bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic Ceramic Thin Films: Trends in Research and Development
Authors: Tuttle Bruce A. 
Published: August 2016

Electronic ceramic materials research is one of the fastest growing, most highly publicized areas of materials science. Subjects receiving considerable attention include high temperature superconductors, multilayer ceramic composites for high density microelectronics packaging, and ferroelectric electro-optic thin films. A complete review of all aspects of electronic ceramics research is beyond the scope of this article, which will focus on two general topics whose development is representative of recent contributions to the field. These two areas are synthesis and characterization of electronic ceramic films,1 and controlled use of low level dopants (1,000 ppm or less) in bulk polycrystalline ceramics, thin films, and single crystals to achieve desired properties. Perspective of the progress in ceramic film development is given by a review of single-crystal synthesis and properties.Several examples of the impact that low level dopants and thin film synthesis have on electronic ceramics development are presented. Dopant concentrations of 1,000 ppm or less can have a dramatic effect on microstructural, optical, and electrical properties. For example, a decrease in aluminum content of 150 ppm resulted in an increase in grain size from 1 to 25 microns in otherwise identical ZnO varistors. Background aluminum concentrations for these varistors were less than 10 ppm. In another example, the photorefractive effect, the change in refractive index with optical light intensity, has been shown to be altered by orders of magnitude with ppm doping levels in ferroelectric electro-optic materials.Several electronic ceramic devices have recently been developed due to improvements in ceramic film processing. Examples of these devices include: 1. multilayer PZT transformers, which allow fabrication of complex monolithic passive multicom-ponent networks, 2. liquid cooled multilayer ceramic substrates, with 400×800 micron liquid transfer capillaries integrated into the multilayer structure via ceramic processing techniques for high density VLSI packaging, and 3. ferroelectric electrooptic thin films that are compatible with silicon or III-V technology. For all the above applications, synthesis of electronic ceramic materials into high purity films is essential.
Techniques for Materials Microanalysis
Authors: Helms C.R. 
Published: August 2016

The science and technology of ultrasmall three-dimensional materials systems has been developing rapidly the last 20 years or so. Catalysts, coatings, composites, as well as electronic device structures—all rely on materials properties on an atomic scale. To develop such new materials and understand the chemical and physical properties that determine their unique behavior, we also require analytical tools with atomic level spatial resolution and at the same time the desired measurement capability. This need, along with extensive scientific interest in the fundamental chemical and physical properties of free surfaces, has led to the continued development of microanalytical chemical analysis techniques over the past 20 years. Most readers will be familiar with many of these techniques with acronyms such as AES, XPS, RBS, SIMS, ESCA, etc. This issue of the MRS BULLETIN will review some recent advances in the development of these techniques as well as introduce new techniques with significant advantages over the older ones.As you can see from the thickness of this issue, it is difficult to cover the entire field in a finite amount of space. This led us to limit the discussion to those microanalytical tools which can easily be applied to the analysis of buried interface structures such as those found in semiconductor devices.
Materials Analysis with High Energy Ion Beams Part I: Rutherford Backscattering
Authors: Gossmann H-J. , Feldman L.C. 
Published: August 2016

AbstractThis article discusses the underlying principles of Rutherford backscattering spectrometry (RBS). Consideration of the theory of the interaction of high energy ions with solids leads to the conclusion that quantitative elemental analysis of the near-surface composition of solids can be performed by RBS. Examples are given.
Fundamentals of Sputtered Neutral Mass Spectrometry
Authors: Kaiser U. , Huneke J.C. 
Published: August 2016

AbstractSputtered neutral mass spectrometry (SNMS) is a technique for elemental and isotopic analysis with excellent detection limits, with similar sensitivity for all elements and without substantial matrix effects. Particles sputter atomized from the sample surface are ionized and mass spectrometrically measured. Elemental detection limits are routinely 1–10 ppm, but can be as low as 1–10 ppb. Particular modes of SNMS enable the measurement of accurate concentration depth profiles with resolutions approaching 20 Å and the measurement of electrically insulating samples.
Surface Analysis by Laser Ionization
Authors: Pallix J.B. , Becker C.H. , Newman N. 
Published: August 2016

AbstractAn overview is presented of a recently developed surface analysis method that combines (1) desorption of neutral atoms and molecules from a sample, typically by sputtering, (2) efficient uniform ionization close to but above the surface by an intense ultraviolet laser beam, and (3) time-of-flight mass spectrometry. This technique, surface analysis by laser ionization, or SALI, provides extremely efficient and sensitive quantitative analysis of surfaces and materials with high depth resolution. Essentially any type of material can be analyzed as evidenced by the examples presented here: the Au-GaAs system, a phosphor-silicate glass, and a bulk polymer.
Advances in Small Spot ESCA
Authors: Bryson Charles E. , Chaney Robert E. 
Published: August 2016

AbstractThe changes in Electron Spectroscopy for Chemical Analysis (ESCA) equipment since 1982 have significantly expanded the range of applications and general utility of the technique. Most of these changes center around improvements in spatial resolution although there have also been improvements in speed and energy resolution. The implications of these changes extend beyond the obvious ability to obtain information from small features on samples.The three major approaches to controlling spatial resolution are: (1) defined area x-ray sources, (2) limited field-of-view electron analyzers, and (3) imaging electron analyzers. Each of these will be reviewed briefly and their salient features contrasted. These advances in the instrumentation have brought about the following benefits to users of the ESCA technique: (1) ability to analyze small features, (2) rapid depth profiling, (3) multiple samples, and (4) improved charging control. Examples are included.
Advances In Analytical Auger Electron Spectroscopy
Authors: Chang Chuan C. 
Published: August 2016

AbstractFundamental principles and experimental procedures for fully utilizing the power of Auger analysis are discussed. Topics include: quantitative analysis, high resolution imaging, depth profiling, and noise reduction. These studies reveal several improvements that might be expected in the immediate future and how they might be achieved. Some knowledge of Auger spectroscopy is assumed, but references on theory, principles, instrumentation, and applications are cited.
Silica Glasses
Authors: Griscom David L. 
Published: August 2016

Fifty years ago, who could have imagined that silicon dioxide—the material of ordinary beach sand—would become one of the most important materials of present-day optics and electronics? Yet SiO2is arguably the most crucial material component in current-generation fiber optics and metal-oxide-semiconductor (MOS) device technology. In MOS field-effect transistors (MOSFETs), SiO2serves not only as the gate insulator, but also as the “field oxide” (which isolates various components of an integrated circuit) and as the packaging material which seals the device from outside contamination. In these roles silica acts as a “perfect dielectric,” being characterized by an essentially infinite resistivity (actually ~1016Ohm · m at 300 K). The ability to form such a high quality dielectric film with a near-perfect lattice match on single-crystal silicon continues to favor silicon-based MOS technology over technologies founded on electrically superior GaAs.In the rapidly developing fiber optic arena, fused silica is still “king” due to a combination of properties, including extremely high transparency over a range of usable wavelengths (Figure 1), low material dispersion (~0 at 1.3/üm), high tensile strength (~ 150 kpsi), and high chemical durability. In addition, bulk forms of silica continue to find application in lenses, prisms, windows, and low-coefficient-of-thermal-expansion reflective optics; thin silica films are common components of the highly reflective and anti-reflective surface coatings which are laid down on reflective and transmissive optics, respectively.
Assessment of Directions and Opportunities in Current and Future Materials Education
Authors: Bernstein I.M. 
Published: August 2016

There is considerable excitement and some turmoil in undergraduate and graduate education in the broad field of materials, as well as in its subfields of metallurgy, ceramics, and polymers. While the reasons are many, the underlying driver is the growth in the visibility and diversity of a young field evolving rapidly into a true discipline, much like chemical engineering and biology from their early roots mainly in chemistry.The University Materials Council (UMC), the group representing accredited materials departments has had a longstanding, obvious interest in education and has been actively involved in assessing current and future directions. More recently, a comprehensive study under the auspices of the National Research Council (the Materials Science and Engineering Study), has been undertaken to develop a unified view of recent progress and new directions in materials science and engineering (MSE), and to assess future opportunities and needs. As part of this ambitious endeavor, a panel on education (Panel 5) was established with the following charges:• To investigate and document existing human resources in MSE;• To identify future directions of education in MSE, including education in and out of materials departments;• To identify needs and opportunities for increasing interdisciplinarity in MSE; and• To identify needs and opportunities in lifelong education.
Specific Materials Science and Engineering Education
Authors: Readey D.W. 
Published: August 2016

Forty years ago there were essentially no academic departments with titles of “Materials Science” or “Materials Engineering.” There were, of course, many materials departments. They were called “Metallurgy,” “Metallurgical Engineering,” “Mining and Metallurgy,” and other permutations and combinations. There were also a small number of “Ceramic” or “Ceramic Engineering” departments. Essentially none included “polymers.” Over the years titles have evolved via a route that frequently followed “Mining and Metallurgy,” to “Metallurgical Engineering,” to “Materials Science and Metallurgical Engineering,” and finally to “Materials Science and Engineering.” The evolution was driven by recognition of the commonality of material structure-property correlations and the concomitant broadening of faculty interests to include other materials. However, the issue is not department titles but whether a single degree option in materials science and engineering best serves the needs of students.Few proponents of materials science and engineering dispute the necessity for understanding the relationships between processing (including synthesis), structure, and properties (including performance) of materials. However, can a single BS degree in materials science and engineering provide the background in these relationships for all materials and satisfy the entire market now served by several different materials degrees?The issue is not whether “Materials Science and Engineering” departments or some other academic grouping of individuals with common interests should or should not exist.
Metallic Superlattices: The Study of Materials at Length Scales From a Few to Hundreds of Angstroms
Authors: Schuller Ivan K. , Homma H. 
Published: August 2016

AbstractWe present the possibilities that metallic superlattices offer for the study of materials at length scales ranging from a few to hundreds of angstroms. The materials problems being studied span practically all interesting solid-state phenomena, including superconductivity, magnetism, elastic behavior, development of novel materials, diffusion, ion beam mixing, crystallization, and amorphization. Several applications are also being pursued. We present a few examples of problems that can be studied at different length scales. Emphasis is made that for a proper study of materials properties, extensive structural characterization is imperative.
Ion Beam Processing
Authors: White C.W. 
Published: August 2016

Ion beams are used extensively in materials research for processing and synthesis as well as for characterization. In the last few years, enormous advances have been made regarding the use of ion beams for processing or synthesis, and this issue of the MRS BULLETIN will review some of those advances. (The use of ion beams for materials characterization will be the subject of a future issue of the BULLETIN.) The areas covered in this issue are ion implantation, ion beam mixing, ion-assisted deposition, and direct ion beam deposition. For each area, recognized experts in the field prepared overview articles that should be very interesting to those who are not active in the field, and that should be useful to other experts in the field.The first large-scale use of ion beams for materials modification took place in the semiconductor industry more than 20 years ago when ion implantation began to be used to dope the near-surface region of silicon with Group III or Group V dopants. The use of ion implantation in the semiconductor industry has undergone explosive growth, and today almost all electronic devices are fabricated utilizing at lest one ion implantation step.In addition to the semiconductor area, research is being carried out using ion implantation in a multitude of other areas which include ceramics, metals and alloys, insulators, etc. The article on “Ion Implantation” by S.T. Picraux and P.S. Peercy provides an excellent overview of current research activities involving ion implantation of a wide spectrum of materials.
Up Close: The Advanced Materials Institute
Authors: Morse Jerome G. 
Published: August 2016

The Advanced Materials Institute (AMI) is the materials research arm of the Colorado Advanced Technology Institute (CATI), a state agency created in 1983 by the state General Assembly as an economic development initiative involving academic, industry, and government sectors. AMI represents a unique process in academic research: long-term materials needs of industry members are addressed by university investigators, with federal agencies providing the major source of funding.AMI is a consortium of four research universities (Colorado School of Mines as the lead institution, Colorado State University, and the Universities of Colorado and Denver) and a present industrial membership of nine corporations (AMAX Inc., Adolph Coors Company, Digital Equipment Corporation, Gates Company, Hewlett Packard, IBM, Manville, Martin Marietta, and Telectronics). The Institute is governed by a Board of Directors with representatives from each participating organization. Sustaining memberships, which do not include representation on the Board, are available; memberships of both kinds are open to non-Colorado-based companies.The long-term materials needs of industry members provide AMI's research agenda; many items, once identified, become company-shared interests. Requests for proposals, based on the agenda, are distributed to the affiliated universities for competitive awarding of seed funds. Proposals receive peer review and the Board selects those to be funded.
New Opportunities in Materials Research With Pulsed Neutrons
Authors: Lander G. H. 
Published: August 2016

AbstractNeutrons have played an important role in materials research for the last 30 years. Recently a new method of producing neutrons, with proton accelerators and specifically designed targets and moderators, has been developed. Many of the techniques developed with these powerful spallation sources open new opportunities for materials research, some of which will be covered in this article. An effort will be made to explain the types of science that can be done, rather than details of the techniques. Spallation sources are being operated as user facilities so the inexperienced can count on expert assistance.
Selective Area Growth of GaN Directly on (0001) Sapphire by the HVPE Technique
Authors: Singh Raj , Barrett Richard J. , Gomes John J. , Dabkowski Ferdynand P. , Moustakas T.D. 
Published: August 2016

In this paper, we report on the selective area growth (SAG) of GaN directly on patterned c-plane sapphire substrates by hydride vapor phase epitaxy (HVPE). A number of researchers have reported that the HVPE growth technique, unlike the MBE and MOCVD methods, is capable of producing device quality GaN films without the need for any low temperature nucleation/buffer layers. The density of edge dislocations in these HVPE films decreases dramatically as the film thickness is increased, and the dislocation density values for thick films (> 10μm) are comparable to those reported for the best GaN films grown by other methods on c-sapphire. These advantages of the HVPE growth technique makes it possible to achieve high quality selective area growth of GaN directly on c-sapphire substrates.C-plane sapphire substrates were coated with PECVD SiO2 and photolithographically patterned with different size and shape openings. Subsequently, these patterned substrates were introduced in a horizontal, hot-wall quartz reactor for the GaN growth. It was observed that single crystal GaN growth was preferentially initiated in the openings in the oxide layer. This selective area growth was followed by epitaxial lateral overgrowth (ELO), leading to the formation of hexagonal GaN prisms terminated in smooth, vertical (100) facets. We have been successful in shearing these pyramid structures from the sapphire substrates as individual devices, which do not require any post-growth etching for feature definition. This procedure allows for the dramatic reduction of the process complexity and the duration and expense for GaN growth for device applications. Stimulated emission results on these self-formed optical cavities are also presented.
Optical nonlinearities of Gallium Nitride
Authors: Haag H. , Gilliot P. , Ohlmann D. , Levy R. , Briot Olivier , Aulombard Roger-Louis 
Published: August 2016

Luminescence, induced absorption and degenerate four-wave mixing experiments are perform on GaN epilayers grown on a sapphire substrate by MOCVD.We measure the nonlinear behavior of the luminescence spectra near the excitonic resonance, by using an excitation at 4.026 eV from an excimer laser. At low intensities of excitation, spectra show a saturation of the I2 line due to the finite donor density in the sample. Higher intensities of excitation induce collision processes between photo-created quasi-particles.Using a dye laser as a pump beam, we measure the induced variation of absorption of a probe beam as a function of the intensity and of the wavelength of the excitation. With increasing intensities of the pump beam, transmission spectra show a red-shift of the absorption edge and of the excitonic resonance.Pulsed degenerate four-wave mixing experiments were performed using the third harmonic of a picosecond Nd-YAG laser at 3.492 eV. A characteristic time constant of 16 ps has been measured, which is independent of the temperature, spacing of the interference fringe and of the intensity of the pump beams.
MOVPE Growth and Structural Characterization of AlxGa1−xN
Authors: Ruffenach-Clur S. , Briot Olivier , Gil Bernard , Aulombard Roger-Louis , Rouviere J. L. 
Published: August 2016

The ternary alloy GaAlN has been grown by low pressure MOVPE (76 Torr) using triethylgallium, trimetylaluminum and ammonia as precursors. The alloy layers were grown on (0001) sapphire substrates using a low temperature AlN buffer. All layers were deposited at a growth temperature of 980°C. Only the aluminum/gallium ratio in the gas phase was changed, keeping the total group III molar flow rate and V/III molar ratio constant.The aluminum incorporation versus gas phase composition was determined experimentally, using energy dispersive analysis of X-rays (EDAX), and X-ray diffraction. We propose a model, taking into account kinetically limited mass transport of group III species in the gas phase, which describes well the data.The structural quality of the layers was investigated using X-ray diffraction and TEM experiments.A degradation of the materials quality is observed with increasing Al content. In this case, growth originate on the buffer grains facets resulting in a “ two directional » growth. This phenomenon, being markedly enhanced when increasing the Al content will be detailed in this paper.
Epitaxial Growth and Orientation of GaN on (1 0 0) γ-LiAlO2
Authors: Hellman E. S. , Liliental-Weber Z. , Buchanan D. N. E. 
Published: August 2016

The (1 0 0) face of γ-LiAlO2 has attracted attention as a possible substrate for GaN epitaxial growth. This is partly because this face has an excellent lattice and structural match to (1 0 0) GaN. This orientation would have a misfit of only −1.4% along the c-direction and −0.1% along the b-direction of LiAlO2. We find that in practice this orientation relationship does not occur; instead, (0 0 0 1) oriented GaN grows with a small tilt (0.6° towards the c-direction) between the film and substrate. Although the misfit along the substrate b direction is large (−6.3%) for this orientation, the tilt perfectly accommodates the −1.4% misfit in the c direction. We present characterization of these films by RHEED, X-ray diffraction, and TEM. We propose that the tilt is driven by a reduction of interface energy which occurs in polar, incoherent interfaces.
Theoretical Studies Of Hydrogen Passivated Substitutional Magnesium Acceptor In Wurzite GaN
Authors: Torres V. J. B. , Öberg S. , Jones R. 
Published: August 2016

Infrared measurements on wurzite GaN codoped with Mg and H reveal strong absorption at 3125 cm−1. Theorectical work provides strong evidence for the H being antibonding to N. We have performed an ab-initio study of Mg-H complexes in wurzite GaN, using the Local Density Approximation on a large H-terminated cluster MgHGa25N26H42. We have investigated the physical properties of three neutral configurations along the c direction. In all configurations Mg sits in a gallium substitutional site. H is then located in the Mg-N bond centre (BC), in the antibonding site on nitrogen side (ABN) or in the antibonding position on magnesium side (ABMg). We found the lowest total energy configuration is hydrogen in the antibonding on the nitrogen site. The stretch mode in this configuration is calculated at 3277 cm−1 which agrees with experiment and previous LDA calculations and we predict an unreported infra red active wag mode at 1311 cm−1. The experimental isotopic shift with D is well reproduced. The BC and ABMg configurations are 0.5 and 3.7 eV higher, producing local modes at 3645 and 2144 cm−1, respectively. No wag modes appear for the BC and ABMg configurations.