High-k/metal gate stacks have been introduced in CMOS technology during the last decade in order to sustain continued device scaling and ever-improving circuit performance. Starting from the 45 nm technology node, the stringent requirements in terms of equivalent oxide thickness and gate current density have rendered the replacement of the conventional SiON/poly-Si stack unavoidable. Although Hf-based technology has become the de facto industry standard for high-k/metal gate MOSFETs, problematic long-term scalability has motivated the research of novel materials and solutions to fulfill the target performances expected of gate stacks in future technology nodes. In this work, integration of a high-k interfacial layer has been identified as the most promising approach to improve gate dielectric scalability, since this technology presents the advantage of potential compatibility with both current Hf-based and plausible future higher-k materials. Thulium silicate has been selected as candidate material for integration as interfacial layer, thanks to its unique properties which enabled the development of a straightforward integration process achieving well-controlled and repeatable growth in the sub-nm thickness regime, a contribution of 0.25+-0.15 nm to the total EOT, and high quality of the interface with Si. Compatibility with industry-standard CMOS integration flows has been kept as a top priority in the development of the new technology. To this aim, a novel ALD process has been developed and characterized, and a manufacturable process flow for integration of thulium silicate in a generic gate stack has been designed. The thulium silicate interfacial layer technology has been verified to be compatible with standard integration flows, and fabrication of high-k/metal gate MOSFETs with excellent electrical characteristics has been demonstrated. The possibility to achieve high performance devices by integration of thulium silicate in current Hf-based technology has been specifically demonstrated, and the TmSiO/HfO2 dielectric stack has been shown to be compatible with the industrial requirements of operation in the sub-nm EOT range (down to 0.6 nm), reliable device operation over a 10 year expected lifetime, and compatibility with common threshold voltage control techniques. The thulium silicate interfacial layer technology has been especially demonstrated to be superior to conventional chemical oxidation in terms of channel mobility at sub-nm EOT, since the TmSiO/HfO2 dielectric stack achieved ~20% higher electron and hole mobility compared to state-of-the-art SiOx/HfO2 devices at the same EOT. Such performance enhancement can provide a strong advantage in the EOT-mobility trade-off which is commonly observed in scaled gate stacks, and has been linked by temperature and stress analyses to the higher physical thickness of the high-k interfacial layer, which results in attenuated remote phonon scattering compared to a SiOx interfacial layer achieving the same EOT. / <p>QC 20140512</p>

Lasers sintonizáveis ao redor de 2,3 &#956;m são interessantes para várias áreas, como detecção de gases, sensoriamento remoto e aplicações médicas. O túlio é o principal sistema entre os lasers de terras-raras com essa emissão e pode ser bombeado diretamente ou por meio de um sensibilizador como o itérbio. Neste trabalho, apresenta-se a obtenção de um laser de Yb:Tm:YLF com emissão de 620 mW em 2,3 &#956;m bombeado em 960 nm por diodo-laser de 20 W do tipo barra em regime quase-contínuo. Investiga-se o bombeamento de um cristal de Tm:YLF em 685 nm e obtém-se de forma inédita um laser de Yb:Tm:YLF bombeado simultaneamente em 685 e 960 nm. Demonstra-se teórica e experimentamente sua maior eficiência em relação ao bombeamento apenas por 960 nm. Por meio de simulações numéricas e soluções analíticas, mostra-se a melhor relação de potência de bombeamento de cada comprimento de onda para se otimizar o laser. / Tunable lasers emitting around 2.3 &#956;m region are important in many areas, like gas detection, remote sensing and medical applications. Thulium has a large emission spectra around 2.3 &#956;m with demonstrated tuning range of 2.2-2.45 &#956;m using the YLF host. For efficient pump absorption, a high concentration sensitizer like ytterbium can be used. We demonstrate quasi-cw operation of the Yb:Tm:YLF laser, pumped at 960 nm with a 20 W diode bar achieving the highest output power reported so far of 620 mW. Simultaneous pumping of the 2.3mm Yb:Tm:YLF laser at 685 nm and 960 nm is demonstrated, showing higher slope efficiency than 960 nm alone. Numerical simulations and analytical models show the best ratio of pump power between both wavelengths.

Lasers sintonizáveis ao redor de 2,3 &#956;m são interessantes para várias áreas, como detecção de gases, sensoriamento remoto e aplicações médicas. O túlio é o principal sistema entre os lasers de terras-raras com essa emissão e pode ser bombeado diretamente ou por meio de um sensibilizador como o itérbio. Neste trabalho, apresenta-se a obtenção de um laser de Yb:Tm:YLF com emissão de 620 mW em 2,3 &#956;m bombeado em 960 nm por diodo-laser de 20 W do tipo barra em regime quase-contínuo. Investiga-se o bombeamento de um cristal de Tm:YLF em 685 nm e obtém-se de forma inédita um laser de Yb:Tm:YLF bombeado simultaneamente em 685 e 960 nm. Demonstra-se teórica e experimentamente sua maior eficiência em relação ao bombeamento apenas por 960 nm. Por meio de simulações numéricas e soluções analíticas, mostra-se a melhor relação de potência de bombeamento de cada comprimento de onda para se otimizar o laser. / Tunable lasers emitting around 2.3 &#956;m region are important in many areas, like gas detection, remote sensing and medical applications. Thulium has a large emission spectra around 2.3 &#956;m with demonstrated tuning range of 2.2-2.45 &#956;m using the YLF host. For efficient pump absorption, a high concentration sensitizer like ytterbium can be used. We demonstrate quasi-cw operation of the Yb:Tm:YLF laser, pumped at 960 nm with a 20 W diode bar achieving the highest output power reported so far of 620 mW. Simultaneous pumping of the 2.3mm Yb:Tm:YLF laser at 685 nm and 960 nm is demonstrated, showing higher slope efficiency than 960 nm alone. Numerical simulations and analytical models show the best ratio of pump power between both wavelengths.

Graduation date: 2005

Les travaux présentés dans ce manuscrit de thèse s'inscrivent dans l'étude et la réalisation de sources lasers impulsionnelles à fibre autour de 2 µm. Le travail présenté dans ce manuscrit se décline en deux parties. Une première partie est consacrée à l'étude des sources lasers fibrées à commutation de gain émettant des impulsions d'une durée de quelques nanosecondes. Une source a été réalisée et caractérisée, elle génère des impulsions de 10 ns de durée, 16 µJ d'énergie et 1,6 kW de puissance crête. Les impulsions sont ensuite amplifiées dans une fibre à large cœur pour atteindre plus de 150 µJ d'énergie et 13 kW de puissance crête, l'ensemble de la source étant totalement fibré. La deuxième partie est consacrée à l'étude des sources à verrouillage de mode autour de 2 µm. Un oscillateur totalement fibré fonctionnant en régime solitonique a été réalisé et caractérisé, il génère des impulsions de 4,5 ps de durée et 62 pJ d'énergie. Ces impulsions sont ensuite amplifiées afin d'atteindre plus de 8 kW de puissance crête et 30 nJ d'énergie sans l'accumulation significative de nonlinéarités. Les limites de l'amplification des impulsions dans ces deux différents régimes sont étudiées et discutées avec l'appui de modèles numériques.

Loin de seulement guider la lumière, les fibres optiques s'avèrent être extrêmement polyvalentes. Dotées de fonctions passives tel qu'un filtrage spectral, elles sont à la base de très nombreux capteurs de contraintes (température, pression, allongement, etc). Dopées d'ions de terres rares, elles acquièrent des propriétés de luminescence exploitées pour la réalisation d'amplificateurs ou de lasers. Parmi les matériaux utilisés pour préparer des fibres, la silice est le verre de référence. Les fibres à base de silice possèdent de très bonnes propriétés mécaniques, une très grande transparence et peuvent être produites à grande échelle. Cependant, certaines caractéristiques (énergie des phonons, solubilité, etc) de ce verre peuvent être néfastes pour les propriétés optiques des ions de terres rares. Depuis ma prise de fonction en tant que CR2 CNRS en 2002 au LPMC (Nice), mes activités de recherche concernent la conception, la fabrication et la caractérisation de fibres optiques à base de silice. En particulier, je m'intéresse aux propriétés spectroscopiques des ions de terres rares. Le premier projet présenté concerne l'efficacité des émissions issues du niveau 3H4 de Tm3+. Celle-ci est pratiquement nulle à cause de l'énergie élevée des phonons de la silice. Une étude matériau, spectroscopique et la mise en place de simulations numériques ont permis de rendre compatible ces fibres avec des applications d'amplificateurs vers 1,47 µm (pour la bande S des télécommunications) et des lasers autour de 810 nm (télécommunications, médical, etc). Un autre projet vise à s'affranchir des limitations de la silice en encapsulant les ions de terres rares dans des particules de taille nanométrique. Une voie de synthèse originale de ces nanoparticules est proposée, basée sur des mécanismes de séparation de phase mettant à profit les traitements thermiques appliqués lors du procédé standard de fabrication de préformes de fibres optiques (MCVD). Ces travaux et les autres présentés dans ce tapuscrit ont été menés dans le cadre de collaborations nationales et internationales. Ils ont aussi été l'occasion de nombreux stages pour des étudiants de licence, master, thèse et post-doc. Le dernier chapitre permet de compléter le tour d'horizon de mes activités : administration de la recherche, enseignements dispensés à l'Université de Nice-Sophia Antipolis, actions de diffusion de la culture scientifique, etc

comme luminophore rouge dans les nouveaux dispositifs de visualisation à panneaux plasma ; le borate Li6(Y,Gd)(BO3)3: Ce3+ est particulièrement approprié pour la détection des neutrons. Outre les borates Li6Ln(BO3)3 (Ln = terre rare) et Li3Ln2(BO3)3 antérieurement connus, l'étude des diagrammes ternaires Li2O-B2O3-Ln2O3 a mis en évidence l'existence de quatre autres compositions : les borates Li3Ln(BO3)2 et les oxyborates LiLn6O5(BO3)3, LiLn2O2BO3 et<br />Li2Ln5O4(BO3)3. Chacune des structures a été résolue sur monocristal par diffraction des rayons X.<br />Une caractéristique des oxyborates est l'existence d'un assemblage de tétraèdres OLn4, tridimensionnel<br />dans les borates LiLn6O5(BO3)3 , bidimensionnel dans les phases Li2Ln5O4(BO3)3 et LiLn2O2BO3 , les groupes (BO3)3- et les ions Li+ se disposent dans des cavités ou entre les couches de ces sous-réseaux. Une étude de la luminescence des ions Eu3+, Tm3+ et Ce3+ a été effectuée afin notamment d'évaluer les performances de ces nouveaux matériaux en tant que luminophores ou scintillateurs. Pour la première fois dans des composés du bore, une luminescence de transfert de charge du lanthane et du cérium tétravalent a par ailleurs été observée.

Inelastic collision processes driven by anistropic interactions are investigated below 1 K. Three distinct experiments are presented. First, for the atomic species antimony (Sb), rapid relaxation is observed in collisions with \(^4He\). We identify the relatively large spin-orbit coupling as the primary mechanism which distorts the electrostatic potential to introduce significant anisotropy to the ground \(^4S_{3/2}\) state. The collisions are too rapid for the experiment to fix a specific value, but an upper bound is determined, with the elastic-to-inelastic collision ratio \(\gamma \leq 9.1 x 10^2\). In the second experiment, inelastic \(\mathcal{m}_J\)-changing and \(J\)-changing transition rates of aluminum (Al) are measured for collisions with \(^3He\). The experiment employs a clean method using a single pump/probe laser to measure the steady-state magnetic sublevel population resulting from the competition of optical pumping and inelastic collisions. The collision ratio \(\gamma\) is measured for both \(\mathcal{m}_J\)- and \(J\)-changing processes as a function of magnetic field and found to be in agreement with the theoretically calculated dependence, giving support to the theory of suppressed Zeeman relaxation in spherical \(^2P_{1/2}\) states [1]. In the third experiment, very rapid atom-atom relaxation is observed for the trapped lanthanide rare-earth atoms erbium (Er) and thulium (Tm). Both are nominally nonspherical \((L \neq 0)\) atoms that were previously observed to have strongly suppressed electronic interaction anisotropy in collisions with helium \((\gamma > 10^4-10^5, [2,3])\). No suppression is observed in collisions between these atoms \((\gamma \lesssim 10)\), which likely implies that evaporative cooling them in a magnetic trap will be impossible. Taken together, these studies reveal more of the role of electrostatic anisotropy in cold atomic collisions. / Physics

Made available in DSpace on 2014-10-09T12:51:44Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:03Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:51:44Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:03Z (GMT). No. of bitstreams: 0 / Lasers sintonizáveis ao redor de 2,3 &#956;m são interessantes para várias áreas, como detecção de gases, sensoriamento remoto e aplicações médicas. O túlio é o principal sistema entre os lasers de terras-raras com essa emissão e pode ser bombeado diretamente ou por meio de um sensibilizador como o itérbio. Neste trabalho, apresenta-se a obtenção de um laser de Yb:Tm:YLF com emissão de 620 mW em 2,3 &#956;m bombeado em 960 nm por diodo-laser de 20 W do tipo barra em regime quase-contínuo. Investiga-se o bombeamento de um cristal de Tm:YLF em 685 nm e obtém-se de forma inédita um laser de Yb:Tm:YLF bombeado simultaneamente em 685 e 960 nm. Demonstra-se teórica e experimentamente sua maior eficiência em relação ao bombeamento apenas por 960 nm. Por meio de simulações numéricas e soluções analíticas, mostra-se a melhor relação de potência de bombeamento de cada comprimento de onda para se otimizar o laser. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP