bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Critical Current Density Enhancement in (Cax Y1−x)Ba2Cu4O8 (1:2:4)
Authors: Narwankar P. K. , Chandrachood M. R. , Fendorf M. , Morris D. E. , Sinha A. P. B. , Gronsky R. 
Published: March 2011

ABSTRACTSamples with the stoichiometry (CaxY1−x)Ba2Cu4O8, x = 0, 0.1 were synthesized at P(O2) = 25 and 200 bar. High Resolution TEM images for the samples synthesized at 25 bar show a high density of planar defects as compared to almost defect free microstructure of Ca0.1Y0.9Ba2Cu4O8 synthesized at 200 bar. The intragrain critical current density of the high defect density samples is however about 100 times lower that that of Ca0.1Y0.9Ba2Cu4O8 synthesized at P(O2) = 200 bar.
Weak Pinning Centers in Proton Irradiated YBCO Single Crystals
Authors: Zhao Y. J. , Liu J. R. , Tao Y. K. , Hor P. H. , Chu W. K. 
Published: March 2011

ABSTRACTObserved magnetic Jc enhancement in a 3.4 MeV proton-irradiated Y1Ba2Cu3O7-δ (YBCO) single crystal are shown to be intimately linked with a kind of weak pinning centers. Applied magnetic field transforms weak centers into the normal state or pinning centers, which then cause pinning enhancement. Strong pinning anisotropy of the radiation induced weak center can be explained very well by the size anisotropy of a superconducting unit cell and a flux line, or the coherence length.
Enhancement of Pinning Energy and Critical Current Density in Tl2CaBa2Cu2O8 Films by Proton Irradiation
Authors: Reeves M. E. , Weaver B. D. , Summers G. P. , Soulen R. J. , Olson W. L. , Eddy M. M. , James T. W. , Smith E. J. 
Published: March 2011

ABSTRACTMeasurements are presented which show the effect of proton irradiation on the irreversibility line and critical current in Tl2 CaBa2Cu2O8 thin films. These data show that the irreversibility line is dependent on the defect structure and that the pinning energy is increased by proton irradiation. This leads to an increase in the critical current density at 60 K for the lowest radiation dose. Further irradiation reduces the critical current, even while the irreversibility line is enhanced.
Ion Beam Assisted Deposition of Cubic Boron Nitride Thin Films
Authors: Kester Daniel J. , Messier Russell 
Published: March 2011

ABSTRACTBoron nitride thin films were grown using ion beam assisted deposition. Boron metal was evaporated, and the depositing film was bombarded by nitrogen and argon ions. The films were characterized using Fourier transform infrared spectroscopy, electron diffraction, transmission electron microscopy, and Rutherford backscattering. The thin films were found to be cubic boron nitride, consisting of 100–200 Å crystallites with a small amount of an amorphous secondary phase. The best conditions for depositing cubic boron nitride were found to be a substrate temperature of 400°C, bombardment by a 50:50 mixture of argon and nitrogen with a bombarding ion energy of 500 eV and a ratio of bombarding ions to depositing boron atoms of from 1.0 to 1.5 ions per atom.
Derelaxation of Amorphous Silicon by Ion Implantation: Optical Characterization
Authors: Reitano R. , Grimaldi M. G. , Baeri P. , Bellandi E. , Borghesi A. , Baratta G. 
Published: March 2011

ABSTRACTThe transition between relaxed and unrelaxed amorphous silicon can be obtained by thermal treatment of the unrelaxed amorphous or by low dose ion irradiation of the relaxed material. In both cases a variation in the short range order has been invoked to explain the behavior of the structural changes probed by various techniques. In this work we study the influence of such changes on the optical properties of a-Si in the region of the transition between the relaxed and the unrelaxed states. We show that a progressive variation of the optical constant in the visible-near infrared region upon derelaxation occurs. Therefore, significant modifications of the electron density of state in the region above the optical gap are associated with the changes in the short range order probed by Raman spectroscopy.
Hydrogen in Dielectric Film Formation From an Electron Cyclotron Resonance Plasma
Authors: Barbour J. C. , Stein H. J. 
Published: March 2011

ABSTRACTThe incorporation of hydrogen into silicon nitride films grown downstream from an electron cyclotron resonance (ECR) plasma decreased rapidly with increasing substrate temperature (100–600°C). Fourier transform infra-red (FTIR) spectroscopy showed that the hydrogen in the as-grown material was primarily bonded to nitrogen. However, an applied bias of -200 V caused an increase in the number of Si-H bonds relative to N-H bonds, as a result of increased ion-beam damage. In addition, ion irradiation of an as-grown film with 175 keV Ar+ at room temperature showed that H transferred from N-H bonds to Si-H bonds without a loss of H. Elastic recoil detection (ERD) and FTIR of thermally annealed films showed that the stability of H incorporated during deposition increased with deposition temperature, and that the N-H bond was more stable than the Si-H bond above 700°C. Deuterium plasma treatments, at 600°C, of annealed films caused isotopic substitution with a conservation of bonds. Therefore, hydrogen loss from annealed films is apparently accompanied by a reduction in dangling bonds.
Characterization of the Depositing Flux in Laser Ablation Deposition (LAD).
Authors: Kools Jacques C.S. , Dieleman Jan 
Published: March 2011

ABSTRACTAngular-resolved time-of-flight (ARTOF) studies have been performed on ablation plumes of copper generated by excimer laser fluences just above threshold in vacuum. Positive ions, Rydberg atoms and ground-state neutrals are observed. Relative concentrations, angular intensity distributions and angular-resolved velocity distributions are measured for ground state neutrals and ions.Ions have the highest kinetic energies ( 20–80 eV). Their angular distribution is isotropic. Their concentration at the substrate is very low ( ≤ 10−6). Ground state neutrals have lower energies ( ≈ 1 eV). Their intensity and velocity is a strongly decreasing function of the polar angle. Rydberg-atoms have energies in between those of ground-state neutrals and ions. Their angular distribution is also dependent on the polar angle.The concentration, kinetic energy and angular distribution of the ionised species arc very well explained by a mechanism of thermal ionization and subsequent space-charge induced repulsion. The velocity distributions and angular intensity distributions of the ground-state neutrals are quantitatively predicted by a model for the flow dynamics of pulsed laser generated gas clouds.
1N-SITU Ellipsometry Study of Pulsed Laser Deposited ZnO Films
Authors: Pittal Shakil , McConville L. A. , Ianno N. J. , Snyder P. G. 
Published: March 2011

ABSTRACTEllipsometry is normally used to characterize layered structures that have uniform properties laterally across the area of the probe beam. In this study, pulsed laser deposition of ZnO films was found to have highly nonuniform growth properties in the lateral directions. We were able to account for the effects of the nonuniform growth on in-situ ellipsometric data, by considering two dynamic growth models.
Effects of Processing Parameters on KrF Excimer Laser Ablation Deposited ZrO2 Films
Authors: Smith Gary A. , Chen Li-Chyong , Chuang Mei-Chen 
Published: March 2011

ABSTRACTSystematic experiments have been carried out to characterize the yttria containing zirconia thin films on sapphire substrates by 248nm KrF excimer laser ablation. The deposition rate as a function of laser fluence and O2 pressure at room temperature was measured with a quartz crystal microbalance. The results show different threshold fluences for deposition in vacuum vs. oxygen. While the deposition rate increases with increasing fluence at a given oxygen pressure, the rate eventually saturates at a higher laser fluence. At a given fluence, the oxygen pressure dependence of the deposition rate shows a radical reduction when the O2 pressure increases from 10 mTorr to 1 Torr. Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy were used to obtain stoichiometric information. A very strong pressure dependence of the O/Zr ratio was observed. While the trend of increasing O/Zr and Zr/Y ratio with increasing O2 pressure is apparent, the correlations between O/Zr as well as Zr/Y ratio and other processing conditions are less obvious. RBS results indicate an increasing roughness at the interface between the ZrO2 film and the sapphire substrate as the oxygen pressure exceeds 50 mTorr. The structural information obtained from x-ray diffraction patterns indicates broadening of peak width with increasing laser fluence as well as decreasing substrate temperature. For the film deposited at a lower substrate temperature, a strong (002) texture was observed.
Processing of Y1Ba2Cu3O7−x Superconducting Thin Films on GaAs Substrates with Double Buffer Layers
Authors: Lee Sang Yeol , Jia Quanxi , Anderson Wayne A. , Shaw David T. 
Published: March 2011

ABSTRACTHigh temperature superconducting Y1Ba2Cu3O7−x(YBCO) thin films have been grown on GaAs substrates by in situ laser deposition with a double buffer layer of yttrium-stabilized ZrO2(YSZ)/Si3N4. A barrier layer using a combination of YSZ/Si3N4 was used to grow high quality YBCO thin films without the degradation of the GaAs during YBCO film deposition. Strongly c-axis oriented superconducting YBCO thin films with a zero resistance temperature of 85.5 K and a critical current density of 1.9×103 A/cm2 at 77 K have been obtained. The electrical properties of the YBCO thin films were mainly dependent on YSZ buffer layer deposition condition.
Pulsed Laser-Induced Amorphization of Silicon Films
Authors: Sameshima T. , Usui S. 
Published: March 2011

ABSTRACTAmorphization of silicon films occurred through homogeneous solidification of molten silicon layers on quartz substrates induced by irradiation with a 30ns-XeCl excimer laser. The crystalline nucleation rate was obtained to be 8×1030m−3s−1. Silicon films were completely amorphized for films thinner than 18nm. Complete amorphizatoin is brought about by reduced grain size and reduced recalescence as the film thickness decreases. Recalescence was observed in situusing transient thermometry with a platinum-temperature-sensing layer when a 15nm-thick silicon film was amorphized.
Buried Quantum Well Structure Fabricated by in Situ EB Lithography
Authors: Kawanishi H. , Sugimoto Y. , Ishikawa T. , Tanaka N. , Hidaka H. 
Published: March 2011

AbstractBuried quantum well structures have been fabricated in GaAs/AIGaAs system using an in situ lithography process. The process utilizes an ultrathin oxide layer formed in situ on a GaAs surface as a mask against Cl2 gas etching. An electron beam (EB)-induced Cl2 gas etching is used to locally remove the oxide mask for positive-type lithography. For negativetype lithography, the oxide mask is selectively formed on a GaAs surface by EB-stimulated oxidation. Subsequent Cl2 gas etching results in the formation of isolated quantum wells. After removing the oxide mask, overgrowth using molecular beam epitaxy is successfully carried out on the patterned surface. The cathodoluminescence image of the buried quantum well demonstrates the high quality of the resulting structure formed by this “in situ EB lithography” process. The photoluminescence intensity from the quantum well of the processed sample is proved to be the same order of magnitude compared with that from a successively grown sample, showing that the use of the oxide mask causes no serious degradation in the processed interface.
Condensed Chlorine Etching of GaAs Induced by Excimer Laser Radiation
Authors: Freiler M.B. , Shih Ming Chang , Haase G. , Scarmozzino R. , Osgood R.M. 
Published: March 2011

AbstractWe report excimer laser induced etching of GaAs samples covered with a layer of condensed Cl2. The experiments were performed at low temperatures (120-150 K) and in a chlorine ambient (PC12=1-40 mTorr). Spatially well-resolved, anisotropic etching has been demonstrated with an observed etch rate of 0.25 Å/pulse (0.1 μm/min for typical parameters). The etch rate is characterized as a function of the various system parameters (pressure, temperature, laser rep-rate, etc.), and a model is proposed to describe the etching mechanism.
Electron Beam Induced Decomposition of Palladium Acetate
Authors: Stark T.J. , Mayer T.M. , Russell P.E. 
Published: March 2011

AbstractA focused electron beam has been used to selectively decompose sub micron thick films of palladium acetate, Pd(OOCCH3)2, resulting in the formation of <0.1μm wide Pd rich features. Resistivity of the palladium acetate film decreased when exposed to doses above 500μC/cm2. Annealing to 160°C further reduces the resistivity of the exposed areas to as low as 100μΔcm. XPS analysis of the exposed areas indicate that the Pd is reduced to a metallic state and that the ratio of C and 0 to Pd drops to 1.5 and 0.6, respectively, after exposure. Residual gas analysis during exposure indicates that CO2 and CH3 are the primary volatile products of the decomposition.
Ablation of Single Crystal MgO by UV Excimer Irradiation
Authors: Webb R. L. , Jensen L. C. , Langford S. C. , Dickinson J. T. 
Published: March 2011

AbstractThe ablation of single crystal MgO irradiated with 248 nm excimer laser light is studied by means of time resolved spectroscopy and quadrupole mass spectrometry. Luminescence spectra and SEM observations indicate that repeated laser bombardment gradually increases the density of potentially absorbing defects. In polished samples, this progressive growth is preceded by an initial clean-up (reduction) of surface damage. Unlike many wide band gap materials, defect production in MgO by electronic mechanisms is not likely. Chemical etch techniques indicate the presence of high dislocation densities in regions etched by the laser, suggesting that point defect production by dislocation motion is important. The ablation plume is composed of charged particles, including cluster ions, as well as a high density of excited neutrals. The growth of the plume with repeated bombardment correlates with defect formation as indicated by luminescence intensities.
Nanostructure Fabrication: Dry Etching Damage
Authors: Doughty G.F. , Cheung R. , Foad M.A. , Rahman M. , Cameron N.I. , Johnson N.P. , Wang P.D. , Wilkinson C.D.W. 
Published: March 2011

AbstractAlthough the directed energy and chemical reactivity of dry etching permits the fabrication of nanostructures with precise geometries, it also causes unwanted electrical and optical changes to the surface, changes generally referred to as “damage”.This paper discusses the extent and the impact of dry-etching damage on rI-V and I[-VI compound semiconductors as assessed by a very wide range of techniques: the performance of devices such as MESFETs, and measurements of other properties - surface uniformly and precisely, Schottky junction characteristics, cut-off of epitaxial wire conductance, integrated photoluminescence, X-ray reflectivity, DLTS, TEM imaging and Raman scattering.We distinguish an important difference between the nature of damage on sidewalls and on surfaces normal to the directed ions, and report on progress towards establishing a model of the nature of dry etching damage. This model is applied to indicate what kinds of processes are likely to give etching with low damage.
The Synthesis of Metal Oxide Films from Compound Powder Targets
Authors: Stognij A.I. , Tokarev V.V. , Mitin Yu.N. 
Published: March 2011

AbstractThe paper presents the results of AES, SIMS, RBS and electron microscopy investigation of compound metal oxide films. The films were deposited by sputtering compound targets with oxygen ion beam, extracted from hollow cold cathode ion source.
Low Temperature Silicon Epitaxial Growth by Plasma Enhanced Chemical Vapor Deposition from SiH4/He/H2
Authors: Lin Yung-Jen , Shieh Ming-Deng , Lee Chiapying , Yew Tri-Rung 
Published: March 2011

AbstractSilicon epitaxial growth on silicon wafers were investigated by using plasma enhanced chemical vapor deposition from SiH4/He/H2. The epitaxial layers were growm at temperatures of 350°C or lower. The base pressure of the chamber was greater than 2 × 10−5 Torr. Prior to epitaxial growth, the wafer was in-situ cleaned by H2 baking for 30 min. The epi/substrate interface and epitaxial layers were observed by cross-sectional transmission electron microscopy (XTEM). Finally, the influence of the ex-situ and in-situ cleaning processes on the qualities of the interface and epitaxial layers was discussed in detail.
Low Temperature UV Growth of SiO2 in O2 and N2O
Authors: Kazor Asghar , Boyd Ian W. 
Published: March 2011

AbstractWe report here the use of a low pressure Hg lamp to grow oxide layers on Si in N 2O and O2. Layer thicknesses up to 100Å, whose IR absorption characteristics are similar to those exhibited by thermal oxides, have been produced. Preliminary modelling of the process is described.
Phosphorus and Boron Doping of Silicon Thin Films Using ArF Excimer Laser
Authors: Slaoui A. , Elliq M. , Pattyn H. , Fogarassy E. , Unamuno S. De , Stuck R. 
Published: March 2011

AbstractThis work describes phosphorus (P) and boron (B) doping of polysilicon filns deposited on quartz. Doping is achieved by means of a pulsed ArF excimer laser to melt a controlled thickness of amorphous or polycristalline silicon film coated with a spinon silicate glass (SOG) film containing the dopant (P or B). We have investigated the influence of doping parameters such as laser fluence, number of shots and dopant film thickness on the sheet resistance and the incorporation rate. From these results, we have shown that high doped, shallow junctions presenting sheet resistance lower than 5 kΩ/∠ can be obtained. Poly-Si TFT's with good electrical characteristics were successfully fabricated using this doping technique.
Characterization of High Temperature Superconducting Thin Film Grown by Laser Ablation Method
Authors: Shimizu K. , Nobumasa H. , Nagai N. , Matsunobe T. , Kawai T. 
Published: March 2011

AbstractWe have measured the complex dielectric function of Bi2Sr2CaCu2Oy, samples in the near infrared region directly by spectroellipsometry. As for both single crystal and thin film. superconducting samples have a zero point in the real part (ε1) of the complex dielectric function (ε*) and a clear peak of the imaginary part of the inverse ε* at almost the same frequency. On the other hand, non-superconducting samples have no such ε1, zero point, and the peak height of (-Im(l/ε*)) becomes small. Then we can determine the superconductivity of samples by this spectroellipsometry measurement at room temperature.
Low Temperature Synthesis of Carbide Thin Films by Pulsed Laser Deposition (Pld)
Authors: Donley M.S. , Zabinski J.S. , Sessler W.J. , Dyhouse V.J. , Walck S.D. , McDevitt N.T. 
Published: March 2011

AbstractThin films of titanium carbide (TiC) and boron carbide (B4C) were grown by excimer pulsed laser deposition (PLD) at room temperature (RT) and 300°C. Films were deposited using the output of an excimer laser operating with KrF gas (λ = 248 nm, 15 ns pulse duration) to ablate hot-pressed targets. Film chemistry, morphology, and crystallinity were investigated. Stoichiometric, crystalline TiC films were grown on 440C stainless steel and NaCl substrates at room temperature and at 300°C. The films grown on NaCI were nanocrystallinc, cubic TiC, with a grain size ranging between 2 and 10 nm in diameter. Boron carbide films were grown on silicon {100} substrates at room temperature and at 300°C. Film chemistry and stoichiometry duplicated that of the B4C target, which contained B4C and a mixed C-B-O-N binder phase. SEM analysis indicated that the morphology of the films was uniform, nonporous, and fine-grained. The films exhibited good adhesion and wear resistance, based on friction and wear data collected with a ball-on-disc tribometer.
Growth of Bn Thin Films by Pulsed Laser Deposition
Authors: Knapp J. A. 
Published: March 2011

AbstractA new UHV system for pulsed laser deposition of materials is described, together with results from preliminary experiments for depositions of BN on Si. The system is designed to allow for in-situ diagnostics of the ablation plasma, as well as UHV preparation and characterization of clean sample substrates. The room temperature depositions of BN result in amorphous, B-rich films, whose particle content is a strong function of laser wavelength.
Comparison in Surface Modifications of Sintered and Single Crystal Ceramic Targets After Laser Ablation
Authors: Young K. H. 
Published: March 2011

AbstractA systematic study of the surface morphology and chemical composition of several ceramic targets after pulsed laser ablation has been conducted using a scanning electron microscope with x-ray energy dispersive spectroscopy. We have examined single crystal LaAIO3 and NdGaO3 disks, as well as powder sintered LaAIO3 and SrTiO3 discs. These targets were rotated during laser ablation and concentric trenches were formed with distinctive surface morphologies due to different doses of laser energy. We observed varied light-solid surface interactions on the targets prepared by different methods. The sintered targets exhibited surface explosions after long period laser ablation, presumably due to sub-surface overheating [1]. The single crystal targets have smoother surface morphology and the resulting films have much fewer particles on the surface. As such, they are preferred for laser ablation applications.
The Growth Kinetics and Shape Evolution of Precipitates Growing by the Ledge Mechanism
Authors: Enomoto Masato , Spanos George , Masumura Robert A. 
Published: March 2011

ABSTRACTThe characteristics of ledge growth of precipitates are investigated by a previously developed finite-difference computer model. The plate lengthening simulation results which incorporate measured ledge heights and spacings are in reasonable agreement with the observed lengthening behavior of plates in Fe-C alloys. The simulation which takes into account the diffusion field interaction among multiple precipitates shows that a variety of precipitate morphologies actually observed can possibly be formed solely by the change in the extent of diffusion field overlap among ledges and/or neighboring precipitates. This overlap is in turn caused by changes in the solute supersaturation, distribution of ledge nucleation sites and ledge nucleation rates. A brief discussion is made of the relative growth kinetics of ledged and disordered interfaces.
Velocity and Morphology Transition in Dendritic Growth
Authors: Raz E. , Chait A. 
Published: March 2011

ABSTRACTThe growth velocity and morphology of crystals growing in a supercooled aqueous solution of ammonium chloride (28 wt%) with small amounts of copper sulfate (0.05 to-1 wt%) have been examined. For the [100] growth direction at low supercooling and for the [110] direction at greater supercooling the crystals start to grow slowly with a faceted interface. As the supercooling is continuously increased, the growth direction becomes [111]. Dendrites with pointed tips develop but continue to grow slowly. With further increase in supercooling, the velocity increases 20- to 40-fold and the tip shape changes from a cusp to a thin and almost paraboloid interface while the growth direction remains [111]. The velocity transition is gradual when the concentration is below 0.1 wt% but is sharper at higher concentrations. The transition temperature decreases with increasing copper sulfate concentration.We postulate that the observed transition indicates a dynamic roughening phenomenon, where the supercooling; is sufficiently high to create many nucleation islands on the faceted interface. In this case the interface behaves as an atomically rough surface and dendrite growth occurs at an interface temperature that is below the equilibrium temperature.