Étude de la cinétique et des dommages de gravure par plasma de couches minces de nitrure d’aluminium

Une étape cruciale dans la fabrication des MEMS de haute fréquence est la gravure par plasma de la couche mince d’AlN de structure colonnaire agissant comme matériau piézoélectrique. Réalisé en collaboration étroite avec les chercheurs de Teledyne Dalsa, ce mémoire de maîtrise vise à mieux comprendre les mécanismes physico-chimiques gouvernant la cinétique ainsi que la formation de dommages lors de la gravure de l’AlN dans des plasmas Ar/Cl2/BCl3. Dans un premier temps, nous avons effectué une étude de l’influence des conditions opératoires d’un plasma à couplage inductif sur la densité des principales espèces actives de la gravure, à savoir, les ions positifs et les atomes de Cl. Ces mesures ont ensuite été corrélées aux caractéristiques de gravure, en particulier la vitesse de gravure, la rugosité de surface et les propriétés chimiques de la couche mince. Dans les plasmas Ar/Cl2, nos travaux ont notamment mis en évidence l’effet inhibiteur de l’AlO, un composé formé au cours de la croissance de l’AlN par pulvérisation magnétron réactive et non issu des interactions plasmas-parois ou encore de l’incorporation d’humidité dans la structure colonnaire de l’AlN. En présence de faibles traces de BCl3 dans le plasma Ar/Cl2, nous avons observé une amélioration significative du rendement de gravure de l’AlN dû à la formation de composés volatils BOCl. Par ailleurs, selon nos travaux, il y aurait deux niveaux de rugosité post-gravure : une plus faible rugosité produite par la présence d’AlO dans les plasmas Ar/Cl2 et indépendante de la vitesse de gravure ainsi qu’une plus importante rugosité due à la désorption préférentielle de l’Al dans les plasmas Ar/Cl2/BCl3 et augmentant linéairement avec la vitesse de gravure.

Liquid Chromatography-Electrospray Linear Ion Trap Mass Spectrometry Analysis of Targeted Neuropeptides in Tac1-/- Mouse Spinal Cords Reveal Significant Lower Concentration of Opioid Peptides.

Tachykinin and opioid peptides play a central role in pain transmission, modulation and inhibition. The treatment of pain is very important in medicine and many studies using NK1 receptor antagonists failed to show significant analgesic effects in humans. Recent investigations suggest that both pronociceptive tachykinins and the analgesic opioid systems are important for normal pain sensation. The analysis of opioid peptides in Tac1-/- spinal cord tissues offers a great opportunity to verify the influence of the tachykinin system on specific opioid peptides. The objectives of this study were to develop a HPLC–MS/MRM assay to quantify targeted peptides in spinal cord tissues. Secondly, we wanted to verify if the Tac1-/- mouse endogenous opioid system is hampered and therefore affect significantly the pain modulatory pathways. Targeted neuropeptides were analyzed by high performance liquid chromatography linear ion trap mass spectrometry. Our results reveal that EM-2, Leu-Enk and Dyn A were down-regulated in Tac1-/- spinal cord tissues. Interestingly, Dyn A was almost 3 fold down-regulated (p < 0.0001). No significant concentration differences were observed in mouse Tac1-/- spinal cords for Met-Enk and CGRP. The analysis of Tac1-/- mouse spinal cords revealed noteworthy decreases of EM-2, Leu-Enk and Dyn A concentrations which strongly suggest a significant impact on the endogenous pain-relieving mechanisms. These observations may have insightful impact on future analgesic drug developments and therapeutic strategies.

Evaluation of multiple reaction monitoring cubed for the analysis of tachykinin related peptides in rat spinal cord using a hybrid triple quadrupole–linear ion trap mass spectrometer

Targeted peptide methods generally use HPLC-MS/MRM approaches. Although dependent on the instrumental resolution, interferences may occur while performing analysis of complex biological matrices. HPLC-MS/MRM3 is a technique, which provides a significantly better selectivity, compared with HPLC-MS/MRM assay. HPLC-MS/MRM3 allows the detection and quantitation by enriching standard MRM with secondary product ions that are generated within the linear ion trap. Substance P (SP) and neurokinin A (NKA) are tachykinin peptides playing a central role in pain transmission. The objective of this study was to verify whether HPLC-HPLCMS/ MRM3 could provide significant advantages over a more traditional HPLC-MS/MRM assay for the quantification of SP and NKA in rat spinal cord. The results suggest that reconstructed MRM3 chromatograms display significant improvements with the nearly complete elimination of interfering peaks but the sensitivity (i.e. signal-to-noise ratio) was severely reduced. The precision (%CV) observed was between 3.5% - 24.1% using HPLC-MS/MRM and in the range of 4.3% - 13.1% with HPLC-MS/MRM3, for SP and NKA. The observed accuracy was within 10% of the theoretical concentrations tested. HPLC-MS/MRM3 may improve the assay sensitivity to detect difference between samples by reducing significantly the potential of interferences and therefore reduce instrumental errors.

Role of Reactive Gliosis and Neuroinflammation in Experimental Glaucoma

Le glaucome est la principale cause de cécité irréversible dans le monde. Chez les patients atteints de cette pathologie, la perte de la vue résulte de la mort sélective des cellules ganglionnaires (CGR) de la rétine ainsi que de la dégénérescence axonale. La pression intraoculaire élevée est considérée le facteur de risque majeur pour le développement de cette maladie. Les thérapies actuelles emploient des traitements pharmacologiques et/ou chirurgicaux pour diminuer la pression oculaire. Néanmoins, la perte du champ visuel continue à progresser, impliquant des mécanismes indépendants de la pression intraoculaire dans la progression de la maladie. Il a été récemment démontré que des facteurs neuroinflammatoires pourraient être impliqués dans le développement du glaucome. Cette réponse est caractérisée par une régulation positive des cytokines pro-inflammatoires, en particulier du facteur de nécrose tumorale alpha (TNFα). Cependant, le mécanisme par lequel le processus neuroinflammatoire agit sur la mort neuronale reste à clarifier. L’hypothèse principale de ce doctorat propose que les facteurs pro-inflammatoires comme le TNFα et la phosphodiestérase 4 (PDE4) interagissent avec les mécanismes moléculaires de la mort neuronale, favorisant ainsi la survie et la protection des CGRs au cours du glaucome. Dans la première partie de ma thèse, J’ai utilisé un modèle in vivo de glaucome chez des rats Brown Norway pour montrer que l’expression du TNFα est augmentée après l'induction de l'hypertension oculaire. L'hypothèse spécifique de cette étude suggère que les niveaux élevés de TNFα provoquent la mort des CGRs en favorisant l'insertion de récepteurs AMPA perméables au calcium (CP-AMPAR) à la membrane cytoplasmique. Pour tester cette hypothèse, j’ai utilisé un inhibiteur sélectif de la forme soluble du TNFα, le XPro1595. L'administration de cet agent pharmacologique a induit une protection significative des somas et des axones des neurones rétiniens. L'évaluation de la perméabilité au cobalt a montré que le TNFα soluble est impliqué dans l'insertion de CP-AMPAR à la membrane des CGRs lors du glaucome. L’exposition des neurones à une pression oculaire élevée est à l’origine de la hausse de la densité membranaire des CP-AMPARs, grâce à une diminution de l’expression de la sous-unité GluA2. La présence de GluA2 au sein du récepteur ne permet pas l’entrée du calcium à l’intérieur de la cellule. L'administration intraoculaire d’antagonistes spécifiques des CP-AMPARs promeut la protection des somas et des axones des CGRs. Ces résultats montrent que les CP-AMPARs jouent un rôle important dans la pathologie du glaucome. Dans la deuxième partie de ma thèse, j’ai caractérisé l'effet neuroprotecteur d’un inhibiteur de la PDE4, l’ibudilast, dans notre modèle de glaucome. L'hypothèse spécifique s’oriente vers une atténuation de la réponse neuroinflammatoire et de la gliose par l’administration d’ibudilast, favorisant ainsi la protection neuronale. Les résultats montrent que dans les rétines glaucomateuses, l’ibudilast diminue la gliose et l'expression de plusieurs facteurs tels que le TNFα, l'interleukine-1β (IL-1β), l’interleukine-6 (IL-6) et le facteur inhibiteur de la migration des macrophages (MIF). Chez les rats glaucomateux, nous avons observé une expression notable de PDE4A dans les cellules de Müller, qui est en corrélation avec l'accumulation de l’AMP cyclique (AMPc) dans ces cellules après un traitement d’ibudilast. Finalement, nous avons démontré que la protection des CGRs via l’administration d’ibudilast est un mécanisme dépendent de l’AMPc et de la protéine kinase A (PKA). En conclusion, les résultats présentés dans cette thèse identifient deux mécanismes différents impliqués dans la perte des CGRs au cours du glaucome. Ces mécanismes pourraient fournir des perspectives potentielles pour le développement de nouvelles stratégies de traitement du glaucome.

Non-Destructive Evaluation of Ion-Implanted Semiconductor Thin Films Using Photothermal Deflections Spectroscopy

Materials and equipment which fail to achieve the design requirements or projected life due to undetected defects may require expensive repair or early replacement. Such defects may also be the cause of unsafe conditions or catastrophic unexpected failure, and will lead to loss of revenue due to plant shutdown. Non-Destructive Evaluation (NDE) / Non Destructive Testing (NDT) is used for the examination of materials and components without changing or destroying their usefulness. NDT can be applied to each stage of a system’s construction, to monitor the integrity of the system or structure throughout its life.

Polystyrene Anchored Vanillin Schiff Base—Complexation and Ion Removal Studies

A set of six new polystyrene anchored metal complexes have been synthesized by the reaction of the metal salt with the polystyrene anchored Schiff base of vanillin. These complexes were characterized by elemental analyses, Fourier transform infrared spectroscopy, diffuse reflectance studies, thermal studies, and magnetic susceptibility measurements. The elemental analyses suggest a metal : ligand ratio of 1 : 2. The ligand is unidentate and coordinates through the azomethine nitrogen. The Mn(II), Fe(III), Co(II), Ni(II), and Cu(II) complexes are all paramagnetic while Zn(II) is diamagnetic. The Cu(II) complex is assigned a square planar structure, while Zn(II) is assigned a tetrahedral structure and Mn(II), Fe(III), Co(II), and Ni(II) are all assigned octahedral geometry. The thermal analyses were done on the ligand and its complexes to reveal their stability. Further, the application of the Schiff base as a chelating resin in ion removal studies was investigated. The polystyrene anchored Schiff base gave 96% efficiency in the removal of Ni(II) from a 20-ppm solution in 15 min, without any interference from ions such as Mn(II), Co(II), Fe(III), Cu(II), Zn(II), U(VI), Na , K , NH4 , Ca2 , Cl , Br , NO3 , NO2 ,and CH3CO2 . The major advantage is that the removal is achieved without altering the pH.

A PVC Plasticized Sensor for Ni(II) Ion Based on a Simple Ethylenediamine Derivative

new PVC membrane ion selective electrode which is highly selective towards Ni(II) ions was constructed using a Schiff base containing a binaphthyl moiety as the ionophore. The sensor exhibited a good Nernstian response for nickel ions over the concentration range 1.0 × 10–1 – 5.0 × 10–6 M with a lower limit of detection of 1.3 × 10–6 M. It has a fast response time and can be used for a period of 4 months with a good reproducibility. The sensor is suitable for use in aqueous solutions in a wide pH range of 3.6 – 7.4 and works satisfactorily in the presence of 25% (v/v) methanol or ethanol. The sensor shows high selectivity to nickel ions over a wide variety of cations. It has been successfully used as an indicator electrode in the potentiometric titration of nickel ions against EDTA and also for the direct determination of nickel content in real samples: effluent samples, chocolates and hydrogenated oils.

Complexation and ion removal studies of a polystyrene anchored Schiff base

This paper reports the synthesis of a series of six new polystyrene anchored metal complexes of Co(II), Fe(III), Ni(II), Cu(II), Zn(II), and dioxouanium(VI) using the polystyrene anchored Schiff base of 2-nitrobenzaldehyde and the corresponding metal salts. The metal salts used were anhydrous FeCl3, CoCl2 Æ 6H2O, Ni(CH3COO)2 Æ 4H2O, Cu(CH3- COO)2 Æ H2O, Zn(CH3COO)2 Æ 2H2O, and UO2(CH3COO) Æ 2H2O. Physico chemical characterizations have been made from diffuse reflectance and vibrational spectra, elemental analysis, magnetic measurements, and TG studies. The elemental analysis suggest a 1:2 metal:ligand ratio when the complexation has carried out at 70 C for about 12 h reflux. The ligand is monodentate and coordinates through the azomethine nitrogen. The Fe(III), Co(II), Ni(II), and Cu(II) complexes are all paramagnetic whereas Zn(II) and U(VI) are diamagnetic. Zn(II) is assigned a tetrahedral structure, Cu(II) and Co(II) are assigned a square planar structure and Fe(III), Ni(II), and U(VI) are all assigned an octahedral structure. The polystyrene anchored ligand has been developed as an excellent reagent for the removal of Cu(II). Optimum conditions have been developed for the removal of metal ion from solutions by studying the effect of change of concentration of metal ion, ligand, effect of pH, time of reflux, and interference effect of other ions. It was found that within a span of 20 min it is possible to remove 90% of the metal ion from a 30 ppm metal ion solution in the pH range 4–5.5.

The Role of Diffusion in ISOL Targets for the Production of Radioactive Ion Beams

On line isotope separation techniques (ISOL) for production of ion beams of short-lived radionuclides require fast separation of nuclear reaction products from irradiated target materials followed by a transfer into an ion source. As a first step in this transport chain the release of nuclear reaction products from refractory metals has been studied systematically and will be reviewed. High-energy protons (500 - 1000 MeV) produce a large number of radionuclides in irradiated materials via the nuclear reactions spallation, fission and fragmentation. Foils and powders of Re, W, Ta, Hf, Mo, Nb, Zr, Y, Ti and C were irradiated with protons (600 - 1000 MeV) at the Dubna synchrocyclotron, the CERN synchrocyclotron and at the CERN PS-booster to produce different nuclear reaction products. The main topic of the paper is the determination of diffusion coefficients of the nuclear reaction products in the target matrix, data evaluation and a systematic interpretation of the data. The influence of the ionic radius of the diffusing species and the lattice type of the host material used as matrix or target on the diffusion will be evaluated from these systematics. Special attention was directed to the release of group I, II and III-elements. Arrhenius plots lead to activation energies of the diffusion process.

Spray Pyrolysed Zinc Oxide Thin Films : Effects of Doping and Ion Beam Irradiation

In recent years scientists have made rapid and significant advances in the field of semiconductor physics. One of the most important fields of current interest in materials science is the fundamental aspects and applications of conducting transparent oxide thin films (TCO). The characteristic properties of such coatings are low electrical resistivity and high transparency in the visible region. The first semitransparent and electrically conducting CdO film was reported as early as in 1907 [1]. Though early work on these films was performed out of purely scientific interest, substantial technological advances in such films were made after 1940. The technological interest in the study of transparent semiconducting films was generated mainly due to the potential applications of these materials both in industry and research. Such films demonstrated their utility as transparent electrical heaters for windscreens in the aircraft industry. However, during the last decade, these conducting transparent films have been widely used in a variety of other applications such as gas sensors [2], solar cells [3], heat reflectors [4], light emitting devices [5] and laser damage resistant coatings in high power laser technology [6]. Just a few materials dominate the current TCO industry and the two dominant markets for TCO’s are in architectural applications and flat panel displays. The architectural use of TCO is for energy efficient windows. Fluorine doped tin oxide (FTO), deposited using a pyrolysis process is the TCO usually finds maximum application. SnO2 also finds application ad coatings for windows, which are efficient in preventing radiative heat loss, due to low emissivity (0.16). Pyrolitic tin oxide is used in PV modules, touch screens and plasma displays. However indium tin oxide (ITO) is mostly used in the majority of flat panel display (FPD) applications. In FPDs, the basic function of ITO is as transparent electrodes. The volume of FPD’s produced, and hence the volume of ITO coatings produced, continues to grow rapidly. But the current increase in the cost of indium and the scarcity of this material created the difficulty in obtaining low cost TCOs. Hence search for alternative TCO materials has been a topic of active research for the last few decades. This resulted in the development of binary materials like ZnO, SnO2, CdO and ternary materials like II Zn2SnO4, CdSb2O6:Y, ZnSO3, GaInO3 etc. The use of multicomponent oxide materials makes it possible to have TCO films suitable for specialized applications because by altering their chemical compositions, one can control the electrical, optical, chemical and physical properties. But the advantages of using binary materials are the easiness to control the chemical compositions and depositions conditions. Recently, there were reports claiming the deposition of CdO:In films with a resistivity of the order of 10-5 ohm cm for flat panel displays and solar cells. However they find limited use because of Cd-Toxicity. In this regard, ZnO films developed in 1980s, are very useful as these use Zn, an abundant, inexpensive and nontoxic material. Resistivity of this material is still not very low, but can be reduced through doping with group-III elements like In, Al or Ga or with F [6]. Hence there is a great interest in ZnO as an alternative of ITO. In the present study, we prepared and characterized transparent and conducting ZnO thin films, using a cost effective technique viz Chemical Spray Pyrolysis (CSP). This technique is also suitable for large area film deposition. It involves spraying a solution, (usually aqueous) containing soluble salts of the constituents of the desired compound, onto a heated substrate.

Tailored Ion Imprinted Polymer Materials for the Preconcentrative Separation of Noble Metals

Tailored ion imprinted polymer materials for the preconcentrative separation of noble metals. This study deals with the synthesis, separation,characterization and analytical application of the noble metals especially palladium and platinum. Platinum group metals(PGM) are currently receiving world wide attention. This group include Palladium(Pt),rhodium(Rh), ruthenium(Ru), iridium(Ir) and osmium(Os).PGM are used as catalysts for a wide variety of hydrogenation, oxidation, isomerization,cyclization,dehydrogenation and dehalogenation reactions.The corrosion resistance of PGM enables them to use in jewellery,electrical and glass industries,extrusion of synthetic fibres,manufacture of laboratory utensils,dental and medical devices. This study clearly establishes selective recovery of platinum from other noble and transition elements.

Optical absorption studies in ion implanted and amorphous semiconductors - Investigations in some tetrahedrally co-ordinated and chalcogenide materials

The thesis provides an overall review and introduction to amorphous semiconductors, followed by a brief discussion on the important structural models proposed for chalcogenide glasses and their electrical, optional and thermal properties. It also gives a brief description of the Physics of thin films, ion implantation and Photothermal Deflection Spectroscopy. A brief description of the experimental setup of a photothermal deflection spectrometer and the details of the preparation and optical characterization of the thin film samples. It deals with the employment of the subgap optional absorption measurement by PDS to characterize the defects, amorphization and annealing behavior in silicon implanted with B+ ions and the profiles of ion range and vacancy distribution obtained by the TRIM simulation. It reports the results of all absorption measurements by PDS in nitrogen implanted thin film samples of Ge-Se and As-Se systems