The growth and characterization of epitaxial thin films see ubiquitous use in both research and applications spanning a number of scientific and industrial fields with overlapping interests in materials science. The central theme of this work centers on leveraging the structural control afforded through the ultrahigh vacuum (UHV) approaches to thin-film epitaxy to derive atomically specific structure-chemistry relationships of key importance to various interface-mediated reactions. The first project was aimed at developing gold (Au) and ceria (CeO2) thin films using advanced surface-science techniques. In that project, a thoroughly wetted Au film on Ta metal substrate has been identified. This model system is necessary due to its potential candidacy as a promising electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cell cathodes. The second film is CeO2(100), grown on a silver (Ag) single crystal substrate. Cerium oxide is a fascinating material with unique properties and has applications in many fields. The (100) plane of ceria is particularly interesting because it is the most active plane among the low index planes. Here in-situ growth of ceria islands on Ag has been reported. The second project is related to a detailed exploration of efforts undertaken to better understand key structure-chemistry relationships central to water cycling processes relevant to the continual evolution of the Lunar surface under the influence of Solar wind interactions. This project has been discussed in two parts - the first part shows the results from D2O temperature programmed desorption (TPD) studies conducted on single-crystalline AlxSiyO2/Ru(0001) bilayer films used to simulate surface properties expected at Feldspar interfaces. This discussion, which aids in the disambiguation of a standing discrepancy in the surface science and zeolite communities, lead to a key postulate linking the nature of the charge-compensating species present in different [A+]x-AlySizO2 mineralogical structures to the barrier for deprotonation via recombinative desorption of water and the lower temperature persistence of molecular water at temperatures relevant to the daytime environment of the lunar surface at different latitudes. A follow-up study demonstrates practical implications of this postulated relationship on realistic anorthite and albite end members of the plagioclase series of Feldspars, with anorthite (albite) exhibiting stronger (weaker) barriers to recombinative desorption of water via deprotonation of isolated hydroxyl groups.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Dhar, Bijoya, "Development and Surface Science Investigations of Epitaxial Thin Films Suitable for Elucidating Mechanisms of Water Formation and Migration on the Moon" (2021). Electronic Theses and Dissertations, 2020-. 950.