bluuebunny/crossref_metadata_2025 huggingface dataset:
Microanalytical and Structural Characterization of Optical Materials By Electron Microscopy and Related Specitroscopies
Authors: Krishnan Kannan M.
Published: March 2011

The fine probe forming capabilities of an analytical electron microscope combined with the development of related spectroscopies, diffraction and imaging techniques, makes it possible to obtain structural and chemical information from multiphase materials at high spatial resolution. These microanalytical methods are described with relevant examples from our studies of compounds in the A12O3-AIN pseudobinary system, a potential window material, low-pressure synthesized diamond, diamond-like carbon and hydrocarbon films. A comprehensive example of the characterization of a novel AION poltypoid structure (32H), illustrative of both the information content obtainable from these techniques at any particular level of resolution and the need to employ all the complementary methods of analysis, is discussed. Efforts to characterize a variety of diamond-like carbon films by the measurements of both the low-loss plasmon resonances and the fine strcture in the core-loss edges observable in the energy-loss spectrum, to obtain sp3/sp2 ratios are outlined. The electronic structure of thin film diamonds, synthesized by a plasma enhanced chemical vapour deposition method, has been shown to be in agreement with band structure calculations.
Characterization of KNbO3 Thin Films Deposited by Ion Beam Sputtering using a Computer-Controlled Rotating Target Holder
Authors: Ameen M. S. , Graettinger T. M. , Auciello O. , Rou S. H. , Kingon A. I. , Krauss A. R.
Published: March 2011

KNbO3 is a strong candidate as a material for use as channel waveguides due to a high electrooptic figure of merit. High quality single crystals are difficult to obtain due to incongruent melting of the compound. Control of cation concentration and oxygen incorporation are problems encountered in current thin film processing routes.

In order to overcome the problems discussed above, an ion beam deposition system featuring a computer-controlled rotatable target holder and quartz crystal resonator (QCR) feedback loop has been developed. Multicomponent films are produced via sputtering from elemental or compound targets sequentially exposed to an ion beam. Initial results are presented on the use of this new technique for the deposition of KNbO3. Pressed KNbO3, Nb2O5, and KO2 powders were used as sputtering targets. By varying the programmed thickness of deposited film from each target being sputtered, the ratio of K:Nb could be reproducibly controlled. The variation in sticking coefficients due to substrate temperature was also compensated for in this manner.

Thin films were analyzed by X-ray diffraction and TEM to determine phases present and film microstructure. Film morphology and composition has been studied as a function of substrate temperature, layer thickness, and ion beam process parameters. The relation between deposition parameters and film characteristics are discussed.
Structural and Optical Characteristics of Thin Films Deposited by Ionized Cluster Beam
Authors: Yamada Isao
Published: March 2011

In ionized cluster beam (ICB) deposition, crystal properties can be controlled by changing the acceleration voltage and the ionization current. Therefore, the physical and chemical characteristics of the deposited films can be controlled. This controllability in ICB deposition allows one to deposit new optical films. These films are expected to have many new applications over optical range from x-ray to visible. This paper describes film examples for an X-ray mirror with low stray scattering, for an excimer laser mirror with very high damage threshold power and for dielectric optical coatings. These results show that the ICB technique offers much potential for developing new optical thin films in a wide range of applications.
The Effects of Biasing on the Optical and Electrical Properties of RF Sputtered VO2
Authors: Razavi A. , Hughes T. , Bobyak L.
Published: March 2011

Vanadium dioxide was deposited on sapphire substrates by RF reactive sputtering. Biasing of substrates during deposition was used to alter both resistivity and infrared transmission of VO2 thin films. It has been found that as the negative dc bias potential is increased, films in the metallic state show an increased transmittance of IR wavelengths between 2.5 and 6 μm. Also, the resistivity ratio of the semiconductor to metal phase as a function of bias potential is found to reach a maximum value after which further increases in bias cause degradation of electrical properties. X-ray diffraction analysis was used to study film composition.
Optical Dispersion Relations for “Diamondlike” Carbon Films
Authors: Alterovitz Samuel A. , Sieg Robert M. , Shoemaker Neil S. , Pouch John J.
Published: March 2011

Ellipsometric measurements on plasma deposited “diamondlike” amorphous carbon (a-C:H) films were taken in the visible, (E = 1.75 to 3.5 eV). The films were deposited on Si and their properties were varied using high temperature (up to 750 °C) anneals. The real (n) and imaginary (k) parts of the complex index of refraction N were obtained simultaneously. Following the theory of Forouhi and Bloomer (Phys. Rev. B34, 7018 (1986)), a least squares fit was used to find the dispersion relations n(E) and k(E). Reasonably good fits were obtained, showing that the theory can be used for a-C:H films. Morever, the value of the energy gap Eg obtained in this way was compared to the Eg value using conventional Tauc plots and reasonably good agreement was obtained.
Nitrogen Doping of ZnO Prepared by Organometallic Chemical Vapor Deposition
Authors: Pan H-C , Wessels B. W.
Published: March 2011

ZnO layers were grown by organometallic chemical vapor deposition. Films were deliberately doped with nitrogen by incorporating ammonia into the ambient during growth. The resistivity of the films depended strongly on the ammonia partial pressure. The layers were n-type with resistivities in the range of 0.1 − 360 ohm-cm. The films exhibited strong ultraviolet nearbandedge photoluminescent emission. Emission was ascribed to recombination of bound excitons at neutral acceptors, presumably involving substitutional nitrogen.
Silicon Hydride Formation in Co-60 Irradiated Optical Fibers
Authors: Evans Bruce D.
Published: March 2011

Doping with hydrogen is shown to reduce the sensitivity of optical fibers to form optical attenuation bands as a result of ionizing radiation and to increase the recovery rate in the near infrared after the exposure. In this case silicon hydride is shown to form in low-OH, pure silica fibers upon Co-60 irradiation. The ratio of radiolytically induced changes in silicon hydride to silicon hydroxide is estimated to be greater than ten. The more numerous radiolytic formation of SiH species implies the participation of oxygen vacancy type defects in the radiolytic process.
Specular Infrared Reflectance Study of Hot Pressed Rare Earth Sesquisulfide Powders
Authors: Vaughan Cheryl M. , White William B.
Published: March 2011

Specular infrared reflectance spectra were made on hot pressed powder samples of rare earth sulfides of composition Ln2S3. The reflectance curve obtained from the Kramers-Kronig analysis is the deconvolution of the sum of the reflectance curves from the multiple grains, giving the bulk dielectric constant within the 25 cm−1 to 400 cm−1 range and transverse and longitudinal optic modes for the bulk material. Reflectance spectroscopy has shown to be a very good alternative to infrared transmission spectra in the far infrared range to obtain electro-optical information on ceramic powders.
Guided Wave Devices Based on III-V Heterojunctionand Quantum Well Structures
Authors: Yu P. K. L. , Chang W. S. C. , Pappert S. , Kellner A. L. , Lin S. C.
Published: March 2011

Guided wave technology based on III–V compound semiconductor materials is important for optical signal processing, fiber communication and sensor applications. The provision of heterojunction and quantum well materials by LPE, MBE, and MOCVD have led to new concepts and techniques in tailoring the properties of discrete devices and optoelectronic integrated circuits. This paper discusses the electro-optical properties of heterojunction, quantum well, superlattice based on two novel effects, the Franz-Keldysh effect in bulk materials and the quantum confined Stark effect in semiconductor quantum wells. The electroabsorption and electrorefraction properties resulted from these effects are utilized in the realization of some waveguide modulators. Materials based on InGaAsP/InP heterojunctions, InGaAs/GaAs strained layer quantum wells and InGaAs/InP quantum wells will be emphasized.
Formation and Properties of Thermosetting and High TgSystems
Authors: Gillham John K.
Published: March 2011

A review of research in the author's laboratory on the conversion of reactive liquids to amorphous polymeric glasses is presented. Inter-relationships between reactants, reaction conditions, and subsequent material properties of thermosetting and high Tg polymers are discussed from the point of view of a generalized time-temperature-transformation (TTT) diagram.
Area-Selective Laser Processing Techniques for Multichip Interconnect
Authors: Liu Y.S. , Cole H. S.
Published: March 2011

The interest in laser processing technology has increased significantly in recent years because of increasing demands for application-specific IC design and fabrication, yield enhancement, circuit restructuring, and prototyping; all of these benefit from an adaptive processing technique using direct energy for improvement of precision, resolution, process automation, and turnaround time. This paper reviews several laser-patterned metallization techniques developed for high-density multichip interconnection applications. Key material and process requirements for developing a viable laser-direct-write interconnect technique on polyimide are addressed.
The Influence of Thermal and Solvent Cycling on the State of Stress in Polyimide Coatings
Authors: Sackinger Scott T. , Royan R. Van , Farris R. J.
Published: March 2011

To evaluate the influence of permeant and temperature exposure on the state of stress in polyimide coatings, uniaxial experiments on thin polyimide films held at constant length were performed. The uniaxially constrained poly(4,4′,-oxidiphenylene pyromellitimide) or PMDA-ODA films were exposed to methylene chloride while the stress was monitored. It was found that the stress was reduced to zero from a stress as high as 40 MPa by the swelling with methylene chloride. Attempts to remove the methylene chloride at room temperature with a nitrogen purge resulted in a stress increase of only 8 MPa. However, the remaining stress of an additional 20 Mpa was recovered when the sample was heated to 350°C and returned to room temperature. Temperature exposures of 150°C and 200°C resulted in a stress increases of only 14 MPa and 17 MPa, respectively. These observations suggest a strong coupling between the stress state, temperature and equilibrium swelling by permeants.
Applications of SIMS to Spatially Modified Polymer Film Characterization
Authors: Linton Richard W. , Judy Cheryl L. , Maybury Susan G. , Corcoran Sean F.
Published: March 2011

The predominant application of secondary ion mass spectrometry (SIMS) to organic polymeric solids has been the molecular monolayer analysis of thin films in the “static” mode. The primary emphasis in this paper, however, is the evaluation of SIMS for two or three-dimensional compositional mapping studies of spatially modified polymers. This often requires the use of the “dynamic” SIMS mode to provide lateral images, depth profiles, or 3-D image depth profiles. Selected applications are presented including SIMS studies of surface derivatized polymers, metal-doped conductive polymer films, and patterned polymeric materials or fibers. One analytical objective is to assess the extent to which compositional information is limited by primary beam damage. The outlook for SIMS instrumentation combining high lateral spatial resolution with minimal primary beam damage to surface molecules is summarized, for example the combination of microfocused liquid metal ion sources and time-of-flight mass spectrometry.
surface Enrichment in Polymer Blends: Simple Theory and an Experimental Test
Authors: Jones R.A.L. , Kramer E.J. , Rafailovich M.H. , Sokolov J. , Schwarz S.A.
Published: March 2011

If a polymer mixture which is in the bulk one-phase region is next to an interface - this may be with another polymer, with a non-polymeric solid, or with the air - the composition of the mixture at the interface will be different from the bulk [1–4]. There are two questions we would like to understand: what determines the composition of the mixture at the interface, and how does that composition increment decay back to the bulk value. This surface or interface segregation has important practical consequences; in the surface case such segregation will profoundly affect wettability, with consequences for the strength of adhesive joints and the biocompatibility of polymeric surgical implants, as well as influencing friction and wear; at interfaces with non-polymers segregation is important for the adhesion of mixed polymer phases to non-polymer phases such as reinforcing fibres or fillers. In this paper we describe some experiments on surface segregation in a very well characterised model system and we describe a recent theory that can be quantitatively tested by our data. We will consider the consequences of this new understanding of surface segregation in polymer mixtures, and we will argue that many of these conclusions may be carried over to the more general case of interface segregation, which opens up a number of interesting technological possibilities.
Characterization of Interfaces Between Polymers and Metals by Static SIMS
Authors: Ooij W.J. Van
Published: March 2011

The use of static Secondary Ion Mass Spectrometry (SIMS) in the characterization of polymer surfaces and interfaces between polymers and metals is described. Examples are given of the use of SIMS to study the effects of plasma treatments on polyimide surfaces and for the analysis of the interface in metallized polytetrafluoroethylene (PTFE).
XPS Identification of Al-PVA Complex
Authors: Akhter S. , Jo S.K. , Zhou X.-L. , White J.M.
Published: March 2011

Aluminum was deposited on a polyvinyl alcohol film surface by reaction with trimethyl aluminum at 300 K. XPS analysis indicated a carbon free deposition of a monolayer of Al. The Al forms an oxy-carbide complex, AlOC, which exhibits a stoichiometry of 1:1:1 for Al, O and C. Within this complex Al is bonded to both C and O resulting in the appearance of low binding energy peaks in C(ls) and O(ls) spectra. The complex is oriented such that Al forms the outer-most layer. The Al modified surface was hydrophobic compared to the hydrophilic PVA. A reaction mechanism is proposed based on XPS and mass spectrometric data.
Solvent and Curing Effects on Diffusion at Polyimide Interfaces
Authors: Tead S. F. , Kramer E. J. , Russell T. P. , Volksen W.
Published: March 2011

Interdiffusion at interfaces between deuterated polyamic acid (d-PAA) and polyimide (PI) films was investigated with forward recoil spectrometry, an ion beam analysis technique. The PI films were prepared by spin – coating a solution of PAA on a silicon substrate, followed by an anneal at a temperature Ti, which produced partial or complete conversion of the PAA to PI. An overlayer of d-PAA was added in one set of samples by spin – coating from solution and in another set by transferring (in the absence of solvents) a dry d- PAA film onto the PI surface. The bilayer samples were then either annealed at a temperature Td or allowed to stand at room temperature. Bilayers prepared by spin – coating d-PAA from solution directly on partially cured PI films had interdiffusion distances w that decreased with increasing values of Ti to immeasurable levels by Ti = 200 °C. The decrease in w with increasing Ti is thought to be caused by a positive Flory parameter between PAA and PI which increases with the imide fraction in the PI film; the result is an increasing immiscibility between the swollen polymer layers. No interdiffusion occurred in the solventless – transfer samples for any combination of temperatures Ti or Td from room temperature up to 400 °C. Post – annealing of spin – coated bilayers at a temperature Td up to 400 °C was ineffective in producing any additional interdiffusion. Both of these results indicate that thermally activated interdiffusion (even for initially unimidized samples) does not exist in the absence of solvents, an effect attributed to the rapid increase of the glass transition temperature of the polymer with imidization.
Fluorinated Monomolecular Assemblies: Model Systems to Probe Chemical Interactions at the Polymer-Metal Interface
Authors: Chau Lai-Kwan , Porter Marc D.
Published: March 2011

Monomolecular assemblies of n-perfluorocarboxylic acids [CF3(CF2)nCOOH, n=6, 7, and 8] have been adsorbed at silver by spontaneous adsorption from dilute alcoholic solutions. Infrared reflection spectroscopy indicates that the monolayers form by the reactive chemisorption of the carboxylic acid to a carboxylate salt. Ellipsometrically-determined film thicknesses increase linearly with an increase in the perfluorocarbon chain length. Contact angle measurements indicate that the packing density of the films increases with increasing chain length, resulting in an interface with a low surface free energy. The structure and properties of these interfaces are compared to those for monolayers of n-alkanoic acids. The potential utility of such assemblies to probe fundamental chemical and physical interactions at polymer-metal interfaces are also discussed.
XPS Study of the Interface of Polyimide on Cr And Ni.
Authors: Garilli Marco , Marletta Giovanni , Puglisi Orazio , Oliveri Carmelo , Magro Carmelo , Ferla Giuseppe
Published: March 2011

The paper presents a study of three polyimide-oxide interfaces. The Cr-oxide-PI interface seems to undergo a drastic topographical structural rearrangement. The case of the Ni surface is indicative of heavy decomposition of the Ni oxide which induces the decomposition of the polymer film. On the contrary the stabilized Ni surface behaves in a normal manner indicating that the driving force for the decomposition is the instability of the oxide.
Conducting Polymer Films by Ion Implantation
Authors: Lu P.H. , Moody R.A. , Loh I.H.
Published: March 2011

Insulating polymeric sheets were made electrically conductive by ion implantation. The effects of implantation parameters, such as ion species, dose, energy, beam current density, and substrate temperature, on the resultant sheet resistivities were investigated. Surface structural changes of implanted polymers were evaluated by X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and Fourier transform infared spectroscopy (FTIR). Electron spin resonance (ESR) and temperature dependent resistivity measurements were performed to explore the conduction mechanisms of implanted polymers. The results indicate that ion beam modification of polymers proceeds via a similar mechanism as high temperature pyrolysis. The resultant carbon-enriched materials which can be described by the conducting grain model.
Measureme of Soiderability Performance of IC Lead/Leadfinish Sysrems Using the Weiting Baiance
Authors: Wittmershaus Janice , Grayeli N. , Siemimann J. , Vickers E.
Published: March 2011

A critical investigation of the use of the wetting balance to characterize leadfinish solderability is described. The wetting force vs. time curves for matte tin and solder plated copper coupons which have been subjected to well controlled environmental conditions, such as steam and high temperature bakes have been analyzed. Steam exposure was shown to impact greatly the shape of the wetting force curve, with the major effect observed after one hour of exposure and with no significant changes upon further exposure. The high temperature exposure (bake) and associated intermetallic compound formation had little effect on the force-time curve as long as it was protected from oxidation. Results show that when the wetting balance is used in conjunction with SEM and microanalysis tools, it is an excellent diagnostic tool for determining sources of solderability changes.
Passive Thermal Management of Excess Heat from Electronic Devices
Authors: Glatz John J. , Leon Juan F.
Published: March 2011

Thermal management in the packaging of electronic components is fast becoming an enabling technology in the development of reliable electronics for a range of applications. The objective of the paper is to assess the feasibility of using advance high thermal conductivity pitch fiber (HTCPF) as a solution to some of the packaging problems. The general scope will include the following: identification of the candidate material and its potential applications; thermal management of the chip to board interface; thermal management of the heat within the multi-layer interconnect board (MIB); thermal management of the standard electronic module-format E (SEME); and heat transfer thru the enclosure to a remote heatsink/heat exchanger.
Moisture and Purity in Polyimide Coatings
Authors: Beuhler A. J. , Burgess M. J. , Fjare D. E. , Gaudette J. M. , Roginski R. T.
Published: March 2011

Moisture and ionic impurities play a major role in the failure mechanism of integrated devices. [1] The use of organic polymers as microelectronic coatings offers advantages in improved planarization of metal steps, low temperature processibility, and reduction of mechanical stresses. [2] Cited disadvantages are the high inherent moisture absorption and level of impurities. Polymers introduce levels of moisture and impurities 10–100 times greater than vacuum deposited inorganic insulators.[3] Moreover, the combination of ionic impurities and a high humidity environment will degrade attractive polymer properties such as high resistivity and low dielectric constant. [4]
Ceramic Fiber - Fluoropolymer Composites for Electronic Packaging Materials
Authors: Bolt John D.
Published: March 2011

Aluminum nitride (AIN), alumina and aramid fibers have been incorporated into epoxy and fluoropolymer matrices. The fluoropolymer composites have dielectric constants less than 3.4 and losses below 0.3%, measured out-of-plane. In-plane and out-of-plane thermal conductivities of the AIN-fluoropolymer composites averaged 5.2 and 1.3 W/mK, respectively, at fiber volume fractions of 0.26 to 0.29. In-plane thermal conductivities of woven fabric composites were accurately predicted by mixing rules; for non-woven and short fiber composites, thermal conductivities were less than predicted. These composites had higher out-of-plane thermal conductivities due to out-of-plane components of the fiber orientations.
Removal of Processing Aids from Ceramic/Polymer Composites
Authors: Stangle Gregory C. , Rhee Dong-Joo , Aksay Ilhan A.
Published: March 2011

Fundamental issues in the removal of processing aids from ceramic compacts prior to sintering have been investigated, both experimentally and theoretically. A general theoretical model has been developed that couples simultaneous momentum, heat, and mass transfer phenomena in disordered porous materials with the mechanical response predicted by an appropriate poroelasticity theory for partially saturated porous granular materials. The kinetics of pyrolytic degradation of organic processing aids were studied using a thermogravimetric analysis-mass spectrometry (TGA-MS) system.
The Effects of Aluminum Alkoxides on the Synthesis of Composite Powders of Alumina and Titania
Authors: Harris Michael T. , Byers Charles H. , Brunson Ronald R.
Published: March 2011

The synthesis of mixed oxide ceramic powders that consist of very fine (submicron)-monodisperse particles with uniform composition is desirable in the improvement of existing ceramics and the development of new ceramic materials. Metal alkoxide hydrolysis is a very attractive method for the synthesis of ultrapure composite powders at low temperatures by the sol-gel process.

The present study investigates the effects of the hydrolysis of aluminum alkoxides and the condensation products on the growth kinetics and morphology of composite particles containing alumina and titania. Alkoxides of titanium and aluminum are employed; therefore, powders of high purity are produced. Since various solvents are used as media for powder synthesis, the effect of the solvent on particle morphology will also be discussed.
Rapid Omnidirectional Compaction of Y2O3 Stabilized Tetragonal Zirconia
Authors: Pechenik Alexander , Pyzik Aleksander J. , Beaman Donald R.
Published: March 2011

The Rapid Omnidirectional Compaction (ROC) technique has been applied successfully to the densification of TZP (3 mole % yttria) ceramics at 1260°C. The combination of high pressure (830 MPa) and temperature results in the plastic deformation of the ceramic particles. The extent of deformation, and consequently, the ROCing temperature, can be determined by using hot hardness of the ceramic material as an approximation of the ceramic's yield stress. The materials ROCed at 1260°C are characterized by a grain size of 0.15 gim, a flexure strength of 1300 MPa, a hardness of 1340 kg/mm2, and a fracture toughness of 5.0 MPa m1/2.
Densification of Particulate Ceramic Composites: The Role of Heterogeneities
Authors: Jonghe Lutgard C. De , Rahaman Mohamed N.
Published: March 2011

Inert p articulate inclusions in ceramic powder compacts can obstruct densification behavior significantly. The factors that are the causes of this decrease in the sinterability are reviewed. It is concluded that the origin of the sintering difficulty resides in defects that processes such as die compaction introduce during the initial forming of the composite powder compact. Alternative processing methods are suggested that should minimize the negative effects of the dispersed inclusion phase on densification.
Sol-Gel Processing of Advanced Dielectric Ceramics for Microwave Applications
Authors: Schnoeller M. , Wersing W.
Published: March 2011

Highly dielectric ceramics make it possible to markedly miniaturize passive microwave components. We have successfully synthesized ceramic powders of the most important microwave ceramic systems (ZrTiSn)O2, Ba(TiNiZnTa)O3 and Ba(MgTa)O3 by using the sol-gel process. Nonaqueous solutions of metal organics together with different inorganic metal salts were used as precursors. The gels derived from these solutions are homogeneous and transparent. Different drying procedures were investigated in order to optimize powder morphology. Thermoanalytic methods and high -temperature x-ray diffraction were used to study the decomposition of xerogels and the formation of crystal phases, respectively. The calcination process was found to be complete at temperatures well below 750 °C.

For the production of barium-containing powders, wet milling must be avoided because this washes out barium and thus causes undesired phases to appear. A dry milling step of the xerogel solves this problem. The prepared (ZrTiSn)O2 and Ba(TiNiZnTa)O3 already equal or surpass the quality of conventionally prepared ceramics.
Rheological Characterization of a Sol-Gel Process for the Preparation of High Tc Superconductors
Authors: Khan S. A. , Bagley B. G. , Barboux P. , Torres F. E.
Published: March 2011

Superconducting thick films of yttrium-based cuprates can be prepared using a sol-gel technique. Rheological measurements on the precursors are used to identify processing parameters that can lead to better film properties. Steady and dynamic experiments reveal a direct correlation between the properties of the precursor, the final product, and the “age” of the yttrium component used in the precursor. Measurements support a proposed mechanism relating the “age” of the yttrium to the other properties and help to establish a processing methodology to obtain effective superconducting properties.
Synthesis and Structure of Novel Cuprates in the Ba-Y/Ca-Cu-O Systems
Authors: Sunshine Steven A. , Siegrist T. , Schneemeyer L. F. , Marsh P.
Published: March 2011

Two new compounds in the Ba-Y/Ca-Cu-O systems have been grown as single crystals from a Ba(OH)2H2O flux. The compounds Ba3(Y/Ca, Cu)2O7−δ and Ba(Ca, Cu)O3−δ have the Sr3Ti2O7 and the perovskite structure, respectively.
Structural Studies of La2−xBaxCuO4 Between 11–293 K
Authors: Cox D. E. , Zolliker P. , Axe J. D. , Moudden A. H. , Moodenbaugh A. R. , Xu Y.
Published: March 2011

Neutron powder diffraction data have been collected from samples of La1.9Ba0.1CuO4 and La1.85Ba0.15CuO4 in the temperature range 11–293 K. The first material undergoes a phase transition from the tetragonal K2NiF4-type structure (space group 14/mmm) to the orthorhombic La2CuO4-type structure (space group Bmab) at about 280 K, and then a second transition to another type of tetragonal (or near-tetragonal) structure with probable space group P42/ncm. The latter transition occurs predominantly between 50–40 K, but about 10% of the orthorhombic phase persists down to 15 K. Rietveld refinement was carried out at selected temperatures in the different structural regions. The differences among the low temperature structures can be cb acterized by tilting of the CuO6 octahedra about different rotation axes on the basis of the simple X-Y model previously proposed by Axe and coworkers. The tilt angle, which is a measure of the long-range order parameter, is about 3.5° at 15 K.

Data sets were also collected from La1.85Ba0.15CuO4 at 293, 90 and 11K. At the two latter temperatures there was some peak broadening consistent with the distortions observed in previous high resolution neutron [Paul and co-workers] and x-ray [Axe and co-workers] powder studies. Rietveld analysis of the data indicated the presence of local octahedral displacements, but it was not possible to determine the nature of the correlations.
Growth of Superconducting La2−xSrxCuO4 Single Crystals
Authors: Kojima Hironao , Tanaka Isao
Published: March 2011

High quality large single crystals of La2−xSrxCuO4 were grown by the traveling solvent floating zone method(TSFZ method). The crystals up to about 6 mm diameter and 40 mm length were obtained. The composition of the grown crystals was uniform and was determined to be La1.86Sr0.14Cu0.97O3.89. The single crystals were superconductors with Tc=37.5K and δ Tc=1.1K, and had a significant anisotropy of the electrical resistivities at the non-superconducting state.
High Tc Superconductors using Solution Techniques
Authors: Barboux P. , Valente I. , Tarascon J.M. , Khan S. , Shokoohi F. , Henry M. , Morineau R. , Bagley B.G.
Published: March 2011

We have investigated different solution techniques to synthesize the Cu-based superconductors in the thick film form. Thick films of YBa2Cu3O7 have been produced using controlled precipitation techniques. Bi-based and Tl-based materials have been deposited by spraying of ionic solutions. The numerous difficulties encountered during each process are analyzed in order to propose new synthesis procedures such as a new method, based on the precipitation of hydroxides only, which is described as a prospective for lowering the synthesis temperature and shortening the reaction time.
Magnetic Properties of YBaCuO Crystal Prepared by Quench and Melt Growth Process
Authors: Murakami Masato , Koyama Noboru
Published: March 2011

We report a new process which enables the production of YBaCuO that shows high Jc in the presence of magnetic field. Then we show that magnetic properties of such materials can be understood in terms of the Bean critical state model. Giant flux creep is absent even at 77K in such samples.
Structural and Solid State Chemistry of Mixed Valence Oxides
Authors: Jean Galy
Published: March 2011

The structural evolution versus oxygen adsorption ↔ desorption of the LnBa2Cu3O6+x series, the influence of rare-earth substitution on oxygen network and copper coordination (CN = 2, 4, 4 + 1, 5) in Bi2Sr2Ca1−yLnyCu2O8 series (Ln = La, Yb; 0≤y≤1) are followed. Images of parent mixed valence oxides, i.e. vanadium bronzes, with their single or double layers structures versus intercalated ions with ideal intergrowth structures like the new Na0.70V2O5 oxybronze are presented. The ability to exhibit double non stoichiometry, i.e. LixV3O8−y (0≤y≤1) in the homologous series LixV3(1+n)O8+7n (0≤n≤∞) is explained.
Oxygen Stoichiometry and Ordering in HTSC and Other Perovskite-Like Solids
Authors: Alario-Franco Miguel Angel
Published: March 2011

As long ago remarked by WADSLEY, perovskite-like solids have a clear tendency to be non-stoichiometric and both the geometrical requirements of cation coordination and the oxidation state can control the way in which non-stoichiometry is accommodated.

For example, in the case of iron, which shows a particular preference for coexisting octaedral and tetrahedral coordination and in which oxidation states rangingformallyfrom 2 + to 4 + are common in oxides, a Family of Phases AnFenO3n−1, has been described. It includes the members n=2,3,4 and ∞. When the stoichiometries are different from these integralnvalues, disordered 1−D intergrowthhs are observed. Subsequent work has shown that all the intermediate compositions, whether ordered or disordered in 1−D, can still become non-stoichiometric by oxidation at high temperatures (T>1200°C in air) and this originates the formation of 3D microdomains. Of these, up to nine different sets have been shown to coexist in the same crystal.

Similarly, the copper based HTSC, which have a lot in common with perovskite, have shown a marked tendency for being oxygen deficient. In particular, Ybacuo, Ba2YCu3O7±6has been shown to exist in a wide oxygen range extending from, at least RO7.2to RO6(R<>Ba2YCu3). Within that range, and in spite of an apparent structurally monophasic, and thermodynamically bivariant, behaviour, a succesion of ordered states of the oxygen vacancies in 1,2 and 3 dimensions has been found. This, again, suggests the existence of intermediate ordered phases which, on the other hand, can also be non-stoichiometric. Results of our work along these lines is presented and discussed.
A New Class of Oxide Superconductor (Nd, Ce, Sr)2CuO4
Authors: Takayama-Muromachi E.
Published: March 2011

Since the discovery of the high-Tc superconductor in the La-Ba-Cu-O system [1], a great deal of experimental and theoretical effort have been made to clarify the nature of the Cu-based oxides. In order to elucidate mechanism of the high-Tc superconductivity, discovery of a new type of superconductor is no doubt of great importance. Recently, Akimitsu et al. found a new oxide superconductor in the Nd-Ce-Sr-Cu-O system [2]. Soon after their discovery, the superconducting phase was isolated and identified [3]. It has a tetragonal cell with space group P4/nmm and has a structure closely related to but different from the K2NiF4− or T'-Nd2CuO4− -type structure. Although, Tc of the Nd-Ce-Sr-Cu oxide is not so high (ca. 20 K) compared with the 1–2–3 or Bi(Tl)-based superconductors, it has aroused interest widely due to a very simple crystal structure. In this article, I will discuss superconductivity and crystal chemistry of the Nd-Ce-Sr-Cu oxide. Also, various compounds isostructural to it will be presented.
Hole Concentration - Tc Relationships for Nd and Zn Substitutions in YBa2Cu3Oy
Authors: Shafer Merrill W. , Penney T. , Olson B. L. , Greene R. L.
Published: March 2011

One of the intriguing questions involving the copper containing high temperature superconductors is the relationship between the hole concentration and the transition temperature, Tc. We address this question in terms of a proposed “master curve” on a Tc, vs hole concentration plot. This curve shows a maximum at 90K at a hole concentration of approximately 0.2 – 0.22 holes per sheet copper for the 1–2–3 system. In this work we studied the Nd1+xBa2−xCu3Oy and YBa2Cu3−xZnxOy systems to check the validity of this “master curve”. Both Nd and Zn substitutions lower Tc, Nd by reducing the number of holes, consistent with the model given by the curve. The effect of Zn substitution is ambiguous, since both the holes are increased and the Cu-O planes are perturbed. Compensation doping, using both Nd and Zn, shows that the major effect of Zn is to disrupt the Cu-O planes.
Ion Beam Induced Crystallization in Preamorphized Bp(100)
Authors: Kobayashi Naoto , Kobayashi Hisao , Tanoue Hisao , Hayashi Nobuyuki , Kumashiro Yukinobu
Published: March 2011

Ion beai induced epitaxial crystallization (IBIEC) in preaiorphized BP(100) has been investigated by RBS channeling experiients. Re-crystallization was induced by subsequent ion boibardients with 400 keV Kr, 400 keV Ar and 800 keV Ar at temperature range between 200°C and 450°C. The current densities of Kr and Ar ions were selected to give the saie energy deposition rate in the elastic collision process. Epitaxial crytallization was observed at teiperatures luch below those required for the therial solid phase epitaxy (SPE) process (above 800°C). The critical temperature for crystallization at typical current densities was 230°C. The ion species used for the preaiorphization give a weak influence on the regrowth rate. On the scale of deposited energy density in the elastic collisions, ion boibardients with higher electronic excitation efficiency were found to be effective in the regrowth process. Dose rate is found to be of iiportance in the regrowth process. The activation energy observed in Ar ion boibardients was 0.18±0.05 eV.
Ion-Beam Induced Epitaxial Crystallization of NiSi2 And CoSi2
Authors: Ridgway M.C. , Elliman R.G. , Williams J.S.
Published: March 2011

Ion—beam induced epitaxial crystallization (IBIEC) of amorphous N1Si2 and CoSi2 layers is demonstrated. Epitaxial metal suicide layers on (111) Si substrates were implanted with 40 keV Si ions to form amorphous surface layers. IBIEC of amorphous NiSi2 and CoSi2 layers was induced at 13—74°C with 1.5 MeV Ne ion irradiation and proceeded in a layer—by—layer manner from the original amorphous/crystalline interface with activation energies of 0.26 ± 0.07 and 0.21 ± 0.06 eV for N1Si2 and CoSi2, respectively.
Ion Beam Annealing of Si Co-Implanted with Ga and As
Authors: Withrow S. P. , Holland O. W. , Pennycook S. J. , Pankove J. , Mascarenhas A.
Published: March 2011

Ion beam annealing of amorphous Si(100) layers formed by co-implantation of overlapping Ga and As distributions is studied. Annealing was done using 750 keV Si+ ions with the Si substrate held at 300°C. The samples were characterized using 2.0 and 5.0 MeV He+ backscattering/channeling as well as by transmission electron microscopy (TEM). Crystallization of the amorphous Si layer occurs during irradiation via solid-phase-epitaxial growth without impurity precipitation or segregation. Both the Ga and As are mainly substitutional in the Si lattice, even at concentrations in excess of 7 at. % for each species. These results are attributed to compensation effects, most likely through ion pairing of the dopants.
Grain Growth and Phase Formation in Ion Irradiated/Annealed Thin Ni-Al Alloys Films
Authors: Alexander Dale E. , Was Gary S. , Rehn Lynn E.
Published: March 2011

Ion irradiation and annealing studies were performed on Ni, Ni-20 at.%Al multilayers and Ni-20 at.%Al co-evaporated thin films. Xe+ ions were used to irradiate the films and homogenize the multilayers at room temperature. Irradiation of alloy films formed a metastable, supersaturated solid solution of γ phase and an HCP phase. Ion induced grain growth occurred in all films. A factor of 2 greater growth was observed in Ni-Al multilayers compared with coevaporated films irradiated to the same dose. The enhancement is attributed to a heat of mixing effect. Post irradiation annealing of the mixed multilayers formed γ*, the morphology of which was dependent upon the presence of Cu in the films due to substrate mixing from the support grid.
Carrier Lifetime Distributions and Recombination Kinetics in Silicon on Insulator (Simox) Substrate
Authors: Lourenço M A , Homewood K P , Hemment P L F
Published: March 2011

During the preparation of the substrates, involving ion implantation (> 1014 O* cm−2) and extended high temperature annealing (∼ 1350°C), many defects are unintentionally introduced, which can act as trapping and recombination centres. In this paper the carrier lifetime distributions and recombination kinetics determined by Photoconductive Frequency Resolved Spectroscopy (PCFRS) are reported. Comparative measurements of the lifetime distributions in bulk silicon, annealed bulk silicon and device quality SIMOX have been made. In annealed silicon and SIMOX higher order recombination kinetics are observed whilst, as expected, the kinetics are first order in unannealed bulk silicon.

Results of PCFRS measurements made as a function of temperature in the range 350 K to 150 K reveal a strong dependence of the lifetime distribution on temperature, confirming the dominance of carrier trapping. Trap parameters have been obtained from Arrhenius plots of the lifetime distributions.
On the Phase Formation During Ion-Beam Mixing
Authors: Andersen L.-U. Aaen , Bøttiger J. , Dyrbye k.
Published: March 2011

The phase formation during ion-beam mixing of binary transition-metal alloys has been studied by use of Xe* , Ar* , and Ne* as a function of temperature and composition. Especially the composition ranges, where only amorphous phases occur, i.e., the glass-forming ranges, have been investigated. Based on semiempi-rical data on free energies, metastable phase diagrams have been constructed and glass-forming ranges estimated for the case of negative heat of mixing. Taking into account the quite large uncertainties of the applied thermodynamic data, reasonable agreement is observed between estimated and experimental glass-forming ranges. In the case of positive heat of mixing, the initial thin-film structure is near thermodynamic equilibrium. However, for small values of the heat of mixing, it is still possible to form amorphous structures. In the absence of chemical driving forces, this formation cannot be explained in a similar way as in the case of negative heat of mixing. As the nucleation of crystalline phases may differ with and without irradiation, irradiation of amorphous structures at elevated temperatures may create new metastable phases. Preliminary measurement of crystallization of metallic-glass films during irradiation are reported.
Why does Hydrogen Loss Rate Correlate with How Strongly Hydrogen Inhibits Ion Beam Mixing?
Authors: Wistrom R. E. , Borgesen P.
Published: March 2011

Previous studies have shown that the presence of hydrogen in multilayer samples containing Ti reduces ion beam mixing rates. The present study sought to determine why the magnitude of this effect depends on which metal is mixed into Ti and why it is correlated to the rate at which hydrogen leaves the sample during mixing. Hydrogen loss rates of multilayers were compared with those of bilayer samples designed to minimize the effect of mixing. For bilayers, hydrogen loss rates were smaller and did not depend on which metal was mixed into Ti in the same way that multilayer loss rates do. This suggests that hydrogen leaves the multilayer samples because it is bound less strongly in the mixed regions than in the Ti. The primary cause of hydrogen loss is mixing rather than ion beam induced desorption.
Ion Beam Mixing of Sb Schottky Contacts on n-Si
Authors: Malherbe J. B. , Weimer K. P. , Bredell L. J. , Friedland E. , Myburg G.
Published: March 2011

The I—V characteristics of as—deposited antimony Schottky contacts on silicon were extremely sensitive to interface conditions. This led to unpredictable results for the unimplanted contacts. After Si* implantation the contacts displayed more uniform I—V characteristics. Implantation led to higher values for the ideality constant, the series resistance and for the saturation current. The ideality factor seems to decrease at the higher implantation doses (ϕ ≥ 5×1014 Sb+cn−2), while no clear dose dependence patterns were observed for the saturation current and series resistance after implantation.
Ion Beam Mixing of Multelayered Co-B Thin Films
Authors: Choe G. , Walser R.M.
Published: March 2011

Ion beam mixing (with 150 keV 1016 Ar ions/cm2) of multilayered Co-B films with various bilayer periods (BP = TCo + TB, TCo = 4 × TB), and layer thickness ratios, was studied to determine its utility, compared to sputtering, in producing morphological changes in amorphous thin films. All the ion beam mixed films were amorphous, but the morphologies of both the as-deposited and the ion beam mixed films varied with the BP. The in-plane, easy axis anisotropies of the films with the largest BP were obliterated by mixing, although their hard axis coercivities were unchanged. The anisotropy of the films with smaller BPs was increased by mixing. The results indicate that ion beam mixing is a potentially useful method of improving the properties of soft magnetic thin films.
Solute Trapping at a Rapidly Moving Solid/Liquid Interface for a Lennard-Jones Alloy
Authors: Cook Stephen J. , Clancy Paulette
Published: March 2011

Non-equilibrium Molecular Dynamics simulation methods have been used to study the trapping of “impurities” in an Ag5B15 Lennard-Jones alloy where the B atoms are 10% bigger in diameter than A. The observation of surface melting in this system is used to calculate an equilibrium interfacial segregation coefficient. Simulations of rapid melting and resolidification were performed for the (100) and (111) orientations at two different substrate temperatures (0.65 Tm and 0.95 Tm) for each orientation. Solute impurity atoms are shown to have been trapped at greater concentrations in the solid than under equilibrium conditions. Partitionless solidification is observed when the regrowth velocity greatly exceeds the diffusive velocity.
Thermal Annealing of Solid Kr Precipitates in Ni
Authors: Birtcher R. C. , Rest J. , Bergstrom D. S.
Published: March 2011

After implantation into Ni at room temperature, Kr condenses under high pressure as an fee solid aligned with the Ni lattice. Evolution of these precipitates during subsequent thermal annealing to a temperature of 650 C has been followed with transmission electron microscopy and modeled with rate theory.

Room temperature implantation results in a monomodal size distribution of small solid Kr precipitates. When Kr is implanted into Ni at 500 C, some precipitates grow to larger sizes, and the precipitate size distribution becomes bimodal. Annealing to temperatures below 600 C after room temperature implantation produces a bimodal size distribution consisting of small solid Kr precipitates and large Kr bubbles. Annealing above 600 C leads to more complete precipitate motion and coalescence that eliminates all small precipitates and results in a monomodal size distribution of large faceted bubbles.

Rate-theory modelling of Kr implantation into Ni at 500 C suggests that small solid Kr precipitates are immobile and that Kr melting is required for precipitate mobility. Similar calculations for thermal annealing experiments show that the bubble size distribution becomes bimodal when only a small fraction of the small precipitates melt and become mobile during annealing, while the size distribution remains monomodal when all precipitates become mobile after Kr melting at higher temperatures.