The plasma anodization of polycrystalline niobium samples has been undertaken using a d.c. glow discharge in oxygen. The apparatus used, which has facilities for in situ ellipsometry measurements and sample temperature control, is described. Anodizations were carried out at various constant current densities up to 1.5 mA cm⁻² , and Langmuir probes were used to estimate the volt drop across the oxide during growth. The ellipsometry measurements yield oxide thickness and refractive index, and indicate that the films have a two-layer structure. Ionic currents are calculated from growth rates using Faraday's Law. Ionic current and oxide field strength data are analyzed and compared with published solution anodization results on the basis of the classical model of ionic conduction at high field strengths. The permittivity and loss factor of the oxide films are deduced from bridge measurements on capacitor structures produced by depositing counterelectrodes on the oxide surface. The introduction of water into the discharge was investigated, and found to affect the oxide growth rate. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

Thesis (Ph. D.)--Lehigh University, 2001. / Includes bibliographical references and vita.

Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references [p. 133-146) Also available via World Wide Web.

Thesis (M.S.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2005. Directed by Christopher Summers. / Summers, Christopher, Committee Chair ; Snyder, Robert, Committee Member ; Wang, Zhong Lin, Committee Member. Includes bibliographical references.

Thesis (M.Sc.)--City University of Hong Kong, 2005. / At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.

Thesis (M.Sc.)--City University of Hong Kong, 2005. / At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.

The development of materials for optical thin film application is essential to progress in fields such as optical data storage and signal processing. Samarium sulfide (SmS) thin films were prepared by reactive evaporation of samarium in hydrogen sulfide (H₂S). These displayed optical switching properties despite the presence of large amounts of carbon and oxygen. They are therefore potentially useful for data storage. The semiconductor to metal phase transition was characterized by x-ray diffraction and spectrophotometry. The observed optical response was modelled by a Bruggeman effective medium calculation. Success with this analysis suggests it as a means for predicting performance in subsequent applications. Zinc sulfide (ZnS) thin films were prepared by molecular beam epitaxy (MBE). Implimentation of an H₂S treated silicon surface provided good chemical bond match in addition to a good lattice match. Atomic layer epitaxy was unsuccessfully explored as a means to grow ZnS from zinc and H₂S reactants, therefore other reactants are proposed. Both the MBE and ALE work is directed at the long term goals of producing p-type ZnS, which is suitable for semiconductor lasing at short wavelengths, and high quality SmS thin films.

Materials in the form of thin films that have been deposited from the vapor phase are significantly different from similar bulk materials, both optically and mechanically, because of their columnar structure and consequent porosity. Their porosity have been verified in different ways. The effects of the pores on optical and mechanical performance and, in particular, the influence of water adsorption, have also been demonstrated. Three techniques used for investigating optical instabilities in thin films are given. They all involve sharp resonances. The resonances are associated either with surface plasmons, metal-dielectric narrowband filters, or all dielectric narrowband filters. These resonances are very sensitive functions of layer properties and hence can be used to detect and measure changes in the layers, particularly those that are induced by adsorption of moisture. Moisture adsorption in thin films is a complex process that occurs unevenly in patches. Using resonance techniques, the adsorption isotherms of change in refractive index, of growth rate in patch size, and of peak wavelength shift, which are all important in characterizing the porosity of films, have been measured. Some effects that locally increase film porosity and create central pores that permit water to penetrate into multilayer structures have been investigated. Based on these results, some suggestions for preventing water adsorption in films are then made. Moisture penetration into thin film structures is the major source of optical coating instability and it is therefore very important that the mechanisms of penetration by understood. Some deductions of the mechanisms are made from the experimental results.

We established measurement and analysis techniques necessary to investigate the optical properties of some transition metal compounds: specifically the carbides and nitrides of Ti, Zr, and Hf. Two distinct techniques determined the optical constants of these films: a Nestell-Christy method to invert measurements of thickness, reflection, and transmission and a Kramers-Kronig analysis of reflection. The compositions of the samples were evaluated by X-ray diffraction, Auger spectroscopy, scanning electron microprobe analysis, and nuclear analysis. We found it possible to correlate these materials' optical and electronic properties and relate these to compositional changes. The ability to engineer a specific optical response of materials is discussed. Additions of carbon and nitrogen change the optical properties in a specific manner; the roles of these elements as electron donors and their effect on the location and population of the d electron bands with respect to the Fermi level are postulated.