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Structure and Dynamics of Core-Excited SpeciesTravnikova, Oksana January 2008 (has links)
<p>In this thesis we have performed core-electron spectroscopy studies of gas phase molecular systems starting with smaller diatomic, continuing with triatomic and extending our research to more complex polyatomic ones. We can subdivide the results presented here into two categories: the first one focusing on electronic fine structure and effect of the chemical bonds on molecular core-levels and the other one dealing with nuclear dynamics induced by creation of a core hole. In our research we have mostly used synchrotron radiation based techniques such as X-ray Photoelectron (XPS), X-ray Absorption (XAS), normal and Resonant Auger (AES and RAS, respectively) and Energy-Selected Auger Electron PhotoIon COincidence (ES-AEPICO) spectroscopies.</p><p>We have demonstrated that resonant Auger spectroscopy can be used to aid interpretation of the features observed in XAS for Rydberg structures in the case of Cl<sub>2</sub> and C1s<sup>−1</sup>π*<sup>1</sup> states of allene molecules. The combined use of high-resolution spectroscopy with <i>ab initio</i> calculations can help the interpretation of strongly overlapped spectral features and disentangle their complex profiles. This approach enabled us to determine the differences in the lifetimes for core-hole 2p sublevels of Cl<sub>2</sub> which are caused by the presence of the chemical bond. We have shown that contribution in terms of the Mulliken population of valence molecular orbitals is a determining factor for resonant enhancement of different final states and fragmentation patterns reached after resonant Auger decays in N<sub>2</sub>O.</p><p>We have also performed a systematic study of the dependence of the C1s resonant Auger kinetic energies on the presence of different substituents in CH<sub>3</sub>X compounds. For the first time we have studied possible isomerization reaction induced by core excitation of acetylacetone. We could observe a new spectral feature in the resonant Auger decay spectra which we interpreted as a signature of core-excitation-induced keto-enol tautomerism.</p>
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Evaluation of amorphous oxide semiconductors for thin film transistors (TFTs) and resistive random access memory (RRAM) applicationsRajachidambaram, Jaana Saranya 06 January 2013 (has links)
Thin-film transistors (TFTs) are primarily used as a switching element in liquid crystal
displays. Currently, amorphous silicon is the dominant TFT technology for displays, but
higher performance TFTs will become necessary to enable ultra-definition resolution
high-frequency large-area displays. Amorphous zinc tin oxide (ZTO) TFTs were
fabricated by RF magnetron sputter deposition. In this study, the effect of both deposition
and post annealing conditions have been evaluated in regards to film structure,
composition, surface contamination, and device performance. Both the variation of
oxygen partial pressure during deposition and the temperature of the post-deposition
annealing were found to have a significant impact on TFT properties. X-ray diffraction
data indicated that the ZTO films remain amorphous even after annealing to 600° C.
Rutherford backscattering spectrometry indicated that the Zn:Sn ratio of the films was
~1.7:1 which is slightly tin rich compared to the sputter target composition. X-ray
photoelectron spectroscopy data indicated that the films had significant surface
contamination and that the Zn:Sn ratios changed depending on sample annealing
conditions. Electrical characterization of ZTO films using TFT test structures indicated
that mobilities as high as 17 cm² V⁻¹ s⁻¹ could be obtained for depletion mode devices. It
was determined that the electrical properties of ZTO films can be precisely controlled by
varying the deposition conditions and annealing temperature. It was found that the ZTO
electrical properties could be controlled where insulating, semiconducting and conducting
films could be prepared. This precise control of electrical properties allowed us to
incorporate sputter deposited ZTO films into resistive random access memory (RRAM)
devices. RRAM are two terminal nonvolatile data memory devices that are very
promising for the replacement of silicon-based Flash. These devices exhibited resistive
switching between high-resistance states to low-resistance states and low-resistance states
to high-resistance states depending on polarity of applied voltages and current
compliance settings. The device switching was fundamentally related to the defect states
and material properties of metal and insulator layers, and their interfaces in the metalinsulator-metal (MIM) structure. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Jan. 6, 2012 - Jan. 6, 2013
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Oberflächenplasmonenresonanz-basierte DNA-Chips und Nucleobasen-SequenzentwurfKick, Alfred 30 October 2013 (has links) (PDF)
Die vorliegende Dissertation beschreibt die Erarbeitung anwendbarer Methoden zum Aufbau Oberflächenplasmonenresonanz (SPR)-basierter DNA-Mikroarrays. Es werden die Beziehungen zwischen allen Teilschritten der Entwicklung eines DNA-Biosensors aufgezeigt. Die Sondendichte auf der Sensoroberfläche ist entscheidend für die Leistungsfähigkeit eines DNA-Chips. In dieser Arbeit werden thiolmodifizierte Sonden und solche mit Phosphorothioatgruppen verwendet und verglichen.
Der Aufbau selbstorganisierender Monoschichten, bestehend aus Mercaptoalkoholen und thiolmodifizierten DNA-Einzelsträngen, wird mittels Röntgenphotoelektronenspektroskopie untersucht. Es werden bis zu 180 Spots auf einem SPR-Chip aufgetragen. Eine weitere Erhöhung der Anzahl an Sondenorten pro Chip wird mit einer hydrophil/hydrophoben Strukturierung der Arrayoberfläche erreicht. Dies erfolgt durch das Mikrokontaktdrucken mit Alkanthiolen.
Die selektiven Hybridisierungen der Produkte der Polymerase-Kettenreaktion (PCR) werden bei SPR-Messungen auf DNA-Mikroarrays detektiert. Eine schnelle markierungsfreie Echtzeitanalyse wird bei Hybridisierungen im mikrofluidischen Kanal innerhalb weniger Minuten erzielt. Die Anwendbarkeit dieser Methoden wurde anhand der Mutationsanalyse der Fusionsgene AML1-ETO und CBFB-MYH11 bei der akuten myeloischen Leukämie bestätigt.
Die Hybridisierungseffizienz auf DNA-Mikroarrays hängt stark von der Sodensequenz ab. SPR-Experimente zeigen, dass die Ausbildung der Haarnadelstrukturen die Ursache dafür ist. Ein Computerprogramm (EGNAS) auf Grundlage eines neu entwickelten Nucleobasen-Sequenzentwurf-Algorithmus, ermöglicht die Generierung vollständiger Sequenzsätze. Die Intra- und Interstrangeigenschaften dieser Sequenzen können kontrolliert werden, um Haarnadelstrukturen und Kreuzhybridisierungen zu vermeiden. Dadurch können optimierte Sequenzen für Anwendungen auf DNA-Chips oder in der DNA-Nanobiotechnologie entworfen werden.
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Structural and electronic properties of metal oxidesRegoutz, Anna January 2014 (has links)
Metal oxides are of immense technological importance. Their wide variety of structural and electronic characteristics leads to a flexibility unrivalled by other groups of materials. However, there is still much debate about the fundamental properties of some of the most widely used oxides, including TiO<sub>2</sub> and In<sub>2</sub>O<sub>3</sub>. This work presents high quality, in-depth characterisation of these two oxides in pure and doped form, including soft and hard X-ray photoelectron spectroscopy and X-ray diffraction. Bulk samples as well as thin film samples were prepared analysed. For the preparation of thin films a high quality sol-gel dip-coating method was developed, which resulted in epitaxial films. In more detail the organisation of the thesis is as follows: Chapter 1 provides an introduction to key ideas related to metal oxides and presents the metal oxides investigated in this thesis, In<sub>2</sub>O<sub>3</sub>, Ga<sub>2</sub>O<sub>3</sub>, Tl<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub>, and SnO<sub>2</sub>. Chapter 2 presents background information and Chapter 3 gives the practical details of the experimental techniques employed. Chapters 4 presents reciprocal space maps of MBE-grown In<sub>2</sub>O<sub>3</sub> thin films and nanorods on YSZ substrates. Chapters 5 and 6 investigate the doping of In<sub>2</sub>O<sub>3</sub> bulk samples with gallium and thallium and introduce a range of solid state characterisation techniques. Chapter 7 describes the development of a dip-coating sol-gel method for the growth of thin films of TiO<sub>2</sub> and shows 3D reciprocal space maps of the resulting films. Chapter 8 concerns hard x-ray photoelectron spectroscopy of undoped and Sn-doped TiO<sub>2</sub>. Chapter 9 interconnects previous chapters by presenting 2D reciprocal space maps of nano structured epitaxial samples of In<sub>2</sub>O<sub>3</sub> grown by the newly developed sol-gel based method. Chapter 10 concludes this thesis with a summary of the results.
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Surface characterization and functional properties of carbon-based materialsNelson, Geoffrey Winston January 2012 (has links)
Carbon-based materials are poised to be an important class of 21st century materials, for bio-medical, bio-electronic, and bio-sensing applications. Diamond and polymers are two examples of carbon-based materials of high interest to the bio-materials community. Diamond, in its conductive form, can be used as an electrochemical bio-sensor, whilst its nanoparticle form is considered a non-inflammatory platform to deliver drugs or to grow neuronal cells. Polymers, especially when chemically modified, have been used extensively in biological environments, from anti-microbial use to drug delivery. The large-scale use of either material for biological use is limited by two factors: ease of chemical modification and the paucity of knowledge of their surface chemistry in aqueous media. This thesis addresses aspects of both these issues. The first study reported is an in situ study of the adsorption dynamics of an exemplar globular protein (bovine serum albumin, BSA) on nanodiamond using the relatively novel quartz crystal microbalance with dissipation (QCM-D) technique. For the first time, QCM-D enabled the detailed study of protein dynamics (i.e. kinetics, viscoelastic properties, overlayer structure, etc.) onto nanodiamond thin films having various surface chemistry and roughness. The dynamics of protein adsorption is found to be sensitive to surface chemistry at all stages of adsorption, but it is only sensitive to surface roughness during initial adsorption phases. Our understanding of the nanodiamond-biology interface is enhanced by this study, and it suggests that QCM-D is useful for the study of the surface chemistry of nanoparticle forms of inorganic materials. A second study concerns a novel surface functionalization scheme, based on carbene and azo-coupling chemistry, which has been recently introduced as a practical, facile method for modifying the surfaces of polymers. Using modern surface characterization techniques, it is demonstrated that a chemical linker can be attached to polystyrene surfaces using carbene-based chemistry, and that further chemical functionality can be added to this chemical linker via an azo-coupling reaction. In situ studies of protein dynamics at these interfaces were conducted using QCM-D, thus enabling a link between specific protein behaviour and the polymer surface chemical termination chemistry to be made. A third area of study of investigates the use of diamond electrodes as a bio-sensor for dopamine under physiological conditions. For these conditions, ascorbic acid interferes with the dopamine oxidation signal, in ways that render the two signals irresolvable. Various modifications are used in attempts to reduce this interference, including: small and large cathodic treatments, grafting of electro-active polymers, addition of carbon nanotubes, and hydrogen plasma treatment. Those modifications leading to the hydrogen-termination of diamond are shown to work the best. Notably, hydrogen plasma treatment effects the complete electrochemical separation of dopamine and ascorbic acid at a diamond electrode. This is the first time this has been accomplished without adding non-diamond materials to the diamond electrode surface.
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Characterization of deeply buried interfaces by Hard X-ray Photoelectron Spectroscopy / Caractérisation d’interfaces profondément enterrées par spectroscopie de photoélectrons à haute énergie (HAXPES)Zborowski, Charlotte 27 June 2018 (has links)
Cette thèse vise à améliorer la méthode d'analyse du fond continu inélastique afin de l'appliquer à des cas qui présentent un intérêt technologique. En effet, ces améliorations sont cruciales car elles portent sur des critères de précision et de gain de temps, plus particulièrement pour l’étude de dispositifs présentant plusieurs couches profondément enterrées de matériaux bien distincts. Ainsi, l'analyse du fond continu inélastique associée à la spectroscopie de photoélectrons à rayons X durs (HAXPES) présente un grand intérêt car l’HAXPES permet de sonder plus profondément dans un échantillon qu'avec la spectroscopie de photoélectrons à rayons X classique (XPS). Ce présent travail porte sur des échantillons technologiquement pertinents, principalement des transistors à haute mobilité d'électrons (HEMTs), à certaines étapes cruciales de leur processus de fabrication, tels que des recuits. Il est donc très important que ces analyses soient effectuées de manière non destructive afin de préserver les interfaces enterrées. Ce sont souvent l'emplacement de phénomènes complexes qui sont critiques pour les performances du dispositif et une meilleure compréhension est une condition préalable à l’amélioration des dispositifs. Dans ce travail, les phénomènes de diffusion en profondeur sont étudiés grâce à l’analyse du fond continu inélastique associée à l’HAXPES (en utilisant le logiciel QUASES) pour des profondeurs allant jusqu'à 60 nm. Les résultats de distribution en profondeur présentent des écarts par rapport aux mesures TEM inférieures à 5%. Le choix des paramètres d'entrée de la méthode est discuté pour une large gamme d'échantillons et des règles simples en sont issues qui rendent l'analyse réelle plus facile et plus rapide à effectuer. Enfin, il a été montré que la spectromicroscopie faite avec la technique HAXPEEM peut fournir des spectres à chaque pixel utilisables pour l’analyse du fond continu inélastique. Cela peut fournir une cartographie 3D de la distribution en profondeur des éléments de manière non-destructive. / This thesis aims at improving the inelastic background analysis method in order to apply it to technologically relevant samples. Actually, these improvements are utterly needed as they concern criteria of accuracy and time saving particularly for analysis of devices presenting deeply buried layers with different materials. For this purpose, the interest of the inelastic background analysis method is at its best when combined with hard X-ray photoelectron spectroscopy (HAXPES) because HAXPES allows to probe deeper in the sample than with conventional X-ray photoelectron spectroscopy (XPS). The present work deals with technologically relevant samples, mainly the high-electron mobility transistor (HEMT), at some crucial steps of their fabrication process as annealing. Actually, it is very important that these analyses shall be performed non-destructively in order to preserve the buried interfaces. These are often the location of complex phenomena that are critical for device performances and a better understanding is often a prerequisite for any improvement. In this thesis, the in-depth diffusion phenomena are studied with the inelastic background analysis technique (using the QUASES software) combined with HAXPES for depth up to 60 nm. The depth distribution results are determined with deviations from TEM measurements smaller than a typical value of 5%. The choice of the input parameters of the method is discussed over a large range of samples and simple rules are derived which make the actual analysis easier and faster to perform. Finally, it was shown that spectromicroscopy obtained with the HAXPEEM technique can provide spectra at each pixel usable for inelastic background analysis. This is a proof of principle that it can provide a 3D mapping of the elemental depth distribution with a nondestructive method. / Denne afhandling har til formål at forbedre den uelastiske baggrundsanalysemetode til anvendelser i den til teknologiske industri. Faktisk er disse forbedringer absolut nødvendige, for at opnå nøjagtighed og tidsbesparelse, især for analyse af prøver med dybt begravede lag af forskellige materialer. Til det formål er interessen for den uelastiske baggrundsanalysemetode bedst i kombination med hård røntgenfotoelektron-spektroskopi (HAXPES), fordi HAXPES gør det muligt at probe dybere i prøven end med konventionel røntgenfotoelektron-spektroskopi (XPS). Dette arbejde beskæftiger sig med teknologisk relevante prøver, hovedsagelig høj-elektron mobilitetstransistor (HEMT), på nogle afgørende trin i deres fremstillingsproces som fx annealing. Faktisk er det meget vigtigt, at disse analyser udføres på en ikke-destruktiv måde for at bevare de begravede grænseflader. Det er ofte her de komplekse fysiske fænomener opstår, som er kritiske for fuktionaliteten, og en bedre forståelse af grænsefladerne er ofte en forudsætning for at kunne forbedre denne. I denne afhandling studeres de dybdegående diffusionsfænomener med den uelastiske baggrundsanalyse teknik (ved hjælp af QUASES software) kombineret med HAXPES for dybder op til 60 nm. Dybdestributionsresultaterne har afvigelser fra TEM-målinger mindre end en typisk værdi på 5%. Valget af input parametre for metoden er diskuteret på bagground af et stort udvalg af prøver samt omfattende simuleringer og enkle regler er udledt, hvilket gør den praktiske analyse nemmere og hurtigere at udføre. Endelig blev det vist, at spektromikroskopi opnået med HAXPEEM-teknikken kan tilvejebringe spektre ved hver enkelt pixel som kan anvendes til uelastisk baggrundsanalyse. Dette viser at i princippet kan en 3D-billeddannelse af den elementære dybdefordeling bestemmes ikke destruktivt.
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L'influence de l'irradiation sur les propriétés structurelles et de transport du graphène / The influence of irradiation on structural and transport properties of grapheneDeng, Chenxing 26 May 2015 (has links)
Le graphène est une simple couche de nid d'abeille motifs atomes de carbone. Il a suscité beaucoup d'intérêt dans la dernière décennie en raison de ses excellentes propriétés électroniques, optiques et mécaniques, etc., et montre larges perspectives d'applications dans le futur. Parfois, les propriétés du graphène doivent être modulées pour s’adapter à des applications spécifiques. Par exemple, le contrôle du niveau de dopage fournit un bon moyen de moduler les propriétés électriques et magnétiques de graphène, qui est important pour la conception de dispositifs de mémoire et de logique à base de graphène. En outre, la possibilité de régler la conductance électrique peut être utilisée pour fabriquer le transistor de graphène, et le dépôt chimique en phase vapeur (CVD) Procédé montre la possibilité d'effectuer la préparation de graphène intégrées dans les processus de fabrication de semi-conducteur. L'injection de spin et l'irradiation sont méthodes efficaces et pratiques pour adapter les propriétés de transport du graphène. Mais en raison du processus de fabrication complexe, il est difficile de préparer le dispositif de transport de spin graphène succès. La lithographie et décoller les processus qui impliquent utilisant résine photosensible va dégénérer les propriétés de transport du graphène. En outre, la sensibilité du graphène aux molécules H2O et O2 lorsqu'il est exposé à l’air ambiant entraînera faible signal de rotation et le bruit de fond. L'irradiation fournit une méthode propre à moduler les propriétés électriques de graphène qui n’impliquent pas de traitement chimique. En ions ou irradiation d'électrons, la structure de bande électronique de graphène peut être réglé et la structure en treillis est modulé aussi bien. En outre, les impuretés chargées et dopage résultant de l'irradiation peuvent modifier les propriétés électroniques du graphène comme la diffusion électron-phonon, libre parcours moyen et la densité de support. Comme indiqué, le graphène oxydation peut être induite par exposition à un plasma d'oxygène, et le N- dopage de graphène par recuit thermique dans de l'ammoniac a été démontré. En outre, la souche dans le graphène peut également être adaptée par irradiation, qui contribue également à la modification des propriétés de transport de graphène. En conclusion, l'irradiation fournit une méthode physique efficace pour moduler les propriétés structurelles et de transport de graphène, qui peuvent être appliqués dans la mémoire à base de graphène et des dispositifs logiques, transistor, et des circuits intégrés. Dans cette thèse, l'irradiation d'ions hélium a été réalisée sur le graphène cultivé sur substrat SiO2 par la méthode CVD, et les propriétés structurelles et de transport ont été étudiés. Le dopage de transfert de charge dans le graphène induite par les résultats d'irradiation dans une modification de ces propriétés, qui suggère une méthode pratique pour les adapter. En outre, l'irradiation par faisceau d'électrons a été effectuée sur graphène cultivé sur substrat de SiC. Les amorphisations progressives, contraintes et d'électrons dopage locales contribuent à la modification des propriétés structurelles et de transport dans le graphène qui peuvent être observés. / Graphene is a single layer of honeycomb patterned carbon atoms. It has attracted much of interest in the past decade due to its excellent electronic, optical, and mechanical properties, etc., and shows broad application prospects in the future. Sometimes the properties of graphene need to be modulated to adapt for specific applications. For example, control of doping level provides a good way to modulate the electrical and magnetic properties of graphene, which is important to the design of graphene-based memory and logic devices. Also, the ability to tune the electrical conductance can be used to fabricate graphene transistor, and the chemical vapor deposition (CVD) method shows the possibility to make the preparation of graphene integrated into semiconductor manufacture processes. Moreover, the sensitivity of graphene to the H2O and O2 molecules when exposed to the air ambient will result in weak spin signal and noise background. Irradiation provides a clean method to modulate the electrical properties of graphene which does not involve chemical treatment. By ion or electron irradiation, the electronic band structure of graphene can be tuned and the lattice structure will be modulated as well. Moreover, the charged impurities and doping arising from irradiation can change the electronic properties of graphene such as electron-phonon scattering, mean free path and carrier density. As reported, graphene oxidization can be induced by exposure to oxygen plasma, and N-Doping of Graphene through thermal annealing in ammonia has been demonstrated. Furthermore, the strain in graphene can also be tailored by irradiation, which also contributes to the modification of transport properties of graphene. In conclusion, irradiation provides an efficient physical method to modulate the structural and transport properties of graphene, which can be applied in the graphene-based memory and logic devices, transistor, and integrated circuits (ICs). In this thesis, Helium ion irradiation was performed on graphene grown on SiO2 substrate by CVD method, and the structural and transport properties were investigated. The charge transfer doping in graphene induced by irradiation results in a modification of these properties, which suggests a convenient method to tailor them. Moreover, electron beam irradiation was performed on graphene grown on SiC substrate. The local progressive amorphization, strain and electron doping contribute to the modification of structural and transport properties in graphene which can be observed.
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Photoelectron Spectroscopy on Atoms, Molecules and Clusters : The Geometric and Electronic Structure Studied by Synchrotron Radiation and LasersRander, Torbjörn January 2007 (has links)
<p>Atoms, molecules and clusters all constitute building blocks of macroscopic matter. Therefore, understanding the electronic and geometrical properties of such systems is the key to understanding the properties of solid state objects.</p><p>In this thesis, some atomic, molecular and cluster systems (clusters of O<sub>2</sub>, CH<sub>3</sub>Br, Ar/O<sub>2</sub>, Ar/Xe and Ar/Kr; dimers of Na; Na and K atoms) have been investigated using synchrotron radiation, and in the two last instances, laser light. We have performed x-ray photoelectron spectroscopy (XPS) on all of these systems. We have also applied ultraviolet photoelectron spectroscopy (UPS), resonant Auger spectroscopy (RAS) and near-edge x-ray absorption spectroscopy (NEXAFS) to study many of the systems. Calculations using <i>ab initio</i> methods, namely density functional theory (DFT) and Møller-Plesset perturbation theory (MP), were employed for electronic structure calculations. The geometrical structure was studied using a combination of <i>ab initio</i> and molecular dynamics (MD) methods.</p><p>Results on the dissociation behavior of CH<sub>3</sub>Br and O<sub>2</sub> molecules in clusters are presented. The dissociation of the Na<sub>2</sub> molecule has been characterized and the molecular field splitting of the Na 2<i>p</i> level in the dimer has been measured. The molecular field splitting of the CH<sub>3</sub>Br 3<i>d</i> level has been measured and the structure of CH<sub>3</sub>Br clusters has been determined to be similar to the structure of the bulk solid. The diffusion behavior of O<sub>2</sub>, Kr and Xe on large Ar clusters, as a function of doping rate, has been investigated. The shake-down process has been observed from excited states of Na and K. Laser excited Na atoms have been shown to be magnetically aligned. The shake-down process was used to characterize the origin of various final states that can be observed in the spectrum of ground-state K.</p>
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A Treatise on the Geometric and Electronic Structure of Clusters : Investigated by Synchrotron Radiation Based Electron SpectroscopiesLindblad, Andreas January 2008 (has links)
<p>Clusters are finite ensembles of atoms or molecules with sizes in the nanometer regime (<i>i.e.</i> nanoparticles). This thesis present results on the geometric and electronic structure of homogeneous and heterogeneous combinations of atoms and molecules. The systems have been studied with synchrotron radiation and valence, core and Auger electron spectroscopic techniques.</p><p>The first theme of the thesis is that of mixed clusters. It is shown that by varying the cluster production technique both structures that are close to that predicted by equilibrium considerations can be attained as well as far from equilibrium structures.</p><p>Electronic processes following ionization constitute the second theme. The post-collision interaction phenomenon, energy exchange between the photo- and the Auger electrons, is shown to be different in clusters of argon, krypton and xenon. A model is proposed that takes polarization screening in the final state into account. This result is of general character and should be applicable to the analysis of core level photoelectron and Auger electron spectra of insulating and semi-conducting bulk materials as well.</p><p>Interatomic Coloumbic Decay is a process that can occur in the condensed phases of weakly bonded systems. Results on the time-scale of the process in Ne clusters and mixed Ar/Ne clusters are herein discussed, as well observations of resonant contributions to the process. In analogy to Auger <i>vis-à-vis</i> Resonant Auger it is found that to the ICD process there is a corresponding Resonant ICD process possible. This has later been observed in other systems and by theoretical calculations as well in subsequent works by other groups.</p><p>Delocalization of dicationic valence final states in the hydrogen bonded ammonia clusters and aqueous ammonia has also been investigated by Auger electron spectroscopy. With those results it was possible to assign a previously observed feature in the Auger electron spectrum of solid ammonia.</p>
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Préparation et caractérisation de films ordonnés, fonctionnels et commutables de macrocycles et de rotaxanes de type amide benzyliqueCecchet, Francesca 03 October 2003 (has links)
Abstract :
The objectives of this work were to prepare and characterize films of benzylic amide macrocycles and rotaxanes obtained by functionalisation of an acidterminated self-assembled monolayer (SAM) on gold, and thus to probe the aptitude of these surfaces for applications in the field of the nanotechnologies.
We initially studied the self-assembled monolayer of 11-mercaptoundecanoic acid and focused on its composition, structure and organization. We show that the molecules of alcanethiol are oriented with the acid group pointing out from the surface. The film is highly ordered with defect density below 0.2%.
We investigated the functionalisation process with the covalently bound Mac-OH macrocycle, with the physisorbed Mac-pyridine macrocycle and with the naphtalimide rotaxane. The latter is also anchored to the SAM through a non-covalent interaction. We focused on the comprehension of both quantitative as qualitative characteristics of the films, such as the degree of functionalisation, their stability with respect to external constraints, their order and homogeneity, their structure and their orientation. By combining techniques such as X-ray photoemission spectroscopy, infrared reflection-absorption spectroscopy, atomic force microscopy, electrochemical and contact angle measurements, we demonstrated that the films of macrocycles reach a high degree of functionalisation. The layers are homogeneous and a preferential orientation of the macrocycle molecules with the plan of the ring tilted with respect to the surface and with the alkyl chains pointing-out from the films is observed. In addition, we studied the possibility of using the macrocycle films for molecular recognition, employing the Fc-Gly-Gly molecule as a model target. Through similar experiments and analysis, films of naphtalimide rotaxane were proven to give a good functionalisation of SAM. The molecule adsorbs with a preferential orientation of the linear axis parallel to the surface and the macrocycle unit normal to it. We characterized the fluorescent properties of the molecule due to the naphtalimide group and showed that when adsorbed on a gold substrate the presence of the self-assembled monolayer prevents total quenching.
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Résumé :
Les objectifs de ce travail étaient de caractériser des films de macrocycles et de rotaxanes de type amide benzylique obtenus par la fonctionnalisation de monocouches auto-assemblées d'alcanethiols, ayant un groupe acide terminal, sur une surface d'or, et ainsi de mettre en évidence certaines des potentialités de ces surfaces en vue d'applications éventuelles dans le domaine des nanotechnologies.
Nous avons d'abord étudié la monocouche auto-assemblée de l'acide 11-mercaptoundecanoïque et particulièrement les aspects tels que la composition, la structure et l'organisation du film et nous avons mis en évidence que les molécules d'alcanethiol sont orientées dans le film avec le groupe acide vers l'extérieur de la surface, de façon à pouvoir interagir avec les molécules à greffer, et que le degré d'ordre de la monocouche est très élevé, en montrant celle-ci une fraction de défauts inférieure au 0.2% de l'aire totale du film.
L'étude de la fonctionnalisation successive avec le macrocycle Mac-OH, lié de façon covalente, et le macrocycle Mac-pyridine ainsi que la rotaxane naphtalimide, ancrés à travers une interaction non-covalente à la monocouche auto-assemblée, a porté une attention particulière à la compréhension d'aspects tels que le degré de recouvrement de la surface, la stabilité vis-à-vis de contraintes externes, l'ordre et l'homogénéité, ainsi que la structure des films et l'orientation des molécules. Grâce à la combinaison de techniques telles que l'XPS, l'IRAS, les techniques électrochimiques, les mesures d'angle de contact et l'AFM, nous avons mis en évidence que les films de macrocycle atteignent un recouvrement élevé et homogène de la monocouche autoassemblée et qu'une orientation des molécules de macrocycle, avec une inclinaison du plan de l'anneau par rapport à la surface et pointant leurs chaînes alkyles vers l'extérieure du film, est observée. Ensuite, nous avons abordé la possibilité d'impliquer les films de macrocycle en tant que récepteurs moléculaires d'une molécule modèle, la Fc-Gly-Gly. Par une caractérisation similaire, les films de la rotaxane naphtalimide ont montré d'atteindre un recouvrement élevé de la surface de la monocouche avec une orientation privilégiée des molécules avec l'axe parallèle et le macrocycle perpendiculaire à la surface pour pouvoir interagir, à travers les fonctions pyridine du macrocycle, avec la monocouche. De plus, nous avons caractérisé les propriétés fluorescentes de la molécule, résidantes dans son groupe naphtalimide, lorsqu'elle est adsorbée sur un substrat métallique, l'or, affectées par la présence de la monocouche auto-assemblée.
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