FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Os sistemas de lagoas de estabilizaÃÃo, bastante presentes em aterros sanitÃrios normalmente nÃo sÃo suficientes para o atendimento aos padrÃes ambientais de descarte de lixiviado tratado em Ãguas superficiais. Este trabalho avaliou o emprego das tecnologias aerÃbias do tipo reator aerado submerso (RAS) e reator em batelada seqÃencial (RBS) como opÃÃes de pÃs-tratamento para lixiviado antigo prÃ-tratado em lagoas de estabilizaÃÃo. A coleta do lixiviado se deu na saÃda da Ãltima lagoa de estabilizaÃÃo do sistema de tratamento de lixiviado (duas anaerÃbias em sÃrie, seguidas de uma facultativa) localizadas no Aterro SanitÃrio Metropolitano Oeste (ASMOC), municÃpio de Caucaia, RegiÃo Metropolitana de Fortaleza, estado do CearÃ. Inicialmente foi realizada uma caracterizaÃÃo fÃsico-quÃmica do lixiviado efluente e verificaÃÃo do atendimento aos padrÃes de descarte. O RAS foi operado em cinco fases, sendo divididas entre esgoto sintÃtico e lixiviado, este Ãltimo testado com e sem diluiÃÃo. Avaliou-se o efeito da adiÃÃo de fonte externa de carbono, etanol, para a fase em que o reator era alimentado com lixiviado sem diluiÃÃo. O RBS foi confeccionado em acrÃlico, em formato cilÃndrico, com um volume Ãtil de 5,0L, sendo inicialmente estudado o tempo de operaÃÃo de cada ciclo de 24 horas. Posteriormente, foram avaliados no RBS os tempos totais de ciclo de 12 e 48 horas, alÃm do efeito da adiÃÃo de etanol no desempenho do reator. Os reatores foram instalados no LaboratÃrio de Saneamento (Labosan) do Departamento de Engenharia HidrÃulica e Ambiental (DEHA) da Universidade Federal do Cearà (UFC). Eles foram operados na faixa mesofÃlica, com temperatura ambiente prÃxima de 27ÂC. Em relaÃÃo ao lixiviado tratado, os valores encontrados na caracterizaÃÃo fÃsico-quÃmica confirmam a recalcitrÃncia e complexidade do lixiviado, indicando que apenas as lagoas de estabilizaÃÃo, nÃo atendem plenamente os padrÃes de descarte. A presenÃa de compostos recalcitrantes e tÃxicos no lixiviado afluente ao RAS durante um dos perÃodos de investigaÃÃo causou diminuiÃÃo na remoÃÃo de DQO, mostrando efeito inibitÃrio nos microrganismos presentes no inÃculo. Entretanto, em outra fase de investigaÃÃo, tanto o RAS quanto o RBS se mostraram eficientes e estÃveis na remoÃÃo de DQO e nitrogÃnio amoniacal, mesmo tratando lixiviado sem diluiÃÃo. A adiÃÃo de etanol como fonte externa de carbono foi benÃfica para suprir as necessidades metabÃlicas microbianas, fazendo aumentar tanto a eficiÃncia global do RAS e RBS em termos de remoÃÃo de matÃria orgÃnica (DQO), assim como na estabilidade operacional dos mesmos. O RAS e o RBS foram tambÃm bastante eficientes no processo de nitrificaÃÃo. O estudo no RBS com os tempos de ciclo de 12, 24 e 48 h revelaram que nÃo houve diferenÃa entre os tempos em relaÃÃo à remoÃÃo dos constituintes analisados, fazendo com que se considerasse 12 h como tempo Ãtimo de ciclo, de forma a minimizar os custos com volume do reator e tempo de aeraÃÃo. Como conclusÃo geral do experimento pode-se dizer que o tratamento biolÃgico aerÃbio, tanto utilizando reatores aerados submerso (RAS) quanto reatores em batelada seqÃencial (RBS), pode ser considerado uma boa alternativa para o pÃs-tratamento de lixiviado antigos provenientes de sistemas de lagoas de estabilizaÃÃo, mas ainda requer adequaÃÃes operacionais ou associaÃÃes com processos fÃsico-quÃmicos ou de oxidaÃÃo avanÃados para o enquadramento de todos os constituintes. / The system of stabilization ponds, which is often present in landfills, is usually not efficient to meet environmental standards for disposal of treated leachate on surface waters. This study evaluated the use of submerged aerated reactor (SAR) and sequencing batch reactor (SBR) as post-treatment options for old leachate pre-treated in waste stabilization ponds. The leachate collection took place at the outflow of the last stabilization pond of the treatment system (two anaerobic em series, followed by a facultative pond) located in West Metropolitan Landfill (ASMOC), Caucaia municipality, metropolitan region of Fortaleza, Cearà state. A physical-chemical characterization of the leachate effluent was performed to verify the compliance to reach disposal standards. The SAR was operated in five phases, being divided between synthetic wastewater and leachate, the latter tested with and without dilution. We evaluated the effect of adding an external carbon source, ethanol, for the phase in which the reactor was fed with leachate without dilution. SBR was made of acrylic, in a cylindrical shape with a working volume of 5.0 L and the total time cycle of 24 hours was initially studied. The total time cycles of 12 and 48 hours were also evaluated in the SBR performance, as well as the effect of adding ethanol as carbon source. The reactors were installed at the Laboratory of Sanitation (Labosan) of the Department of Hydraulic and Environmental Engineering (DEHA), Federal University of Cearà (UFC). They were operated in the mesophilic range, with temperature near 27  C. Regarding the treated leachate, the physical-chemical characterization confirmed its recalcitrance and complexity, indicating that only the stabilization ponds did not fully meet the standards of disposal. The presence of recalcitrant and toxic compounds in the leachate influent to the SAR during the investigation period decreased COD removal, showing an inhibitory effect on the microorganisms present in the inoculum. However, in another research phase, both the SAR and SBR were stable and efficient on COD and ammonia removals, even when undiluted leachate was used. The addition of ethanol as external carbon source was beneficial to meet the microbial metabolic needs, increasing both the overall efficiency of SAR and SBR in terms of organic matter removal (COD) and operational stability. The SAR and SBR were also quite efficient in the nitrification process. The study with SBR with cycle times of 12, 24 and 48 h showed no considerable difference amongst the constituent removals, so that 12 h was considered as optimal time cycle in order to minimize the costs with reactor volume and aeration time. As a general conclusion of the experiment we can say that the aerobic biological treatment, using either submerged aerated reactor (SAR) or sequencing batch reactors (SBR), can be considered a good alternative for post-treatment of old leachate pre-treated in stabilization ponds, but still requires operational adjustments and associations with physical-chemical or advanced oxidation processes for accomplish all discharge standards.

O Nitreto de Gálio (GaN) é um semicondutor de gap direto, motivo de numerosas pesquisas científicas, principalmente devido a sua importância na fabricação de dispositivos de alta potência e optoeletrônicas. Ligas de GaN como InGaN e AlGaN, por exemplo, possibilitam a fabricação de LEDs e LASERs azuis. Neste nosso estudo selecionamos o Arseneto de Gálio (GaAs) como um substrato viável para síntese de GaN mediante a permuta de Arsênio (As) por Nitrogênio (N) fundamentada em três passos: a) incorporação de N por implantação iônica em GaAs (à 350, 450 ou 550 ºC) em elevadas fluências (1, 2, 3 ou 4 × 1017 N/cm2); b) maior estabilidade das ligações Ga-N frente às de Ga-As; e c) expurgo de As da região contendo N implantado mediante recozimentos (à 550, 650, 750, 850 ou 1000 ºC) sob fluxo de N2. Uma capa de ~ 125 nm de Nitreto de Silício (Si3N4) foi depositada por sputtering sobre o GaAs previamente a implantação à quente: camada de sacrifício que pode ser removida após a síntese. Análises por Microscopia Eletrônica de Transmissão (TEM) e Espectroscopia de Raios- X por Dispersão em Energia (EDS) demonstraram que, no estado como-implantado da fluência de 3 × 1017 N/cm2, formam-se bolhas de N para ambos os lados da interface Si3N4/GaAs e a região implantada do GaAs amorfiza. Após um recozimento à 850 ºC/5 min, observou-se uma elevada degradação da camada de Si3N4, fragilizada pela formação das bolhas de N. Formou-se uma camada contínua de GaN (GaN-layer) de ~ 70 nm na sua fase hexagonal, sustentada por “pilares” no substrato GaAs, entre os quais existem extensos vazios. Medidas TEM em alta resolução (HRTEM) e por Difração de Elétrons de Área Selecionada (SAED) revelaram que a GaN-layer apresenta forte tendência à epitaxia com o substrato GaAs (relações de epitaxia são aqui apresentadas), e regiões estruturalmente espelhadas (i.e., twins). SAED sobre os pilares evidenciaram uma fase transicional cúbica, com um parâmetro de rede substancialmente menor (0,42 ± 0,01) nm que o reportado na literatura (0,45 nm). Estudos por Espectrometria de Retroespalhamento de Rutherford e Canalização (RBS/C) mostraram que a GaN-layer é rica em N (Ga1,00N1,90, para 3 × 1017 N/cm2) e apresenta canalização (para implantações de 2 e 3 × 1017 N/cm2), confirmando o caráter monocristalino identificado por TEM. Medidas de Fotoluminescência (PL) confirmam emissão na região do gap de banda do α-GaN (~ 3,4 eV), bem como bandas associadas a defeitos estruturais do material. Também foi investigado o efeito de campos de tensão provenientes de bolhas de Hélio (He) mediante a realização da síntese a partir de substrato GaAs pré-implantado com He. Neste caso, as bolhas, que se formam no GaAs durante a implantação de N à quente e extinguem-se após recozimentos, limitam a difusão de N para o interior do substrato, conduzindo a formação de uma GaN-layer mais espessa (~ 120 nm) e com bem mais N (Ga1,00N2,80). Como consequência, a GaNlayer apresentou um caráter mais policristalino. / The Gallium Nitride (GaN) is a direct gap semiconductor, is issue of numerous scientific research, mainly due to its importance in the manufacture of high power devices and optoelectronic devices. GaN alloys, as InGaN and AlGaN, for example, enable the production of LEDs and blue LASERs. In this study, we have selected Gallium Arsenide (GaAs) as a suitable substrate for GaN synthesis through Arsenic (As) replacement by Nitrogen (N), based on three steps: a) incorporation of N by ion implantation into GaAs (at 350, 450 or 550 ºC) at high fluences (1, 2, 3 or 4 × 1017 N/cm2); b) higher stability of the Ga-N bonds compared to the Ga-As ones; and c) purge of As from the region containing implanted N by annealing (at 550, 650, 750, 850 or 1000 ºC) under N2 flow. A 125-nm cap-layer of Silicon Nitride (Si3N4) was deposited by sputtering on GaAs prior to the hot implantation: it is a sacrifice layer which can be removed after the synthesis. Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDS) analyzes demonstrated that, on the as-implanted state of the fluence of 3 × 1017 N/cm2, N bubbles are formed on both sides of the Si3N4/GaAs interface and the implanted region of GaAs amorphizes. After annealing at 850 °C/5min, a high degradation of the Si3N4 layer was observed, weakened by the formation of N bubbles. A continuous layer of GaN (GaN-layer) of ~ 70 nm was formed in its hexagonal phase, supported by “pillars” on the GaAs substrate, with extensive voids in between them. High-Resolution TEM (HRTEM) and Selected Area Electron Diffraction (SAED) measurements revealed that the GaN-layer exhibits a strong tendency to epitaxy with the GaAs substrate (epitaxial relationships are here presented), and structurally mirrored regions (i.e., twins). SAED on the pillars showed a transitional cubic phase, with a lattice parameter substantially smaller (0.42 ± 0.01) nm than the one reported in the literature (0.45 nm). Rutherford Backscattering Spectrometry studies and Channeling (RBS/C) showed that the GaN-layer is rich in N (Ga1.00N1.90, for 3 × 1017 N/cm2) and presents channeling (for implantations of 2 and 3 × 1017 N/cm2), corroborating the monocrystalline nature identified by TEM. Photoluminescence (PL) measurements confirm emission in the band gap region of a- GaN (~ 3.4 eV), as well as bands associated to structural defects in the material. It was also investigated the effect of strain fields from Helium (He) bubbles through synthesis starting up from He pre-implanted GaAs substrate. In this case, the bubbles, which are formed in the GaAs during the hot N-implantation and are annihilated after annealing, limit the N diffusion into the substrate, leading to the formation of a thicker GaN-layer (~ 120 nm) and with much more N (Ga1.00N2.80). As a result, the GaN-layer presented an aspect more polycrystalline.

This thesis is aimed at preparation of thin plasma-polymerized films deposited on glass fibers by Plasma-Enhanced Chemical Vapor Deposition (PE CVD) from a mixture of tetravinylsilane (TVS) and oxygen gas. Plasma-polymerized films which were deposited on silicon wafers were used to characterize chemical properties and optimization of deposition process with respect to reproducibility.

High performance polymer composites are materials with emphasis on specific chemical and mechanical properties due to their broad scope of applications. The main advantages are high strenght and toughness in comparison with their low weight and density. An increased adhesion at composite interfaces is important to ensure excellent composite properties. Bundles of glass fibers were coated by plasma-polymerised interlayers of tetravinylsilane (pp-TVS) of different thicknesses and at different effective powers. The prepared interlayers of pp-TVS were analyzed to evaluate chemical composition (RBS, FTIR, XPS) and mechanical properties (NI-AFM). Microindentation test and fiber-bundle pull-out test were used to determine the interfacial shear strenght.

The aim of this work was to find a correlation between the electrical, optical and microstructural properties of thin SiO2 layers containing group IV nanostructures produced by ion beam synthesis. The investigations were focused on two main topics: The electrical properties of Ge- and Si-rich oxide layers were studied in order to check their suitability for non-volatile memory applications. Secondly, photo- and electroluminescence (PL and EL) results of Ge-, Si/C- and Sn-rich SiO2 layers were compared to electrical properties to get a better understanding of the luminescence mechanism.

Im Sommer 1999 wurde im Forschungszentrum eine Zweistrahlführung in Betrieb genommen. Dieses System gestattet, Ionenarten aus unterschiedlichen Beschleunigern gleichzeitig in die Experimentierstationen zu lenken. In der Doppelimplantationsstation wird die Zweistrahlführung zur Synthese neuartiger Materialien genutzt. In der Analysestation wird die Zweistrahlführung in Kombination mit einem magnetischen Browne-Buechner-Spektrometer eingesetzt, um komplexe und hochgenaue Materialanalysen durchzuführen. Das System überträgt Ionen des gesamten Teilchen- und Energiespektrums von 3-MV-Tandetron-Beschleuniger und 500-kV-Ionenimplanter mit minimalen Intensitätsverlusten zu den Experimenten. Steuerung und Kontrolle von Beschleunigern, Strahlführung und Experiment erfolgen in einem hierarchischen Rechnernetz. Die hier beschriebene Zweistrahlanlage ist Teil eines Projekts zur umfassenden Kopplung von Basisgeräten des Forschungszentrums.

Among the well-known methods to form or modify the composition and physical properties of thin films, ion implantation has shown to be a very powerful technique. In particular, ion beam syntheses of binary iron silicide have been studied by several groups. Further, the interests in transition metal silicide systems are triggered by their potential use in advanced silicon based opto-electronic devices. In addition, ternary silicides have been by far less studied than their binary counterparts despite the fact that they have interesting magnetic and electronic properties. In this study, we investigate ion beam synthesis of Fe-Si binary structures and Fe-Co-Si ternary structures. This work involves fundamental investigation into development of a scalable synthesis process involving binary and ternary transitional metal silicide thin films and Nano-structures using low energy ion beams. Binary structures were synthesized by implanting Fe- at 50 keV energy. Since ion implantation is a dynamic process, Dynamic simulation techniques were used in these studies to determine saturation fluences for ion implantation. Also, static and dynamic simulation results were compared with experimental results. The outcome of simulations and experimental results indicate, dynamic simulation codes are more suitable than static version of the TRIM to simulate high fluence, low energy and, heavy ion implantation processes. Furthermore, binary Fe-Si phase distribution was determined at different implantation fluences and annealing temperatures. A higher fluence implantation at 2.16×1017 atoms/cm2 and annealing at 500 oC showed three different Fe-Si phase formations (β-FeSi2, FeSi and Fe3Si) in substrate. Further, annealing the samples at 800 oC for 60 minutes converted the Fe3Si phase into FeSi2 and FeSi phases. As an extension, a second set of Fe- ion implantations was carried with the same parameters while the substrate was placed under an external magnetic field. External magnetic fields stimulate the formation of magnetic phase centers in the substrate. X-ray diffraction (XRD) results shows formation of ferromagnetic Fe3Si phase in the Si matrix after annealing at 500 oC for 60 minutes. In addition, X-ray photoelectron spectra (XPS) provide further evidence for ferromagnetic metallic behavior of Fe3Si in the substrate. Ternary Fe-Co-Si structures were synthesized by implanting Fe- & Co- into a Si (100) substrate at an energy of 50 keV at saturation fluences. Both Fe- & Co- co-implantation were performed under external magnetic fields to enhance magnetic phase formation. Fe(1-x)CoxSi B20-type cubic structure can be synthesized on Si(100) substrate with 0.4≤x≤0.55 concentration range using ion implantation under external magnetic field. Moreover, magnetic measurement indicates a possible magnetic phase transformation at ~50 K. Further, XPS results also provide evidence for metallic & ferromagnetic properties in the thin film structure

Recombinant DNA technology has been commonly used in a number of fields to synthesize new products or generate products with a new pathway. Conventional cloning methods are expensive and require significant time and labor; λ-PCR, a new cloning method developed in the Senger lab, has a number of advantages compared to other cloning processes due to its employment of relatively inexpensive and widely available materials and time-efficiency. While the amount of lab work required for the cloning process is minimal, the importance of accurate primer design cannot be overstated. The target of this study was to create an effective procedure for λ-PCR primer design that ensures accurate cloning reactions. Additionally, synthetic ribosome binding sites (RBS) were included in the primer designs to test heterologous protein expression of the cyan fluorescent reporter with different RBS strengths. These RBS sequences were designed with an online tool, the RBS Calculator. A chimeric primer design procedure for λ-PCR was developed and shown to effectively create primers used for accurate cloning with λ-PCR; this method was used to design primers for CFP cloning in addition to two enzymes cloned in the Senger lab. A total of five strains of BL21(DE3) with pET28a + CFP were constructed, each with the same cyan fluorescent protein (CFP) reporter but different RBS sequences located directly upstream of the start codon of the CFP gene. Expression of the protein was measured using both whole-cell and cell-free systems to determine which system yields higher protein concentrations. A number of other factors were tested to optimize conditions for high protein expression, including: induction time, IPTG concentration, temperature, and media (for the cell-free experiments only). Additionally, expression for each synthetic RBS sequence was investigated to determine an accurate method for predicting protein translation. NUPACK and the Salis Lab RBS Calculator were both used to evaluate the effects of these different synthetic RBS sequences. The results of the plate reader experiments with the 5 CFP strains revealed a number of factors to be statistically significant when predicting protein expression, including: IPTG concentration, induction time, and in the cell-free experiments, type of media. The whole-cell system consistently produced higher amounts of protein than the cell-free system. Lastly, contrasts between the CFP strains showed each strain's performance did not match the predictions from the RBS Calculator. Consequently, a new method for improving protein expression with synthetic RBS sequences was developed using relationships between Gibbs free energy of the RBS-rRNA complex and expression levels obtained through experimentation. Additionally, secondary structure present at the RBS in the mRNA transcript was modeled with strain expression since these structures cause deviations in the relationship between Gibbs free energy of the mRNA-rRNA complex and CFP expression. / Master of Science / Recombinant DNA technology has been used to genetically enhance organisms to produce greater amounts of a product already made by the organism or to make an organism synthesize a new product. Genes are commonly modified in organisms using cloning practices which typically involves inserting a target gene into a plasmid and transforming the plasmid into the organism of interest. A new cloning process developed in the Senger lab, λ-PCR, improves the cloning process compared to other methods due to its use of relatively inexpensive materials and high efficiency. A primary goal of this study was to develop a procedure for λ-PCR primer design that allows for accurate use of the cloning method. Additionally, this study investigated the use of synthetic ribosome binding sites to control and improve expression of proteins cloned into an organism. Ribosome binding sites are sequences located upstream of the gene that increase the molecule’s affinity for the rRNA sequence on the ribosome, bind to the ribosome just upstream of the beginning of the gene, and initiate expression of the gene. Tools have been developed that create synthetic ribosome binding sites designed to produce specific amounts of protein. For example, the tools can increase or decrease expression of a gene depending on the application. These tools, the Salis Lab RBS Calculator and NUPACK, were used to design and evaluate the effects of the synthetic ribosome binding sites. Additionally, a new method was created to design synthetic ribosome binding sites since the methods used during the design process yielded inaccuracies. Each strain of E. coli contained the same gene, a cyan fluorescent protein (CFP), but had different RBS sequences located upstream of the gene. Expression of CFP was controlled via induction, meaning the addition of a particular molecule, IPTG in this system, triggered expression of CFP. Each of the CFP strains were tested with a variety of v conditions in order to find the conditions most suitable for protein expression; the variables tested include: induction time, IPTG (inducer) concentration, and temperature. Media was also tested for the cell-free systems, meaning the strains were grown overnight for 18 hours and lysed, a process where the cell membrane is broken in order to utilize the cell’s components for protein expression; the cell lysate was resuspended in new media for the experiments. ANOVA and multiple linear regression revealed IPTG concentration, induction time, and media to be significant factors impacting protein expression. This analysis also showed each CFP strain did not perform as the RBS Calculator predicted. Modeling each strain’s CFP expression using the RBS-rRNA binding strengths and secondary structures present in the RBS allowed for the creation of a new model for predicting and designing RBS sequences.

Metal/semiconductor interfaces, particularly those involving Si, are of great technological and scientific interest. In atomically abrupt interfaces, many properties are determined by interatomic interactions over a few layers, i.e., over ~1 nanometer. The initial stages of growth of an atomic layer related to structural and electronic properties are thus important to thin film behavior. Surface science studies on metal-semiconductor systems often lead to contradictory conclusions regarding bonding sites and even whether the first layer is metallic or not. A key piece of information that must be consistent with any study is the number of atoms per unit area in the first layer, which is difficult to assess directly. Alkali-metal-semiconductor systems have been studied as model abrupt interfaces for several years. Novel effects, such as electron localization, were observed. Still, determinations of absolute coverage have been lacking. This dissertation describes results of absolute coverage measurements for Cs on Si(100)(2X1), Si(111)(7X7), and Si (111)(v3 X v3)R30°-B reconstructed surfaces using Rutherford Backscattering Spectrometry in ultrahigh vacuum. The results bracket possible structural models for these systems. For the Cs/Si(111)(v3 X v3)R30°-B interface, this work confirms conclusions regarding electron localization effects and introduces considerations of ion-beam-induced desorption for the weakly-bound Cs

L’intégration de semiconducteurs III-V à gap direct sur silicium est un enjeu de taille pour le développement de l’optoélectronique. En effet, si le silicium est aujourd’hui à la base de la microélectronique, la nature indirecte de son gap en fait un très mauvais émetteur de lumière. Parmi les matériaux candidats à l’intégration, l’In(Ga)As présente l’avantage d’un gap direct plus faible que le silicium, favorisant un comportement de puits de potentiel pour les paires électrons-trous. En revanche, le fort désaccord paramétrique entre les deux matériaux fait de la croissance épitaxiale d’In(Ga)As sur silicium un sérieux défi pour le physicien. Cette thèse est focalisée sur l’étude par faisceaux d’ions de boîtes quantiques (BQs) d’In(Ga)As épitaxiées sur silicium et de leur encapsulation ultérieure par du silicium. L’analyse par rétrodiffusion élastique à haute énergie (RBS) a permis de quantifier la composition des îlots d’In(Ga)As et de la couche cap de Si. Des phénomènes d’exo-diffusion d’indium et la présence d’espèces en excès ont été mis en évidence. En pratiquant l’analyse en géométrie de canalisation (RBS-C), nous avons pu caractériser l’épitaxie des BQs sur le substrat ainsi que celle de la couche cap. La deuxième technique utilisée dans ce travail est l’analyse par rétrodiffusion élastique à moyenne énergie (MEIS), qui permet de profiler composition, défauts cristallins, et déformation avec une résolution sub-nanométrique au voisinage de la surface de la cible. Les spectres MEIS en modes aléatoire et canalisé ont permis d’obtenir le profil de composition et de défauts du plan de BQs. Enfin, la déformation du cristal d’In(Ga)As par rapport au monocristal de silicium du substrat a été étudiée grâce à l’effet de blocage du flux d’ions rétrodiffusés qui permet d’observer les ombres des axes et des plans cristallographiques. / The integration on silicon of direct band gap materials such as some semiconductors from the III-V group is of a rising interest for tomorrow's optoelectronic devices. Although silicon is the raw material for many microelectronic devices, it has a poor light emitting efficiency due to his indirect band gap. Among the III-V family, the In(Ga)As compounds present the advantage of a smaller band gap than silicon, which encourage the confinement of electron-hole pairs. However, the large lattice mismatch between silicon and In(Ga)As is a serious limitation for the epitaxial integration. This PhD work has been focused on the ion beam study of In(Ga)As quantum dots (QDs) grown by epitaxy on silicon and of the QD capping by silicon. Rutherford Backscattering Spectrometry (RBS) has been used to quantify composition of both QDs and cap layer. Exo-diffusion and excess issues of some elements have been pointed out. The epitaxial relation between QDs and substrate have been investigated by ion channelling (RBS-C). Medium Energy Ion Scattering (MEIS) has also been used to obtain high resolution profiles of composition, defects and strain for both the QD plane and the capping layer. Direct space mapping of both crystals has also been achieved by MEIS thanks to the blocking effect.