This thesis paper examines the feasibility of using external-beam PIXE to study the surface enrichment effect in metal artifacts. By varying the energy of the incident proton beam, we penetrated the artifact's surface to different levels and were able to produce a depth profile of the elemental composition of the sample. In this study, the sample set we chose to examine consisted of ancient and modern coins. This paper first describes the surface enrichment effect and theoretically how PIXE can be used to study it. It then details the construction of the components of the external-beam setup. Many of the refinements of the hardware and experimental methods are discussed. It recounts the means of calibration of the detector and analytical tools. Finally, an accounting of the research performed on several coins is set forth, along with data showing the effectiveness of PIXE in complementing other methods of elemental analysis. We found that PIXE revealed statistically significant differences in concentrations of modern coins at the two beam energies we used. Ancient coins did not have similarly significant discrepancies between the two beam energies. The modern coin data suggested depletion in copper in copper-silver and copper-gold alloys, which is consistent with predictions of the theory of the surface enrichment effect. We suggest that the ancient coins are so deeply corroded that the PIXE beam is unable to penetrate adequately to observe surface enrichment. Comparison of our PIXE data to XRF and SEM data suggest that the trends we observed in modern coins are verified by the other methods. We therefore assert that external-beam PIXE is an effective tool for studying the surface enrichment effect, though with the beam energies available at Brigham Young University, the study must be limited to fairly modern coins.

In der vorliegenden Arbeit wird das Wachstum von Ta- und TaN-Schichten auf Si- und SiO_2-Substraten untersucht Die Schichten werden dabei unter technologienahen Bedingungen mittels Magnetron-Sputtern abgeschieden. Die Untersuchungen erfolgen hauptsächlich mit winkelaufgelöster röntgenstrahlungsangeregter Photoelektronenspektroskopie (ARXPS). Die Analysen erfolgen in situ, ohne Unterbrechung des Ultrahochvakuums, um die Deposite vor Oxidation und Kontamination zu schützen. Zur zerstörungsfreien Tiefenprofilanalyse wird ein Quantifizierungsalgoritmus beschrieben und angewandt. Für die Kombination Ta/Si wird die Bildung einer zunächst unvollständigen TaSi_2-Schicht, danach das Aufwachsen von Ta auf diese Zwischenschicht beobachtet. Für die Kombination Ta/SiO_2 wird eine Reduktion des SiO_2-Substrates bei gleichzeitigem Aufwachsen von Ta-Oxiden beobachtet. Auf dem durchmischten Schichtstapel wächst danach Ta auf. Für die Kombination TaN/Si wird die Bildung einer Si-N-Zwischenschicht bei gleichzeitigem Wachsen einer TaN-Schicht beobachtet. Für die Kombination TaN/SiO_2 wird das Aufwachsen einer TaN-Schicht ohne Ausbilung von Zwischenschichten beobachtet. Das Wachstumsverhalten des Ta/Si-Systems wird zusätzlich mit in situ Rastertunnelmikroskopie und -spektroskopie untersucht. Es wurden Untersuchungen zur thermischen Stabilität von abgeschiedenen Schichten an den Systemen Ta/Si und TaN/SiO_2 durchgeführt. Als mögliche Alternative zur winkelaufgelösten XPS wurden Untersuchungen mittels synchrotronstrahlungsangeregter Photoelektronenspektroskopie bei variierter Anregungsenergie durchgeführt.

Spatial and temporal information on catchment sediment sources and sinks can provide an improved understanding of catchment response to human-induced disturbances. This is essential for the implementation of well-targeted catchment-management decisions. This thesis investigates the nature and timing of catchment response to human activities by examining changes in sediment sources and sinks in a dry-tropical subcatchment of the Great Barrier Reef (GBR) catchment area, in northeastern Australia. Changes in catchment sediment sources, both in terms of spatial provenance and erosion type, are determined using sediment tracing techniques. Results indicate that changes in sediment source contributions over the last 250 years can be linked directly to changes in catchment land use. Sheetwash and rill erosion from cultivated land (40???60%) and channel erosion from grazed areas (30-80%) currently contribute most sediment to the river system. Channel erosion, on a basin-wide scale, appears to be more important than previously considered in this region of Australia. Optically stimulated luminescence and 137Cs dating are used to determine pre-and post- European settlement (ca. 1850) alluvial sedimentation rates. The limitations of using 137Cs as a floodplain sediment dating tool in a low fallout environment, dominated by sediment derived from channel and cultivation sources, are identified. Low magnitude increases in post-disturbance floodplain sedimentation rates (3 to 4 times) are attributed to the naturally high sediment loads in the dry-tropics. These low increases suggest that previous predictions which reflect order of magnitude increases in post-disturbance sediment yields are likely to be overestimates. In-channel bench deposits, formed since European settlement, are common features that appear to be important stores of recently eroded material. The spatially distributed erosion/sediment yield model SedNet is applied, both with generic input parameters and locally-derived data. Outputs are evaluated against available empirically-derived data. The results suggest that previous model estimates using generic input parameters overestimate post-disturbance and underestimate pre-disturbance sediment yields, exaggerating the impact of European catchment disturbance. This is likely to have important implications for both local-scale and catchment-wide management scenarios in the GBR region. Suggestions for future study and the collection of important empirical data to enable more accurate model performance are made.

La miniaturisation et l’augmentation de la complexité des circuits intégrés avancés est l’un des axes d’évolution de l’industrie microélectronique. Pour assurer les performances du transistor, une maitrise précise des épaisseurs, de la structure cristalline et de la composition, notamment de la dose d’azote, est indispensable pour chacune des couches des empilements qui constituent les transistors. Or, cette architecture complexe présente de nombreux challenges pour la métrologie. En effet, avec l’alternance de films très minces, les techniques de métrologie usuelles, basées sur des mesures en volume, sont difficiles à mettre en œuvre. Ainsi, une émergence de l’utilisation des techniques à rayons X s’observe, telle que la spectroscopie de photoélectrons à rayons X (XPS) ; méthode adaptée pour l’étude quantitative en épaisseur et en composition chimique sur des films de moins de 10nm. L’objectif principal de cette thèse est d’explorer de nouvelles approches de mise en œuvre de la technique XPS tant dans la méthodologie d’utilisation que dans les structures de tests étudiées. Dans un premier temps, ce travail porte sur l’analyse de la composition et de l’épaisseur de couches minces homogènes de l’empilement de grille des technologies 14nmFDSOI et 28nmFDSOI, composé d’un canal de SiGe et d’un empilement high-k/interfacial layer HfON/SiON. La mesure d’épaisseur par XPS appliquée à l’empilement HKMG HfON/SiON/Si est tout d’abord étudiée afin de valider son utilisation pour un suivi en ligne tout en analysant les effets de diffusion élastique sur cette mesure. Afin de déterminer la composition et l’épaisseur de couches de SiGe sur substrat de silicium, l’étude d’une métrologie hybride entre l’XPS avec la technique de réflectivité des rayons X (XRR) est menée pour en déterminer la faisabilité et la sensibilité. Dans un second temps, ce travail s’intéresse à l’étude d’empilements présentant des compositions hétérogènes avec la profondeur grâce au pARXPS (parallel Angle Resolved XPS), utilisé afin d’obtenir des reconstructions de profils chimiques. Après avoir validé la technique sur des couches HfON, SiON et SiGe, celle-ci est appliquée à des empilements industriels. La prise en compte des profils présents dans le réel empilement de grille a permis d’étudier l’effet de l’oxydation du SiGe sur le profil du germanium ainsi que d’améliorer la justesse et la sensibilité de la mesure des espèces et des épaisseurs des couches HfON et SiON sur un XPS en ligne. Enfin, l’exploration d’utilisations moins conventionnelles de l’XPS (e.g. structures 3D, étude de cristallinité) ouvre de nouvelles perspectives pour la caractérisation des couches minces. / The downscaling and the increasing complexity of integrated circuits is one of the microelectronics industry development axes. To insure the transistor performances, a precise mastering of thickness, crystalline structure and composition, notably the nitrogen dose, is mandatory for each stack layer. Yet, this complex architecture arises new challenges for metrology. Indeed, with the alternation of very thin films, conventional metrology techniques, based on volume measurements, are difficult to implement. This is why, an increasing use of X-rays techniques can be noticed, such as X-ray photoelectron spectroscopy (XPS); a well-established method for the quantitative thickness and chemical composition study of ultrathin films (<10nm). Thus, the major aim of this thesis is to explore new ways to implement XPS technique, in both the usage methodology and the test structures studied. First, this work focuses on a composition and thickness analysis of homogeneous thin films of the 14nmFDSOI and 28nmFDSOI technologies gate stack composed of an SiGe channel and a High-k/interfacial layer (HK/IL) HfON/SiON stack. The XPS thickness measurement applied to the HK/IL is firstly studied for purposes of validating its application for in-line monitoring, as well as analyzing the inelastic diffusion effects on this measurement. In order to determine the composition and thickness of SiGe layers on silicon substrate, the study of an hybrid metrology, between XPS and the X-ray reflectivity (XRR) technique, is carried out to determine the feasibility and the sensibility of this method. Secondly, this work focuses on the study of heterogeneous stack along the depth thanks to pARXPS (parallel Angle Resolved XPS), used to obtain chemical profile reconstructions. After a validation step of this technique on HfON, SiON and SiGe layers, it is used on industrial stacks. Taking into account the profiles into the real industrial gate stack allows us to study the SiGe oxidation effects on the germanium profile and to improve the accuracy and the sensibility of the composition and the thickness measurements of HfON and SiON layers with the industrial in-line XPS. Finally, the exploration of less conventional ways to use XPS (e.g. 3D structures, crystallinity study…) opens new perspectives for the characterization of thin films.

The diploma thesis deals with the use of Laser-Induced Breakdown Spectroscopy (LIBS) for depth profiling and 3D mapping of the zinc-coated steel used in the automotive industry. Before creating depth maps and depth profiles, optimization of the experiment was performed. It was shown that the LIBS technique is suited for making depth profiles and depth maps. The theoretical part deals with the description of the LIBS instrumentation, characteristics of plasma, and assembling of scientific papers which reflect the up to date knowledge about depth profiling and mapping with the use of the LIBS technique. The experimental part describes the optimization of the experiment. Gate delay, the depth and the diameter of craters using the profilometer, the position of the focal plane relative to the sample surface, and selection of spectral lines with the smallest residual signal and small scattering of data were optimized. Depth profiles of zinc, iron, chromium and manganese with the depth map of zinc and iron were made, and also the depth resolution for both elements was calculated.

In der vorliegenden Arbeit wird das Wachstum von Ta- und TaN-Schichten auf Si- und SiO_2-Substraten untersucht Die Schichten werden dabei unter technologienahen Bedingungen mittels Magnetron-Sputtern abgeschieden. Die Untersuchungen erfolgen hauptsächlich mit winkelaufgelöster röntgenstrahlungsangeregter Photoelektronenspektroskopie (ARXPS). Die Analysen erfolgen in situ, ohne Unterbrechung des Ultrahochvakuums, um die Deposite vor Oxidation und Kontamination zu schützen. Zur zerstörungsfreien Tiefenprofilanalyse wird ein Quantifizierungsalgoritmus beschrieben und angewandt. Für die Kombination Ta/Si wird die Bildung einer zunächst unvollständigen TaSi_2-Schicht, danach das Aufwachsen von Ta auf diese Zwischenschicht beobachtet. Für die Kombination Ta/SiO_2 wird eine Reduktion des SiO_2-Substrates bei gleichzeitigem Aufwachsen von Ta-Oxiden beobachtet. Auf dem durchmischten Schichtstapel wächst danach Ta auf. Für die Kombination TaN/Si wird die Bildung einer Si-N-Zwischenschicht bei gleichzeitigem Wachsen einer TaN-Schicht beobachtet. Für die Kombination TaN/SiO_2 wird das Aufwachsen einer TaN-Schicht ohne Ausbilung von Zwischenschichten beobachtet. Das Wachstumsverhalten des Ta/Si-Systems wird zusätzlich mit in situ Rastertunnelmikroskopie und -spektroskopie untersucht. Es wurden Untersuchungen zur thermischen Stabilität von abgeschiedenen Schichten an den Systemen Ta/Si und TaN/SiO_2 durchgeführt. Als mögliche Alternative zur winkelaufgelösten XPS wurden Untersuchungen mittels synchrotronstrahlungsangeregter Photoelektronenspektroskopie bei variierter Anregungsenergie durchgeführt.

During the summer of 2008 and 2009, we studied the ecology of the Kittlitz’s Murrelet (Brachyramphus brevirostris), a small diving seabird and candidate for the U.S. Endangered Species List, in Prince William Sound (PWS), Alaska. At-sea survey data suggests that the population significantly increased from 2001 to 2009, however there is limited evidence of reproductive success. Habitat use models showed individuals were observed in shallower waters, closer to glaciers, the shoreline, and further from moraines than the available habitat during the daytime. Finer extent sampling from 2008 suggests temperature-depth profiles also influence Kittlitz’s Murrelet daytime habitat use. The associations between Kittlitz’s Murrelets and water column characteristics are likely an effect of prey availability. Stable isotope work in 2009 suggests birds were generalist foragers prior to the breeding season, becoming more specialized following the breeding season. This specialization may have been a response to strict foraging constraints during the flightless fall molt. Time budgets of radio-tagged individuals suggest birds may have been responding to ephemeral prey concentrations, and working near their maximum energetic limits. Remote monitoring of radio-tagged individuals showed birds left the glacial fjord system during the nighttime, possibly spending these hours near gillnet fishing areas, suggesting a new possible area of concern in evaluating potential threats to Kittlitz’s Murrelet populations.

No description available.

Poptávka ze strany vesmírného výzkumu, zdravotnictví a bezpečnostního průmyslu způsobila v posledních letech zvýšený zájem o vývoj materiálů pro detekci a zobrazování vysokoenergetického záření. CdTe a jeho slitina CdZnTe. jsou polovodiče umožnují detekci záření o energiích v rozsahu 10 keV až 500 keV. Šířka zakázaného pásma u CdTe / CdZnTe je 1.46 -1.6 eV, což umožňuje produkci krystalů o vysoké rezistivitě (10^10-10^11 cm), která je dostačující pro použití CdTe / CdZnTe při pokojové teplotě. V mé práci byly zkoumány detektory CdTe/CdZnTe v různých stádiích jejich poruchovosti. Byly použity velmi kvalitní spektroskopické detektory, materiál s nižší rezistivitou a výraznou polarizací, detektory s asymetrií elektrických parametrů kontaktů a teplotně degenerované vzorky. Z výsledků analýzy nízkofrekvenčního šumu je patrný obecný závěr, že zvýšená koncentrace defektů způsobí změnu povahy původně monotónního spektra typu 1/f na spektrum s výrazným vlivem generačně-rekombinačních procesů. Další výrazná vlastnost degenerovaných detektorů a detektorů nižší kvality je nárůst spektrální hustoty šumu typu 1/f se vzrůstajícím napájecím napětí se směrnicí výrazně vyšší než 2. Strukturální a chemické analýzy poukázaly, že teplotní generace detektorů způsobuje difuzi kovu použitého při kontaktování a stopových prvků hlouběji do objemu krystalu. Část mé práce je věnována modifikaci povrchu svazkem argonových iontů a jejímu vlivu na chemické složení a morfologii povrchu.

CO2 is a greenhouse gas which is significantly emitted by agricultural soils through the decomposition of plant residue and soil organic carbon. Carbon isotopes can be used in determining the source of the CO2, origin of the carbon, and the age of the CO2 emissions. This study investigates the transport of CO2 gas through agricultural soils using carbon isotopes 14C and 13C to complement concentration and production rate measurements in two comparative agricultural settings in Eastern Ontario, one of which has been modified by clearing and dredging of the adjacent riparian zone and one left undredged. Traditional radiocarbon dating measures time through loss by decay, while recent dating is based on matching measurements with the atmospheric 14CO2 signal (F14C) generated by nuclear bomb testing in the 1950s and 1960s. CO2 emissions were analyzed from soil core sections together with soil-probe gas samples and surface flux chamber samples collected from the study area. Soil cores were collected from 0- 90 cm at 7.5 cm increments and placed into IsoJar® microcosms for a period of one month. CO2 in-growth was monitored to provide production rates and samples for 14C and 13C analysis. The radiocarbon data for the microcosms showed that values increase with depth from the current fraction modern value of 1.00 F14C at the surface to an attenuated peak of 1.04 F14C at a depth of 30 to 40 cm and then decrease to values below 1.00 F14C. The data collected from the soil-probe gas showed a significant depletion in comparison to the microcosms and the surface chambers. The soil cores were subsequently analyzed by a selective leach oxidation protocol to sample decreasingly labile solid organic carbon. This involved placing the weighed soil samples into MilliQ water for 24 hours, before being passed through two sieves, 63 microns and 0.45 microns. The DOC leachate was collected and analyzed for 14C and 13C. The two solid soil fractions were then dried, treated with HCl to remove carbonate and then oxidized under vacuum with 5% H2O2 yielding CO2 and residual soil carbon for 14C and 13C. The radiocarbon analysis of these variously labile fractions, together with the microcosm and soil probe measurements, demonstrate that surface emissions at both sites are greatly dominated by CO2 from recently-sequestered labile organic carbon from the upper 30 cm with minor contribution from earlier, bomb-pulse carbon or from deeper pre-bomb carbon. No significant difference in age of emissions between the dredged and undredged sites was found.