Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 147-151). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Deng,Yulin; Committee Member: Hsieh, Jeffery S.; Committee Member: Nair, Sankar; Committee Member: Singh, Preet; Committee Member: Yao, Donggang. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2010. / Committee Chair: Orlando, Thomas; Committee Member: El-Sayed, Mostafa; Committee Member: First, Phillip; Committee Member: Lackey, Jack; Committee Member: Tolbert, Laren. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Chemical vapor deposition is a process that enables the deposition of thin films material with a high degree of thickness control, composition and film quality. In an ultra-high vacuum environment (UHV), films of high purity and controlled crystal structure can be achieved. The control of the crystal structure is achieved thanks to reduced contamination, e.g. oxygen, which allows the grown film to align itself with the underlying substrate. The film purity is also ensured by the reduced amount of contaminants present in the UHV environment. This master’s thesis discusses the design and construction of a cold wall reactor using a pyrolytic graphite heater encased in a thin layer of pyrolytic boron nitride, and an Oerlikon-Leybold Turbovac 361 turbomolecular pump. This heater is shown to achieve temperatures greater than 1200°C, as well as reach pressures in the 10-10 Torr range. Graphene growth on copper is discussed as well as the ultra-high vacuum annealing of graphene devices on boron nitride substrates. The graphene growth experiments coupled with this system’s annealing capabilities demonstrate the functionality and versatility of this type of chemical vapor deposition system. / text

With the growing demand for miniaturization of devices and for new materials with useful properties, the use of Chemical Vapor Deposition (CVD) for the manufacture of thin films is receiving growing attention. The synthesis of potentially volatile metal complexes and investigation of their use as CVD precursors is an important part of this process. The research presented addresses several major areas of this process, (i) the identification and synthesis of ligands which can impart volatility to a metal complex, (ii) the synthesis, characterization, and assessment of volatility of metal complexes containing these ligands, and (iii) the full materials characterization of thin films grown with these complexes. The use of trimethylphosphine, bis(trifluoromethyl)pyrazolate, and bis(trifluoromethyl)pyrrolyl ligands have been successfully used to synthesize volatile new complexes of cobalt, rhodium, and nickel, some of which show promise for use as potential CVD precursors. / text

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Cubic boron nitride (c-BN) has been in focus for several years due to its interesting properties. The possibility for large area chemical vapor deposition (CVD) is a requirement for the realization of these different properties in various applications. Unfortunately, there are at present severe problems in the CVD growth of c-BN. The purpose with this research project has been to theoretically investigate, using density functional theory (DFT) calculations, the possibility for a layer-by-layer CVD growth of c-BN.  The results, in addition with experimental work by Zhang et al.57,  indicate that plasma-enhanced atomic layer deposition (PEALD), using a BF3-H2-NH3-F2 pulse cycle and a diamond substrate, is a promising method for deposition of c-BN films. The gaseous species will decompose in the plasma and form BFx, H, NHx, and F species (x = 0, 1, 2, 3). The H and F radicals will uphold the cubic structure by completely hydrogenate, or fluorinate, the growing surface. Surface radical sites will appear during the growth process as a result of atomic H, or F, abstraction reactions. However, introduction of energy (e.g., ionic bombardment) is probably necessary to promote removal of H from the surface. The addition of NHx growth species (x = 0, 1, 2) to the B radical sites, and BFx growth species (x = 0, 1, 2) to N radical sites, will then result in a continuous growth of c-BN.

Currently the cost of solar grade silicon accounts for approximately one third of the total solar cell cost, therefore a new silicon refining process is being proposed with the goal of lowering the cost of producing solar grade silicon. In this new process, Si-Cu alloys were used as the silicon source. One to one molar ratio H2-HCl gas mixtures were used as transport agents to extract Si out from the Si-Cu alloy at about 300-700oC, with following reaction taking place: Si+3HCl(g)=HSiCl3(g)+H2(g) While at about 1000-1300oC, pure Si deposits onto a hot silicon rod according to: Si+3HCl(g)=HSiCl3(g)+H2(g) The role of the copper in the alloy was to trap impurities in the Si and catalyze the gas solid reaction. A study on determining the rate limiting step and impurity behavior was done. A possible silicon extraction reaction mechanism was also addressed.

Currently the cost of solar grade silicon accounts for approximately one third of the total solar cell cost, therefore a new silicon refining process is being proposed with the goal of lowering the cost of producing solar grade silicon. In this new process, Si-Cu alloys were used as the silicon source. One to one molar ratio H2-HCl gas mixtures were used as transport agents to extract Si out from the Si-Cu alloy at about 300-700oC, with following reaction taking place: Si+3HCl(g)=HSiCl3(g)+H2(g) While at about 1000-1300oC, pure Si deposits onto a hot silicon rod according to: Si+3HCl(g)=HSiCl3(g)+H2(g) The role of the copper in the alloy was to trap impurities in the Si and catalyze the gas solid reaction. A study on determining the rate limiting step and impurity behavior was done. A possible silicon extraction reaction mechanism was also addressed.

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