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Infrared reflectivity and transmittance measurements (200-5000 cm⁻¹) were carried out on heavily-doped GaAs:C films grown by molecular beam epitaxy. With increasing carbon concentration, a broad reflectivity minimum develops in the 1000-3000 cm⁻¹ region and the one-phonon band near 270 cm⁻¹ rides on a progressively increasing high-reflectivity background. An effective-plasmon/one-phonon dielectric function with only two free parameters (plasma frequency ω_p and damping constant γ_p) gives a good description of the main features of the reflectivity spectra. The dependence of effective plasma frequency on hole concentration p is linear. At each doping, the effective-plasmon damping constant γ_p is large and corresponds to an optical hole mobility that is about half the Hall mobility at that p. Secondary-ion mass spectroscopy and localized-vibrational-mode measurements indicate that the Hall-effect-derived hole concentration is close to the carbon concentration and that the Hall factor is close to unity, so that the Hall mobility provides a good estimate of the actual dc mobility. Also, analysis shows that, for our highly-doped samples, the observed dichotomy between the dc and infrared mobilities is not a statistical-averaging artifact of the approximations involved in the model. The explanation of the small infrared mobility resides in the influence of intervalence band absorption on the effective-plasmon fit, which operationally defines that mobility via the effective-plasmon damping. The optical properties obtained with the use of the effective-plasmon model for GaAs:C yield a phenomenological, approximate, overall picture of the infrared spectra. But the neglect of intervalenceband transitions, for this p-type semiconductor, is shown (in this dissertation) to be a serious drawback of this simple model. In order to obtain the optical properties of GaAs:C in a model-independent way, and to attempt to resolve the apparent dc/infrared mobility dichotomy, we made use of a recently-developed spectroscopic-analysis procedure. Using direct numerical-solution techniques for the reflectance (R) and transmittance (T) equations of a multilayer structure, we analyzed our infrared R and T results for highly-doped films having hole concentrations from 2 × 10¹⁹ up to 1.4 × 10²⁰ cm⁻³. The optical properties were determined for photon energies from 0.07 to 0.6 eV, in which region plasmon (intraband) and intervalenceband contributions are in competition. Our results for the optical absorption coefficient resolve two separate peaks located (at high doping) at about 0.1 and 0.2 eV. (The effective-plasmon model necessarily missed the two-peak character of the actual absorption spectrum.) By carrying out theoretical calculations of the intervalenceband (IVB) absorption processes for our dopings, we identify the peak near 0.2 eV with light-hole to heavy-hole IVB transitions, and we attribute the lower-energy peak to the hole plasmon. Our experimental absorption spectra are very well described by a model combining the intervalenceband contribution to the dielectric function with a plasmon contribution. The hole-plasmon parameters ω_plasmon and γ_plasmon that we obtain for highly-doped p-GaAs yield an infrared mobility which (unlike the too-small IVB-entangled infrared mobility implied by the use of the usual effective-plasmon model) is in substantial agreement with the dc mobility. Therefore, in actuality, there is no dc/infrared mobility discrepancy. The discrepancy implied by the use of the usual, standard-operating-procedure, effective-plasmon model is a consequence of the inadequacy of that model for p-type semiconductors exhibiting intervalenceband infrared absorption. Raman-scattering measurements were carried out on the GaAs:C films. Only the phononlike coupled plasmon-phonon mode is observed. The non-occurrence of the plasmonlike mode is due to the large damping of the hole plasmon and the competition with strong Raman scattering by intervalenceband transitions among the heavy-hole, light-hole, and split-off bands. Analysis of the phononlike coupled mode, within the framework of the wavevector-dependent Lindhard-Mermin dielectric function, supports the hole properties that we determined by Hall and infrared studies. Photoluminescence measurements showed that the split-off band also participates in the photoluminescence of GaAs:C, giving rise to an above-bandgap emission band corresponding to transitions from the conduction band to the split-off valence band. / Ph. D.

This dissertation focuses on the design, synthesis, characterization of platinum (II) pyridylazolate complexes and develop high performance organic light emitting diodes (OLEDs) and design and execute high-sensitivity humidity sensors based on the luminescent metal-organic complexes of platinum. A majority of existing platinum compounds do not dissolve in organic solvents, making it difficult to analyze the photophysical characteristics of complexes in solution, a key part of understanding chemical photophysical properties. Furthermore, due to the poor quantum yield, it is inefficient for use in devices such as OLEDs. Chapter 2 reports the synthesis and characterization of a novel heteroleptic platinum(II) pyridylazolate complex with high solubility and quantum yield. The photochemistry of the complex is studied, including efficiency, emission profiles, and lifetimes at different temperatures. Chapter 3 reports the power efficiency (lm/W), current efficiency (cd/A), external quantum efficiency (EQE), luminance and operating voltage (V) of OLED devices made with the heteroleptic platinum(II) pyridylazolate complex. The relation between thickness of hole transport layer and electron transport layer on performance of devices has been studied through building a variety of devices. Chapter 4 includes application of a homoleptic platinum(II) pyridylazolate complex in humidity sensor. In many environments, the relationship between moisture content and emissive wavelength has been investigated. This research reveals that regardless of the humidity level, there is a link between increasing the temperature and decreasing the moisture absorption capacity of the complex.

Cubic Polyhedral Oligomeric SilSesquioxanes (POSS) of general formula Si₈O₁₂R₈ (R = alkenyl, alkoxy, aryl, hydrogen...) have found applications in various fields ranging from biology to chemistry. Besides the advantage of presenting the characteristic dendritic globular shape at low generation, these three-dimensional molecules, easily modified by organic or inorganic reactions, quickly exhibit multiple end groups at their periphery, thus featuring attractive properties in catalysis and photoluminescence applications. Various dendritic POSS containing diphenylphosphine moieties at their periphery have been used in the methoxycarbonylation of ethene. Those with a -CH₂CH₂- spacer between the silicon and the phosphorus atoms (G0-8ethylPPh₂ and G1-16ethylPPh₂) only produce methyl propanoate whilst a similar dendrimer with a -CH₂- spacer between Si and P (G1-16methylPPh₂) gives only copolymer. The effect of the molecular architecture is discussed in comparison with the selectivities observed when using small molecule analogues. A wide range of non dendritic monodentate phosphines has also been studied in this reaction showing that low steric bulk and high electron density favours polyketone formation. The poorly active, monodentate SemiEsphos phosphine has been turned into an active ligand for rhodium catalysed vinyl acetate hydroformylation by attachment to the periphery of a Polyhedral Oligomeric Silsesquioxane. Whilst some of these dendritic ligands have shown activity, others precipitated upon mixing with the rhodium precursor. Modelling studies correlating the experimental facts have shown that the former are more compact and rigid in comparison to the latter, which are more flexible and hence more prone to monodentate binding to rhodium and cross-linking. Grubbs cross metathesis has been used to functionalize octavinylsilsesquioxane with fluorescent vinylbiphenyl modified chromophores to design new hybrid organic-inorganic nanomaterials. Those macromolecules have been characterized by NMR, microanalyses, MALDI-TOF mass spectrometry and photoluminescence. This last method was shown to be an interesting tool in the analysis of the purity of the cube derivatives. Reduction of the peripheral 4`-vinylbiphenyl-3,5-dicarbaldehyde groups on a Polyhedral Oligomeric Silsesquioxane (POSS) with NaBH₄ or LiAlH₄ activates the fluorescence of this macromolecule by turning the aldehydic functions into primary alcohols providing novel optical sensors for reducing environments.

Ce travail de thèse est une contribution au développement d’afficheurs électroluminescents inorganiques utilisant le luminophore CaTiO3 :Pr3+ comme couche active. Il comporte deux volets. Le premier concerne l’étude du dépôt de CaTiO3 :Pr3+ par pulvérisation cathodique à partir d’une cible céramique élaborée au laboratoire et s’est plus particulièrement attaché à l’influence de la pression de dépôt et aux conditions de recuit (température, type de fours) sur les propriétés morphologiques, structurales, optiques et électriques des films. Les films obtenus sont cristallisés en structure orthorhombique, photoluminescents, transparents sur toute la gamme du visible et possèdent des propriétés électriques compatibles avec l’application visée. Des pistes d’optimisation de ces propriétés sont également avancées. Le second volet du travail utilise le modèle de transfert de charge par intervalence (TCIV) développé ces dernières années au laboratoire, pour orienter la recherche d’autres luminophores dopés par des ions Pr3+ utilisables dans des afficheurs électroluminescents. Sur cette base, des titanates de formulations (Ca,Sr)TiO3 :Pr3+, CaTiO3 :Bi3+ ;Pr3+ et Na1/2Ln1/2TiO3 :Pr3+ (Ln = La, Gd, Y, Lu) ont été synthétisés et caractérisés. L’évaluation détaillée du comportement de ces matériaux en photoluminescence a permis de valider le modèle TCIV, d’initier d’autres modèles et de mettre en évidence l’intérêt d’un codopage au bismuth pour accroître l’intensité de fluorescence de l’ion Pr3+ dans la matrice CaTiO3. Le luminophore rouge CaTiO3 :Bi3+ ; Pr3+ apparaît être un candidat intéressant pour des applications en électroluminescence. / This work reports on the pre-development of inorganic electroluminescent devices based on luminescent CaTiO3 :Pr3+ thin films. It includes two parts. The first part is dedicated to the deposition of CaTiO3: Pr3 + films by sputtering of a home-made target and post-treated for their crystallization. Influence of gas pressure during deposition and post-treatment conditions (temperature, oven…) on the morphology, structure, optical and electrical properties of the films was investigated. Finally, the possibility to obtain films crystallized in the orthorhombic phase, photoluminescent, transparent in the whole visible range and with electrical properties needed for the aimed application, was demonstrated. Conditions for further optimization are also given. The second part of the work aims to use the Intervalence Charge Transfer (IVCT) model that has been recently elaborated in the laboratory, as a tool for the design of new Pr3+-doped phosphors that could be integrated in electroluminescent devices. On this basis, the titanates (Ca,Sr)TiO3 :Pr3+, CaTiO3 :Bi3+ ;Pr3+ and Na1/2Ln1/2TiO3 :Pr3+ (Ln = La, Gd, Y, Lu) were prepared and characterized. The detailed analysis of the photoluminescence behaviors confirmed the IVCT model and allowed to propose new models. Further, the role of Bi3+ codopant as a sensitizer of the Pr3+ luminescence in CaTiO3 is demonstrated and interpreted. The red phosphor CaTiO3 :Bi3+ ;Pr3+ appears as a possible interesting candidate for applications in electroluminescence.

Il y a des indications que les nanocristaux de silicium (nc-Si) présentent un gain optique qui est potentiellement assez grand pour permettre l'amplification optique dans la gamme de longueurs d'ondes où une photoluminescence (PL) intense est mesurée (600- 1000 nm). Afin de fabriquer des cavités optiques, nous avons implantés des morceaux de silice fondue avec des ions de Si pour former une couche de nc-Si d'une épaisseur d'environ 1 μm. Le Si a été implanté à quatre énergies comprises entre 1 MeV et 1,9 MeV de manière à obtenir une concentration atomique de Si en excès variant entre 25% et 30%. Les pièces ont été flanquées de miroirs diélectriques composés de filtres interférentiels multicouches. Sur une plage de longueurs d'ondes d'environ 200 nm de large, un filtre réfléchit près de 100%, alors que l'autre a une réflexion moyenne d'environ 90%. Nous avons mesuré et comparé les spectres de PL de trois échantillons: le premier sans miroir, le second avec des filtres réfléchissant autour de 765 nm (entre 700 nm et 830 nm), et la troisième avec des filtres agissant autour de 875 nm (entre 810 nm et 940 nm). Lorsque les échantillons sont excités avec un laser pulsé à 390 nm, des mesures de photoluminescence résolue dans le temps (PLT) révèlent des taux de décroissance plus rapides en présence de miroirs dans le domaine de longueurs d'onde où ceux-ci agissent comparé aux échantillons sans miroirs. Aussi, l'intensité PL en fonction de la fluence d'excitation montre une augmentation plus rapide de la présence de miroirs, même si celle-ci reste sous-linéaire. Nous concluons que de l'émission stimulée pourrait être présente dans la cavité optique, mais sans dominer les autres mécanismes d'émission et de pertes. / There are indications that silicon nanocrystals (nc-Si) exhibit an optical gain that is potentially large enough to enable optical amplification in the wavelength range where intense photoluminescence (PL) is measured (600-1000 nm). We fabricated optical cavities on fused silica pieces ion-implanted with Si in order to form a nc-Si layer with a thickness of about 1 μm. Si was implanted at four energies between 1 MeV and 1.9 MeV to obtain an excess atomic concentration varying between 25% and 30%. The pieces were sandwiched between dielectric mirrors consisting of multilayer interference filters. Over a wavelength range of about 200 nm wide, one filter reflects nearly 100%, while the other one shows an average reflection of 90%. We measured and compared the PL spectra of three samples: the first one with no mirrors, the second one with filters reflecting around 765 nm (between 700 nm and 830 nm), and the third one with filters acting around 875 nm (between 810 nm and 940 nm). When exciting the samples with a pulsed laser, timeresolved PL measurements exhibited faster decay rates in the wavelength domain where the reflection of the mirrors is maximal compared to samples without mirrors. Also, PL intensity as a function of excitation flux showed a faster increase in the presence of mirrors, although the increase remained sub-linear. From this, we conclude that stimulated emission could be present in the optical cavity, but does not dominate the other emission and loss processes.

Les matériaux dopés avec des ions de terres rares continuent de faire l’objet de nombreuses recherches grâce à leur efficacité dans les domaines de la photonique et leurs applications dans les amplificateurs ou laser à fibre optique. Dans ce contexte, dans un premier temps, des massifs de silice (SiO2) dopée par des ions europium (Eu3+) ont été préparés par le processus Sol-Gel. Les propriétés de luminescence des ions de terres rares ont été étudiées dans ces massifs, ainsi que dans des massifs co-dopés avec du magnésium et traités thermiquement à 900°C. Les propriétés optiques des ions Eu3+ ont été étudiées aussi dans un environnement totalement différent : des nanoparticules de silice (NPSi). Ces différents matériaux ont été caractérisés par ICP-OES, MET, DRX, analyse de sorption et FT-IR. La première partie de ce manuscrit décrit comment la taille des NPSi, la quantité d’europium, le traitement thermique et la présence de magnésium modifient les propriétés de photoluminescence des ions Eu3+.Le second axe de ce travail de thèse concerne l'étude de la réactivité des ions fluorures dans le système ternaire SiO2-GeO2-LaF3. Plusieurs mélanges binaires et ternaires ont été élaborés et calciné à 1500°C puis étudiés par ATG, EDS-MEB, DRX et spectroscopie Raman. L'évaporation des ions F- a été mise en évidence via une réaction préférentielle avec le silicium (pour former SiF4) plutôt qu'avec le germanium. Dans le système ternaire, nous avons observé la formation de la phase La2Si2O7. / Rare earth ions doped materials continue to be the subject of several researches thanks to their efficiency in the fields of photonics and their applications in amplifiers or optical fiber lasers. In this context, firstly, silica bulks (SiO2) doped with europium ions (Eu3+) were prepared by Sol-Gel process. The luminescence properties of rare earth ions were studied in these bulks, as well as in bulks co-doped with magnesium and heat-treated at 900°C. The optical properties of Eu3+ ions have also been studied in a very different environment: silica nanoparticles (NPSi). These different materials were characterized by ICP-OES, TEM, XRD, sorption analysis and FT-IR. The first part of this manuscript describes how the size of the NPSi, the amount of europium, the heat treatment and the presence of magnesium modify the photoluminescence properties of Eu3+ ions.The second axis of this work concerns the study of the reactivity of fluoride ions in the ternary system SiO2-GeO2-LaF3. Several binary and ternary mixtures were prepared and heat-treated at 1500°C and then studied by TGA, EDS-SEM, XRD and Raman spectroscopy. The evaporation of F- ions has been evidenced by a preferential reaction with silicon (to form SiF4) rather than with germanium. In the ternary system, we observed the formation of La2Si2O7 phase.

L’intégration des communications optiques sur puce offre de vastes promesses en termes de performances et de réduction de la puissance consommée, les canaux optiques ne souffrant pas des nombreuses limitations des canaux métalliques. De plus, l’information codée optiquement permet d’atteindre des débits de données élevés par le biais du multiplexage en longueur d’onde. Afin de conserver la compatibilité avec les composants électroniques, les communications et composants optiques doivent s’intégrer dans la filière silicium. Cependant, ce dernier matériau ne permet pas d’envisager la réalisation de certaines fonctions optiques, en particulier la source laser. D’autres matériaux doivent ainsi être intégrés pour suppléer au silicium. Mes travaux de thèse portent sur l’intégration de nanotubes de carbone sur plate-forme silicium pour la photonique. Dans ces travaux, le potentiel des nanotubes de carbone pour la réalisation de sources optiques intégrées est exploré. Dans un premier temps, je proposerai des pistes de compréhension de l’apparition du gain optique dans les nanotubes de carbone semiconducteurs par analyse des temps de vie des excitons, mesurés en spectroscopie pompe-sonde. Ces temps de vie sont sensiblement rallongés lorsque la centrifugation des nanotubes de carbone, au cours de l’extraction, est poussée à des vélocités et des temps plus longs. Une explication envisagée est la réduction du nombre de défauts à la surface des nanotubes, ces défauts se comportant comme des centres de recombinaison non-radiatifs. D’autre part, une méthode efficace d’intégration des nanotubes de carbone sur guide d’onde silicium a été proposée. Cette méthode robuste et permet d’observer le couplage de la photoluminescence des nanotubes de carbone avec le mode optique du guide d’onde. Afin d’obtenir une interaction exaltée entre mode optique et nanotube de carbone, le couplage entre les nanotubes et différentes cavités photoniques, incluant microdisques, cavités Fabry-Pérot et micro-résonateurs en anneau, a été étudié. L’emploi en particulier de résonateurs en anneau permet d’observer la structuration de la photoluminescence des nanotubes de carbone par les modes de résonance de l’anneau. Différentes configurations ont été étudiées afin de compléter la compréhension des mécanismes de couplage : micro-photoluminescence, photoluminescence guidée et photoluminescence intégrée. / On-chip optical communication may increase drastically performances and consumption of communication systems. Indeed, optical channels do not face limitations that metallics interconnects do. Even better would be the achievable data rate due to the multiplexing possibility in optics. In order to keep compatibility with electronic devices, optical components and interconnects should be built in silicon. However, this material is not suitable for some optical function, such as laser sources. Thus, there is a need to integrate alternative materials to compensate for silicon weaknesses. My PhD work focuses on integration of carbon nanotube on silicon for photonics applications. In this work, potential use of carbon nanotube for light emission function is investigated. First, I will propose clue to understand the appearance of optical gain in semiconducting carbon nanotube. Such investigation is done by mean of pump-probe experiments, where the excitons lifetimes are measured. Those lifetimes slightly increase while centrifugation time and speed is increased, during the extraction process. A possible explanation is that defect-free carbon nanotubes are selected by the centrifugation process. In parallel, I worked on designing an efficient method to couple nanotubes photoluminescence with silicon waveguides. This method appears to be quite robust, and allows to observe coupling between the nanotube photoluminescence and the optical mode of the waveguide. In order to obtain a more intense interaction between the optical mode and carbon nanotubes, I investigated the coupling between carbon nanotubes and several photonic cavities, including microdisks, Fabry-Pérot cavities and ring resonators. Specifically, ring resonators allow to measure the photoluminescence of carbon nanotube structured by the resonant modes. Several configurations are studied to understand more in-depth the coupling mechanisms: micro-photoluminescence, guided photoluminescence and integrated photoluminescence.