bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Reflectometry During LPCVD Tungsten Growth.
Authors: Holleman Jisk , Hasper Albert , Middelhoek Jan 
Published: March 2011

AbstractThe formation of LPCVD tungsten by means of the reduction of WF6 with Si, H2 and SiH4 is monitored in situ using a wavelength adjustable reflectometer. The initial self stopping growth of W by Si reduction is strongly dependant on surface status [1]. SEM observations together with Auger depth profiling and weight measurements support a growth model of islands that grow laterally and vertically until islands touch. After the self stopping Si reduction the W layer was increased in thickness by either the h or SiH4 reduction. The surface roughness calculated from the reflectance appears to increase linearly with thickness in the case of H2 reduction. Typical rms roughness was found to be 7% of layer thickness in the H2 reduction case. The reflectance of H2 reduced W layers could be improved by interrupting the growth process with a renucleation step using SiH4. Selective deposition and in situ growth rate measurements can be monitored when the deposition is carried out on a grating of SiO2 as a mask. Precleaning of the reactor with an NF3 plasma results in a strong retardation of the H2 reduction reaction.
Gas Phase Reactions Relevant to Chemical Vapor Deposition: Optical Diagnostics
Authors: Burgess D. 
Published: March 2011

AbstractLaser photolysis, optical emission, and laser-induced fluorescence (LIF) were used to investigate laser driven decomposition processes in the gas phase pertaining to the systems: SiH4 → Si (s) and SiH4 → NH3 → Si3N4 (s). These processes are important to silicon/ silicon-nitride chemical vapor deposition, flame-driven gas phase silicon-particle nucleation, and laser-induced processes for materials fabrication. UV laser photolysis was used to generate SiHx and NHx species from silane and ammonia. A number of photofragments were identified by emission from excited states. The rate of reaction of NH2 with silane was measured using LIF to detect NH2 as a function of time following photolysis of ammonia
Chemical Vapor Deposition of Silicon Borides
Authors: Goto T. , Mukaida M. , Hirai T. 
Published: March 2011

AbstractMonolithic SiB4±x and SIB6 plates about 1 nm in thickness were prepared by CVD using SiCl4, B2H6 and H2 gases as source materials. The CVD-SiB4±x, plates have nonstoichiometric compositions between B/Si=3.1 and 5.0. The lattice parameters of the CVD-SiB4±x, plates are a=0.633 nm and c=1.262 to 1.271 nm. The density of the CVD-SiB4±x ranges from 2.39 to 2.45 g/cm3. The CVD-SiB6 plates have a constant composition of B/Si=6.0. The lattice parameters of the CVD-SiB6plates are a=1.444 nm, b=1.828 nm, c=0.9915 nm, and their density Is 2.42 g/cm3. These measured densities are both almost in agreement with theoretical values. The electrical conductivity, Seebeck coefficient, Hall mobility and thermal conductivity of the CVD-SiB4±x and CVD-SiB6 plates were examined in the temperature range from 300 to 1000K. The conduction mechanism Is discussed and their figure of merit values for thermoelectric materials are evaluated.
Adhesion of Diamond Films on Various Substrates
Authors: Yen Tyan-Ywan , Kuo Cheng-Tzu , Hsu S. E. 
Published: March 2011

AbstractThe adhesion as determined by indentation of diamond films deposited by microwave plasma-assisted CVD on various substrates was investigated. The critical loads for crack initiation and the propagation of the lateral crack under different loads were measured. The effects of the coating conditions and surface pretreatment of the substrate on the adhesion were examined.
Interaction of Titanium with SiC Coated Boron Fiber
Authors: Hwan Luchen , Tan Beng Jit , Suib Steven L. , Galasso Francis S. 
Published: March 2011

AbstractSICABO fiber, which is one of the silicon carbide coated fibers, has been found to be more stable than BORSIC fiber in titanium matrix composites because SICABO fiber has excess carbon in the SiC layer which was determined by an AES depth profile study. Tensile strength data also show that the SICABO fiber has a higher tensile strength after heating in titanium during hot pressing and chemical vapor deposition processing. Ti5Si3 and TiSi phases were identified from XRD studies on titanium coated BORSIC, but there was no TiSi phase identified in the titanium coated SICABO fiber. AES depth profile results have shown that the BORSIC-Ti has a broad interdiffusion zone.
The Emergence Of Plasma Enhanced Chemical Vapor Deposition (PECVD) As A Viable Industrial Coating Process
Authors: Engle George , Warren James W. 
Published: March 2011

AbstractThe potential of Chemical Vapor Deposition, as a process for applying erosion and corrosion resistant ceramic and metal coatings to ferrous and non-ferrous alloys has long been recognized. Unfortunately, the high deposition temperatures (900°-1000°C) cause deleterious and generally nonreversible metallurgical changes in the coated parts. Corresponding shape stability and dimensional tolerances are also lost. For more than twelve years, Plasma Enhanced Chemical Vapor Deposition (PECVD) technology has evolved from the laboratory into production operations within the semiconductor industry.This acceptance is primarily due to the low PECVD deposition temperatures (<450 ° C). The PECVD processes have recently demonstrated an adaptability to coating alloy components and carbon/ceramic fibers with a wide range of carbide, boride, nitride, oxide and metal coatings to render them corrosion and erosion resistant. Typical Knoop hardness control of sili on carbide coatings can be controlled from about 2300 to more than 7000 kgfmn−2 at 10% penetration of the indenter while coating thickness and uniformity can be controlled from 300A ± 5%. Selected coating applications and performance are described.
Laser Induced Photochemical Vapor Deposition of Tungsten on Silicon
Authors: Maaren A. J. P. van , Sinke W. C. 
Published: March 2011

AbstractAn ArF excimer laser (193 nm) aligned parallel to the substrate has been used to initiate photo-activation of the W-CVD process. W was deposited on silicon and SIMOX at a 310 °C substrate temperature using WF6 as a W precursor, together with H2. The samples were analyzed after deposition with SEM and 2 MeV He+ RBS, to obtain information about the reaction between WF6 and Si in laser-induced CVD of W. The data indicate that the reaction between WF6 and Si is suppressed upon laser irradiation. The suppression increases with increasing laser-pulse frequency. An explanation for this phenomenon is given in terms of atomic Hformation after (partial) photodissociation of WF6.
Silicon Nitride Synthesis by Laser Pyrolysis of an Aerosol-Dispersed Precursor
Authors: Xiao Tongsan D. , Strutt Peter R. , Gonsalves Kenneth E. 
Published: March 2011

AbstractSurface layers of ultrafine Si3N4 particles (30–100 nm. diameter) have been synthesized by laser-pyrolysis of a liquid precursor, dispersed as an aerosol. This aerosol was formed in a nitrogen environment (at near ambient pressure) using an ultrasonically activated nozzle. The organosilazane precursor, which was specially designed for CO2 laser pyrolysis, was of the type (CH3SiHNH)x, with x = 3 or 4. In the current experiments deposition was performed on Ni substrates using a (i) 7 cm/s. substrate translational velocity, and (ii) ˜2.8 × 102 w/cm2 power density.
Titanium Nitride Thin Films: Properties and Apcvd Synthesis Using Organometallic Precursors
Authors: Fix Renaud M. , Gordon Roy G. , Hoffman David M. 
Published: March 2011

AbstractA novel process for the low temperature synthesis of titanium nitride thin films by APCVD is described. TiN coatings containing less than one atom percent of carbon and oxygen were deposited at 200 °C on silicon, vitreous carbon, glass, stainless steel and plastic substrates using Ti(Nme2)4 and ammonia gas as precursors. The films were characterized by Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy.
Calculation of Transport-Shifted CVD Phase Diagrams
Authors: Rosner Daniel E. , Collins Joshua 
Published: March 2011

AbstractA non-iterative method is presented for constructing CVD phase diagrams which include the systematic effects of chemical element segregation in mass-transfer controlled flow reactors. Element segregation is shown to substantially shift predicted deposit phase boundaries when the vapor/deposit interface equilibrium is calculated using the local element fractions instead of the feed gas elemental composition, as is usually done. The mass transfer analysis developed here accounts for both Fick and Soret multicomponent diffusion acting across a non-isothermal boundary layer. The gas phase is assumed to be chemically frozen, with local thermochemical equilibrium imposed only at the vapor/deposit interface (as in a cold wall reactor with a hot substrate). As a specific example, this model is applied to the chemical vapor deposition of titanium diboride from TiCl4(g), BC13(g) and H2(g) in an Ar(g) carrier gas for ceramic composite material applications. These calculations, which account for boron and titanium transport via 17 chemical species, are illustrated for a long cylindrical reactor with a resistively heated coaxial fiber deposition substrate and coaxial annular flow. However, the method presented here is general in that both the chemical system and CVD reactor geometry can be changed to any other system of interest, provided: i) adequate themochemical and thermophysical data are available, ii) the deposition rate is vapor transport controlled, and iii) convective-diffusion heat and mass transfer coefficients are estimable.
Light-Scattering Measurements of CVD Silicon Carbide
Authors: Sheldon B. W. , Besmann T. M. 
Published: March 2011

AbstractSurface morphologies created by the chemical vapor deposition (CVD) of silicon carbide were examined with light scattering. Silicon carbide was deposited from methyltrichlorosilane under various conditions to create different surfaces. A helium neon laser was used, and the scattered light was measured over a range of scattering angles. These measurements are compared with scanning electron microscopy (SEM) observations and profilometer measurements of the same surfaces. In theory the scattered light contains all of the information needed to provide a statistical description of a given surface; however, a complete vector theory for the scattering phenomena is too complex to provide any simple basis for experimental analysis. The application and limits of existing descriptions of scattering from a rough surface are discussed.
Raman Measurements of Epitaxial YBa2Cu3O7–δ Films
Authors: Burns G. , Dacol F. H. , Feild C. A. , Gupta A. , Holtzberg F. , Koren G. , Laibowitz R. , McGuire T. R. , Segmuller A. P. , Worthington T. K. 
Published: March 2011

AbstractWe have measured the infrared (IR) reflectance and Raman spectra of electron doped and undoped Nd2CuO4 and Pr2CuO4. Utilizing the results from doped ceramics and undoped ab plane oriented single crystals, we observe and assign all the IR active phonons (3A2u + 4Eu) predicted by group theory. We have also observed the Raman active modes involving atom motion along the c axis. We compare our results to those found in the related hole superconductors based upon La2CuO4.
Magnetic and 119-Sn Mössbauer Effect Study of Sn-Doped Pb2Sr2Eu.5Cu3-xSnxO8+z (x = 0.0, 0.1) Superconductors
Authors: Vaishnava P. P. , Nelson C. D. , Pratt W. P. 
Published: March 2011

AbstractX-ray diffraction, magnetic susceptibility and 119-Sn Mössbauer effect measurements have been performed on Pb2Sr2Eu.5Cu3-xSnx08+z (x = 0.0, 0.1) superconductors. The x-ray diffraction pattern indicated that the samples are single phase materials. The diamagnetic shielding and the Meissner fraction increase with the introduction of Sn in the lattice. The 119-Sn Mössbauer effect measurements have been used to determine the site symmetry and valence state of Sn atom in the superconductor.
Superconductivity and Stoichiometry in Tl2Ca2Ba2Cu3Ox Single Crystals
Authors: Venturini E. L. , Tigges C. P. , Baughman R. J. , Ginley D. S. , Morosin B. 
Published: March 2011

AbstractMagnetization and resistivity data are presented which show a substantial difference in superconducting transitions for nominal Tl2Ca2Ba2Cu3Ox plates with identical crystal structures grown from two different “melt” compositions. A Tl-O and CuO-rich flux yielded approximately stoichiometric plates which have sharp transitions beginning near 111 K, while a second Tl-O-rich flux produced plates containing more Tl and less Ba with very broad transitions starting near 96 K. These data demonstrate the extreme sensitivity of superconductivity to cation site disorder in the Tl-Ca-Ba-Cu-O system.
Magnetic Properties of Pb2Sr2Eu1-xCaxCu308+z Superconductors
Authors: Nelson C.D. , Pratt W.P. , Vaishnava P.P. 
Published: March 2011

AbstractX-ray diffraction and magnetic measurements using a SQUID magnetometer have been performed on the title compounds for 0 ≤ x ≤ 0.9. For 0 ≤ x ≤ 0.5, we have single phase materials. However, a small percentage of an impurity phase is noticed in the x = 0.7 sample, and the x = 0.9 sample is clearly not a single phase material. The transition temperature, the diamagnetic-shielding effect, and the Meissner-effect increase as x becomes larger. We have obtained, approximately, Hc1 ≤ 700 oe and Hc2 ≥ 800 k0e.
Certain Novel Aspects of Thallium and Bismuth Cuprate Superconductors
Authors: Rao C. N. R. 
Published: March 2011

AbstractNovel superconducting thallium cuprates of the type T1Ca1‐X LnX Sr2 Cu2O6+δ (Ln = Y or rare earth), T1Srn+1‐x Lnx Cun OY and Tl1‐x PbX Srn+1Cun08+δ are described. These cuprates as well as Bi2Ca1‐x Lnx Sr2Cu2O8+δ and TICa1‐xYxBa2 Cu2 O6+δ . show maximum T around a specific composition or oxygen content. They also show interesting changes in the sign and magnitude of the thermopower with the composition. Specially noteworthy is the negative slope of the thermopower‐temperature plots. The thermopower behaviour in these two‐band systems can be understood in terms of entropie and quasiparticle contributions. It appears that Tl1‐x Pbx CaSr2Cu2O6+δ is a genuine high T electron superconductor.
Ibad Diffusion Barriers Between YBaCuO and Si
Authors: Greenwald Anton , Hirvonen James , Jaggi Narendra , Allen John 
Published: March 2011

AbstractDifferent materials were investigated for use as diffusion barriers between silicon and yttrium barium copper oxide (YBCO). Ion beam assisted deposition (IBAD) of 300nm zirconia films at room temperature prevented interdiffusion at sintering temperatures over 800°C. Similar MgO and indium-tin oxide films did not prevent degradation at elevated temperatures. All films deposited on top of YBCO reduced the effects of extended atmospheric exposure.
The Influence of Tte Substrate Surface on the Nucleation and Growth of Superconducting Thin Films
Authors: Basu S. N. , Bordes N. , Rollett A. , Cohen M. , Nastasi M. 
Published: March 2011

AbstractThe quality of epitaxially grown superconducting thin films is dependent on the nature of the substrate surface. In this study, the surface of <100> oriented SrTiO3 single crystals was modified by mechanical polishing, thermal annealing and chemical etching. A study of the YBa2Cu3O7-x thin films grown on these substrates showed that high quality superconducting films were obtained when the substrate surface was highly oriented in the <100> direction and was also microscopically smooth.
Electric-field modulation of a Bi-Sr-Ca-Cu-O film with a polymer film as an insulator
Authors: Morohashi Shin'ichi , Suzuki Hideo , Gotoh Kohtaroh , Fujimaki Norio , Hasuo Shinya 
Published: March 2011

AbstractWe fabricated the multi layered structure with Au gate electrode/polymer film/Bi-Sr-Ca-Cu-O film to study the electric-field control of high Tc superconductor. A Bi-Sr-Ca-Cu-O(BSCCO) film was fabricated using an ion beam sputtering technique. The plasma polymerization using trif luoroethane gas was used to make the gate insulator. The patterning of the BSCCO film was carried out using an ion beam etching technique. The supercurrent of the structure decreased when the gate voltage was applied to the gate electrode.
Use of Si-YBaCuO Intermixed System for Patterning of Superconducting Thin Films
Authors: Ma Q. Y. , Yang E. S. , Treyz G. V. , Shu C. , Osgood R. M. , Chang Chin-An 
Published: March 2011

AbstractA Si-YBaCuO intermixed system has been formed using rapid thermal annealing (RTA) of Cu/BaO/Y2O2/Si layered structures, which were deposited on MgO substrates by electron-beam evaporation. The electrical and structural properties of the Si-YBaCuO system have been analyzed by resistivity, X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy and Auger depth profiling measurements. It was found that Si mixed with YBaCuO during annealing, thus creating an insulating film. This effect has been used to pattern YBaCuO films. The patterning process was carried out on an underlying silicon layer, rather than the YBaCuO film itself, using conventional photolithography or laser etching. After YBaCuO film deposition and RTA, the patterned region became superconducting separated by Si-YBaCuO intermixed areas. Micron-sized line features with Tc's above 77 K have been demonstrated.
Transport Measurements on Superconducting YBa2Cu3O7-δ Thin Film Lines
Authors: Moeckly B. H. , Lathrop D. K. , Redinbo G. F. , Russek S. E. , Buhrman R. A. 
Published: March 2011

AbstractCritical current densities, magnetic field response, and microwave response have been measured for laser ablated YBa2Cu3O7-δ thin film lines on MgO and SrTiO3 substrates. Films on SrTiO3 have critical current densities > 1 x 106 A/cm2 at 77K and show uniform transport properties in lines of all sizes. Films on MgO have critical current densities which range between 102 and 106 A/cm2 at 77K and show considerable variation from device to device on the same chip. Narrow lines on MgO with low critical current densities show Josephson weak link structure which includes RSJ-like IV curves, microwave induced constant voltage steps, and a high sensitivity to magnetic field. The presence of the Josephson weak links is correlated with small amounts of misaligned grains in films on MgO.
High TC Superconductor Fibers from Metallo-Organic Precursors
Authors: Chen K.C. , Mazdiyasni K.S. 
Published: March 2011

AbstractHomogeneous solution for Y-Ba-Cu-0 superconductor was prepared from yttrium i-propoxide, barium i-propoxide, and copper ethylhexanoate. The solution was converted to a resin-like material and was readily dissolved in organic solvents. The resin possesses a cohesive property in a number of solvents, such as benzene and xylene. Single-phase superconducting YBa2Cu307_x fibers have been continuously spun from the viscous solution. Controlled amounts of Y2BaCu05 phase in the fibers were made possible by slight adjustments in the solution compositions. Partial substitution of copper ethylhexanoate with copper trifluoroacetate prevents barium carbonate formation In the fiber during curing and organic pyrolysis.
Effect of Magnetic Field on Critical Current Density in Bulk Superconducting Wires
Authors: Lanagan M. T. , Balachandran U. , Youngdahl C. A. , Dusek J. T. , Picciolo J. J. , Poeppel R. B. 
Published: March 2011

AbstractBulk YBa2Cu3O7‐x (YBCO) wires and tubes were fabricated by an extrusion technique. Critical current density (Jc) was measured as a function of applied magnetic field at 77 K and was found to decrease significantly in fields below 100 G. Jc was dependent on specimen geometry. In addition, when a concentric magnetic field was generated by passing a current though a copper wire, the external field from the wire could interfere constructively or destructively with the magnetic field produced by current in a YBCO tube. The change in electrical properties with magnetic field has been attributed to weak‐link behavior at the grain boundaries. Batch‐to‐batch differences in the field dependence of Jc imply the possibility of reducing the dependence by processing modifications.
Novel Processing of Hts Based Conductors
Authors: Ginley D. S. , Venturini E. L. , Kwak J. F. , Baughman R. J. , Bourceer R. J. , Mitchell M. A. , Morosin B. , Halloran J. W. , Neal M. J. , Ca- Pone D. W. 
Published: March 2011

AbstractConductor development is one of the major long term goals in high temperature superconductor research. In this paper we report on two promising processing technologies that have been utilized to produce superconducting HTS conductors. First, melt spun YBa2Cu3O7 fibers rapid thermal processed for 1‐8 sec at 950 to 1075°C have Tc's to 92 K, Jc's to 1100 A/cm2 and the orthorhombic twinned morphology typical for high quality YBa2Cu3O7 A processing matrix of time, temperature and composition for these fibers shows that slightly CuO‐rich starting compositions give the best results. Second, silver tube encapsulated wires of Bi1.7Pb0.3Sr2Ca2Cu3O10 have been made by extrusion, wire drawing and cold rolling. The resulting tapes show orientation of the crystallites, zero resistance up to 100K and improved magnetic hysteresis above 50 K. The combination of mechanical reprocessing and extended thermal anneals near 850°C appears to significantly improve these materials.
Studies on Microstructure - Property Relationship of Yba2Cu3O7-X + Ag2O Composite Wire
Authors: Samajdar S. , Gouthama  , Samanta S. K. 
Published: March 2011

AbstractSilver is known to act as a compatible metal host for designing a microcomposite system with the high temperature superconducting ceramic YBCO[l,3]. The unique role played by nascent silver generated from the silver monoxide precursor during sintering as well as warm compaction of the powder mix is illustrated with the help of light optical micrography. It is seen that electrical as well as mechanical properties of the bulk composite is significantly governed by its microstructure. The microstructure, in turn, could be controlled by suitable heal treatment and proper selection of the fabrication process parameters at every step. Attempting a structure‐propcrty‐processing correlation, a microstructure controlled scheme for fabricating superconducting composite product of useful shapes is discussed. Successful fabrication of thin (0.75 mm dia.) and long (450 mm) flexible wire following this route is also reported here.
Wet Chemical Etching of High TC Superconductors by Ethylenediaminetetraacetic Acid (EDTA)
Authors: Shokoohi F. K. , Schiavone L. M. , Rogers C. T. , Inam A. , Wu X. D. , Nazar L. , Venkatesan T. 
Published: March 2011

AbstractA novel chemical etchant for the high temperature superconducting material YBa2Cu3O7‐x is demonstrated. The etching solution which consists of ethylenediaminetetraacetic acid (EDTA) in water does not degrade the properties of the superconducting films and is suitable for applications with standard photolithography. We have etched 2‐200 μm wide wires which show no degradation of Tc ( within 1 K accuracy of the measurements) and show zero‐resistance temperature ≥90 K. The etchant exhibits a polishing effect by selectively removing the porous and semiconducting surface layers which are formed during high temperature annealing process. The dense bulk of the films are etched at a rate of 1400 Å/min which provides control for fine‐line patterning of thin film material. The critical current densities of the unpatterned films which are polished by reactions with EDTA remain unaffected and are measured to be about 5 x 106 A/cm2.