L'étude des propriétés luminescentes de nanoparticules permet d'accéder à des informations sur les mécanismes élémentaires liés à cette luminescence. À l'instar de ce qui a été fait pour les semiconducteurs (effets de confinement quantique par exemple), nous souhaitons étudier l'influence de paramètres tels que la taille ou la composition de nanoparticules isolantes sur leur luminescence. Pour cela il fallait créer un outil polyvalent capable d'exciter efficacement ces particules, d'en effectuer des images luminescentes et enfin d'en faire la spectroscopie. Le microscope confocal achromatique élaboré dans le cadre de mon travail de thèse et hébergé au sein de Nanoptec est à même de remplir ces objectifs : longueur d'onde d'excitation accordable allant de l'UV dur (210 nm) à l'IR (près de 1 μm), résolution spatiale de l'ordre du μm (permet l'étude de particules assez espacées), aspect confocal permettant d'isoler spatialement la luminescence de l'objet étudié, système de détection capable d'isoler spectralement cette luminescence... Cet outil a permis des collaborations diverses avec des équipes au sein et hors du laboratoire, comme la cartographie spatiale de la répartition de dopants dans des fibres laser, l'évaluation des inhomogénéités lumineuses au sein de matériaux céramiques, la mesure de dispersion spatiale de nanoparticules dans des plastiques... Le microscope confocal achromatique nous sert également à étudier plus fondamentalement les effets de la puissance d'excitation sur les propriétés luminescentes de nanoparticules de tailles et de compositions diverses.

Neutrino-nucleon scattering is an effective way to investigate the inner structure of the nucleon, to extract the Standard Model parameters and to explore heavy quarks production dynamics. In the last decades, several experiments have been constructed to study weak interactions of neutrinos with nucleons. One of them was CERN-WA95 experiment operated by the CHORUS collaboration. It is based on a hybrid detector with nuclear emulsion as a target followed by electronic devices. Nuclear emulsion provides three dimensional spatial information with an outstanding resolution of the order of one micron. Therefore, it is ideal to detect short-lived particles. A special technique has been developed to reconstruct events in the emulsion which allows to perform a detailed investigation of events such as charmed hadrons production by neutrinos. As a result, the backround in the selected charm sample is up to six times lower compared to similar experiments. Such a method also permits to make direct measurements of some quantities instead of model fittings. This thesis is devoted to the study of the muonic decays of charmed hadrons and their production in emulsion. Manual inspection of charm events gives a complete reconstruction of charm decay topology. The extraction of the inclusive muonic branching ratio is based on the ratios per number of charged daughters in charm decay. Such an approach allows to separetely measure the muonic branching ratios for neutral and charged charm particles. Finally, normalization of the events with a muon in the final state to the charged current events gives dimuon production rate which is found compatible with the previous experiments. On top of that, preliminary results are shown for Bjorken x distribution and for a direct measurement of the Vcd Cabbibo-Kabayashi-Maskawa matrix element.

Metrological data from sample surfaces can be obtained by using a variety of profilometry methods. Atomic Force Microscopy (AFM), which relies on contact inter-atomic forces to extract topographical images of a sample, is one such method that can be used on a wide range of surface types, with possible nanometer range resolution. However, AFM images are commonly distorted by convolution, which reduces metrological accuracy. This type of distortion is more significant when the sample surface contains high aspect ratio features such as lines, steps or sharp edges - structures commonly found in semiconductor devices and applications. Aiming at mitigating these distortions and recovering metrology soundness, we introduce a novel image deconvolution scheme based on the principle of stereo imaging. Multiple images of a sample, taken at different angles, allow for separation of convolution artifacts from true topographic data. As a result, perfect sample reconstruction and probe shape estimation can be achieved in certain cases. Additionally, shadow zones, which are areas of the sample that cannot be probed by the AFM, are greatly reduced. Most importantly, this technique does not require a priori probe characterization. It also reduces the need for slender or sharper probes, which, on one hand, induce less convolution distortion but, on the other hand, are more prone to wear and damage, thus decreasing overall system reliability. / Singapore-MIT Alliance (SMA)

The main focus of this dissertation is to develop a multispectral imaging system with spectral zooming capability and also successfully demonstrate its promising medical applications through combining this technique with microscope system. The realization of the multispectral imaging method in this dissertation is based on the 4-f spatial filtering principle. When a collimated light is dispersed by the grating, there exists a clear linear distribution spectral line or spectrum at the Fourier plane of the Fourier transform lens group base on the Abbe imaging theory and optics Fourier Transform principle. The optical images, not the collimated light, are applied into this setup and the spectrum distribution still keeps linear relationship with the spatial positions at Fourier plane, even through there exists additional spectral crosstalk or overlap. The spatial filter or dynamic electrical filters used at the Fourier plane will facilitate randomly access the desired spectral waveband and agilely adjust the passband width. It offers the multispectral imaging functionality with spectral zooming capability. The system is flexible and efficiency. A dual-channel spectral imaging system based on the multispectral imaging method and acousto-optical tunable filter (AOTF) is proposed in the dissertation. The multispectral imaging method and the AOTF will form spate imaging channels and the two spectral channels work together to enhance the system efficiency. The AOTF retro reflection design is explored in the dissertation and experimental results demonstrate this design could effectively improve the spectral resolution of the passband. Moreover, a field lens is introduced into the multispectral imaging system to enhance the field of view of the system detection range. The application of field lens also improves the system spectral resolution, image quality and minimizes the system size. This spectral imaging system can be used for many applications. The compact prototype multispectral imaging system has been built and many outdoor remote spectral imaging tests have been performed. The spectral imaging design has also been successfully applied into microscope imaging. The prototype multispectral microscopy system shows excellent capability for normal optical detection of medical specimen and fluorescent emission imaging/diagnosis. Experiment results have demonstrated this design could realize both spectral zoom and optical zoom at the same time. This design facilitates fast spectral waveband adjustment as well as increasing speed, flexibility, and reduced cost.

Neutrino-nucleon scattering is an effective way to investigate the inner structure of the nucleon, to extract the Standard Model parameters and to explore heavy quarks production dynamics. In the last decades, several experiments have been constructed to study weak interactions of neutrinos with nucleons. One of them was CERN-WA95 experiment operated by the CHORUS collaboration. It is based on a hybrid detector with nuclear emulsion as a target followed by electronic devices. Nuclear emulsion provides three dimensional spatial information with an outstanding resolution of the order of one micron. Therefore, it is ideal to detect short-lived particles. A special technique has been developed to reconstruct events in the emulsion which allows to perform a detailed investigation of events such as charmed hadrons production by neutrinos. As a result, the backround in the selected charm sample is up to six times lower compared to similar experiments. Such a method also permits to make direct measurements of some quantities instead of model fittings. This thesis is devoted to the study of the muonic decays of charmed hadrons and their production in emulsion. Manual inspection of charm events gives a complete reconstruction of charm decay topology. The extraction of the inclusive muonic branching ratio is based on the ratios per number of charged daughters in charm decay. Such an approach allows to separetely measure the muonic branching ratios for neutral and charged charm particles. Finally, normalization of the events with a muon in the final state to the charged current events gives dimuon production rate which is found compatible with the previous experiments. On top of that, preliminary results are shown for Bjorken x distribution and for a direct measurement of the Vcd Cabbibo-Kabayashi-Maskawa matrix element.

In the past two decades depth-sensing indentation has becomea widely used technique to measure the mechanical properties ofmaterials. This technique is particularly suitable for thecharacterisation of materials at sub-micro or nano scale thoughthere is a tendency to extend its application to the micro ormacro scale. The load-penetration depth curve of depth-sensingindentation is a characteristic of a material and can be usedfor analysing various mechanical properties in addition tohardness. This thesis deals with the mechanicalcharacterisation of bulk materials, thin films and coatings,gradient materials, and composites using depth-sensingindentation. Finite element method has been resorted to as atool to understand the indentation behaviour of materials. The piling-up or sinking-in behaviour of materials plays animportant role in the accurate determination of materialsproperties using depth-sensing indentation. Finite elementsimulations show that the piling-up or sinking-in behaviour isdetermined by the material parameters, namelyE/σyratio and strain hardening exponent orexperimental parameterhe/hmaxratio, and the contact friction. Anempirical model has been proposed to relate the contact area ofindentation to theE/σyratio and thehe/hmaxratio and used to predict thepiling-up orsinking-in of materials. The existence of friction is found toenhance the sinking-in tendency of materials. A generalrelationship between the hardness and the indentationrepresentative stress valid for both soft and hard materialshas been obtained. A possible method to estimate the plasticproperties of bulk materials has been suggested. Measuring the coating-only properties requires theindentation to be done within a critical penetration depthbeyond which substrate effect comes in. The ratio of thecritical penetration depth to the coating thickness determinedby nanoindentation is independent of coating thickness andabout 0.2 for gold / nickel, 0.4 for aluminium / BK7 glass, and0.2 for diamond-like-carbon / M2 steel and alumina / nickel.Finite element simulations show that this ratio is dependent onthe combination of the coating and the substrate and moresensitive to differences in the elastic properties than in theplastic properties of the coating/substrate system. Thedeformation behaviour of coatings, such as, piling-up of thesoft coatings and cracking of the hard coatings, has also beeninvestigated using atomic force microscope. The constraint factors, 2.24 for WC phase and 2.7 for WC-Cocemented carbides, are determined through nanoindentation andfinite element simulations. A modified hardness model of WC-Cocemented carbides has been proposed, which gives a betterestimation than the Lee and Gurland hardness model. Finiteelement method has also been used to investigate theindentation behaviour of WC-Co gradient coatings. Keywords:depth-sensing indentation, nanoindentation,finite element method, atomic force microscope, mechanicalproperties, hardness, deformation, dislocations, cracks,piling-up, sinking-in, indentation size effect, thin coatings,composite, gradient materials, WC-Co, diamond-like-carbon,alumina, gold, aluminium, nickel, BK7 glass, M2 steel.

The fabrication characteristic of etching and deposition of focused ion beam (FIB) on the submicron structure of silica and quartz glass was investigated. FIB has several advantages such as high sensitivity, high material removal rate, and direct fabrication in some selected areas without the use of etching mask, etc. In this study, silicon and quartz glass materials etched by FIB were used for fast fabrication of 3-D submicron structures to investigate the differences between the samples before and after fabrication. The expansion effect of silicon with sputtered platinum on surface is compared with Pyrex glass with sputtered chromium on surface. The result shows the side wall of structure in the center wouldn¡¦t be vertical after etching and trimming on the quartz glass and the silicon substrate. Trenches with different depth and width on the surface of silicon were etched by FIB and measured by Atomic Force Microscope. Lines with different interval were deposited by FIB on the surface of quartz glass and were measured by Atomic Force Microscope.

No description available.

Laser interference fringe tomography (LIFT) is within the class of optical imaging devices designed for volumetric microscope applications. LIFT is a very simple and cost-effective three-dimensional imaging device which is able to reliably produce low-quality imagery. It measures the reflectivity as a function of depth within a sample and is capable of producing three-dimensional images from optically scattering surfaces. The first generation of this instrument is designed and prototyped for optical microscopy. With an imaging spot size of 42 μm and a 180 μm axial resolution kernel, LIFT is capable of producing one- and two- dimensional images of various samples up to 1.5 mm thickness. The prototype was built using commercial-off-the-shelf components and cost ~ $1,000. It is possible that with effort, this device can become a reliable, stable, low-quality volumetric imaging microscope to be readily available to the consumer market at a very affordable price. This document will present the optical design of LIFT along with the complete mathematical description of the instrument. The design trade-offs and choices of the instrument are discussed in detail and justified. The theoretical imaging capabilities of the instrument are tested and experimentally verified. Finally, some imaging results are presented and discussed.

<p>Nucleic acids are subjected to many different mechanical loadings inside. These loadings could cause large deformations and conformational changes to these molecules. This is why the mechanical properties of nucleic acids are so important to their functions. Here we use a newly designed and built high-performance AFM force spectrometer, supplemented with molecular dynamics simulations and NMR spectroscopy to investigate the relationship between mechanical properties and structure of different nucleic acids.</p><p>To test the mechanical properties of nucleic acids, we successfully designed and purpose-built a single molecule puller, an instrument to physically stretch single molecules, at a fraction of the cost of a commercial AFM instrument. This instrument has similar force noise to hybrid instruments, while also exhibiting significantly lower drift, on the order of five times lower. This instrument allows the measurement of subtle transitions as a molecule is stretched. With the addition of a lock-in amplifier, we possibly could obtain better force resolution, the order of femtonewtons. </p><p>We find that helical structure does indeed have an effect on the mechanical properties of double-stranded DNA. As the A-form double helix has a shorter, wider structure compared to the B-form helix, its force spectra exhibit a shorter initial length before the overstretching force plateau, compared to B-form DNA. Contrarily, the Z-form double helix has a narrower, more extended helical structure than B-form DNA, and we see this fact manifest in the force spectra of Z-DNA, which has a longer initial length before the overstretching force plateau. Also, interestingly, we find that neither A, nor Z-DNA force spectra display the second melting force plateau. Indicating this plateau is not necessarily cause by melting of strands apart, but rather a feature of B-DNA. </p><p>To better understand the forces that stabilized these different structures, specifically base stacking, we also mechanically characterize different single-stranded helical polynucleotides using AFM based force spectroscopy. We expand on previous studies by confirming that single helical polynucleotides undergo a force transition at a force of ~20 pN as they are uncoiled, and also demonstrating, that when stretched beyond this force transition, the molecules behave differently depending on base sequence and backbone sugar. Specifically, the force spectra of poly-adenylic acid possess a linear force region, which persists to ~300 pN, after the force plateau. We also observe that poly-deoxyadenylic acid is comparatively stiffer than other polynucleotides after undergoing two force transitions. By supplementing our force spectroscopic data with MD simulations and NMR spectroscopy, we find that base stacking in adenine is quite strong, persisting above 100 pN. We find that initial helical structure, which is defined by base stacking and backbone sugar, guides the stretching pathway of the polynucleotides. This finding can possibly be extrapolated to the elasticity of double-stranded DNA.</p> / Dissertation