bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanocontact Measurements in Superlattices
Authors: Baumann T. , Pethica J. B. , Grimsditch M. , Schuller Ivan K. 
Published: March 2011

ABSTRACTMany metallic superlattices are known to exhibit dramatic anomalous elastic properties as a function of modulation wavelength. All measurements to date measure either a shear modulus or a longitudinal modulus in the superlattice plane. Here we present a method which also probes longitudinal elastic behavior perpendicular to the layers using a nano-hardness tester. In this method, a diamond tip is indented into the material and both the indentation depth and applied force are constantly monitored during loading and unloading. The elastic properties are extracted from the unloading part of the force versus displacement curve. Contrary to the anomaly found in a shear modulus, no anomaly in Young's modulus was found in the present study on Mo/Ni superlattices.
Intrinsic Stress and Structure in Mixed Composition thin films
Authors: Sankur Haluk , Denatale J. , Gunning W. J. 
Published: March 2011

ABSTRACTIntrinsic stress and microstructure of mixed composition films were investigated for several material systems useful in the IR wavelength range. Stress in coevaporated mixed films (analog) deviated from a linear dependence on composition, while in discrete alternating films (digital) it varied linearly with composition. For MgF2-Ge and CeF3-Ge, analog film stress was small and compressive over a large range of intermediate compositions despite the fact that the constituent materials had high tensile stress. The stress behavior correlated with changes in the microstructure. Low stress compositions were observed to correspond to enhanced grain size in the mixed film. These results have significant implications for the design of gradient-index thin-film structures.
Correlations and Ordering in (GaSb)1−xGe2x Alloys
Authors: Newman Kathie E. , Gu Bing-Lin , Fedders P. A. 
Published: March 2011

ABSTRACTThe semiconducting alloy (GaSb)1−x Ge2x is an example of a mixed crystalline alloy that undergoes a phase transition between its constituent crystal types. The order-disorder transition modifies both the long-range and short-range order in the alloy as a function of composition x. By using the Kikuchi approximation, the bond probabilities are calculated and then compared with EXAFS data. These calculations show that the EXAFS data are consistent with the existence in (GaSb)1−x Ge2x of “wrong” bonds of Ga-Ga and Sb-Sb. The theory also predicts a violation of Vegard's Law for the behavior of the mean bond length as a function of composition x.
The Structure of a-Si:H,F/a-Si,Ge:H,F Interfaces
Authors: Conde J. P. , Shen D.-S. , Campbell I. H. , Fauchet P. M. , Wagner S. 
Published: March 2011

ABSTRACTWe study the interface between un-alloyed a-Si:H,F and an a-Si0.4,Ge0.6:H,F alloy using superlattice structures. From infrared spectroscopy we estimate a width of 8 A for the excess hydrogen layer, and X-ray diffraction data give us a width of 2Å contributing to the width of the diffraction peak. Vibrational Raman scattering data show that the ratios of the number of Si-Si, Ge-Ge and Si-Ge bonds is not altered by changing the number of interfaces. This fact allows us to establish an upper limit for the interface width of 3 atomic layers, i.e. one layer in each partner plus an intermediate layer.
Optical Modulation Spectroscopy of a-Si:H Based Multilayer Structures
Authors: Zhou T. X. , Stoddart H. , Vardeny Z. , Tauc J. , Abeles B. 
Published: March 2011

ABSTRACTSteady state optical modulation spectrum of a-Si:H/a-SiNx:H multilayer structure, its temperature dependence and time decay have been studied. For multilayers with very thin sublayers the onset of the spectrum is more gradual and occurs at higher energy than the spectrum for unlayered a-Si:H, indicating a broadening of the band tail. For larger layer thicknesses the optical modulation spectrum is compared to that for P-doped a-Si:H and interpreted as due to charged dangling bonds at the interfaces.
Exafs Studies of Grain Boundary Diffusion and Segregation
Authors: Heald S. M. , Chen H. , Tranquada J. M. 
Published: March 2011

ABSTRACTThe dominant pathway for thin film interdiffusion and interface reactions is often via grain boundaries. We have made EXAFS measurements of grain boundary constituents for two systems: interdiffusion in Ag-Au bilay-ers and solid state reaction of Nb with a copper-tin bronze to form Nb3Sn. The Ag-Au results indicate that Au in saturated Ag grain boundaries has an environment similar to a dilute Au in Ag solution with reduced coordination. For the Nb-bronze reaction, the results for the Cu environment indicate distinct changes in the grain boundary environment when small amounts of Ti, Hf, Zr, and Ta are added to the starting Nb. Both results demonstrate the ability of EXAFS to probe grain boundary environments, and to provide important structural information in understanding solid state diffusion and interdiffusion in thin film systems.
Properties of Metal Fluoride Films Deposited by Laser and E-Beam Evaporation
Authors: Sankur Haluk , Woodberry F. , Hall R. , Gunning W. J. 
Published: March 2011

ABSTRACTThe properties of metal fluoride films (MgF2 CeF3, LaF3 CaF2 and SrF2) deposited using cw laser and electron-beam evaporation were compared. The differences in film properties were subtle, but important. Films obtained by laser evaporation have lower losses in the UV (185–250 nm) and slightly better crystallinity than the films deposited by e-beam evaporation. Other optical and mechanical properties were independent of preparation method. Differences in the film properties were tentatively attributed to the higher proportion of dissociated species in the évaporant plume of the laser-evaporated materials.
Thin Metal Film Adhesion Studies on GaAs
Authors: Bardin T. T. , Pronko J. G. , Kinell D. K. 
Published: March 2011

ABSTRACTComparative thin film adhesion studies were performed on GaAs substrates using Au or Au-Ni-Ge, metallization materials. The influence of parameters such as crystal orientation, substrate surface preparation, deposition vacuum conditions, thickness and composition of films, and post-evaporative treatment such as ion-beam mixing and thermal annealing, on film adhesion was considered. The quality of the adhesion bond was measured using Scotch tape tests and a Sebastian adhesion tester. Film interfaces were characterized using AES, XPS, and RBS techniques. The results indicate that the most important factors dominating the quality of adhesion were surface preparation and the deposition vacuum conditions. Films deposited under optimum conditions were found to adhere so well that the GaAs crystal would fracture before the film would pull free of the substrate. The influence of ion beam mixing on the quality of adhesion was tested and only in the cases of depositions under the less optimum conditions, where the adhesion was poor, could an improvement be made in the adhesive properties.
The Diffusion of Phosphorus and Indium into Gallium Arsenide from Polycrystalline-Silicon
Authors: Kavanagh K. L. , Magee C. W. , Mayer J. W. 
Published: March 2011

ABSTRACTArsenic or phosphorus doped polycrystalline-Si (poly-Si) acts as a diffusion source when deposited on GaAs. Non-Fickian Si diffusion into GaAs has been observed following heat treatments above 700°C. In this paper, the diffusion of In and P from poly-Si at temperatures between 800 and 1020°C is presented. These impurities, introduced into the poly-Si by in-situ plasma deposition, implantation or vapor annealing, diffuse rapidly into the GaAs. Results from particle induced x-ray analysis, transmission electron microscopy, Rutherford backseat tering and secondary ion mass spectroscopy indicate 80% substitutional In and P at interface concentrations of approximately 10 and 25 at%, respectively.
Superconducting Mbtallic Supkrlattices
Authors: Falco Charles M. , Vaglio Ruggero , Cucolo Annamaria 
Published: March 2011

ABSTRACTSince the coherence length is of order 50 Å to 1 μm, it is possible to alternately layer thin films of a superconductor with another material to affect the physical properties of the resulting superlattice. A brief description of our sputtering technique used to prepare superlat t ices consisting of Nb/Cu and Ta/Mo is given. Optical interferometry, x-ray diffraction and ion beam analysis techniques independently confirm that control of ±0.3% is achieved over the amount of material deposited in each layer. Results of a study of Josephson tunneling to Nb/Cu metallic super lattices are reviewed. These measurements enable a determination of the London penetration depth to be made as a function of superlattice layer thickness.
Exafs Studies of Semiconductors
Authors: Bunker Bruce A. 
Published: March 2011

ABSTRACTRecent results from EXAFS spectroscopy are discussed, including (i) the determination of the site and local bond lengths of Fe impurities implanted into Si, (ii) the determination of the ferroelectric phase transition in Pb1−x Gex Te as order-disorder rather than displacive, and (iii) the nondestructive measurement of Aℓ diffusion into GaAs at an Aℓ/GaAs Interface.
Constitutive Laws for Ceramics Exhibiting Stress-Induced Martensitic Transformation
Authors: Lambropoulos John C. 
Published: March 2011

ABSTRACTThe theory of internal variables is used in order to develop multiaxial constitutive laws for ceramics undergoing martensitic stress-assisted transformation, such as partially stabilized zirconia or A12O3-ZrO2. The internal variable is identified with the volume concentration of transformed particles, and we assume that transformation occurs so that the change in potential energy due to the transformation is maximized. When the rate of transformation depends on the applied stresses only through the corresponding change in potential energy, it is shown that the inelastic strain rates are along the normal of a stress function in stress space. The constitutive law depends on all three stress invariants. We further discuss specific stress environments such as crack tip fields, the special case of homogeneous transforming particle distribution, and conditions under which normality is not obeyed.
Excinier Laser Radiation Induced Rapid-Solidification of Alunjinumi and Aluminumi Alloys
Authors: Antony G. , Strutt P. R. 
Published: March 2011

AbstractA study of the effects of high intensity excimer laser radiation (249nm.) of aluminum and an Al-Si alloy reveals a variety of intriguing surface topographical features. Important parameters determining these include the energy-density and the number of short-duration (≈22ns.) pulses. Specific attention has been devoted to determining the condition for the onset of surface melting, and the physical effects of further increasing the energy density. A study of the frozen-in surface wave structure has been used to determine the approximate solidification time and the solidification-front velocity. As well as overall surface melting, an interesting phenomenon is the localized melting occurring at precipitates which preferentially absorb the incident radiation. This phenomenon has been studied in an Al-Si alloy subjected to single and multiple pulses; the effect of the latter has been found to have a striking effect.
Unusual Rapidity of Electron Beam Transient Tempering
Authors: Tauqir Anjum , Strutt Peter R. 
Published: March 2011

AbstractElectron beam rapid solidification of molybdenum-base high speed steels results in quenched-in metastable phases containing a high concentration of alloying elements. Thermal reprocessing of such material by momentary interaction with the electron beam results in decomposition of martensite at a rate ≈ 100 times faster than that occurring during conventional thermal treatment. It is postulated that this arises from a high concentration of 'defect cluster nucleation sites' during the rapid up-quenching. The product of short thermal treatment is a dispersion of 2–5 nm very fine precipitates identified using transmission electron microscopy as MC type carbides.
Preparation and Gas Addition of Soft Magnetic Pure Iron Thin Film by Dual Ion Beam Sputtering
Authors: Nagakubo M. , Kawano A. , Naoe M. 
Published: March 2011

AbstractPure iron thin films with soft magnetic properties and good chemical stabilities have been prepared by Dual Ion Beam Sputtering (DIBS). Four kinds of gas, that is, hydrogen, helium, nitrogen and argon were introduced respectively to the auxiliary ion source as the additional element in the film and also for the purpose of bombardment during deposition. The dependence of crystal structure and magnetic properties of the films on the preparation condition, especially, on the effect of various gases added in the films by ion bombardment onto the depositing film surface, has been investigated.Saturation magnetization 4πMs of iron film including gas atoms is usually smaller than that of bulk iron which has 4πMs of 21.5kG. For example, 4πMs of the film prepared by conventional planer magnetron sputtering remains about 15kG. Such a remarkable difference in 4πMs may be primarily attributed to the considerable amount of argon atoms included in the film due to argon pressure as high as 10mTorr. It may be also caused by high energy particles bombarding onto the iron film surface during deposition. On the other hand, pure iron thin films prepared by Dual Ion Beam Sputtering can have 47Ms as high as 21.5kG, and coercive force Hc as low as about 4 Oe by controlling the ratio of sputtering iron atoms to argon gas atoms, impinging onto the substrate, and the arrival energies both of them. Magnetic properties and crystal structures of the iron thin films depend significantly on the kind of added gas. In this study, it has been found that bombardment and addition of adequate gas atoms with proper energy results in an improvement of atomic ordering and microscopic uniformity in the films.
Magnetic Properties of Composite Amorphous Powder Cores
Authors: Chang Hong-Yow , Yao Pei-Chih , Huang Der-Ray , Hsu Shu-En 
Published: March 2011

AbstractComposite amorphous powder core made by field-annealing with new insulations could improve the high frequency AC magnetic and mechanical properties. All of the amorphous ribbons with composition Fe78B16Si5C and Fe40Ni38Mo4B17Si were annealed at temperature higher than their embrittlement temperature but lower than the crystallization temperature. After the ribbons become brittle, they were mechanically crushed and milled to produce powders with size about 50 ∼ 250μm. To make a core, the amorphous powders combined with insulation binder were put into an evacuted toroidal followed by hot mechanical compaction. The weight percentages of binder were about 3 wt%, 5 wt% and 10 wt%. Field-annealings were carried out for different conditions in an Ar (or N2) atmosphere chamber at elevated temperature with applied field about 10 Oe. The initial magnetization curve and saturation magnetization were measured by vibrating sample magnetometer (O≤H≤10 KOe). DC and AC magnetic properties such as permeability, coercive force, core loss, etc. were tested by B-H loop tracer. It shows the AC properties can be improved by increasing the particle size of the amorphous powder and by increasing the interparticle contacts at high frequency.
Magnetization Reversal in Amorphous TbFe Films
Authors: Calkins J. , Mansuripur M. , Ruane M. 
Published: March 2011

AbstractObservations under polarized light of magnetization reversal in thin amorphous films of TbFe alloys indicate that the reversal process is initiated at inherent nucleation sites where reverse-magnetized domains appear at fields below coercivity. The nuclei then grow in time until they cover the entire sample. The process of nucleation and growth seems to be dominated by the microstructure, since samples with identical bulk magnetic characteristics (such as composition, hysteresis loop and coercivity) exhibit quite different reversal behavior. This process is also dependent upon the history of magnetization of the sample.
Formation and Consolidation of Mechanically Alloyed Amorphous Powders
Authors: Dolgin B. P. 
Published: March 2011

AbstractMechanical alloying (MA) of iron, cobalt, and nickel with titanium and also with samarium produces a continuous growth of an amorphous phase. X-ray diffraction analyses show that the growth of the phase is described by a square root of time law. Differential scanning calorimetry data also confirm that mechanically alloyed powders are amorphous. Dry MA and MA in the presence of toluene are compared. The rate of alloying is much higher in the presence of toluene. Amorphous powders re-alloyed with the fast diffuser are consolidated by means of extrusion.
Bulk Amorphous Metals From Metallic Composites by Solid State Reaction
Authors: Schultz Ludwig 
Published: March 2011

AbstractThe amorphization reaction in mechanically prepared metallic Ni-Zr composites has been investigated by X-ray diffraction, electrical conductivity and magnetization measurements during isothermal annealing. The formation kinetics of the amorphous phase are determined by the diffusion of the Ni atoms across the amorphous NiZr layer. The diffusivity of Ni atoms in the initially formed amorphous Ni58.5 Zr41.5 is measured in the temperature range from 225°C (Dni= 5.3×10−17 cm2/sec) to 325°C (Dni= 1×10−14 cm2/sec). The data fit an Arrhenius plot with an activation energy of 1.4 eV. Magnetic coercivity measurements indicate that neither recovery nor recrystallization occurs in the Ni layers during the reaction. The Kirkendall effect caused by the anomalous fast diffusion of Ni is directly monitored by dilatometric measurements. Microhardness results are also presented. The role of a diffusion-related growth selection favoring the amorphous phase is critically assessed with respect to the glass formation.
An Atom Probe Study of Boron Segregation to Line and Planar Defects in Ni3Ai
Authors: Horton J. A. , Miller M. K. 
Published: March 2011

AbstractAtom probe analyses of rapidly solidified, boron-doped Ni-24 at. % Al subjected to various heat treatments have shown boron segregation to a wide range of linear and planar defects. These include dislocations, superlattice intrinsic stacking faults, antiphase boundaries, twin boundaries, low-angle boundaries (dislocation cell walls), and high-angle grain boundaries. Boron coverage of these features was found to vary along a particular linear or planar defect and from boundary to boundary.
Site Occupation Determinations in Ni3Ai by Atom Probe
Authors: Miller M.K. , Horton J.A. 
Published: March 2011

AbstractThe site occupation of three substitutional elements, hafnium, iron and cobalt, in substoichiometric Ni3Al was determined from atom probe field-ion microscopy. The hafnium was found to have a strong preference for the aluminum sites, the cobalt had a strong preference for the nickel sites, and the iron had a weak preference for the aluminum sites. The atom probe results were in agreement with zone axis electron channeling microanalysis of the same alloys and predictions from the position of the solubility lobes in the ternary phase diagrams.
Lattice Occupation Determination of Hafnium in Ni3Al by Pac
Authors: Bohn H.G. , Schumacher R. , Vianden R.J. 
Published: March 2011

AbstractUsing the perturbed angular correlations technique we have investigated the intermetallic alloy Ni76Al24Hf1 in order to determine the lattice location of the Hf in the ordered Ni3Al structure. From the fact that the Hf atoms sense an electric field gradient it is concluded that most of the Hf resides on Ni-sublattice sites.
The Strength and Ductility of Intermetallic Compounds: Grain Size Effects
Authors: Schulson E.M. , Baker I. , Frost H.J. 
Published: March 2011

Since writing on this subject two years ago [1], a number of developments have occurred, particularly in relation to the mechanical properties of the L12 nickel aluminide Ni3Al. Some elucidate the nature of the yield strength and the extraordinarily beneficial effect of boron on low-temperature ductility. Some others expose, at least in part, the nature of the marked reduction in ductility at elevated temperatures. Another considers the mechanisms dominating creep deformation. Also during this period, contradictions have appeared: the relationship between the yield strength and the grain size, d, at room temperature has been contested, and opposing views of grain refinement on ductility have been reported.This paper reviews these developments. Although broadly directed at intermetallic compounds, the discussion is specific to Ni3Al. The hope is that the knowledge and understanding gained about this compound will benefit the class as a whole.
Deformation of Single Crystalline Mn3Sn
Authors: Lee J. Y. , Pope D. P. , Vitek V. 
Published: March 2011

AbstractSingle crystalline Mn3Sn was chosen as a model material for a study of the deformation machanism of DO19 ordered alloys. Single crystals were grown by the Bridgman method in an argon atmosphere. Compression test specimens of six different orientations were cut from the bulk single crystals by electric discharge machining and polished for slip trace analysis. Compression tests were carried out in an Instron testing machine at a strain rate of 1.2 X 10−3 s−1 at temperatures ranging from 77 OK to 1180 oK. Tests at temperatures above 400 oK were performed in an argon atmosphere while those of lower temperatures were performed in air.Preliminary results were obtained and analyzed in order to determine the temperature and orientation dependence of the operating slip systems and the yield stress. Basal slip was observed to be the dominant slip mechanism. Slip lines were observed on specimen surfaces compressed at low temperatures but such observations were difficult on specimens deformed at temperatures above 1000 OK due to surface contamination.An anomalous positive temperature dependence of the critical resolved shear stress for basal slip was found, similar to that reported for octahedral slip in many intermetallic compounds with the Ll2 structure.
Fatigue of Intermetallic Compounds
Authors: Stoloff N.S. , Fuchs G.E. , Kuruvilla A.K. , Choe S.J. 
Published: March 2011

AbstractThe fatigue behavior of intermetallic compounds is reviewed. The effects of long range order, stoichiometry, test temperature and test environment on crack initiations high cycle fatigue lives and crack growth rates are emphasized. In the case of Ni3Al+B stoichiometry affects high cycle lives largely through the influence of aluminum on ductility and notch sensitivity. High cycle fatigue behavior of Fe3Al is dependent upon stoichiometry and temperature in a complex way which is connected with the formation of superlattice dislocations and with phase changes during high temperature exposure. Oxygen and hydrogen are shown to be detrimental to high cycle fatigue and crack growth in several compounds.
Deformation of the Intermetallic Compound Al3Ti and Some Alloys with An Al3Ti Base
Authors: Yamaguchi M. , Umakoshi Y. , Yamane T. 
Published: March 2011

AbstractIn this paper, firstly, the results of deformation experiments which have been made on Al3Ti and Al3Ti-base alloys are reviewed. Secondly, the possibility of the improvement of ductility of Al3Ti by alloying processes is discussed, and then possible alloying elements for this purpose are suggested. Thirdly, the oxidation resistance of Al3Ti is described and then possible future technological applications of Al3Ti are briefly discussed.