You limited your search to:

  Partner: UNT Libraries
 Department: Department of Chemistry
 Decade: 1990-1999
 Collection: UNT Theses and Dissertations
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 ...
Contributing Partner: UNT Libraries
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.
Contributing Partner: UNT Libraries
Aluminum and Copper Chemical Vapor Deposition on Fluoropolymer Dielectrics and Subsequent Interfacial Interactions

Aluminum and Copper Chemical Vapor Deposition on Fluoropolymer Dielectrics and Subsequent Interfacial Interactions

Date: December 1997
Creator: Sutcliffe, Ronald David
Description: This study is an investigation of the chemical vapor deposition (CVD) of aluminum and copper on fluoropolymer surfaces and the subsequent interfacial interactions.
Contributing Partner: UNT Libraries
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.
Contributing Partner: UNT Libraries
An Approach Towards the Total Synthesis of Clonostachydiol

An Approach Towards the Total Synthesis of Clonostachydiol

Date: August 1995
Creator: Maiti, Tushar B. (Tushar Baran)
Description: The syntheses of the unsymmetrical 14-membered bismacrolides have been reviewed. A total synthesis of clonostachydiol, the latest to join this family, has been attempted using trimethylsilyl acetylene as the builiding block and palladium catalyzed reactions for the formation of key bonds. The alkyne groups were introduced by Stille coupling of trimethylstannylethynyltrimethylsilane with an acid chloride for one fragment and by addition of lithiotrimethylsilyl acetylene to an aldehyde for the other. Lactic acid derivatives were chosen as starting materials for both fragments, thus introducing two of the chiral centers. The remaining stereocenters were introduced using stereoselective reductions of ketones.
Contributing Partner: UNT Libraries
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 ...
Contributing Partner: UNT Libraries
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.
Contributing Partner: UNT Libraries
Combined Electrochemistry and Spectroscopy of Complexes and Supramolecules containing Bipyridyl and Other Azabiphenyl Building Blocks

Combined Electrochemistry and Spectroscopy of Complexes and Supramolecules containing Bipyridyl and Other Azabiphenyl Building Blocks

Date: August 1995
Creator: Yang, Lei
Description: A group of azabiphenyl complexes and supramolecules, and their reduced and oxidized forms when possible, were characterized by cyclic voltammetry and electronic absorption spectroscopy. The oxidized and reduced species, if sufficiently stable, were further generated electrochemically inside a specially designed quartz cell with optically transparent electrode, so that the spectra of the electrochemically generated species could be taken in situ. Assignments were proposed for both parent and product electronic spectra. Species investigated included a range of Ru(II) and Pt(II) complexes, as well as catenanes and their comparents. Using the localized electronic model, the electrochemical reduction can be in most cases assigned as azabiphenyl-based, and the oxidation as transition metal-based. This is consistent with the fact that the azabiphenyl compounds have a low lying π* orbital. The electronic absorption spectra of the compounds under study are mainly composed of π —> π* bands with, in some cases, charge transfer bands also.
Contributing Partner: UNT Libraries
Computer Simulations of Dilute Polymer Solutions: Chain Overlaps and Entanglements

Computer Simulations of Dilute Polymer Solutions: Chain Overlaps and Entanglements

Date: August 1996
Creator: Drewniak, Marta
Description: Chain conformations and the presence of chain overlaps and entanglements in dilute polymer solutions have been analyzed. The fundamental problem of existence of chain overlaps in dilute solutions is related to the drag reduction phenomenon (DR). Even though DR occurs in solutions with the concentration of only few parts per million (ppm), some theories suggest that entanglements may play an important role in DR mechanism. Brownian dynamics technique have been used to perform simulations of dilute polymer solutions at rest and under shear flow. A measure of interchain contacts and two different measures of entanglements have been devised to evaluate the structure of polymer chains in solution. Simulation results have shown that overlaps and entanglements do exist in static dilute solutions as well as in solutions under shear flow. The effect of solution concentration, shear rate and molecular mass have been examined. In agreement with the solvation theory of DR mechanism, simulation results have demonstrated the importance of polymer + polymer interactions in dilute solutions.
Contributing Partner: UNT Libraries
The Development of Predictive Models for the Acid Degradation of Chrysotile Asbestos

The Development of Predictive Models for the Acid Degradation of Chrysotile Asbestos

Date: May 1993
Creator: Ingram, Kevin D. (Kevin Dean)
Description: The purpose of this study was to determine the factors affecting the acid degradation of chrysotile asbestos (Mg_3Si_2O_5(OH_4)) . Millions of tons of asbestos have found use in this country as insulative or ablative material. More than 95 percent of the asbestos in use is of the chrysotile variety. The remaining 5 percent is composed of various types of fibrous amphiboles. The inhalation of asbestos can lead to several diseases in humans. Asbestosis, lung cancer and mesothelioma are the most common afflictions associated with asbestos inhalation, and they may occur up to 40 years after the initial exposure. It has previously been reported that if more than 50 percent of the magnesium is removed from a chrysotile sample its carcinogenicity is reduced to nil. Several inorganic acids were studied to determine their ability to leach magnesium from chrysotile. It was found that the ability to leach magnesium was dependent upon the acidic anion in addition to the concentration of the acid. The ordering of the efficiency of the acids in their ability to remove magnesium from chrysotile was found to be HCl > H_2SO_4 > H_3PO_4 > HNO_3. Predictive equations were developed to allow the calculation of the amount of ...
Contributing Partner: UNT Libraries
FIRST PREV 1 2 3 4 5 NEXT LAST