starting with the basics and covering a number of active directions of research. Single- and multipolaron theories have o?ered more insight into colossal magnetoresistance and in a broad spectrum of ph- ical properties of structures with reduced dimension and dimensionality such as transport, optical absorption, Raman scattering, photoluminescence, magneto-optics, etc. While nobody - at present - has a ?nal theory of hi- temperature superconductivity, we discuss one alternative (polaronic) route. We have bene?ted from discussions with many experts in the ?eld.