bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diamond-Based Field-Emission Displays
Authors: Jaskie James E. 
Published: August 2016

Diamond has existed in the natural state for thousands of years. It was mainly used as a jewel for its optical brilliance and for its hardness. In the 1950s methods were developed to fabricate synthetic diamonds commercially. This greatly increased diamond's industrial use, mostly for grinding and lapping applications. Diamond is a crystalline form of carbon, a group-IV element in the periodic table. Silicon and germanium are also Group-IV elements and also have the same crystalline lattice structure as diamond. Hence there has been theoretical interest in diamond's electronic properties since the beginning of the semiconductor age. However the cost and poor crystalline quality of both natural and synthetic diamond have precluded any real industrial interest in diamond as an electronic material. Methods of low-temperature and low-pressure diamond-film deposition, developed initially by the Russians in the 1950s and 1960s (and thence by the Japanese, and eventually by others) has made it possible to use this exotic material as an electronic substrate.Diamond, in single-crystalline, polycrystalline, and diamondlike carbon (DLC) forms, is a material with many unusual properties. It is the hardest naturally occurring material, the most thermally conductive, and the most transparent. It also has the slickness of Teflon. In regard to many physical properties, it is at the extreme end of the scale. One of the more unusual and important properties that it possesses is its presentation of a rather small barrier to the emission of electrons into a vacuum.
Materials for Magnetic-Tape Media
Authors: Onodera Seiichi , Kondo Hirofumi , Kawana Takahiro 
Published: August 2016

Magnetic recording has been responsible for the widespread and inexpensive recording of sound and video. Despite the availability of other means of storing data, such as optical recording and semiconductor devices, flexible magnetic-recording media have advantages such as (1) low cost, (2) stable storage, (3) a relatively high data rate, (4) a relatively short seek time, and (5) high-volumetric information density.The first commercially available magnetic-recording tapes were produced in 1947 by the 3M Company. Since that time, magnetic tapes have developed rapidly for use in audio, video, and digital-data recording systems.The linear-analogue technique is commonly used for most audio recorders. The magnetic tape is transported at a speed of several cm/s over a stationary head. On the other hand, helical-scanning rotary heads were developed for video recording, which afforded a high head-to-tape speed of more than several m/s and high recording-density capabilities. However high relative speed causes wear of the tape. The success of a tape in actual use depends critically on its tribological properties.Magnetic media are divided into two groups: (1) particulate media where magnetic particles are dispersed in a polymer binder with some additives and coated onto the substrate and (2) thin-film media in which monolithic, magnetic thin films are deposited onto the substrate in vacuum. The overwhelming preponderance of media fabricated to date have been coated media. However continuous demand for increasingly higher recording density has led to thin-film media.
Mesoscopic Disorder
Authors: Weitz D.A. 
Published: August 2016

Disorder characterizes most of the materials that surround us in nature. Despite their great technological importance, materials with ordered crystalline structures are relatively rare. Examples of disordered materials, however, abound, and their forms can be as varied as their number. The paper on which these words are printed has a disordered structure composed of a highly interconnected network of fibers. It has also been coated with particulate materials to improve its properties and the visibility of the ink. The reading glasses you may require to focus on these words are composed of a glass or polymer material that is disordered on a molecular level. Even the structure of your hand holding this magazine is disordered. These and virtually all other disordered materials are typically parameterized by a characteristic length scale. Above this length scale, the material is homogeneous and the effects of the disorder are not directly manifest; below this characteristic length the disorder of the structure dominates, directly affecting the properties.The range of characteristic length scales for the disordered materials around us is immense. For the glass or polymer of your reading glasses, it is microscopic; the disorder is apparent only at the molecular level, while above this level the material is homogeneous. For the paper on which this magazine is printed, the scale is larger; the paper is white partly because the disordered fiber network has within it structures that are comparable in size to the wavelength of light, resulting in strong scattering of the light.
In Situ Observations of Misfit Dislocations in Lattice-Mismatched Epitaxial Semiconductor Heterostructures
Authors: Hull Robert , Bean John 
Published: August 2016

This article describes the application of transmission electron microscopy (TEM) to real-time, in situ dynamic observations of dislocations in strained epitaxial semiconductor heterostructures. Such experiments allow us to directly observe the formation, motion, and interaction of mis-fit dislocations. Preliminary extension of this work to the in situ measurement of the electrical properties of misfit dislocations will also be described.The Fundamental Scientific IssueIt is well established that it is possible to grow a thin, coherent epitaxial layer on a substrate with a slightly different lattice parameter, as illustrated in Figure la. This concept is known as strained layer epitaxy. In the fields of semiconductor physics and device design, strained layer epitaxy offers many exciting new opportunities (see Reference 1 for a review). A coherently strained structure, however, will store an enormous elastic strain energy density in the epitaxial layer, due to the distortion of interatomic bonds. Therefore, as the epitaxial layer increases in thickness during growth, it will become increasingly energetically favorable to relax this strain energy. A number of relaxation routes exist: (1) roughening of the epitaxial layer surface (see, for example, Reference 2); (2) interdiffusion of the layers (this will generally only be significant at temperatures which are a large fraction of the layer melting temperatures (e.g., Reference 3)); and (3) introduction of a dislocation network into the substrate/epilayer interface, which as shown schematically in Figure lb, will allow the epitaxial layer to relax toward its bulk lattice parameter. This dislocation mechanism is the most prevalent strain relaxation mechanism at typical crystal growth and processing temperatures, and we concentrate on this mechanism in our experimental studies.
Visualization of Dynamic Near-Surface Processes
Authors: Twesten Ray D. , Gibson J. Murray , Ross Frances M. 
Published: August 2016

Electron microscopy has played an undeniably important role in the development and understanding of new materials. One particular method, plan-view transmission electron microscopy (TEM), has been used to reveal many aspects of materials and to help answer questions that are not accessible by other methods. In planview TEM, materials are studied either by the image contrast caused by diffraction or by direct diffraction analysis. The studies are often at a somewhat lower resolution than is possible with some other electron-based microscopies or, in the case of diffraction, must be interpreted in terms of an average effect. Nevertheless, plan-view TEM is very useful because properties at these intermediate length scales typically determine important materials characteristics. It is plan-view microscopy that gives us the big picture of what is happening in a material.Until recently, TEM studies of materials have entailed comparing samples taken at various stages of processing and trying to observe and understand the mechanisms that determine the material behavior. With the advent of controllable specimen environments, materials processing has been taken into the TEM, allowing direct observation of the microstructural development. Here we will focus particularly on surface and near-surface processes, such as oxidation.
Photovoltaic Efficiency Measurements
Authors: Emery Keith 
Published: August 2016

A variety of performance indicators have been employed by the photovoltaic (PV) community to rate the performance of PV cells, modules, and arrays. The PV power conversion efficiency under a set of standard reporting conditions serves as a basis for meaningful comparisons of PV performance, within and among PV technologies. PV efficiency is defined as 100 times the maximum PV electrical power density produced divided by the incident light power at a reference PV temperature, total irradiance, and spectral irradiance. Standard reporting conditions commonly used by the PV community are summarized in Table I.The direct and global reference spectra were generated by a comprehensive Monte-Carlo computer model and actually integrate to 768 W m−2 and 964 W m−2. The terrestrial PV community has arbitrarily assigned a 1-sun total irradiance of 1,000 W m−2 for the global and direct reference spectra. The term “direct” in Table I refers to the direct-normal (5° field of view about the sun) component of the global spectral irradiance distribution. The term “global” in Table I refers to the spectral irradiance distribution on a 37-tilted south-facing surface with a solar zenith angle of 48.2° (AM1.5). The terms AM1 or AM1.5 are often used to refer to standard spectra, but the relative optical air mass (AM) is a geometrical quantity and can be obtained by taking the secant of the angle between the sun and the zenith.
Structural Evaluation and Molecular Control of Vacuum-Evaporated Organic Thin Films
Authors: Matsushige Kazumi 
Published: August 2016

Recently, organic molecules and their complexes with inorganic or metallic materials have drawn many researchers' interest as candidate materials for nanoscale electronic devices of the next generation, especially since Carter's proposal on molecular electronic devices (MEDs) with the functions of gating, switching, memory, etc. in one molecule. However, in order to build such nanoscopic organic electronic devices to replace conventional silicon-based inorganic devices, one must determine how to produce such nanoscale devices and to recognize the electronic states of a single molecule.The scanning tunneling microscope (STM) developed by G. Binning and H. Rohrer made it possible to visualize atoms and molecules in real space under various atmospheres. In addition, STMs can be used as nanoscopic tools for manipulation of individual atoms and molecules, thus realizing MEDs and nanotechnology.In this article, we present our recent achievements concerning the STM as well as in situ x-ray diffraction studies on the molecular structure of ultrathin films prepared by vacuum evaporation. STM observations with atomic resolution reveal the mechanism of nuclei formation and the crystal-growth process in organic molecules. Computer simulations based on STM images of polar organic molecules with electronic dipoles have elucidated the role of electronic interaction for their aggregation structures.Also, nanometer-sized molecular memory can be created by applying an electronic pulse to the evaporated organic films through the STM tip. Furthermore, we discuss the principle of a newly developed in situ total reflection x-ray diffraction (TRXD) apparatus and its application to the evaluation of crystal structure and molecular orientation in organic thin films during the evaporation process, particularly in regard to the role of the substrate, that is, epitaxial growth on organic molecular crystals.
Materials Science in High Magnetic Fields
Authors: Crow J.E. , Parkin D.M. , Sullivan N.S. 
Published: August 2016

The recent rapid growth in the emerging areas of magnetic and magnet-related materials research and applications has led to worldwide recognition of the increased importance of research and technology using high magnetic fields. New high-field magnet facilities and major upgrades of existing facilities are being planned and implemented by a number of countries, among them Japan, Germany, France, the Netherlands, Belgium, Great Britain, Poland, Australia, and the United States. Over the next ten years, these developments will advance the state of the art in magnet-related materials science and technologies by a significant quantum jump. Support by many of the national agencies and a strong corporate commitment to stimulate rapid growth in the development of capabilities at higher magnetic fields and in related technologies results in part from an awareness of the impact these technologies will have in developing the new emerging industrial technologies of the 21st century.The Francis Bitter National Magnet Laboratory (FBNML) at the Massachusetts Institute of Technology has been one of the pre-eminent facilities in developing and advancing science and technology in high magnetic fields. The new U.S. National High Magnetic Field Laboratory (NHMFL) at Florida State University, at the University of Florida, and at Los Alamos National Laboratory builds on the success of existing facilities. NHMFL will provide the necessary environment to develop the next generation of high magnetic fields: 30–50-tesla continuous fields, 60-tesla quasi-continuous fields, and pulsed fields from 60–1,000 tesla. The ability to develop broad user capabilities at these extreme fields is crucial for the advancement of the frontiers of science and of magnet-related industries.
Environmental Stability of Materials—Issues and Opportunities
Authors: Clark David E. 
Published: August 2016

Professor David Kingery, author of the classic text, Introduction to Ceramics, said it well: “Corrosion, like death and taxes in our existence, is inevitable for all materials.” Metals, ceramics, and polymers all undergo change when exposed to the environment. Metals can exhibit electrochemical corrosion, while ceramics and plastics experience primarily chemical corrosion. Although “corrosion” often is used to describe the environmental stability (or instability) of metals, a host of other definitions have been used to characterize the changes that occur in ceramics and polymers.Definitions can become an issue when scientists from various disciplines work together to solve a problem of national/international importance. One such example involves the description of the surface changes that occur when nuclear waste forms are exposed to an aqueous environment (as might occur in a geological repository). The observed surface changes have been referred to as corrosion, leaching, weathering, degradation, and alteration, to name a few. In early symposia on nuclear waste management, sponsored by the Materials Research Society and the American Ceramic Society, definitions and technical issues were discussed extensively by materials scientists, chemists, physicists, geologists, nuclear engineers, and other professionals. Because of this interdisciplinary interaction, significant advances were made (in spite of disagreements over terminology) in understanding the aqueous alteration of these materials. Much of this knowledge will be useful in other applications where environmental stability is important.Although aqueous alteration is an important concept in materials corrosion, the topic of environmental stability is much broader. Other important subtopics are erosion, thermal stability, oxidation and radiation damage, and molten metal, glass, and salt corrosion. Finally, environmental instability need not always be bad. Indeed, there are numerous processes and products that work only because of the material's instability in specific environments.
The Photovoltaic Challenge
Authors: Sinke Wim C. 
Published: August 2016

The term “solar energy” refers to a wide variety of techniques for using the energy available as sunlight. Well-known examples are active and passive thermal solar energy and photovoltaic solar energy but, strictly speaking, hydropower, wind energy, and biomass are also forms of solar energy. Today, only hydropower is used in significant quantities, covering approximately 6% of the world's energy demand. Traditional use of biomass, mainly in developing countries, accounts for more than 10% of the total energy consumption, but is sometimes left out of statistics because it falls outside the category of organized and commercial use.The global potential for solar energy is huge, since the amount of energy that reaches the earth's surface every year exceeds the total energy consumption by roughly a factor of 10,000. There are, however, various barriers to the large-scale use of solar energy technologies. Most technologies have in common that the power density of the generator is low; in other words, one needs large areas to generate significant amounts of energy. This is especially true for biomass, with typical conversion efficiencies (solar energy to chemical energy) of 1% or less. Further, many solar energy technologies have proved technically feasible, but have yet to be proved economically feasible. Last, but not least, the large-scale use of solar energy requires substantial modification of our global energy supply system, which is based largely on fossil fuels.
Quantum-Well Solar Cells
Authors: Barnham Keith , Barnes Jenny , Haarpaintner Guido , Nelson Jenny , Paxman Mark , Foxon Tom , Roberts John 
Published: August 2016

The best present-day single-bandgap solar cells have efficiencies around 20–25%. However, the Carnot efficiency of the earth-sun system is 95%, so there is considerable potential for improvement. The fundamental efficiency limitation in a conventional solar cell results from the tradeoff between a low bandgap which maximizes light absorption and hence output current and a high bandgap which maximizes output voltage. As a result, the maximum theoretical efficiency of a conventional solar cell is around 30% in unconcentrated sunlight at a bandgap close to that of GaAs.The quantum-well solar cell is a novel approach to higher efficiency. In its simplest form, shown in Figure 1, it consists of a multiquantum-well (MQW) system in the undoped region of a p-i-n solar cell. For light with energy greater than the band-gap Eg, the quantum-well cell behaves like a conventional cell. However, light with energy below Eg can be absorbed in the quantum wells. Our studies show that if the material quality is good, the electrons and holes escape from the wells and contribute to a higher output current at a voltage between that of the barrier and well material. In AlGaAs/GaAs test devices, we have obtained efficiency enhancements of a factor of more than two when cells with quantum wells are compared with identical cells without wells.The structure in Figure 1 is, of course, essentially similar to the MQW photodiode or modulator structure that operates in reverse bias, and the quantum-well laser that operates in forward bias beyond flat band.
Phenomenological Modeling of Fusion Welding Processes
Authors: David S.A. , DebRoy T. , Vitek J.M. 
Published: August 2016

Welding is utilized in 50% of the industrial, commercial, and consumer products that make up the U.S. gross national product. In the construction of buildings, bridges, ships, and submarines, and in the aerospace, automotive, and electronic industries, welding is an essential activity. In the last few decades, welding has evolved from an empirical art to a more scientifically based activity requiring synthesis of knowledge from various disciplines. Defects in welds, or poor performance of welds, can lead to catastrophic failures with costly consequences, including loss of property and life.Figure 1 is a schematic diagram of the welding process showing the interaction between the heat source and the base metal. During the interaction of the heat source with the material, several critical events occur: melting, vaporization, solidification, and solid-state transformations. The weldment is divided into three distinct regions: the fusion zone (FZ), which undergoes melting and solidification; the heat-affected zone (HAZ) adjacent to the FZ, that may experience solid-state phase changes but no melting; and the unaffected base metal (BM).Creating the extensive experimental data base required to adequately characterize the highly complex fusion welding process is expensive and time consuming, if not impractical. One recourse is to simulate welding processes either mathematically or physically in order to develop a phenomenological understanding of the process. In mathematical modeling, a set of algebraic or differential equations are solved to obtain detailed insight of the process. In physical modeling, understanding of a component of the welding process is achieved through experiments designed to avoid complexities that are unrelated to the component investigated.In recent years, process modeling has grown to be a powerful tool for understanding the welding process. Using computational modeling, significant progress has been made in evaluating how the physical processes in the weld pool influence the development of the weld pool and the macrostructures and microstructures of the weld.
Materials Reliability in Microelectronics
Authors: Lloyd James R. , Thompson Carl V. 
Published: August 2016

The 20th century has seen considerable technological achievement that has had far-reaching consequences on the way people live and do business. The first half of the century saw remarkable developments in transportation with the automobile and the airplane and in communications with radio and television. These developments would not have been possible without associated advances in materials technology. The second half of the century has been characterized by the development of the computer (see the cover of this issue).Nineteenth century futurists equated progress with scale. The bigger the better. One can only speculate on what these savants would say if introduced to what we currently call progress. Progress is now measured by how small you can make a device, how narrow you can make a conductor, and how many circuits you can fit onto the point of a pin (see Figure 1).
Electromigration and IC Interconnects
Authors: Thompson Carl V. , Lloyd James R. 
Published: August 2016

A modern integrated circuit (IC) is composed of 106 or more electronic devices. They are connected to form a circuit through the use of metallic films patterned into strips which function as wires to interconnect devices. These wires are usually simply referred to as interconnects. In an IC occupying the surface of a 1 cm2 Si chip, there can be 10 m of total interconnect length. This length is in the form of more than 106 line segments contacting pairs of devices and different segments of the circuit. This enormous number of wires is made possible by their small widths. Interconnect widths as small as 0.55 μm are currently used in commercial circuits, and circuits and processes leading to smaller and smaller widths are continuously in development.During operation of an IC, interconnects carry current densities as high as 4 × 105 A/cm2. This should be compared with a current density of 102 A/cm2, the maximum allowed for house wiring. Thin-film conductors can carry these high current densities only because of the relatively good heat sinking provided by the Si substrate.