bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic Properties of YBaCuO Crystal Prepared by Quench and Melt Growth Process
Authors: Murakami Masato , Koyama Noboru 
Published: March 2011

ABSTRACTWe 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

ABSTRACTThe 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

ABSTRACTAs 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

ABSTRACTSince 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

ABSTRACTOne 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

ABSTRACTIon 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

ABSTRACTIon—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

ABSTRACTIon 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

ABSTRACTIon 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

ABSTRACTDuring 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

ABSTRACTThe 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

ABSTRACTPrevious 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

ABSTRACTThe 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

ABSTRACTIon 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

ABSTRACTNon-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

ABSTRACTAfter 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.
Studies on Ion Scattering and Sputtering Processes Relevant to Ion Beam Sputter Deposition of Multicomponent Thin Films
Authors: Auciello O. , Ameen M. S. , Krauss A. R. , Kingon A. I. , Ray M. A. 
Published: March 2011

ABSTRACTResults from computer simulation and experiments on ion scattering and sputtering processes in ion beam sputter deposition of high Tc superconducting and ferroelectric thin films are presented. It is demonstrated that scattering of neutralized ions from the targets can result in undesirable erosion of, and inert gas incorporation in, the growing films, depending on the ion/target atom mass ratio and ion beam angle of incidence/target/substrate geometry. The studies indicate that sputtering by Kr+ or Xe+ ions is preferable to the most commonly used Ar+ ions, since the undesirable phenomena mentioned above are minimized for the first two ions. These results are used to determine optimum sputter deposition geometry and ion beam parameters for growing multicomponent oxide thin films by ion beam sputter-deposition.
Importance of Surface Preparation in Direct Ion Beam Deposition(Ibd)
Authors: Miyake Kiyoshi 
Published: March 2011

ABSTRACTFundamental aspects of direct ion beam deposition (IBD) are discussed, stressing surface preparation and contamination problems. Residual gas contamination, ion beam induced metal contamination, and presence of surface native oxide before deposition are shown to be the major factors hindering low temperature epitaxial growth in IBD.
A low energy hydrogen ion bombardment is demonstrated as an effective surface preparation method to remove surface native oxide in the case of silicon deposition.
Study of the Anodic Oxidation on Ti and Ta6V (Ti6A14V) by Ion-Implanted Xe Ions Markers and O18 Tracing Techniques
Authors: Chen Heming , Dai Mingjiang , Bai Xinde , Li Wangpei 
Published: March 2011

ABSTRACTThe techniques of single and double layers of implanted Xe ions marker as well as the O18 tracing method are used to study the mechanism of the anodic oxidation of Ti and TA6V (Ti6A14V). It is observed that in 5 wt% ammonium citrate, the mechanism of the anodic oxidation of Ti is very different from that of TA6V. For Ti, new oxide is formed mainly by the migration of Ti cations to the solution/oxide interface and the regions at which new oxide is formed are at the solution/oxide interface and in the pre-oxide near the interface. While for TA6V, anodic film growth is due to the migration of oxygen anions to the oxide/metal interface and the growth regions of new oxide are at the oxide/metal interface and in the pre-oxide near the interface. Transport numbers for Ti oxidized in 1 wt%. KOH are calculated and found to be affected by oxidation temperature, i.e. at 3'C, the average transport number is 0.32, while at 30&00B0;C,it is 0.28. Current efficiencies are above 99.8%. AES spectra show that the distribution profiles of the elements V and Al in anodic film on TA6V are uniform.
Thermodynamic Measurements via Time-Resolved Transient Conductance
Authors: Thompson Michael O. 
Published: March 2011

ABSTRACTRecent applications of the transient conductance technique to measurements of thermodynamic properties of Si are reviewed. The transient conductance measurements provide time-resolved data of the melt and solidification dynamics during pulsed laser irradiation. By studying these dynamics, thermodynamic properties can be measured in time and temperature regimes unaccessible by conventional techniques. Examples discussed include homogeneous nucleation, electrical properties of the supercooled liquid, and the melting temperature of amorphous Si. Homogeneous nucleation occurs at supercoolings of 500 K for quench rates near 1010 K/s, consistent with a liquid/crystal surface energy of 0.34 J/m2. Evidence of transient nucleation effects are observed at quench rates above 2 × 1010 K/s. During supercooling, the temperature dependence of the electrical conductivity of liquid Si was estimated between 1200 and 1800 K with a broad maximum observed near 1450 K. The melting temperature of amorphous Si was determined to be 220 K below the crystal melting temperature with no detectable differences between thermally unrelaxed and relaxed states.
Laser Induced Solid-State Grain Growth in Polysilicon Films
Authors: Ajuria S.A. 
Published: March 2011

ABSTRACTWe report studies done on the heating of polysillcon thin films below the melting temperature with long-time (on the order of minutes) continuous-wave laser irradiations. It is shown that a well controlled steady-state temperature is locally established within the film. A thermal model is developed to correlate film temperature to beam intensity and a direct relationship is found. A correlation coefficient of 2.5 K/W/cm2 is empirically determined between film temperature and incident beam power density.
Femtosecond Laser Melting of Graphite and Diamond
Authors: Reitze D. H. , Ahn H. , Wang X. , Downer M. C. 
Published: March 2011

ABSTRACTFemtosecond time-resolved reflectivity measurements performed on highly oriented pyrolytic graphite (HOPG) and diamond elucidate the nature of the phase transition from solid to liquid carbon. In HOPG, we find that a high-reflectivity phase lasting as long as 10 ps appears when the surface is irradiated with pulse fluences in excess of 0.13 J/cm2, the critical fluence for melting. This transforms within 30 ps into an equilibrium low-reflectivity phase lasting hundreds of ps, similar to behavior observed in picosecond reflectivity experiments. The results suggest the occurrence of a two-step phase transition (graphite -> liquid metal -> liquid insulator) when HOPG is excited above the critical fluence. Similar results are obtained with diamond.
Microstructure, Stress and Electrical Properties of the Highly Stable W/P+-In0.53Ga0.47 as Ohmic Contacts
Authors: Katz A. , Maher D. , Thomas P.M. , Weir B.E. , Dautremont-Smith W.C. , Kimerling L.C. 
Published: March 2011

ABSTRACTNon-alloyed refractory ohmic contacts to P+-ln0.53 Ga0.47 As layer have been fabricated using sputtered W and rapid thermal processing. These contacts showed excellent thermal stability over the temperature range of 300 to 750°C, with an abrupt and almost unreacted metal-semiconductor interface. The W film biaxial stresses were found to be strongly depended on the Ar pressure during the sputter deposition. At low Ar pressures the film were deposited with compressive stress, and became tensile at pressures higher than 7mTorr with a maximum value of about 8×l09 dyne cm2 as a result of Ar deposition pressure of 28mTorr. The W contacts to Zn doped 1×1019 cm−3 In0.53GA0.47 As film was found to be ohmic already as deposited with a minimum specific resistance of about 7.5×10−6 Ωcm−2, achieved as a result of heating at 600°C for about 30 sec.
Interaction Between Implanted Ions and Intrinsic Defects in Silica
Authors: Magruder R.H. , Kinser D.L. , Weeks R.A. , Zuhr R.A. 
Published: March 2011

ABSTRACTHigh purity silica (Spectrosil) samples were implanted with Ti, Cr, Mn, Fe and Cu at doses ranging from 1.0 to 5.0×1015 ions/cm2 at 160 keV and 2.6 μA/cm2. The optical absorption extinction coefficients per ion were measured from 1.8 to 6.0 eV. In all samples there was an increase in absorption over the unimplanted sample at energies ≥4.6 eV. The increase in absorption at 5.1 eV and 5.7 eV is attributed to B2(E”) centers and E’ centers respectively. The relative values of the extinction coefficients of these bands are attributed to the relative oxygen activities of the TMI relative to the SiO2 host substrate.