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- Volume 28, 1998
Annual Review of Materials Research - Volume 28, 1998
Volume 28, 1998
- Preface
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- Review Articles
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JAHN-TELLER PHENOMENA IN SOLIDS
Vol. 28 (1998), pp. 1–27More Less▪ AbstractJahn-Teller phenomena encountered in oxides are reviewed briefly. High-spin Mn(III) in an octahedral site illustrates an ion with twofold orbitally degenerate σ-bonding orbitals having a quenched orbital angular momentum; octahedral V(III) and high-spin Co(II), as well as tetrahedral high-spin Ni(II), are examples of ions with threefold orbitally degenerate π-bonding orbitals that retain orbital angular momentum. Cooperative local deformations that are static give rise, below a transition temperature Tt, to a lowering of the lattice symmetry, anisotropic interactions, and the possibility of a ferromagnetism that is oriented in opposition to a magnetic field applied on cooling through the transition. Dynamic local deformations can influence the physical properties of a solid in a variety of ways. Of special interest is the influence of dynamic deformations at a cross-over from localized to itinerant electronic behavior in a mixed-valent system.
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ISOTROPIC NEGATIVE THERMAL EXPANSION
Vol. 28 (1998), pp. 29–43More Less▪ AbstractMaterials that contract on heating are unusual and have important applications. Materials showing such negative thermal expansion behavior are usually anisotropic and usually exhibit this behavior over only a small temperature range. The zirconium tungstate family is unique in showing strong negative thermal expansion over a broad temperature range.
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SPIN-DEPENDENT TRANSPORT AND LOW-FIELD MAGNETORESISTANCE IN DOPED MANGANITES
Vol. 28 (1998), pp. 45–78More Less▪ AbstractDoped manganite perovskites exhibit large magnetoresistance, but usually only in high fields (>1 Tesla). Efforts are under way to understand the underlying mechanism and to explore possibilities of achieving large magnetoresistance at low fields, which has led to focused studies of spin-dependent transport across macroscopic interfaces between manganites. We review recent experimental progress in this area.
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HIGH-DIELECTRIC CONSTANT THIN FILMS FOR DYNAMIC RANDOM ACCESS MEMORIES (DRAM)
Vol. 28 (1998), pp. 79–100More Less▪ AbstractWe discuss high-dielectric films, in general, oxide ferroelectrics based on simple perovskite structures and related Aurivillius-phase layered structure perovskites employed as thin-film capacitors in dynamic random access memories (DRAMs). Emphasis is on breakdown mechanisms and limits, leakage currents, electrodes and electrode interfaces, scaling to submicron geometries, and deposition techniques.
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IMAGING AND CONTROL OF DOMAIN STRUCTURES IN FERROELECTRIC THIN FILMS VIA SCANNING FORCE MICROSCOPY1
Vol. 28 (1998), pp. 101–123More Less▪ AbstractScanning force microscopy (SFM) is becoming a powerful technique with great potential both for imaging and for control of domain structures in ferroelectric materials at the nanometer scale. Application of SFM to visualization of domain structures in ferroelectric thin films is described. Imaging methods of ferroelectric domains are based on the detection of surface charges in the noncontact mode of SFM and on the measurement of the piezoelectric response of a ferroelectric film to an external field applied by the tip in the SFM contact mode. This latter mode can be used for nondestructive evaluation of local ferroelectric and piezoelectric properties and for manipulation of domains of less than 50 nm in diameter. The effect of the film thickness and crystallinity on the imaging resolution is discussed. Scanning force microscopy is shown to be a technique well suited for nanoscale investigation of switching processes and electrical degradation effects in ferroelectric thin films.
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InGaN-BASED LASER DIODES
Vol. 28 (1998), pp. 125–152More Less▪ AbstractContinuous-wave operation of InGaN multi-quantum-well (MQW) structure laser diodes (LDs) has been demonstrated at room temperature with output power up to 50 mW, operating temperature up to 100°C, emission wavelength of 400–420 nm, and a lifetime up to 300 h. InGaN MQW LDs with a lifetime of more than 1000 h are expected soon. Commercialization will begin in 1998 if research on the bluish-purple InGaN-based laser diodes continues to progress. The stimulated emission of the InGaN-based LDs originates from localized energy states of 100–250 meV depth, which are equivalent to quantum dot energy states, probably arising from from InGaN composition fluctuation in the InGaN well layers.
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SOFT LITHOGRAPHY
Vol. 28 (1998), pp. 153–184More LessAbstractSoft lithography represents a non-photolithographic strategy based on self-assembly and replica molding for carrying out micro- and nanofabrication. It provides a convenient, effective, and low-cost method for the formation and manufacturing of micro- and nanostructures. In soft lithography, an elastomeric stamp with patterned relief structures on its surface is used to generate patterns and structures with feature sizes ranging from 30 nm to 100 μm. Five techniques have been demonstrated: microcontact printing (μCP), replica molding (REM), microtransfer molding (μTM), micromolding in capillaries (MIMIC), and solvent-assisted micromolding (SAMIM). In this chapter we discuss the procedures for these techniques and their applications in micro- and nanofabrication, surface chemistry, materials science, optics, MEMS, and microelectronics.
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TRANSIENT DIFFUSION OF BERYLLIUM AND SILICON IN GALLIUM ARSENIDE
Vol. 28 (1998), pp. 185–214More Less▪ AbstractTransient diffusion is an increasingly important phenomenon as thermal budgets for real processes decrease and diffusion during sample growth becomes more important. To fully characterize dopant diffusion in gallium arsenide, an understanding must be developed of the dominant atomistic processes for a given dopant, as well as the sources of transient effects under a given set of experimental conditions. Theoretical, experimental, and simulation results were obtained to understand transient diffusivities of beryllium and silicon in grown-in and implanted samples. In implanted samples, by understanding implant damage and modeling the evolution of point defect populations, the observed transient effects can be explained. Such phenomena cannot account for the time-dependent diffusivity observed when the dopant is introduced during molecular beam epitaxial growth. Transient diffusivities for grown-in beryllium were investigated and explained by modeling the evolution of point defect populations as they increase beyond their equilibrium levels at the growth temperature to achieve equilibrium at the anneal temperature.
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SEMICONDUCTOR WAFER BONDING
U. Gösele, and Q.-Y. TongVol. 28 (1998), pp. 215–241More Less▪ AbstractWhen mirror-polished, flat, and clean wafers of almost any material are brought into contact at room temperature, they are locally attracted to each other by van der Waals forces and adhere or bond. This phenomenon is referred to as wafer bonding. The most prominent applications of wafer bonding are silicon-on-insulator (SOI) devices, silicon-based sensors and actuators, as well as optical devices. The basics of wafer-bonding technology are described, including microcleanroom approaches, prevention of interface bubbles, bonding of III-V compounds, low-temperature bonding, ultra-high vacuum bonding, thinning methods such as smart-cut procedures, and twist wafer bonding for compliant substrates. Wafer bonding allows a new degree of freedom in design and fabrication of material combinations that previously would have been excluded because these material combinations cannot be realized by the conventional approach of epitaxial growth.
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CATHODIC ARC DEPOSITION OF FILMS
Vol. 28 (1998), pp. 243–269More Less▪ AbstractCathodic arc deposition is a plasma-based technology for the fabrication of films. The process can be carried out either at high vacuum or in a low pressure gaseous environment, and films can be formed for example of metals, ceramics, diamond-like carbon, some semiconductors and superconductors, and more. The plasma stream can be filtered to remove microdroplet contamination, and the ion energy can be controlled by substrate bias, thereby transforming the straightforward deposition method into hybrids with other surface modification processes such as ion beam–assisted deposition, ion beam mixing, and ion implantation. The method provides a versatile and powerful plasma tool for the synthesis of novel and technically important surfaces.
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THE MATERIAL BONE: Structure-Mechanical Function Relations
S. Weiner, and H. D. WagnerVol. 28 (1998), pp. 271–298More Less▪ AbstractThe term bone refers to a family of materials, all of which are built up of mineralized collagen fibrils. They have highly complex structures, described in terms of up to 7 hierarchical levels of organization. These materials have evolved to fulfill a variety of mechanical functions, for which the structures are presumably fine-tuned. Matching structure to function is a challenge. Here we review the structure-mechanical relations at each of the hierarchical levels of organization, highlighting wherever possible both underlying strategies and gaps in our knowledge. The insights gained from the study of these fascinating materials are not only important biologically, but may well provide novel ideas that can be applied to the design of synthetic materials.
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SCIENCE AND TECHNOLOGY OF HIGH-TEMPERATURE SUPERCONDUCTING FILMS1
Vol. 28 (1998), pp. 299–347More Less▪ AbstractThe field of high-temperature superconducting thin films is reviewed, focusing on the synthesis and properties of materials that are most promising for device applications. Current materials issues that are important for emerging device applications of oxide superconducting films are discussed, with emphasis on the growth, characterization, and use of epitaxial films. The status of specific superconducting device technologies is briefly reviewed.
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IN SITU STUDIES OF THE PROPERTIES OF MATERIALS UNDER HIGH-PRESSURE AND TEMPERATURE CONDITIONS USING MULTI-ANVIL APPARATUS AND SYNCHROTRON X-RAYS
Vol. 28 (1998), pp. 349–374More Less▪ AbstractIncreased access to multi-anvil high-pressure devices interfaced to synchrotron X-ray radiation sources has led to a new class of experiments. These new capabilities include (a) high-precision crystal structure determination and refinement from powder X-ray diffraction data; (b) the determination of kinetic parameters and structure from time-resolved diffraction data; (c) the determination of absolute pressures by the combined use of ultrasonic techniques at high pressures and temperatures with simultaneous monitoring of X-ray diffraction; and (d) the determination of the strength and rheological properties of materials through the monitoring of the relaxation of broadened diffraction peak widths in the presence of a well-characterized deviatoric stress field generated in the multi-anvil high-pressure apparatus.
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STUDIES OF MULTICOMPONENT OXIDE FILMS AND LAYERED HETEROSTRUCTURE GROWTH PROCESSES VIA IN SITU, TIME-OF-FLIGHT ION SCATTERING AND DIRECT RECOIL SPECTROSCOPY1
Vol. 28 (1998), pp. 375–396More Less▪ AbstractThe understanding of film growth processes is critical for fabricating a variety of thin film-based devices. Many novel film-based devices require growth of films in background gas atmospheres such as oxygen and nitrogen for oxide or nitride films. The studies of film growth processes in background gas environments require special analytical techniques. We discuss a novel time-of-flight ion scattering and direct recoil spectroscopy (TOF-ISARS) technique developed in our laboratory that is capable of providing a wide range of information including film composition and surface structure during growth, at the atomic scale. We also discuss recent work focused on the growth of ferroelectric thin films and their integration with electrode layers relevant to the fabrication of ferroelectric capacitors.
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PEROVSKITE THIN FILMS FOR HIGH-FREQUENCY CAPACITOR APPLICATIONS1
D. Dimos, and C. H. MuellerVol. 28 (1998), pp. 397–419More Less▪ AbstractPerovskite, ferroelectric and paraelectric, thin films exhibit outstanding dielectric properties, even at high frequencies (>1 GHz). This feature makes films such as (Ba,Sr)TiO3 and Pb(Zr,Ti)O3 ideally suited for a wide range of capacitor applications, particularly decoupling capacitors and tunable microwave capacitors; the latter application has been fueled by the recent explosion in wireless communications. The successful implementation of these materials as high-frequency dielectrics requires a detailed understanding of both their processing and materials properties.
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RECENT DEVELOPMENTS IN CONDUCTOR PROCESSING OF HIGH IRREVERSIBILITY FIELD SUPERCONDUCTORS
Vol. 28 (1998), pp. 421–462More Less▪ AbstractThis review discusses the current status and future of high irreversibility field superconductor processing for conductor applications. The topic is introduced by comparing the properties and processability of the most widely studied superconducting materials, and by highlighting the application goals requirements. A major section of the review is concerned with thin film routes for fabricating the high irreversibility superconductor, YBa2Cu3O7−x, because this is an area where there has been much recent success. The prospect of improved conductor properties through processing refinements, as well as the potential for scale-up and cost issues, is considered for the thin film routes.
Bearing in mind the industrial limitations of the thin film technologies, the possibility of adopting an “all thick film” or hybrid “thin film/thick film” technology is considered, with examples of success in this area being given. Various thick film deposition methods are explored, as well as the reaction steps required to achieve the necessary film texture for high-current-carrying conductors.
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POINT DEFECT CHEMISTRY OF METAL OXIDE HETEROSTRUCTURES
Vol. 28 (1998), pp. 463–499More Less▪ AbstractThis article reviews the defect chemistry of perovskite ferroelectric oxides such as barium titanate and lead zirconate titanate. Such metal oxides are being considered for a wide range of applications that include nonvolatile memories and dynamic random access memories. Time-dependent degradation of these devices is controlled at least in part by point defects, which are determined by the defect chemistry of the material. The role of point defects on Pb(Zr,Ti)O3 thin film device properties such as fatigue, switching, polarization relaxation and imprint is discussed.
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PROCESSING TECHNOLOGIES FOR FERROELECTRIC THIN FILMS AND HETEROSTRUCTURES1
Vol. 28 (1998), pp. 501–531More Less▪ AbstractBasic scientific and technological advances on ferroelectric thin films and heterostructures are discussed in relation to the work on nonvolatile ferroelectric random access memories (NVFRAMs) performed by different groups during the last seven years. A reasonable understanding of the synthesis and microstructure-property relationships of ferroelectric thin films for NVFRAMs is demonstrated. Materials integration strategies developed to fabricate ferroelectric capacitors with practically no fatigue or imprint, long polarization retention, and low leakage current are discussed. These properties have been obtained using two ferroelectric materials, Pb(ZrxTi1−x)O3 (PZT) and SrBi2Ta2O9 (SBT), that are the main candidates for application to the first generation of commercial NVFRAMs. A discussion of current knowledge and future research directions is presented.
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THE ROLE OF METASTABLE STATES IN POLYMER PHASE TRANSITIONS: Concepts, Principles, and Experimental Observations
Vol. 28 (1998), pp. 533–562More Less▪ AbstractPolymer phases can be described in the same way as phases in other condensed matter using a number density operator and its correlation functions. This description requires the understanding of symmetry operations and order at different atomic and molecular levels. Statistical mechanics provides a link between the microscopic description of the structure and motion and the macroscopic thermodynamic properties. Within the limits of the laws of thermodynamics, polymers exhibit a rich variety of phase transition behaviors. By definition, a first-order phase transition describes a transformation that involves a sudden change of thermodynamic properties at its transition temperature, whereas higher-order phase transitions are classified as critical phenomena. Of special interest is the role of metastability in phase and phase transition behaviors. Although a metastable state possesses a local free energy minimum, it is not at the global equilibrium. Furthermore, metastable states can also be associated with phase sizes. Metastable behavior is also observed in phase transformations that are impeded by kinetic limitations along the pathway to thermodynamic equilibrium. This is illustrated in structural and morphological investigations of crystallization and mesophase transitions, liquid-liquid phase separation, vitrification, and gel formation, as well as combinations of transformation processes. In these cases, the metastable state often becomes the dominant state for the entire system and is observed over a range of time and size scales. This review describes the general principles of metastability in polymer phases and phase transitions and provides illustrations from current experimental works in selected areas.
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Previous Volumes
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Volume 53 (2023)
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Volume 52 (2022)
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Volume 51 (2021)
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Volume 50 (2020)
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Volume 49 (2019)
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Volume 48 (2018)
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Volume 47 (2017)
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Volume 46 (2016)
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Volume 45 (2015)
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Volume 44 (2014)
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Volume 43 (2013)
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Volume 42 (2012)
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Volume 41 (2011)
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Volume 40 (2010)
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Volume 39 (2009)
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Volume 38 (2008)
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Volume 37 (2007)
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Volume 36 (2006)
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Volume 35 (2005)
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Volume 34 (2004)
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Volume 33 (2003)
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Volume 32 (2002)
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Volume 31 (2001)
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Volume 30 (2000)
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Volume 29 (1999)
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Volume 28 (1998)
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Volume 27 (1997)
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Volume 26 (1996)
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Volume 25 (1995)
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Volume 24 (1994)
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Volume 23 (1993)
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Volume 22 (1992)
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Volume 21 (1991)
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Volume 20 (1990)
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Volume 19 (1989)
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Volume 18 (1988)
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Volume 17 (1987)
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Volume 16 (1986)
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Volume 15 (1985)
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Volume 14 (1984)
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Volume 13 (1983)
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Volume 12 (1982)
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Volume 11 (1981)
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Volume 10 (1980)
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Volume 9 (1979)
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Volume 8 (1978)
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Volume 7 (1977)
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Volume 6 (1976)
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Volume 5 (1975)
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Volume 4 (1974)
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Volume 3 (1973)
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Volume 2 (1972)
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Volume 1 (1971)
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Volume 0 (1932)