Développement de composés conjugués en étoile de première génération incluant des liens azométhines et études électrochimiques et photophysiques

Les matériaux conjugués sont de nos jours très utilisés dans de nombreuses applications ainsi qu’en recherche. L’enchainement des liaisons π-σ-π permet la délocalisation des électrons et d’obtenir différentes propriétés comme la conduction, la fluorescence, la chélation, etc. Ainsi, de nombreux dispositifs utilisent ces caractéristiques en vue d’obtenir de nouveaux matériaux révolutionnaires comme les cellules solaires, les transistors à effet de champs, les dispositifs électrochromiques, etc.. Les dispositifs électrochromiques font partie des dispositifs en vogue. Ils sont capables de changer de couleur selon le potentiel électrique appliqué. Ils se distinguent par la simplicité du mode de conception et ils ne nécessitent pas de fonctionner dans des conditions drastiques comme une atmosphère contrôlée. Ces dispositifs sont actuellement utilisés et commercialisés comme fenêtre intelligente, camouflage, papier électronique et carte de visite personnalisée pour n’en nommer que quelques-uns. Deux propriétés sont essentielles pour que des composés puissent être utilisés dans ces familles de dispositifs : la réversibilité à l’oxydation et la stabilité à l’air et à la lumière. Dans le groupe de recherche du professeur W.G. Skene, l’axe principal de recherche est basé sur la conception de nouveaux matériaux conducteurs comportant des liaisons azométhines. Les principaux matériaux étudiés sont des dérivés de thiophènes et de fluorènes. De précédents résultats ont montré que plusieurs produits issus de la réaction de condensation entre les dérivés du 2,5-diaminothiophène et de thiophènes diformylés menaient à des produits possédant d’excellentes propriétés photophysiques et électrochimiques. C’est en partant de ces résultats encourageants qu’il a été choisi de synthétiser une nouvelle famille de produits avec un nouveau substrat fonctionnalisé. Ce dernier possède d’excellentes propriétés électrochimiques et photophysiques : la triphénylamine. Deux familles de produits ont été synthétisées qui possèdent toutes comme cœur une triphénylamine. Cette dernière a été modifiée de façon à créer une, deux ou trois liaisons azométhines avec différents thiophènes. Deux dérivés du thiophène ont été choisis afin d’étudier l’influence des groupements donneurs et accepteurs sur ces nouveaux types de composés encore jamais étudiés. Les résultats des différentes synthèses et analyses ont été effectués par RMN, spectrométrie de masse, spectrométrie d’absorbance UV-Visible, fluorescence et voltampérométrie cyclique sont rapportées dans le présent recueil.

Growth and Characterisation of Radio Frequency Magnetron Sputttered Indium Tin Oxide Thin Films

The increasing interest in the interaction of light with electricity and electronically active materials made the materials and techniques for producing semitransparent electrically conducting films particularly attractive. Transparent conductors have found major applications in a number of electronic and optoelectronic devices including resistors, transparent heating elements, antistatic and electromagnetic shield coatings, transparent electrode for solar cells, antireflection coatings, heat reflecting mirrors in glass windows and many other. Tin doped indium oxide (indium tin oxide or ITO) is one of the most commonly used transparent conducting oxides. At present and likely well into the future this material offers best available performance in terms of conductivity and transmittivity combined with excellent environmental stability, reproducibility and good surface morphology. Although partial transparency, with a reduction in conductivity, can be obtained for very thin metallic films, high transparency and simultaneously high conductivity cannot be attained in intrinsic stoichiometric materials. The only way this can be achieved is by creating electron degeneracy in a wide bandgap (Eg > 3eV or more for visible radiation) material by controllably introducing non-stoichiometry and/or appropriate dopants. These conditions can be conveniently met for ITO as well as a number of other materials like Zinc oxide, Cadmium oxide etc. ITO shows interesting and technologically important combination of properties viz high luminous transmittance, high IR reflectance, good electrical conductivity, excellent substrate adherence and chemical inertness. ITO is a key part of solar cells, window coatings, energy efficient buildings, and flat panel displays. In solar cells, ITO can be the transparent, conducting top layer that lets light into the cell to shine the junction and lets electricity flow out. Improving the ITO layer can help improve the solar cell efficiency. A transparent ii conducting oxide is a material with high transparency in a derived part of the spectrum and high electrical conductivity. Beyond these key properties of transparent conducting oxides (TCOs), ITO has a number of other key characteristics. The structure of ITO can be amorphous, crystalline, or mixed, depending on the deposition temperature and atmosphere. The electro-optical properties are a function of the crystallinity of the material. In general, ITO deposited at room temperature is amorphous, and ITO deposited at higher temperatures is crystalline. Depositing at high temperatures is more expensive than at room temperature, and this method may not be compatible with the underlying devices. The main objective of this thesis work is to optimise the growth conditions of Indium tin oxide thin films at low processing temperatures. The films are prepared by radio frequency magnetron sputtering under various deposition conditions. The films are also deposited on to flexible substrates by employing bias sputtering technique. The films thus grown were characterised using different tools. A powder x-ray diffractometer was used to analyse the crystalline nature of the films. The energy dispersive x-ray analysis (EDX) and scanning electron microscopy (SEM) were used for evaluating the composition and morphology of the films. Optical properties were investigated using the UVVIS- NIR spectrophotometer by recording the transmission/absorption spectra. The electrical properties were studied using vander Pauw four probe technique. The plasma generated during the sputtering of the ITO target was analysed using Langmuir probe and optical emission spectral studies.

Line of Brillouin-Erbium Fiber Laser Utilizing a Fabry-Perot Cavity in L-band

In this paper, the generation of a multiwavelength laser source from a Brillouin -Erbium fiber laser in the long wavelength band (L-band) region is experimentally demonstrated. The proposed laser system utilizes a Fabrv-Perot cavity formed by fiber-loop mirrors. Twenty-four lines of Brillouin-Stokes with line spacings of 10 GHz are obtained in the L-band region

A study of the preparation and characterization of bismuth telluride and bismuth oxide thin films

This thesis deals with the preparation and properties of two compounds of V-II family, viz. bismuth telluride and bismuth oxide, in thin filmform. In the first chapter is given the resume of basic solid state physics relevant to the work reported here. In the second chapter the different methods of thin film preparationtia described. Third chapter deals with the experimental techniques used for preparation and characterization of the films. Fourth chapter deals with the preparation and propertiesof bismuth telluride films. In next four chapters, the preparation and properties of bismuth oxide films are discussed in detail. In the last chapter the use of Bi205 films in the fabrication of Heat mirrors is examined and discussed.

Fabrication And Parametric Measurements Of N2 Laser Pumped Dye Laser And Its Application To Energy Transfer Studies In Mixed Dyes

Eventhough a large number of schemes have been proposed and develoned for N9 laser ouined dye lasers the relatively low efficiency compelled the scientists to device new methods to improve the system efficiencs. Energy transfer mechanism has been shown to he a convenien tool for the enhancement of efficiency of dye lasers. Th p resent work covers a detailed study of the performance characteristics of a N2 laser pumped dye laser in the con— ventional mode and also, when pumped by the energy transfer mechanism. For .th.e present investigations a dye laser pumped by a'N2 laser (A4200 kw peak power) was fabricated. The grating at grazing incidence was used as the beam expanding device; A t its best performance the system was giving an output peak power of l5 kW for a 5 X lC"3H/l Rh—€ solution in methanol. T he conversion efficiency was 7.5; The output beam was having 3 divergence of 2 mrad and bandwidth o.9 A. Suitable modifications were suggested for obtaining better conversion efficiency and bandwidth.

Quantum dynamics of crystals of molecular nanomagnets inside a resonant cavity

It is found that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. A strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing indirect evidence of the coherent microwave radiation by the crystals. A similar dependence has been found for a crystal placed between the Fabry-Perot superconducting mirrors.

Difference and equality: A critical theorist analysis of post-modern philosophy

The following paper is a critical theorist analysis of post-structuralist philosophy. It examines the omission of an economic critique in post-structuralism and describes this omission as the result of a particular flaw in Nietzsche's epistemological work, an error which has persisted all the way down through deconstruction, post-colonialism, and cultural studies. The paper seeks to reintroduce an economic critique of capitalism back into the social critique of post-structuralism, with the promise that the combination of the two will prove stronger than either critical theory or post-structuralism alone. To achieve this it reinterprets Marx' concept of metabolism as a critical economic category that mirrors post-structuralism's concept of differance.

Story Analyzing als Zugang zur Organisationskultur

The Psychohistory of Lloyd deMause as a key to corporate culture - The corporate culture approach is considered a central key to the understanding of the dynamics of organizations. Since the corporate culture mirrors unconscious contexts of meaning, culture analysis in organizations gain in importance. Narratives convey culture. So why not use narratives for the analysis of organisational cultures? The combination of data collection through work biographies with a resembling »narrative analytical method« such as the psychoanalytical fantasy-wordmethod of Lloyd deMause points out new ways of approaching organizations and their knowledge potential. This article describes the background and the accomplishment of such a research process.

Mikromechanisch durchstimmbare, dielektrische Fabry-Pérot-Filter im nahen Infrarot-Bereich: Konzept, Herstellung und Charakterisierung

Das Ziel der vorliegenden Arbeit war die Herstellung und Charakterisierung mikromechanisch durchstimmbarer, dielektrischer Fabry-Pérot-Filter im nahen Infrarot-Bereich bei einer Zentralwellenlänge von λc = 950 nm. Diese Bauelemente wurden auf Basis kostengünstiger Technologien realisiert, dank deren Entwicklung extreme Miniaturisierung und gleichzeitig hohe spektrale Anforderungen möglich sind. Der Vorteil solcher Filter liegt darin, dass sie direkt in einen Photodetektor integriert werden können und mit ganz wenigen Komponenten zu einem kompakten Spektrometermodul zusammengesetzt werden können. Die Baugröße ist nur durch die Größe des Photodetektors limitiert und die gesamte Intensität des einfallenden Lichts kann vorteilhaft auf eine einzelne Filtermembran des Fabry-Pérot-Filters fokussiert werden. Für den Filteraufbau werden zwei hochreflektierende, dielektrische DBR-Spiegel, ein organisches Opferschichtmaterial, welches zur Erzeugung einer Luftkavität im Filter dient, und zwei unterschiedliche Elektroden aus ITO und Aluminium verwendet. Die mikromechanische Auslenkung der freigelegten Filtermembran geschieht mittels elektrostatischer Aktuation, wobei auf diese Weise die Kavitätshöhe des Fabry-Pérot-Filters geändert wird und somit dieser im erforderlichen Spektralbereich optisch durchgestimmt wird. Das in dieser Arbeit gewählte Filterkonzept stellt eine Weiterentwicklung eines bereits bestehenden Filterkonzepts für den sichtbaren Spektralbereich dar. Zum Einen wurden in dieser Arbeit das vertikale und das laterale Design der Filterstrukturen geändert. Eine entscheidende Änderung lag im mikromechanisch beweglichen Teil des Fabry-Pérot-Filters. Dieser schließt den oberen DBR-Spiegel und ein aus dielektrischen Schichten und der oberen Aluminium-Elektrode bestehendes Membranhaltesystem ein, welches später durch Entfernung der Opferschicht freigelegt wird. Die Fläche des DBR-Spiegels wurde auf die Fläche der Filtermembran reduziert und auf dem Membranhaltesystem positioniert. Zum Anderen wurde im Rahmen dieser Arbeit der vertikale Schichtaufbau des Membranhaltesystems variiert und der Einfluss der gewählten Materialien auf die Krümmung der freistehenden Filterstrukturen, auf das Aktuationsverhalten und auf die spektralen Eigenschaften des gesamten Filters untersucht. Der Einfluss der mechanischen Eigenschaften dieser Materialien spielt nämlich eine bedeutende Rolle bei der Erhaltung der erforderlichen optischen Eigenschaften des gesamten Filters. Bevor Fabry-Pérot-Filter ausgeführt wurden, wurde die mechanische Spannung in den einzelnen Materialien des Membranhaltesystems bestimmt. Für die Messung wurde Substratkrümmungsmethode angewendet. Es wurde gezeigt, dass die Plasmaanregungsfrequenzen der plasmaunterstützten chemischen Gasphasenabscheidung bei einer Prozesstemperatur von 120 °C die mechanische Spannung von Si3N4 enorm beeinflussen. Diese Ergebnisse wurden im Membranhaltesystem umgesetzt, wobei verschiedene Filter mit unterschiedlichen mechanischen Eigenschaften des Membranhaltesystems gezeigt wurden. Darüber hinaus wurden optische Eigenschaften der Filter unter dem Einfluss des lateralen Designs der Filterstrukturen untersucht. Bei den realisierten Filtern wurden ein optischer Durchstimmbereich von ca. 70 nm und eine spektrale Auflösung von 5 nm erreicht. Die erreichte Intensität der Transmissionslinie liegt bei 45-60%. Diese Parameter haben für den späteren spektroskopischen Einsatz der realisierten Fabry-Pérot-Filter eine hohe Bedeutung. Die Anwendung soll erstmalig in einem „Proof of Concept“ stattfinden, wobei damit die Oberflächentemperatur eines GaAs-Wafers über die Messung der spektralen Lage seiner Bandlücke bestimmt werden kann.

Optimization of the Mechanical and Optical Properties of Tunable Optical Sensor Arrays (TOSA) for a Nanospectrometer in the Visible and Near Infrared Spectral Range

Tunable Optical Sensor Arrays (TOSA) based on Fabry-Pérot (FP) filters, for high quality spectroscopic applications in the visible and near infrared spectral range are investigated within this work. The optical performance of the FP filters is improved by using ion beam sputtered niobium pentoxide (Nb2O5) and silicon dioxide (SiO2) Distributed Bragg Reflectors (DBRs) as mirrors. Due to their high refractive index contrast, only a few alternating pairs of Nb2O5 and SiO2 films can achieve DBRs with high reflectivity in a wide spectral range, while ion beam sputter deposition (IBSD) is utilized due to its ability to produce films with high optical purity. However, IBSD films are highly stressed; resulting in stress induced mirror curvature and suspension bending in the free standing filter suspensions of the MEMS (Micro-Electro-Mechanical Systems) FP filters. Stress induced mirror curvature results in filter transmission line degradation, while suspension bending results in high required filter tuning voltages. Moreover, stress induced suspension bending results in higher order mode filter operation which in turn degrades the optical resolution of the filter. Therefore, the deposition process is optimized to achieve both near zero absorption and low residual stress. High energy ion bombardment during film deposition is utilized to reduce the film density, and hence the film compressive stress. Utilizing this technique, the compressive stress of Nb2O5 is reduced by ~43%, while that for SiO2 is reduced by ~40%. Filters fabricated with stress reduced films show curvatures as low as 100 nm for 70 μm mirrors. To reduce the stress induced bending in the free standing filter suspensions, a stress optimized multi-layer suspension design is presented; with a tensile stressed metal sandwiched between two compressively stressed films. The stress in Physical Vapor Deposited (PVD) metals is therefore characterized for use as filter top-electrode and stress compensating layer. Surface micromachining is used to fabricate tunable FP filters in the visible spectral range using the above mentioned design. The upward bending of the suspensions is reduced from several micrometers to less than 100 nm and 250 nm for two different suspension layer combinations. Mechanical tuning of up to 188 nm is obtained by applying 40 V of actuation voltage. Alternatively, a filter line with transmission of 65.5%, Full Width at Half Maximum (FWHM) of 10.5 nm and a stopband of 170 nm (at an output wavelength of 594 nm) is achieved. Numerical model simulations are also performed to study the validity of the stress optimized suspension design for the near infrared spectral range, wherein membrane displacement and suspension deformation due to material residual stress is studied. Two bandpass filter designs based on quarter-wave and non-quarter-wave layers are presented as integral components of the TOSA. With a filter passband of 135 nm and a broad stopband of over 650 nm, high average filter transmission of 88% is achieved inside the passband, while maximum filter transmission of less than 1.6% outside the passband is achieved.

Calibration of a Structured Light-Based Stereo Catadioptric Sensor

Catadioptric sensors are combinations of mirrors and lenses made in order to obtain a wide field of view. In this paper we propose a new sensor that has omnidirectional viewing ability and it also provides depth information about the nearby surrounding. The sensor is based on a conventional camera coupled with a laser emitter and two hyperbolic mirrors. Mathematical formulation and precise specifications of the intrinsic and extrinsic parameters of the sensor are discussed. Our approach overcomes limitations of the existing omni-directional sensors and eventually leads to reduced costs of production

El problema de Alhacén

El presente documento es un estudio detallado del problema conocido bajo el título de Problema de Alhacén. Este problema fue formulado en el siglo X por el filósofo y matemático árabe conocido en occidente bajo el nombre de Alhacén. El documento hace una breve presentación del filósofo y una breve reseña de su trascendental tratado de óptica Kitab al-Manazir. A continuación el documento se detiene a estudiar cuidadosamente los lemas requeridos para enfrentar el problema y se presentan las soluciones para el caso de los espejos esféricos (convexos y cóncavos), cilíndricos y cónicos. También se ofrece una conjetura que habría de explicar la lógica del descubrimiento implícita en la solución que ofreció Alhacén. Tanto los lemas como las soluciones se han modelado en los software de geometría dinámica Cabri II-Plus y Cabri 3-D. El lector interesado en seguir dichas modelaciones debe contar con los programas mencionados para adelantar la lectura de los archivos. En general, estas presentaciones constan de tres partes: (i) formulación del problema (se formula en forma concisa el problema); (ii) esquema general de la construcción (se presentan los pasos esenciales que conducen a la construcción solicitada y las construcciones auxiliares que demanda el problema), esta parte se puede seguir en los archivos de Cabri; y (iii) demostración (se ofrece la justificación detallada de la construcción requerida). Los archivos en Cabri II plus cuentan con botones numerados que pueden activarse haciendo “Click” sobre ellos. La numeración corresponde a la numeración presente en el documento. El lector puede desplazar a su antojo los puntos libres que pueden reconocerse porque ellos se distinguen con la siguiente marca (º). Los puntos restantes no pueden modificarse pues son el resultado de construcciones adelantadas y ajustadas a los protocolos recomendados en el esquema general.

La reintegración social y económica de los grupos armados ilegales en Colombia: reflexiones a partir de la trayectoria de nueve excombatientes

Esta investigación toma como marco general la Política de Reintegración Social y económica de personas y grupos alzados en armas en Colombia, en donde tras el estudio de las trayectorias en el conflicto de un grupo de 9 excombatientes, se aborda la relación existente entre los beneficios otorgados por dicha política y aquello que facilitó y motivó el ingreso, la permanencia y desmovilización de los grupos armados. Se presenta una caracterización e interpretación conceptual de las denominadas trayectorias en el conflicto, son establecidas relaciones y diferencias entre las organizaciones ilegales FARC y las AUC, se revisan las percepciones que frente a los beneficios del programa de reintegración tienen excombatientes y profesionales de la entidad que lidera dicho proceso y a partir de ello, es argumentada la incidencia que sobre el éxito de esta política tienen las características individuales y particulares, tanto de los excombatientes como de las organizaciones armadas ilegales.

Cavity-enhanced absorption: detection of nitrogen dioxide and iodine monoxide using a violet laser diode

We present an application of cavity-enhanced absorption spectroscopy with an off-axis alignment of the cavity formed by two spherical mirrors and with time integration of the cavity-output intensity for detection of nitrogen dioxide (NO2) and iodine monoxide (IO) radicals using a violet laser diode at lambda = 404.278 nm. A noise-equivalent (1sigma = root-mean-square variation of the signal) fractional absorption for one optical pass of 4.5x10(-8) was demonstrated with a mirror reflectivity of similar to0.99925, a cavity length of 0.22 m and a lock-in-amplifier time constant of 3 s. Noise-equivalent detection sensitivities towards nitrogen dioxide of 1.8x10(10) molecule cm(-3) and towards the IO radical of 3.3x10(9) molecule cm(-3) were achieved in flow tubes with an inner diameter of 4 cm for a lock-in-amplifier time constant of 3 s. Alkyl peroxy radicals were detected using chemical titration with excess nitric oxide (RO2 + NO --> RO + NO2). Measurement of oxygen-atom concentrations was accomplished by determining the depletion of NO2 in the reaction NO2 + O --> NO + O-2. Noise-equivalent concentrations of alkyl peroxy radicals and oxygen atoms were 3x10(10) molecule cm(-3) in the discharge-flow-tube experiments.

Optical thin films

Optical thin films are coatings of amorphous, crystalline or polymerized materials, in single or multiple layers, on surfaces of optical components such as lenses and mirrors. These thin film coatings are used in optics to reduce reflections from optical parts (antireflection coatings) or to provide highly reflective surfaces (dielectric mirrors), as well as to protect components against abrasion and ambient moisture.