bluuebunny/crossref_metadata_2025 huggingface dataset:
Total Ionizing Dose and Displacement-Damage Effects in Microelectronics
Authors: Foster Charles C.
Published: February 2011

When exposed to radiation, the function of microelectronic devices is not only degraded by single-event phenomena but by cumulative effects. Most of the energy lost by radiation passing through semiconductors is through ionization. Buildup of charge in gate oxide layers and of interface and border traps due to ionization result in semipermanent damage to the device. These effects are known as total ionizing dose effects. A fraction of the energy of the radiation passing through semiconductors is lost to displacement of atoms from their sites in the crystal lattice structure. The buildup of displacement damage with radiation exposure causes gradual but permanent changes in device performance and limits device lifetime in a radiation environment. Displacement damage will be discussed in the context of non-ionizing energy loss.
Scale Effects in Cellular Metals
Authors: Onck P.R.
Published: February 2011

Scale effects in cellular metals can develop when the specimen size is of the order of the cell size. Decreasing the relevant specimen dimensions—height, width, and ligament size (the region between notches in notched specimens)—leads to material strengthening in shear, in indentation, and in notched specimens and to reduced strength and stiffness in uniaxial compression. Experimental size-effect studies were reviewed, and it was concluded from discrete modeling results that scale effects are caused by two different microstructural mechanisms: boundary-layer effects and constraint effects. The first mechanism is active in shear (strong boundary layers) and uniaxial compression (weak boundary layers) and vanishes for specimens larger than two cell sizes and seven cell sizes, respectively. The second mechanism is active in indentation and in notched specimens, leading to a strengthening behavior that is inversely proportional to indenter and ligament size.
In SituX-Ray Tomography Measurements of Deformation in Cellular Solids
Authors: Maire E. , Elmoutaouakkil A. , Fazekas A. , Salvo L.
Published: February 2011

The use of microtomography to study the structure and especially the deformation modes of cellular solids is reviewed in this article. First, the technique is described in detail. Examples illustrating the power of the coupling ofin situdeformation with three-dimensional (3D) imaging, drawn from the recent literature and the authors' own work, are then given. The most detailed example is the study of the deformation modes of several samples made of different aluminum foams. Four kinds of closed-cell foams were investigated, corresponding to different routes available today for their manufacture. The initial macrostructure was quantified using the 3D images combined with 3D granulometry, allowing retrieval of pertinent information about the cell size and the wall and strut thicknesses. The global behavior exhibited by the foams during thein situcompression experiments was shown to vary from one brand of material to another. Some of these variations can be explained by differences in the known microstructure and the measured macrostructure of the samples.
Cellular Ceramics: Intriguing Structures, Novel Properties, and Innovative Applications
Authors: Green David J. , Colombo P.
Published: February 2011

Cellular ceramics are a class of high-porosity materials that are used or are being considered for a wide range of technological applications. A critical aspect of this development is the materials science approach required to understand the relationships between the properties of these materials and their structure. Of particular interest are the parameters that control mechanical reliability, as ceramic materials are usually brittle. In addition, it is critical to understand the way in which processing methods can influence the cellular structure. This article emphasizes one particular group of cellular ceramics known as ceramic foams. Understanding these materials involves various interdisciplinary scientific challenges in characterizing structure, developing micromechanical models, experimentally measuring properties, developing new processing approaches, and optimizing performance.
Photonic Materials for Optical Communications
Authors: Hillmer Hartmut , Germann Roland
Published: February 2011

An overview of key materials for optical communications, including semiconductors, dielectrics, glasses, and organics, is presented in this issue of MRS Bulletin. Materials quality is in all cases crucial for advanced device and system performance. Materials properties and important problems are reviewed, and their impact on the performance of state-of-the-art optical devices is assessed and demonstrated by means of selected examples.
Material Properties of III–V Semiconductors for Lasers and Detectors
Authors: Tu Charles W. , K.L.Yu Paul
Published: February 2011

We describe how the material properties of III–V semiconductors, including bandgap, band structure, band offset, refractive index, absorption, and ionization coefficient, are exploited for lasers and photodetectors for fiber-optic communications. The material systems discussed for 1.3 μm and 1.55 μm light emission include the more traditional GaInAsP and AlGaInAs on InP, the more recently investigated GaInAs quantum dots and low-bandgap GaInNAs on GaAs as well as GaAsSb/GaAs Type II structures, and the potentially viable GaN/AlGaN from intersubband transitions (i.e., between quantized conduction-band energy levels). As an example of photodetector applications, GaInAsP/InP and wafer-fused GaInAs/Si are discussed in terms of gain and noise factor for use in avalanche photodiodes with separate absorption and multiplication regions.
Combined Densification and Thermo-Hydro-Mechanical Processing of Wood
Authors: Navi Parviz , Heger Frédéric
Published: February 2011

The process of heating and compressing wood to improve its properties or reform it to a new shape has been known for decades. Such improvements are usually accompanied by “shape memory,” where the deformation produced by compression is not permanent, and the material recovers when re-moistened and heated. The combination of densification and a thermo-hydro-mechanical (THM) treatment can transform wood into a new material with improved mechanical properties, decreased sensitivity to moisture, increased durability, and no shape-memory effects. This article presents the principles of combined densification and THM processing, the products and experimental results, the origin of the shape-memory effect and its elimination by THM treatment, and the potential use of THM-processed densified wood in construction applications.
Molecular Electronics: Theory and Device Prospects
Authors: Ghosh A.W. , Damle P.S. , Datta S. , Nitzan A.
Published: February 2011

Understanding current flow through molecular conductors involves simulating the contact surface physics, the molecular chemistry, the device electrostatics, and the quantum kinetics of nonequilibrium transport, along with more sophisticated processes such as scattering and many-body effects.We summarize our current theoretical understanding of transport through such nanoscale devices. Our approach is based on self-consistently combining the nonequilibrium Green's function (NEGF) formulation of transport with an electronic structure calculation of the molecule.We identify the essential ingredients that go into such a simulation. While experimental data for many of the inputs required for quantitative simulation are still evolving, the general framework laid down in this treatment should still be applicable.We use these concepts to examine a few prototype molecular devices, such as wires, transistors, and resonant-tunneling diodes.
Electrical and Spectroscopic Characterization of Molecular Junctions
Authors: Kushmerick James G. , Allara David L. , Mallouk Thomas E. , Mayer Theresa S.
Published: February 2011

The design of future molecular electronic devices requires a firm understanding of the conduction mechanisms that determine their electrical characteristics. Progress toward this goal has been hindered by complications in controlling the exact configuration and makeup of fabricated molecular junctions, thus limiting the availability of quantitative experimental data for developing cohesive theories to model and predict molecular transport. This article summarizes recent research aimed at developing well-controlled systems for comparing molecular conduction and vibrational spectra using crossed-wire and in-wire metal–molecule–metal junctions. Systematic variations in molecular structure and metal–molecule contacts show strong quantitative agreement in device properties, while spectroscopic data provide evidence that the properties are due to the molecular junction. Further investigations using these and other molecular junction test beds will provide the needed experimental data to advance fundamental understanding of molecular transport and facilitate future molecular electronics applications.
Nanoceramics in Biomedical Applications
Authors: Ben-Nissan B.
Published: February 2011

An improved understanding of the interactions at the nanoscale level between the bioceramics in medical implants and the hard or soft tissues in the human body could contribute significantly to the design of new-generation prostheses and postoperative patient management strategies.Overall, the benefits of advanced ceramic materials in biomedical applications have been universally accepted, specifically in terms of their strength, biocompatibility, hydrophilicity, and wear resistance in articulating joints.The continuous development of new-generation implants utilizing nanocoatings with novel nanosensors and devices is leading to better compatibility with human tissue and improved well-being and longevity for patients. This article gives a short overview of bioceramics and reexamines key issues of concern for processing and applying nanoceramics as biomaterials.
Bio-Resorbable Nanoceramics for Gene and Drug Delivery
Authors: Kriven Waltraud M. , Kwak Seo-Young , Wallig Matthew A. , Choy Jin-Ho
Published: February 2011

Nanoscale ceramic particles, such as layered double hydroxides (LDHs), have been developed to deliver drugs or genes into biological cells. In this article, we describe the controlled-release properties of LDHs as drug delivery carriers, the formation of bio-LDH nanohybrids, theirin vivoandin vitrocytotoxicity tests, and their potential as anticancer gene delivery carriers. Unstable biomolecules can be intercalated into LDHs, displacing the interlayer anions; the drug or gene's negative charge is thus shielded, enabling penetration into the cell. In the slightly acidic environment of the cell, ceramic nanoplatelets of ∼100 nm diameter dissolve, thus releasing the intercalates in a controlled manner.
Synthesis, Analysis, and Electrical Property Measurements of Compound Nanotubes in the B-C-N Ceramic System
Authors: Golberg Dmitri , Bando Yoshio , Dorozhkin Pavel , Dong Zhen-Chao
Published: February 2011

Nanotubular structures in the B-C-N ceramic system represent an intriguing alternative to conventional carbon nanotubes.Because of the ability to widely vary the chemical composition of nanotubes within the B-C-N ternary phase diagram and to change the stacking of C-rich or BN-rich tubular shells in multiwalled structures, a wide horizon opens up for tuning nanostructure electrical properties.Pure carbon nanotubes are metals or narrow-bandgap semiconductors, depending on the helicity and diameter, whereas those of BN are insulators with a ∼5.0eV gap independent of these parameters.Thus, the relative B/C/N ratios and/or BN-rich and C-rich domain spatial arrangements, rather than tube helicity and diameter, are assumed to primarily determine the B-C-N nanotube electrical response.This characteristic is highly valuable for nanotechnology:while tube diameter and helicity are currently difficult to control, continuous doping of C with BN, or vice versa, proceeds relatively easily due to the isostructural nature of layered C and BN materials.In this article, recent progress in the synthesis, microscopic analysis, and electrical property measurements of a variety of compound nanotubes in the ceramic B-C-N system is documented and discussed.
The RABiTS Approach: Using Rolling-Assisted Biaxially Textured Substrates for High-Performance YBCO Superconductors
Authors: Goyal Amit , Paranthaman M. Parans , Schoop U.
Published: February 2011

This article provides an overview of the fabrication of epitaxial, biaxially aligned buffer layers on rolling-assisted biaxially textured substrates (RABiTS) as templates for YBCO films carrying high critical current densities.The RABiTS technique uses standard thermomechanical processing to obtain long lengths of flexible, biaxially oriented substrates with smooth surfaces.The strong biaxial texture of the metal is conferred to the superconductor by the deposition of intermediate metal and/or oxide layers that serve both as a chemical and a structural buffer.Epitaxial YBCO films with critical current densities exceeding 3 106A/cm2at 77K in self-field have been grown on RABiTS using a variety of techniques and demonstrate magnetic-field-dependent critical current values that are similar to those of epitaxial films on single-crystal ceramic substrates.The RABiTS architecture most commonly used consists of a CeO2(sputtered)/YSZ (sputtered)/Y203(e-beam)/Ni-W alloy.

The desired texture of the base metal has been achieved in 100 m lengths and 10cm widths.Scaleable and cost-effective techniques are also being pursued to deposit the epitaxial multilayers.The results discussed here demonstrate that this technique is a viable route for the fabrication of long lengths of high-critical-current-density wire capable of carrying high currents in magnetic fields and at temperatures accessible by cooling with relatively inexpensive liquid nitrogen (up through the 77K range).
Research and Development of Biaxially Textured IBAD-GZO Templates for Coated Superconductors
Authors: Iijima Yasuhiro , Kakimoto Kazuomi , Yamada Yutaka , Izumi Teruo , Saitoh Takashi , Shiohara Yuh
Published: February 2011

Ion-beam-assisted deposition (IBAD) has been used to prepare biaxially textured templates necessary to realizing high superconducting performance in coated conductors.The IBAD method is characterized by the direct deposition of sharply aligned templates on nontextured metal substrates using fluorite-like oxide films (yttrium-stabilized zirconia, Gd2Zr2O7, etc.).Recent progress in vacuum technology for IBAD has made it possible to reproducibly fabricate long lengths (100 m) of IBAD-GZO templates.Continuous deposition of YBCO films on these templates has been achieved by pulsed laser deposition (PLD).Furthermore, a new approach to improving the texture of IBAD templates was found by using CeO2 films grown by PLD.Trifluoroacetate-based metalorganic deposition has also been used instead of PLD to produce superconducting layers on IBAD buffered tapes, aiming at a low-cost process.This article reviews progress in the research and development of biaxially textured templates produced using IBAD and their subsequent use in fabricating superconducting tapes and wires by means of several processes.
Evaporation-Induced Self-Assembly: Functional Nanostructures Made Easy
Authors: Brinker C. Jeffrey
Published: February 2011

The following article is an edited transcript based on the MRS Medalist presentation given by C. Jeffrey Brinker (Sandia National Laboratories and the University of New Mexico) on December 3, 2003, at the Materials Research Society Fall Meeting in Boston. Brinker received the Medal for “his pioneering application of principles of sol-gel chemistry to the self-assembly of functional nanoscale materials.” Nature combines hard and soft materials, often in hierarchical architectures, to obtain synergistic, optimized properties with proven, complex functionalities. Emulating natural designs in robust engineering materials using efficient processing approaches represents a fundamental challenge to materials chemists. This presentation reviews progress on understanding so-called evaporation-induced silica/surfactant self-assembly (EISA) as a simple, general means of preparing porous thin-film nanostructures. Such porous materials are of interest for membranes, low-dielectric-constant (low-k) insulators, and even ‘“nano-valves” that open and close in response to an external stimulus. EISA can also be used to simultaneously organize hydrophilic and hydrophobic precursors into hybrid nanocomposites that are optically or chemically polymerizable, patternable, or adjustable.
Novel Materials and Applications of Electronic Noses and Tongues
Authors: Gouma Perena , Sberveglieri Giorgio
Published: February 2011

This introductory article describes the content of the October 2004 issue ofMRS Bulletinfocusing on novel materials and applications of electronic noses and tongues.The articles in this issue review the state of the art in materials, devices, and data processing algorithms used in electronic olfaction and taste systems. The most common gas- and liquid-phase analyte detection tools are presented and compared with traditional chemical analysis instrumentation such as gas chromatography/mass spectroscopy systems. Metal oxides, polymer/polymer composites, and dyes are covered in these articles as key sensing materials. Resistive, optical, electrochemical, and other types of electronic nose and tongue systems are reviewed, and their use in diverse applications, including environmental and food-quality monitoring and medical diagnostics, is discussed.
An Optoelectronic Nose:“Seeing” Smells by Means of Colorimetric Sensor Arrays
Authors: Suslick Kenneth S.
Published: February 2011

A new approach to general sensors for odors and volatile organic compounds (VOCs) using thin films of chemically responsive dyes as a colorimetric sensor array is described. This optoelectronic “nose,” by using an array of multiple dyes whose colors change based on the full range of intermolecular interactions, provides enormous discriminatory power among odorants in a simple device that can be easily digitally imaged. High sensitivities (ppb) have been demonstrated for the detection of biologically important analytes such as amines, carboxylic acids, and thiols. By the proper choice of dyes and substrate, the array can be made essentially nonresponsive to changes in humidity.
High-Performance Emerging Solid-State Memory Technologies
Authors: Goronkin Herb , Yang Yang
Published: February 2011

This article introduces the November 2004 issue of MRS Bulletin on the state of the art in solid-state memory and storage technologies.The memory business drives hundreds of billions of dollars in sales of electronic equipment per year. The incentive for continuing on the historical track outlined by Moore's law is huge, and this challenge is driving considerable investment from governments around the world as well as in private industry and universities. The problem is this: recognizing that current approaches to semiconductor-based memory are limited, what new technologies can be introduced to continue or even accelerate the pace of complexity? The articles in this issue highlight several commercially available memories, as well as memory technologies that are still in the research and development stages. What will become apparent to the reader is the huge diversity of approaches to this problem.
Overview of Phase-Change Chalcogenide Nonvolatile Memory Technology
Authors: Hudgens S. , Johnson B.
Published: February 2011

Phase-change nonvolatile semiconductor memory technology is based on an electrically initiated, reversible rapid amorphous-to-crystalline phase-change process in multicomponent chalcogenide alloy materials similar to those used in rewriteable optical disks. Long cycle life, low programming energy, and excellent scaling characteristics are advantages that make phase-change semiconductor memory a promising candidate to replace flash memory in future applications. Phase-change technology is being commercialized by a number of semiconductor manufacturers. Fundamental processes in phase-change semiconductor memory devices, device performance characteristics, and progress toward commercialization of the technology are reviewed.
The Influence of Order on the Nucleation Barrier
Authors: Kelton K.F. , Greer A.L. , Herlach D.M. , Holland-Moritz D.
Published: February 2011

While it is conventionally thought that liquids turn to solids at their “freezing” point, it is often the case that materials must be supercooled (cooled below the freezing temperature) before nucleation actually happens. There is growing evidence that coupled processes, including chemical–structural ordering and orientational–translational ordering, are among the factors that affect exactly when and how nucleation occurs in liquids and crystals. Recent density functional calculations have demonstrated that such coupled routes, which are not incorporated within the one-dimensional framework of the classical theory, can dramatically influence the overall nucleation process. Here, some recently observed cases in metal alloys are discussed, establishing a relationship between developing order in undercooled liquids and the nucleation barrier, the influence of magnetic ordering on nucleation in Co-based melts, and the role of interfacial structure and chemistry on the catalytic efficiency of inoculants for heterogeneous nucleation.
In Situ Transmission Electron Microscopy Studies of the Solid–Liquid Interface
Authors: Howe James M. , Saka Hiroyasu
Published: February 2011

In situtransmission electron microscopy (TEM) studies allow one to determine the structure, chemistry, and kinetic behavior of solid–liquid (S–L) interfaces with subnanometer spatial resolution. This article illustrates some important contributions ofin situTEM to our understanding of S–L interfaces in Al-Si alloys and liquid In particles in Al and Fe matrices.Four main areas are discussed:ordering in the liquid at a S–L interface, compositional changes across the interface, the kinetics and mechanisms of interface migration, and the contact angles and equilibrium melting temperature of small particles.Results from these studies reveal that (1)partially ordered layers form in the liquid at a Si{111} S–L interface in an Al–Si alloy, (2)the crystalline and compositional changes occur simultaneously across an Al S–L interface, (3)the Al interface is diffuse and its growth can be followed at velocities of a fewnm/s at extremely low undercoolings, and (4)the melting temperature of In particles less than ~ 10 nm in diameter can be raised or lowered in Al or Fe, depending on the contact angle that the S–L interface makes at the three-phase junction. These results illustrate the benefits of in situ TEM for providing fundamental insight into the mechanisms that control the behavior of S–L interfaces in materials.
Structural Ordering at the Solid–Liquid Interface
Authors: Veen J.F. van der , Reichert H.
Published: February 2011

Many processes in nature and technology are based on the static and dynamic properties of solid–liquid interfaces. Prominent examples are crystal growth, melting, and recrystallization. These processes are strongly affected by the local structure at the solid–liquid interface. Therefore, it is mandatory to understand the change in the structure across the interface. The break of the translational symmetry at the interface induces ordering phenomena, and interactions between the liquid's molecules and the atomically corrugated solid surface may induce additional ordering effects. In the past decade, new techniques have been developed to investigate the structural properties of such (deeply) buried interfaces in their natural environment. These methods are based on deeply penetrating probes such as brilliant x-ray beams, providing full access to the structure parallel and perpendicular to the interface. Here, we review the results of a number of case studies including liquid metals in contact with Group IV elements (diamond and silicon), where charge transfer effects at the interface may come into play. Another particularly important liquid in our environment is water. The structural properties of water vary widely as it is brought in contact with other materials. We will then proceed from these seemingly simple cases to complex fluids such as colloids.
Building Materials by Packing Spheres
Authors: Manoharan Vinothan N. , Pine David J.
Published: February 2011

An effective way to build ordered materials with micrometer- or submicrometer-sized features is to pack together monodisperse (equal-sized) colloidal particles. But most monodisperse particles in this size range are spheres, and thus one problem in building new micrometer-scale ordered materials is controlling how spheres pack. In this article, we discuss how this problem can be approached by constructing and studying packings in the few-sphere limit. Confinement of particles within containers such as micropatterned holes or spherical droplets can lead to some unexpected and diverse types of polyhedra that may become building blocks for more complex materials. The packing processes that form these polyhedra may also be a source of disorder in dense bulk suspensions.
High-Resolution Three-Dimensional X-Ray Microscopy
Authors: Larson Bennett C. , Lengeler Bruno
Published: February 2011

This issue of MRS Bulletin focuses on the rapid progress that is ongoing in the development of hard x-ray microscopies with three-dimensional spatial resolutions ranging from micrometers to nanometers. The individual articles provide a crosscut of developments in hard x-ray projection tomography microscopy for imaging density and chemical fluctuations in crystalline and noncrystalline materials; large-angle diffractionbased, spatially resolved imaging of local structure, orientation, and strain distributions in crystalline materials; and emerging coherent diffraction imaging for nanometer-range Fourier transform imaging of crystalline and noncrystalline materials.
Three-Dimensional X-Ray Structural Microscopy Using Polychromatic Microbeams
Authors: Ice Gene E. , Larson Bennett C.
Published: February 2011

In this article, the authors describe the principle and application of differential-aperture x-ray microscopy (DAXM). This recently developed scanning x-ray microprobe technique uses a confocal or traveling pinhole camera approach to determine the crystal structure, crystallographic orientation, and elastic and plastic strain tensors within bulk materials. The penetrating properties of x-rays make the technique applicable to optically opaque as well as transparent materials, and it is nondestructive; this provides for in situ, submicrometer-resolution characterization of local crystal structure and for measurements of microstructure evolution on mesoscopic length scales from tenths to hundreds of micrometers. Examples are presented that illustrate the use of DAXM to study grain and subgrain morphology, grain-boundary types and networks, and local intra- and intergranular elastic and plastic deformation. Information of this type now provides a direct link between the actual structure and evolution in materials and increasingly powerful computer simulations and multiscale modeling of materials microstructure and evolution.
Imaging and Characterization of Molecules and One-Dimensional Crystals Formed within Carbon Nanotubes
Authors: Sloan J. , Luzzi D.E. , Kirkland A.I. , Hutchison J.L. , Green M.L.H.
Published: February 2011

The imaging and characterization of individual molecules and atomically thin, effectively one-dimensional crystals of rock salt and other halides encapsulated within single-walled carbon nanotubes are reviewed in this article. These species were imaged by conventional and super-resolved high-resolution transmission electron microscopy and by scanning tunneling microscopy, revealing the detailed atomic structure of these nanoscopic species.
The Rheology of Cementitious Materials
Authors: Flatt Robert J. , Martys Nicos , Bergström Lennart
Published: February 2011

The introduction of a new generation of dispersants in concrete allow this material to exhibit self-compacting properties in its fresh state and high durability and mechanical strength in its hardened state. These properties translate into many practical advantages for the construction field.Two of the most important are reducing the ecological impact of this sector of industry and reducing the labor-intensive work associated with placing ordinary concrete by vibration. In this article, it will be shown that knowledge of colloidal science has proven essential in the development of this new generation of dispersants for concrete. Indeed, the polymer molecules used in these dispersants are specifically designed to induce steric repulsion between cement particles, reducing their agglomeration and allowing high workability of fresh concrete prior to setting. While the linkage between interparticle forces and the rheological behavior of cement pastes is still only semiquantitative, recent advances in the modeling of concrete rheology show very promising results in terms of handling aggregates with a wide distribution of particle sizes and shapes. However, accurate modeling requires reliable input on the interaction of the dispersant with the hydrating cement at the molecular level, which is identified as a future research challenge.
Production Aspects of Organic Photovoltaics and Their Impact on the Commercialization of Devices
Authors: Brabec Christoph J. , Hauch Jens A. , Schilinsky Pavel , Waldauf Christoph
Published: February 2011

The essential cost-driving factor for the production of classical photovoltaic devices is the expensive investment in costly semiconductor processing technologies. This unfavorable cost structure has so far prohibited the technology from having a significant impact on global energy production. Nevertheless, the continued high interest in photovoltaics originates from the fact that they represent the only truly portable renewable-energy conversion technology available today. Therefore, the potential of fabricating organic photovoltaic elements on low-cost, thin plastic substrates by standard printing and coating techniques and packaged by lamination is not only intriguing, but highly attractive from a cost standpoint. In this article, we discuss the economic and technical production aspects for organic photovoltaics.
Enhanced Light Transmission through Subwavelength Holes
Authors: Dintinger José , Degiron Aloyse , Ebbesen Thomas W.
Published: February 2011

The transmission of light through a hole was thought to be very weak when all of the lateral dimensions of the hole were much smaller than the wavelength of the light.The discovery of enhanced transmission has changed this view, raising fundamental questions and leading to many practical applications ranging from photonics to chemical sensing. A key feature of the transmission process is the activation of surface plasmons. In this article, we review the present understanding of this phenomenon and illustrate its potential through several examples of applications in different fields.
Electronic Mayonnaise: Uniting the Sciences of “Hard” and “Soft” Matter
Authors: Schmalian J. , Wolynes P.G.
Published: February 2011

“Soft” condensed-matter science (also known as colloid chemistry) has revealed the nearly zoological complexity of long-lived structures that can arise from the competing interactions working in concert with thermal fluctuations both near and far from equilibrium. “Hard” condensed-matter science has revealed the stark beauty of elementary excitations shimmering on a placid quantum Fermi sea. The study of strongly correlated electronic states of matter is forcing us to unify these often disparate branches of materials science. Explaining confusing phenomena occurring in high-temperature superconductors and related materials seems to require that long-lived electronic structures be generated largely on their own, but perhaps with a little help from lattice disorder.We will explain the fruitful analogy between such systems and classical colloidal systems such as mayonnaise. Ordered crystalline, striped, or checkerboard phases and striped glasses emerge as candidate forms of highly correlated matter that may explain many puzzling observations of electronic materials.
Scaling and the Magnetic Origin of Emergent Behavior in Correlated Electron Superconductors
Authors: Curro Nicholas , Fisk Zachary , Pines David
Published: February 2011

We discuss three examples of emergent behavior in correlated electron matter, in which the discovery of scaling of several measured quantities with a single energy scale provides a key clue to a common magnetic origin: the emergence of itinerant (mobile) electronic behavior from the Kondo lattice of localized f electrons found in cerium- and uranium-based heavy fermion materials; the emergence of unconventional superconductivity in the cuprate and “high-temperature” heavy electron Ce- and Pu-based 1-1-5 superconductors; and the emergence of pseudogap behavior in the underdoped and optimally doped cuprate superconductors.We conclude with some speculation on ways in which these novel perspectives might be used to design new materials.
The Materials Science of Protein Aggregation
Authors: Cox D.L. , Lashuel H. , Lee K.Y.C. , Singh R.R.P.
Published: February 2011

Numerous human diseases are associated with conformational change and aggregation of proteins, including Alzheimer's, Parkinson's, prion diseases (such as mad cow disease), familial amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease), Huntington's, and type II (mature onset) diabetes. In many cases, it has been demonstrated that conformational change and aggregation can occur outside living cells and complex biochemical networks. Hence, approaches from materials and physical science have enhanced our understanding of the role of protein aggregation in these diseases at the molecular and nanoscale levels. In this article, we will review what is known about these protein structures from the perspective of materials science, focusing on the details of emergent oligomeric and nanotube-like structures, their interactions with model lipid bilayers, how the structures relate to observed biological phenomena, and how protein aggregation and amyloid formation can be employed for the good in biology and materials science.
Addressing Grand Energy Challenges through Advanced Materials
Authors: Dresselhaus M. S. , Crabtree G. W. , Buchanan M. V.
Published: February 2011

The following article is based on the plenary presentation given by Mildred S. Dresselhaus of the Massachusetts Institute of Technology on November 29, 2004, at the Materials Research Society Fall Meeting in Boston. Advanced materials offer new promise for addressing some of the grand societal challenges of our future, including that of global energy. This article will review opportunities that have opened up at the nanoscale, with materials of reduced dimensionality and enhanced surface-to-volume ratio. Some examples of research accomplishments and opportunities at the nanoscale will be described, with special attention given to the potential for advanced materials and nanoscience to have an impact on the grand challenges related to a sustainable energy supply for the 21st century and beyond.
Polymer Electrolyte Membrane Technology for Fuel Cells
Authors: Rajendran Raj G.
Published: February 2011

The concept of using an ion-exchange membrane as an electrolyte separator for polymer electrolyte membrane (PEM) fuel cells was first reported by General Electric in 1955. However, a real breakthrough in PEM fuel cell technology occurred in the mid-1960s after DuPont introduced Nafion®, a perfluorosulfonic acid membrane. Due to their inherent chemical, thermal, and oxidative stability, perfluorosulfonic acid membranes displaced unstable polystyrene sulfonic acid membranes.Today, Nafion® and other related perfluorosulfonic acid membranes are considered to be the state of the art for PEM fuel cell technology. Although perfluorosulfonic acid membrane structures are preferred today, structural improvements are still needed to accommodate the increasing demands of fuel cell systems for specific applications. Higher performance, lower cost, greater durability, better water management, the ability to perform at higher temperatures, and flexibility in operating with a wide range of fuels are some of the challenges that need to be overcome before widespread commercial adoption of the technology can be realized. The present article will highlight the membrane properties relevant to PEM fuel cell systems, the development history of perfluorosulfonic acid membranes, and the current status of R&D activities in PEM technology.
Organic-Based Photovoltaics: Toward Low-Cost Power Generation
Authors: Shaheen Sean E. , Ginley David S. , Jabbour Ghassan E.
Published: February 2011

Harvesting energy directly from sunlight using photovoltaic technology is a way to address growing global energy needs with a renewable resource while minimizing detrimental effects on the environment by reducing atmospheric emissions. This issue of MRS Bulletin on “Organic-Based Photovoltaics” looks at a new generation of solar cells that have the potential to be produced inexpensively. Recent advances in solar power conversion efficiencies have propelled organic-based photovoltaics out of the realm of strictly fundamental research at the university level and into the industrial laboratory setting. Fabricated from organic materials—polymers and molecules—these devices are potentially easier to manufacture than current technologies based on silicon or other materials. In this introductory article, we describe the motivation for pursuing research in this field and provide an overview of the various technical approaches that have been developed to date.We conclude by discussing the challenges that need to be overcome in order for organic photovoltaics to realize their potential as an economically viable path to harvesting energy from sunlight.
Making Things by Self-Assembly
Authors: Boncheva Mila , Whitesides George M.
Published: February 2011

Self-assembly—the spontaneous generation of order in systems of components—is ubiquitous in chemistry; in biology, it generates much of the functionality of the living cell. Self-assembly is relatively unused in microfabrication, although it offers opportunities to simplify processes, lower costs, develop new processes, use components too small to be manipulated robotically, integrate components made using incompatible technologies, and generate structures in three dimensions and on curved surfaces. The major limitations to the self-assembly of micrometer- to millimeter-sized components (mesoscale self-assembly) do not seem to be intrinsic, but rather operational: selfassembly can, in fact, be reliable and insensitive to small process variations, but fabricating the small, complex, functional components that future applications may require will necessitate the development of new methodologies. Proof-of-concept experiments in mesoscale self-assembly demonstrate that this technique poses fascinating scientific and technical challenges and offers the potential to provide access to hard-to-fabricate structures.
The Photoconversion Mechanism of Excitonic Solar Cells
Authors: Gregg Brian A.
Published: February 2011

Excitonic solar cells (XSCs) function by a mechanism that is different than that of conventional solar cells.They have different limitations on their open circuit photovoltages, and their behavior cannot be interpreted as if they were conventional p–n heterojunctions. Exciton dissociation at the heterojunction produces electrons on one side of the interface already separated from the holes produced on the other side of the interface. This creates a powerful photoinduced interfacial chemical potential energy gradient that drives the photovoltaic effect, even in the absence of a built-in electrical potential. The maximum thermodynamic efficiency achievable in an XSC is shown to be identical to that of a conventional solar cell, with the substitution of the optical bandgap in the XSC for the electronic bandgap in the conventional cell. This article briefly reviews the photovoltaic mechanism of XSCs, the limitations on their photovoltage, and their maximum achievable efficiency.
Biointerface Science
Authors: Chilkoti Ashutosh , Hubbell Jeffrey A.
Published: February 2011

Biointerface science, defined as the study and control of biomolecular interactions at surfaces, is a critical component of many aspects of biotechnology, but it has only recently begun to attract the attention it deserves as a unique interdisciplinary research area. This issue of MRS Bulletin explores the rich diversity of function provided by biomolecules at interfaces and the unparalleled opportunities for applications, which range from clinical diagnostics, biomaterials, and tissue engineering to genomics and proteomics. This diversity will continue to drive the evolution of biointerface science.
Dynamic Substrates for Cell Biology
Authors: Mrksich Milan
Published: February 2011

The development of dynamic substrates that can modulate the behavior of adherent cells is important for fundamental studies in cell biology, applications in biomaterials, and engineering microsystems that combine cellular and material components. This review outlines several strategies based on physical transduction schemes (including electrical, photochemical, thermal, and mechanical forces) for designing interfaces that are active and can signal changes in the behavior of attached cells.
The Limits to Organic Photovoltaic Cell Efficiency
Authors: Forrest Stephen R.
Published: February 2011

We consider the fundamental limits to organic solar cell efficiency, and the schemes that have been used to overcome many of these limitations. In particular, the use of double and bulk heterojunctions, as well as tandem cells employing materials with high exciton diffusion lengths, is discussed.We show that in the last few years, a combination of strategies has led to a power conversion efficiency of ηp = 5.7% (under AM 1.5 G simulated solar radiation at 1 sun intensity) for tandem cells based on small-molecularweight materials, suggesting that even higher efficiencies are possible.We conclude by considering the ultimate power conversion efficiency that is expected from organic thinfilm solar cells.
Ordered Organic–Inorganic Bulk Heterojunction Photovoltaic Cells
Authors: Coakley Kevin M. , Liu Yuxiang , Goh Chiatzun , McGehee Michael D.
Published: February 2011

Fabrication of bulk heterojunctions with well-ordered arrays of organic and inorganic semiconductors is a promising route to increasing the efficiency of polymer photovoltaic cells. In such structures, almost all excitons formed are close enough to the organic–inorganic interface to be dissociated by electron transfer, all charge carriers have an uninterrupted pathway to the electrodes, and polymer chains are aligned to increase their charge carrier mobility. Furthermore, ordered structures are interesting because they are relatively easy to model. Studies of ordered cells are likely to lead to better design rules for making efficient photovoltaic cells.
SiC Bipolar Power Devices
Authors: Chow T. Paul
Published: February 2011

The successful commercialization of unipolar Schottky rectifiers in the 4H polytype of silicon carbide has resulted in a market demand for SiC high-power switching devices. This article reviews recent progress in the development of high-voltage 4H-SiC bipolar power electronics devices.We also present the outstanding material and processing challenges, reliability concerns, and future trends in device commercialization.
Photoelectrochemical Cells Based on Inherently Conducting Polymers
Authors: Wallace G. G. , Too C. O. , Officer D. L. , Dastoor P. C.
Published: February 2011

This review of photoelectrochemical cells (PECs) based on inherently conducting polymers (ICPs) deals with the mechanisms of operation and the various factors that influence the overall efficiency of PECs. The factors addressed include ICP composition and oxidation state, the use of nanostructured surfaces and interfaces, and the PEC electrolyte and redox mediator.
Surfactant-Directed Synthesis and Optical Properties of One-Dimensional Plasmonic Metallic Nanostructures
Authors: Murphy Catherine J. , Sau Tapan K. , Gole Anand , Orendorff Christopher J.
Published: February 2011

One-dimensional metallic nanostructures such as nanorods and nanowires are of tremendous interest for electronic, sensing, and catalytic applications. Shape anisotropy introduces new optical properties in gold and silver nanoparticles, such as longitudinal plasmon resonance bands in the visible and near-IR portion of the spectrum. Different approaches employed for the shape-controlled synthesis of silver and gold nanocrystals include chemical, electrochemical, and physical methods. The chemical route for the synthesis of nanorods and nanowires, in which metal salts are reduced in an aqueous solution, is one of the most widely used methods. This route commonly employs a surfactant as the directing agent to introduce asymmetry in the nanocrystal shape. Variation in the concentration of precursor salt and the surfactant, the nature of the surfactant, the nature and concentration of reducing agents, the presence of external salts, and the pH of the reaction solution all affect nanocrystal shape, dimension, and yield. The size and shape of the nanocrystals affect the position of the plasmon bands, which in turn has been widely used in surface-enhanced spectroscopies that include both Raman and fluorescence. The aqueous, surfactant-directed route also promises the synthesis of more complex nanostructures with additional desirable properties.
Magnetic Domain Walls in Nanowires
Authors: Allenspach Rolf , Jubert Pierre-Olivier
Published: February 2011

For many decades, it was assumed that the characteristics of magnetic domain walls were determined by material properties and the walls were moved by magnetic fields.In the past few years, it has been shown that domain walls behave differently on the nanometer scale.Domain walls in small elements exhibit complex spin arrangements that strongly deviate from the wall types commonly encountered in magnetic thin-film systems, and they can be modified by changing the geometry of the element.Domain walls in nanowires can also be moved by injecting electrical current pulses.Whereas wall propagation is qualitatively explained by a spin transfer from the conduction electrons to the spins of the domain wall, important aspects of the observations cannot be explained by present models.Examples include the observation of a drastic transformation of the wall structure upon current injection and domain wall velocities that tend to be orders of magnitude smaller than anticipated from theory.
A Perspective on Modeling Materials in Extreme Environments: Oxidation of Ultrahigh-Temperature Ceramics
Authors: Bongiorno Angelo , Först Clemens J. , Kalia Rajiv K. , Li Ju , Marschall Jochen , Nakano Aiichiro , Opeka Mark M. , Talmy Inna G. , Vashishta Priya , Yip Sidney
Published: February 2011

The broader context of this discussion, based on a workshop where materials technologists and computational scientists engaged in a dialogue, is an awareness that modeling and simulation techniques and computational capabilities may have matured sufficiently to provide heretofore unavailable insights into the complex microstructural evolution of materials in extreme environments.As an example, this article examines the study of ultrahigh-temperature oxidation-resistant ceramics, through the combination of atomistic simulation and selected experiments.We describe a strategy to investigate oxygen transport through a multi-oxide scale—the protective layer of ultrahigh-temperature ceramic composites ZrB2-SiC and HfB2-SiC—by combining first-principles and atomistic modeling and simulation with selected experiments.