Ce travail de thèse porte sur l'étude et la réalisation de Lasers à Emission par la Surface à Cavité Verticale pompés électriquement (EP-VCSELs) à base d'antimoniures émettant dans le moyen-infrarouge au-delà de 2 µm. Ces VCSELs proposent des caractéristiques intéressantes pour la détection de gaz tel qu'une émission monomode et une large accordabilité sans saut de mode. L'objectif de ce travail était de développer de tels composants. La première partie de ce mémoire présente les propriétés des couches qui seront empilés pour former la structure VCSEL. La seconde partie traite des différentes conditions pour obtenir une source laser monomode. La troisième partie présente les procédés de fabrication qui ont étés mis en place. Notamment de la sous-gravure sélective de la Jonction Tunnel (JT), qui est une technique de confinement originale dans le système GaSb. Celle-ci permet de réduire le diamètre de la JT jusqu'à 6 µm, ce qui est la condition pour obtenir une émission monomode.La dernière partie de ce manuscrit présente les caractérisations menées sur les structures monolithiques à JT sous-gravées. La sous-gravure sélective nous a ainsi permis d'obtenir le premier EP-VCSEL monolithique monomode. Ce composant fonctionne au-delà de la température ambiante et en régime continu. Avec des courants de seuils aussi bas que 1,9 mA et un fonctionnement jusqu'à 70°C. Le développement des structures monolithique à zone active (ZA) en cascade a également permis d'augmenter les puissances optiques en sortie de ces composants. Celles-ci sont passées de 300 µW @ 20°C à 950 µW pour la première structure citée classique et la structure à ZA en cascades respectivement. / This thesis deals with study and conception of GaSb-based electrically pumped Vertical Cavity Surface Emitting Lasers (EP-VCSELs) emitting in the mid-infrared range above 2 µm. This VCSELs exhibits suitable characteristics for gas analysis like single-mode emission and a large current tunability without mode-hopping. The objective of this work was to develop such devices. The first part of this work is about properties of the epitaxial stack layers used to form the VCSEL structure. The second parts deal with characteristics and the confinement system to design a single mode cavity. The third part presents manufacturing process which has been set up, like Tunnel Junction (TJ) under-etching, which is an innovate approach on the GaSb system. It allows reducing TJ diameter down to 6 µm, which is a necessary point to demonstrate single-mode operation.The final part of this manuscript presents the characterisations purchased on the under-etched TJ monolithic-VCSELs. Selective under-etching of the TJ allowed the first demonstration of the first single-mode monolithic EP-VCSEL. This device emits around 2.3 µm in continuous regime above room temperature. This device exhibits threshold currents as low as 1.9 mA and operate up to 70°C. The development of bipolar cascaded VCSELs has also allowed increasing the optical power on large diameter multimode, with a maximum output power of 300 µW and 950 µW@20°C for the classic and the bipolar cascaded VCSEL respectively.

Metal and semiconducting nanocrystals have received a great deal of attention from fundamental scientists and application-oriented researchers due to their physical and chemical properties, which differ from those of bulk materials. Nanocrystals are essential building blocks in the development of nanostructured devices for energy conversion. Colloidal metals and metal chalcogenides have been developed for use as nanocrystal inks to produce efficient solar cells with lower costs. All high-performing photovoltaic nanocrystals contain toxic elements, such as Pb, or scarce elements, such as In; thus, the production of solution-processable nanocrystals from earth-abundant materials using environmentally benign synthesis and processing methods has become a major challenge for the inorganic semiconductor-based solar field. This dissertation, divided into two parts, addresses several aspects of these emerging challenges. The first portion of the thesis describes the synthesis and characterization of nanocrystals of antimony sulfide, which is composed of non-scarce and non-toxic elements, and examines their performance in photovoltaic devices. The effect of various synthetic parameters on the final morphology is explored. The structural, optical and morphological properties of the nanocrystals were investigated, and Sb2S3 nanocrystal-based solid-state semiconductor-sensitized solar cells were fabricated using different deposition processes. We achieved promising power conversion efficiencies of 1.48%. The second part of the thesis demonstrates a novel method for the in situ synthesis and patterning of nanocrystals via reactive inkjet printing. The use of low-cost manufacturing approaches for the synthesis of nanocrystals is critical for many applications, including photonics and electronics. In this work, a simple, low-cost method for the synthesis of nanocrystals with minimum size variation and waste using reactive inkjet printing is introduced. As a proof of concept, the method was used for the in situ synthesis of gold nanoparticles as a model system. Relatively monodisperse gold nanoparticles were produced. The size and shape of gold nanoparticles can be controlled by the gold precursor and surfactant concentration in the ‘ink.’ This approach can be extended to the synthesis of other nanocrystals and is thus a truly impactful process for the low-cost synthesis of materials and devices incorporating nanocrystals.

Antimonpräparate sind seit über 60 Jahren der Standard zur Behandlung der Leishmaniose. Immer häufiger kommt es jedoch zum Therapieversagen durch resistente Erreger. In Indien sprechen über 60 % der erstmalig mit Antimonpräparaten behandelten Patienten nicht mehr auf die Therapie an (Sundar et al., 2000). Obwohl dies ein großes Problem darstellt, ist bisher wenig über die Resistenzmechanismen der Parasiten bekannt. Durch die Aufklärung dieser Mechanismen könnten zwei Hauptziele erreicht werden: i) Es könnten optimierte Medikamente entwickelt werden, die die Resistenzmechanismen der Parasiten umgehen. ii) Es könnten diagnostische Maßnahmen ergriffen werden, um vor Beginn einer Therapie deren Erfolgschancen zu kalkulieren. So würde man dem Patienten die starken Nebenwirkungen sowie die Kosten der Antimontherapie ersparen. Desweiteren könnte sofort mit einer wirkungsvollen Therapie begonnen und somit die Zeitspanne verkürzt werden, in der der infizierte Patient ein Reservoir für die weitere Transmission der Parasiten darstellt. In Vorarbeiten wurde durch genetische Komplementation das Gen LbrM20_V2.0210 (Lbr_0210) vorläufig identifiziert, das bei Überexpression Antimonresistenz vermittelt (Dissertation A. Nuehs, 2010). Diese Arbeiten wurden mit Leishmania braziliensis durchgeführt. Direkt benachbart befindet sich ein strukturell sehr ähnliches Gen, LbrM20_V2.0200 (Lbr_0200). Beide Gene wurden bei den vorangegangenen Sb(III)-Selektionen untersucht. Hierbei konnte ausschließlich Lbr_0210 als resistenzvermittelnd identifiziert werden. Datenbankrecherchen ergaben, dass es zu Lbr_0210 je ein direktes orthologes Gen in Leishmania infantum und Leishmania major gibt. Das Ziel des ersten Teils dieser Doktorarbeit war es, die resistenzvermittelnde Funktion des zu Lbr_0210 orthologen Gens aus L. infantum, LinJ34.0220, in unterschiedlichen Leishmania-Spezies zu verifizieren. Es war vor allem wichtig die Frage zu beantworten, ob das Gen auch im pathogenen Stadium des Parasiten, also in intrazellulären Amastigoten, Resistenz gegenüber Pentostam®, einem Standardmedikament, vermittelt. Im zweiten Teil dieser Arbeit sollte das Protein strukturell und zellbiologisch charakterisiert werden, um Hinweise auf den Resistenzmechanismus zu erhalten. Durch den Vergleich mit dem zu Lb_0200 orthologen Gen aus L. infantum, LinJ34.0210, sollten Hinweise auf die unterschiedlichen Aufgaben der Proteine gesammelt werden.

No description available.

Interference effects of co-generated hydrides of arsenic, antimony, bismuth and selenium on trapping behavior of selenium or antimony hydrides (analytes) within iridium modified, transversely heated graphite tube atomizer (THGA) was investigated. A twin-channel hydride generation system was used for independent separate generation and introduction of analyte and interferent hydrides, i.e. in simultaneous and/or sequential analyte-interferent and interferent-analyte mode of operation. Influence of the analyte and modifier mass, interferent amount, trapping temperature and composition of the gaseous phase was studied. A simple approach for elimination of mutual interference effects by modification of the gaseous phase with oxygen in substoichiometric ratio to chemically generated hydrogen is proposed and suppression of these interference effects is demonstrated. A hypothesis on mechanism of trapping and mutual interference effects is drawn.

Atomic layer deposition (ALD) is a technique by which surface-based reactions between a precursor molecule (often metal-containing) and a co-reactant (e.g. H2O, O2 or H2) yield highly uniform and conformal (ultra-)thin films. The precursor and co-reactant are each delivered in the gas phase, separated from one another by inert gas purge steps. The self-limiting nature of these surface-based reactions allows the thickness of the film to be controlled solely by the number of ‘precursor – purge – co-reactant – purge’ cycles. This nano-scale control of film thickness allows for a large number of applications such as in flat panel displays, fuel and solar cells, and microelectronic devices. The first goal of this project was the pursuit of new low-temperature methods for main group elemental ALD using silyl-substituted precursor molecules. The second goal of the project was the development of alternative methods for thin film deposition of group 4 (M = Hf, Zr) oxides that would encourage effective (ie. void-free) filling of narrow (<20 nm) trenches in high-aspect-ratio (HAR) substrates. This thesis includes the development of new precursor molecules and reaction pathways, evaluation of precursor molecular structures, thermal stability, volatility and solution reactivity, identification of appropriate experimental conditions for ALD, and characterization of the resulting thin films. ALD of elemental antimony was achieved on hydrogen-terminated silicon (H-Si) and SiO2/Si substrates using Sb(SiMe3)3 (2-1) and SbCl3 in the temperature range 23- 65 °C. The mirror-like films were confirmed to be composed of crystalline antimony by XPS (for the film deposited at 35 °C) and XRD, with low impurity levels and strong preferential orientation of crystal growth relative to the substrate surface. To the best ofour knowledge, this is the first example of room temperature thermal ALD (with demonstrated self-limiting growth) of a pure element. Film growth at 35 °C exhibited a substrate-enhanced mechanism, characterized by faster film growth for the first ~125 ALD cycles, where substantial deposition is occurring on the original substrate surface (GPC (growth-per-cycle) = 1.3 Å on SiO2/Si, and 1.0 Å on H-Si), and slower film growth (GPC = 0.40 Å on SiO2/Si, and 0.27 Å on H-Si) after ~125 cycles, once much of the initial substrate surface has been covered. Films deposited using 500-2000 ALD cycles were shown to be continuous by SEM. The use of less than 250 cycles afforded discontinuous films. However, in this initial growth phase, when deposition is occurring primarily on the original substrate surface, in-situ surface pre-treatment by Sb(SiMe3)3 or SbCl3 (50 x 0.4 or 0.8 s pulses), followed by the use of longer precursor pulses (0.4 or 0.8 s) during the first 50 ALD cycles resulted in improved nucleation. For example, on H-Si, a continuous 6.7 nm thick film was produced after initial pre-treatment with 50 x 0.8 s pulses of SbCl3, followed by 50 ALD cycles using 0.8 s pulses. The use of longer ALD pulses in the first 50 ALD cycles following surface pre-treatment is likely required in order to achieve complete reactivity with an increased density of reactive surface sites. Boranes featuring bulky silyl or sterically unencumbered trimethylgermyl groups, in combination with a stabilizing dimethylamido group, were pursued as potential precursors for ALD of elemental boron. This ALD process would employ a boron trihalide (BX3; X = F, Cl, Br, I) co-reactant, exploiting the thermodynamically favourable formation of tetrel-halide bonds as a driving force. This work required multistep syntheses of alkali metal silyl reagents, {(Me3Si)3Si}Li(THF)2 (3-1) and tBu3SiNa(THF)n (3-2), and previously un-isolated [Me3GeLi(THF)2]2 (3-3), and their reactions with B(NMe2)Cl2 (3-4). The boranes {(Me3Si)3Si}2B(NMe2) (3-8) and (tBu3Si)(Me3Ge)B(NMe2) (3-12) were successfully synthesized, spectroscopically and crystallographically characterized, and assessed for their suitability as precursor molecules for boron ALD. Unfortunately, deposition attempts on SiO2/Si using 3-8 and BCl3 led to minor film growth (GPC = 0.01 Å). However, the enhanced volatility and solution-state reactivity of 3-12 in comparison to 3-8 makes it a promising precursor candidate for future ALD reactor studies. Attempts to synthesize bis(trimethylgermyl)(dimethylamido)borane from the 2:1 reaction of 3-3 with 3-4 resulted in the formation of a lithium trigermylamidoborate, {(Me3Ge)3B(NMe2)}Li(THF)2 (3-13). ALD can give rise to uniquely uniform and conformal ultra-thin films, but voids often remain after attempted filling of narrow high-aspect-ratio trenches. To achieve void-free trench-filling, ALD (or CVD; chemical vapour deposition) methods which deposit a flowable material are desirable, and this initially-deposited material can be converted to the target material (e.g. a metal oxide) by post-deposition annealing, or potentially at the deposition temperature on a longer timescale than flowable behaviour. In this work, a new HfO2 ALD process was developed using [Hf(NMeEt)4] in combination with β- hydroxyisovaleric acid (IVA; CMe2(OH)CH2CO2H) that introduces the potential for flowability. Self-limiting growth was observed at 100, 250, and 300 °C, with a GPC of 1.5- 2.2 Å on planar SiO2 substrates. Films deposited at 100 °C consisted of amorphous HfO2 with significant carbon content (~22 at%) and <1 at% nitrogen. After annealing at 400 °C in vacuo for 1 hour, the films were composed of amorphous HfO2 with low (<1 at%) carbon content. The co-reactant in this work, β-hydroxyisovaleric acid, was chosen with the following criteria in mind: Firstly, the carboxylic acid group may be sufficiently acidic to cleave linkages between chemisorbed hafnium species and the surface, generating flowable non-surface-tethered hafnium carboxylate species (with low volatility, so that they are not lost from the surface). Secondly, the hydroxyl groups of the ligands can potentially serve as reactive sites for the hafnium precursor delivered in the next pulse. Thirdly, fairly low-energy pathways should exist for deprotonated IVA ligands to decompose to generate oxide or hydroxide ligands with release of volatile by-products, such as CO2 and isobutene, or acetone and ketene. Experiments to gain insight into the nature of reactivity between [Hf(NMeEt)4] and IVA and a structurally similar carboxylic acid are described. These include (a) solution-state reactions between [Hf(NMeEt)4] and IVA or pivalic acid (tBuCO2H), with formation of [H2NMeEt]2[Hf(κ2-O2CCH2CMe2OH)2(κ2- OC(O)CH2CMe2O)2] (4-1) and [Hf5(μ3-O)4(κ2-O2CtBu)4(μ-O2CtBu)8] (4-2), (b) attempted ALD using pivalic acid (which lacks a hydroxyl group) in place of IVA, and (c) roomtemperature solution reactions between [Hf(NMeEt)4] and 4 equiv. of IVA to form 4-1, followed by removal of volatiles, heating at 200 °C, and volatile/soluble product analysis by NMR spectroscopy and GC-MS headspace analysis. Compounds 4-1 and 4-2 were isolated and crystallographically characterized. Heteroleptic zirconium(IV) complexes were designed, synthesized, spectroscopically and crystallographically characterized, and assessed as potential precursor molecules to enable flowable ZrO2 ALD. The envisaged process would operate via the deposition of oligomeric, one-dimensional chains that, if grown untethered on a functionalized substrate, could potentially flow to the bottoms of trenches. Reaction of one equivalent of H2(acen), H2(cis-Cyacen) or H2(trans-Cyacen) with [Zr(CH2SiMe3)4] at room temperature afforded [Zr(acen)(CH2SiMe3)2] (5-1), [Zr(cis-Cyacen)(CH2SiMe3)2] (5-2) or [Zr(trans-Cyacen)(CH2SiMe3)2] (5-3), respectively (acen = C2H4(NCMeCHC(O)Me)2; Cyacen = 1,2-C6H10(NCMeCHC(O)Me)2). These alkyl compounds are trigonal prismatic in the solid state, and whereas 5-1 and 5-3 decomposed without sublimation above 120 °C (5-10 mTorr), 5-2 sublimed in >95% yield at 85 °C (5-10 mTorr). However, heating solid 5-2 at 88 °C under static argon for 24 hours resulted in extensive decomposition to afford H2(cis-Cyacen) and SiMe4 as the soluble products. Compound 5-2 reacted cleanly with two equivalents of tBuOH to afford [Zr(cis-Cyacen)(OtBu)2] (5-4), but excess tBuOH caused both SiMe4 and H2(cis-Cyacen) elimination. The 1:1 reaction of H2(acen) with [Zr(NMeEt)4] did not proceed cleanly, and 8-coordinate [Zr(acen)2] (5-5) was identified as a by-product; this complex was isolated from the 2:1 reaction. A zirconium amido complex, [Zr(acen)(NMeEt)2] (5-6) was accessed via the reaction of 1 with two equiv. or excess HNMeEt, but decomposed readily in solution at room temperature. More sterically hindered [Zr(acen){N(SiMe3)2}2] (5-7) was synthesized via the reaction of [Zr(acen)Cl2] with two equivalents of Li{N(SiMe3)2}, but was also thermally unstable as a solid and in solution at room temperature. Compounds 5-1 to 5-3, 5-5 and 5-7 were crystallographically characterized. / Dissertation / Doctor of Science (PhD) / The focus of this work is the development of new processes to deposit ultra-thin films of main group elements and transition metal oxides. The deposition method utilized in this work is atomic layer deposition (ALD), which involves the use of a precursor molecule (which contains the target element) and a co-reactant. These chemical species must be appropriately reactive towards one another, and display adequate volatility and thermal stability. The feasibility of a precursor/co-reactant combination can be assessed using solution-state reactivity studies. For main group element ALD, silyl-containing compounds (E(SiR3)3, E = Sb, B) have been investigated as precursors in combination with EX3 (X = F, Cl, Br, I) coreactants, due to the potential for thermodynamically favourable Si-X bond formation to drive the required surface-based reactions. For metal oxide ALD (MO2; M = Hf, Zr), new ALD methods have been proposed to enable gap-free filling of narrow trenches on the surface of a silicon wafer. This work involved the design, synthesis, and evaluation of new ALD precursor molecules and reactions, ALD reactor studies for thin film deposition, and characterization of the resulting films.

No description available.

High-oxidation state main-group metal complexes are potential alternatives to transition metals for electrophilic C-H functionalization reactions. However, there is little known about how selection of the p-block, main-group metal and ligand impact C-H activation and functionalization thermodynamics and reactivity. Chapter 2 reports density functional theory (DFT) calculations used to determine qualitative and quantitative features of C-H activation and metal-methyl functionalization energy landscapes for reaction between high-oxidation state d10s0 InIII, TlIII, SnIV, and PbIV carboxylate complexes with methane. While the main-group metal influences the C-H activation barrier height in a periodic manner, the carboxylate ligand has a much larger quantitative impact on C-H activation with stabilized carboxylate anions inducing the lowest barriers. For metal-methyl reductive functionalization reactions, the barrier heights, are correlated to bond heterolysis energies as model two-electron reduction energies.In Chapter 3, DFT calculations reveal that arene C-H functionalization by the p-block main-group metal complex TlIII(TFA)3 (TFA = trifluoroacetate) occurs by a C-H activation mechanism akin to transition metal-mediated C-H activation. For benzene, toluene, and xylenes a one-step C-H activation is preferred over electron transfer or proton-coupled electron transfer. The proposed C-H activation mechanism is consistent with calculation and comparison to experiment, of arene thallation rates, regioselectivity, and H/D kinetic isotope effects. For trimethyl and tetramethyl substituted arenes, electron transfer becomes the preferred pathway and thermodynamic and kinetic calculations correctly predict the experimentally reported electron transfer crossover region.In Chapter 4, DFT calculations are used to understand the C-H oxidation reactions of methane and isobutane with SbVF5. SbVF5 is generally assumed to oxidize methane through a methanium-methyl cation mechanism. DFT calculations were used to examine methane oxidation by SbVF5 in the presence of CO leading to the acylium cation, [CH3CO]+. While there is a low barrier for methane protonation by [SbVF6]-[H]+ to give the [SbVF5]-[CH5]+ ion pair, H2 dissociation is a relatively higher energy process, even with CO assistance, and so this protonation pathway is reversible. The C-H activation/[]-bond metathesis mechanism with formation of an SbV-Me intermediate is the lowest energy pathway examined. This pathway leads to [CH3CO]+ by functionalization of the SbV-Me intermediate by CO, and is consistent with no observation of H2. In contrast to methane, due to the much lower carbocation hydride affinity, isobutane significantly favors hydride transfer to give tert-butyl carbocation with concomitant SbV to SbIII reduction. In this mechanism, the resulting highly acidic SbV-H intermediate provides a route to H2 through protonation of isobutane.

No description available.

No description available.