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Surface and Interfacial Studies of Metal-Organic Chemical Vapor Deposition of Copper

Description: The nucleation and successful growth of copper (Cu) thin films on diffusion barrier/adhesion promoter substrates during metal-organic chemical vapor deposition (MOCVD) are strongly dependent on the initial Cu precursor-substrate chemistry and surface conditions such as organic contamination and oxidation. This research focuses on the interactions of bis(1,1,1,5,5,5-hexafluoroacetylacetonato)copper(II), [Cu(hfac)2], with polycrystalline tantalum (Ta) and polycrystalline as well as epitaxial titanium nitride (TiN) substrates during Cu MOCVD, under ultra-high vacuum (UHV) conditions and low substrate temperatures (T < 500 K). The results obtained from X-ray photoelectron spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Temperature Programmed Desorption (TPD) measurements indicate substantial differences in the chemical reaction pathways of metallic Cu formation from Cu(hfac)2 on TiN versus Ta surfaces.
Date: December 1997
Creator: Nuesca, Guillermo M.
Partner: UNT Libraries

Strontium Program: Quarterly Summary Report, November 19, 1958

Description: From Abstract: "This report up-dates certain sections of HASL-42, "Environmental Contamination from Weapon Tests". In particular, the levels of Strontium-90 in fallout, milk, tap water, air, and soil are included for data available up to November 1, 1958."
Date: November 19, 1958
Creator: Hardy, Edward P., Jr. & Klein, Stanley
Partner: UNT Libraries Government Documents Department

Selectivity Failure in the Chemical Vapor Deposition of Tungsten

Description: Tungsten metal is used as an electrical conductor in many modern microelectronic devices. One of the primary motivations for its use is that it can be deposited in thin films by chemical vapor deposition (CVD). CVD is a process whereby a thin film is deposited on a solid substrate by the reaction of a gas-phase molecular precursor. In the case of tungsten chemical vapor deposition (W-CVD) this precursor is commonly tungsten hexafluoride (WF6) which reacts with an appropriate reductant to yield metallic tungsten. A useful characteristic of the W-CVD chemical reactions is that while they proceed rapidly on silicon or metal substrates, they are inhibited on insulating substrates, such as silicon dioxide (Si02). This selectivity may be exploited in the manufacture of microelectronic devices, resulting in the formation of horizontal contacts and vertical vias by a self-aligning process. However, reaction parameters must be rigorously controlled, and even then tungsten nuclei may form on neighboring oxide surfaces after a short incubation time. Such nuclei can easily cause a short circuit or other defect and thereby render the device inoperable. If this loss of selectivity could be controlled in the practical applications of W-CVD, thereby allowing the incorporation of this technique into production, the cost of manufacturing microchips could be lowered. This research was designed to investigate the loss of selectivity for W-CVD in an attempt to understand the processes which lead to its occurrence. The effects of passivating the oxide surface with methanol against the formation of tungsten nuclei were studied. It was found that the methanol dissociates at oxide surface defect sites and blocks such sites from becoming tungsten nucleation sites. The effect of reactant partial pressure ratio on selectivity was also studied. It was found that as the reactant partial pressures are varied there are significant changes in the ...
Date: August 1994
Creator: Cheek, Roger W. (Roger Warren)
Partner: UNT Libraries

Dry Deposition Velocity Estimation for the Savannah River Site: Part 2 -- Parametric and Site-Specific Analysis

Description: Values for the dry deposition velocity of airborne particles were estimated with the GENII Version 2.10.1 computer code for the Savannah River site using assumptions about surface roughness parameters and particle size and density. Use of the GENII code is recommended by the U.S. Department of Energy for this purpose. Meteorological conditions evaluated include atmospheric stability classes D, E, and F and wind speeds of 0.5, 1.0, 1.5, and 2.0 m/s. Local surface roughness values ranging from 0.03 to 2 meters were evaluated. Particles with mass mean diameters of 1, 5, and 10 microns and densities of 1, 3, 4, and 5 g/cm3 were evaluated. Site specific meteorology was used to predict deposition velocity for Savannah River conditions for a range of distances from 670 to 11,500 meters.
Date: September 12, 2013
Creator: Napier, Bruce A.; Rishel, Jeremy P. & Cook, Kary M.
Partner: UNT Libraries Government Documents Department

Sputter deposition of metallic thin film and directpatterning

Description: A compact apparatus is developed for deposition of metal thin film. The system employs an RF discharge plasma source with a straight RF antenna, which is made of or covered with deposition material, serving as sputtering target at the same time. The average deposition rate of copper thin film is as high as 450nm/min. By properly allocating the metal materials on the sputtering antenna, mixture deposition of multiple metal species is achieved. Using an ion beam imprinting scheme also taking advantage of ion beam focusing technique, two different schemes of direct patterning deposition process are developed: direct depositing patterned metallic thin film and resistless ion beam sputter patterning. Preliminary experiments have demonstrated direct pattern transfer from a template with feature size of micro scale; patterns with more than 10x reduction are achieved by sputtering patterning method.
Date: September 9, 2005
Creator: Ji, L.; Chen, Y.; Jiang, X.; Ji, Q. & Leung, K.-N.
Partner: UNT Libraries Government Documents Department

Atmospheric Mercury near Salmon Falls Creek Reservoir in Southern Idaho

Description: Gaseous elemental mercury (GEM) and reactive gaseous mercury (RGM) were measured over two-week seasonal field campaigns near Salmon Falls Creek Reservoir in south-central Idaho from the summer of 2005 through the fall of 2006 and over the entire summer of 2006 using automated Tekran mercury analyzers. GEM, RGM, and particulate mercury (HgP) were also measured at a secondary site 90 km to the west in southwestern Idaho during the summer of 2006. The study was performed to characterize mercury air concentrations in the southern Idaho area for the first time, estimate mercury dry deposition rates, and investigate the source of observed elevated concentrations. High seasonal variability was observed with the highest GEM (1.91 ± 0.9 ng m-3) and RGM (8.1 ± 5.6 pg m-3) concentrations occurring in the summer and lower values in the winter (1.32 ± 0.3 ng m-3, 3.2 ± 2.9 pg m-3 for GEM, RGM respectively). The summer-average HgP concentrations were generally below detection limit (0.6 ± 1 pg m-3). Seasonally-averaged deposition velocities calculated using a resistance model were 0.034 ± 0.032, 0.043 ± 0.040, 0.00084 ± 0.0017 and 0.00036 ± 0.0011 cm s-1 for GEM (spring, summer, fall, and winter, respectively) and 0.50 ± 0.39, 0.40 ± 0.31, 0.51 ± 0.43 and 0.76 ± 0.57 cm s-1 for RGM. The total annual RGM + GEM dry deposition estimate was calculated to be 11.9 ± 3.3 µg m-2, or about 2/3 of the total (wet + dry) deposition estimate for the area. Periodic elevated short-term GEM (2.2 – 12 ng m-3) and RGM (50 - 150 pg m-3) events were observed primarily during the warm seasons. Back-trajectory modeling and PSCF analysis indicated predominant source directions from the southeast (western Utah, northeastern Nevada) through the southwest (north-central Nevada) with fewer inputs from the northwest (southeastern Oregon and southwestern ...
Date: December 1, 2007
Creator: Abbott, Michael L. & Einerson, Jeffrey J.
Partner: UNT Libraries Government Documents Department

Approaches to rid cathodic arc plasmas of macro- andnanoparticles: A review

Description: A major obstacle for the broad application of cathodic arc plasma deposition is the presence of micro- and nanoparticles in the plasma, also often referred to as 'macroparticles'. This paper reviews the formation of macroparticles at cathode spots, their interaction with the arc plasma and substrate, and macroparticle separation and removal from the plasma by various filtering methods. Nineteen variants of filters are discussed, including Aksenov's classic 90{sup o}-duct filter, filters of open architecture, and the concept of stroboscopic filtering.
Date: June 1, 1999
Creator: Anders, Andre
Partner: UNT Libraries Government Documents Department

A concentration rebound method for measuring particle penetrationand deposition in the indoor environment

Description: Continuous, size resolved particle measurements were performed in two houses in order to determine size-dependent particle penetration and deposition in the indoor environment. The experiments consisted of three parts: (1) measurement of the particle loss rate following artificial elevation of indoor particle concentrations, (2) rapid reduction in particle concentration through induced ventilation by pressurization of the houses with HEPA-filtered air, and (3) measurement of the particle concentration rebound after house pressurization stopped. During the particle concentration decay period, when indoor concentrations are very high, losses due to deposition are large compared to gains due to particle infiltration. During the concentration rebound period, the opposite is true. The large variation in indoor concentration allows the effects of penetration and deposition losses to be separated by the transient, two-parameter model we employed to analyze the data. We found penetration factors between 0.3 and 1 and deposition loss rates between 0.1 and 5 h{sup -1}, for particles between 0.1 and 10 {micro}m.
Date: September 1, 2002
Creator: tlthatcher@lbl.gov
Partner: UNT Libraries Government Documents Department

Models and Measurements: Complementary Tools for Predicting Atmospheric Dispersion and Assessing the Consequences of Nuclear and Radiological Emergencies

Description: Since its inception over 26 years ago, NARAC (the National Atmospheric Release and Advisory Center) has used measurement data to update model predictions of radioactive releases from known origins. NARAC continues to routinely participate in emergency response drills with organizations that collect air concentration, ground deposition, and radiation exposure measurements. From a complementary perspective, NARAC is now developing an advanced capability to combine models and data from monitoring systems to characterize and forensically reconstruct atmospheric release events of unknown origin.
Date: November 7, 2005
Creator: Bradley, M M; Kosovic, B & Nasstrom, J S
Partner: UNT Libraries Government Documents Department

A novel method to synthesize high purity, nanostructured copper

Description: Nanostructured high purity (99.999%) copper foils, 10 cm in diameter and 22-25 microns thick were produced using nanoscale multilayer technology. The foils were produced using five different layer thicknesses ranging from 1.25 to 43.6 nm (18,000 to 520 layers). This process delivers the ability to produce multiple large-scale samples during a single deposition run with very small residual stresses. Tensile and indentation tests demonstrate that the material produced is a high strength copper ({sigma}{sub y} {approx} 540-690 MPa).
Date: August 30, 2005
Creator: Hodge, A M; Wang, Y M & Barbee, T W
Partner: UNT Libraries Government Documents Department

Comparative Deposition of Zr95 in a Reticulo Endothelial Tumor to Normal Tissue in a Human Patient

Description: A test dose of Zr{sup 95} was given to a female patient which had a metastatic reticula endothelial tumor at the distal portion of the left femur. A comparison of the deposition of Zr{sup 95} showed greater uptake 24 hours after administration than any of the normal tissues investigated.
Date: March 1, 1948
Creator: Low-Beer, B.V.; Scott, K.G.; Hamilton, J.G. & Stone, R.S.
Partner: UNT Libraries Government Documents Department

Growing carbon nanotubes by chemical vapor deposition technique.

Description: Carbon nanotubes were synthesized in the laboratory using chemical vapor deposition at different methane concentration. I found that a methane concentration of 4 sccm was ideal for well recognizable carbon nanotubes. A higher concentration led to fewer nanotube growth and silicon carbide structure. Coating the sample first with Fe(NO3)3 created a catalyst base on the substrate for the nanotube to adhere and grow on.
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Date: May 2000
Creator: Rajan, Harihar V.
Partner: UNT Libraries

Laser Deposition, Heat-treatment, and Characterization of the Binary Ti-xmn System

Description: The present research seeks to characterization of an additively manufactured and heat-treated Ti-xMn gradient alloy, a binary system that has largely been unexplored. In order to rapidly assess this binary system, compositionally graded Ti-xMn (0<x<15 wt%) specimens were fabricated using the LENS (Laser Engineered Net Shaping) and were subsequently heat-treated and characterized using a wide range of techniques. Microstructural changes with respect to the change in thermal treatments, hardness and chemical composition were observed and will be presented. These include assessments of both continuous cooling, leading to observations of both equilibrium and metastable phases, including the titanium martensites, and to direct aging studies looking for composition regimes that produce highly refined alpha precipitates – a subject of great interest given recent understandings of non-classical nucleation and growth mechanisms. The samples were characterized using SEM, EDS, TEM, and XRD and the properties probed using a Vickers Microhardness tester.
Date: August 2013
Creator: Avasarala, Chandana
Partner: UNT Libraries

Evaluation of methods for application of epitaxial layers of superconductor and buffer layers

Description: The recent achievements in a number of laboratories of critical currents in excess of 1.0x10{sup 6} amp/cm{sup 2} at 77K in YBCO deposited over suitably textured buffer/substrate composites have stimulated interest in the potential applications of coated conductors at high temperatures and high magnetic fields. As of today, two different approaches for obtaining the textured substrates have been identified. These are: Los Alamos National Laboratory`s (LANL) ion-beam assisted deposition called IBAD, to obtain a highly textured yttria-stabilized zirconia (YSZ) buffer on nickel alloy strips, and Oak Ridge National Laboratory`s (ORNL) rolling assisted, bi-axial texturized substrate option called RABiTS. Similarly, based on the published literature, the available options to form High Temperature Superconductor (HTS) films on metallic, semi-metallic or ceramic substrates can be divided into: physical methods, and non-physical or chemical methods. Under these two major groups, the schemes being proposed consist of: - Sputtering - Electron-Beam Evaporation - Flash Evaporation - Molecular Beam Epitaxy - Laser Ablation - Electrophoresis - Chemical Vapor Deposition (Including Metal-Organic Chemical Vapor Deposition) - Sol-Gel - Metal-Organic Decomposition - Electrodeposition, and - Aerosol/Spray Pyrolysis. In general, a spool- to-spool or reel-to-reel type of continuous manufacturing scheme developed out of any of the above techniques, would consist of: - Preparation of Substrate Material - Preparation and Application of the Buffer Layer(s) - Preparation and Application of the HTS Material and Required Post-Annealing, and - Preparation and Application of the External Protective Layer. These operations would be affected by various process parameters which can be classified into: Chemistry and Material Related Parameters; and Engineering and Environmental Based Parameters. Thus, one can see that for successful development of the coated conductors manufacturing process, an extensive review of the available options was necessary. Under the U.S. Department of Energy (DOE`s) sponsorship, the University of Tennessee Space Institute (UTSI), was ...
Date: June 1, 1997
Partner: UNT Libraries Government Documents Department

Composition and Bonding in Amorphous Carbon Films Grown by Ion Beam Assisted Deposition: Influence of the Assistance Voltage

Description: Amorphous carbon films have been grown by evaporation of graphite with concurrent Ar+ ions bombardment assistance. The ion energy has been varied between 0-800 V while keeping a constant ion to carbon atom arrival ratio. Film composition and density were determined by ion scattering techniques (RBS and ERDA), indicating a negligible hydrogen content and a density dependence with the assistance voltage. The bonding structure of the films has been studied by Raman and X-ray Absorption Near-Edge (XANES) spectroscopy. Different qualitative effects have been found depending on the ion energy range. For ion energies below 300 eV, there is a densification of the carbon layer due to the increase in the sp3 content. For ion energies above 300 eV sputtering phenomena dominate over densification, and thinner films are found with increasing assistance voltage until no film is grown over 600 V. The films with the highest SP3 content are grown with intermediate energies between 200-300 V.
Date: November 12, 1998
Creator: Albella, J.M.; Banks, J.C.; Climent-Font, A.; Doyle, B.L.; Gago, R.; Jimenez, I. et al.
Partner: UNT Libraries Government Documents Department

HFCVD of diamond at low substrate and low filament temperatures

Description: It has been discovered that the addition of a small amount of oxygen to the CH{sub 4} and H{sub 2} feed gas permits HFCVD of diamond at significantly lower filament and substrate temperatures. The effective O/C ratio here is much lower than that used in most studies of the oxygen effect. Careful control of the O/C and C/H ratios were found to be crucial to success. The effects of substrate and filament temperatures on growth rate and film quality were studied. Optimum conditions were found that gave reasonable growth rates ( {approximately}0.5 {mu}m/h ) with high film quality at filament temperatures below 1750{degrees}C and substrate temperatures below 600C. As a result, low temperature deposition has been realized. Power consumption can be reduced 50%, and the filament lifetime is extended indefinitely.
Date: March 8, 1995
Creator: Tolt, Z. L.; Heatherly, L.; Clausing, R. E.; Shaw, R. W. & Feigerle, C. S.
Partner: UNT Libraries Government Documents Department