Brian Keith Peterson

A computational study of calcium cation locations and diffusion in chabazite

Abstract The characteristics of calcium ions in high-silica chabazite are explored by treating the aluminium and calcium ions as a defect in an otherwise purely siliceous bulk with the defect modelled using the Mott–Littleton method. Three generic sites are found for calcium, which correspond to the centre of the double six-ring unit, on the triad axis of the double six-ring unit but displaced into the cavity and in the eight-ring window. Distortion of the framework is also examined. The main energetic barriers to cation migration are found. As expected these are large in relation to kT , even at elevated temperatures, and significant diffusion of the cations can be ruled out for anhydrous chabazite.

Electrochemical and Spectroscopic Investigations of the Overcharge Behavior of StabiLife Electrolyte Salts in Lithium-Ion Batteries

Electrochemical and spectroelectrochemical studies were conducted to understand the fundamental processes that occur during the overcharge of lithium-ion batteries with electrolyte solutions containing the StabiLife electrolyte salt (Li 2 B 12 F 12 )- Cyclic voltammetric experiments on these electrolyte solutions show well defined, quasi-reversible oxidation and reduction peaks with an onset potential of 4.6-4.9 V, depending upon the dielectric constant of the electrolyte. When oxidized in organic electrolytes, commonly used in lithium-ion batteries, Li 2 B 12 F 12 forms the stable, pale yellow B 12 F 1- * 12 radical anion. This is confirmed in solution by in situ electron paramagnetic resonance measurements. The overcharge chemistry of the StabiLife electrolyte salts was further probed in full cell configurations with mesocarbon microbeads as an anode and LiCoO 2 as a cathode. A Li metal reference electrode was incorporated to monitor the voltage changes associated with both the anode and the cathode during overcharge. Overcharge in cells based on LiPF 6 electrolytes very rapidly leads to cell potentials >5.5 V, while similar cells containing Li 2 B 12 F 12 based electrolytes exhibit stable voltage holding at ~4.7 V. X-ray photoelectron spectroscopy analysis confirms that massive lithium plating has occurred in the LiPF 6 -based cells. Evidence of only trace lithium plating is observed in Li 2 B 12 F 12 -based cells. A plausible mechanism for the reductive completion of the redox shuttle is proposed.

Impact of Pore Size and Morphology of Porous Organosilicate Glasses on Integrated Circuit Manufacturing

Porous organosilicate materials produced by plasma enhanced chemical vapor deposition are the leading candidates for back-end-of-line dielectric insulators for IC manufacturing at 45nm design features and beyond. The properties of porous organosilicate glass films of dielectric constant k=2.50 ± 0.05 formed using diethoxymethylsilane and five different porogen precursors with an ultraviolet post treatment are reported. By varying the porogen precursor type pore sizes of 1-2 nm (equivalent spherical diameter) and porosities in the range of 24-31% were measured. While there were no observable trends in pore size with the molecular volume or plasma reactivity of the porogen precursor, modulus values ranged from 6.6 to 10.8 GPa. Porous films with the highest mechanical properties were found to have the highest matrix dielectric constant, highest network connectivity (lowest methyl content), and highest density. Within this process space, maximizing the network connectivity of the film was found to be more important to mechanical properties than lowering the total porosity. In effect, the choice of porogen precursor dictates the film morphology through its impact on the organosilicate glass matrix and pore size.

Plasma Enhanced Chemical Vapor Deposition of Porous Organosilicate Glass ILD Films With k ≤ 2.4.

We report on our work to develop a process for depositing nanoporous organosilicate (OSG) films via plasma enhanced chemical vapor deposition (PECVD). This approach entails codepositing an OSG material with a plasma polymerizable hydrocarbon, followed by thermal annealing of the material to remove the porogen, leaving an OSG matrix with nano-sized voids. The dielectric constant of the final film is controlled by varying the ratio of porogen precursor to OSG precursor in the delivery gas. Because of the need to maintain the mechanical strength of the final material, diethoxymethylsilane (DEMS) is utilized as the OSG precursor. Utilizing this route we are able to deposit films with a dielectric constant of 2.55 to 2.20 and hardness of 0.7 to 0.3 GPa, respectively.

Computational-chemical assessments of well characterised uniform catalysts

The use of computer-simulation procedures to model the behaviour of zeolites and other well characterised, uniform catalysts is discussed. We describe the prediction of the location of solute molecules and the estimation of heats of adsorption by molecular mechanics (MM) procedures. In addition, the use of Monte Carlo (MC) and molecular dynamics (MD) techniques to study sorbates at high loadings is considered, together with the calculation of diffusion coefficients by MD. The assessment of the stability of known and hypothetical zeolites by lattice-simulation procedures is described and we explore the extension of the method to pillared clays. The possibility of modelling a catalytic reaction mechanism by quantum-mechanical procedures is also examined.

Optimized Materials Properties for Organosilicate Glasses Produced by Plasma-Enhanced Chemical Vapor Deposition

In this paper we examine the relationship between precursor structure and material properties for films produced from several leading organosilicon precursors on a common processing platform. Results from our study indicate that for the precursors tested the nature of the precursor has little effect upon film composition but significant impact on film structure and properties. Introduction There are a variety of materials being considered for the next generation interlayer dielectric (ILD) materials. The leading candidates for the 90nm generation are organosilicate glasses produced by Plasma-Enhanced Chemical Vapor Deposition (PECVD). Providing materials with extendibility beyond a single generation solution requires the optimization of both electrical and mechanical properties. These are competing goals since concomitant with reducing the dielectric constant (k) is, in general, a decrease in the mechanical strength of a material. The goal of this work is to build a better understanding of the structure of low k dielectric films deposited from a PECVD process. In attempts to elucidate structureproperty relationships for OSG precursors we assessed a variety of chemicals including those used in various commercial product offerings. Experimental All experiments were performed on an Applied Materials Precision 5000 fitted with a 200mm DxZ chamber. Every attempt was made to optimize process regimes for each precursor to provide the best mechanical properties at a given dielectric constant (k). Films were analyzed for refractive index and thickness with a SCI FilmTek 2000 reflectometer calibrated daily. Electrical tests were performed on low resistivity wafers ( 20 ohm-cm) using a Thermo Nicolet 750 at 4 cm resolution, nitrogen purged cell and background corrected with Si. Selected samples were analyzed using Carbon-13 and Silicon-29 Nuclear Magnetic Resonance (NMR). Density Molecule Si–CH3:Si Si–O:Si Si–H:Si Structure