bluuebunny/crossref_metadata_2025_split huggingface dataset:
MBE of Magnetic Metallic Structures
Authors: Prinz G. A. 
Published: August 2016

Epitaxial growth of magnetic metals actually pre-dates epitaxial growth of semiconductors. The earliest work (1936), which reported single-crystal Fe growth on NaCl, exploited the fact that single-crystal substrates of NaCl were easy to obtain, readily cleaved, and could be cleaned in a vacuum by heating. The good lattice match between the two systems and lack of interfacial disruption upon growth permitted excellent quality single-crystal films of Fe to be grown in relatively modest vacuum. Improved vacuum techniques broadened the range of materials which could be studied, with respect to both the films and substrates. The most recent ultrahigh vacuum (UHV) techniques developed for molecular beam epitaxial growth of semiconductors, including the large array of electron-based analytical tools, have also been exploited to grow and characterize magnetic metal films.Some requirements for these magnetic materials, such as the need for higher temperature effusion sources to generate useful fluxes of Fe, Co and Ni, and high vacuum in the presence of e-beam sources in order to avoid oxidation of the rare earths, served to stimulate new technical developments for the field in general. It is now possible to control growth to a fraction of a monolayer (ML) and even to know when one ML coverage is complete and another is beginning. The techniques have become so successful that a whole new subfield of magnetism has emerged — surface and interfacial magnetism — in which the work would be largely meaningless if one could not grow precisely characterized epitaxial magnetic metal films. Recent work has shown that it is now possible to grow single-crystal magnetic metal films on a wide variety of substrates, including insulators (oxides and salts), semiconductors, and metals.
Diluted Magnetic Semiconductors
Authors: Samarth N. , Furdyna J.K. 
Published: August 2016

Diluted magnetic semiconductors (DMS) are semiconducting alloys whose lattice is partly made of substitutional magnetic ions. The most extensively studied materials of this type are the alloys, in which a fraction of the group II sublattice is replaced at random by Mn. The entire family of ternary alloys, along with their crystal structure and corresponding ranges of composition, is listed in Table I. Over the past decade, these alloys have attracted a growing scientific interest because of new fundamental effects in semiconductor physics and magnetism in these materials and because of their potential applications in optical nonreciprocal devices, solid state lasers, flat panel displays, infrared detectors, and other optoelectronic applications.The increasing popularity of this field can be attributed to the broad variety of fascinating problems offered by the study of the alloys. To begin with, there is an interest in the semiconducting properties per se — for instance, the understanding of the electronic band structure and its variation with alloy composition. As in other ternary alloys, the band parameters and the lattice constant can be “tuned” by controlling the alloy composition, opening the door to band-gap engineering and lattice matching in the context of epitaxially grown superlattices and het-erostructures. The random distribution of Mn atoms with a well-characterized antiferromagnetic Mn-Mn exchange interaction provides an ideal system for studying fundamental questions in disordered magnetism. The sp-d exchange interaction between the spins of band electrons and the localized moments of the Mn atoms constitutes a unique interplay between semiconductor physics and magnetism. This leads to unusual magneto-transport and magneto-optic phenomena such as an extremely large Faraday rotation, giant negative magneto-resistance, and a magnetic-field-induced metal-insulator transition. Finally, the potential technological importance of DMS is also being recognized. For example, the large Faraday rotation holds promise of DMS applications as optical isolators, modulators, and circulators. We will briefly introduce some of the exciting research problems offered by the study of DMS. More detailed information is available in several extensive reviews and compendia.
Intelligent Processing of Materials
Authors: Yolken H. Thomas 
Published: August 2016

Advanced materials can provide specialized properties, or combinations of properties, that cannot be obtained in conventional materials. However, advanced materials generally require unusual processing operations in order to achieve their unique microstructures and the resulting greatly improved properties. These materials also tend to be expensive because of the high value added by unusual processing operations that may be labor intensive. Because the relationships among the processing parameters, microstructure, and resulting material properties and performance are not fully understood, and because the microstructure is difficult to control, reproducibility in these materials is often unsatisfactory. A very promising direction toward overcoming these difficulties involves intelligent processing of materials, a computer-based approach to automatically controlling the evolution of microstructure during processing.In a conventional automated materials processing system, automation involves utilizing sensors to monitor process variables such as temperature and pressure. Data from these sensors are compared with preset values automatically in order to maintain these values with control devices. Nevertheless, the microstructure and properties often experience significant variations. The variations are detected after the fact either by destructive analysis in a quality control laboratory or by nondestructive evaluation (NDE) at the end of the manufacturing process.In contrast, an intelligent processing system utilizes a new class of NDE sensors to characterize the microstructure of the material in real time. Moreover, the real-time data plus data from conventional process variable sensors are transmitted to a computerized decision maker.
On-Line NDE for Control and Modeling of Ceramic Processing
Authors: McClung R.W. , Johnson D.R. 
Published: August 2016

The high-temperature structural properties of ceramics make them unique candidates for application in such systems as advanced gas turbines and other heat engines. Of concern, however, is the variability in fast fracture strength of structural ceramics which is due, in part, to the sensitivity of ceramics to very small (e.g., 20–50 μm) critical flaws and the difficulty in detecting and characterizing this type of flaw by nondestructive examination (NDE) techniques.The flaw sensitivity of ceramics and the typically wide variation in flaw sizes result in the situation illustrated in Figure 1, which is a frequency distribution of fast fracture strengths for a hypothetical structural ceramic with characteristic strength of 350 MPa and Weibull modulus of 5. The strength requirement, 250 MPa, for a particular application is shown. In this illustration, a significant fraction of the population of ceramic parts, 17%, has a strength below the 250 MPa requirement.The situation illustrated in Figure 1 is typical of structural ceramics today: although in many cases the average properties of a specific ceramic may be suitable for the intended use, a significant fraction of the parts made of that material will be unsuitable. The unacceptable parts are, of course, very difficult to distinguish from the rest of the population.
Atomic-Scale Simulation in Materials Science
Authors: Baskes Michael , Daw Murray , Dodson Brian , Foiles Stephen 
Published: August 2016

Realistic simulation of the atomic-scale properties of complex systems has long been a goal of scientists interested in the behavior of condensed matter. Until recently, the role of atomistic simulation techniques has been to address rather idealized problems in statistical mechanics. Treatment of more realistic materials has been uncommon not because suitable approaches toward simulating such materials were unknown, but rather because the computer power available was inadequate. Recently, major advances have occurred in the complexity of systems subject to atomistic simulation, primarily due to a dramatic increase in availability of computer power. These new capabilities have driven the development of atomic-scale descriptions of real materials accurate enough for atomistic simulation of a wide range of specific materials science problems.In this section, we will outline several of the techniques used to simulate the microscopic behavior of an atomistic system. The first method introduced for atomistic simulation was the molecular dynamics technique, in which Newton's equations of motion for the individual atoms are integrated numerically for given interatomic and external forces. One of the first uses of this technique was the study, by Fermi, Pasta, and Ulam, of randomization of vibrational energy in a one-dimensional chain of atoms. Although the results of this initial application were to some extent unsatisfactory, the molecular dynamics technique has since been applied to a wide range of problems in the statistical mechanics of condensed media.
Three Dimensional X-Ray Computed Tomography in Materials Science
Authors: Kinney J.H. , Johnson Q.C. , Bonse U. , Nichols M.C. , Saroyan R.A. , Nusshardt R. , Pahl R. , Brase J. M. 
Published: August 2016

Imaging is the cornerstone of materials characterization. Until the middle of the present century, visible light imaging provided much of the information about materials. Though visible light imaging still plays an extremely important role in characterization, relatively low spatial resolution and lack of chemical sensitivity and specificity limit its usefulness.The discovery of x-rays and electrons led to a major advance in imaging technology. X-ray diffraction and electron microscopy allowed us to characterize the atomic structure of materials. Many materials vital to our high technology economy and defense owe their existence to the understanding of materials structure brought about with these high-resolution methods.Electron microscopy is an essential tool for materials characterization. Unfortunately, electron imaging is always destructive due to the sample preparation that must be done prior to imaging. Furthermore, electron microscopy only provides information about the surface of a sample. Three dimensional information, of great interest in characterizing many new materials, can be obtained only by time consuming sectioning of an object.The development of intense synchrotron light sources in addition to the improvements in solid state imaging technology is revolutionizing materials characterization. High resolution x-ray imaging is a potentially valuable tool for materials characterization. The large depth of x-ray penetration, as well as the sensitivity of absorption crosssections to atomic chemistry, allows x-ray imaging to characterize the chemistry of internal structures in macroscopic objects with little sample preparation. X-ray imaging complements other imaging modalities, such as electron microscopy, in that it can be performed nondestructively on metals and insulators alike.
Liquid Crystalline Polymers
Authors: Windle Alan 
Published: August 2016

Not much more than a decade ago, the plastics industry viewed itself as a mature branch of the heavy chemical industry. Its raison d'être was the mass production of four or five main-line polymers, and profits were equated to tonnage output, plant efficiency, and clever downstream processing such as film blowing. The chemistry was essentially simple and the monomer, of course, cheap. There was, however, a spark of new thinking. A trend was developing toward the design and manufacture of more complex, more expensive polymers, with special properties which could command a special price. Such products would sell advanced scientific know-how, not just engineering expertise which could all too easily be exported to the major oil producers in the form of a polymer plant.Designing particular molecules to achieve desired properties is now a major theme of polymer producers. There is a move toward increasing the aromatic content of polymer backbones to achieve greater levels of chemical and thermal stability, while the development of new cross-linking systems remains as chemically intensive as ever. It is, however, the introduction of liquid crystalline polymers which, above all, has exploited the principles of molecular design, while at the same time challenging our understanding in a new area of polymer science.A polymer is “liquid crystalline” where the chains are sufficiently rigid to remain mutually aligned in the liquid phase although the perfect positional periodicity of a crystal is no longer present. In other words there is a long-range orientational order without long-range positional order (Figure 1). Structurally, therefore, the phase is intermediate between a crystal and a liquid leading to the use of the term mesophase. Where the liquid crystalline phase forms on melting the polymer, it is known as thermotropic, but where it is achieved by solvent addition it is called Inotropic. Increasing temperature, or solvent concentration, will eventually lead to the reversion of the liquid crystal phase to the normal isotropic polymer melt.
Electrically Conductive Polymers
Authors: Wnek Gary E. 
Published: August 2016

Polymeric materials are typically considered as insulators, and in fact important applications do rely on their poor conductivity— e.g., electrical cable insulation and charged dielectric films (electrets, electrical analogs of magnets), the latter finding use in microphones. Research in the last decade, however, has lead to the discovery of polymeric materials with extremely high conductivity, approaching that of copper. This brief article will highlight recent work in the synthesis, processing and applications of these novel materials.Typical polymers, the oxidant (or “dopant”) used to create carriers, and room temperature conductivities are given in Table I. A key feature shared by these materials is delocalized (at least over a few repeat units) π-electron density. Such unsaturated polymers facilitate carrier generation because of the ability for resonance derealization of the resulting radical ions, which can also offer good intramolecular carrier mobility. In addition, the geometry of π-orbitals allows for good orbital overlap and encouragesintermolecular carrier transport.That the polymer chains are considerably shorter than typical sample dimensions indicates that intermolecular transport is dominant, especially in view of the disorder observed in most conducting polymer systems. However, as the number of defects (crosslinks, “twists” which inhibit conjugation) decreases, it might be anticipated that carriers can travel greater distances along a chain before a (presumably) higher activation energy, inter molecular electron transfer becomes necessary, thus affording higher conductivity. Indeed, it has been recently reported that samples of very high quality, oriented polyacetylene, when treated with iodine,exhibit conductivities approaching that of copper at room temperature.
Ferroelectric Ceramics for Dielectric Electromechanical and Pyroelectric Applications
Authors: Schulze Walter A. , Gururaja Turuvekere R. 
Published: August 2016

The growth of integrated circuit applications has been a strong influence in the expansion of markets for ferroelectric ceramics. Ferroelectrics perform three major functions in circuits:1. They store energy with a high volume efficiency,2. They have very useful large changes in impedance with frequency, and3. They transduce between various energy forms and electrical signals.For many years commercial ferroelectric ceramics have been dominated by the barium titanate and lead zirconate titanate (PZT) systems. A tremendous research effort has been dedicated to these systems with very interesting studies still progressing on basic understanding, reproducibility, and modifications to utilize inexpensive electrodes. Processing studies are also seeking to reduce the size of devices and develop new transducing and sensing applications. The need to reduce cost and to fulfill specific applications is creating demands for new materials. Much of this effort has centered on lead-based systems referred to as relaxor ferroelectrics.The areas of application of ferroelectrics are narrowed in this review by eliminating the interfacial (grain-grain boundary) devices and electro-optic applications discussed in “Electronic Ceramic Thin Films” by Bruce Tuttle in this issue. Also, this article can only cover a small fraction of the information indicated by the title.
Plasma Synthesis of Ceramic Powders
Authors: Phillips D.S. , Vogt G.J. 
Published: August 2016

Condensation from plasmas has been shown to yield very fine, high purity powders from even the most refractory materials. Elementary particles in these powders are often single crystals, as fine as 50 nm diameter. These particles vary widely in agglomeration state; in some systems they are essentially independent, while in others hard agglomerates as large as several microns are observed. In this article the geometric aspects of reactor design which are thought to influence these powder structures are reviewed, along with three case studies in powder microstructure. Finally, the structure of the “typical” plasma powder is compared with expectations from alternative preparation routes.The development of new, energy-efficient processing strategies for ceramic fabrication has become a rapid growth field over the last ten years. Most of these strategies rely on minimizing diffusion requirements during densification by improving both the chemical homogeneity and the initial density of the powder compact to be consolidated; both requirements dictate unusual care in the synthesis of the starting powders. In the oxide systems most extensively studied to date, the required powders can often be produced by precipitation from aqueous solutions and/or emulsions. In the carbide and nitride systems widely envisaged for the next generation of structural applications, these techniques are difficult and gas-phase synthesis routes appear more attractive. In fact, even the leading practitioners of the precipitation arts write enthusiastically of aerosol synthesis methods for the oxides.
Up Close: MIT's Ceramics Manufacturing and Process Integration Laboratory
Authors: Pober Richard L. , Thomson Elizabeth A. 
Published: August 2016

In a relatively short period of time ceramics have become the key elements to a variety of new technologies, including integrated circuit substrates, artificial limbs, turbocharger rotors, and, of course, superconductors. By and large, however, they have not met their potential. Though advances in basic research are responsible for the breakthroughs so far, no extensive work has been done to establish the manufacturing paradigms necessary for the production of reliable, reproducible materials.The new Ceramics Manufacturing and Process Integration Laboratory (CMPIL) at the Massachusetts Institute of Technology was conceived to address this need. As a logical extension of the science-based Ceramics Processing Research Laboratory (CPRL), also at MIT, the CMPIL will “test” fundamental ideas as they relate to ceramics manufacturing. The goal is to create a hands-on “research factory,” complete with manufactured product, to make an impact on manufacturing productivity and teach students, staff, and visiting scientists the principles that control ceramics manufacturing systems. Other thrusts include developing innovative processing techniques and collecting operating data that will ultimately be transferred to industry.
Fundamentals of X-Ray Photoemission Spectroscopy
Authors: Grunthaner F.J. 
Published: August 2016

AbstractRapid progress in the development of new electronic materials and the steady maturation of silicon-based technologies has resulted in a host of novel electronic devices in which the active region of the structure is confined to an interface or a surface. The chemical, electronic, and physical characterization of surfaces and interfaces in semiconductors and insulators is of critical importance to manufacturing process control as well as to the fundamental electron physics and materials science which support microelectronic device research.
Up Close: The Ion Beam Materials Laboratory at Los Alamos National Laboratory
Authors: Tesmer J.R. , Parkin D.M. , Maggiore C.J. 
Published: August 2016

The new Ion Beam Materials Laboratory (IBML) is a Los Alamos National Laboratory (LANL) resource devoted to the characterization and modification of surfaces through the use of ion beams. IBML was developed and designed in response to a large number of recognized research needs ranging from archaeology to the Strategic Defense Initiative and from basic research to semiconductor development. Most recently, the IBML has been used in research on high temperature superconductors. The IBML was dedicated in February 1987 when the 3 MV tandem accelerator reached operational status.Beginning with an existing accelerator facility built to support nuclear physics, Los Alamos researchers added materials science capability and started to demonstrate the power of ion beam techniques as they apply to many of the Laboratory's research activities. These efforts led to a growing interest in ion beams by fellow researchers and caught the attention of LANL management. By the fall of 1984, a clear grassroots case—which was supported by the Laboratory's Center for Materials Science (CMS)—was made for developing a modern ion beam facility, which included capabilities for materials modification and analysis. The $1.7-million IBML was funded with Laboratory-wide resources in the spring of 1985 and was charged with supporting Laboratory-wide programs.
Up Close: Center for Materials Science at Los Alamos National Laboratory
Authors: Parkin Don M. 
Published: August 2016

Los Alamos National Laboratory (LANL) has extensive and diverse activities and programs in materials science and engineering. The Center for Materials Science (CMS) was established to promote scientific collaboration and scientific excellence in materials research and engineering throughout the Laboratory and with individuals and institutions outside the Laboratory. The Center's objective is to enhance the Laboratory's materials science and technology contributions to the nation's defense, energy, and scientific missions.Consistent with its main objective, Laboratory resources supply the principal funding for CMS programs. Additional funding for individual scientific research programs conducted by CMS members comes directly from outside sources.To carry out its responsibilities, CMS has accepted four demanding missions:1. Build a core group of qualified and established materials scientists and solid state physicists.2. Promote and support top-quality, interdisciplinary materials research programs at Los Alamos.3. Strengthen the interactions of materials scientists at Los Alamos with the external materials science community.4. Establish and maintain modern materials research facilities in a readily accessible, central location.The core group of CMS members has a broad charter to advance materials science and technology in directions expected to have long-term impact on LANL's mission. The acting director is Don M. Parkin. In addition to the director, six members presently constitute the CMS. James L. Smith heads an experimental effort in superconductivity.