Transition metal-ligand interactions in several groups of closely related organometallic complexes are discussed from the results of both valence and core photoelectron experiments. Particular attention is given to the novel experimental aspects, including a charged particle oscillator He II source, sample introduction and containment, and data collection and spectral analysis procedures not normally associated with gas phase photo-electron spectroscopy. The application of the ionization experiments begins with a reassessment of the bonding in the group VIb metal hexacarbonyls. He I ionization data of unprecedented quality for the predominantly metal d t₂g level of Cr(CO)₆ and W(CO)₆ reveals for the first time the presence of metal-carbon vibrational fine structure. These positive ion M-C stretching frequencies are significantly reduced from neutral ground state values, giving direct evidence of the pi back-bonding nature of the t₂g level. The next chapter focuses on the comparison of the metal-nitrosyl interactions in the trans-X-W(CO)₄NO complexes to the isoelectronic/isostructural metal-carbonyl interactions in the X-Re(CO)₅ complexes (X = Cl,Br,I). A further comparison of carbonyl and nitrosyl bonding, as well as the first photoelectron assessment of metal-thionitrosyl bonding, is addressed in the next chapter by comparing the valence and core ionization data for CpCr(CO)₂NO and CpCr(CO)₂NS (Sp = η⁵-C₅H₅) to the data reported earlier for CpMn(CO)₃ and CpMn(CO)₂CS. The final chapter of the dissertation compares the electronic structure of the CpFe(CO)₂X complexes to their CpCr(NO)₂X analogs (X = Cl,Br,I,CH₃,CN). The essence of this work fully contrasts the Fe(CO)₂ and Cr(NO)₂ functional groups.

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This thesis presents experimental studies of water and ice at near-atmospheric pressures using intense x-rays only accessible at synchrotrons and free-electron lasers. In particular, it focuses on the deeply supercooled, metastable state and its implications on ice nucleation. The local structure of the liquid phase was studied by x-ray scattering over a wide temperature range extending from 339 K down to 227 K. In order to be able to study the deeply supercooled liquid, micron-sized water droplets were evaporatively cooled in vacuum and probed by ultrashort x-ray pulses. This is to date the lowest temperature at which measurements of the structure have been performed on bulk liquid water cooled from room temperature. Upon deep supercooling, the structure evolved toward that of a low-density liquid with local tetrahedral coordination. At ~230 K, where the low-density liquid structure started to dominate, the number of droplets containing ice nuclei increased rapidly. The estimated nucleation rate suggests that there is a “fragile-to-strong” transition in the dynamics of the liquid below 230 K, and its implications on water structure are discussed. Similarly, the electronic structure of deeply supercooled water was studied by x-ray emission spectroscopy down to 222 K, but the spectral changes expected from the structural transformation remained absent and explanations are discussed. At high fluence, the non-linear dependence of the x-ray emission yield indicated that there were high valence hole densities created during the x-ray pulse length due to Auger cascades, resulting in reabsorption of the x-ray emission. Finally, the hydrogen-bonded network in water was studied by x-ray absorption spectroscopy and compared to various ices. It was found that the pre-edge absorption cross-section, which is associated with distorted hydrogen bonds, could be minimized for crystalline ice grown on a hydrophobic BaF2(111) surface with low concentration of nucleation centers. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.</p>

Abstract Methylammonium lead (II) iodide has recently attracted considerable interest which may lead to substantial developments of efficient and inexpensive industrial photovoltaics. The application of this material as a light-absorbing layer in solid-state solar cells leads to impressive efficiency of over 22% in laboratory devices. However, for industrial applications, fundamental issues regarding their thermal and moisture stability need to be addressed. MAPbI3 belongs to the perovskite family of materials with the general formula ABX3 ,where is the organic cation (methylammonium) which is reported to be a major source of instability. In this work, a variety of alkyammonium lead (II) iodide materials have been synthesized by changing the organic cation, to study the relationship between the structural and physical properties of these materials. [(A)PbI3] and (A)PbI4 series were studied. Three dimensional (3D) networks (MAPbI3,MAPbBr3), two dimensional (2D) layered systems (BdAPbI4, HdAPbI4, OdAPbI4), and one dimensional (1D) columns (EAPbI3, PAPbI3, EAPb2I6) were found for the materials. [PbI6] octahedral structural units were repeated through the material network depending on the dimensionality and connectivity of the materials. Where a bulkier cation was introduced, the crystallographic unit cell increased in size which resulted in lower symmetry crystals. The connectivity of the unit cells along the material networks was found to be based on corner-sharing and face-sharing. Lower dimensionality resulted in larger bandgaps and lower photoconductivity, and hence a lower light conversion efficiency for the related solar cells. The thermal and moisture stability was greater in the 1D and 2D materials with bulkier organic cations than with methylammonium. In total, an overview is provided of the relationship between the chemical dimensionality and physical properties of the organic-inorganic lead halide materials with focus on the solar cell application. / Svenska sammandrag: Metylammoniumbly(II)jodid har under de senaste åren genererat ett stort intresse som ett möjligt material for utveckling av effektiva och på industriell skala billiga solceller. Detta material har använts som ljusabsorberande skikt i fasta solceller med imponerande omvandlingseffektiviteter på över 22% för solceller i laboratorieskala. För att denna nya typ av solceller ska bli intressanta för produktion på industriell skala, så behöver grundläggande frågeställningar kring materialens stabilitet avseende högre temperaturer och fukt klargöras. MAPbI3 har formellt perovskitstruktur med den allmänna formel ABX3, där A utgörs av den organiska katjonen (metyammoniumjonen) och som kan kopplas till materialets instabilitet. I denna avhandling har olika alkylammoniumbly(II)jodidmaterial syntetiserats där den organiska katjonen modifierats med syftet att studera växelverkan mellan struktur och fysikaliska egenskaper hos de resulterande materialen. Material av olika dimensionalitet erhölls; tredimensionella (3D) nätverk (MAPbI3, MAPbBr3), tvådimensionella (2D) skiktade strukturer (BdAPbI4, HdAPbI4, OdAPbI4), och endimensionella (1D) kedjestrukturer (EAPbI3, PAPbI3, EAPb2I6). Flera nya lågdimensionella material (2D och 1D) tillverkats och karaktäriserats för första gången. Enkristalldiffraktometri har använts för att erhålla materialens atomära struktur. Strukturen hos material tillverkade i större mängder konfirmerades genom jämförelse mellan resultat från pulverdiffraktion och enkristalldiffraktion. Den oktaedriska strukturenheten [PbI6] utgör ett återkommande tema i materialen sammankopplade till olika dimensioner. Då större organiska katjoner används karaktäriseras i regel strukturerna av större enhetsceller och lägre symmetri. De lågdimensionella materialen ger typiskt störe elektroniskt bandgap, lägre fotoinducerad ledningsförmåga och därför sämre omvandlingseffektiviteter då de används i solceller. De lågdimensionella materialen (1D och 2D) som baseras på de större organiska katjonerna uppvisar bättre stabilitet med avseende på högre tempereratur och fukt. De tvådimensionella materialens elektroniska struktur har karaktäriserats med hjälp av röntegenfotoelektronspektroskopi, liksom röntgenabsorptions- och emissionsspektroskopi. Resultat från teoretiska beräkningar stämmer väl överens med de experimentella resultaten, och de visar att materialens valensband huvudsakligen består av bidrag från atomorbitaler hos jod, medan atomorbitaler från bly främst bidrar till edningsbandet. Sammantaget erbjuder avhandlingen en översikt av sambandet mellan kemisk dimensionalitet och fysikaliska egenskaper hos ett antal organiska/oorganiska blyhalogenidmaterial med fokus på tillämpning i solceller. / <p>QC 20170123</p>

Incident 0.5 to 2.5 MeV charged particle beams were used to ionize the inner-shells of selected targets and study their subsequent emission of characteristic x-rays. ⁹Be⁺ ions were used to examine K-shell x-ray production from thin F, Na, Al, Si, P, Cl, and K targets, L-shell x-ray production from thin Cu, An, Ge, Br, Zr and Ag targets, and M-shell x-ray production from thin Pr, Nd, Eu, Dy, Ho, Hf, W, Au, Pb and Bi targets. L-shell x-ray production cross sections were also measured for ²⁷Al⁺ ions incident upon Ni, Cu, Zn, As, Zr, and Pd targets. M-shell x-ray production cross sections were measure for ²⁷Al⁺ and ⁴⁰Ar⁺ ions incident upon Pr, Nd, Gd, Dy, Lu, Hf, Au, Pb, Bi, and U targets. These measurements were performed using the 2.5 MV Van de Graaff accelerator at North Texas State University. The x-rays were detected with a Si(Li) detector whose efficiency was determined by fitting a theoretical photon absorption curve to experimentally measure values. The x-ray yields were normalized to the simultaneously measured Rutherford backscattered (RBS) yields which resulted in an x-ray production cross section per incident ion. The RBS spectrum was obtained using a standard surface barrier detector calibrated for to account for the "pulse height defect." The experimental results are compared to the predictions of both the first Born and ECPSSR theories; each of which is composed of two parts, the direct ionization (DI) of the target electron to the continuum and the capture (EC) of the target electron to the projectile. The first Born describes DI by the Plane-Wave-Born-Approximation (PWBA) and EC by the Oppenheimer-Brinkman-Kramers treatment of Nikolaev (OBKN). ECPSSR expands upon the first Born by using perturbed (PSS) and relativistic (R) target electron wave functions in addition to considering the energy loss (E) of the projectile in the target and its deviation from straight line trajectory (Coulomb deflection (C)). The measurements presented show that the first Born theories overestimate the measured results rather significantly for all experiments using the ⁹Be beams to examine the inner shell x-rays, while the ECPSSR predictions fir the measured data much better. For incident ²⁷Al and ⁴⁰Ar ions, the measured results are not predicted by the theories. The first Born generally over-predicts the data for low target atomic numbers while under-predicting at high atomic numbers. The ECPSSR theory greatly under-predicts the results (factors of 10³ to 10²⁰). Reasons for this behavior are discussed as well as suggestions for future experiments.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2017 / The Merensky Reef vertical grade distribution is highly variable within Styldrift I Mine. The variable nature of the Merensky Reef mineralisation necessitates regular and timeous updating of the planned mining cut with sampling information so that the optimum can be applied during mining operations. The current geochemical assay analysis that is used for the analysis of platinum group elements (PGEs) has been proven to be accurate and precise however it is expensive with long turn-around times from the laboratory. Portable X-ray fluorescence (pXRF) technology has been tested as an alternative to measure the platinum group element content along the Merensky Reef. pXRF technology cannot accurately measure PGE content directly. Copper and nickel are detectable by the pXRF analyser and, like PGEs, copper and nickel mineralisation peaks along Merensky Reef horizon. Copper and nickel were therefore tested as potential pathfinder elements to target PGE mineralisation along the Merensky Unit. The testing of the pXRF analyser was undertaken by analysing the accuracy of the results it produces as well as determining if a regression between copper/nickel to PGE content is possible along the Merensky Unit. The pXRF did not produce results of adequate accuracy as a consistent significant bias was detected with pXRF results which were consistently lower than laboratory results. Calibration of the pXRF using site specific samples was not sufficient to overcome the bias. Regressions from copper/nickel to PGEs were tested for the Merensky Footwall which could be isolated as a single data population. Significant outliers exist that do not fit the regression analysis due to the inconsistent PGE modes of occurrence along the Merensky Unit. Application of the pXRF to the study area therefore does not meet the required conditions. An underground trial of the pXRF has indicated that peaks in pXRF copper and nickel results often, but not always, coincide with peaks in PGE mineralisation. The pXRF can therefore be used as a low confidence indicator of PGE mineralisation however the user must be aware of the limitations of the instrument. pXRF analysis cannot be used reliably therefore geochemical assay analysis remains the most reliable method to analyse PGE content at Styldrift I Mine. / XL2018

O grafeno é um material que apresenta propriedades físicas e químicas superiores aos materiais tradicionalmente utilizados na fabricação de diferentes dispositivos. Porém, para substituir tais materiais, é imprescindível o conhecimento e controle de processos de adsorção e incorporação de diferentes compostos na superfície do grafeno, crescido ou transferido, sobre diferentes substratos. A investigação da síntese e caracterização de filmes de grafeno com a finalidade de controlar as propriedades físico-químicas e elétricas é um esforço da comunidade científica atualmente. Nesse trabalho, tivemos o objetivo de investigar o processamento térmico do grafeno em vapor de água e em óxido nítrico e sua síntese pela técnica de MBE, caracterizando as estruturas resultantes através de técnicas de análise por feixes de íons, espectroscopia de fotoelétrons e espectroscopia Raman. No caso do processamento em vapor de água, as amostras foram submetidas a tratamentos térmicos em ampla faixa de temperatura (200-1000°C), sendo possível distinguir três diferentes regimes de interação do grafeno com a água. A baixas temperaturas de processamento (200-400°C), nenhuma modificação considerável é observada. Na faixa entre 400-500°C, a estrutura plana do grafeno é corrugada para acomodar os novos grupamentos funcionais formados. A partir de 600°C, os domínios cristalinos diminuem e observa-se alto nível de dopagem oxidativa. Já no processamento em NO, evidenciou- se a introdução de N na rede cristalina e etching do grafeno em altas temperaturas. Quanto ao crescimento de grafeno sobre substratos de Si3N4 e AlN(0001) por MBE, este trabalho mostrou a viabilidade de se obter filmes de nanografeno com uma taxa de crescimento de 1 monocamada por minuto, onde a qualidade cristalina do filme formado e a espessura dependem do tempo de crescimento. / Graphene is a material which presents physical and chemical properties superior than the materials traditionally used in different devices. In order to use graphene rather than those materials, it is necessary to understand and control the adsorption process and incorporation of different compounds on graphene, grown or transferred, on different substrates. The scientific community has made efforts to control the physicochemical and electrical properties of graphene films. The objective of thesis is to investigate the physicochemical modifications of graphene induced by annealing in water vapor and nitric oxide and to grow graphene by MBE. Resulting structures were characterized by ion beam analysis, x-ray spectroscopy and Raman spectroscopy. Concerning samples treated in water vapor, annealings were performed at temperatures ranging from 200 to 1000ºC. Results evidence three different regimes with respect to annealing temperature. In the low temperature range (200–400°C), no prominent modification of graphene itself is observed. At higher temperatures (400–500°C), to accommodate newly formed oxygen functionalities, the flat and continuous sp2 bonding network of graphene is disrupted, giving rise to a puckered layer. For 600°C and above, shrinking of graphene domains and a higher doping level take place. Regarding graphene processing in NO, results show N incorporation in graphene crystal network and etching of graphene at higher temperatures. Concerning graphene synthesis on Si3N4 and AlN(0001) by MBE, this work demonstrates the feasibility of growing nanographene with a growth rate of one monolayer per minute. In addition, the crystal quality of the films and their thickness depends on growing time.

by Yeung Sau Lai Catherine. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Yeung Sau Lai Catherine. / Acknowledgments --- p.i / Abstract --- p.ii / Table of Contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.ix / Chapter Chapter1 --- Introduction to the Study of Chinese antique objects using surface science techniques / Chapter 1.1 --- Surface Science --- p.1 / Chapter 1.2 --- Surface Science Techniques --- p.1 / Chapter 1.3 --- Study of Antiques Objects --- p.2 / Chapter 1.4 --- Chinese Antique --- p.4 / Chapter 1.5 --- Aims of the current study --- p.4 / Chapter 1.6 --- Reference --- p.7 / Chapter Chapter 2 --- Silicon on Chinese Bronze Seals / Chapter 2.1 --- Introduction --- p.8 / Chapter 2.2 --- Basic Principles of the analytical techniques --- p.9 / Chapter 2.2.1 --- Scanning electron microscopy (SEM) --- p.9 / Chapter 2.2.2 --- Energy dispersive x-ray analysis (EDX) --- p.9 / Chapter 2.2.3 --- X-ray Photoelectron spectroscopy (XPS) --- p.13 / Chapter 2.3 --- Sample --- p.16 / Chapter 2.4 --- Experimental --- p.18 / Chapter 2.4.1 --- Instrument --- p.18 / Chapter 2.4.2 --- Sampling --- p.18 / Chapter 2.5 --- Results and Discussion --- p.20 / Chapter 2.5.1 --- Chemical Composition --- p.20 / Chapter 2.5.2 --- Silicon content --- p.21 / Chapter 2.5.3 --- Sources of silicon --- p.21 / Chapter 2.5.4 --- Implication of high silicon content --- p.25 / Chapter 2.6 --- Conclusion --- p.28 / Chapter 2.7 --- Related studies --- p.28 / Chapter 2.8 --- Reference --- p.29 / Chapter Chapter 3 --- Surface analysis of Chinese Jade using Fourier Transform Infrared Spectroscopy with fixed angle reflectance technique / Chapter 3.1 --- Introduction --- p.30 / Chapter 3.2 --- principles of FTIR and specular reflectance technique --- p.31 / Chapter 3.2.1 --- General principles --- p.31 / Chapter 3.2.2 --- IR spectrometer --- p.31 / Chapter 3.2.3 --- Specular (External) Reflectance Technique --- p.33 / Chapter 3.2.4 --- Kramers-Kronig Transformation --- p.33 / Chapter 3.3 --- Sample (Chinese Jade from the Liang-zhu Culture) --- p.36 / Chapter 3.3.1 --- Background on use of Jade in China --- p.36 / Chapter 3.3.2 --- Nomenclature --- p.39 / Chapter 3.3.3 --- Mineralogy of Jade --- p.39 / Chapter 3.3.4 --- Liang-zhu Culture --- p.40 / Chapter 3.4 --- Experimental --- p.40 / Chapter 3.4.1 --- Instrument --- p.40 / Chapter 3.4.2 --- Sampling --- p.44 / Chapter 3.4.3 --- Data Treatment --- p.44 / Chapter 3.5 --- Results and Discussion --- p.44 / Chapter 3.5.1 --- Characteristic of Specular reflectance spectrum of Nephrite --- p.44 / Chapter 3.5.2 --- Reflectance spectrum of Liangzhu samples --- p.57 / Chapter 3.5.2.1 --- Comparison within sample --- p.57 / Chapter 3.5.2.2 --- Comparison among sample --- p.57 / Chapter 3.5.3 --- "Reflectance spectrum of heirloom pieces from the Art Museum, CUHK" --- p.58 / Chapter 3.5.4 --- Absorption peaks at 3000-2800cm-1 --- p.58 / Chapter 3.6 --- Conclusion --- p.58 / Chapter 3.7 --- Related studies --- p.61 / Chapter 3.8 --- Reference --- p.61 / Chapter Chapter 4 --- SIMS and TIMS Analysis on Lead Isotopes Ratio in Ancient Chinese Metallic Artifacts / Chapter 4.1 --- Introduction --- p.63 / Chapter 4.2 --- Background --- p.64 / Chapter 4.2.1 --- Lead isotope --- p.64 / Chapter 4.2.2 --- Aims of this study --- p.66 / Chapter 4.3 --- Basic principle of TIMS and SIMS --- p.67 / Chapter 4.4 --- Experimental --- p.68 / Chapter 4.4.1 --- Sample --- p.68 / Chapter 4.4.2 --- Instrument --- p.68 / Chapter 4.4.2.1 --- Thermal Ionisation mass spectrometry --- p.68 / Chapter 4.4.2.2 --- Secondary ion mass spectroscopy --- p.70 / Chapter 4.5 --- Results and Discussion --- p.72 / Chapter 4.5.1 --- Data Interpretation --- p.72 / Chapter 4.5.2 --- Standard deviation of SIMS data --- p.74 / Chapter 4.5.3 --- Possible use of SIMS data --- p.74 / Chapter 4.6 --- Conclusion --- p.76 / Chapter 4.7 --- References --- p.76 / Chapter Chapter 5 --- Analysis by Particle Induced X-ray emission technique / Chapter 5.1 --- Introduction --- p.79 / Chapter 5.2 --- Basic principle --- p.80 / Chapter 5.2.1 --- General principle --- p.80 / Chapter 5.2.2 --- Fundamental Set up --- p.80 / Chapter 5.2.3 --- Data analysis --- p.82 / Chapter 5.3 --- Experimental --- p.82 / Chapter 5.3.1 --- PIXE --- p.82 / Chapter 5.3.2 --- Sample --- p.82 / Chapter 5.4 --- Result --- p.85 / Chapter 5.5 --- Further studies --- p.85 / Chapter 5.6 --- Reference --- p.85 / Chapter Chapter 6 --- Conclusion / Chapter 6.1 --- Conclusion --- p.88 / Chapter 6.2 --- Further studies --- p.89