bluuebunny/crossref_metadata_2025_split huggingface dataset:
Annealing of Pb-Implanted SrTiO3 in The Presence of Water Vapour: A Study Using D218O Labelling
Authors: McCallum J. C. , Simpson T. W. , Mitchell I. V. , Rankin J. , Boatner L. A. 
Published: March 2011

ABSTRACTWe report new measurements of the regrowth behaviour of Pb-implanted SrTiO3 crystals in the presence of water vapour. Doubly labelled water vapour, D218O, at greater than 95% enrichment in each isotope has been added to the annealing ambient and depth profiles of D and 18O have been obtained from the regrown crystals using secondary ion mass spectrometry (SIMS). The D and 18O content has also been measured by nuclear reaction analysis (NRA) using the reactions D(3He,p)4 He and 18O(p,α)15 N. The crystals were regrown in a conventional furnace under a controlled gas ambient and time-resolved optical reflectivity (TRR) was used to dynamically monitor the regrowth rate during the anneal. An enhancement of the solid-phase epitaxial regrowth rate is observed when water vapour is added to the annealing ambient. This rate increase is accompanied by incorporation of D throughout the regrown layer. 18O is incorporated into the lattice but does not appear to penetrate deep enough to influence the regrowth rate.
Examination of Ion Beam-Target Angle Effects by Optical Spectroscopic Profiling
Authors: Klein J. D. , Yen A. 
Published: March 2011

ABSTRACTThe optical emission spectra resulting from ion beam sputtering a SrTiO3 target were observed as a function of position. A collimated optical fiber bundle parallel to the plane of die sputter target was translated vertically and horizontally to spectroscopically profile the sputter process. Three different angles of incidence of the beam to die target were examined for evidence of bombardment of candidate substrate positions by undesirable species. When the ion beam was at normal incidence to the target or 22.5* from normal incidence the Ar and O contours were of similar shape. However, when die target was inclined at an angle of 45* to die incident ion beam die O contours deviated markedly. Under these conditions it appears that there is a substantial oxygen flux in a direction normal to die target surface. Under these conditions die placement of a substrate facing die sputter target would probably result in undesirable bombardment of die growing film by energetic oxygen.
Irradiation Damage in Zr3 Fe
Authors: Hove L. M. , Rainville M. H. , Phillips D. 
Published: March 2011

ABSTRACTIon bombardments, transmission-electron-microscopy (TEM) and analytical-electron-microscopy (AEM) techniques were used to obtain information on the effect of irradiation on the phase stability of Zr3 Fe, which has an orthorhombic crystal structure. Irradiations were performed at 35–773 K using 0.5–1.5 MeV 40Ar ions and at 40 K using 15–120 keV 209Bi ions.At low ion fluences (1011–1013 ions cm−2), most of the visible damaged regions (∼1.0–5.0 nm diameter) exhibited strong structure-factor contrast features and it is believed that they are probably amorphous. With increasing ion energy, multiple damaged regions were observed to form within individual collision cascades, and the fraction of the theoretical cascade volume occupied by these heavily-damaged regions decreased rapidly. Irradiations at higher ion fluences showed that an irradiation-induced phase change from the crystalline-to-amorphous state occurred at 35–573 K, but not above 623 K. The effect of varying the ion flux was also investigated. The results showed that the fluence required to amorphize a given fraction of the irradiated volume was quite dependent upon the amount of annealing that occurred within the collision cascade at the temperature of the bombardment. The crystalline-to-amorphous transformation appeared to be the result of direct amorphization within the collision cascades and a critical defect concentration being reached in the cascade overlap regions, thus producing additional amorphous regions.
Implantation of Nitrogen into Ti/Al, Ni/Ti, and Ni/Al Bilayers
Authors: Boerma D. O. , Corts T. 
Published: March 2011

ABSTRACTTi/Al, Ni/Ti, and Ni/Al bilayers were produced by evaporation on a Si substrate. The thicknesses of the composing layers were in the 50–200 nm range. The as-evaporated bilayers were implanted with doses of 0.4–2.5 · 1017 of 15N ions/cm2. The 15N energy was chosen so that the calculated projected range was either in the middle of the top Ni layer, or coincided with the interface between the metal layers. The implantation temperature was varied in the range from 25 °C to 245 °C. The 15N depth profiles as measured with nuclear reaction analysis (NRA) were found to have the expected Gaussian shape for the Ti/Al bilayers. However, in the Ni/Ti and Ni/Al layers very asymmetric 15N profiles were observed, with a major fraction of N atoms in the Ti or Al layer, and a minor fraction in the Ni layer. The N concentrations in the Al or Ti layers were found to be almost constant. A massive redistribution of N atoms must have taken place in all three metals during the implantations, to form the observed profiles. We speculate that this remarkable phenomenon, which occurs even below 80°C, can be explained by interstitial diffusion of N atoms and subsequent trapping in Ti or Al, which have a high chemical affinity for nitrogen. The N atoms remaining in the Ni layer after implantation were found to migrate out of this layer during annealing at temperatures ≥250°C.
Molecular Dynamics Simulations of Low Energy Displacement Cascades in the Ordered Compound CuTi
Authors: Zhu H. , Lam N. Q. , Devanathan R. , Sabochick M. J. 
Published: March 2011

ABSTRACTThe properties of low-energy (≤500 eV) displacement cascades in the ordered intermetallic compound CuTi have been investigated by molecular dynamics simulations in conjunction with recently-developed embedded-atom potentials. Various aspects of the time evolution of cascades produced by Cu and Ti primary knock-on atoms have been considered, including the dynamics of Frenkel-pair production, generation of ‘pure’ replacements and anti-site defects, and the anisotropy of the threshold energy for displacement. The spatial distributions of Frenkel defects and the damage function have been analyzed, based on information obtained from various simulated events corresponding to different recoil directions.
Solid Phase Epitaxial Regrowth of Implantation Amorphized Si0.7Ge0.3 Grown on (100) Silicon
Authors: Lee C. , Jones K. S. 
Published: March 2011

ABSTRACTThe solid phase epitaxial regrowth (SPER) process of implantation amorphized Si0.7Ge0.3 layers (850± Å thick) grown on (100) Si has been studied by cross-sectional transmission electron microscopy. For amorphous layers produced by 40 Ar+ implantation highly defective three dimensional regrowth was observed in both Si0.7Ge0.3 and Si. Stacking faults were the principle defect formed of both materials during regrowth. SPER after amorphization via 73 Ge+ implantation was also investigated. It was found that the SPER velocity of the 73 Ge+ implanted Si0.7 Ge0.7 Ge0.3 was about twice the velocity of the 40 Ar+ implanted samples; for 73 Ge+ implanted Si it was about three times that of the 40Ar+ implanted samples. The activation energy for SPER in 40Ar+ and in 73 Ge+ implanted Si0.7 Geo0.3 was about 1.6 and 2.6 eV, respectively. The defect density was significantly reduced in 73 Ge+ amorphized Si but not in the 73 Ge+ amorphized Si0.7 Ge0.3. It is proposed that limited Ar solubility inhibits high quality regrowth in both SiGe and Si. Upon 73 Ge+ amorphization and solid phase epitaxy the interfacial strain between the SiGe and Si cannot be accommodated. Thus the epitaxial process is poor in these SiGe strained layers regardless of the amorphizing species.
Excimer Laser Irradiation of Metallic Films on Ceramic Substrates
Authors: Godbole M. J. , Pedraza A. J. , Lowndes D. H. , Thompson J. R. 
Published: March 2011

ABSTRACTCopper films sputter deposited on mechanically polished (optical finish) and on annealed substrates were laser-irradiated at various energy densities. The effect of the substrate condition on both the evaporation threshold and the morphology of the laser-irradiated metallic films was investigated. The energy density threshold for laser-induced evaporation of the copper films was studied using energy dispersive x-ray spectroscopy (EDS) in a scanning electron microscope (SEM). It was found that for annealed substrates the energy density threshold decreases relative to the threshold for the as-polished condition. These results are compared with predictions of a mathematical model that assumes that the near surface region of the as-polished ceramic is a highly damaged region and, thus, constitutes a thermal barrier. The film remains intact and with almost no change in morphology after laser irradiation at energy densities lower than 0.80 J/cm2 if the substrate has been previously annealed. On the other hand, copper films deposited on as-polished substrates break up during laser processing forming copper islands.
High-Resolution Transmission Electron Microscope Study of Electron-Beam Induced Damage in some Oxide Superconductors
Authors: Matsui Yoshio , Yanagisawa Kasumi 
Published: March 2011

ABSTRACTElectron-beam induced damage of some oxide superconductors is examined by high-resolution transmission electron microscopy (HRTEM), using both 1 MV high-voltage machine and conventional 200kV one. By 1 MV electron beam, both YBa2Cu4Oy and Y2Ba4Cu7Oy suffer from amorphization due to knock-on effects which is initiated at (CuO)2 double-chain sites. By 200kV beam, some of the double-chains decompose into the single-chains and precipitation of CuO crystal is induced, due to thermal heating effects. Both Bi- and Pb-based superconductors, on the other hand, suffer from amorphizations at both 1MV and 200kV. The materials relating to La2CuO4, for instance the T*-type of superconductor (Nd, Sr, Ce)2CuO4, never amorphize even by irradiations of 1000kV electron beam. These results suggest that it is possible to introduce defects or precipitates to control the microstructures of superconductors by means of electron beam irradiations.
Thermal Neutron Irradiation and Large Pinning Enhancement in Superconducting Materials
Authors: Zhao Y. J. , Liu J. R. , Meng R. L. , Hor P. H. , Chu W. K. 
Published: March 2011

ABSTRACTUp to 25 times enhancement of magnetic critical current density has been observed at 70 K and 2500 O for 3% 6Li-doped sintered YBCO sample irradiated with thermal neutrons at a dose of 1 × 1018 n/cm2. High energy reaction product of 6Li and thermal neutron, the 2.73 MeV 3H and 2.05 MeV 4He produced uniform damage throughout the bulk sample. The strong field dependence of the Jc enhancement points to the weak center nature of the radiation defects. The upper critical field of this weak center decreases with temperature, and is about 800, 300, 150 Oe at 30, 50, 70 K respectively.
Non-Linear and Time-Dependent Diffusion of Gold in Amorphous Silicon.
Authors: Wagner A. V. , Wu D. T. , Spaepen F. 
Published: March 2011

ABSTRACTBy performing scaling experiments [1] and examining the evolution of the spatial second moment of the concentration profile, it was shown that the diffusion coefficient of gold in amorphous silicon is both concentration and time dependent. The second moment curves for different temperature anneals can be scaled to a master curve using a factor with an activation enthalpy of 2.0 eV.
Magnetic Field Dependence of Jc in A T1–1223 Wire; Presence of Pinning and Good Grain Boundary Connectivity.
Authors: Doi Toshiya J. , Nabatame Toshihide , Okada Michiya , Yuasa Toyotaka , Tanaka Kazuhide , Inoue Naomi , Soeta Atsuko , Aihara Katsuzo , Kamo Tomoichi , Shin-Peimatsuda  
Published: March 2011

ABSTRACTThe existence of effective pinning in single T1-layer 1223 superconductors has been reported [1–3], as opposed to lower values in T1- and Bi-double layer systems, which is intimately related to their crystal structures. In order to investigate the possibility of T1–1223 being applied as a practical superconductor, tape shaped wires of the chemical composition (T10.5Pb0.51 (Sr0.8Ba0.2Ca2Cu3O9were prepared. Transport Jc of T1–1223 was measured to be 1.8 × 104 A/cm2 at 77K in the absence of a magnetic field. These results seem to imply that T1–1223 has, not only effective pinning because of having a more 3-dimensional vortex line lattice like YBa2Cu3O7, but also better grain boundary weak-link performance than YBa2Cu3O7. PresenT1y it appears that T1–1223 may be a superior choice to make better superconducting wire, because of these considerations and of the higher Tc of 120K.(T10.5Pb0.5)1Sr2CaCu2O7 (T1–1212) also seems to have effective pinning, as well as T1–1223, supporting the idea that shorter Cu-O plane spacing, or absence of thicker insulating region such as T12O2 or Bi2O2 double layer, are beneficial for effective pinning through facilitating a better 3D-like vortex line lattice [4, 5]. Our “1212” and “1223” samples are good counter examples to the 2D pancake-like vortex theory [6, 7].
Trapped Magnetic Field in Proton Irradiated Melt-Textured Y-Ba-Cu-O Superconductors
Authors: Chen In-Gann , Liu Jianxiong , Weinstein Roy 
Published: March 2011

ABSTRACTThe trapped magnetic fields in high energy proton irradiated melt-textured Y-Ba-Cu-O (MT-Y123) high temperature superconductors (HTS) materials have been studied. Prototype of mini-magnet, about 1 cm3 which retains about 14, 200 G @ 77 K, has been made with these proton irradiated samples. Quasi-persistent magnetic field near 3 to 5 Tesla in liquid nitrogen is feasible with our current MT-Y123 samples. Two types of motors have been tested successfully by replacing metallic permanent magnet with the trapped field in MT-Y123 samples.The trapped magnetic field mapping technique is used to study the superconducting properties of the MT-Y123 materials. Granular structures in MT-Y123 samples can be observed directly by the field mapping method. A phenomenological current model has been developed to account for the trapped field intensity and profile in HTS samples. The trapped field can be reproduced very well by this model. Remenant magnetic moment trapped by MT-Y123 samples measured by this mapping method and by standard VSM will be discussed. The effect of high energy proton (160–210 MeV) bombardment on the field trapping capability and stability will be discussed.
Irradiation Effect of Slow Neutrons on Mechanical Behaviour Related to Flux Pinning In YBa2Cu3Oy
Authors: Zhu J. S. , Li J. , Wang Y. N. , Jin J. R. , Gu M. , Ding S. Y. , Jin X. , Fung P. C. W. , Liu Z. M. 
Published: March 2011

ABSTRACTInternal friction and modulus in YBa2Cu3Oy, which are related to flux pinning, were examined by means of the vibrating reed technique before and after the slow neutron irradiation to different fluences. Both the decrease of mechanical dissipation and the increase of the modulus associated with strongly enhanced flux pinning were observed in a sample irradiated up to a suitable fluence. However, a decrease of modulus and magnetic hysteresis loop was found after further irradiation. A change in the microstructure of the irradiated material is used to explain the observed phenomena.
Orientation Dependence of Flux Pinning in a Layered Bi2Sr2 Ca1 Cu2O8 + 10% Ag Composite
Authors: Foldeaki Maria , Ledbetter Hassel 
Published: March 2011

ABSTRACTThe Bi2 Sr2 Ca1 Cu2 O8 + 10% Ag specimen was grain oriented along the a(b) axis, but random in the perpendicular plane. Magnetic susceptibility and hysteresis measured along the axis of grain orientation and in the polycrystalline direction showed remarkable anisotropy. At low temperatures (below about 30 K), hysteresis curves were compatible with the strong-pinning model. The pinning force calculated from the hysteresis loop showed a higher maximum in the random direction, but decreased fast with increasing field and temperature. From the zero-field-cooled (zfc) and field-cooled (fc) susceptibility curves, the irreversibility line T*(H*) was determined. Evaluation according to the de Almeida-Thouless equation with fixed exponent n=3/2 revealed a two-phase vortex structure; one nearly isotropic with low (40-$K) zero-field irreversibility transition temperature, and one strongly anisotropic, the irreversibility transition being close to the superconducting-transition temperature.
In Situ TEM Observation of Defects and Amorphous Phase in Si Wafer During Ion Implantation
Authors: Shigenaka Naoto , Hashimoto Tuneyuki , Fuse Motomasa , Owada Nobuo , Yamaguchi Hizuru , Ozono Seiko 
Published: March 2011

ABSTRACTIn situ TEM observations of defects and. the amorphous phase in Si wafer during 150 keV Ar+ ion implantation were made which elucidated their characteristic behavior in Si. Defects introduced by ion implantation were eliminated by amorphous phase formation and then new defects did not form in the amorphous phase. Microstructural evolution in Si wafers under high dose implantation (2E16 ions/cm2) of 400 keV Si* ions was also investigated at temperatures of -70, -30, 20, 100 and 200 °C using a cross-section 1 TEM observation technique. At temperature of 20 °C and above, a defect layer was formed in each specimen, and the defect density was observed to decrease as temperature increased. At temperture of -30 °C and below the amorphous phase was formed and a defect layer which made contact with this phase was also observed. After annealing of these implanted specimens at 850 °C for 20 min, the amorphous phase had crystallized and the defect layer in contact with the amorphous phase was almost eliminated. But another defect layer was formed during annealing in the region where the amorphous phase had existed.
Copper-Carbon Alloy Films by Methane Beam Assisted Epitaxial Copper Deposition
Authors: BROWN David W. , Donovan Edward P. , Cotell Catherine M. , Grabowski Kenneth S. 
Published: March 2011

ABSTRACTCopper-carbon alloy films containing between 7 and 40 at.% carbon, as measured with 6.2 MeV He++ scattering, were deposited by ion beam assisted deposition (IBAD) on pure epitaxial Cu(100) films on Si(100) substrates. The IBAD process involved simultaneous deposition of evaporated copper (0.3 to 2.0 nm/s) and bombardment with 400 eV ions (340 μA/cm2 on target) from a Kaufman ion source fed with methane. Transmission electron microscopy (TEM) showed that an IBAD layer with 15 at.%C was epitaxial with the underlying pure Cu(100) layer. X-ray diffraction (XRD) indicated that the IBAD films were epitaxial at low carbon concentration but polycrystalline at high concentration. The small range of carbon ions in copper and the evidence of sputtering suggest that this loss of epitaxy resulted from increased surface carbon interfering with epitaxy. Although carbon and copper are immiscible, TEM and XRD have revealed no evidence of carbon precipitation, indicating that the carbon may be in solution and that such IBAD layers may be suitable for diamond formation by laser annealing.
Influence of Energy Deposited by Energetic Particle Bombardment on Thin Film Characteristics
Authors: Winters Harold F. , Eckstein W. , Coufal H. J. 
Published: March 2011

ABSTRACTIt has been recognized since the 1960's that bombardment of a growing thin film by energetic particles strongly influences film properties. Particle bombardment has generally been accomplished by accelerating ions into the growing film. However, it has also been recognized since the 1960's that energetic particles reflected from the target influence the characteristics of films grown by physical sputtering and many experiments have been interpreted on this basis. A systematic study of the energy reflected from the surface by normally incident, singly charged noble-gas ions on five substrates of different masses has recently been published. This data along with sputter yields from the literature allow estimates to be made which were previously unavailable. The energy reflected from the target is carried away by electrons, sputtered particles and reflected ions (neutrals). The purpose of this paper is to provide basic information which will allow thin film scientists to estimate the influence of various experimental parameters on the amount of energy arriving at the growing film. The energy reflected from the target per sputtered atom will be given as a function of ion mass, target mass, and ion energy. TRIM.SP Monte Carlo calculations will be used to estimate the ratio of the energy carried away by sputtered atoms to that carried away by reflected ions. Calculations will also be used to estimate the average energy of the sputtered atoms as a function of ion mass, substrate mass and ion energy. It will be shown how this information can be used to guide the adjustment of experimental parameters in sputtering environments so as to control film characteristics.
Simulations of Low-Energy Ion Bombardment and Epitaxial Growth
Authors: Chason E. , Bedrossian P. , Tsao J. Y. , Dodson B. W. , Picraux S. T. 
Published: March 2011

ABSTRACTWe have performed computer simulations of epitaxial growth and low-energy ion bombardment for comparison with reflection high-energy electron diffraction (RHEED) mesurements. The simulations are based on a hybrid Monte Carlo/rate equation approach which includes the processes of defect creation (adatom and surface vacancy), surface diffusion, and attachment and detachment from steps and islands. In this work, we focus on simulating the experimental observations of ion-induced RHEED oscillations and cancellation of RHEED oscillations during simultaneous ion bombardment and growth. For the interaction of the low-energy ion with the surface, we consider two mechanisms: preferential sputtering (where the sputtering cross section depends on the atomic coordination) and mobile vacancies. Our results indicate that the primary interaction of the ion beam with the surface is probably through the creation of mobile vacancies, and that the degree of preferential sputtering is not large.
In Situ Observation of Growing Process of Particles in Silane Plasmas and Their Effects on Amorphous Silicon Deposition
Authors: Shiratani Masaharu , Watanabe Yukio 
Published: March 2011

ABSTRACTIn rf silane plasmas, growing process and behavior of dust particles and presence of negative ions are studied by square-wave-amplitude-modulating an rf discharge voltage. By combining the rf modulation method with Mie scattering methods, particle behavior together with temporal evolutions of particle size and density is revealed. While the rf modulation is effective for the suppression of particle growth, small particles are found to exist still in the discharge space for a larger duty cycle. Further, particles seem to be suspended around an rf electrode by counter balance between an electrostatic force due to time-averaged sheath electric field and a force increasing with particle size. The development of particle growth also affects the rf discharge itself, resulting in inhomogeneity of film properties. Negative ion detection is carried out as a first step for studying whether they cause the particle formation. It is found that negative ions are formed in rf silane discharges even for a low concentration of 0.5%SiH4 and their formation is due to attachment to dissociated radicals rather than dissociative attachment of SiH4.