bluuebunny/crossref_metadata_2025 huggingface dataset:
Materials Issues in Film Archiving: A French Experience
Authors: Aubert Michelle
Published: February 2011

The following article is based on a presentation given as part of Symposium X—Frontiers of Materials Research on December 4, 2002, at the 2002 Materials Research Society Fall Meeting. The cinema is just over 100 years old. From the beginning of motion pictures in the mid-1890s, the materials used for films have been at the heart of cinema technology. The material first used was cellulose nitrate film—unrivaled in its mechanical, physical, and aesthetic qualities, and also dangerously flammable. In the 1950s, cellulose nitrate was replaced, for safety reasons, by cellulose triacetate. Today, polyester film is widely used; nevertheless, the fact remains that the majority of the world's film heritage exists on two main material formats, cellulose nitrate and cellulose triacetate, both of which decay over time. Film archivists are engaged in a race to save historic film footage from being lost forever. Digital technology, now widely used in cinema, does not resolve the issue of the long-term preservation of films because digital formats are still evolving. This article discusses the materials used in motion-picture technology over the years, the mechanisms active in film decomposition, and international efforts to preserve and restore historic films.
High-Performance Packaging of Power Electronics
Authors: Shaw M. C.
Published: February 2011

Packaging of solid-state power electronics is a highly interdisciplinary process requiring knowledge of electronics, heat transfer, mechanics, and materials science. Consequently, there are numerous opportunities for innovations at the interfaces of these complementary fields. This article offers a perspective of the current state of the art and identifies six specific areas for materials-based research in power electronics packaging. The emphasis is on identifying the underlying physical relationships that link the performance of the power electronics system to the microstructure and architectural arrangement of the constituents.
Advanced Fabrics
Authors: Schreuder-Gibson Heidi L. , Realff Mary Lynn
Published: February 2011

This brief article describes the content of the August 2003 issue of MRS Bulletin focusing on Advanced Fabrics. The six articles will feature reviews of advanced fibers, new fabric constructions and design considerations, materials for novel fabric properties, and the incorporation of new elements within fabric structures to add multifunctional, wearable features to clothing.
Progress toward Dynamic Color-Responsive “Chameleon” Fiber Systems
Authors: Hardaker Stephen S. , Gregory Richard V.
Published: February 2011

Fibers and coatings with unique optical, magnetic, and electrical properties are being widely studied for use in both military and commercial applications. New materials are being developed in this research effort, with unique tunable coloration properties across the visible spectrum as well as spanning the infrared and ultraviolet region of the electromagnetic spectrum. These dynamic color-responsive “chameleon” fiber systems will have wide application to a variety of new textile products. These new materials will also allow penetration into markets normally not dependent on textile materials. New markets, such as the optical communication and electronics market areas, will include bio-sensors, detector applications for textile materials, and “smart materials” that can change their color, hue, or depth of shade by application of a static or dynamic electric field for applications such as smart uniforms.
Computational Fluid Dynamics Modeling of Fabric Systems for Intelligent Garment Design
Authors: Barry Jim , Hill Roger , Brasser Paul , Sobera Michal , Kleijn Chris , Gibson Phil
Published: February 2011

Protective clothing provides laboratory and hazardous-materials workers, firefighters, military personnel, and others with the means to control their exposure to chemicals, biological materials, and heat sources. Depending on the specific application, the textile materials used in protective clothing must provide high performance in a number of areas, for example, impermeability to hazardous chemicals, breathability, light weight, low cost, and durability. Models based on computational fluid dynamics have been developed to predict the performance of protective clothing materials. Such models complement testing by enabling property data from laboratory materials tests to be used in predictions of the performance of integrated multilayer garments under varying environmental conditions.
Ultrahigh-Temperature Nb-Silicide-Based Composites
Authors: Bewlay B. P. , Jackson M. R. , Zhao J.-C. , Subramanian P. R. , Mendiratta M. G. , Lewandowski J. J.
Published: February 2011

This article reviews the most recent progress in the development of Nb-silicide-based in situ composites for potential applications in turbine engines with service temperatures of up to 1350°C. These composites contain high-strength Nb silicides that are toughened by a ductile Nb solid solution. Preliminary composites were derived from binary Nb-Si alloys, while more recent systems are complex and are alloyed with Ti, Hf, W, B, Ge, Cr, and Al. Alloying schemes have been developed to achieve an excellent balance of room-temperature toughness, fatigue-crack-growth behavior, high-temperature creep performance, and oxidation resistance over a broad range of temperatures. Nb-silicide-based composites are described with emphasis on processing, microstructure, and performance. Nb silicide composites have been produced using a range of processing routes, including induction skull melting, investment casting, hot extrusion, and powder metallurgy methods. Nb silicide composite properties are also compared with those of Ni-based superalloys.
SiC-Matrix Composite Materials for Advanced Jet Engines
Authors: Naslain R. , Christin F.
Published: February 2011

SiC-matrix composites consist of ceramic fibers embedded in a silicon carbide matrix produced by gas-, liquid-, or solid-phase routes, yielding materials that differ in matrix crystallinity, residual porosity, and thermal properties. These composites can be highly engineered in terms of the nature of the reinforcement, the interphase used to control the fiber-matrix bonding, the matrix, and the seal coating used. SiC-matrix composites are refractory ceramics displaying outstanding mechanical and thermal properties at high temperature. Their durability in oxidizing atmospheres and under load exceeds 1000 h at temperatures of up to ∼1200°C. They have been used to fabricate different components of the hot zone of jet engines with significant weight savings and an increase in performance. This article reviews the state of the art in the processing, materials design, and properties of these composites as well as their applications in advanced jet engines.
Advances in Coating Design for High-Performance Gas Turbines
Authors: Nicholls J. R.
Published: February 2011

Surface engineering is now a key materials technology in the design of future advanced gas-turbine engines. This article focuses on coating systems for hot-gas-path components, which can vary from low-cost aluminide diffusion coatings to the more exotic, and therefore expensive, thermal-barrier coatings. Available coating systems and their relative benefits are reviewed in terms of performance against manufacturing complexity and cost. Future trends in the design of environmental- and thermal-protection coatings are discussed, including the addition of multiple reactive elements, modified aluminide coatings, diffusion-barrier concepts, the design of “smart” corrosion-resistant coatings, and the development of structurally modified, low-thermal-conductivity thermal-barrier coatings.
Half-Metallic Ferromagnetic Oxides
Authors: Coey J.M.D. , Chien C.L.
Published: February 2011

Half-metals are unusual ferromagnets that have electrons at the Fermi level in a single spin state, either spin up or spin down. Of potential interest as sources and analyzers of polarized electrons in spintronic devices, they are usually identified from spin-dependent band-structure calculations. We present a classification scheme for half-metals and then discuss methods for measuring spin polarization based on point contacts or tunnel junctions with ferromagnetic or superconducting counter electrodes. Oxide examples include CrO2, the best-studied half-metal. The half-metallicity tends to be destroyed by increasing temperature and by structural defects. The half-metals that currently offer the best prospects for spintronics applications are those with the highest Curie temperatures, such as magnetite, Fe3O4, and perhaps oxide semiconductors such as Co-doped ZnO.
Electrical Spin Injection and Transport in Semiconductor Spintronic Devices
Authors: Jonker B.T. , Erwin S.C. , Petrou A. , Petukhov A.G.
Published: February 2011

Semiconductor heterostructures that utilize carrier spin as a new degree of freedom offer entirely new functionality and enhanced performance over conventional devices. We describe the essential requirements for implementing this technology, focusing on the materials and interface issues relevant to electrical spin injection into a semiconductor. These are discussed and illustrated in the context of several prototype semiconductor spintronic devices, including spin-polarized light-emitting diodes and resonant tunneling structures such as the resonant interband tunneling diode.
Inkjet Printing of Functional Materials
Authors: Sirringhaus Henning , Shimoda Tatsuya
Published: February 2011

This article introduces the November 2003 issue of MRS Bulletin on Inkjet Printing of Functional Materials. The issue is devoted to the emerging non-graphic-arts uses of inkjet printing as a technique for depositing and patterning functional materials in the liquid phase onto a substrate. The articles provide an overview of a selected range of representative applications in the field of structural ceramics, polymer electronics, and protein chips, and address some of the key challenges that face the broad scientific and industrial community as it attempts to apply a mature and well-developed graphic arts printing technique to the deposition of functional materials.
Inkjet Printing of Light-Emitting Polymer Displays
Authors: Shimoda Tatsuya , Morii Katsuyuki , Seki Shunichi , Kiguchi Hiroshi
Published: February 2011

Based on the concept of a microliquid process, we have developed an organic electroluminescent display using conductive polymers, including light-emitting polymers. The technology of inkjet printing has progressed enough to be used for the microliquid process. First, we describe the process used to form a patterned thin film. This involves inkjet-related technologies, the self-patterning behavior of a microliquid on the substrate, and the drying process that defines the thickness profile and film properties. Some microliquid behaviors and related phenomena, along with properties of the resulting film, were identified as distinct from those coming from a macroscopic liquid, as a result of size effects. By fully utilizing these unique properties of microliquids, we have succeeded in fabricating color-pixel arrays by direct patterning of polymer solutions. As a result, an organic electroluminescent display with a vivid full-color image has been developed.
New Frontiers in the Application of Neutron Scattering to Materials Science
Authors: Richter Dieter , Rowe J. Michael
Published: February 2011

This brief article describes the content of the December 2003 issue of MRS Bulletin on New Frontiers in the Application of Neutron Scattering to Materials Science. New techniques, new instrumentation, and new sources are providing exciting opportunities for the use of neutron scattering in materials research at a time when the pace of research and development is accelerating while the complexity of the issues governing materials use is increasing. At a time such as this, it is critical to use the best tool for the job, and neutron scattering is evolving into a tool that can be used with many others, rather than a technique only for the specialist. It is also providing unprecedented resolution in energy to allow the study of the slow dynamics characteristic of many problems in soft matter and to probe surfaces and interfaces in a unique way. In this issue, we have chosen three areas to emphasize these trends: neutron reflectivity as a probe of surfaces and interfaces, the use of neutrons to study complex fluids, and high-resolution neutron scattering studies of dynamics. We also give a view of the future of neutron sources, with an article outlining the opportunities to be provided by sources proposed or under construction in Europe, Japan, and the United States. It is our hope that this sampling of new opportunities in neutron scattering will encourage wider use of these techniques to help solve the challenging materials research problems of today and tomorrow.
Next-Generation Neutron Sources
Authors: Mason Thomas E. , Arai Masatoshi , Clausen Kurt N.
Published: February 2011

This article gives an overview of current neutron-scattering facilities and illustrates the capabilities of third-generation sources that are now under development. The new science that is driving this development has been illustrated in the articles in this issue of MRS Bulletin and in a previous issue published in 1999 [MRS Bull.24 (12) (1999) p. 14]. The scale of these facilities is such that only three of them are envisaged worldwide, in the Asia Pacific region, Europe, and America. Two construction projects, the spallation neutron sources in the United States (SNS) and in Japan (J-PARC), are now well under way, while the European proposal for a spallation source (ESS) is still awaiting a decision to start construction.
Impact of Single-Event Upsets in Deep-Submicron Silicon Technology
Authors: Baumann Robert
Published: February 2011

The once-ephemeral soft error phenomenon has recently caused considerable concern for manufacturers of advanced silicon technology. Soft errors, if unchecked, now have the potential for inducing a higher failure rate than all of the other reliability-failure mechanisms combined. This article briefly reviews the three dominant radiation mechanisms responsible for soft errors in terrestrial applications and how soft errors are generated by the collection of radiation-induced charge. Scaling trends in the soft error sensitivity of various memory and logic components are presented, along with a consideration of which applications are most likely to require intervention. Some of the mitigation strategies that can be employed to reduce the soft error rate in these devices are also discussed.
Circuit Responses to Radiation-Induced Upsets
Authors: Bernstein Kerry
Published: February 2011

Historically, radiation-induced corruption of data in high-speed complementary metal oxide semiconductor designs has been limited to on-board static random-access memory in various memory caches. Successive generations of scaling, however, have resulted in capacitance reductions in key logic circuits, increasing their vulnerability to these “soft errors.” Charge delivered by radiation events now carries a substantial probability of inducing upsets, not only in bistable elements, but in logic evaluation circuits as well. This article introduces the reader to common logic-circuit topologies in high-speed microprocessors, radiation circuit response mechanisms that can compromise logic evaluation integrity, and existing techniques that mitigate this exposure.
Cosmic-Ray Neutrons on the Ground and in the Atmosphere
Authors: Goldhagen Paul
Published: February 2011

Neutrons from collisions of cosmic rays with the nuclei of atoms in the atmosphere are an irremovable external radiation that causes single-event upsets in microelectronic devices. Predicting soft error rates requires knowledge of the flux and energy distribution of the cosmic-ray-induced neutrons. This article reviews cosmic-ray neutrons in the atmosphere and on the ground, the factors that determine their intensity, and recent calculations and state-of-the-art measurements of neutron spectra covering 12 decades of energy, from the thermal energy range up to 10 GeV.
Superhard Coating Materials
Authors: Chung Yip-Wah , Sproul William D.
Published: February 2011

“Superhard” coating materials are defined by hardness values that exceed 40 GPa. In this issue of MRS Bulletin, we focus on noncarbon-based superhard coatings, with the exception of a review of carbon nitride (CN) materials. Nanometer-scale multilayered nitride coatings were the first to show the superhard property, and these coatings have quickly made their way into industry as protective coatings for cutting-tool operations. Nanocomposite thin films also exhibit superhardness, and some of these materials have hardnesses approaching that of diamond. Cubic boron nitride (c-BN), which is naturally superhard, has proven very difficult to deposit at thicknesses exceeding 0.1 μm, but it is now reported that chemical vapor deposition techniques based on fluorine chemistries can produce c-BN films up to 20 μm thick. The search to produce cubic β-CN has led to the development of noncubic, fullerene-like forms of CN that are both hard and elastic, a very interesting combination of properties that has already been put to use in the hard-disk industry. Overall, the development of hard and superhard coatings during the past 20 years has been remarkable. We have progressed from trying (and often failing) to deposit hard coatings to now designing new nanometer-scale multilayered and nanocomposite coatings that exhibit excellent hardness properties and other high-performancecharacteristics.
Stability of Nanometer-Thick Layers in Hard Coatings
Authors: Barnett Scott A. , Madan Anita , Kim Ilwon , Martin Keith
Published: February 2011

This article reviews two topics related to the stability of hard coatings composed of nanometer-thick layers: epitaxial stabilization and high-temperature stability. Early work on nanolayered hard coatings demonstrated large hardness increases as compared with monolithic coatings, but it was subsequently found that the layers interdiffused at elevated temperatures. More recently, it has been shown that nanolayers exhibit good stability at elevated temperatures if the layer materials are thermodynamically stable with respect to each other and are able to form low-energy coherent interfaces. This article discusses metal/nitride, nitride/nitride, and nitride/boride nanolayers that exhibit good high-temperature stability and hardness values that are maintained (or even increase) after high-temperature annealing. Epitaxial stabilization of nonequilibrium structuresin thin layers is a well-known phenomenon that has been applied to hard nitride materials. In particular, AlN, which crystallizes in the hexagonal wurtzite structure in bulk form, was stabilized in the rock-salt cubic structure in nitride/nitride nanolayers (e.g., AlN/TiN). These results and the current understanding of epitaxial stabilization in hard nanolayers are discussed.
Large-Scale Manufacturing of Nanoscale Multilayered Hard Coatings Deposited by Cathodic Arc/Unbalanced Magnetron Sputtering
Authors: Münz W.-D.
Published: February 2011

Nanoscale multilayered (superlattice) hard coatings can be manufactured in a plastic hardness range (HP) between 25GPa and 55 GPa by a combination of cathodic arc evaporation and unbalanced magnetron sputtering (arc bond sputter technology). Using large-scale industrial physical vapor deposition (PVD) equipment and a sufficiently high pumping speed, multilayered coatings can be deposited by simultaneously operating cathodes without special shutter and shielding facilities in a common reactive-gas atmosphere. The efficiency of the process is in many cases identical to that of TiN and CrN. Temperature-resistant, wear-resistant, and corrosion-resistant coatings of various compositions have been produced under industrial conditions. So far, the main applications concentrate on metal-forming and on cutting die steel, Inconel, stainless steel, and titanium. Applications have also been found in the chemical, textile, medical, and automotive industries.
Recent Advances in Cubic Boron Nitride Deposition
Authors: Zhang W.J. , Bello I. , Lifshitz Y. , Lee S. T.
Published: February 2011

This article reviews recent progress in the deposition of thick, adherent, cubic boron nitride (c-BN) films. Most of the previous work applied ion-assisted physical vapor deposition methods to deposit c-BN films. The ion impact was successful in nucleating c-BN crystallites, but it resulted in a very small crystallite size and introduced stress, which caused the delamination of films thicker than 100 nm. Recent efforts to reduce the stress and obtain thicker films are described. The limited success of these attempts motivated us to explore chemical vapor deposition methods based on fluorine chemistry. We review this work, detailing the success of depositing thick (>20 μ), stress-free, adherent films with a larger crystallite size and significantly better crystalline quality.
Fullerene-like Carbon Nitride: A Resilient Coating Material
Authors: Hultman Lars , Neidhardt Jörg , Hellgren Niklas , Sjöström Hans , Sundgren Jan-Eric
Published: February 2011

Carbon nitride is an emerging material for wear-resistant coatings. The fullerene-like CNx compounds generally exhibit extreme elasticity in combination with a low work of indentation hardness. Yet CNx shows a low-to-moderate resistance to penetration, depending on deposition conditions. Since the deformation energy is predominantly stored elastically, the material possesses an extremely resilient character. This new class of materials consists of sp2-coordinated basal planes that are buckled from the incorporation of pentagons and cross-linked at sp3-hybridized C sites, both of which are caused by structural incorporation of nitrogen. Carbon nitride thus deforms elastically due to bending of the structural units. The orientation, radius of curvature of the basal planes, and the degree of cross-linking between them defines the structure and properties of the material. Due to the unique deformation behavior, the hardness requires special care to assess, but can be very high for films with a large degree of cross-linking. This article is a review of the research on CNx films depositedby reactive magnetron sputtering, with examples from our recent work. The findings are significant for the design of fracture-tough materials.
Foam Structure: From Soap Froth to Solid Foams
Authors: Kraynik Andrew M.
Published: February 2011

The properties of solid foams depend on their structure, which usually evolves in the fluid state as gas bubbles expand to form polyhedral cells. The characteristic feature of foam structure—randomly packed cells of different sizes and shapes—is examined in this article by considering soap froth. This material can be modeled as a network of minimal surfaces that divide space into polyhedral cells. The cell-level geometry of random soap froth is calculated with Brakke's Surface Evolver software. The distribution of cell volumes ranges from monodisperse to highly polydisperse. Topological and geometric properties, such as surface area and edge length, of the entire foam and individual cells, are discussed. The shape of struts in solid foams is related to Plateau borders in liquid foams and calculated for different volume fractions of material. The models of soap froth are used as templates to produce finite element models of open-cell foams. Three-dimensional images of open-cell foams obtained with x-ray microtomography allow virtual reconstruction of skeletal structures that compare well with the Surface Evolver simulations of soap-froth geometry.
Scaffolds for Tissue Engineering
Authors: Karp Jeffrey M. , Dalton Paul D. , Shoichet Molly S.
Published: February 2011

Devices for tissue engineering comprise scaffolds with the appropriate chemistry and architecture to promote cell infiltration and colonization. The scaffold is designed with biology in mind, and thus the architecture and chemistry differ according to tissue type. In this review, we focus on scaffolds for two tissue types—bone and nervous tissue—and describe different approaches used to create them. The appropriate scaffold for a hard tissue such as bone has a high degree of interconnected macroporosity and allows the rapid invasion of cells while maintaining a rigid structure. Several approaches are described for constructing tissue-engineering scaffolds for bone. The appropriate scaffold for soft tissues like nerve fibers (e.g., axons, which conduct nerve impulses) also has a high degree of interconnected pores; however, the pores may require orientation and may be smaller. Homogeneous, high-water-content hydrogels with mechanical properties that match the soft nerve tissue are commonly used as a scaffold, and the methods used to make these are reviewed.
Toward Applications of Ceramic Nanostructures
Authors: Seal Sudipta , Baraton Marie-Isabelle
Published: February 2011

This article serves to introduce the January 2004 issue of MRS Bulletin on progress toward applications of ceramic nanostructures. Conventional ceramic materials are widely used today in areas ranging from structural to biological applications, and in devices as diverse as lasers, semiconductors, sensors, and piezoelectric components. Such materials include oxides, carbides, nitrides, mixed oxides, and composites.Over the last decade, the use of ceramic nanostructures has already changed the approach to materials design in many of these applications, by seeking structural control at the atomic level and tailoring of the engineering properties. The articles in this issue review the advantages of nanoceramics, their application in various fields, and the challenges involved in their fabrication.
Molecular Transport Junctions: An Introduction
Authors: Kagan Cherie R. , Ratner Mark A.
Published: February 2011

This issue of MRS Bulletin on molecular transport junctions highlights the current experimental and theoretical understanding of molecular charge transport and its extension to the rapidly growing areas of molecular and carbon nanotube electronics. This introduction will outline the progress that has been made in understanding the mechanisms of molecular junction transport and the challenges and future directions in exploring charge transport on the molecular scale. In spite of the substantial challenges, molecular charge transport is of great interest for its intrinsic importance to potential single-molecule electronic, thin-film electronic, and optoelectronic applications.
Atomic Force Microscopy of Biological Samples
Authors: Frederix P.L.T.M. , Hoogenboom B.W. , Fotiadis D. , Müller D.J. , Engel A.
Published: February 2011

The atomic force microscope (AFM) allows biomolecules to be observed and manipulated under native conditions. It produces images with an outstanding signal-to-noise ratio and addresses single molecules while the sample is in a buffer solution. Progress in sample preparation and instrumentation has led to topographs that reveal subnanometer details and the surface dynamics of biomolecules. Tethering single molecules between a support and a retracting AFM tip produces force–extension curves, giving information about the mechanical stability of secondary structural elements. For both imaging and force spectroscopy, the cantilever and its tip are critical:the mechanical properties of the cantilever dictate the force sensitivity and the scanning speed, whereas the tip shape determines the achievable lateral resolution.
Imaging, Manipulation, and Spectroscopic Measurements of Nanomagnets by Magnetic Force Microscopy
Authors: Zhu Xiaobin , Grütter Peter
Published: February 2011

Magnetic force microscopy (MFM) is a well-established technique for imaging the magnetic structures of small magnetic particles. In cooperation with external magnetic fields, MFM can be used to study the magnetization switching mechanism of submicrometer-sized magnetic particles. Various MFM techniques allow the measurement of a hysteresis curve of an individual particle, which can then be compared to ensemble measurements. The advantage of using MFM-constructed hysteresis loops is that one can in principle understand the origin of dispersion in switching fields. It is also possible to directly observe the correlation between magnetic particles through careful imaging and control of the external magnetic field. In all of these measurements, attention needs to be paid to avoid artifacts that result from the unavoidable magnetic tip stray field. Control can be achieved by optimizing the MFM operation mode as well as the tip parameters. It is even possible to use the tip stray field to locally and reproducibly manipulate the magnetic-moment state of small particles. In this article, we illustrate these concepts and issues by studying various lithographically patterned magnetic nanoparticles, thus demonstrating the versatility of MFM for imaging, manipulation, and spectroscopic measurements of small particles.
The Application of Atomic Force Microscopy to the Characterization of Industrial Polymer Materials
Authors: Bar Georg K. , Meyers Gregory F.
Published: February 2011

Atomic force microscopy (AFM) is now well established among the tools of choice for the analysis and characterization of materials.Applications of AFM span many industries including chemicals, plastics, pharmaceuticals, and semiconductors.Advancements in AFM instrumentation over the last five years have expanded the range of application of this technology to investigate thermal and mechanical properties of complex materials at high spatial resolution as well as structural and morphological characterization of materials subjected to thermal and mechanical stresses.In particular, this has been an enabling technology for an improved understanding of structure–property relationships in polymeric materials including homopolymers, blends, impact-modified polymer systems, porous polymer systems, and semicrystalline polymers.Practical examples illustrate applications of contact, tapping-mode, phase-imaging, hot-stage, and scanning thermal methods for the characterization of modern industrial polymer materials.
Measurements of In-Plane Material Properties with Scanning Probe Microscopy
Authors: Carpick Robert W. , Eriksson Mark A.
Published: February 2011

Scanning probe microscopy (SPM) was originally conceived as a method for measuring atomic-scale surface topography. Over the last two decades, it has blossomed into an array of techniques that can be used to obtain a rich variety of information about nanoscale material properties. With the exception of friction measurements, these techniques have traditionally depended on tip—sample interactions directed normal to the sample's surface. Recently, researchers have explored several effects arising from interactions parallel to surfaces, usually by deliberately applying a modulated lateral displacement. In fact, some parallel motion is ubiquitous to cantilever-based SPM, due to the tilt of the cantilever. Recent studies, performed in contact, noncontact, and intermittent-contact modes, provide new insights into properties such as structural anisotropy, lateral interactions with surface features, nanoscale shear stress and contact mechanics, and in-plane energy dissipation. The understanding gained from interpreting this behavior has consequences for all cantilever-based scanning probe microscopies.
Germanium Nanostructures on Silicon Observed by Scanning Probe Microscopy
Authors: Tomitori Masahiko , Arai Toyoko
Published: February 2011

Scanning tunneling microscopy and noncontact atomic force microscopy have been used to observe germanium growth on Si(001) and Si(111). The atomically resolved images provide invaluable information on heteroepitaxial film growth from the viewpoints of both industrial application and basic science. We briefly review the history of characterizing heteroepitaxial elemental semiconductor systems by means of scanning probe microscopy (SPM), where the Stranski–Krastanov growth mode can be observed on the atomic scale:the detailed phase transition from layer-by-layer growth to three-dimensional cluster growth was elucidated by the use of SPM. In addition, we comment on the potential of SPM for examining the spectroscopic aspects of heteroepitaxial film growth, through the use of SPM tips with well-defined facets.
Biaxially Textured IBAD-MgO Templates for YBCO-Coated Conductors
Authors: Arendt Paul N. , Foltyn Stephen R.
Published: February 2011

This article reports on the development of second-generation Y1Ba2Cu3O7–(YBCO)-coated conductors deposited on biaxially textured MgO templates fabricated using ion-beam-assisted deposition (IBAD).The materials system architecture and processing techniques used to achieve high critical supercurrents on flexible superalloy substrates is described.The texturing of YBCO films on metal substrates approaches that of films deposited on single-crystal oxide substrates.Critical currents and critical current densities of YBCO films on metal substrates are also equivalent to YBCO films deposited on single-crystal oxides.
YBCO-Coated Conductors Manufactured by High-Rate Pulsed Laser Deposition
Authors: Usoskin Alexander , Freyhardt Herbert C.
Published: February 2011

High-temperature superconductors of the second generation—coated conductors—are based on an architecture of YBCO films deposited on a well-textured substrate tape. The deposition technique used in the processing of YBCO films is responsible not only for both the resulting critical currents in the conductors and the cost efficiency of the employed production route, but also for the ultimate viability of the chosen technology. This article describes an advanced deposition method for YBCO films using high-rate pulsed laser deposition (HR-PLD).An elaborate variable azimuth ablation allows target roughening to be considerably reduced in the course of continuous deposition, and as a result, the integral deposition speed and speed stability can be increased to technologically interesting high values.Well-selected process parameters have been demonstrated to yield high currents of up to 480A/cm-width in short tapes and 360A/cm-width in 6-m-long tapes.Together with quasi-equilibrium heating, the HR-PLD method allows the processing of long-length YBCO-coated conductors and offers a cost-efficient route for their production on an industrial scale.
The Pursuit of the Small: From Grain-Boundary Cavities to Nanocrystalline Metals
Authors: Weertman Julia R.
Published: February 2011

The following article is based on the Von Hippel Award presentation given by Julia Weertman of Northwestern University on December 3, 2003, at the Materials Research Society Fall Meeting in Boston.Weertman received the award for “her lifelong exceptional contributions to understanding the basic deformation processes and failure mechanisms in a wide class of materials, from nanocrystalline metals to high-temperature structural alloys, and for her inspiring role as an educator in materials science.” It has been said that “the best things come in small packages,” and that is certainly in Weertman's mind in this presentation.She has spent much of her career “in pursuit of the small.” In this article, she first looks back at her experiences studying grain-boundary cavities and life in the spaces between grains.She then fast-forwards to modern work on nanocrystalline mechanical behavior, confirming that such nanocrystalline materials are indeed strong, but also brittle.Some of her experiences in studying these phenomena are also described.
Unusual Phenomena in Exchange-Biased Nanostructures
Authors: Schuller Ivan K.
Published: February 2011

The following article is an edited transcript based on the MRS Medalist presentation given by Ivan K.Schuller of the University of California, San Diego, on December 3, 2003, at the Materials Research Society Fall Meeting in Boston.Schuller received the MRS Medal for “his innovative studies of exchange bias in magnetic heterostructures and nanostructures.” Magnetic nanostructures have received increasing attention in recent years, motivated by the interesting phenomena that are apparent when physical size becomes comparable with relevant magnetic length scales.In addition, a number of important potential applications in the sensors and storage industries have emerged. When magnetic nanostructures are in contact with dissimilar magnetic materials, and because their magnetic fields extend considerably outside the physical structure, they are very susceptible to interaction with the surrounding environment.A particularly interesting situation is a ferromagnetic nanostructure in contact with an anti-ferromagnetic substrate.In this “exchange-biased” configuration, a variety of unusual phenomena arise:The reversal mode of the ferromagnet changes considerably, the superparamagnetic transition temperature is affected, and there is a noticeable change in the microscopic spin configuration.A series of experiments will be described involving these phenomena in nanostructured ferromagnets prepared by electron-beam lithography and self-assembly.
Electronic Olfactory Systems Based on Metal Oxide Semiconductor Sensor Arrays
Authors: Pardo Matteo , Sberveglieri Giorgio
Published: February 2011

In this article, we present the Pico electronic nose, an artificial olfactory system based on thin-film semiconductor sensors, and two applications: food-quality control (coffee analysis) and environmental monitoring (odors at a landfill site). For both applications, the electronic nose data correlated with that of panels of trained judges. For the coffee, a global index (called the hedonic index) characterizing the sensorial appeal could be predicted with the electronic nose, and for the landfill site, the intensity of odors could be quantified. In this article, we stress the importance of stable and sensitive sensors, such as metal oxide thin films produced by sputtering, and of multivariate data analysis for extracting knowledge (e.g., gaining selectivity) from the data.
Classification of Ear, Nose, and Throat Bacteria Using a Neural-Network-Based Electronic Nose
Authors: Dutta Ritaban , Gardner Julian W. , Hines Evor L.
Published: February 2011

This article describes the use of an electronic nose (the Cyranose 320) to sense and identify three species of bacteria responsible for ear, nose, and throat (ENT) infections. Gathered data were a complex mixture of different chemical compounds. An innovative approach for classifying the bacteria data was investigated by using a combination of several clustering algorithms. The best results suggest that the three classes of bacteria examined can be predicted with up to 98% accuracy, allowing more precise diagnosis of ENT infection in patients. This type of bacteria data analysis and feature extraction is difficult, but it can be concluded that combined use of the analysis methods described here can solve the feature extraction problem with very complex data and enhance the performance of electronic noses.
Polymer–Carbon Black Composite Sensors in an Electronic Nose for Air-Quality Monitoring
Authors: Ryan M.A. , Shevade A.V. , Zhou H. , Homer M.L.
Published: February 2011

An electronic nose that uses an array of 32 polymer–carbon black composite sensors has been developed, trained, and tested. By selecting a variety of chemical functionalities in the polymers used to make sensors, it is possible to construct an array capable of identifying and quantifying a broad range of target compounds, such as alcohols and aromatics, and distinguishing isomers and enantiomers (mirror-image isomers). A model of the interaction between target molecules and the polymer–carbon black composite sensors is under development to aid in selecting the array members and to enable identification of compounds with responses not stored in the analysis library.
Organic Thin-Film Memory
Authors: Yang Yang , Ma Liping , Wu Jianhua
Published: February 2011

Recently, organic nonvolatile memory devices have attracted considerable attention due to their low cost and high performance. This article reviews recent developments in organic nonvolatile memory and describes in detail an organic electrical bistable device (OBD) that has potential for applications. The OBD consists of a tri-layer of organics/metal nanoclusters/organics sandwiched between top and bottom electrodes. A sufficiently high applied bias causes the metal nanoparticle layer to become polarized, resulting in charge storage near the two metal/organic interfaces. This stored charge lowers the resistance of the device and leads to an electrical switching behavior. The ON and OFF states of an OBD differ in their conductivity by several orders of magnitude and show remarkable bistability—once either state is reached, the device tends to remain in that state for a prolonged period of time. More important, the conductivity states of an OBD can be precisely controlled by the application of a positive voltage pulse (to write) or a negative voltage pulse (to erase). Device performance tests show that the OBD is a promising candidate for high-density, low-cost electrically addressable data storage applications.
Molecular Memories Based on a CMOS Platform
Authors: Kuhr Werner G. , Gallo Antonio R. , Manning Robert W. , Rhodine Craig W.
Published: February 2011

Hybrid complementary metal oxide semiconductor (CMOS)/molecular memory devices are based on a dynamic random-access memory (DRAM) architecture, are fast, have high density, and exhibit low power consumption. These devices use a well-characterized charge storage mechanism to store information based on the intrinsic properties of molecules attached to a CMOS platform. The molecules are designed in a rational way to have known electrical properties and can be incorporated into CMOS devices with only minor modification of existing fabrication methods. Each memory element contains a monolayer of molecules (typically 100,000–1,000,000) to store charge; this process yields a structure that has many times the charge density of a typical DRAM capacitor, obviating the necessity for a trench or stacked capacitor geometry. The magnitude of voltage required to remove each electron is quantized (typically a few hundred millivolts per state), making it much easier to put molecules in a known state and to detect that state with low-power operation. Existing devices have charge retention times that are >1000 times that of semiconductors, and nonvolatile strategies based on simple modifications of existing systems are possible. All of these devices are ultimately scalable to molecular dimensions and will enable the production of memory products as small as state-of-the-art lithography will allow.
Nonvolatile Silicon Memory at the Nanoscale
Authors: Silva Helena , Kim Moon Kyung , Avci Uygar , Kumar Arvind , Tiwari Sandip
Published: February 2011

The key challenges for memories that operate at the nanoscale and that are compatible with mainstream semiconductor processing are in achieving the performance characteristics that make the integration of hundreds of millions or more of such devices feasible. The concept of harnessing a single electron or just a few electrons for memory storage is very appealing, but among the issues to address are the increased variance, smaller signal, and numerous other consequences of the reduced statistics resulting from reduced number of carriers employed. Coupling a few electrons to a transistor channel provides a structure with the power gain and the necessary current for fast memory-state detection as well as compatibility with mainstream processing. Several recent ideas, such as the use of nanocrystals and defects, and decoupling storage from the read process, provide paths to addressing the issues of power, speed, technology compatibility, and variability in these structures.We discuss several approaches to nanoscale nonvolatile silicon memory, their attributes, and the underlying materials issues, with a focus on finding the design compromises necessary to enable their manufacturability.
Solid–Liquid Interfaces: Molecular Structure, Thermodynamics, and Crystallization
Authors: Asta Mark , Spaepen Frans , Veen J. Friso van der
Published: February 2011

Materials phenomena ranging from the melting or freezing of ice to biomineralization in living organisms, to lubrication and the commercial casting of superalloys, are known to be critically influenced by molecular-scale structure and processes occurring at the interfaces between the crystalline solid and liquid phases. The properties of solid–liquid interfaces have long been a topic of intense interest in materials science, primarily because of their role in governing nucleation, growth, and morphological evolution in crystal growth from the melt or solutions.This issue of the MRS Bulletin provides an overview, highlighting new developments in experiment, theory, and modeling techniques that have led to substantial recent progress in the characterization of the molecular-level structural and thermodynamic properties of solid–liquid interfaces and their consequences for a variety of crystallization phenomena.
Step and Kink Dynamics in Inorganic and Protein Crystallization
Authors: Chernov A.A. , Yoreo J.J.De , Rashkovich L.N. , Vekilov P.G.
Published: February 2011

Revived interest in crystal growth from solutions is driven by a variety of demands, including the need to develop an understanding of biomineralization processes in bones, teeth, and shells;and efforts to characterize large optically nonlinear crystals, perfect crystals of proteins, nucleic acids, and complexes such as viruses. Producing and purifying drugs, food, paint, fertilizers, and other polycrystalline materials in industry are other expanding areas that rely on crystal growth from solution. These general practical incentives have activated in-depth studies that revealed new phenomena and raised new fundamental questions: Are thermal fluctuations of steps on a crystal face always fast enough to assure the step propagation at the rate controlled just by molecular incorporation at kinks? Is the Gibbs–Thomson capillarity shift of thermodynamic equilibrium always applicable to evaluate the crystallization driving force of polygonized steps? Is it possible to eliminate the step bunching on a growing crystal face that compromises crystal homogeneity, or at least to mitigate it? In this overview, we will discuss experimental findings and provide state-of-the-art answers to these questions.
Nucleation and the Solid–Liquid Interfacial Free Energy
Authors: Wu David T. , Gránásy László , Spaepen Frans
Published: February 2011

This article reviews the current understanding of the fundamentals of nucleation theory and its use to extract values for the solid–liquid interfacial free energy from experimental and simulation data.
New Developments in Colloid Science
Authors: Weitz D.A. , Russel W.B.
Published: February 2011

This introductory article reviews the topics covered in this issue of MRS Bulletin on New Developments in Colloid Science. Colloidal particles have a long history of importance in a broad range of applications in technology and materials processing. They can be made from many different materials and suspended in a wide variety of solvents. The rheological properties of colloidal suspensions have traditionally been of primary concern in their technological applications, and our understanding of these properties continues to evolve. However, new uses of colloidal particles are also emerging. Because they can be produced to a precise size, colloidal particles are now also being used in novel ways as building blocks for engineering completely new materials, including high-precision filters, controlled-porosity substrates, and photonic devices. In addition, new methods are evolving to alter the shape of the particles and create controlled structures with nonspherical particles. New experimental techniques are allowing improved measurement and increased understanding of the structure, properties, and behavior of colloidal suspensions. Significant progress continues to be made, and the potential uses of colloidal particles continue to grow. This issue presents a snapshot summary of recent developments in this field.