Suspended titanium dioxide (TiO2) nanoparticles produce hydroxyl radicals (•OH) that synergistically aid in disinfection when irradiated with UV light. To exploit the benefits of TiO2 photocatalysis without having to remove them, TiO2 was deposited onto 3M Company’s nanostructured thin film (NSTF). •OH production by suspended and TiO2-NSTF was determined by para-chlorobenzoic acid (pCBA), a •OH probe compound. Both techniques of introducing TiO2 to the samples produced equivalent •OH without forming bromate, a regulated byproduct in drinking water at all UV and TiO2 levels. Formation of bromate by ozone in brackish water and seawater were used to compare the disinfection byproduct (DBP) formation between the disinfection methods. Additionally, monitoring bromate, typically performed by ion chromatography, is complicated by chloride and other anions present in brackish water or seawater. Thus, a spectrophotometric method to measure bromate in saline systems is introduced.

A novel method to detect and quantify the growth of the solid electrolyte interphase (SEI) on battery electrode materials using in-situ spectroscopic ellipsometry (SE) is presented. The effects of additives in 1 M LiPF6/EC:DEC (1:2) electrolyte on the SEI were studied. Thin film electrodes of a-Si, Ni, and TiN were prepared by magnetron sputtering for use with a custom-designed tubular in-situ electrochemical cell. Li/a-Si and Li/Ni in-situ cells in 0.1 M LiPF6/EC:DEC (1:2) were studied by galvanostatic chronopotentiometry. Large changes in the ellipsometric parameters, ? and ?, were observed for both materials. These changes were closely related to the state of charge of the in-situ cell. The formation of an a-LixSi alloy, the formation of an SEI layer, or both contributed to these large changes for a Li/a-Si in-situ cell. For a Li/Ni in-situ cell, a thin transparent surface layer was observed. The surface layer, presumably made from SEI species and species from the displacement reaction between NiO and Li, increased to roughly 17 nm during the first discharge. During the first charge, the surface layer thickness decreased to roughly 5.5 nm and could not be removed, even at high potentials. The effect of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) additives on SEI formation were studied using a Li/TiN in-situ cell in 1 M LiPF6/EC:DEC (1:2) by potentiostatic chronoamperometry. SEI thicknesses for cells containing no additives, VC, and FEC were roughly 18 nm, 25 nm and 30 nm, respectively, after a 10 h hold at 0.1 V. SE is a useful technique for measuring thin film growth in-situ on electrode materials for Li-ion batteries.

Detailed magnetometry and polarized neutron reflectometry studies were conducted on MnSi thin films grown epitaxially on Si(111) substrates. It is demonstrated that with an in-plane applied field H || [110], a broadly stable skyrmion phase exists at elevated temperatures and fields. Magnetometry and transport measurements with an out-of-plane applied field H || [111] prove that no skyrmion phase exists in this geometry. However, Hall effect measurements in this geometry show unexpected evidence of a topological Hall effect. This can be explained with a multi-dimensionally modulated cone phase, which proves that contrary to recent literature, a topological Hall effect is not sufficient proof of skyrmions. The results of this thesis represent a significant step towards a technologically relevant material in which skyrmions are broadly stable. A material of this type could be used in novel magnetic storage devices and signi ficantly impact our future computing capabilities.

Diamond is widely known for its extraordinary properties, such as high hardness, thermal conductivity, electron mobility, energy bandgap and durability making it a very attractive material for many applications. Synthetic diamonds retain most of the attractive properties of natural diamond. Among the types of synthetic diamonds, nanocrystalline diamond (NCD) is being developed for electrical, tribological, optical, and biomedical applications. In this research work, NCD films were grown by the pulsed electron beam ablation (PEBA) method at different process conditions such as accelerating voltage, pulse repetition rate, substrate material and temperature. PEBA is a relatively novel deposition technique, which has been developed to provide researchers with a new means of producing films of equal or better quality than more conventional methods such as Pulsed Laser Deposition, Sputtering, and Cathodic Vacuum Arc. The deposition process parameters have been defined by estimating the temperature and pressure of the plasma particles upon impact with the substrates, and comparing the data with the carbon phase diagram. Film thickness was measured by visible reflectance spectroscopy technique and was in the range of 40 – 230 nm. The nature of chemical bonding, namely, the ratio (sp3/sp3+sp2) and nanocrystallinity percentage were estimated using visible Raman spectroscopy technique. The films prepared from the ablation of a highly ordered pyrolytic graphite (HOPG) target on different substrates consisted mainly of nanocrystalline diamond material in association with a diamond-like carbon phase. The micro-structural properties and surface morphology of the films were studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The mechanical properties of the NCD films were evaluated by nano-indentation.

Atomic vapors condensed onto solid surfaces form a remarkable category of condensed matter materials, the so-called thin films, with a myriad of compositions, morphological structures, and properties. The dynamic process of atomic condensation exhibits self-assembled pattern formation, producing morphologies with atomic-scale three-dimensional structures of seemingly limitless variety. This study attempts to shed new light on the dynamical growth processes of thin film deposition by analyzing in detail a previously unreported specific distinct emergent structure, a crystalline triangular-shaped spike that grows within copper and silver thin films. I explored the deposition parameters that lead to the growth of these unique structures, referred to as ``nanospikes'', fabricating approximately 55 thin films and used scanning electron microscopy and x-ray diffraction analysis. The variation of parameters include: vapor incidence angle, film thickness, substrate temperature, deposition rate, deposition material, substrate, and source-to-substrate distance. Microscopy analysis reveals that the silver and copper films deposited at glancing vapor incidence angles, 80 degrees and greater, have a high degree of branching interconnectivity between adjacent inclined nanorods. Diffraction analysis reveals that the vapor incidence angle influences the sub-populations of crystallites in the films, producing two different [110] crystal texture orientations. I hypothesize that the growth of nanospikes from nanorods is initiated by the stochastic arrival of vapor atoms and photons emitted from the deposition source at small diameter nanorods, and then driven by localized heating from vapor condensation and photon absorption. Restricted heat flow due to nanoscale thermal conduction maintains an elevated local temperature at the nanorod, enhancing adatom diffusion and enabling fast epitaxial crystal growth, leading to the formation and growth of nanospikes. Electron microscopy and x-ray diffraction analysis, and comparisons to related scientific literature, support this hypothesis. I also designed a highly modular ultrahigh vacuum deposition chamber, capable of concurrently mounting several different pieces of deposition equipment, that allows for a high degree of control of the growth dynamics of deposited thin films. I used the newly designed chamber to fabricate tailor-made nanostructured tantalum films for use in ultracapacitors, for the Cabot Corporation. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2011-01-17 15:22:47.533

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Modification of planar graphitic carbon surfaces by the attachment of molecular films has been investigated in this work. Molecular layers have been grafted to glassy carbon (GC) and pyrolyzed photoresist film (PPF) by employing a range of techniques, which involved electrochemically and photochemically assisted procedures. Modification methods involve the electrochemical reduction of aryldiazonium salt, electrochemical oxidation of arylcarboxylate and photolysis of alkene, alkyne and azide on carbon surfaces. For these methods, it is proposed that reactive species are generated by the procedures, which leads to the grafting of modifiers to the carbon surfaces. A selection of molecular species was grafted to GC and PPF by these method containing different terminal R-functional groups that include —COOH, -NO₂, -NH₂, and —NCS. The grafted R-functional groups permit for further chemical reactions on the surface. Electrochemically and photochemically grafted films were examined with a combination of water contact angle measurements, cyclic voltammetry, X-ray electron spectroscopy XPS, optical microscopy, scanning electron microscopy SEM and atomic force microscopy AFM. Film properties such as surface concentration, film thickness, wettability, chemical composition and reactivity were characterized by the above mentioned techniques. Films electrochemically prepared from aryldiazonium salts and arylcarboxylates, under the conditions applied in this work, formed loosely packed multilayers with typical film thicknesses of les than 5 nm. Photochemically grafted films prepared from alkenes and azides, in general, formed loosely packed monolayers with film thicknesses of less than 2 nm. Loosely packed multilayers were also prepared from alkene and alkyne by photochemical procedures. ii Chemical reactions on grafted films were demonstrated and analyzed by a combination of the above mentioned characterization techniques. In particular, the reduction of nitrophenyl (NP)films, amine-coupling reactions, photoactivation of grafted films with oxalyl chloride and electrostatic assembly of anionic gold nanoparticles were investigated. Selected chemical reactions permitted identification and evaluation of the grafted layers, and demonstrated the ability to control the immobilization of chemical species. Microscale chemical patterning of two different types of modifiers on carbon surfaces was demonstrated using photolithographical techniques that utilized photochemical reactions with azides. Patterns of line-arrays with line widths of hundreds of micrometers to 10 µm were formed.

Piezoelectric bimorph thin films may hold solutions for many future applications, such as lightweight deployable mirrors and inflatable struts. Non-contact actuation by an electron gun has shown promise in preventing issues that arise from attaching many wire leads to a thin film surface. This study investigates piezoelectric bimorph thin film response to electron gun actuation when covered with multiple spatial regions of control. Desired parameter ranges are found that will lead to predictable control under certain circumstances. Under such circumstances, film response is influenced almost solely by the primary electrons incident on the film, and secondary electrons have negligible effect. Such information is vital before attempting closed loop control of a thin-film piezoelectric mirror with multiple electrodes.

CIGS thin film solar cells usually include a thin layer of intrinsic zinc oxide (i-ZnO) deposited on a CdS buffer layer by sputtering. However an interest has grown in using chemical vapor deposition (CVD) instead. Hence, the aim of this thesis was to study how well CVD i-ZnO performs on a CdS buffer layer in a CIGS solar cell and how the properties of the layer can be controlled when using a hot-wall CVD reactor with diethylzinc and water as precursors. The process was characterized through depositions on glass substrates and was then successfully implemented in solar cell devices. The main influences of temperature, thickness and precursor flows on resistivity, optical band gap and film structure were mapped out. The analysis methods used included X-ray diffraction (XRD), X-ray fluorescence (XRF), four point probe resistivity measurements, mechanical profilometry and absorption spectrophotometry. In addition, the solar cell devices were characterized using external quantum efficiency (EQE) and current-voltage (IV) measurements. It was found that the CVD process was sensitive to the condition of the CdS surface, which resulted in a large distribution of shunted cells when grown on aged CdS. Unexpected trends in open-circuit voltage and fill factor were found. Both these factors increased when the growth temperature was decreased, resulting in higher conversion efficiencies. Compared to i-ZnO deposited by an in-house baseline sputtering process, the CVD process resulted in cells with higher short-circuit current due to higher EQE in the short-wavelength region. It was shown that the CVD process used is capable of producing solar cell devices whose performances contest those of cells manufactured with sputtered i-ZnO.