Au cours de ce travail, nous avons décrit et mis en œuvre la fabrication de surfaces nanostructurées d’alumine par anodisation de feuilles d’aluminium de très grande pureté. Les paramètres morphologiques caractérisant la membrane d’oxyde que sont le diamètre des pores, leur profondeur et leur espacement sont finement contrôlés par les paramètres expérimentaux. Ces surfaces nanotexturées ont permis l’étude approfondie de l’interaction solide-liquide au sein des pores et de la physique de la ligne de contact devant composer avec les nano-aspérités de surface. Ces deux éléments ont pu être appréhendés par des mesures d’angles de contact à l’équilibre et d’hystérésis de mouillage. La modélisation des résultats a montré l’inadéquation des modèles classiques de CASSIE, WENZEL ou de capillarité à cette situation. L’adjonction du terme controversé de tension de ligne permet de bonnes prévisions. Nous montrons que cette interprétation n’est pas unique ; une diminution de l’énergie de surface due à la forte courbure des pores conduit à des résultats identiques. Une investigation théorique a été menée par l’intégration des forces de VAN DER WAALS. La baisse de l’énergie de surface est prévue mais dans des proportions insuffisantes. Le modèle peut être amélioré. Les mesures d’hystérésis ont dévoilé le pouvoir adhésif des surfaces nanoporeuses. À cause des forces de capillarité dans les pores, la ligne de contact ne peut jamais reculer. Les angles d’avancée ont montré que la ligne de contact a une épaisseur négligeable devant la dizaine de nanomètre. Elle peut en outre parfaitement contourner les pores, imprimant de fortes courbures à l’interface liquide-gaz à la base de la goutte. Sa forme tridimensionnelle a été abordée au travers d’un modèle numérique restant à perfectionner. / In this work, we have described and carried out the fabrication of nanostructured alumina surfaces by anodizing highly pure aluminum foils. The pore diameter, depth and spacing are finely controled through experimental parameters. These nanotextured surfaces allowed a thorough study of the solid-liquid interactions within the pores and of the contact-line constrained by the surface nanoasperities. Equilibrium contact-angle and wetting hysteresis measurements were helpful to apprehend them. Modeling the results has revealed the inability of classical CASSIE, WENZEL and capillarity models to properly match the situation. Adding the controversial line-tension term solves the problem and provides good predictions. Anyway, this interpretation is not unique. A lower surface energy within the pores due to their strong curvature yields the same modeling quality. This case has been theoretically investigated through the integration of VAN DER WAALS’ forces. A surface-energy decrease has been calculated but it is not as strong as required. The model still can be improved. Hysteresis measurements have highlighted the nanoporous surfaces are strongly adhesive. Because of the pore size, the capillarity is very marked and keeps the contact line from receding. The advancing contact angles have shown that the contact-line thickness is negligible with respect of ten nanometres. In addition, it can circumvent the pore openings which involves strong liquid–gas interface curvatures at the drop base. The three-dimensional liquid–gas interface shape has been studied with a numerical model that still has to be enhanced.

Biologically inspired materials are being developed with the aim of improving the integration of medical implants and minimizing non-desirable host reactions. A promising strategy is the design of topographically patterned surfaces that resemble those found in the extracellular environment. Nanoporous alumina has been recognized as a potential biomaterial and as an important template for the fabrication of nanostructures. In this thesis in vitro studies were done to elucidate the role of alumina nanoporosity on the inflammatory response. Specifically, by comparing alumina membranes with two pore sizes (20 and 200 nm in diameter). Complement and platelet activation were evaluated as well as monocyte/macrophage behaviour. Whole blood was incubated with the alumina membranes and thereafter the biomaterial surfaces were evaluated in terms of protein and platelet adhesion as well as procoagulant properties. The fluid phase was analyzed for complement activation products and platelet activation markers. Besides, human mononuclear cells were cultured on the alumina membranes and cell adhesion, viability, morphology and release of pro-inflammatory cytokines were evaluated. The results indicated that nanoporous alumina with 200 nm pores promotes higher complement activation than alumina with 20 nm pores. In addition, platelet response to nanoporous alumina was found to be highly dependent on the material porosity, as reflected by differences in adhesion, PMP generation and procoagulant characteristics. A clear difference in monocyte/macrophage adhesion and activation was found between the two pore size alumina membranes. Few but highly activated cells adhered to the 200 nm membrane in contrast to many but less activated monocytes/macrophages on the 20 nm surface. The outcome of this work emphasizes that nanotopography plays an important role in the host response to biomaterials. Better understanding of molecular interactions on nano-level will undoubtedly play a significant role in biomaterial implant development and will contribute to design strategies for controlling specific biological events.

Avec l'augmentation du nombre de dispositifs utilisant des nanostructures, tels les nanofils pour les systèmes photovoltaïques, les détecteurs, etc., il devient nécessaire de développer des techniques de fabrication de réseau d'objets de dimensions nanométrique à faible coût. Dans cette étude, nous utilisons les propriétés d'auto-assemblage combinées avec des méthodes « descendantes » pour créer des réseaux de nanostructures très denses et très organisés. En effet, nous proposons de produire des réseaux hexagonaux parfaits d'alumine poreuse (AAO) et de les utiliser pour la croissance confinée de fils de silicium (Si) par la technique de dépôt chimique en phase vapeur (CVD).L'AAO est naturellement obtenue par oxydation de l'aluminium dans un acide, mais ce processus seul n'apporte qu'une organisation des pores très faible. Nous présentons un procédé innovant utilisant la lithographie par nano-impression thermique pour pré-texturer l'aluminium avant son anodisation. Ainsi, nous obtenons des réseaux poreux hexagonaux parfait sur des surfaces allant jusqu'à 4 cm ². Toutes les caractéristiques géométriques de la membrane poreuse peuvent être ajustées en faisant varier les paramètres expérimentaux de l'anodisation. En outre, pour augmenter la densité du réseau et réduire le coût de fabrication du moule d'impression, nous avons développé des structures originales avec une croissance mixte de pores guidées et générer naturellement.Afin d'étudier les caractéristiques de ces réseaux et suivre leur évolution au cours de leur formation, nous présentons les résultats d'une étude de diffusion des rayons X aux petits angles réalisée in situ pendant la formation de l'AAO.L'AAO est finalement utilisée comme matrice guide pour la croissance auto-organisée de fils de Si par CVD. Nous présentons donc des réseaux hexagonaux parfaits de nanofils crus perpendiculairement à la direction <100 > des substrats de silicium. Les différentes étapes du procédé, du dépôt de catalyseur à la croissance des fils sont présentées. Grâce à cette technique, nous obtenons des densités de fils allant jusqu'à 9.109 cm-2 et la dispersion des diamètres est meilleure que lors d'une croissance colloïdale (CVD). La composition chimique et l'orientation cristalline des nanofils confirme qu'ils sont en silicium et que nous avons à la fois des orientations <100> et <111>. Nous avons étudié également la conductivité entre le sommet des fils et le substrat grâce à la technique du microscope à force atomique conducteur. / With the increased number of devices using functional nanostructures, e.g nanowires for photovoltaic systems, detector etc, it becomes of great importance to develop low-cost and versatile fabrication of systems with nano-objects. In this study, self-assembly properties combined with top-down methods were used to create highly dense and organized nanostructures. Indeed, flawless hexagonal porous anodic alumina arrays (PAA) were successfully used as a template for the epitaxial Silicon (Si) nanowires (NW) growth in a chemical vapor deposition reactor (CVD).PAA is naturally obtained by oxidation of aluminum in acid; however this simple process brings a poor pores organization. We present an innovative route using Thermal NanoImprint Lithography previous to aluminum anodization to prepare perfect hexagonal nanopore array on large surface (4 cm²). All the geometrical characteristics of the porous membrane can be adjusted by varying experimental parameters. Furthermore, to increase the density of the array and reduce the fabrication cost of the imprint mould, original structures with a mixed growth of NIL-guided pores and generation of naturally-guided pores (induced pores) have been developed. Shapes of the pores can be modified varying the electrolyte.To know the characteristic of these arrays and their evolution during formation, we will present the results of the hitherto unseen In Situ study under Grazing Incidence Small Angle X-ray Scattering of PAA formation.The PAA is finally used as templates for the self-organized Si NW growth in a CVD reactor. Hexagonal nanowire arrays grown perpendicularly to <100> silicon substrates were successfully produced. The different process steps from the catalyst deposition to the planarization of the array are presented. The quality of the final silicon array is discussed. Densities up to 9*109 NW.cm-2 and diameter dispersion better than colloidal growth are achieved. The chemical composition and the crystalline orientation of the nanowires confirms the nanowires are in silicon and a mix between <100> and <111> orientation. We also measured the conductivity between the top of the vertical nanowire and the substrate with conductive atomic force microscopy.

Aligned arrays of nanostructures has recently attracted great interest because of their unique properties and potential use in a broad range of technological applications. The nanostructures can be employed when it is essential to create large surface on a small area in electronic device as sensor technology or energetics e.g. solar panels. One of the simplest and low-cost methods of fabricating nanostructures is template-assisted electrochemical deposition. This method also enables good control over the nanostructure dimensions and can be used to deposit a wide range of materials. The proposed method consists of two steps. At first, a non-conductive nanoporous template has to be created and then nanostructures are formed by electrodeposition into the template which is coated with a metal on one of its sides or placed on a metal surface.

Spintronics or electronics that utilizes the spin degree of freedom of a single charge carrier (or an ensemble of charge carriers) to store, process, sense or communicate data and information is a rapidly burgeoning field in electronics. In spintronic devices, information is encoded in the spin polarization of a single carrier (or multiple carriers) and the spin(s) of these carrier(s) are manipulated for device operation. This strategy could lead to devices with low power consumption. This dissertation investigates spin transport in one dimensional and two dimensional semiconductors, with a view to applications in spintronic devices.

Le confinement de la matière condensée dans un milieu nanoporeux peut induire à l'échelle nanométrique des changements structurels ou dynamiques drastiques qui conduisent finalement aux propriétés originales. Le confinement des polyélectrolytes, qui sont des polymères porteurs d'une charge électrique, présente un intérêt particulier. Dans ce projet, des membranes d'alumine nanoporeuse auto-ordonnée (nPAAMs), dont les paramètres structuraux sont réglés par la synthèse, ont été choisies comme milieu de confinement et des approches expérimentales ont été proposées pour étudier le confinement d'un polyélectrolyte fort (PE), polystyrène-sulfonate de sodium. Une partie importante de ce travail a été consacrée à la caractérisation des charges structurales et superficielles des nPAAMs. La structure et la composition du nPAAM sont caractérisées par la combinaison de la microscopie électronique à balayage et de la diffusion neutronique à petit angle (SANS). Une stratégie détaillée est proposée pour mesurer les nPAAM dans des conditions optimales en raison de leur forme anisotrope et de leur pouvoir de diffusion élevé ainsi que des informations sur leur composition chimique. La charge superficielle de la membrane a été déterminée par des mesures de potentiel d’écoulement. La charge de la paroi du pore peut être ajustée à une charge positive ou négative et l'étendue des interactions électrostatiques peut être ajustée, ce qui permet d'adapter le milieu aux études de confinement électrostatique. Le comportement de perméation et l'adsorption du polyélectrolyte à l'intérieur des pores sont étudiés par SANS en combinaison avec des mesures de perméabilité. La cinétique de l'adsorption est obtenue par le potentiel d’écoulement et la possibilité d'utiliser la réflectivité neutronique pour ces études est proposée. Ce travail fournit des approches expérimentales sur la caractérisation de l'PE en milieu confiné. / The confinement of condensed matter in nanoporous medium can induce at the nanoscale drastic structural or dynamical changes that ultimately lead to original properties. Of a specific interest is the confinement of polyelectrolytes that are polymers carrying an electrical charge. In this project, self-ordered nanoporous alumina membranes (nPAAMs), whose structural parameters are tuned through the synthesis, have been chosen as a confining medium and experimental approaches have been proposed to study the confinement of a strong polyelectrolyte (PE), sodium polystyrene-sulfonate . An important part of this work has been devoted to the structural and surface charge characterization of nPAAMs. The nPAAM’s structure and composition are characterized by combining scanning electron microscopy and small angle neutron scattering (SANS). A detail strategy is proposed for measuring the nPAAMs under optimal conditions due to their anisotropic shape and high scattering power and information on their chemical composition. The membrane’s surface charge has been determined by streaming potential measurements. The pore’s wall charge can be adjusted to positive or negative charge and the extent of the electrostatic interactions can be tuned, tailoring the medium for electrostatic confinement studies. The permeation behavior and the adsorption of the polyelectrolyte inside the pores is studied by SANS combined with flow measurements. The kinetics of the adsorption is accessed by streaming potential and the possibility to use of neutron reflectivity for such studies is proposed. This work provides experimental approaches insight into the characterization of PE under confinement.

Les membranes d'alumine nano-poreuses suscitent depuis quelques années un grand intérêt dans la synthèse de nano-objets. Ces membranes présentent des pores très verticaux naturellement organisés en un réseau hexagonal (structure en nid d'abeilles). Le diamètre des pores peut varier entre 20 et 200nm espacés de 60 à 540nm et l'épaisseur de la membrane peut varier de 100nm à plusieurs centaines de µm. Durant ces travaux de thèse, deux approches ont été envisagées pour synthétiser des nano-structures. La première consiste à utiliser ces membranes comme nano-réservoirs. La couche barrière formée au fond de la membrane dont l'épaisseur est environ égale au diamètre des pores est diminuée à 10nm par voie chimique. Puis des dépôts de divers matériaux (Au, Co, Si) ont été réalisés dans des membranes avec des pores de 180nm et 40nm préalablement dégazées. Ces objets 3D ont été fabriqués sous ultra-vide (10-10 mbar), concfinés à l'intérieur des nano-réservoirs, transparents aux électrons. Les études en TEM permettent d'avoir accès à la morphologie des nanoparticules, qui se révèlent être cristallines, selon plusieurs directions cristallographiques. En vue plane, perpendiculairement à l'interface, pour ceux déposés au fond du nano-réservoir et en vue transverse pour ceux déposés sur les parois. Il a par ailleurs été possible de réaliser des études de recuits in-situ en température (RT à 1000° C) dansle TEM pour des particules d'or. La seconde approche repose sur l'utilisation des membranes ouvertes comme masque pour l'évaporation. Cette technique permet de dupliquer le motif de la membrane sur le substrat préalablement nettoyé pour former un réseau de nanoparticules correspondant au matériau déposé. Nous avons réalisé de manière reproductible, sous ultravide,des réseaux de plots d'or à l'aide de membranes dont le diamètre des pores est de 180 nm / The nanoporous alumina membrane rise in recent years a great interest in the synthesis of nanoobjects. These membranes have pores naturally very vertical organized in a hexagonal lattice(honeycomb structure). The pore diameter may vary between 20 and 200nm spaced 60 to 540nmand the thickness of the membrane can vary from 100nm several hundred microns. During this thesis work, two approaches have been explored to synthesize nano-structures. The first is touse these membranes as nano-tanks. The barrier layer formed at the bottom of the membrane whose thickness is about equal to the diameter of pores is reduced to 10nm by chemical etching. Then deposits from materials (Au, Co, Si) were performed in membranes with pores of 180nmand 40nm previously degassed. These 3D objects have been produced under ultra-high vacuum(10-10 mbar), confined within nano-tanks, transparent to electrons. TEM studies allow accessto the morphology of nanoparticles, which are proving to be crystallin, according to several crystallographic directions. In plane view perpendicular to the interface for those deposited atthe bottom of the nano-tank and cross-sectional view for those deposited on the walls. It has also been possible to perform studies of in-situ annealing (RT to 1000° C) in TEM of Au particles. The second approach relies on the use of membranes opened as an evaporation mask. This technique allows to duplicate the pattern of the membrane to the substrate previously cleaned, to form a network of nanoparticles corresponding to the material deposited. We have achieved reproducible, gold dot arrays, under UHV conditions using membranes with a pore size of 180 nm.

Les nanofils de silicium présentent un fort potentiel d'intégration, et leur utilisation dans des dispositifs électroniques tels que des cellules solaires photovoltaïques ne peut se faire que si leur élaboration et leurs propriétés structurales sont maitrisées. Nous présentons dans cette thèse une méthode de fabrication de matrices de nanofils de silicium par croissance catalysée par l'or ou le cuivre en dépôt chimique en phase vapeur et faisant appel à des matrices de guidage de la croissance en alumine nanoporeuse. Cette technique permet notamment la croissance d'assemblées de nanofils ultra-denses (1.10^{10} nanofils/cm²) sur substrat non préférentiel ou d'hétérostructures comme des nanofils de germanium sur substrat de silicium. Grâce à la diffraction des rayons X nous montrons ensuite que les nanofils produits sont de très bonne qualité structurale malgré leur substrat non préférentiel et la présence d'une légère déformation de leur maille cristalline. Le contrôle de la déformation cristalline de nanofils de germanium est par ailleurs démontré en encapsulant les nanofils dans une coquille de nitrure de silicium. De nouveaux éléments de réflexion sont également rapportés concernant la contamination des nanofils de silicium par le catalyseur de leur croissance. Enfin l'intégration des nanofils de silicium dans des dispositifs solaires photovoltaïques est démontré en faisant appel à des jonctions PN radiales entre le coeur et la coquille des nanofils. / Silicon nanowires are promising objects but their integration in electronic devices such as photvoltaic solar cells relies on the ability to control their production and tailor their structural properties. In this thesis we present a method to produce nanowire matrices using a gold or copper catalysed growth process by chemical vapor deposition and using a nanoporous alumina growth template. This method enables the fabrication of ultra-dense nanowire arrays (1.10^{10} nanowires/cm²) on non preferential substrate or heterostructures such as germanium nanowires on silicon substrate. Using X-ray diffraction we also show that the structural quality of the template grown nanowires is very good in spite of their non preferential substrate and the presence of a small cristalline lattice strain. The control of germanium nanowires strain is also demonstrated by embeding them in a silicon nitride shell. Besides, new results are presented concerning the catalyst contamination of silicon nanowires. Silicon nanowires integration in photovoltaic devices is eventually demonstrated using a radial geometry for the PN junction between the core and the shell of the nanowires.

Anodisation is a surface treatment process, commonly used to form a protective oxide coating on the surface of metals like aluminium. Anodised coatings, being grown out of the base metal have excellent interface strength but are porous and brittle. Porosity of the coating reduces the hardness and the brittle nature of the oxide induces cracking. In practice, the pores are typically filled with organic dye and sealed. Under certain controlled electrochemical conditions, anodisation results in a highly ordered hexagonal porous structure in pure aluminium. In this work, we explore the possibility of using this ordered porous alumina to form a novel metal nanocomposite as a tribological coating. By optimizing the nonporous structure and tuning the electrodeposition process, we uniformly filled the ordered pores with copper. We have measured the hardness of the resulting ordered and aligned nanocomposite. We explore the possibility of using this composite coating for tribological applications by carrying out some preliminary reciprocating wear test. Ordered porous alumina layer is formed by a two-step anodisation process. By optimizing the anodisation conditions, we control the thickness of the coating and the pore size. The interface of the porous structure and aluminium substrate is defined by a non-conducting dense barrier oxide layer. However, to deposit metal into the pores, a conducting path should be established through the barrier layer. One possibility is to etch out the bottom of the pores at the cost of the interface strength and losing out on the main advantage of anodised coatings. To be able to fill metal without this sacrifice, we utilised the dendritic structure in the barrier layer formed by a step-wise reduction of voltage towards the end of anodisation process. Optimisation of this dendritic structure led to uniform deposition of metal into pores, achieved by pulsed electrodeposition. In pulse lectrodeposition, a positive pulse is applied to remove accumulated charge near to the bottom of pores, followed by a negative pulse to deposit metal and a delay to allow diffusion of ions. By optimising the pulse shape and duration, we have achieved uniform growth of metal into pores. Further, monitoring the deposition current helped us to identify and control different phases of growth of the nanowire. The properties of the porous alumina and the nanocomposite were measured by nanoindentation. The deformation characteristics were obtained by observing the indents in a FE-SEM. We find that dendritic modification of interface has very little effect on the hardness of the porous alumina layer. We also found that the porous alumina deformed either by compaction or by forming circumferential and radial cracks. When copper is filled in the nano pores, the hardness increased by 50% and no circumferential cracks were found up to the load of 10 mN for a film thickness of about 1 µm. Coefficient of friction of the coating reciprocated against steel in dry condition is found to be around 0.4. Minimal wear was observed from the SEM images of wear track. In summary, a novel nanocomposite coating with ordered porous alumina as matrix embedded with aligned metal nano rods has been developed. This was achieved by optimally modifying the barrier layer without sacrificing the interfacial strength. Uniform coating has been achieved over an area of 10 mm x 10 mm. The coating is found to have high hardness and high wear resistance.

Nowadays, nanostructures fixed on solid substrates and colloidal nanoparticles permeate through all areas of human life, in area of sensors and detection as well. This dissertation thesis deals with the fabrication of nanostructures on the surface of planar electrodes via self-ordered nanoporous template of aluminum trioxide. The nanofabrication, as one of many possible techniques, is used to increase the active surface area of electrodes by creating unique surface types with specific properties. These electrodes are very perspective in the applications, such as biomolecules electrochemical detection and measurement. The transformation of aluminum layer into non-conductive nanoporous template in the process of anodic oxidation is a fundamental technique employed to obtain the array of nanostructures in this thesis. The fabrication of high quality nanoporous membranes with narrow pore size distribution on various types of metallic multilayers is one of the key experimental parts in this work. Several problems associated with the production of the thin-film systems, including the dissolving the barrier oxide layer, are discussed and solved. Another part of this work deals with the use of nanoporous membrane as a template for the production of metallic nanostructures via electrochemical metal ions deposition directly into the pores. The obtained nanostructures as nanowires, nanorods or nanodots are characterized by the scanning electron microscopy and energy-dispersive or wavelength X-ray spectroscopy. The electrode surface, modified by gold nanostructures suitable for the detection of biomolecules, has been chosen for the electrochemical measurements, due to the gold biocompatibility. The nanostructured electrodes were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The effect of nanostructured surface geometrical parameters, including the size of the electrochemically active area, on the results of electrochemical measurements has been observed and compared to flat gold electrodes. Two model biomolecules, namely guanine and glutathione, have been chosen for the study of potential application of these nanostructures in biosensors.