Os métodos geofísicos constituem um conjunto de várias ferramentas de investigação, com características específicas e com aplicação, em especial, no estudo de áreas submersas, tendo em vista a inacessibilidade as estes ambientes pelos métodos convencionais. Entretanto, sua aplicação nem sempre traz os resultados esperados e assim, o objetivo principal deste estudo é discutir e avaliar a aplicabilidade dos métodos geofísicos, com ênfase nos métodos sísmicos, em estudos de áreas submersas rasas: plataforma continental interna, áreas costeiras, rios, lagos e reservatórios. O estabelecimento de critérios que auxiliem a escolha do método geofísico mais adequado para a melhor solução ao problema geológico ou geotécnico colocado, visa, entre outros aspectos, contribuir para a mitigação dos problemas, principalmente ambientais, causados pela atividade antrópica concentrada nestes ambientes e ampliar o conhecimento geológico básico, propiciando deste modo intervenções sustentadas nestes complexos ambientes. / Geophysical methods consist of a series of investigation tools with specific features that are critical to the study of water-covered areas, since these environments cannot be reached with conventional methods. However, sometimes these applications fail to provide the expected results. The objective of this study is to discuss and assess the applicability of geophysical methods by focusing on seismic methods in studies conducted in shallow water-covered areas: inner continental shelves, coastal areas, rivers, lakes and reservoirs. Criteria to help to select the most appropriate geophysical method to solve geological or geotechnical issues must be established to minimize problems, particularly environmental problems caused by concentrated anthropic activity, and to expand basic geological knowledge to allow for sustained interventions in these complex environments. This study is based on extensive bibliographic research and on several projects developed by IPT (Institute for Technological Research of São Paulo State) and by IOUSP (Oceanography Institute of the University of São Paulo), in addition to partnerships with private companies and other institutes in Brazil that address this field of knowledge. The focus on shallow waters was driven by the lack of systematic data and the demand for geological and geotechnical knowledge in these areas, due to the concentration, in these sectors, of the main economic activities of our current society: projects to build or reassess port dimensions, installation of moles, ducts, marinas, bridges, tunnels, fishing activities, beach regeneration, mineral prospecting, waterways, dredging, installation of reservoirs for water storage or flood containment, and reservoir silting. In any of these topics, basic geological knowledge of the bottom and subbottom of water-covered areas is essential to ensure the venture’s success. Considering this, geophysical methods, particularly seismic ones, are investigation tools that effectively contribute to generate new information, and are the only set of tools available to quickly and objectively provide enough data to improve the geological understanding of the area under investigation. The result of this study includes a discussion on the feasibility of the methodologies recommended, based on an extensive survey conducted in 2005/2006 on the availability of geophysical equipment in research institutes and private companies in Brazil.

Due to the low amount or unfavorable annual distribution of precipitation the exploration, allocation, sustainable exploitation, and protection of replenishable as well as fossile water resources are challanging tasks in semiarid and arid regions. Beside a few natural or artifcial surface water reservoirs the porous underground at the same time is the largest storage and transport medium for water and provides protection against evaporation and to a certain degree against surcficial introduction of contaminants. This situation is characteristic for the Near East and thus for the selected investigation areas, that are located in Israel and the West Bank, and that are subject of the conducted partail studies that are presented. The work focuses on three main subjects. On the one hand, it deals with the characterization of the young groundwater components of the discharge of four major springs of Wadi Qilt and Jericho, as well as of sampled deep wells of three important well fields. All of these objects discharge or abstract water from the Upper and Lower Judea Group Aquifer. With a thickness of about 750 m it is one of the most important groundwater reservoirs of the region and comprises mainly to varying degrees karstified and fractured limestones and dolomites. These formations underwent uplift during Senonian to Eocenian times forming a pair of double-plunging anticlinal structures (Hebron and Ramallah or Judea and Samaria Mountains, respectively) that are again subdivided into minor anticlines and synclines. The groundwater replenishment is restricted to the winter season between October and April, and to the crestal area of the mountains, where the otherwise covered aquifer rocks crop out. A strategy was developed to interpret the applied tracers for all locations in a similar way using a lumped parameter approach, which enables a direct comparison. On the other hand, the work investigates salinization processes in the Shallow Aquifer of Jericho and their discrimination. Potential sources for salinization are remnant brines that are activated to flow into the range of well extraction due to groundwater overexploitation, dissolution of salts, or formation waters from the Lisan formation. These layers represent the sediments of Lake Lisan, the Pleistocene precursor of the Dead Sea. A discrimination of the salinization mechanisms is important to develope reasonable measures to limit or lower the salt concentration in the affected wells. Consequently, the relevant measured but also potential main hydrochemical indicators and isotope tracers are identified. The large uncertainties with respect to the establishment of a well-founded water balance and to the insuffcient knowledge about the geology of the small-scale area of Jericho are discussed. Because the interpretation of the measured helium samples from the fractured and karstified aquifer of the Cretaceous Judea Group is limited, the dependencies of the He-4 accumulation in groundwater in an idealized dual-continuum aquifer are investigated with respect to the relation of the He-4 mass fluxes and the system response time to the varied parameters (groundwater head gradient, hydraulic conductivities, dispersivities, porosities) by means of a sensitivity analysis. Although the system response time is not a system variable as such it clearly turned out that knowledge about it may be an important information for the interpretation of He concentrations in groundwaters of non-stationary systems. To enhance the visual post-processing of the parameter sensitivity analysis an easily interpretable way of data presentation is introduced.:Impressum Kurzfassung Abstract List of Figures List of Tables Introduction Geology and hydrogeological background Theory and application of environmental tracers to characterize groundwater flow Methodology Results Summary Conclusions / Semiaride und aride Gebiete stellen aufgrund des niedrigen oder ungünstig verteilten Niederschlagsdargebots eine besondere Herausforderung bezüglich Erkundung, Bereitstellung, nachhaltiger Nutzung und Schutz sich neu bildender, aber auch fossiler Wasserresourcen dar. Abgesehen von wenigen natürlichen oder künstlich angelegten Oberflächenreservoiren ist der poröse Untergrund dabei gleichzeitig Hauptspeicher und Transportmedium für Wasser und bietet einen Schutz gegen Verdunstung und bis zu einem gewissen Grade gegen oberflächig einwirkende Verunreinigungen. Diese Situation ist charakteristisch für den Nahen Osten und damit für die im Rahmen der vorliegenden Arbeit beschriebenen Teiluntersuchungsgebiete, die sich in Israel und der West Bank befinden. Die Arbeit behandelt drei Hauptthemen. Einerseits geht sie auf die Charakterisierung der Jungwasseranteile im Abfluß vier bedeutender Quellen des Wadi Qilts und Jerichos sowie in beprobten tiefen Brunnen dreier wichtiger Brunnenfelder ein. Alle diese Objekte entwässern bzw. entnehmen Wasser aus dem Oberen oder Unteren Judea Group Aquifer. Mit ca. 750 m Mächtigkeit stellt dieser eines der bedeutensten Grundwasserreservoire der Region dar und besteht hauptsächlich aus unterschiedlich stark verkarsteten und gestörten Kalkstein- und Dolomitformationen, welche zwischen dem Senon und Eozän in Form einer in sich weiter gegliederten, beid-seitig abtauchenden Doppelantiklinalstruktur herausgehoben wurde (Hebron und Ramallah bzw. Judea und Samaria Mountains). Die Grundwasserneubildung ist beschränkt auf die Zeit zwischen Oktober und April sowie auf die Kammlagen des Gebirges, wo die sonst bedeckten Schichten des Aquifers ausstreichen. Es wurde eine Strategie entwickelt, die eingesetzten Tracer auf ähnliche Weise mit Hilfe von Lumped Parameter-Modellen für alle Lokationen zu interpretieren und somit eine Vergleichbarkeit zu gewährleisten. Andererseits untersucht die Arbeit Versalzungsprozesse im Shallow Aquifer von Jericho und deren Abgrenzung untereinander. Mögliche Hauptquellen der Versalzung sind durch überhöhte Grundwasserentnahme verstärke Zuflüsse von Solen, die Lösung von Salzen aus der Lisan-Formation oder Formationswässer der Lisan-Formation, welche die Ablagerungen des Lisan-Sees, des Pleistozänen Vorgängers des heutigen Toten Meeres, repräsentieren. Eine Unterscheidung der Mechanismen hat dabei durchaus Bedeutung für die Festlegung geeigneter Gegenmaßnahmen. Demzufolge werden die ermittelten, aber auch weitere, potentielle hydrochemische Hauptindikatoren und Tracer benannt. Unsicherheiten sowohl hinsichtlich der Aufstellung einer Wasserbilanz, als auch einer unzureichend bekannten Geologie für das sehr kleinräumige Gebiet von Jericho werden diskutiert.:Impressum Kurzfassung Abstract List of Figures List of Tables Introduction Geology and hydrogeological background Theory and application of environmental tracers to characterize groundwater flow Methodology Results Summary Conclusions

Utilising tidal currents as a renewable energy resource is presently under consideration to meet the requirements of increasing worldwide energy demand and the need to reduce carbon emissions. In this respect, in-stream tidal devices are proposed to convert the kinetic energy of currents into useful extractable power. In order to extract a useful amount of energy from tidal currents, the proposed devices need to be deployed in an array or farm-like format. Due to the thrust exerted by the devices within an array, the natural flow regime will inevitably be changed. In light of this, this study aims to estimate the maximum power that can be extracted by tidal turbine arrays and assess the far-field effects of energy extraction in the designated areas around the UK for various array configurations. In this thesis, the ocean tides are modelled using the long wave equations, commonly referred as the shallow water equations (SWEs). A numerical solver based on a Runge-Kutta discontinuous Galerkin finite element method is employed to solve the SWEs. One main advantage of the discontinuous Galerkin method is that it approximates the solution individually at each element, which allows for discontinuities within the solution system while ensuring mass conservation locally and globally. The selected numerical solver has been verified against several benchmark tests. It is then modified to include a line discontinuity to represent the effect of tidal turbine array(s) in a coastal basin. The algorithm implemented in the numerical solver involves a sub-grid model, which is based on Linear Momentum Actuator Disk Theory (LMADT) to approximate the local flow-field in the presence of the turbines. This near-field approach allows the flow velocity at the turbine to be estimated with a greater accuracy. As the power available to the turbines is related to the velocity at the turbine blades, the characterisation of the designated tidal site as a resource using LMADT may be more accurate than previously proposed methods. An additional advantage of using LMADT is that it provides a distinction between the power extracted by the turbines and the total amount of power that is removed from the tidal stream, including the wake mixing losses. The methodology employed in this thesis has been applied to two tidal basins around the UK; the Anglesey Skerries (a headland) and the Bristol Channel (an oscillating bay). A comprehensive unstructured triangular finite element model has been constructed to simulate the naturally occurring tides at these regions. The constructed model has then been validated against field measurement. The validated model is used to conduct parametric studies, which evaluate the importance of tidal array locations, configurations and operating conditions on the available power at the Anglesey Skerries and the Bristol Channel sites. The parametric study aims to evaluate a realistic upper limit of available power at each site considered. This study also provides a unique analysis to examine the potential tidal farm interactions by deploying several tidal arrays at both Anglesey Skerries and the Bristol Channel.

Ice sheets, such as the Greenland Ice Sheet or Antarctic Ice Sheet, have a fundamental impact on landscape formation, the global climate system, and on sea level rise. The slow, creeping flow of ice can be represented by a non-linear version of the Stokes equations, which treat ice as a non-Newtonian, viscous fluid. Large spatial domains combined with long time spans and complexities such as a non-linear rheology, make ice sheet simulations computationally challenging. The topic of this thesis is the efficiency and error control of large simulations, both in the sense of mathematical modelling and numerical algorithms. In the first part of the thesis, approximative models based on perturbation expansions are studied. Due to a thick boundary layer near the ice surface, some classical assumptions are inaccurate and the higher order model called the Second Order Shallow Ice Approximation (SOSIA) yields large errors. In the second part of the thesis, the Ice Sheet Coupled Approximation Level (ISCAL) method is developed and implemented into the finite element ice sheet model Elmer/Ice. The ISCAL method combines the Shallow Ice Approximation (SIA) and Shelfy Stream Approximation (SSA) with the full Stokes model, such that the Stokes equations are only solved in areas where both the SIA and SSA is inaccurate. Where and when the SIA and SSA is applicable is decided automatically and dynamically based on estimates of the modeling error. The ISCAL method provides a significant speed-up compared to the Stokes model. The third contribution of this thesis is the introduction of Radial Basis Function (RBF) methods in glaciology. Advantages of RBF methods in comparison to finite element methods or finite difference methods are demonstrated. / eSSENCE

Agriculture and, more recently, oil and gas development have contributed to extensive degradation and loss of temperate grasslands. I investigated the landscape-scale effects of oil and gas development, and roads, on grassland birds in southern Alberta using abundance, clutch size and nesting success data collected from 2010-2014. I estimated: (i) the distance at which there are effects of edge, and effects of shallow gas well density, using piecewise regressions; (ii) the locations and extent of habitat affected by infrastructure for obligate grassland species– Baird’s Sparrow (Ammodramus bairdii), Chestnut-collared Longspur (Calcarius ornatus) and Sprague’s Pipit (Anthus spragueii); and generalist species – Clay-colored Sparrows (Spizella pallida), Horned Lark (Eremophila alpestris), Savannah Sparrow (Passerculus sandwichensis), Vesper Sparrow (Pooecetes gramineus) and Western Meadowlark (Sturnella neglecta), and (iii) the total area affected by wells and roads. My findings suggest that the effects of roads, overall, extended to further distances than edge effects associated with natural gas wells, obligate species had more habitat affected by infrastructure than generalist species and shallow gas wells affected more habitat than did oil wells, due to their greater density on the landscape. Additionally, obligates, on average, were negatively affected by proximity to edge where as generalists were more productivity closer to edge. Reducing fragmentation caused by roads, minimizing the spread of non-native vegetation and management of cattle around gas wells could improve habitat quality for these focal species. / February 2016

As the size of modern transistors is continuously scaled down, challenges rise in almost every component of a silicon device. Formation of ultra shallow junction (USJ) with high activation level is particularly important for suppressing short channel effects. However, the formation of low resistance USJ is made difficult by dopant Transient Enhanced Diffusion (TED) and clustering-induced deactivation. In this work, we proposed a novel point defect engineering solution to address the arsenic TED challenge. By overlapping arsenic doped region with silicon interstitials and vacancies, we observed enhanced and retarded arsenic diffusion upon anneal, respectively. We explain this phenomenon by arsenic interstitial diffusion mechanism. In addition, we implemented this interstitial-based mechanism into a kinetic Monte Carlo (kMC) simulator. The key role of interstitials in arsenic TED is confirmed. And we demonstrated that the simulator has an improved prediction capability for arsenic TED and deactivation. As a long time unsolved process challenge, arsenic segregation at SiO₂/Si interface was investigated using density functional theory (DFT) calculation. The segregation-induced arsenic dose loss not only increases resistance but also may induce interface states. We identified three arsenic complex configurations, [chemical formula] , [chemical formula] and [chemical formula], which are highly stabilized at SiO₂/Si interface due to the unique local bonding environments. Therefore, they could contribute to arsenic segregation as both initial stage precursors and dopant trapping sites. Our calculation indicates that arsenic atoms trapped in such interface complexes are electrically inactive. Finally, the formation and evolution dynamics of these interface arsenic-defect complexes are discussed and kMC models are constructed to describe the segregation effects. A potential problem for the p-type USJ formation is the recently found transient fast boron diffusion during solid phase epitaxial regrowth process. Using DFT calculations and molecular dynamics simulation, we identified an interstitial-based mechanism of fast boron diffusion in amorphous silicon. The activation energy for this diffusion mechanism is in good agreement with experimental results. In addition, this mechanism is consistent with the experimentally reported transient and concentration-dependent features of boron diffusion in amorphous silicon. / text

Bed topography identification in open channel and glacier flows is of paramount importance for the study of the respective flows. In the former, the knowledge of the channel bed topography is required for modelling the hydrodynamics of open channel flows, fluvial hydraulics, flood propagation, and river flow monitoring. Indeed, flow models based on the Shallow Water Approximation require prior information on the channel bed topography to accurately capture the flow features. While in the latter, usable bedrock topographic information is very important for glacier flow modellers to accurately predict the flow characteristics. Experimental techniques to infer the bed topography are usually used but are mostly time consuming, costly, and sometimes not possible due to geographical restrictions. However, the measurement of free surface elevation is relatively easy. Alternative to experimental techniques, it is therefore important to develop fast, easy-to-implement, and cost-effective numerical methods. The inverse of the classical hydrodynamic problem corresponds to the determination of hydraulic parameters from measurable quantities. The forward problem uses model parameters to determine measurable quantities. New one-shot and direct pseudo-analytical and numerical approaches for reconstructing the channel bed topography from known free surface elevation data is developed for one-dimensional shallow water flows. It is shown in this work that instead of treating this inverse problem in the traditional partial differential equation (PDE)-constrained optimization framework, the governing equations of the direct problem can be conveniently rearranged to obtain an explicit PDE for the inverse problem. This leads to a direct solution of the inverse problem which is successfully tested on a range of benchmark problems and experimental data for noisy and noiseless free surface data. It was found that this solution approach creates very little amplification of noise. A numerical technique which uses the measured free surface velocity to infer the channel bed topography is also developed. The one-dimensional shallow water equations along with an empirical relationship between the free surface and the depth averaged velocities are used for the inverse problem analysis. It is shown that after a series of algebraic manipulation and integration, the equation governing the inverse problem simplifies to a simple integral equation. The proposed method is tested on a range of analytical and experimental benchmark test cases and the results confirm that, it is possible to reconstruct the channel bed topography from a known free surface velocity distribution of one-dimensional open channel flows. Following the analysis of the case of one-dimensional shallow water flows, a numerical technique for reconstructing the channel bed topography from known free surface elevation data for steep open channel flows is developed using a modified set of equations for which the zero-inertia shallow water approximation holds. In this context, the shallow water equations are modified by neglecting inertia terms while retaining the effects of the bed slope and friction terms. The governing equations are recast into a single first-order partial differential equation which describes the inverse problem. Interestingly, the analysis shows that the inverse problem does not require the knowledge of the bed roughness. The forward problem is solved using MacCormack’s explicit numerical scheme by considering unsteady modified shallow water equations. However, the inverse problem is solved using the method of characteristics. The results of the inverse and the forward problem are successfully tested against each other. In the framework of full two-dimensional shallow water equations, an easy-to-implement and fast to solve direct numerical technique is developed to solve the inverse problem of shallow open channel flows. The main underlying idea is analogous to the idea implemented for the case of one-dimensional reconstruction. The technique described is a “one-shot technique” in the sense that the solution of the partial differential equation provides the solution to the inverse problem directly. The idea is tested on a set of artificial data obtained by first solving the forward problem. Glaciers are very important as an indicator of future climate change or to trace past climate. They respond quickly compared to the Antarctica and Greenland ice sheets which make them ideal to predict climate changes. Glacier bedrock topography is an important parameter in glacier flow modelling to accurately capture its flow dynamics. Thus, a mathematical technique to infer this parameter from measured free surface data is invaluable. Analogous to the approaches implemented for open channel flows, easy-to-implement direct numerical and analytical algorithms are developed to infer the bedrock topography from the knowledge of the free surface elevation in one space dimension. The numerical and analytical methods are both based on the Shallow Ice Approximation and require the time series of the ablation/accumulation rate distribution. Moreover, the analytical method requires the knowledge of a non-zero glacier thickness at an arbitrary location. Numerical benchmark test cases are used to verify the suitability and applicability of the algorithms.

Coarse-grained beaches are particularly prevalent in the UK, composed of accumulations of either gravel, or mixed sand and gravel sediments. The aim of the work presented in this thesis is to improve capabilities for predicting coarse-grained beach 2D profile development. In particular, the effects of infiltration and sediment sorting are considered. In this study, the public domain numerical model, XBeach (v12) is developed further. This model was initially developed for studying sandy environments especially for the case of dune erosion. Here, the model is modified to enhance its capability to predict beach profile change on coarse-grained beaches. Improvements include: use of Lagrangian interpretation of velocity in place of Eulerian for driving sediment movement; introduction of a new morphological module based upon Soulsby’s sediment transport equation for waves and currents; incorporation of Packwood’s infiltration approach in the unsaturated area of the swash region; and implementation of a multiple sediment fraction algorithm for sediment sorting of mixed sediments. These changes are suggested and justified in order to significantly improve the application of this model to gravel and mixed beaches, especially with regard to swash velocity asymmetry which is responsible for development of the steep accretionary phase steep berm above waterline and sediment sorting. A comparison between model simulation and large scale experiments is presented with particular regard to the tendency for onshore transport and profile steepening during calm conditions; offshore transport and profile flattening during storm conditions; and sediment sorting in the swash zone. Data used for this and the model calibration comes from the Large Wave Channel (GWK) of the Coastal Research Centre (FZK) in Hannover, Germany. The results are found to agree well with the measured experimental data on gravel beach profile evolution. This is due to the inclusion of infiltration in the model which weakens the backwash volume and velocity in a more satisfying manner than through the use of asymmetric swash friction and transport coefficient. The model also simulates sediment sorting of a mixed sediment beach. However, the profile comparisons were not satisfactory due to limitations of the numerical model such as the constant permeability rate used throughout the simulation and the non-conservation of the sediment volume in the laboratory data by an order of 50%. From the simulation, it was found that the fine sediment moves offshore and the coarser sediment moves onshore. This is because of infiltration weakens the backwash velocity; the coarser sediment moving onshore barely moves back offshore while the fine sediment remains in motion. This pattern agrees with the pattern obtained from sediment samples analysis in the experiment and provides an explanation for the existence of composite beaches. The model is also shown to be capable of switching from accretionary to erosive conditions as the wave conditions become more storm-like. Again, the model simulations were in a good agreement with the observations from the GWK dataset. Numerical model simulations on the effects of the tidal cycle on coarse-grained beach profile evolution were also carried out. This preliminary investigation showed that the model was able to predict the anticipated profile change associated with a coarse-grained beach under such wave and tidal forcing. Tidally forced accretion and erosion were compared with those predicted under similar beach sediments and wave conditions for constant water level. The main differences are that the affected area is wider and the berm is located on the upper beach during flood for both gravel and mixed beaches. Therefore, the model developed in this study can be seen to be a robust tool with which to investigate cross-shore beach profile change on coarse-grained beaches and sediment sorting on mixed beaches. Further work is also indicated.

The bulk of the research work in wave related areas considers sea waves as stochastic objects leading to wave forecasting techniques based on statistical approaches. Due to the complex dynamics of the sea waves’ behaviour, statistical techniques are probably the only viable approach when forecasting over substantial spatial and temporal intervals. However this view changes when limiting the forecasting time to a few seconds or when the goal is to estimate the quiescent periods that occur due to the beating interaction of the wave components, especially in narrow band seas. This work considers the multi disciplinary research field of deterministic sea wave prediction (DSWP), exploring different aspects of DSWP associated with shallow angle LIDAR systems. The main goal of this project is to study and develop techniques to reduce the prediction error. The first part deals with issues related to shallow angle LIDAR systems data problems, while the remaining part of this work concentrates on the prediction system and propagation models regardless of the source of the data. The two main LIDAR data problems addressed in this work are the non-uniform distribution and the shadow region problems. An empirical approach is used to identify the characteristics of shadow regions associated with different wave conditions and different laser position. A new reconstruction method is developed to address the non-uniformed sampling problem, it is shown that including more information about the geometry and the dynamics of the problem improves the reconstruction error considerably. The frequency domain approach to the wave propagation model is examined. The effect of energy leakage on the prediction error is illustrated. Two approaches are explored to reduce this error. First a modification of the simple dispersive phase shifting filter is tested and shown to improve the prediction. The second approach is to reduce the energy leakage with an iterative Window-Expansion method. Significant improvement of the prediction error is achieved using this method in comparison to the End-Matching method typically used in DSWP systems. The final part in examining the frequency domain approach is to define the prediction region boundaries associated with a given prediction accuracy. The second propagation model approach is the Time/Space domain approach. In this method the convolution of the measured data and the propagation filter impulse response is used in the prediction system. In this part of the research work properties of these impulse responses are identified. These are found to be quite complicated representations. The relation between the impulse response (duration and shift) with prediction time and distance are studied. Quantification of these impulse responses properties are obtained by polynomial approximation and non-symmetric filter analysis. A new method is shown to associate the impulse response properties to the prediction region of both the Fixed Time and Fixed Point mode.

Depuis les années 1970, la taille des composants n’a cessé de diminuer. La réalisation de jonctions ultra-minces et fortement dopées est devenue un point clef dans la réduction des dispositifs microélectroniques. Les techniques de production doivent évoluer afin de répondre aux spécifications drastiques, en termes de taille des zones dopées et de leurs propriétés électriques, des prochains noeuds technologiques. Dans ce travail de thèse nous avons étudié le procédé d’activation au laser de dopants implantés par immersion plasma. Le laser à excimère utilisé (ArF) est absorbé dans moins de 10 nmde silicium, ce qui va permettre un recuit local. De plus, la courte durée d’impulsion va assurer un faible budget thermique, limitant la diffusion des dopants. En associant cette technique à l’implantation ionique par immersion plasma, dont l’intérêt est de pouvoir travailler à de très basses tensions d’accélération (quelques dizaines d’eV), nous pouvons réaliser des jonctions avec un fort taux d’activation sans diffusion. Après avoir présenté les différentes techniques de dopage pouvant être utilisées, nous avons décrit les dispositifs expérimentaux de traitement et de caractérisation utilisés. Des simulations ont permis de comprendre le rôle des paramètres laser sur le profil de température du siliciumen surface. Après avoir choisi le laser le plus adapté parmi les lasers ArF, KrF et XeCl (respectivement: 193 nm - 15 ns, 248 nm - 35 ns, 308 nm - 50 ns), nous avons observé l’effet du nombre de tirs et de la mise en forme de faisceau afin d’optimiser le procédé. Pour terminer, des inhomogénéités dues aux bords de faisceau ont été mises en évidence et étudiées afin d’enlimiter l’effet. / Since the 1970’s, the components size has steadily declined. The realization of highly-dopedultra shallow junctions became a key point in the reduction of microelectronic devices. Them anufacturing processes must evolve to meet the stringent specifications of the next technologynodes, in particular in terms of dimension and electrical properties of the doped area.In this thesis we have studied the process of laser annealing of dopants implanted by plasmaimmersion. The ArF excimer laser we used is absorbed in less than 10 nm of silicon, whichallows a local heating. Moreover, the short pulse duration provides a low thermal budget whichreduces the dopant diffusion. By combining this technique with plasma immersion ion implantation, which is interesting because of the very low acceleration voltage (few tens of eV), we can produce highly activated junctions without diffusion. After a presentation of the different doping techniques that may be used, we describe the experimental treatment and the characterization tools that we used. We have used numerical simulations to understand the role of the laser parameters on the temperature profile of the silicon surface. After choosing the most suitable laser between ArF, KrF and XeCl (respectively :193 nm - 15 ns, 248 nm - 35 ns, 308 nm - 50 ns), we studied the influence of the number of shots and beam shaping to optimize the process. Finally, inhomogeneities caused by the beam edgeshave been studied and identified in order to improve the laser scan process.