The high degree of control over the morphology and optoelectronic properties of semiconductor nanowires (NWs) makes them attractive for applications such as thermoelectrics, quantum emitters, and photodetectors. However, NW growth is still not fully understood as many parameters play a role in the determination of NW morphology and crystal structure, which in turn governs resulting optoelectronic properties. We report tellurium-doped GaP NWs with positive tapering and radii measuring as low as 5 nm grown by the self-assisted vapor–liquid–solid mechanism using selective-area molecular beam epitaxy. The occurrence of ultrathin nanoantenna showed a dependence on pattern pitch (separation between NWs) with a predominance at 600 nm pitch, and exhibited radius oscillations that correlate with polytypic zincblende (ZB)/wurtzite (WZ) segments. A growth model explains the positive tapering of the NW leading to an ultrathin tip from the suppression of surface diffusion of Ga adatoms on the NW sidewalls by Te dopant flux. The model also provides a relationship between the radius modulations and the oscillations of the droplet contact angle, predicting the quasi-periodic radius oscillations and corresponding crystal phase transitions. Photoluminescence and cathodoluminescence at 10 K reveal distinct spectra corresponding to either the ZB or WZ phase. Emission above and below ~2.15 eV are associated with ZB and WZ, respectively. The characteristic WZ spectrum arises from a bound exciton and its phonon replicas, consistent with published results. The origin of emission in the ZB regime is less conclusive, but may originate from the splitting of a bound exciton by the field of an axial defect. The results presented in this thesis establish a link between NW growth, morphology, and optoelectronic properties to inform future work involving ultrathin NWs. / Thesis / Master of Applied Science (MASc) / A nanowire (NW) is a tiny rod with a length on the order of one millionth of a meter and diameter on the order of one billionth of a meter. We made gallium phosphide (GaP) NWs by stacking gallium and phosphorus atoms in a column. The NWs were separated by a constant distance. In some cases, we also added beryllium and tellurium atoms to our NWs. The addition of tellurium caused our NWs to grow into extremely sharp points, which we measured with a microscope that uses electrons instead of light. The microscope images also revealed that the arrangement of the atoms in the NW changes along its length. By detecting the light emission from the NWs, it was possible to distinguish between two unique arrangements. Overall, the small dimensions of our GaP NWs make them interesting for applications that require the emission or detection of single particles of light.

Nine beryllium deposits were studied in order to determine the geological environment of beryllium mineralization in southern Arizona. Beryllium occurs in two pegmatite areas, two contact metamorphic deposits, two quartz-tungsten veins, two quartz-feldspar veins, and in one quartz monzonite stock. It is associated in almost all of these deposits with purple fluorite and tungsten. Beryllium mineralization is associated with granitic and quartz monzonite intrusions of Laramide age, and generally occurs at the intersection of northwest-trending lineaments and the Texas lineament.

Graduation date: 1992

MOF-5 ist der Archetyp einer neuartigen Klasse hochporöser Materialien, den Metal Organic Frameworks, die unter anderem zur Anwendung als effektive Gasspeicher geeignet sind. Im Rahmen dieser Arbeit werden die seiner Bildung zugrunde liegenden Reaktionen untersucht. Aus den Erkenntnissen dieser Untersuchungen wurden zwei neue Syntheseverfahren entwickelt. Eines der Verfahren beruht auf der Phasenumwandlung von Zinkterephthalaten und ermöglichte die Laborsynthese von MOF-5 in 100 g-Mengen. Ein zweites Verfahren bedient sich des Strukturaufbaus mit Hilfe vorgefertigter anorganischer Cluster, wodurch erstmals die Synthese von MOF-5-Homologen anderer Metalle als Zink gelang.

<div><div><div><p>The radionuclide 10Be is produced in the atmosphere and is delivered to Earth’s surface in meteoric rain and aerosols. The stable nuclide 9Be is present in trace concentrations within rocks in Earth’s crust and is released via chemical weathering. Together, these two isotopes have been employed to study a wide range of Earth processes. Here I explore new terrestrial archives of Be isotopes: cave speleothems and terrestrial Mn-oxides. Until this point, these archives have barely been studied. Only one published dataset of Be isotopes in cave speleothems exists (Lundblad, 2006), and to my knowledge, terrestrial manganese oxides are yet to be explored. However, since speleothems and Mn-oxides precipitate from groundwater, they have the potential to encode temporal variations in the 10Be/9Be ratio of water and colloids in the vadose zone.</p><p>I develop a framework for using the 10Be/9Be ratio in the dissolved phase and/or secondary weathering products as a metric of chemical weathering rate. I am motivated by several over-arching questions:</p><ol><li><p>1) Which factor, or factors, is/are dominant in controlling Be isotopes in speleothems and terrestrial Mn-oxides?</p></li><li><p>2) Can Be isotopes in speleothems be used as a metric of weathering rate over time, particularly across glacial/interglacial cycles?</p></li><li><p>3) Can Be isotopes be used to date the formation of terrestrial Mn-oxides?</p></li></ol><p>I measure Be-isotope concentrations in speleothems from Soreq Cave, Israel. By applying an equation that I derive in this thesis, I use the temporal variation in the speleothem10Be/9Be ratio to calculate chemical weathering rates over the last 168 ka. Chemical weathering varies with independent proxies for temperature. The weathering-temperature relationship can be fit to an Arrhenius relationship, and the calculated activation energy (Ea) matches other field-based estimates for feldspar, an abundant mineral in the soil above the cave. In the Appendices I present additional results of Be-isotope measurements in a flowstone from Buffalo Cave in South Africa, as well as Mn-oxides from the Appalachians.</p></div></div></div>

Eine mit Polyethylen abgeschirmte Americium-Beryllium-Quelle wurde bzgl. ihres schnellen und thermischen Neutronenfeldes sowie Photonenfeldes durch Messungen und Simulationen quantifiziert. Dafür wurden Strahlungsfeldgrößen wie spektrale Teilchenflussdichten, Teilchenflussdichten, UmgebungsÄquivalentdosisleistungen und Richtungs-Äquivalentdosisleistungen für die jeweiligen Felder in unterschiedlichen Abständen der Strahlungsquelle bestimmt. Die ermittelten Ergebnisse werden verwendet, um einen neuen Bestrahlungsstand als Referenzfeld für Neutronen und Photonen zu errichten.:Einleitung 1. Theoretische Grundlagen 1.1. Strahlungsfeldgrößen 1.1.1. Radiometrische Größen 1.1.2. Interaktionskoeffizienten 1.1.3. Dosimetrische Größen 1.1.4. Fluenz-zu-Dosis-Konversionskoeffizienten 1.2. Photonen 1.2.1. Wechselwirkung mit Materie 1.2.2. Nachweis durch Szintillationsdetektoren 1.3. Neutronen 1.3.1. Klassifizierung 1.3.2. Wechselwirkung mit Materie 1.3.3. Nachweis schneller Neutronen durch organische Szintillationsdetektoren 1.3.4. Nachweis thermischer Neutronen durch ³He-Zählrohre 1.4. Americium-Beryllium-Quellen 1.4.1. Neutronenerzeugung 1.4.2. Abschirmung 1.5. Detektoren 1.5.1. Szintillationsdetektoren 1.5.2. ³He-Zählrohre 1.6. Digitale Pulsverarbeitung 1.6.1. Pulsformdiskriminierung mit organischen Szintillationsdetektoren 1.7. Monte-Carlo-Strahlungstransportsimulationen 2. Geräte und Materialien 3. Methoden 3.1. Quantifizierung des schnellen Neutronenfeldes 3.1.1. PFD-unterstützte Flugzeitmethode 3.1.2. Einfache Entfaltungstechnik 3.2. Quantifizierung des thermischen Neutronenfeldes 3.3. Quantifizierung des Photonenfeldes 4. Messungen 4.1. Messung 1 4.2. Messung 2 4.3. Messung 3 4.4. Messung 4 4.5. Messung 5 4.6. Messung 6 4.7. Messung 7 4.8. Messung 8 4.9. Messung 9 4.10. Messung 10 5. Simulationen mit FLUKA 5.1. Nachmodellierung der Versuchsaufbauten 5.2. Nachbildung der Strahlungsfelder 5.2.1. Bestimmung der Korrekturfaktoren 5.3. Simulierte Größen 6. Ergebnisse 6.1. Quantifizierung des schnellen Neutronenfeldes 6.1.1. Strahlungsfeldgrößen mittels des Stilbendetektors 6.1.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.1.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.2. Quantifizierung des thermischen Neutronenfeldes 6.2.1. Strahlungsfeldgrößen mittels des ³He-Zählrohrs 6.2.2. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.3. Quantifizierung des Photonenfeldes 6.3.1. Strahlungsfeldgrößen mittels des CeBr₃-Detektors 6.3.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.3.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 7. Diskussion 7.1. Quantifizierung des schnellen Neutronenfeldes 7.1.1. Spektrale Teilchenflussdichten 7.1.2. Umgebungs-Äquivalentdosisleistungen 7.2. Quantifizierung des thermischen Neutronenfeldes 7.2.1. Teilchenflussdichten 7.3. Quantifizierung des Photonenfeldes 7.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV 7.3.2. Umgebungs-Äquivalentdosisleistungen 7.3.3. Richtungs-Äquivalentdosisleistungen 8. Zusammenfassung A. Bestimmte Strahlungsfeldgrößen A.1. Schnelles Neutronenfeld A.1.1. Spektrale Teilchenflussdichten A.1.2. Umgebungs-Äquivalentdosisleistungen A.2. Thermisches Neutronenfeld A.2.1. Teilchenflussdichten A.3. Photonenfeld A.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV A.3.2. Umgebungs-Äquivalentdosisleistungen A.3.3. Richtungs-Äquivalentdosisleistungen B. Zwischenergebnisse B.1. Quantifizierung des schnellen Neutronenfeldes B.1.1. Pulsladungshistogramme des Stilbendetektors für n₁-Neutronen B.1.2. Anzahlen der Rückstoßprotonen B.2. Quantifizierung des Photonenfeldes B.2.1. Simulierte und gemessene Größen zur Bestimmung der Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV / An americium-beryllium source shielded with polyethylene was quantified in regards to its fast and thermal neutron field, as well as its photon field via measurements and simulations. Therefore, radiation field quantities like spectral fluence rates, fluence rates, ambient dose rate equivalents and directional dose rate equivalents of the respective fields were determined in different distances from the radiation source. The produced results will be used for establishing a new irradiation workbench as reference field for neutrons and photons.:Einleitung 1. Theoretische Grundlagen 1.1. Strahlungsfeldgrößen 1.1.1. Radiometrische Größen 1.1.2. Interaktionskoeffizienten 1.1.3. Dosimetrische Größen 1.1.4. Fluenz-zu-Dosis-Konversionskoeffizienten 1.2. Photonen 1.2.1. Wechselwirkung mit Materie 1.2.2. Nachweis durch Szintillationsdetektoren 1.3. Neutronen 1.3.1. Klassifizierung 1.3.2. Wechselwirkung mit Materie 1.3.3. Nachweis schneller Neutronen durch organische Szintillationsdetektoren 1.3.4. Nachweis thermischer Neutronen durch ³He-Zählrohre 1.4. Americium-Beryllium-Quellen 1.4.1. Neutronenerzeugung 1.4.2. Abschirmung 1.5. Detektoren 1.5.1. Szintillationsdetektoren 1.5.2. ³He-Zählrohre 1.6. Digitale Pulsverarbeitung 1.6.1. Pulsformdiskriminierung mit organischen Szintillationsdetektoren 1.7. Monte-Carlo-Strahlungstransportsimulationen 2. Geräte und Materialien 3. Methoden 3.1. Quantifizierung des schnellen Neutronenfeldes 3.1.1. PFD-unterstützte Flugzeitmethode 3.1.2. Einfache Entfaltungstechnik 3.2. Quantifizierung des thermischen Neutronenfeldes 3.3. Quantifizierung des Photonenfeldes 4. Messungen 4.1. Messung 1 4.2. Messung 2 4.3. Messung 3 4.4. Messung 4 4.5. Messung 5 4.6. Messung 6 4.7. Messung 7 4.8. Messung 8 4.9. Messung 9 4.10. Messung 10 5. Simulationen mit FLUKA 5.1. Nachmodellierung der Versuchsaufbauten 5.2. Nachbildung der Strahlungsfelder 5.2.1. Bestimmung der Korrekturfaktoren 5.3. Simulierte Größen 6. Ergebnisse 6.1. Quantifizierung des schnellen Neutronenfeldes 6.1.1. Strahlungsfeldgrößen mittels des Stilbendetektors 6.1.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.1.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.2. Quantifizierung des thermischen Neutronenfeldes 6.2.1. Strahlungsfeldgrößen mittels des ³He-Zählrohrs 6.2.2. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.3. Quantifizierung des Photonenfeldes 6.3.1. Strahlungsfeldgrößen mittels des CeBr₃-Detektors 6.3.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.3.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 7. Diskussion 7.1. Quantifizierung des schnellen Neutronenfeldes 7.1.1. Spektrale Teilchenflussdichten 7.1.2. Umgebungs-Äquivalentdosisleistungen 7.2. Quantifizierung des thermischen Neutronenfeldes 7.2.1. Teilchenflussdichten 7.3. Quantifizierung des Photonenfeldes 7.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV 7.3.2. Umgebungs-Äquivalentdosisleistungen 7.3.3. Richtungs-Äquivalentdosisleistungen 8. Zusammenfassung A. Bestimmte Strahlungsfeldgrößen A.1. Schnelles Neutronenfeld A.1.1. Spektrale Teilchenflussdichten A.1.2. Umgebungs-Äquivalentdosisleistungen A.2. Thermisches Neutronenfeld A.2.1. Teilchenflussdichten A.3. Photonenfeld A.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV A.3.2. Umgebungs-Äquivalentdosisleistungen A.3.3. Richtungs-Äquivalentdosisleistungen B. Zwischenergebnisse B.1. Quantifizierung des schnellen Neutronenfeldes B.1.1. Pulsladungshistogramme des Stilbendetektors für n₁-Neutronen B.1.2. Anzahlen der Rückstoßprotonen B.2. Quantifizierung des Photonenfeldes B.2.1. Simulierte und gemessene Größen zur Bestimmung der Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV

During several decades of research and development in the field of Magnetically Confined Fusion (MCF) the preferred selection of materials for Plasma Facing Components (PFC) has changed repeatedly. Without doubt, endurance of the first wall will decide research availability and lifespan of the first International Thermonuclear Research Reactor (ITER). Materials erosion, redeposition and mixing in the reactor are the critical processes responsible for modification of materials properties under plasma impact. This thesis presents several diagnostic techniques and their applications for studies of materials transport in fusion devices. The measurements were made at the EXTRAP T2R Reversed Field Pinch operated in Alfvén laboratory at KTH (Sweden), the TEXTOR tokamak, recently shut down at Forschungszentrum Jülich (Germany) and in the JET tokamak at CCFE (UK). The main outcomes of the work are: Development and application of a method for non-destructive capture and characterization of fast dust particles moving in the edge plasma of fusion devices, as well as particles generated upon laser-assisted cleaning of plasma exposed surfaces.  Advancement of conventional broad beam and micro ion beam techniques to include measurement of tritium in the surfaces exposed in future D-T experiments.  Adaption of the micro ion beam method for precision mapping of non uniform elements concentrations on irregular surfaces.  Implementation of an isotopic marker to study the large scale materials migration in a tokamak and development of a method for fast non destructive sampling of the marker on surfaces of PFCs. / <p>QC 20140508</p>

No campo da medicina, a radiação ionizante é utilizada tanto para fins terapêuticos como para fins diagnósticos, englobando assim um amplo intervalo de doses de diferentes tipos de radiações. Para assegurar que a finalidade da prática esteja sendo alcançada, são necessários estudos detalhados de detectores e dispositivos que respondam a diferentes tipos de radiações. Neste trabalho foi realizada a caracterização dosimétrica de amostras de BeO utilizando as técnicas de termoluminescência (TL) e luminescência opticamente estimulada (OSL) comparando-se as respostas para as radiações alfa, beta e X e propondose um sistema adequado para sua utilização em monitoração de feixes destas radiações. Dentre os principais resultados obtidos estão: alta sensibilidade à radiação beta para ambas as técnicas empregadas, boa reprodutibilidade das respostas TL e OSL (coeficientes de variação inferiores a 5%), uma dependência energética máxima da radiação X de 28% para técnica TL, e de apenas 7% para a técnica OSL, dentro dos intervalos de energia estudados. As características dosimétricas obtidas neste trabalho mostram a possibilidade de aplicação das amostras de BeO em dosimetria das radiações ionizantes X, alfa e beta, considerando os intervalos de dose empregados, pelas técnicas de TL e OSL. Pelos resultados obtidos, as amostras de BeO apresentaram sua utilização potencial para dosimetria de feixes de radiodiagnóstico e radioterapia. / In the medical field, the ionizing radiation is used both for therapeutic and diagnostic purposes, in a wide range of radiation doses. In order to ensure that the objective is achieved in practice, detailed studies of detectors and devices in different types of radiations beams are necessary. In this work a dosimetric characterization of BeO samples was performed using the techniques of thermoluminescence (TL) and optically stimulated luminescence (OSL) by a comparision of their response for alpha, beta and X radiations and the establishment of an appropriated system for use in monitoring of these radiations beams. The main results are: the high sensitivity to beta radiation for both techniques, good reproducibility of TL and OSL response (coefficients of variation lower than 5%), maximum energy dependence of the X radiation of 28% for the TL technique, and only 7% for the OSL technique, whithin the studied energy range. The dosimetric characteristics obtained in this work show the possibility of applying BeO samples to dosimetry of alpha, beta and X radiations, considering the studied dose ranges, using the TL and OSL techniques. From the results obtained, the samples of BeO showed their potential use for beam dosimetry in diagnostic radiology and radiotherapy.

No campo da medicina, a radiação ionizante é utilizada tanto para fins terapêuticos como para fins diagnósticos, englobando assim um amplo intervalo de doses de diferentes tipos de radiações. Para assegurar que a finalidade da prática esteja sendo alcançada, são necessários estudos detalhados de detectores e dispositivos que respondam a diferentes tipos de radiações. Neste trabalho foi realizada a caracterização dosimétrica de amostras de BeO utilizando as técnicas de termoluminescência (TL) e luminescência opticamente estimulada (OSL) comparando-se as respostas para as radiações alfa, beta e X e propondose um sistema adequado para sua utilização em monitoração de feixes destas radiações. Dentre os principais resultados obtidos estão: alta sensibilidade à radiação beta para ambas as técnicas empregadas, boa reprodutibilidade das respostas TL e OSL (coeficientes de variação inferiores a 5%), uma dependência energética máxima da radiação X de 28% para técnica TL, e de apenas 7% para a técnica OSL, dentro dos intervalos de energia estudados. As características dosimétricas obtidas neste trabalho mostram a possibilidade de aplicação das amostras de BeO em dosimetria das radiações ionizantes X, alfa e beta, considerando os intervalos de dose empregados, pelas técnicas de TL e OSL. Pelos resultados obtidos, as amostras de BeO apresentaram sua utilização potencial para dosimetria de feixes de radiodiagnóstico e radioterapia. / In the medical field, the ionizing radiation is used both for therapeutic and diagnostic purposes, in a wide range of radiation doses. In order to ensure that the objective is achieved in practice, detailed studies of detectors and devices in different types of radiations beams are necessary. In this work a dosimetric characterization of BeO samples was performed using the techniques of thermoluminescence (TL) and optically stimulated luminescence (OSL) by a comparision of their response for alpha, beta and X radiations and the establishment of an appropriated system for use in monitoring of these radiations beams. The main results are: the high sensitivity to beta radiation for both techniques, good reproducibility of TL and OSL response (coefficients of variation lower than 5%), maximum energy dependence of the X radiation of 28% for the TL technique, and only 7% for the OSL technique, whithin the studied energy range. The dosimetric characteristics obtained in this work show the possibility of applying BeO samples to dosimetry of alpha, beta and X radiations, considering the studied dose ranges, using the TL and OSL techniques. From the results obtained, the samples of BeO showed their potential use for beam dosimetry in diagnostic radiology and radiotherapy.

The Miocene rhyolites of the Spor Mountain Formation hosts the world's largest beryllium deposit which produced 85% of the world's beryllium in 2010. The fresh lava is extremely enriched in Be (up to 75 ppm in matrix glass). We have examined the rhyolite to understand the Be enrichment. The Spor Mountain rhyolite contains ~40% quartz, ~40% sanidine, ~10% biotite, and ~10% plagioclase, along with accessory fluorite, columbite, euxenite, fergusonite, monazite, thorite, and zircon. Two types of rhyolite erupted within the Spor Mountain Formation, a less evolved magma (1150 ppm Rb, 42 ppm Be, 0.68 wt% F in matrix glass) and an evolved magma (1710 ppm Rb, 75 ppm Be, 1.56 wt% F in matrix glass). Eruption temperatures estimated using zircon saturation, feldspar-liquid, two feldspar, and Ti-in-quartz geothermometers converge on 718 °C for the less evolved magma and 682 °C for the evolved magma. Using the Ti-in-Qz equation of Huang and Audetat (2012), the pressure of the Spor Mountain rhyolite system is estimated to be around 2 kbar at 700°C. Water content of the rhyolite melt was less than <5 wt%, based on the presence of all four major mineral phases at 700°C and the magma was water undersaturated (Webster et al., 1987). Viscosity of the rhyolite was about 6.2 log Pa·s for the less evolved rhyolite and 5.8 log Pa·s for the evolved rhyolite. Magma viscosities calculated using the Einstein-Roscoe question suggest the evolved magma has a slightly higher viscosity than the less evolved magma (7.0 log Pa·s in the evolved magma vs 6.7 log Pa·s in the less evolved magma) because of higher phenocryst content. Fluorine lowered the melt viscosity, though not by a significant amount (less than 0.5 log units at 1.7 wt% F). Partition coefficients for 32 elements have been calculated for biotite, for 21 elements for sanidine and plagioclase, and for 6 elements for quartz, using data acquired by laser ablation inductively coupled plasma mass spectrometry. Partition coefficients for feldspars in the Spor Mountain rhyolite are generally higher than other silicic magmas, and lower for biotite. Beryllium is one of the most incompatible trace elements in the Spor Mountain rhyolite, with a bulk partition coefficient <0.1. Volatile content of the melt (specifically F), melt composition, and the low temperature of crystallization act as the major controls of trace element partitioning. Trace element models using these partition coefficients suggests that crystal fractionation is the dominant magmatic enrichment process within the rhyolite, requiring ~45% crystallization (f = 55%) of the observed phenocrysts to get compositions from the less evolved to evolved rhyolite. Accumulation of batches of melt formed by different degrees of partial melting cannot explain the great depletion of compatible elements.