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  Partner: UNT Libraries
 Degree Discipline: Chemistry
 Degree Level: Doctoral
Adhesion/Diffusion Barrier Layers for Copper Integration: Carbon-Silicon Polymer Films and Tantalum Substrates

Adhesion/Diffusion Barrier Layers for Copper Integration: Carbon-Silicon Polymer Films and Tantalum Substrates

Date: December 1999
Creator: Chen, Li
Description: The Semiconductor Industry Association (SIA) has identified the integration of copper (Cu) with low-dielectric-constant (low-k) materials as a critical goal for future interconnect architectures. A fundamental understanding of the chemical interaction of Cu with various substrates, including diffusion barriers and adhesion promoters, is essential to achieve this goal. The objective of this research is to develop novel organic polymers as Cu/low-k interfacial layers and to investigate popular barrier candidates, such as clean and modified tantalum (Ta) substrates. Carbon-silicon (C-Si) polymeric films have been formed by electron beam bombardment or ultraviolet (UV) radiation of molecularly adsorbed vinyl silane precursors on metal substrates under ultra-high vacuum (UHV) conditions. Temperature programmed desorption (TPD) studies show that polymerization is via the vinyl groups, while Auger electron spectroscopy (AES) results show that the polymerized films have compositions similar to the precursors. Films derived from vinyltrimethyl silane (VTMS) are adherent and stable on Ta substrates until 1100 K. Diffusion of deposited Cu overlayers is not observed below 800 K, with dewetting occurred only above 400 K. Hexafluorobenzene moieties can also be incorporated into the growing film with good thermal stability. Studies on the Ta substrates demonstrate that even sub-monolayer coverages of oxygen or carbide on polycrystalline ...
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Adsorbate-enhanced Corrosion Processes at Iron and Iron Oxide Surfaces

Adsorbate-enhanced Corrosion Processes at Iron and Iron Oxide Surfaces

Date: December 1994
Creator: Murray, Eric
Description: This study was intended to provide a fuller understanding of the surface chemical processes which result in the corrosion of ferrous materials.
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Aldohaloketenes and the Stereochemistry of Aldohaloketene Cycloadditions

Aldohaloketenes and the Stereochemistry of Aldohaloketene Cycloadditions

Date: May 1970
Creator: Hoff, Edwin Frank
Description: The objective of this research problem was to synthesize aldohaloketenes and investigate the chemistry of this new class of ketenes.
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Analysis of Acid Gas Emissions in the Combustion of the Binder Enhanced d-RDF by Ion Chromatography

Analysis of Acid Gas Emissions in the Combustion of the Binder Enhanced d-RDF by Ion Chromatography

Date: August 1988
Creator: Jen, Jen-Fon
Description: Waste-to-energy has become an attractive alternative to landfills. One concern in this development is the release of pollutants in the combustion process. The binder enhanced d-RDF pellets satisfy the requirements of environmental acceptance, chemical/biological stability, and being storeable. The acid gas emissions of combusting d-RDF pellets with sulfur-rich coal were analyzed by ion chromatography and decreased when d-RDF pellets were utilized. The results imply the possibility of using d-RDF pellets to substitute for sulfur-rich coal as fuel, and also substantiate the effectiveness of a binder, calcium hydroxide, in decreasing emissions of SOx. In order to perform the analysis of the combustion sample, sampling and sample pretreatment methods prior to the IC analysis and the first derivative detection mode in IC are investigated as well. At least two trapping reagents are necessary for collecting acid gases: one for hydrogen halides, and the other for NOx and SOx. Factors affecting the absorption of acid gases are studied, and the strength of an oxidizing agent is the main factor affecting the collection of NOx and SOx. The absorption preference series of acid gases are determined and the absorption models of acid gases in trapping reagents are derived from the analytical results. To prevent ...
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The Analysis of Volatile Impurities in Air by Gas Chromatography/Mass Spectrometry

The Analysis of Volatile Impurities in Air by Gas Chromatography/Mass Spectrometry

Date: May 1993
Creator: Talasek, Robert Thomas
Description: The determination of carbon monoxide is also possible by trapping CO on preconditioned molecular sieve and thermal desorption. Analysis in this case is performed by gas chromatography/mass spectroscopy, although the trapping technique is applicable to other suitable GC techniques.
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Aromatic Amino Acid Studies

Aromatic Amino Acid Studies

Date: December 1970
Creator: Sullivan, Patrick Timothy
Description: Pyridine ring analogs of the aromatic amino acids phenylalanine and tyrosine were synthesized and studied in microbiological and mammalian systems.
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Biological Inhibitors

Biological Inhibitors

Date: December 1971
Creator: Sargent, Dale Roger
Description: Four isosteric series of plant growth-regulating compounds were prepared. Using an Avena sativa coleptile assay system, derivatives in series I and IV inhibited segment elongation to a greater degree than did comparable derivatives in series II and III.
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Bonding Studies in Group IV Substituted n,n-dimethylanilines

Bonding Studies in Group IV Substituted n,n-dimethylanilines

Date: December 1971
Creator: Drews, Michael James
Description: The purpose of the present work is to study the effects of the trimethylsilyl and trimethylgermyl substituents on the N,N-dimethylamino ring system. Both ground and excited state interactions were studied and their magnitudes determined. The experimental data were then used in conjunction with molecular orbital calculations to differentiate among, and determine the importance of, d-p bonding, hyperconjugation or polarization of the trimethylsilyl group on the ground and excited state bonding.
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Characterization of Low Barrier Hydrogen Bonds in Enzyme Catalysis: an Ab Initio and DFT Investigation

Characterization of Low Barrier Hydrogen Bonds in Enzyme Catalysis: an Ab Initio and DFT Investigation

Date: August 1999
Creator: Pan, Yongping
Description: Hartree-Fock, Moller-Plesset, and density functional theory calculations have been carried out using 6-31+G(d), 6-31+G(d,p) and 6-31++G(d,p) basis sets to study the properties of low-barrier or short-strong hydrogen bonds (SSHB) and their potential role in enzyme-catalyzed reactions that involve proton abstraction from a weak carbon-acid by a weak base. Formic acid/formate anion, enol/enolate and other complexes have been chosen to simulate a SSHB system. These complexes have been calculated to form very short, very short hydrogen bonds with a very low barrier for proton transfer from the donor to the acceptor. Two important environmental factors including small amount of solvent molecules that could possibly exist at the active site of an enzyme and the polarity around the active site were simulated to study their energetic and geometrical influences to a SSHB. It was found that microsolvation that improves the matching of pK as of the hydrogen bond donor and acceptor involved in the SSHB will always increase the interaction of the hydrogen bond; microsolvation that disrupts the matching of pKas, on the other hand, will lead to a weaker SSHB. Polarity surrounding the SSHB, simulated by SCRF-SCIPCM model, can significantly reduce the strength and stability of a SSHB. The residual strength ...
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Chemical Equilibria in Binary Solvents

Chemical Equilibria in Binary Solvents

Date: August 1997
Creator: McHale, Mary E. R.
Description: Dissertation research involves development of Mobile Order Theory thermodynamic models to mathematically describe and predict the solubility, spectral properties, protonation equilibrium constants and two-phase partitioning behavior of solutes dissolved in binary solvent mixtures of analytical importance. Information gained provide a better understanding of solute-solvent and solvent-solvent interactions at the molecular level, which will facilitate the development of better chemical separation methods based upon both gas-liquid and high-performance liquid chromatography, and better analysis methods based upon complexiometric and spectroscopic methods. Dissertation research emphasizes chemical equilibria in systems containing alcohol cosolvents with the understanding that knowledge gained will be transferable to more environmentally friendly aqueous-organic solvent mixtures.
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