Flat panel displays (FPDs) are microfabricated devices that are often fabricated on specialized glass substrates known as display glass. The surface chemistry of the outer few nanometers of display glass can have an important influence on FPD performance and yield. Dsiplay glass surface characterization is difficult because (i) display glass surface composition varies significantly from its bulk composition; (ii) high-surface area forms of glass, such as fibers and powders, may not have the same surface composition as melt-formed planar surfaces, and (iii) the surface composition of display glass may be altered through exposure to chemical treatments commonly used during flat panel display production, including acids, bases, etchants, detergents, and plasmas. We have performed a detailed surface composition of Eagle XG®, a widely used commercial display glass substrate, using a range of surface analytical techniques including time-of-flight secondary ion mass spectrometry (ToF-SIMS), angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and low energy ion scattering (LEIS). The information from these techniques has given us a detailed understanding of the elemental surface composition and surface hydroxylation of Eagle XG® at length scales ranging from ca. 10 nm from the surface to the outermost atomic layer. These analyses reveal that the surface composition of Eagle XG® varies significantly from its bulk composition, having generally lower concentrations of Al, B, Mg, Ca, and Sr, and higher concentrations of Si. Treatment with an industrial alkaline detergent results in significant recovery of aluminum concentration at the Eagle XG® surface, while treatment with hydrochloric and hydrofluoric acid result in further depletion of Al, B, Mg, Ca, and Sr at the sample surface.We used ToF-SIMS to quantify surface hydroxyls at the sample surface of this material. The SiOH+/Si+ peak area ratio was a useful metric of surface hydroxylation. We studied the effects of adventitious surface contamination on the measurements by analyzing samples dosed with perdeuterated triacontane, a model alkane, prior to analysis. Thick triacontane overlayers suppressed the SiOH+ signal, indicating that this approach gives inaccurately low estimates of surface hydroxylation for samples with high degrees of surface contamination, and accurate measurements are only possible for very-clean surfaces. The number of of hydroxyls on Eagle XG® surfaces varied as the surfaces were exposed to different chemical treatments. HF- and HCl- treated surfaces had the highest degree of hydroxylation, while detergent-treated surfaces had the lowest.

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The primary focus of my work is the application of informatics methods to the fields of materials science and analytical chemistry. The statistical analysis of data has become increasingly important in understanding the properties of materials and analytes. Statistical methods like principal component analysis (PCA) and multivariate curve resolution (MCR) are widely used for analysis in chemistry and other fields given their ability to categorize spectra in an unsupervised way. PCA is relatively easy to apply and has appealing mathematical properties. However, the results can be challenging to interpret, even for experienced users. In contrast, MCR results can be more interpretable, because the factors resemble real spectra and do not have negative scores or loadings. Nevertheless, the useful orthogonality properties of the scores and loadings in PCA are sacrificed in doing so. Other statistical analysis methods like cluster analysis and partial least squares regression (PLS-R) present their own challenges. Pattern recognition entropy (PRE) is a novel application of Shannon’s information theory for understanding the underlying complexity in spectra. Unlike PCA and MCR, PRE is a summary statistic that adopts the mathematical quantification of information and applies it for chemometric analysis. PRE values reflect the shape and complexity of spectra. Chapter 1 contains a description of the analytical methods/instruments that provided the data I analyzed by PRE and other informatics tools, including (i) X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) and (ii) liquid chromatography-mass spectrometry (LC-MS) and capillary electrophoresis (CE), (iii) a discussion of some of the commonly used statistical analysis tools like PCA, MCR, cluster analysis and PLS-R, and (iv) a description of PRE. Chapter 2 describes in much greater detail the theory associated with the statistical tools I used and PRE. Chapter 3 describes the PRE and informatics analysis of depth profiles through thin films by XPS and ToF-SIMS. Chapter 4 introduces the concept of the ‘reordered spectrum’ as an intuitive, visual representation of spectra to address the abstraction associated with PRE result. Total ion current chromatograms (TICCs) generated using LC-MS are often extremely complex and ‘noisy’. Chapter 5 describes the application of PRE as a variable reduction method for producing higher quality TICCs. Chapter 6 discusses the limitations associated with the application of PRE to TICCs and presents a new method using cross-correlation (CC) in conjunction with a PRE analysis. Chapter 7 discusses a new methodology that uses CE and PRE to detect autologous blood doping (ABD). Chapter 8 presents my conclusions of this present work and discusses the scope of future work on PRE. The thesis also contains several appendices. Appendix 1 introduces polyallylamine (PAAm) as a simple, easy-to-apply adhesion promoter for the widely used photoresist SU-8. Appendices 2, 3 and 4 contain articles I wrote that relate to trends in modern XPS instrumentation and 5-8 contain supplemental information relating to Chapters 3, 4, 5, and 7 respectively.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a powerful technique for the analysis of organic surfaces and interfaces for many innovative technologies. However, despite recent developments, there are still many issues and challenges hindering the robust, validated use of ToF-SIMS for quantitative measurement. These include: the lack of metrology and fundamental understanding for the use of novel cluster primary ion beams such as C60ⁿ⁺ and Ar₂₀₀₀⁺; the need for validated and robust measurement protocols for difficult samples, such as those with significant micron scale surface topography; the lack of guidance on novel data analysis methods including multivariate analysis which have the potential to simplify many time-consuming and intensive analyses in industry; and the need to establish best practice to improve the accuracy of measurements. This thesis describes research undertaken to address the above challenges. Sample topography and field effects were evaluated experimentally using model conducting and insulating fibres and compared with computer simulations to provide recommendation to diagnose and reduce the effects. Two popular multivariate methods, principal component analysis (PCA) and multivariate curve resolution (MCR), were explored using mixed organic systems consisting of a simple polymer blend and complex hair fibres treated with a multi-component formulation to evaluate different multivariate and data preprocessing methods for the optimal identification, localisation and quantification of the chemical components. Finally, cluster ion beams C60ⁿ⁺ and Ar_500-2500⁺ were evaluated on an inorganic surface and an organic delta layer reference material respectively to elucidate the fundamental metrology of cluster ion sputtering and pave the way for their use in organic depth profiling. These studies provide the essential metrological foundation to address frontier issues in surface and nanoanalysis and extend the measurement capabilities of ToF-SIMS.

When and how life first emerged on the Earth is an area of intense research. Signs of the first life on Earth, including morphological fossils, are scarce and hard to interpret. An alternative approach is to study organic biomarkers, which are molecular fossils commonly considered as bona fide biosignatures. The main objective of the project is to develop an approach for analysis of single oil-bearing fluid inclusions and most importantly the detection of organic biomarkers in these inclusions. Analysis of oil-bearing fluid inclusions is advantageous since the inclusions may provide an uncontaminated sample source of Precambrian hopanes and steranes, which are key biomarkers for tracing the early evolution of life on Earth. Due to the presence of several inclusion generations, single inclusion analysis is desired in order to constrain biomarkers to specific inclusions. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) could be an excellent tool for analysis of these types of samples. The development of the approach for analysis of single oil-bearing inclusions was done in a two-step process; i) a number of crude oils were analysed with ToF-SIMS and gas chromatography mass-spectrometry (GC-MS) to facilitate interpretation of ToF-SIMS spectra of these types of samples and, ii) a procedure that combines micrographs with ion etching and ToF-SIMS analysis was developed for analysis of inclusions. The feasibility of the technique was demonstrated for oil inclusions from the Siljan impact crater in which hopanes and steranes where detected. Single oil-bearing fluid inclusions trapped in mid-Proterozoic sandstones from Northern Australia were subsequently analyzed, and steranes and hopanes were detected in these inclusions. If applied on older inclusions this approach may help answer some of the questions regarding the emergence and evolution of life on Earth, and if applied on extraterrestrial samples, also the possibility of life on other planets and moons. / Livets uppkomst och tidiga utveckling på jorden är ett hett forskningsfält. Hur och när livet och dess olika domäner (arkéer, bakterier och eukaryoter) uppstod på jorden är fortfarande oklart vilket beror på att de första tecknen på liv, vilka inkluderar morfologiska fossil, spårfossil och isotoper, är få och svåra att tolka. Ett alternativt sätt att studera det tidiga livet är att studera organiska biomarkörer som är organiska molekyler som anses unika för liv. Huvudmålet med projektet är att utveckla en metod som kan detektera organiska biomarkörer i enskilda oljebärande vätskeinneslutningar. Vätskeinneslutningar, som är små mängder vätska (picoliter) infångad in en sten, är intressanta då de är en potentiell provkälla för prekambriska (äldre än 500 miljoner år) biomarkörer, som hopaner och steraner, vilka används för att utforska livets tidiga utveckling på jorden. Analys av enskilda inneslutningar är emellertid oftast nödvändigt för att kunna tidsavgränsa biomarkörer. På grund av att de flesta inneslutningar är små (10 µm i diameter) är det inte möjligt att analysera en enskild vätskeinneslutning med standardtekniken gaskromatografi-masspektrometri (GC-MS). Time-of-flight secondary ion mass spektrometri (ToF-SIMS) med sin höga känslighet, höga massupplösning och kapacitet för 2D-representation av analysdata och djupprofilering av prover är en utmärkt teknik för analys av enskilda inneslutningar. Metoden för analys av enskilda inneslutningar utvecklades i två steg. Först analyserades ett antal råoljor med ToF-SIMS och GC-MS för att underlätta förståelsen av ToF-SIMS-spektra från dessa typer av prover. Därefter utvecklades en metod som bestod av mikroskopering för att lokalisera inneslutningen, jonetsning för att öppna inneslutningen och ToF-SIMS analys av det exponerade innehållet. Metoden testades framgångsrikt på enskilda inneslutningar i hydrotermala vener av flusspat och kalcit i ordovicisk (488-443 miljoner år sedan) kalksten. Därefter användes den utvecklade metoden för att analysera enskilda vätskeinneslutningar i 1,43 miljarder år gammal sandsten från norra Australien, i vilka hopaner och steraner detekterades. De detekterade steranerna visar att trots att havet under denna tid var syrefritt existerade det lokala syrerika miljöer där eukaryoter kunde överleva. Om den utvecklade metoden används på ännu äldre inneslutningar, vilka har daterats till 3,2 miljarder år, kan den komma att svara på några de mest fundamentala frågorna kring livets uppkomst och tidiga utveckling. Om metoden används på utomjordiska prover kan den svara på frågan om det finns liv på andra planeter eller månar. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Submitted.

The present work is the fourth (and final) contribution to an inter-laboratory collaboration that was planned at the 3rd International Summit on Organic Photovoltaic Stability (ISOS-3). The collaboration involved six laboratories capable of producing seven distinct sets of OPV devices that were degraded under well-defined conditions in accordance with the ISOS-3 protocols. The degradation experiments lasted up to 1830 hours and involved more than 300 cells on more than 100 devices. The devices were analyzed and characterized at different points of their lifetimes by a large number of non-destructive and destructive techniques in order to identify specific degradation mechanisms responsible for the deterioration of the photovoltaic response. Work presented herein involves time-of-flight secondary ion mass spectrometry (TOF-SIMS) in order to study chemical degradation in-plane as well as in-depth in the organic solar cells. Various degradation mechanisms were investigated and correlated with cell performance. For example, photo-oxidation of the active material was quantitatively studied as a function of cell performance. The large variety of cell architectures used (some with and some without encapsulation) enabled valuable comparisons and important conclusions to be drawn on degradation behaviour. This comprehensive investigation of OPV stability has significantly advanced the understanding of degradation behaviour in OPV devices, which is an important step towards large scale application of organic solar cells. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Ce travail a pour objectif l’élaboration de surfaces permettant le contrôle de l’adsorption protéique et de l’adhésion cellulaire. Deux axes d’études permettent de répondre à cette problématique : d’une part l’optimisation des conditions de greffage par réaction thiol-ène de chaînes éthylène glycol (OEG ou PEG) comportant une fonction thiol sur une monocouche auto-assemblée de trichlorosilane d’undécényle, d’autre part la caractérisation chimique de surface (mesures d’angle de contact, ellipsométrie, microscopie de fluorescence, infrarouge en réflexion totale atténuée IR-ATR, spectroscopie de photoélectrons induits par rayons X XPS, spectrométrie de masse d’ions secondaires à temps de vol ToF-SIMS) à l’issue de chaque étape de traitement. L’étude méthodologique des conditions de greffage thiol-ène montre la mise au point d’un système bicouche structuré après 1 minute de réaction pour le greffage OEG, 1 heure pour le greffage PEG. Par l’emploi de divers substrats (oxyde de silicium, titane, verre), différentes molécules OEG-thiol ou PEG-thiol (longues de 7 à 220 unités éthyléniques, terminées –méthyle, -carboxyle ou –amine), nous mettons en avant les déclinaisons possibles de cette stratégie. Ces terminaisons chimiques conduisent, au choix, à l’inhibition de l’adsorption protéique ou à l’adsorption de biomolécules, albumine de sérum bovin (BSA) ou fibronectine (Fn), permettant de faire de l’adhésion spécifique. Le contrôle, dans le plan de l’échantillon, des zones exposées à la lumière par photochimie lors du greffage thiol-ène autorise le photopatterning des surfaces permettant la maîtrise de l’adsorption protéique et également de l’adhésion cellulaire à la surface. / The aim of this work is to design surfaces allowing controlling cellular adhesion by the study of protein adsorption and cell adhesion. Two main parts were investigated in order to answer this challenge: on one side the optimization of grafting conditions using the thiol-ene reaction of thiol-terminated ethylene glycol chains (OEG or PEG) on a undecenyltrichlorosilane self-assembled monolayer, on the other side the surface chemical characterization (angle contact measurement, ellipsometry, fluorescence microscopy, attenuated total reflection infrared IR-ATR, X-ray Photoelectron Spectroscopy XPS, Time-of-Flight Secondary Ion Mass Spectrometry ToF-SIMS) after each reaction step. The methodological investigation of thiol-ene grafting conditions exhibits the development of a bilayer structured system after a 1 minute reaction time concerning OEG grafting, 1 hour in case of PEG grafting. By using different substrates (silicon oxide, titanium, glass), different molecules OEG-thiol or PEG-thiol (from 7 to 220 ethylene unit long, methyl-, carboxyl- or amine-terminated), we highlight the range of available versions of this strategy. These chemical extremities lead on demand either to protein adsorption inhibition or to biomolecule adsorption, bovine serum albumin (BSA) or fibronectin (Fn) giving access to specific adhesion.By controlling the light-exposed areas in the sample plan, the photochemistry occurring during the thiol-ene grafting allows to design surface patterning for addressing both protein adsorption and cell adhesion on the sample surface.

Dans ce travail, Al-Cu échantillons modèle en alliage ont été chauffés sous vide ultra élevé, et on a trouvé que l'oxyde Al grandi et Cu pertage inceased en fonction de l'exposition à l'O2 en raison de l'oxydation préférentielle de Al. échantillons ont ensuite été recuits à 540 °C sous vide poussé et vieilli à 300 °C dans l'air, et corrodés en peu de temps dans l'électrolyte neutre et l'électrolyte alcalin contenant des ions Cl- en utilisant le système à trois électrodes, respectivement. Après immersion dans l'électrolyte neutre, corrosion morphologies (creusement de tranchées sur l'échantillon poli vs fosses creuses sur l'échantillon vieilli) se distinguent. Cependant, dans un électrolyte alcalin, la corrosion a à deux phases en raison de la dissolution de l'aluminium et de l'oxyde d'aluminium dans une solution alcaline: d'une part, un oxyde d'Al et la matrice d'Al ont été dissous en général, ce qui entraîne riche en Cu intermétalliques étant laissé isolément sur la surface; d'autre part, la corrosion générale a ensuite accompagné la dissolution préférentielle du substrat environnant riche en Cu intermétalliques résultant dans des tranchées autour des particules. Formation des mixtes Al-Cu oxydes riche en Cu2O et CuO dépôts ont été trouvés sur la surface corrodée. En outre, les échantillons Al-Cu recouvertes de revêtements Al2O3 déposés par procédé ALD à la surface ont été corrodés dans des conditions similaires. Comme on s'y attendait, une amélioration significative de la résistance à la corrosion des échantillons d'alliages revêtus a été observée, mais la couche d'ALD dans l'électrolyte alcalin est pas aussi stable que dans les électrolytes neutres. / In this work, Al-Cu model alloy samples were heated in ultra high vacuum (UHV), and it was found that the Al oxide grew and Cu percentage increased as a function of exposure to the O2 owing to the preferential oxidation of Al. Then samples were annealed at 540 °C in high vacuum and aged at 300 °C in air, and corroded in short time in the neutral electrolyte and the alkaline electrolyte containing Cl- ion using the three-electrode system, respectively. After immersion in the neutral electrolyte, corrosion morphologies (trenching on the polished sample vs. hollow pits on the aged sample) are distinguished due to the different distributions of Cu-rich intermetallics in the polished sample (distributed homogeneously) and the aged sample (mostly beneath the oxide layer). However, in alkaline electrolyte, corrosion went at two stages owing to the dissolution of aluminium and aluminium oxide in an alkaline solution: firstly, Al oxide and the Al matrix were dissolved generally, resulting in Cu-rich intermetallics being left isolatedly on the surface; secondly, general corrosion went on accompanied with the preferential dissolution of substrate surrounding Cu-rich intermetallics resulting in trenching around particles. Formation of mixed Al-Cu oxides/hydroxides layer rich in Cu2O and CuO deposits were found on the corroded surface. Furthermore, Al-Cu samples covered with Al2O3 coatings deposited by ALD process on the surface were corroded under similar conditions. As expected, a significant improvement of corrosion resistance of the coated alloy samples was observed, but the ALD layer in alkaline electrolyte is not as stable as in neutral electrolytes, and undergoes dissolution.

Les couches de conversion actuellement utilisées dans l'industrie aéronautique, pour protéger le métal de la corrosion et favoriser l'adhérence de la peinture, contiennent du chrome hexavalent, composé toxique et cancérigène dont l'utilisation va prochainement être interdite par la réglementation européenne REACh. L'une des pistes envisagée pour remplacer ces couches chromatées est l'utilisation de couches de conversion TCP (Trivalent Chromium Protection). Ces travaux portent sur l'étude des couches de TCP et s'attachent à caractériser chaque étape du traitement de surface industriel, incluant les étapes de prétraitement et de post-traitement. Des techniques d'analyse de surface (XPS, ToF-SIMS, AFM, MEB et PM-IRRAS) ont été utilisées pour analyser la composition chimique et la morphologie de la surface après chaque étape du traitement. Cette étude a été réalisée sur un alliage d'aluminium AA 2024-T3, très utilisé en aéronautique pour ses propriétés mécanique, mais présentant une faible résistance à la corrosion. Les résultats obtenus ont notamment mis en évidence que la couche de TCP se forme sur toute la surface de l'alliage (composés intermétalliques et cavités), et ont permis de comprendre comment le post-traitement permet d'améliorer la résistance à la corrosion de la couche de TCP. Ces travaux s'intéressent également à des couches de conversion sans chrome, à base de zirconium, étudiées ici pour servir de point de départ au développement d'une conversion sans chrome qui respecterait les exigences de résistance à la corrosion. / Conversion coatings are used in aerospace industry to protect the metal from corrosion and to promote paint adhesion. Currently, chromate conversion coatings are used, but chromate is toxic and carcinogenic and its use will be forbidden by the European REACh regulation. TCP (Trivalent Chromium Protection) conversion coatings, are considered as a promising alternative to replace chromate conversion coating. This work focuses on the characterisation of the TCP layer and considers each step of the industrial surface treatment, including pre-treatment and post-treatment steps. Surface analytical techniques (XPS, ToF-SIMS, AFM, SEM and PM-IRRAS) were used to analyse the chemical composition and morphology of the surface after each step in the process. This work was done on an aluminium alloy AA 2024-T3, commonly used in the aerospace industry for its good mechanical properties, but poorly resistant to corrosion. The results obtained demonstrate, among other things, that the TCP layer totally covers the surface (intermetallic compounds and cavities) and enable to understand how the post-treatment can improve the corrosion resistance of the TCP coating. This work also focuses on conversion coating based on zirconium, which are studied here to be used as a starting point to develop a new conversion coating without chromium, meeting the corrosion resistance requirement.

Extensive research has shown that electrochemistry is one of the factors that govern the flotation of sulfide minerals. Flotation is often adversely affected by uncontrolled oxidation, which is also an electrochemical process. The interest in pyrrhotite recovery arose after observing that there is a substantial loss of PGM due to the depression of pyrrhotite and the subsequent loss of any PGMs associated with it. The first part of this study focuses on the influence of chemical composition and crystal structure on the electrochemical behaviour of pyrrhotite in a 0.05 M Na2B4O7 solution. Rest potential and polarisation resistance measurements, as well as anodic polarisation diagrams, showed that the magnetic 4C type pyrrhotite is anodically more reactive than the non-magnetic 6C type pyrrhotite. It was also shown in cathodic polarisation diagrams that the non-magnetic 6C type pyrrhotite is a better substrate for oxygen reduction and is less susceptible to oxidation. ToF-SIMS showed the formation of an oxide layer on the pyrrhotite surface after oxidation. In the second part of this work, the influence of galvanic interactions on the electrochemical behaviour of pyrrhotite in contact with pentlandite was investigated. It was observed that, under oxygen-saturated conditions, as the amount of pentlandite increases, the reactivity towards oxidation of the mixed mineral system is reduced. Impedance measurements showed a decrease in capacitance values, indicating the formation of a continuous oxide layer on the surface and an increase in oxide layer thickness with decreasing pentlandite content. Anodic polarisation diagrams showed that under oxygen-deficient conditions and in the low potential region, pentlandite behaves as an inert material and does not have an influence on the oxidation behaviour of pyrrhotite. Hence, the anodic activities of the different magnetic 4C type pyrrhotites from Sudbury Gertrude, Phoenix and Russia were compared. It was shown that the oxidation reactivity decreased in the following order: Sudbury Gertrude magnetic 4C pyrrhotite > Phoenix magnetic 4C pyrrhotite > Russian magnetic 4C pyrrhotite; it also varied according to location. In the transpassive region, higher anodic currents were observed on the mixed samples because both pentlandite and pyrrhotite reacts. The reactivity increased in the order: pure pyrrhotite (Russia) < medium-pentlandite (Sudbury Gertrude) < high-pentlandite (Phoenix). In the presence of potassium ethyl xanthate, there was no change in the initial anodic reactivities of the different pyrrhotites. The anodic polarisation diagrams of the pure and mixed samples showed a reduction in the maximum anodic peak current, suggesting the presence of xanthate on the surface, which hinders oxidation of the mineral surface. In addition, the influence of cleaning of oxidised pyrrhotite with gaseous carbon dioxide was studied, using electrochemical and microflotation measurements. Electrochemical measurements indicated that CO2 treatment resulted in depassivation of the oxidised surfaces; this was supported by ToF-SIMS measurements that demonstrated a reduction in the oxide layer thickness after CO2 treatment. Anodic polarisation diagrams showed a higher anodic peak current, indicating that the surface is more reactive. Gaseous carbon dioxide conditioning of oxidised pyrrhotite resulted in improved flotation response of pyrrhotite with the aid of copper activation and higher air flow rate. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Materials Science and Metallurgical Engineering / unrestricted