bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Porous Solids
Authors: Smith Douglas M. , Hua Duen-Wu , Earl William L.
Published: August 2016

Progress in the synthesis and engineering of advanced porous materials demands better pore structure characterization. The analysis of pore structure is complicated by (1) the wide range in pore sizes observed, from molecular (<1 nm) to macroscopic (>1 mm) dimensions, (2) complex pore shapes and connectivities, (3) chemical and physical heterogeneities, and (4) pore structure changes that can occur during characterization.

The required pore structure information varies with application. Bulk density and the pore-size distribution are needed for thermal insulation. In this case, the dimension of interest is the so-called hydraulic radius since, for small pores, the gas-phase conductivity is proportional to the mean hydraulic radius to the mean free path. A few large but isolated pores will significantly affect conductivity but will go undetected in typical gas-absorption methods. In contrast, for separations, bottlenecks control performance. For transport, such as migration through geologic formations, both the pore-size distribution and pore connectivity are important. For adsorption, surface area and pore size are the relevant factors. Finally, the conventional concepts of pore structure lose meaning as the pore size approaches molecular dimensions, typical of adsorbents and gas-separation membranes.
John von Neumann and Materials Science
Authors: Seitz Frederick
Published: August 2016

I presume that many of you will be surprised to learn that John von Neumann, a great mathematician, and a remarkable man, had even a passing interest in materials science since his name is usually associated with work in function theory, mathematical logic, the mathematical foundations of quantum mechanics, game theory, and of course with the development of computer logic. Actually, he was deeply interested in the evolution of materials science and technology, and he played an important role in giving prominence to materials science at a critical time in its evolution. But first let me tell you a little about his life.

John von Neumann was born in Budapest, Hungary, in 1903 into a prominent business family. His mathematical genius was recognized early by his high school teacher, Lázsló Ratz, who insisted that he receive special tutoring since mathematical geniuses tend to flower early. He became a close and, indeed, a lifetime friend of a slightly older fellow student, Eugene Wigner, who was inspired by the same mathematics teacher. The two of them frequently wandered home together after school, with von Neumann providing a tutorial on some aspect of mathematics while Wigner, who had a comparably brilliant mind, absorbed everything. The two students had different personalities, but shared a great love of mathematics.

Von Neumann was never a narrow genius. He soaked up knowledge of all kinds rapidly and was exposed to much because the von Neumann family dinner gatherings were devoted to discussions of technical, historical and cultural affairs, as well as business. This great versatility in interests was a characteristic trademark of von Neumann‘s entire life.
Materials and the Environment
Authors: Weissman Suzanne H. , Sekutowski Janine C.
Published: August 2016

We co-organized the first MRS technical symposium dealing with the environment at the 1991 Spring Meeting in Anaheim, California. Entitled “Environmentally Conscious Materials Processing,” the symposium dealt with waste minimization, pollution prevention, alternative materials and processes, recovery and recycling, and chemical sensors for process stream monitoring. This symposium captured much interest among the press and the materials community. Because of the growing interest in the environment, the MRS Bulletin asked us to guest edit this special issue that deals with the interrelated areas of materials science and the environment.

In recent years, environmental concern has heightened in the United States and around the world. Public concern was greatly raised by increased environmental awareness incidents such as the accident in Bhopal, India, and the oil spill in Alaska by the Exxon Valdez. As a result, U.S. companies are more concerned with public acceptance of their operations. In addition, manufacturers have been subject to increasingly stringent environmental legislation. Federal, state, and local legislation currently regulate air emissions, water discharges, occupational exposure, and treatment and disposal of various hazardous chemicals. In addition, the Montreal Protocol, an international agreement signed by the United States, regulates the production and use of halogenated organic compounds now known to deplete the Earth's ozone layer. Associated with these stringent environmental regulations are increasing waste-associated costs. Waste disposal costs are increasing at an annual rate of about 10%.
The Changing Paradigm for Business Success in Advanced Materials and Components Manufacturing
Authors: Barnett B. , Bowen H.K. , Clark K.
Published: August 2016

The use of manmade materials progressed rather slowly until the science and technology of metals, refractories, and glass burst forth in the mid-1800s and continued its infancy through the first decades of the 20th century. In fact, much of the scientific wherewithal in industrial nations focused on the development of manmade materials from the standpoint of properties and fabrication processes. From the discipline of metal physics, which emerged in the 1930s, and from the scientific activities in ceramics, polymers, and electronic materials that blossomed in the 1940s and 1950s, a science and engineering base was established, enabling advanced materials and components to be fabricated, often for specific end-user applications. The molecular engineering of crystals, for example, has its roots in von Hippel's studies of dielectric materials at the Massachusetts Institute of Technology, which began in the 1930s. In this time frame, society, which had primarily used such materials as wood, gypsum, clay, copper, zinc, lead, and iron, turned to a broader set of materials to meet new uses. These new applications required an understanding not only of the composition of matter, but of novel and difficult processes as well. Research specialties broadened.

From the late 1950s to the present, the knowledge base for materials and components has exploded. In this period, the scientific and technological field of endeavor—materials science and engineering (MS&E) — evolved from a collection of discrete, disparate arts and crafts with varied amounts of science and practitioners who generally did not stray from their own specialties to a more diffuse field where researchers take a broader approach to materials research and practice.
GaAs Integrated Circuit Manufacturing
Authors: del Alamo Jesús A.
Published: August 2016

In the mid 1980s, reports of exciting progress from GaAs integrated circuit (IC) performance from R&D laboratories world-wide portrayed a rosy future for GaAs. Now, in the early 1990s, true to their reputation, GaAs ICs are still largely the stuff of the future. In fact, deployment of GaAs ICs in real systems has been disappointingly slow. In 1985, the commercial GaAs IC market was forecast to reach $800 million by 1990. The actual figure was only $142 million. To put this number in perspective, it represents less than 0.4% of the total Si IC merchant market.

In a recent survey of the GaAs industry, Kato explored the causes for GaAs troubles, with startling findings. The issue certainly does not seem to be a performance one because GaAs ICs are sufficiently ahead of alternative technologies. Material quality is not a problem either. Extremely high-quality 3 in. and 4 in. GaAs wafers are now on the market at reasonable prices. On the other hand, several serious deficiencies center around IC manufacturing. The price of the final GaAs ICs is perceived as not competitive with alternative technologies. This is rooted in the low yields and poor repeatability of the manufacturing lines. A great contribution to cost is time-consuming functionality testing, particularly for analog products. For MMICs (monolithic microwave integrated circuits) in particular, final testing can easily become the bottleneck of the entire fabrication process. There is also much uncertainty about reliability. This might explain to a large extent the low customer confidence in the technology. Kato reports that fundamental technical problems in making GaAs ICs are still believed to remain.
Nuclear Magnetic Resonance Spectroscopy of Geological Materials
Authors: Stebbins Jonathan F.
Published: August 2016

From the earliest days of extractive metallurgy, materials scientists and geoscientists have shared common ground. Experimental approaches, such as phase equilibrium and structural studies, are often similar, as are the questions asked in attempts to connect microscopic fundamentals to technologically desired or naturally observed bulk properties. The actual materials studied by both groups are often similar or even identical, such as silicate ceramics and glasses, magnetic oxides, and crystals based on the perovskite structure.

Nuclear magnetic resonance (NMR) was applied to solid-state physics shortly after the technique was invented in 1946. Even at the start, many of the samples placed in magnets in physics laboratories were large single crystals of naturally occurring minerals such as gypsum (CaSO4 · 2H2O) and fluorite (CaF2), perhaps borrowed from mineralogist colleagues. In the last 10 years, however, applications to both the earth and materials science have rapidly expanded because of improvements in both technological capabilities and basic theory. Only work on inorganic materials will be discussed here, although 13C NMR studies have proved very useful in characterizing the complex, often inseparable mixtures of large organic molecules found in soils, kerogen, and coal. I will not attempt to thoroughly review the broad and fast growing literature in inorganic applications. Instead, I have chosen examples, primarily from our recent studies, to illustrate the scope of what is and will become possible.

Several recent books clearly introduced the basic concepts of solid-state NMR, and applications to crystalline and glassy silicates as well as NMR at high temperature have been reviewed recently.
Structure of Glasses of Geological Interest: Applying Spectroscopic Techniques
Authors: Hawthorne Frank C.
Published: August 2016

Glasses are a minor fraction of Earth materials. However, all igneous processes within the Earth involve a melt phase (magma), and our understanding of the physical and chemical features of these processes is contingent upon an adequate understanding of the melt phase itself. In particular, we wish to relate the behavior of such melts to their composition and structure in the range of physical and chemical conditions in which they occur. The physical conditions of many of these processes are particularly difficult to reproduce in the laboratory, and the ability to predict behavior under such conditions is the goal. From a geological viewpoint, the primary interest is in silicate melts because of the composition of the Earth's lithosphere and mantle. There are significant experimental difficulties in looking at the behavior of silicate melts, so much work has focused on glasses as melt analogues since spectroscopic data on silicate glasses and melts (Figure 1) are similar.

Silicate glasses are also of considerable industrial interest, and early work in the geological field borrowed heavily from materials science. However, the thrust to understand natural magmas led geologically based work into more complex chemical systems (e.g., hydrous alkali-alkaline-earth-aluminosilicates) and their behavior at high pressures.

The structure of glasses is a complex issue, and many different experimental techniques are needed to resolve the details of their structure. Here I will focus on the following techniques: IR (infrared), Raman, Mössbauer, EXAFS (extended x-ray absorption fine structure) and XANES (x-ray absorption near-edge spectroscopy) spectroscopies.
Buried Oxide and Silicide Formation by High-Dose Implantation in Silicon
Authors: Celler G.K. , White Alice E.
Published: August 2016

Experiments in ion implantation were first performed almost 40 years ago by nuclear physicists. More recently, ion implanters have become permanent fixtures in integrated circuit processing lines. Manufacture of the more complex integrated circuits may involve as many as 10 different ion implantation steps. Implantation is used primarily at f luences of 1012–1015 ions/cm2 to tailor the electrical properties of a semiconductor substrate, but causing only a small perturbation in the composition of the target (see the article by Seidel and Larson in this issue of the MRS Bulletin). Applications of implantation had been limited by the small beam currents that were available, but recently a new generation of high-current implanters has been developed. This high-current capability allows implanting concentrations up to three orders of magnitude higher than those required for doping—enough to create a compound.
Thin Film Processing of Complex Multilayer Structures of High-Temperature Superconductors
Authors: Ono Ronald H.
Published: August 2016

The realization of a revolutionary generation of electronics based on high-temperature superconductors (HTS) crucially depends on the ability to make high-quality thin film microstructures. These will incorporate materials such as YBa2Cu3O7-δ (YBCO), TlBaCaCuO, or BiSrCaCuO in a fashion similar to the circuits and devices made of their low Tc counterparts Nb or NbN. Without exception, the most valuable structures will be composed of multiple layers of superconducting films and dielectrics, in some cases combined with normal metals, low-temperature superconductors, or a variety of semiconductors. Generically, these can be combined in two ways: in a hybrid design where specialized packages and bonding are used to attach dissimilar materials, or in a monolithic thin film structure such as the one seen in Figure 1.

The division between hybrid and monolithic multilayers results from the historical development of electronic circuits. Hybrid designs typically require linewidths and alignment accuracy somewhat less demanding than those used in fully integrated circuits. The advantage of hybrid construction is the separation of incompatible processing steps onto different substrates or die. The monolithic integrated circuit, whether microelectronic, millimeter wave, or radio frequency, can be made in large batches with concomitant economy of scale and can be fabricated with fewer parasitic constraints. Superconducting integrated circuits have followed the semiconductor pattern of being developed in a hybrid fashion, then transferred to a fully integrated process.
Art and Technology
Authors: Vandiver Pamela , Druzik Jim
Published: August 2016

Art has as many meanings as contexts in which it operates. It can mean surface decoration or the integral sum of parts and whole which a historian analyzes as structure using visual, musical, theatrical or other criteria. Art serves as decoration, but also serves to signal or sign a particular meaning. Art often confers an elite social status on its patrons or provides goods which support the power and prestige of a special group or person. Art is also used to describe the experience of viewers, usually as “aesthetic experience”; for instance, we experience art as beauty, as a shared emotional experience or empathetic understanding, or as interactive play or a process of performance by which we investigate or relate ideas, occurrences, or objects and give them meaning.

Technology, in contrast, is usually defined as “praxis” and involves doing things, as a craft practice involving materials selection and refinement, followed by making those materials into useful things, artifacts, or objects which serve useful functions for individuals, a social group, class, or culture. The products of technology can be useful as tools that enable a task to be accomplished, or as products which satisfy subsistence needs, or devices, or even practical ideas. When put to use, they enable travel, communication, transportation of goods, or control of energy. But technology has another meaning which is often thought to be less useful, namely technical marvels—things which amaze or surprise us. Some examples are the mechanical automatons of the 17th and 18th centuries, the latest computer game, a special way of hearing or seeing, or even the gas and light spewing magic machines described as being used in Greek temples to get peoples' attention. Another example is the technology described by the 11th century monk Theophilus, used to equip a church, from bells and censors, to glass windows and painted walls. In these examples, doing technology or learning to use technological marvels is a way of almost magically extending our own power and understanding beyond ourselves.
AMS Radiocarbon Dating: Its Current and Future Role in Art Research
Authors: Stulik D.C. , Donahue D.J.
Published: August 2016

Since the development of14C dating by W.F. Libby in the 1940s and 1950s, the method has proved to be the best absolute method for chronometric dating of organic and some carbon-containing inorganic materials. It has become an essential research tool for both archaeologists and geologists. Even broader application horizons have been opened to radiocarbon dating by use of the accelerator mass spectrometer, which allows routine analysis of submilligram samples. Art curatorship and art conservation directly benefit from this development.

There are pronounced similarities between application of radiocarbon dating in archaeology and art research but there are also major differences which make it difficult to simply take a methodology developed for archaeological research and apply it directly to radiocarbon dating of art objects.

In both fields the application of dating techniques focuses on dating an object of unknown age or cross-checking the age of an object previously dated by other methods.
Fracture Behavior of Cement-Based Materials
Authors: Shah S.P. , Ouyang C. , Lange D.A.
Published: August 2016

The characterization of fracture behavior is a continuing challenge to the cement and concrete community. The performance of a material can be evaluated by its stress-strain response. For an ideally brittle material, elastic response is terminated when stress suddenly drops to zero, as shown in Figure 1a. However, cement-based materials are considered quasi-brittle because they respond nonlinearly prior to peak stress, and their stress gradually decreases after reaching a peak, as indicated in Figure 1b.

To make cement-based materials stronger and tougher, one needs to understand the fracture mechanisms associated with nonlinear stress-strain behavior and to characterize material fracture properties based on these fracture mechanisms. Three novel techniques are being used at the Center for Advanced Cement-Based Materials (ACBM) to detect the quasi-brittle nature of cement-based materials. These three techniques are laser holographic interferometry, acoustic emission, and microscopic surface analysis. This article summarizes both the fracture mechanisms in cement-based materials and the application of the three techniques to characterize and measure fracture properties.
Use of Complementary Imaging Techniques in Concrete Deterioration Studies
Authors: Wagner K.E. , Draper E.A. , Skalny J.
Published: August 2016

The infrastructures of the United States and other industrialized nations are, to a large degree, based upon concrete. With such a pervasive application, the importance of accurately analyzing concrete structure failures and addressing durability problems is obvious, as is the timely recognition of premature structure deterioration, so that an appropriate recommendation for remediation may be made. Although concrete is one of the most important engineering materials in use today, it is perhaps also the least understood, primarily because it is chemically reacting and changing throughout its service life. The chemical and physical changes that occur in this material can have degenerative effects on its mechanical properties and, ultimately, on its durability. Understanding how these chemical reactions occur within the concrete and affect its physical characteristics is often not straightforward. For example, the reactions can be affected by internal components (cement, fine and coarse aggregate), mixing procedures, curing cycle parameters, and/or the choice of additives. External influences on these reactions include weather exposure, chemically aggressive environments, and climate-mitigating surface treatments. Furthermore, there are some deleterious internal reactions that tend to occur sequentially and others that may occur concurrently. The overlap of simultaneous reactions can make it difficult to isolate the initial occurrence and to identify the deleterious component of deterioration. To resolve such questions, it is necessary to understand the interrelationship among the concrete components and their processing, and to examine the material with a variety of complementary techniques and sample configurations.
Microstructure-Property Relationships in Macro-Defect-Free Cement
Authors: Lewis Jennifer A. , Kriven Waltraud M.
Published: August 2016

The term “macro-defect-free” refers to the absence of relatively large voids (or defects) that are normally present in conventional cement pastes due to entrapped air or inadequate mixing. A decade ago, Birchall and co-workers developed a novel processing method that avoids the formation of these strength-limiting defects. This method, outlined schematically in Figure 1, consists of mixing hydraulic cement powder, a water-soluble polymer, and a minimal amount of water under high shear to produce a macro-defect-free (MDF) cement composite. Several cement/polymer systems can be processed by this flexible technique, although the calcium aluminate cement/polyvinyl alcohol-acetate (PVA) copolymer system is most common: MDF cements display unique properties relative to conventional cement pastes. For example, the flexural strength of MDF cement is more than 200 MPa as compared to values on the order of 10 MPa for conventional pastes. One can view MDF cements as a type of “inorganic plastic.” As is the case with plastic processing, fillers such as alumina, silicon carbide, or metal powders can be added to MDF cement to modify its performance properties (e.g., abrasion resistance, thermal or electrical conductivity, and hardness). The combined attractiveness of inexpensive raw materials and flexible, low-temperature processing has generated great interest in this new class of advanced cement-based materials.
In Situ Ellipsometry in Microelectronics
Authors: Irene E.A. , Woollam J.A.
Published: August 2016

Ellipsometry has been used in microelectronics since the early 1960s when it became necessary to measure the thickness of transparent films on reflective substrates. Ellipsometry is an old technique but with the increasing technological importance of thin films, particularly in microelectronics, and with the availability of faster computers for calculations, ellipsometry is in a renaissance. In principle it is a simple technique (don't confuse simple with easy!) that relies primarily on the physical optics of stratified media. Excellent treatments of ellipsometry exist (e.g., a book, recent reviews), and it is not the intent here to try to improve upon them. Rather, this article is intended to briefly discuss the essential ideas and then to show a few examples of in situ ellipsometry applied to modern materials-research problems. The emphasis here is on in situ ellipsometry, because it is one of the few techniques that can accurately monitor thin-film processes while they occur, yielding both fundamental properties and process information about the system under measurement. In addition it is now possible to use feedback to affect control of thickness, composition, and temperature, for example.

We first consider some basic questions: What is ellipsometry, what does it measure, and how well? Next, we discuss hardware for in situ ellipsometry, and finally we show a few examples.
Analysis of Growing Films of Complex Oxides by RHEED
Authors: Bozovic Ivan , Eckstein J.N.
Published: August 2016

The majority of sophisticated ultra-high-vacuum (UHV) systems for deposition of thin films, such as molecular beam epitaxy (MBE) machines, contain some kind of electron diffraction apparatus which is used to scrutinize the surface structure of the film while it is grown. Reflection high energy electron diffraction (RHEED) is probably the most frequently employed configuration. An excellent introduction to RHEED, including a treatment of electron diffraction, reciprocal-space description, reflection from imperfect surfaces, etc., was recently published in the MRS Bulletin by Lagally and Savage. Hence, we will not review these basics here. Rather, we will assume the reader to be familiar with that article, and will refer to it as LS.

The materials discussed in LS include Si, Ge on Si, and GaAs. The applications of MBE for synthesis of semiconductor thin films and heterostructures are widely recognized. MRS has recently bestowed its greatest honor, the Von Hippel Award, to Alfred Y. Cho for his pioneering work on MBE synthesis of GaAs and its application to new devices.

In contrast, here we focus on complex oxides—cuprates, titanates, manganates, etc. This is a relatively new area of application for both MBE and RHEED. Actually, it was only after the discovery of high-temperature superconductivity (HTS) that many MBE systems were designed and built specifically for metallic oxide deposition. More recently, some of these machines have also been employed to synthesize other interesting oxides, for example, ferroelectrics and ferromagnets. In all these studies, RHEED has been the principal diagnostic tool and source of information about the growing film surface.
Biomaterials: New Polymers and Novel Applications
Authors: Langer Robert
Published: August 2016

The following is an edited transcript of the plenary lecture presented by Robert Langer at the 1995 MRS Spring Meeting on April 17, 1995 in San Francisco.

Over the last 21 years I have been involved in examining and studying, and in some cases synthesizing new polymers and biomaterials, looking at how they might be able to solve two problems. One set of problems involves drug delivery; a second involves creating new tissues.

Controlled drug release is a relatively young field that has involved a fundamental change in the way drugs are delivered. Transdermal drug delivery, for example, uses five layers of polymers, yet the whole system is 0.2 mm thick. One such polymer contains nitroglycerine, which is slowly released for one day from a patch through the skin into the blood circulation. This process provided a novel way to treat angina for patients with chest pains. First introduced in 1982, such drug-delivery systems saw a usage rate of over 500 million last year.

Norplant systems, which are silicone capsules placed under the forearm, slowly release a birth-control drug for over 2,000 days, or five years, from what are actually six small implants about the size of match sticks. These two examples illustrate that drugs can be made to slowly diffuse through polymers over a long period of time.
SEMPA Studies of Exchange Coupling in Magnetic Multilayers
Authors: Celotta R.J. , Pierce D.T. , Unguris J.
Published: August 2016

In the late 1980s, a number of exciting yet puzzling observations resulted from experiments investigating the coupling between two ferromagnetic layers separated by a nonferromagnetic spacer layer. A pioneering experiment by Grünberg et al. showed that Fe layers separated by a thin Cr spacer aligned with antiparallel magnetization, but with Au as the spacer layer, a parallel alignment occurred. The long-range magnetic dipole from each layer would tend to explain antiparallel alignment; small pinholes in the spacer layer would produce parallel alignment. Alternatively, the layers might be coupled through the spacer-layer conduction electrons by the Ruder man-Kittel-Kasuya-Yosida (RKKY) effect. This was expected to produce an oscillation in coupling as the spacer thickness increased, that is, an oscillation between parallel and antiparallel alignment. Oscillatory coupling was first observed by Parkin et al. Researchers had also found that, at spacer thicknesses where antiparallel alignment occurred, the Fe/Cr/Fe system can exhibit a giant magnetoresistance (GMR) effect, that is, an anomalously large change in resistance when a magnetic field is applied. The potential technological importance of the GMR effect to magnetic sensing and magnetic information storage added further impetus to the already rapidly growing area of research in magnetic multilayers.
Surface Magnetism and Kerr Spectroscopy
Authors: Qiu Z.Q. , Bader S.D.
Published: August 2016

Magneto-optic effects were first discovered in 1845 by Michael Faraday, but these effects continue to make a major impact on the materials community to this day. The need for new magnetic information-storage media has stimulated new approaches and opened new scientific opportunities in the exploration of thin-film and surface magnetism. This article provides background to some of these developments and highlights examples of contemporary issues that provide a focus for the field. In the Faraday effect, the polarization plane of linearly polarized light rotates when a magnetic field is applied in the propagation direction. The analogous phenomenon was subsequently discovered by the Rev. John Kerr in 1877 for light reflected from opaque materials. The works of Faraday and Kerr serve as cornerstones for our present understanding of magneto-optic effects in magnetic materials. Magnetooptics is presently described in the context of either microscopic quantum theory or macroscopic dielectric theory. Microscopically, the coupling between the electric field of the propagating light and the electron spin in a magnetic medium occurs through the spin-orbit interaction. Macroscopically, magneto-optic effects arise from the antisymmetric, off-diagonal elements in the dielectric tensor, as discussed in the next section.

Magneto-optic characterizations of surface magnetism began only a decade ago. The first surface magneto-optic Kerr-effect study, better known by its acronym SMOKE, concerned the magnetichysteresis loops for ultrathin Fe films grown epitaxially on Au(100). Since then, SMOKE has emerged as a premier surface-magnetism technique. SMOKE has been applied to various topics in low-dimensional magnetism, ranging from the detection of magnetic order to the characterization of critical behavior, magnetic surface anisotropies, and the oscillatory antiferromagnetic coupling exhibited by giant-magnetoresistance

heterostructures. Additional interest in SMOKE has been generated by the recent commercialization of high-density, magneto-optic information-storage media, and especially by the next-generation candidate material based on Co/Pt superlattices.
Micromagnetic Modeling: Theory and Applications in Magnetic Thin Films
Authors: Zhu Jian-Gang
Published: August 2016

Micromagnetic theory concerns detailed magnetization configurations and the magnetization-reversal processes in a ferromagnetic system. By combining the original micromagnetic theory with a dynamic description of magnetization orientations, one can simulate complete magnetization processes and calculate important properties such as magnetic hysteresis and magnetic switching dynamics. Not only can micromagnetic simulation predict complex magnetic-domain configurations in a ferromagnetic system, it also can generate transient pictures showing how a complex domain configuration forms. Very important among these systems are ferromagnetic thin films, particularly those used in sensors and recording devices. Micromagnetic modeling not only has enriched our understanding of existing magnetic films but has also been used to successfully predict the magnetic properties of new film microstructures created for particular applications.

In this article, a brief introduction of micromagnetic-modeling theory will be given. Modeling of soft and hard magnetic films will be discussed separately through two examples illustrating the essence of micromagnetic-magnetization processes in these films.
Coherent Lorentz Imaging of Soft, Thin-Film Magnetic Materials
Authors: McVitie Stephen , Chapman John N.
Published: August 2016

A detailed knowledge of the micromagnetic structure of thin films is essential for our understanding of the magnetic processes in modern magnetic materials. Many technological applications in the magnetic-recording industry involve thin-film materials including magnetic and magneto-optic recording media and magneto-resistive sensors. Electron microscopy allows imaging of the magnetic structure of such thin films with very high spatial resolution. It is also possible in certain instruments to study the behavior of the materials in the presence of a magnetic field while the specimen is still in the microscope. This facility offers the prospect of full magnetic characterization of thinned materials using electron microscopy.
Chemical Vapor Deposition of TiN for Sub-0.5 μm ULSI Circuits
Authors: Eizenberg M.
Published: August 2016

Titanium nitride (TiN) has been recognized as an excellent barrier material in various metallization structures of advanced microelectronic devices. TiN serves as a nucleation/glue layer as well as a barrier against WF6 attack in W plug filling. It serves as a diffusion barrier during or after high-temperature Al reflow processing for contact and via filling. TiN is considered as a diffusion-barrier material for Cu metallization as well. In addition, it is utilized as an antireflection coating layer, especially on top of Al, an application that will not be discussed in this article.

TiN films must conform to the extreme topographies used in devices in order to guarantee void-free plug formation as well as Jow junction leakage. This should be achieved with the thinnest films possible in order to reduce interconnect stack thickness and to lower contact or via resistance. (The TiN resistivity is higher than that of the other components of the metallization—Ti, Al, or W.) In addition, the good barrier properties must be retained following various thermal cycles used in multilevel metallization. Finally, the metallization must be manufacturing-worthy, namely, it should be reliable and reproducible, it should have a very low particle content, and it should have a low cost of ownership.

At present, TiN is mainly deposited by physical vapor deposition (PVD) via reactive sputtering. However, the poor conformality of sputtered TiN films over extreme topography limits the use of this deposition technique for deep sub-0.5 μm applications, especially those with features that have high aspect ratios.
Swift, Heavy Ions in Insulating and Conducting Oxides: Tracks and Physical Properties
Authors: Provost J. , Simon Ch. , Hervieu M. , Groult D. , Hardy V. , Studer F. , Toulemonde M.
Published: August 2016

Transition metal oxides belong to the class of iono-covalent materials in which electrons are, to first order, localized in tight metal-oxygen bonds. They appear to be quite different from classical metals in which electrons are assumed to be delocalized in a free electron gas. Nevertheless, due to exchange interactions and hybridization of atomic orbitals, oxides exhibit many interesting physical properties like magnetic ordering and various electron transport properties that extend from wide gap insulators to narrow band conductors and high-temperature superconducting (HTS) superconductors. This class of materials appears well-suited to the study of the damage induced by heavy ion irradiation and its consequence on physical properties like electrical resistivity.

In this article, we will describe the results of heavy ion irradiations in magnetic oxides, exhibiting a wide palette of electron transport properties from insulators to metals through hopping semiconductors and in HTS copper oxides that are narrow-band metals aboveTc. We will show that heavy ion irradiation, in addition to disordering matter, can induce changes in some physical properties like magnetic ordering and orientation of magnetic fields, and can produce large increases of the critical current. To account for these results, the thermal spike model will be considered as a possible way to understand the damage creation in iono-covalent compounds.
Electroceramic Thin Films Part I: Processing
Authors: Auciello Orlando , Ramesh Ramamoorthy
Published: August 2016

Basic and applied science of electroceramic thin films is an interdisciplinary field that is rapidly evolving worldwide. A major driving force for the extensive research in many university, industrial and national laboratories around the world is the promise of a new generation of advanced microdevices that may transform various technologies, potentially creating new multibillion-dollar markets. Electroceramic-thin-film properties that are being intensively investigated include electrical conductivity, large dielectric permittivity, ferroelectricity, piezoelectricity, pyroelectricity, and electro-optic activity. Perhaps the most publicized application of electrical conductivity of electroceramics is that related to the new high-temperature-superconducting (HTS) materials, which has been extensively discussed in numerous national and international conferences and in the scientific literature. Less glamorously publicized applications, but as important as those of HTS materials, are those involving ferroelectric materials, which is the subject of this MRS Bulletin.
Laser-Ablation Deposition and Characterization of Ferroelectric Capacitors for Nonvolatile Memories
Authors: Auciello O. , Ramesh R.
Published: August 2016

An intense worldwide research-and-development effort has been undertaken during the last seven years with the objective of developing thin-film deposition techniques and materials-integration and processing strategies capable of realizing a commercially viable solid-state nonvolatile-ferroelectric-random-access-memory (NVFRAM) technology. Many laboratories around the world have focused their work on developing strategies for integrating submicron thin-film ferroelectric capacitors with the mature silicon-based transistor technology to yield capacitor-transistor-based memory architectures as schematically illustrated in Figure 1. This figure also shows the perovskite unit cell of a capacitor, based on a ferroelectric Pb(ZrxTi 1−xO3 (PZT) layer, and the variety of structural, chemical, electronic, and ionic interfaces that arise during the fabrication and integration of these metal-oxide hetero-structure capacitors on a Si substrate. Nonvolatile ferroelectric random-access memories exploit the capacity of the ferroelectric layer to be polarized in two opposite directions, which are used as the 0 and 1 binary stable states.
PE-MOCVD of Dielectric Thin Films: Challenges and Opportunities
Authors: Dey Sandwip K. , Alluri Prasad V.
Published: August 2016

The current trend in electronic-systems technology is to produce compact, lighter, low-power-dissipating, affordable, reliable, and mobile information systems. These factors favor the augmentation of interface systems that sense, source, store, display, and actuate with artificial-intelligence strategies. Herein lies the opportunity to introduce novel technologies based on integrated multi-component oxide (e.g., titanates, niobates, and tantalates) films into usable systems. In particular the oxygen octahedra class of materials (e.g., (Ba,Sr)TiO3 or BST, Pb(Zr,Ti)O3 or PZT, layered SrBi2Ta2O9 or SBT, and polytitanates) that exhibit high permittivities; large electromechanical-coupling coefficients; and pyroelectric, electro-optic, and ferroelectric effects are of interest. They are being evaluated, due to growing demand for compatibility with integrated-circuit (IC) technology, for a variety of applications. These include nonvolatile memories, ultralargescale-integration (ULSI) dynamic random-access memories (DRAMs), decoupling capacitors, piezoelectric sensors and actuators, pyroelectric detectors, and neural network components. Moreover in high-performance multichip-module (MCM) technology, there remains a vital need for the replacement of discrete passive devices, which occupy valuable real estate, by embedded ones. These high-density interconnect structures will play a significant role in nondigital electronic modules including mixed-mode circuits, power conversion and conditioning, microwave transmit/receive (T/R), and optoelectronics. Table I specifically illustrates some electronic applications along with their estimated requirements.
Chemical Dynamics and Bond-Order Potentials
Authors: Brenner Donald W.
Published: August 2016

Tremendous advances in computing speed, increasingly clever algorithms, and more accurate interatomic-force models have made atomistic simulation a powerful tool in many areas of materials science and engineering. Indeed, from traditional areas such as the study of grain boundaries, fracture, and point defects to somewhat less traditional areas such as nanometer-scale engineering and device fabrication, atomistic simulations are providing exciting new data and insights that cannot be obtained in any other way. Central to the success of an atomistic simulation is the use of an appropriate force model. For simulations requiring large systems and/or long times, the computational efficiency offered by classical potential-energy functions is necessary. However, obtaining quantitative results requires a model that can both accurately describe an appropriate database of physical properties and that is transferable to structures and dynamics beyond those to which it is fit. The latter property is especially critical if an atomistic simulation is to have useful predictive capabilities. While an extensive and well-chosen database from which parameters are determined is important, transferability ultimately depends on the chosen functional form. The definitive mathematical form, however, has yet to be developed.

This article covers my attempts to develop classical potential-energy functions based on an empirical bond-order formalism that put qualitative and semiquantitative features of chemistry into large-scale condensed-phase simulations. To help explain this work, the next section gives a brief tutorial of the “chemistry” of few-body potentialenergy surfaces. Although familiar to chemists, the concepts discussed in this section may not be as familiar to mate rials scientists and engineers. A discussion of the bond-order formalism and how it can be related to both solid-state structure and chemical dynamics follows. The article ends with a discussion of two applications of this formalism, modeling chemical dynamics near a shock front and the reactive chemistry of diamond deposition.
Biocatalytic Synthesis of Polyesters Using Enzymes
Authors: Morrow Cary J.
Published: August 2016

Plants and animals have been exploited as sources of materials for centuries but, as our ability to analyze and fractionate them has progressed, the extraordinary range of properties available from materials produced by living systems has continued to grow. Doi, in another article in this issue of theMRS Bulletin, presents a discussion of a group of naturally occurring polyesters related to poly(beta-hydroxybutyrate). These polyesters are formedin vivoby several microorganisms as part of an energy storage scheme. Research on these systems has allowed growth conditions to be found that can lead, in a controlled fashion, to a number of copolymers. Useful materials based on these bacterial polyesters appear to be at hand.

Thein-vivoformation of polyesters in microorganisms also illustrates several of the important reasons for examining biocatalytic polymer synthesis. First, unlike most industrial syntheses of polyesters, the poly(beta-hydroxybutyrate) biosynthesis occurs at a near-ambient temperature using a carbohydrate feedstock. Second, and perhaps most importantly, the stored polyesters are readily biodegraded by the bacteria that manufacture them, so materials based on these polyesters should also be biodegradable. Third, although there are side chains along the polymer backbone, they are introduced in a highly stereo-specific fashion duringin-vivosynthesis, leading to an entirely stereoregular polyester. However, along with these advantages, there are also significant limitations to bacterial polyester synthesis. First, there are some substrates that are not incorporated into the polyester by the bacteria. Second, normal metabolism leads to the polyester, always incorporating a fraction of hydroxybutyrate monomers. Third, the backbone is always comprised of four-atom, A-B type 3-hydroxy acid repeat units with variations appearing in the side chain at carbon-3.
Engineering Enzymes and Antibodies
Authors: Hilvert Donald
Published: August 2016

Phenomenal rate accelerations, exacting selectivities, and mild reaction conditions characterize biocatalysis and have generated considerable interest in nonbiological applications of enzymes. As a result of greater availability and purity, these molecules are now being used increasingly in organic synthesis to prepare complex natural products and novel materials. They are also being exploited industrially in the production of food additives, pharmaceuticals, and fine chemicals.

Unfortunately, for many commercial applications, natural enzymes may be unsuitable. They may be unstable or difficult to isolate; they may function poorly at the temperatures, pH's, and substrate concentrations needed for reaction; or they may lack appropriate specificity. For many chemical reactions, a natural enzyme may not even exist. For example, natural biocatalysts for the synthetically valuable Diels-Alder cycloaddition have yet to be discovered.
Mutated Bacteriortiodopsins: Competitive Materials for Optical Information Processing?
Authors: Hampp N. , Brauchte C. , Oesterhelt D.
Published: August 2016

In 1971, the first halobacterial retinal protein was discovered and named bacteriorhodopsin. Bacteriorhodopsin (BR) is a protein of 248 amino acids that is integrated into the bacterial membrane. It is a light driven pump, moving protons from the inside to the outside of the cell. The resulting gradient drives the production of ATP (adenosine triphosphate) for the organism. In the 1970s, rapidly growing research activities focused on the biochemical and biophysical properties of BR and resulted in a linearly increasing number of publications per year. The constant level of about 200 publications/year in the last decade signifies the steadily growing knowledge about the structure and bioenergetic function of BR and related molecules. Nowadays, BR is one of the best-investigated membrane proteins (e.g., References 3–10).

Only five years after the unusual chemical and photophysical properties of BR were reported, several articles appeared suggesting technical applications of BR for sunlight energy conversion. Although no commercial applications of BR have resulted from these studies, new ideas for application have arisen, covering about 10% of the total publications on BR during the last two years. Is this an indicator of real potential for BR as a biological material in technology?