Browsing by Subject "ALD"

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    Group 13 Metal Doping of Cadmium Selenide Nanocrystals and Atomic Layer Deposition of Copper Oxide and Copper Aluminum Oxide
    (2017-05) Halverson, Joshua
    Semiconductors are a broad class of materials and by extension present a large array of possibilities for potential research. This thesis looks at two different areas of semiconductor research. The first is electronic doping of semiconductor nanocrystals and the second is the deposition of copper aluminum oxide via atomic layer deposition (ALD). Semiconductor nanocrystals are semiconductor particles with diameters less than 10 nm. At these size ranges, semiconductor nanocrystals display several unique electrical and optical characteristic due to quantum confinement. Quantum confinement is a phenomenon that arises when the physical size of the nanocrystal is smaller than the wavefunction size of the electrons and holes that allow electrical conductivity in semiconductors. These quantum confinement effects are tunable based on the size of the nanocrystal, which allows one material to have a broad range of possible uses. Even greater control could be had if semiconductor nanocrystals could be doped with heterovalent dopants, as is seen in traditional semiconductors. This thesis look at incorporating group 13 dopants into cadmium selenide nanocrystals and found that while the dopants had effects on the electronic structure of the nanocrystals they were not successfully incorporated into the nanocrystals. The dopants instead were bound to the surface of the nanocrystal. Copper aluminum oxide has generated interest as a potential p-type transparent conductive oxide. Thin films of this material have been deposited via physical vapor methods. Depositing this material via ALD provides a great level of film thickness control, which is critical in many thin film devices. Deposition of copper containing films via ALD has been hampered by a lack of suitable copper precursor. As a solution to that problem, this thesis demonstrates the construction of an ALD deposition system that can use both solid and liquid ALD precursors. This system with its extended capabilities was then used to deposit thin films of copper aluminum oxide using solid copper precursors.
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    Understanding cominatorial atomic layer deposition and chemical vapor deposition.
    (2009-01) Moersch, Tyler Leighton
    The transformation of molecular precursor to solid film begins with an understanding of molecular structure, proceeds through delivery of the molecule to the surface and ends with the decomposition of precursor on the surface to form a deposit. An understanding of the physical and chemical processes leading from molecule to film enables the utilization of chemical precursors in effective deposition processes. Single crystal X-ray crystallography was used to study the structure of [NO]0.5[NO2]0.5[Zr(NO3)5] and [NO]0.5[NO2]0.5[Hf(NO3)5]. Infrared spectroscopy was employed to identify the nature of the cation in the crystal structure, and characteristic absorptions of both nitronium and nitrosonium cations were observed. Fluidized bed reactor technology has been used to study the sublimation behavior of solid-state chemicals. Fluidization behavior, precursor mass transfer rates and delivery uniformity for aluminum trichloride were studied and the results reported. Mixed metal oxide nanolaminate films of hafnium oxide and zirconium oxide interspersed with layers of silicon oxide have been deposited on silicon substrates by a combinatorial atomic layer deposition (ALD) technique. Exposure of repeated cycles of co-dosed alkoxide precursors Hf[OC(CH3)3]4 and Zr[OC(CH3)3]4 with counter-reactant pulses of Si[OC(CH3)3]3(OH) formed films of uniform thickness (±5%) and uniform silicon oxide concentration (85% per total metals basis). The hafnium and zirconium concentrations exhibited smooth gradation across the film from 18% - 82% (per Hf and Zr metals basis). Self-limiting deposition rates of 1.5 nm / cycle were measured, and a linear relationship of film thickness to number of deposition cycles was observed, both consistent with a true ALD process. Rutherford backscattering spectrometry, ellipsometry and X-ray reflectivity results were used to map the composition and determine the film microstructure. Single precursor depositions have been performed and compared to computational models created using CFD-ACE in order to further the understanding of the interaction of fluid dynamics and chemistry in the combinatorial chemical vapor deposition process. The physical and chemical processes contributing to film growth in combinatorial chemical vapor deposition were evaluated.