bluuebunny/crossref_metadata_2025_split huggingface dataset:
Requirements of Electrical Contacts to Photovoltaic Solar Cells
Authors: Gessert T. A. , Coutts T. J. 
Published: March 2011

ABSTRACTThe importance of contacts to photovoltaic solar cells is often underrated mainly because the required values of specific contact resistance and metal resistivity are often thought to be relatively modest compared with those associated with very large scale integration (VLSI) applications. However, due to the adverse environmental conditions experienced by solar cells, and since many of the more efficient cells are economically advantageous only when operated under solar concentration, the requirements for solar cell contacts are sometimes more severe. For example, at one-sun operation, the upper limit in specific contact resistance is usually taken to be 10−2 Ω-cm2. However, at several hundred suns, this value should be reduced to less than 10−4 Ω-cm2. Additionally, since grid line fabrication often relies on economical plating processes, porosity and contamination issues can be expected to cause reliability and stability problems once the device is fabricated. It is shown that, in practice, these metal resistivity issues can be much more important than issues relating to specific contact resistance and that the problem is similar to that of providing stable, low resistance interconnects in VLSI. This paper is concerned with the design and fabrication of collector grids on the front of the solar cells and, although the discussion is fairly general, it will center on the particular material indium phosphide. This III-V material is currently of great importance for space application because of its resistance to the damaging radiation experienced in space.
On the Origin of Multiple Peaks in the Deep Level Admittance Spectroscopy of Dx Centers in AlGaAs:Sn
Authors: Chakravarty S. , Subramanian S. , Arora B. M. 
Published: March 2011

ABSTRACTDeep level admittance spectroscopy (DLAS) of the Sn-DX centers in Alx Ga1−x As:Sn (0.2 < x < 0.6) shows three peaks SNi, SN2 and SN3. The SN3 peak is identified to be related to the dominant peak of the Sn-DX center observed in the conventional DLTS technique. The SN1 and SN2 peaks are not easily seen in DLTS. A careful analysis of the DLAS data shows that the three peaks are not due to independent (chemically distinct) defects related to Sn, but they are caused by the multiple sates of the same DX center.
Radiation Enhanced Dislocation Glide and Rapid Degradation
Authors: Maeda K. , Yamashita Y. , Maeda N , Takeuchi S. 
Published: March 2011

ABSTRACTConspicuous enhancement of dislocation glides under minority carrier injection is reviewed. Systematic investigation of dislocation glide velocity under electron-beam irradiation in various semiconducting crystals showed that the radiation enhanced dislocation glide (REDG) effect exhibits features expected from the recombination enhanced defect motion (REDM) mechanism. Theoretical analysis, based on the kink diffusion model for the elementary process of dislocation motion, shows that the REDG effect requires enhancement of double-kink formation. An experimental attempt provided an evidence for the smallest double kink formation is the only process that is enhanced by carrier injection. In light of the knowledge available at present, a guide line in device design to minimize degradation in the dislocation glide mode is suggested.
Microstructural Benefits of Rsp in a γ-(Ti-Ta-Al) Alloy
Authors: McCullough C. , Valencia J.J. , Levi C.G. , Mehrabian R. 
Published: March 2011

AbstractTi-15Ta-48Al alloy samples were characterized after arc melting, controlled supercooling experiments and splat-quenching. It was found that primary b.c.c. (β) forms from the melt in all cases. The arc-button exhibits severe Ta segregation toward the dendrite cores which is substantially alleviated by rapid solidification. Increasing bulk supercooling of the melt reduces the size and scale of segregation and ultimately results in a single phase γ structure. Splat quenching also increases homogeneity and alters the post-solidification transformations in three ways: (i) it suppresses the typical precipitation of γt laths in α2, (ii) it inhibits the formation of σ, and (iii) the Ta-rich areas of the β phase transform to B2 instead of α + σ.
Formation of Cubic Ll2 Phases from Al3Ti and Al3 Zr by Transition Metal Substitutions for Al
Authors: Sparks C. J. , Porter W. D. , Schneibel J. H. , Oliver W. C. , Golec C. G. 
Published: March 2011

AbstractAlloys of (AlxM1−x)3Ti where M is V, Cr, Mn, Fe, Co, Nb, W, Fe + Ga or Fe + Ga + Mn were fabricated to form the Ll2 cubic phase, tested for ductility, and characterized by lattice parameter, microstructure, quantitative phase analysis, and phase composition. The elements V, Co, Nb, W, Fe + Ga and Fe + Ga + Mn are hereby newly found Ll2 formers in Al3Ti. Both X-ray diffraction and microprobe analysis were used to identify the phases, their volume fractions and compositions. The amount of ternary addition found in the Ll2 cubic phase varied between 4 and 12 atomic percent. This amount of ternary addition decreased as the atomic radius of the elemental addition increased. Pettifor's Mendeleev number was a useful guide in the selection of elements to form the Ll2 phase but did not correlate strongly with the amount of the ternary addition. For the DO23 phase of Al3Zr, the elements V, Mn, and Co were added to the list of Ni, Cu, Fe, and Cr as elements known to form the Ll2 phase. Little if any ductility was observed in these cubic Ll2 phases which readily cleaved with transgranular failure. To achieve ductility and toughness, more than transformation of these compositions from a lower to a higher symmetry crystal structure will be required.
Kinetics of B2 and D03 Ordering: Theory
Authors: Anthony L. , Fultz B. 
Published: March 2011

AbstractMonte-Carlo simulations (MCS) and the path probability method (PPM) were used to study disorder→order transformations in bcc alloys having the AB3 stoichiometry. Both methods used an explicit vacancy mechanism of ordering and an activated-state rate theory for the vacancy jumps. We studied the evolution of short-range order (SRO) as well as B2 and D03 long-range order (LRO) in alloys that began as random solid solutions. The growth rates of SRO and LRO were significantly higher for the PPM than for the MCS. We attribute this difference to improper handling of correlated vacancy motions in the PPM. The PPM also suffered from an artificial incubation time for the initiation of LRO. Both the MCS and the PPM showed that SRO has a tendency to develop in two stages. In the first stage there is a quick relaxation of the SRO by itself. In the second stage, which occurs with a longer time constant, the SRO and LRO grow simultaneously. Parametric plots of one order parameter against another, here termed “kinetic paths”, are discussed. A variety of different kinetic paths through the B2 and D03 order parameters can be predicted theoretically, depending on the choice of interatomic potentials. This range of calculated kinetic paths is broad enough to encompass our experimental results of SRO and LRO evolution in Fe3Al.
The Effect of Scandium on the Phase Stability of Al3Nb AND Al3Zr
Authors: Nicholson D. M. , Schneibel J. H. , Shelton W. A. , Sterne P. , Temmerman W. M. 
Published: March 2011

AbstractA series of Al-25 (Nb,Sc), at.%, and Al-25 (Zr,Sc), at.%, alloy buttons were arccast in argon and homogenized for 2 h in vacuum at temperatures ranging from 1473 to 1573K. X-ray powder-diffraction indicated that almost all the Nb in Al-25 Nb (DO22) had to be replaced by Sc in order to obtain the Ll2 structure. In the case of Al3Zr much less Sc was required - the single phase Ll2 composition is approximately Al16Zr8Sc.Recent calculations [1,2] show that once the tetragonality is properly included the phase stability of the trialuminide transition-metal binary alloys can be understood in terms of their electronic density of states. The dominating feature is a deep minimum in the density of states just below the major transition metal d-band peak. The exact position of the minimum changes with structure type (i.e., Ll2, DO22, or DO23, and with c/a). The alignment of the Fermi energy with the minimum appears to determine the equilibrium structure. The results of linearized-muffin-tin-orbital [3] (LMTO) electronic structure calculations are compared to the rigid band model and checked against the experimentally determined phase boundaries.
Interaction between Lattice Dislocations and Grain Boundaries in Ordered Compounds: Theory and Experiment
Authors: Pestman B. J. , Hosson J. Th. M. De , Vitek V. , Tichelaar F.D. , Schapink F.W. 
Published: March 2011

AbstractThe interaction between a screw dislocation and symmetric [1 1 0] tilt boundaries under the influence of an applied shear stress was investigated by atomistic simulation. Many-body potentials representing Cu and Ni3Al were used for the description of the interatomic forces. A comparison will be made with in-situ observations in a transmission electron microscope of the interaction of screw dislocations with a coherent twin boundary.
First Principles Calculations of the Equilibrium Mechanical Properties of Simple Metals and Ordered Intermetallic Alloys
Authors: Mehl Michael J. , Osburn Jean E. , Papaconstantopoulos Dimitri A , Klein Barry M. 
Published: March 2011

AbstractHigh-strength, light-weight intermetallic compounds which are ductile at high temperatures are of great technological interest. Purely experimental searches for improved intermetallic materials are time consuming and expensive. Theoretical studies can shorten the experimental work by focusing on candidate compounds which have several of the desired properties. Although current abinitio density functional calculations are not adequate to calculate material properties at high temperatures, it is possible to compute the equation of state and elastic moduli of ordered compounds with several atoms in a unit cell. Known correlations between equilibrium and high temperature properties can then be used to point the way for experiments.We have demonstrated the power of this approach by applying the linearized augmented plane wave (LAPW) method to calculate the equation of state and elastic moduli for several simple metals (Al, Ca, and Ir), binary cubic intermetallics (SbY, AlCo, AlNi, AlRu, and RuZr), and binary L1o intermetallics (AlTi and IrNb). Most of the calculated equilibrium lattice constants are within 3% of the experimentally observed lattice constants. Although the available experimental information about the elastic moduli is limited by the lack of single crystal data for most of these materials, we are in excellent agreement (within 10%) with the available experimental data, except for the shear modulus of IrNb. We also use known correlations between the elastic moduli and the melting temperature to predict melting temperatures of the intermetallics. In general the agreement there is good agreement between theory and experiment, indicating that we can qualitatively predict melting temperatures.
Extra Contribution of Tm Solutes to the Solute-Dislocation/Surface Interactions in Nickel
Authors: Shinoda T. , Masuda-Jindo K. , Suzuki Tomoo 
Published: March 2011

AbstractThe solute-dislocation (S-D) interaction energies for various kinds of transition-metal(TM) and B-subgroup solutes in nickel are calculated using a simple tight-binding electronic theory with lattice relaxations taken into account. As a result, the S-D interaction energy for TM solutes is almost identical with that for B-subgroup solutes when compared at an equal level of size-misfit strain( SMS) in Ni. This is neither more nor less than the answer from the classical elastic theory. However, in the solutions of the present calculation there are some points which can not be derived from the continuum elastic theory. Experiments show that Ni3Al is, differently from Ni, more strengthened by TM solutes than by B-subgroup ones. It is discussed that this may be due to the extra contribution of TM solutes to the S-D interaction energy in Ni3Al. As another possibility that TM solutes may contribute differently from B-subgroup ones to the macroscopic property of Ni, the (100) surface segregation of solute atoms in Ni is discussed.
The Dissociation of Sessile Superdislocations at a Coherent Twin Eoundary in Ordered CU3AU During Plastic Deformation
Authors: Tichelaar F.D. , Schapink F.W. 
Published: March 2011

AbstractThe glide behaviour of superdislocations at a coherent twin boundary in ordered Cu3Au was examined in a transmission electron microscope for the case when the superdislocations are sessile in the boundary. Possible schemes for dissociation of a superdislocation in the boundary were analysed geometrically. The leading superpartial of each superdislocation dissociated into a superpartial in the matrix and a residual Shockley partial in the boundary of glissile type. The trailing superpartial remained undissociated in the boundary. The superpartial in the matrix glided on a cube plane, and a ribbon of APB connected to the boundary was left in its trail. The cube slip occurs as a result of (i) a maximal resolved shear stress for the observed slip system and (ii) the geometric criteria for slip applied to all possible slip systems in the matrix. The Schmid factors for the slip systems in the matrix could be calculated by assuming a uniform tensile axis in the foil. The tensile axis was deduced from the observed slip systems in the twin.
Design of Li2 -Type Ni3 Si Intermetallics
Authors: Takasugi T. , Izumi O. 
Published: March 2011

AbstractBased on the alloying method to improve the intergranular cohesion of LI2 alloys, it was shown that the Ni3 Si alloy was ductilized by the addition of Ti element and the control of stoicliometry. Metallographic and structural observations in the alloys along Ni3Si-Ni 3 Ti section were performed on optical microscopy, X-ray diffraction, TEM and ALCHEMI. It was shown that Ti element with a solubility of about 11 at.% substituted for the Si sites and the Ni3 (Si,Ti) alloys were highly ordered. The mechanical properties and fracture behavior of Ni3 (Si,Ti) polycrystals were investigated in terms of composition, the environmental effect, test temperature and the doping of B, C and Be. At ambient temperatures, higher ductility accompanied by a high portion of transgranular fractures was observed in the alloys with higher Ti and Ni contents, doped with B and C, and tested in vacuum. Hydrogen and oxygen from environment strongly affected the ductility and fracture of these alloys at ambient and elevated temperatures, respectively. The yield stress increased with increasing Ti content.
The Influence of Interstitial Alloying Elements on the Phase Stability and Fracture Toughness of V3Au
Authors: Kassem M. A. , Fahmy Y. , Koch C. C. 
Published: March 2011

AbstractAdditions of the interstitial elements oxygen and carbon to the A15 structure V3Au intermetallic compound resulted in the formation of the L'2 perovskite structure. The composition of the L'12 phase is about 17.5 at.% oxygen. Analysis of x-ray diffraction line intensities indicated that the interstitial stabilized phase was L'12 perovskite structure rather than the L12, Cu3Au structure type. The microhardness of the L'12 phase is about 20% lower than that of the A15 phase and its fracture toughness is 2 to 3.5 times greater. The mechanism for the improved fracture toughness in the L'12 phase is the subject of continued research.
Characterization of the Effect of Cr Additions to TiAl-Base Alloys
Authors: Huang Shyh-Chin , Hall Ernest L. 
Published: March 2011

AbstractTernary TiAl-base alloys containing Cr have been studied, using rapidsolidification processed materials. The mechanical behavior has been characterized and related to other results on microstructure, site occupancy, phase stability, and deformation mode. It was found that Cr additions enhance the plasticity of duplex γ+a2 alloys, but not single-phase alloys. The ductilization effect of Cr is partially due to its ability to occupy Al lattice sites and modify the Ti-Al bond. It is also partially due to its ability to promote twin formation, by modifying the Al partitioning and therefore the a2/γ volume ratio in transformed regions.
Alloy Phase Stability Requirements in Single Crystal Superalloys
Authors: Duhl David N. 
Published: March 2011

AbstractAlloy phase stability is a critical parameter in the design and implementation of nickel-base superalloys. To achieve the high temperature properties required of single crystal superalloys for application in gas turbine machinery, these alloys must have a stable gamma plus gamma prime microstructure for long periods of time at elevated temperatures. Significant deviation from this stable two phase microstructure, due to the precipitation of other phases, results in the loss of critical alloy properties which can have a deleterious impact on engine performance.Empirical methods based on the electron vacancy concept, commonly employed to predict and prevent the formation of undesirable topologically close packed (TCP) phases such as sigma or mu in polycrystalline nickelbase superalloys, are also used with single crystal superalloys. These undesirable phases result in the loss of alloy properties primarily as a result of the depletion of refractory strengthening elements from the superalloy matrix. The consequence of the formation of undesirable TCP phases on alloy properties and subsequent single crystal component behavior is reviewed.
Decomposition of Quasicrystalline Phase in a Rapidly Solidified Ai-Fe-V-Si Alloy
Authors: Park W. J. , Ahn S. , Kim N.J. 
Published: March 2011

AbstractDecomposition of quasicrystalline phase formed in a rapidly solidified Al-Fe-V-Si alloy has been studied by TEM. The as-cast microstructure varies through the thickness of melt-spun ribbon; microeutectic precipitation of the bcc silicide near the wheel side, formation of globular quasicrystalline icosahedral phase with the microeutectic silicide phase at the middle of the ribbon, and the decomposition of quasicrystalline phase near the air side of the ribbon. During heating, as observed by annealing studies and by in-situ TEM studies, quasicrystalline phase decomposes into various phases such as aluminum, silicide and other unidentified phases. It has been shown that the preferential sites for the transformation are either at the center of quasicrystalline particles or at the quasicrystal/matrix interface, depending on the location of quasicrystalline particles.
Full Potential Lmto Study of Tial Alloy
Authors: Khowash Pradeep K. , Price David L. , Cooper Bernard R. 
Published: March 2011

AbstractWe have used a full potential all electron LMTO total energy calculation with a true interstitial to establish a baseline understanding of pure γ-TiAl. The c and a lattice parameters, Bulk modulus and the Young's modulus are calculated and found to be in excellent agreement with reported experimental values.
Magnetic and Chemical Ordering in the NiPt and the CoPt Systems
Authors: Sanchez J.M. , MorÁn-LÓpez J.L. , Cadeville M.C. 
Published: March 2011

AbstractThe interplay between atomic ordering and magnetism in the NiPt and the CoPt systems is investigated theoretically and experimentally. The complete equilibrium phase diagrams are calculated within the framework of statistical models and are compared with experimental data. Experimental results for the Curie temperature, magnetization and paramagnetic susceptibility in ordered and disordered states are satisfactorily reproduced by a Hamiltonian that contains chemical and short-range order dependent magnetic interactions.
Low Temperature Deposited High Quality ITO Films Prepared by E-Beam Evaporation
Authors: Chang C. S. , Wang J. C. , Kuo L. C. 
Published: March 2011

AbstractAn electron beam evaporation method has been used to prepare tin doped indium oxide (ITO) films with 95 wt.% In2O3 and 5 wt.% SnO2 in an oxygen atmosphere. It was found that the deposition rate and oxygen pressure strongly influence the film properties when the substrate temperature was lower than 200°C. In an optimal condition, highly transparent (transmittance ˜ 90% at wavelength 570 nm) and conductive (resistivity – 3×10−4Ω-cm) films of thickness around 2000 Å at substrate temperature as low as 180°C can be obtained.
Morphology of E-Beam Evaporated Cr Thin Films
Authors: Cheng Y. , Stearns M. B. , Smith David J. 
Published: March 2011

AbstractStudies were made of the structural dependence on the growth rate and substrate temperature of Cr thin films prepared by e-beam evaporation. The d-spacings and the average size of the crystallites were determined from large angle x-ray scattering spectra. Detailed studies of the morphology were made by cross-sectional high resolution transmission electron microscopy.
Sxes Study of Transition Metal Silicide Films and their Contacts to Semiconductors
Authors: Watabe H. , Iwami M. , Hirai M. , Kusaka M. , Kubota M. , Nakamura H. , Kawai M. , Soezima H. , Akao F. 
Published: March 2011

AbstractSpectra obtained by a new soft x-ray emission spectroscopy(SXES) apparatus again exhibited clear differences among Si-compounds and Si crystal. A non-destructive analysis of an annealed transition metal(TMSi:film)/Si(111) contact system was carried out using either the distinct differences of Si L2, 3 SXES spectra between TMSi's and Si single crystals or the fad that the soft x-ray production depth increases in a solid with the energy of the primary electron, Ep. It was shown that the apparatus was capable of exploring electronic and atomic structures of a multi-layered contact system grown on a Si(111) substrate.
Investigation into the Thin-Film Fabrication of Intermetallic NiTi
Authors: Jardine A. Peter , Zhang Hong , Wasielesky Lysa D. 
Published: March 2011

AbstractThin-films of Ni and Ti were formed by sputter co-deposition of Ni and Ti onto amorphous SiO2 and single crystal NaCl and Sapphire substrates. Films were characterized as follows: a) The chemical composition of the films was analysed by EDAX b) The gross morphology was examined by Scanning Electron Microscopy. c) The crystal phases were indentified by X-ray diffraction and Electron diffraction. Intermetallic NiTi has been identified in samples annealed in vacuo at 850°C. Annealing at 500°C in vacuum produced chemical separation of the Ni and Ti. This effect may be due to a narrow solidus region for the existence of NiTi and inhomogeneities due to uneven deposition of the Ni and Ti.
Chemical Vapor Deposition of Copper From Metal-Organic Copper(I) Phosphine Complexes
Authors: Shin H.-K. , Hampden-Smith M.J. , Kodas T.T. , Duesler E.N. , Farr J.D. , Paffett M. 
Published: March 2011

AbstractA series of new, molecular copper(I) compounds with the general formula (β-diketonate)Cu(PMe3) have been prepared which are specifically designed as precursors for the CVD of copper. These species have been designed such that the effects of systematic ligand variations on the CVD process can be examined. The series of derivatives where β-diketonate is one of hexafluoroacetylacetonate, 3, trifluoroacetylacetonate, 4, or acetylacetonate, 5, have been prepared in high yield and are described here. A solid state X-ray diffraction study of 3 reveals that it is monomeric. Cryoscopic molecular weight determination and gas phase FTIR spectroscopy are also consistent with a monomeric structure in liquid and gas phases. Hot-wall CVD of copper from these precursors has been examined under various conditions. Auger electron spectroscopy indicates that the films all exhibit some degree of carbon contamination, but little contamination by oxygen, fluorine or phosphorus.
Decagonal Al3Pd Phase Formation in Lateral and Conventional Thin Film Al/Pd Diffusion Couples.
Authors: Blanpain B. , Mayer J.W. 
Published: March 2011

AbstractWe show that the decagonal Al3Pd phase can be formed by solid state reaction in lateral and conventional thin film couples of Al and Pd. The metastable decagonal phase forms after the initial growth of the Al3Pd2 compound.