bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth, Spectroscopy, and Laser Application of Self-Ordered III-V Quantum Dots
Authors: Bimberg D. , Grundmann M. , Ledentsov N.N. 
Published: August 2016

The development and application of semiconductor light-emitting and laser diodes has been a huge success during the last 30 years in key areas of modern technology like communications, recording, and printing. Still there is ample room for improvement through combination of the atomlike properties for zero-dimensionally localized carriers in quantum dots (QDs) with state-of-the-art semiconductor-laser technology. Low, temperature-insensitive threshold current; high gain; and differential gain have been predicted since the early 1980s.In the past two decades, the fabrication of QDs has been attempted using colloidal techniques (see the article by Nozik and Mićić in this issue), patterning, etching, and layer fluctuations (see the article by Gammon in this issue). However a break-through occurred recently through the employment of self-ordering mechanisms during epitaxy of lattice-mismatched materials (see the next section) for the creation of high-density arrays of QDs that exhibit excellent optical properties, particularly high quantum efficiency, up to room temperature. The zero-dimensional carrier confinement and subsequent atomlike electronic properties have a drastic impact on optical properties (see the section on Spectroscopy). Also intimately connected is the applicability of QDs as a novel gain medium in state-of-the-art laser diodes with superior properties (see the section on Lasers).
Applications of Electron Microscopy in Collaborative Industrial Research
Authors: Ross F.M. , Krishnan K.M. , Thangaraj N. , Farrow R.F.C. , Marks R.F. , Cebollada A. , Parkin S.S.P. , Toney M.F. , Huffman M. , De Araujo C.A. Paz , McMillan L.D. , Cuchiaro J. , Scott M.C. , Echer C. , Ponce F. , O'Keefe M.A. , Nelson E.C. 
Published: August 2016

The transmission electron microscope (TEM) is one of the most useful tools available to the materials scientist. Yet both the complexity and expense of the equipment, and the huge investment in time necessary to become proficient in specimen preparation and image acquisition and analysis, mean that it is difficult for most industrial institutions to maintain a state-of-the-art TEM facility. How can industry overcome this problem? One solution is to set up a collaboration with a university, an industrial partner, or a government research laboratory. Such collaborations can be extremely valuable to the company, which gains access to microscopes, specimen-preparation equipment and the expertise of professional microscopists, and to the research laboratory, which benefits from the industrial perspective and the private sector's proficiency in materials preparation and processing.Such collaborations exist, and they can produce excellent results. In this article, we present three case studies in which successful collaboration has occurred between industry and one of the Department of Energy's scientific user facilities, the National Center for Electron Microscopy (NCEM-see sidebar). Our aim is not only to describe results that we hope will be of scientific interest but also to encourage industrial researchers to consider collaborations with institutes such as NCEM.
Materials Used in Electroluminescent Displays
Authors: Rack P.D. , Naman A. , Holloway P.H. , Sun S-S. , Tuenge R.T. 
Published: August 2016

The flat-panel-display (FPD) market is experiencing rapid growth due to increased demand for portable computers, communication equipment, and consumer electronic products. In all of these applications, the display is the primary human interface that conveys information. The size of the flat-panel-display market is presently estimated to be $10 billion/year and is projected to grow to over $18 billion/year by 1998. Although most current FPDs utilize either passive- or active-matrix liquid-crystal-display (LCD) technology, electroluminescent (EL) displays and light sources, because of their solid-state construction and self-emissive characteristics, can provide improved performance for many demanding display applications. Thin-film electroluminescent (TFEL) technology has been demonstrated over a broad range of display sizes from 1-in. to 18-in. diagonal with resolutions from 50 to 1,000 lines per inch. Also, because of its unique solid-state characteristic, TFEL technology is well-suited to provide a fully integrated display with the light-emitting element and electronics fabricated on the same substrate. An example of a full-color TFEL display is shown in Figure 1.Thin-film electroluminescent display panels are finding increasing applications in the FPD marketplace due to several fundamental performance advantages over LCDs. These include wide viewing angle, high contrast, wide operating-temperature range, ruggedness, and long lifetime. Alternating-current (ac)-driven monochrome TFEL displays (ACTFEL displays) have become the most reliable, longest running devices on the market. Commercial ACTFEL display panels have operated for more than 50,000 hours with less than 10% luminance change, the equivalent of 25 working years.
Surface Absorption of Monolayers
Authors: Ulman Abraham 
Published: August 2016

When the first paper describing the formation of self-assembled monolayers (SAMs) of octadecyltrichlorosilane [CH3(CH2)17SCl3, or OTS] by adsorption on SiO2 was published, it could not have been predicted that this area of research would become so important in only one decade. Although Zisman was the first to discover that monolayers can be prepared by adsorption of a surfactant onto a clean metal surface, the real revolution in the field occurred when Nuzzo and Allara showed that SAMs of alkanethiolates on gold can be prepared by adsorption of di-n-alkyl disulfides from dilute solutions. A decrease in the use of moisture-sensitive alkyl trichlorosilanes and the increased use of crystalline gold surfaces were two important reasons for the success of these SAMs. Indeed, monolayers of alkanethiolates on gold are the most studied SAMs to date and thus deserve the most detailed discussion.SAMs have been intensively studied in the past few years because of their relevance to science and technology. Due to their dense and stable structure, SAMs have potential applications in corrosion prevention, wear protection, and biosensing, for example. The ability to tailor both head and tail groups of the constituent molecules makes them ideal for gaining a more fundamental understanding of phenomena affected by competing intermolecular, molecular-substrate, and molecule-solvent interactions like ordering and growth, wetting adhesion, lubrication, and corrosion.
Beneficial Aspects of the Environmental Instability of Materials
Authors: Ambrose John R. , Bendale Priya R. 
Published: August 2016

The environmental degradation of materials poses a serious limitation in the utility of engineering materials. The corrosion of metals, for example, has been estimated to represent a 4–5% decrease in the Gross National Product each year. To this, add losses involved in the replacement or restoration of ceramic structures such as buildings and transportation systems, i.e., the “infrastructure,” and the result is a significant sacrifice of economic strength.Most of us are familiar with the consequences of exposing materials to environments in which the materials are chemically unstable and convert into substances that are unable to perform the function for which the original material was selected. The corrosion of metals into soluble or insoluble oxidation reaction products, chain scission or molecular mutation in polymers, even hydrolysis and leaching of silicious ceramic compounds represent behavior which ultimately limits the service applications of most engineering materials. For example, aluminum and its alloys are unsuitable for use in environments where oxide formation rates are high enough to represent a problem with respect to useful service life.
Mathematical Modeling in Materials Science and Engineering
Authors: Szekely Julian 
Published: August 2016

During the past two decades, mathematical modeling has been gaining acceptance as a legitimate part of materials science and engineering. However, as common to all relatively new disciplines, we still lack a realistic perspective regarding the uses, limitations, and even the optimal methodologies of mathematical modeling techniques.The term “mathematical modeling” covers a broad range of activities, including molecular dynamics, other atomistic scale systems, continuum fluid and solid mechanics, deformation processing, systems analysis, input-output models, and lifecycle analyses. The common point is that we use algebraic expressions or differential equations to represent physical systems to varying degrees of approximation and then manipulate these equations, using computers, to obtain graphical output.While it is becoming an accepted fact that some kind of mathematical modeling will be needed to make most research programs complete, there is still considerable ambiguity as to what form this should take and what might be the actual usefulness of such an effort.Among the more seasoned and successful practitioners of this art, clear guidelines have emerged regarding the uses and limitations of the mathematical modeling approach. We seek to illustrate these uses through the successful modeling examples presented by some leading practitioners. Some general principles may be worth repeating as an introduction to this interesting collection of articles.
Emulsion-Derived Foams Preparation, Properties, and Application
Authors: Even William R. , Gregory Donald P. 
Published: August 2016

Porous polymeric foams are well-known materials and have been produced by a wide variety of techniques ranging from leaching soluble fillers through gas-blowing to phase separation. Although these materials are widely used, their structure is often irregular and difficult to control. However, a novel method for producing porous materials with a more regular structure has been developed based on high internal phase emulsions (HIPE). These foams are called emulsion-derived foams and are commercially known as Polyhipe® (Unilever) polymers.If one takes a liquid oil, introduces water and a suitable emulsifier with agitation, a dilute emulsion is produced with small water droplets dispersed within the oil phase, about the consistency of milk. If the amount of the water (i.e., the internal or pore forming) phase is increased, a concentrated emulsion will be formed and the consistency of the mixture changes into a more viscous fluid. As further water is introduced, a limit is reached where the droplets are so prevalent that they approximate a close-packed structure (see cover of this issue); beyond this point the droplets must distort to accommodate any additional internal phase. For a collection of monodispersed spheres this packing limit corresponds to 74% by volume and is the accepted definition of a high internal phase emulsion, i.e., an emulsion with an internal phase greater than 74%.4 The structure of the emulsion is now analogous to soap bubbles, with thin films surrounding and separating the drops. Note also that, compared to “standard” emulsion polymerization, this is the exact reverse or “inverse” of that process. In the standard route, the dispersed oil phase is polymerized to yield a collection of polymeric spheres; with inverse emulsion, the continuous phase is polymerized, yielding a rigid matrix.
Industrial Ecology: The Materials Scientist in an Environmentally Constrained World
Authors: Allenby Braden R. 
Published: August 2016

For most materials scientists, as for most people, John Donne's lines “and therefore never send to know for whom the bell tolls. It tolls for thee.” are simply inspired verse. Increasing recognition of the interplay between human economic activity and global environmental perturbations, however, are beginning to add a cold air of prescience to John's words: “Ask not for whom the CFCs are emitted. They are emitted for thee.”The need for greater understanding, and new, more systematic approaches to these intertwined economic/environmental issues is becoming more apparent. What is perhaps not so clear is the critical role that materials scientists and engineers must play in this effort. An analysis of the symbiotic relationships among economic development, human population growth, and the uses and flows of materials throughout the economy clearly demonstrates this role.The intuitive feeling held by many technologists—that they are part of the solution, not part of the problem—certainly appears to be correct. But it will require growth on our part, and a more systems-oriented and comprehensive view of our role, if this promise is to be fulfilled.
Control of Directional Properties in Aluminum Can Stock
Authors: Pate Mark A. 
Published: August 2016

Aluminum alloy 3004 (Al-1.0 Mn-1.0 Mg) is the predominant material of choice for use in rigid beverage containers. The mechanical property requirements of the draw and iron forming operation dictate careful control of the aluminum sheet production parameters. The demand for ever lighter weight beverage containers has also continued to place increased demands on the strength requirements of the aluminum can stock. To achieve the strength requirements, the sheet must be produced in a highly cold-worked state. A practical consequence of this required level of cold work is pronounced mechanical and crystallographic anisotropy. Without careful control of can stock production parameters, pronounced rolling textures can lead to an undesirable directionality of properties that produce ears, formed during the deep drawing operation of can making, located 45° to the rolling direction. Figure 1 shows the rolling texture ears in a drawn and ironed beverage can.This article illustrates the minimization and control of rolling texture earing in cold rolled 3004 alloy beverage can stock through modification of the fabricating process, application of metallurgical theory, optimization of hot rolling practice through empirical experimentation, and process control practices.
The National Critical Materials Act
Authors: Leamy Harry 
Published: August 2016

Profound acknowledgment of the importance of materials research to the well-being of society has recently been provided by the government of the United States of America in the form of Public Law 98-373: National Critical Materials Act of 1984. This law provides for the establishment of a National Critical Materials Council within the Executive Office of the President that is responsible for coordination of the government's materials-related policies, programs, and research and technology activities. This new legislation, the major features of which are reproduced on the next page in this issue of the BULLETIN, promises to touch all of us in some way during the coming years.The law establishes a National Critical Materials Council consisting of three presidential appointees who are qualified in materials policy or materials science and engineering. The Council is primarily responsible for the formulation of national materials policies consistent with other Federal policies. This activity includes establishing responsibilities for programs and priorities for materials activities in each Federal department or agency. The Council will also review materials programs and activities of the government for consistency with the National Materials and Minerals Policy Research and Development Act of 1980. It will monitor the critical needs of both industry and government, and it will advise the President of world trends and their implications for national and world economy and national security.
Fundamental Properties of Intermetallic Compounds
Authors: Nakamura Morihiko 
Published: August 2016

More than 25 years have passed since Intermetallic Compounds, edited by Westbrook, was published. Since that time, enormous advances have been made in the understanding and usage of intermetallic compounds. It is known that intermetallic compounds are generally brittle. Thus, alloys that contain intermetallics may also be brittle. However, many intermetallic compounds are known to have extraordinary functions and characteristics that are not observed in ordinary metals and alloys. Thus, they function as magnetic materials, superconductors, semiconductors, hydrogen absorbing alloys, shape memory alloys, and so on.Many high-strength structural alloys like maraging steels and duralumins are strengthened by fine precipitates of intermetallic phases. Nickel-based superalloys, which are used for airplane-engine parts, contain 60-70% of Ni3Al-based intermetallics by volume fraction and exhibit high strength at high temperatures. Hard metals, which are used for cutting tools, are composed of a large amount of hard but brittle intermetallics like WC and a small amount of ductile cobalt. Intermetallic compounds like TiAl are also investigated for their applications as structural materials where high strength at high temperatures is required.In a strict sense, intermetallic compounds are composed of two or more metallic elements. In a wider sense, they are composed of metallic and/or semimetallic elements. Each is characterized by an ordered arrangement of two or more kinds of atoms, that is, the formation of a superlattice, and have various kinds of interatomic bonding, ranging from metallic to covalent or ionic bonding. The ordering of atoms and the strong interatomic bonding result in many attractive properties for intermetallic compounds.
Simulation of Microstructure and Surface Profiles of Thin Films for VLSI Metallization
Authors: Smy T. , Dew S.K. , Brett M.J. 
Published: August 2016

A crucial step in the manufacture of very large-scale integration (VLSI) integrated circuits is the fabrication of reliable, low-resistance metal interconnects between semiconductor devices. The fabrication of these interconnects is generally performed by depositing a blanket metal film and then patterning it by lithographic and etching techniques. The primary means of depositing thin metal films for VLSI interconnects are sputtering and chemical vapor deposition (CVD).The creation of reliable interconnects is, however, complicated by a number of issues. In order to obtain low contact resistance, to inhibit reactions with the silicon, and to provide good adhesion to both Si and SiO2, contact, barrier, and adhesion layers are generally deposited prior to the deposition of the low-resistance metal film that forms the bulk of the interconnect. If these layers are to provide an effective barrier to diffusion of the interconnection metal to the silicon, they must be deposited in a uniform, homogeneous form. It is also necessary that the primary interconnect material have as high step coverage as is possible in order to reduce current crowding, local heating effects, and electromigration. Unfortunately, as VLSI circuit densities have increased, the fabrication of interconnects requires high aspect-ratio contact cuts, and relatively severe local topographies can result. These factors make it difficult to deposit films with good step and bottom coverage.In addition to these concerns with the film surface profile, another factor is becoming increasingly significant. Both sputtering and CVD produce thin films with characteristic microstructures. This microstructure consists of columns or grains separated by grain boundaries and voids.
Quantitative Auger and XPS Analysis of Thin Films
Authors: Slaughter J.M. , Weber W. , Güntherodt Gernot , Falco Charles M. 
Published: August 2016

In 1925, P. Auger first observed the so-called Auger electrons in a Wilson cloud chamber. He explained this occurrence as being due to a radiationless transition in atoms excited by a primary x-ray photon source. In 1953, Lander first pointed out that Auger electrons arising from solid samples can be detected in the energy distribution curve of secondary electrons from surfaces subjected to electron bombardment. Moreover, low-energy Auger electrons (∼1 keV kinetic energy) can escape from only the first several atomic layers of a surface since they are strongly absorbed by even a monolayer of atoms. Thus Auger electron spectroscopy (AES) possesses high surface sensitivity. This is one characteristic that makes AES very useful for the study of thin films. For such applications, an important development in AES occurred when Harris showed that the sensitivity of the detection of Auger electrons can be improved by differentiating the electron energy distribution curve with respect to the energy. Furthermore, Weber and Johnson demonstrated that, provided the Auger line profile does not change, the peak-to-peak height in the differentiated energy distribution curves is proportional to the Auger current in the peak. Therefore, in addition to its surface sensitivity, AES also can be used for quantitative studies of thin films.Like AES, x-ray photoelectron spectroscopy (XPS) is a surface-sensitive technique that uses the energy distribution of electrons ejected from a thin film for quantitative analysis. However, in many ways the information provided by AES and XPS is complementary.
Block-by-Block Deposition of Complex Oxide Films
Authors: Locquet Jean-Pierre , Mächler Erich 
Published: August 2016

Since the discovery of superconductivity in layered cuprates there has been a strong desire to grow thin films of these materials in a so-called layer-by-layer manner, where each layer represents one atomic monolayer. There has been worldwide interest in this problem and numerous groups have invested time and equipment in an attempt, first, to grow the known materials using a sequential deposition technique so that the atomic monolayers are stacked artificially on top of one another in a sequence defined by the structure of the given unit cell, and second, to search for new stacking sequences of such atomic monolayers, thus making metastable compounds.Understanding the growth of thin films using any deposition technique requires information about two fundamental processes, the nucleation of a crystal and its growth. Both are strongly affected by the three thermodynamic parameters, temperature, pressure, and chemical potential (composition), at the growth front. The third parameter, the surface composition from which the desired compound can nucleate and propagate, probably provides the greatest degree of freedom in the growth process. The compositional phase diagrams of most cuprates show that several phases can coexist with the superconducting phase at a certain temperature and pressure. This is also the main reason why a widely changing surface composition, such as that present during layer-by-layer or block-by-block deposition, still produces high-quality thin films.