Dissertations / Theses: 'XPS'

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El, Kazzi Mario. "ETUDE PAR PHOTOEMISSION (XPS & XPD) D'HETEROSTRUCTURES D'OXYDES FONCTIONNELS EPITAXIES SUR SILICIUM." Phd thesis, Ecole Centrale de Lyon, 2007. http://tel.archives-ouvertes.fr/tel-00321458.

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Cette thèse se situe dans un des axes principaux de l'INL qui a pour objectif de développer des procédés de fabrication de films minces d'oxydes monocristallins, épitaxiés sur silicium. Ces oxydes pourraient remplacer les oxydes de grille amorphes de type SiOxNy ou HfSixOyNz et répondre au cahier des charges de la « Road Map » de l'ITRS dans les futures filières CMOS sub 22nm. L'intérêt de maîtriser l'épitaxie d'oxydes sur silicium va bien au-delà de l'application au CMOS. Un tel savoir faire serait une brique technologique essentielle pour pouvoir développer des filières d'intégration monolithique sur silicium.

Dans ce contexte, l'objectif principal de ma thèse a été de mener une étude approfondie des propriétés physicochimiques et structurales de couches fines d'oxydes élaborées par Epitaxie par Jets Moléculaires (EJM) sur substrat silicium ou oxyde, en utilisant la spectroscopie de photoélectrons (XPS) et la diffraction de photoélectrons (XPD).

Nous avons étudié dans un premier temps la relaxation de films minces de LaAlO3 et de BaTiO3 épitaxiés sur des substrats de SrTiO3(001). Nous avons montré qu'au-dessous d'une certaine épaisseur critique ces deux oxydes sont contraints de façon pseudomorphiques sur SrTiO3(001). De plus nous avons clairement mis en évidence une forte augmentation de la déformation ferroélectrique pour une couche contrainte de BaTiO3.

Dans un deuxième temps, nous avons aussi étudié la croissance de LaAlO3 sur Si(001). LaAlO3 est amorphe pour des températures de croissance en dessous de 500°C. Pour des températures supérieures il y a formation de silicates à l'interface qui empêche la cristallisation. Pour surmonter cette difficulté, des procédés d'ingénierie d'interface ont été développés pour limiter les réactions interfaciales et réussir la croissance épitaxiale. Ils sont basés sur l'utilisation de couches tampons interfaciales d'oxydes comme SrO, SrTiO3 et Al2O3.

Enfin, nous avons comparé les modes de croissance et la stabilité d'interface d'Al2O3 et de Gd2O3 épitaxiés sur Si(111) et Si(001). Les résultats prouvent que la croissance de ces deux oxydes sur Si(111) a une orientation suivant [111]. Par contre sur Si(001) le mécanisme de croissance est plus complexe avec des relations d'épitaxie et des orientations inhabituelles.

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Kazzi, Mario El. "Etude par photoemission (XPS & XPD) d'hétérostructures d'oxydes fonctionnels epitaxies sur silicium." Ecully, Ecole centrale de Lyon, 2007. http://www.theses.fr/2007ECDL0028.

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Cette thèse se situe dans un des axes principaux de l’INL qui a pour objectif de développer des procédés de fabrication de films minces d’oxydes monocristallins, épitaxiés sur silicium. Ces oxydes pourraient remplacer les oxydes de grille amorphes de type SiOxNy ou HfSixOyNz et répondre au cahier des charges de la « Road Map » de l’ITRS dans les futures filières CMOS sub 22nm. L’intérêt de maîtriser l’épitaxie d’oxydes sur silicium va bien au-delà de l’application au CMOS. Un tel savoir faire serait une brique technologique essentielle pour pouvoir développer des filières d’intégration monolithique sur silicium. Dans ce contexte, l’objectif principal de ma thèse a été de mener une étude approfondie des propriétés physicochimiques et structurales de couches fines d’oxydes élaborées par Epitaxie par Jets Moléculaires (EJM) sur substrat silicium ou oxyde, en utilisant la spectroscopie de hotoélectrons (XPS) et la diffraction de photoélectrons (XPD). Nous avons étudié dans un premier temps la relaxation de films minces de LaAlO3 et de BaTiO3 épitaxiés sur des substrats de SrTiO3(001). Nous avons montré qu'au-dessous d’une certaine épaisseur critique ces deux oxydes sont contraints de façon pseudomorphiques sur SrTiO3(001). De plus nous avons clairement mis en évidence une forte augmentation de la déformation ferroélectrique pour une couche contrainte de BaTiO3. Dans un deuxième temps, nous avons aussi étudié la croissance de LaAlO3 sur Si(001). LaAlO3 est amorphe pour des températures de croissance en dessous de 500°C. Pour des températures supérieures il y a formation de silicates à l'interface qui empêche la cristallisation. Pour surmonter cette difficulté, des procédés d’ingénierie d’interface ont été développés pour limiter les réactions interfaciales et réussir la croissance épitaxiale. Ils sont basés sur l’utilisation de couches tampons interfaciales d’oxydes comme SrO, SrTiO3 et Al2O3. Enfin, nous avons comparé les modes de croissance et la stabilité d’interface d’Al2O3 et de Gd2O3 épitaxiés sur Si(111) et Si(001). Les résultats prouvent que la croissance de ces deux oxydes sur Si(111) a une orientation suivant [111]. Par contre sur Si(001) le mécanisme de croissance est plus complexe avec des relations d’épitaxie et des orientations inhabituelles
This thesis is on one of the main INL axes, the goal of which is to develop the growth procedures of thin oxide single crystal on silicon. These oxides are meant to replace the presently used amorphous gate oxide (SiOxNy and HfSixOyNz) by a high-κ oxide in future “sub 22nm” CMOS. Besides, the interest in controlling the growth of these oxides goes far beyond this oxide gate application. This know-how would be a technological breakthrough to develop monolithic integration on silicon. In this context, the main objective of my thesis has been to study the physico-chemical and structural properties of thin oxide layers grown by Molecular Beam Epitaxy (MBE) on silicon or oxide substrate. We have used X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD). First, the stress relaxation of LaAlO3 and BaTiO3 grown on SrTiO3 (001) substrate has been investigated. We have proved that below a critical thickness this two oxides can be grown pseudomorphically and that beyond a plastic relaxation occurs. In addition, we have evidenced that the ferroelectric deformation is strongly enhanced in strained BaTiO3 thin films. Second, we have studied the LaAlO3 growth on Si(001). LaAlO3 is amorphous for growth temperature below 500°C. For higher temperature, the formation of silicates at the interface prevents the crystallization. Thus, an interface engineering strategy has been set up to avoid these interfacial reactions and to succeed an epitaxial growth,. Using SrO, SrTiO3 and Al2O3 as buffer Finally, a comparison of the growth mode and interface stability has been done between Al2O3 and Gd2O3 grown either on Si(111) or Si(001) substrates. Results show that this two oxides grow along the [111] direction on Si(111). However, on Si(001), the growth mechanism is more complex leading to unusual orientations and epitaxial relationships

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Kazzi, Mario Hollinger Guy. "Etude par photoemission (XPS & XPD) d'hétérostructures d'oxydes fonctionnels epitaxies sur silicium." Ecully : Ecole Centrale de Lyon, 2007. http://bibli.ec-lyon.fr/exl-doc/melkazzi.pdf.

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Martins, Emanuel. "X-ray spectroscopic study of the electronic structure of sulfur compounds." Thesis, Queen Mary, University of London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283717.

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FLAMENT, OLIVIER. "Etude xps des interfaces polyimide/isolant." Paris 7, 1990. http://www.theses.fr/1990PA077034.

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L'etude des interfaces, pour la comprehension des phenomenes d'adherence, entre le polyimide pmda-oda (pyromellitic dianhydride-oxydianiline) et des substrats isolants (al#2o#3 et si#3n#4) est abordee a partir de la technique xps (x-ray photoelectron spectroscopy). Une calibration du spectrometre pour l'obtention de resultats quantitatifs est prealablement effectuee, la methode permettant l'obtention de mesures quantitatives reproductibles qui tiennent compte des conditions operatoires. L'utilisation de depots de polyimide en films minces (<5 nm) a permis de mettre en evidence des differences entre des temps de recuit de 1 h et 5 h a 240#oc au niveau de l'interface polymere-substrat. En effet, parallelement a l'imidisation du polyimide, des variations importantes sont constatees dans le niveau c#1#s (diminution du pic du aux imides, apparition d'un pic supplementaire) et le niveau n#1#s (augmentation de la quantite de liaisons c=n par rapport au polyimide de reference). Ces variations sont attribuees a la formation de liaisons substrat-polymere de type al-o-c pour les substrats d'alumine. Pour les substrats de nitrure, ces changements sont significatifs pour les substrats non traites et traites par plasma o#2, alors que pour ceux ayant subi un traitement d'adherence avec la -aps (-aminopropyltriethoxysilane) aucune difference n'est revelee entre les deux types de recuit. Des tests de pelage ont ete effectues pour les differents cas. Ils mettent en evidence que le recuit prolonge du polyimide (5 h) ameliore l'adherence sur les nitrures non traites ou oxydes par plasma; ceci correlant bien avec la caracterisation par esca de liaisons substrat-polymere

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Dwyer, V. M. "Elastic scattering in quantitative Auger/XPS analysis." Thesis, University of York, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374164.

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Ferrah, Djawhar. "Etude des propriétés physico-chimiques d'interfaces par photoémission." Thesis, Ecully, Ecole centrale de Lyon, 2013. http://www.theses.fr/2013ECDL0048/document.

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L'objectif de cette thèse est d'étudier les propriétés physico-chimiques des surfaces et des interfaces des couches minces par spectroscopie de photoémission (XPS), diffraction des photoélectrons (XPD), et la photoémission résolue en temps (PTR). Les expériences sont réalisées en utilisant une source standard des rayons X AlKa à l'INL ou les rayons X mous auprès du synchrotron Soleil. La première étude sur le système Pt/ Gd203/ Si(111) a montré que le transfert de charge entre le Pt et 0 à l'interface Pt/Gd203 implique un déplacement chimique de niveau Pt4f sans modification des caractéristiques de la composante métallique des spectres XPS. L'étude XPD montre que Pt se cristallise partiellement en deux domaines : [110] Pt(111) // [110] Gd203 (111) et [101] Pt(111) / / [110] Gd203 (111). De plus, une autre phase ordonnée d'oxyde de platine Pt02 à l'interface a été observée. A travers la caractérisation de la morphologie déterminée par la technique AFM et XPD, nous avons discuté l'adhésion aux interfaces métal/oxyde. La deuxième étude traite l'évolution d'interface d'un système modèle : métal non réactive/ semi-conducteur, dépendent fortement des conditions thermodynamiques. Nous avons étudié la couche mince d'Au déposée sur le substrat Si(001) par photoémission résolue en temps (TEMPO- synchrotron Soleil). L'étude XPS, montre avant le recuit la formation de l'oxyde native Si02 sur l'heterostructure à température ambiante. La désorption de cet oxyde se produit à faible température et induit une décroissance de l'intensité des photoélectrons durant le temps de recuit. La désorption de l'oxyde Si02 et la formation de l'alliage AuSi sont responsables de la gravure et la formation des puits de forme cubique à la surface de Si due à l'activité catalytique de l'Au. La troisième étude concerne la croissance du graphène à partir de cristal de SiC(0001)- face Si par décomposition thermique. Le niveau de coeur C1s résolu en trois composantes principales sont associées au carbone de 6H-SiC, de graphène, et l'interface graphène/ 6H-SiC (0001). L'intensité de chaque composante est rapportée en fonction de l'angle polaire (azimutale) pour différents angles azimutales (polaire). Les mesures XPD fournissent des informations cristallographiques qui indiquent clairement que les feuillets de graphène sont organisés en structure graphite sur le substrat 6H-SiC (0001). Cette organisation résulte de l’effondrement de la maille de substrat. Enfin, le découplage à l'interface graphène/ 6H-SiC (0001) par l'oxygène a été étudié par XPS. La dernière étude concerne la croissance du film mince d'InP par MBE sur le substrat SrTi03 (001). L'intégration des semi-conducteurs III-V sur le Si, en utilisant la couche tampon d'oxyde SrTi03 est l'objet des intenses recherches, en raison des applications prometteuses dans le domaine de nano-optoélectronique. Les niveaux de coeur O1s, Sr3d, Ti2p, In3d, P2p ont été analysés et rapportés en fonction de l'angle azimutale à différents angles polaires. La comparaison des courbes XPD azimutales de Sr3d et In3d montre que les ilots InP sont orientées (001) avec la relation d'épitaxie; [110]InP(001 )/ / [100]! SrTi03 (001). La caractérisation morphologique par AFM montre des ilots InP facettés régulièrement dispersée à la surface
The main objective of this thesis is to study the chemical and physical properties at the surface or at the interface between thin layers by photoemission spectroscopy (XPS), photoelectron diffraction (XPD), and time resolved photoemission (PTR) . The experiments were conducted using an Alka source at INL or soft -X ray synchrotron radiation at Soleil, the French national Synchrotron facility. The first photoemission study has been performed on platinum deposited on thin Gd2(h layers grown by Molecular Bearn Epitaxy (MBE) on Si (111) substrate. The charge transfer between Pt and 0 at the interface causes a chemical shift to higher binding energies without changing the characteristic shape of the metal XPS peak. The XPD study shows that Pt is partially crystallized into two (111)-oriented do mains on Gd20 3 (111) with the in-plane epitaxial relationships [11 0] Pt (111) / / [11 0] Gd203 (111) and [101] Pt(111)/ / [11 0] Gd20 3 (111). In addition to bi-domains formation of platinum Pt (111) on Gd20 3 (111), a new ordered phase of platinum oxide Pt02 at the Pt/ Gd203 interface have been observed. The study of the background of the polar curves depending of the morphology has shown, that the film of Pt does not wet on the oxide, due to the low energy of interaction at the interface compared to the Pt thin layer. The second study has been interested to the photoemission time-resolved study of non-reactive metal / semiconductor model system. We have studied the thin layer gold (Au) growth on silicon (Si) substrate before and during annealing in TEMPO beam line (synchrotron Soleil).The XPS study, shows before annealing the formation of silicon native oxide on heterostructure at ambient temperature. The desorption of silicon oxide during annealing at low temperature induce photoemission intensity decreases with time. The desorption of oxide and alloy formation (AuSi) induce distribution of pits with cubic form at silicon surface due to gold etching activity. The third photoemission study has concerned thin films of a few layers of graphene obtained by solid-state graphitization from 6H-SiC (0001) substrates have been studied by X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD). The Cls core-level has been resolved into components, which have been associated with carbon from bulk SiC, carbon from graphene and carbon at the interface graphene/ 6H-SiC (0001). Then, the intensity of each of these components has been recorded as a function of polar (azimuth) angle for several azimuth (polar) angles. These XPD measurements provide crystallographic information which clearly indicates that the graphene sheets are organized in graphite-like structure on 6H-SiC(0001), an organization that results of the shrinking of the 6H-SiC (0001) lattice after Si depletion. Finally the decoupling of graphene from 6H-SiC (0001) substrate by oxygen intercalation has been studied from the XPS point of view. Finally, photoemission study has concerned thin film of InP (phosphor indium ) islands grown by Molecular Bearn Epitaxy (MBE) on SrTi03 (001) bulk substrate have been investigated by X-ray photoelectron spectroscopy and diffraction (XPS/ XPD).Integration of III-V semi-conductor on silicon wafer, via SrTi03 buffer is currently the subject of intense research because of its potentially interesting applications in future nano-optoelectronics. The Ols, Sr3d, Ti2p, In3d, and P 2p core level area have been studied as function of azimuth angle for different polar angles. Comparison of the XPD azimuth curves of Sr3d and In3d shows that islands InP are oriented (001) with an in-plane epitaxial relationship [110] InP(001 ) // [100] SrTi03 (001). AFM images shows that InP islands are regularly dispersed on the surface. Their shape is a regularly facetted half-sphere

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Blundell, Rebecca K. "XPS of quaternary ammonium and phosphonium ionic liquids." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/34589/.

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X-ray Photoelectron Spectroscopy (XPS) has been used to probe the influence of cation structure on fundamental interactions within Ionic Liquid (IL) systems. A series of tetraalkylammonium-based ILs and their phosphonium analogues have been investigated. A robust C 1s peak fitting model has been developed and described for the tetraalkylphosphonium and tetraalkylammonium families of ionic liquid, with comparisons made between the two series. Cation-anion interactions have been investigated to determine the impact of changing the cationic core from nitrogen to phosphorus on the electronic environment of the anion. Comparisons between long and short chain cationic systems, and the effect of cation conformational restriction, are also described. Additionally, a high-energy Ag Lα’ X-ray source has been utilised to probe the structure of the IL/vacuum interface using Energy-resolved XPS (ERXPS) for tetraalkylammonium- and tetraalkylphosphonium-based ILs, with comparison made to data obtained with Angle-resolved XPS (ARXPS) experiments using a standard Al Kα X-ray source. The capability of the Ag Lα’ source for IL analysis is confirmed, alongside the characterisation of previously undetected high energy core level photoelectron emissions. The effect of cation functionalisation is also studied by XPS, with a view to establish fine-tuning of charge transfer from anion to cation using electron-withdrawing substituents embedded within the alkyl side chain of the cation. Binding energy analysis indicated cation functionalisation had minimal influence on the electronic environment of the ionic head groups with respect to the non-functionalised analogues. The performance of ILs, with respect to cation functionalisation, as solvents in the Suzuki reaction is also reported in this Thesis, whereby evidence is provided for changing the nature of catalysis via cation functionalisation.

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Hung, Wing Wa. "FTIR and XPS of congruent and stoichiometric LiNbO3." HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/442.

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Ishii, Masaru. "Nanofabrication and STM/XPS Studies of Automotive Model Catalysts." Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485372.

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Scanning Tunnelling Microscopy (STM) and X-ray Photoelectron Spectroscopy (XPS) have been used in this work at various temperatures to study the mechanism of NOx storage reaction using model catalysts based mainly on the li02 (110) and the Pt (111) surfaces. The metals Pd and 8a were deposited using metal vapour deposition (MVDÃ‚Â». The key findings of this work are summarised below. Prior to the investigation of the 8a/Pdm02 (110) model catalyst, the NOx reactivity with the clean li02 (110) surface and Sa reactivity with li02 (110) were studied. NO and N02was adsorbed on the clean li02 (110)-(1 X2) surface in the molecule state at room temperature and dissociated 'at 373 K in the XPS. However, the amount of adsorbed NO or N02 was small, - less than 0.1 ML, and there was no evidence of or~ered structure of any reactivity between NO and li02 (110) in the STM. Upon increasing theÃ‚Â·annealing temperature, liN was formed at 873 K by reaction of dissociated N with interstitialli3 + diffused from the bulk. On the other hand, for a small amount of 8a deposition on the li02 (110) surface, the surface was disordered, but rows of 8a were seen running in the [001] direction of the li02 substrate. Upon sintering at 1073K in UHV, a (2x2) pattern was seen in LEED that originated from the Sa, although no ordering could be seen with STM. NO and O2were adsorbed on the Pd/Sarn02 (110) model catalysts, which was prepared by the 8a deposition and then Pd deposition at 673 K. However it was less reactive due to a low NO sticking probability and it was impossible to obtain atomic resolution images of model catalysts. A new approach, using inverse catalysts, was adopted, that is, Pt (111) was used as the support and Sa was deposited at room temperature. A locally ordered (2x2) structure was obtained. In the case of the annealing temperature at 1273 K, the variety of structures were formed, which these structures might be Sa overlayer, Sa/Pt alloy and BaO. One of these structures is the banded zig-zag structure on the terrace, with the unit cell can be defined as (8 ~ J. After the introduction of O2 atÃ‚Â· 573 K, large scale images of BaO were obtained. The average spacing is - 8.6 A, twice that expected for the (111) plane of BaO, which is due to reconstruction, resulting in the formation of (2x2) structure. There was a metastable state of a top layer of BaO/Pt (111) model catalyst at 573 K in the presence of O2, which is likely to be due to the formation of Ba02 confirmed by the atomic structure of Ba02 in the STM. Upon dosing NO and O2 at 573 K, the BaO particles grew and some growth was confirmed at step edges, especially O2 rich state. This effect is observed by an approximate increase in particle volume of 100%, which is consistent with about half of the oxide being converted to the nitrate. It is therefore postulated that a film of the nitrate effectively encapSUlates the oxide. This surface is unreactive to S02' However, when both S02 and O2 were co-dosed, the , ; atomic structure of BaO has rapidly disappeared which might be converted to the SUlphate, 8aS04, Which would result in poisoning of the real catalyst.

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ALMEIDA, CLARA MUNIZ DA SILVA DE. "XPS AND AFM ANALYSIS OF PVC/PHB BLENDS SURFACES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7338@1.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Neste trabalho, foram estudadas blendas formadas pelo polímero Policloreto de Vinila (PVC) e pelo polímero biodegradável Poli Hidroxibutirato (PHB), com diferentes concentrações relativas de cada polímero. As blendas foram preparadas em forma de membrana, com concentrações de PHB variando de 2 a 40%. A técnica utilizada para o preparo das amostras foi a evaporação do solvente, sendo dicloroetano o solvente utilizado. A composição química das superfícies das blendas foi caracterizada utilizando a técnica de espectroscopia de fotoelétrons induzida por raios-X (XPS). A morfologia e as propriedades mecânicas das amostras foram estudadas com o auxílio da microscopia de força atômica (AFM). Medidas de calorimetria diferencial exploratória foram realizadas a fim de conhecermos a miscibilidade das blendas formadas. Nas blendas formadas observou-se uma segregação de PHB para a superfície, sendo o percentual de PHB na superfície na faixa de 18±2%, mesmo para blendas com mais baixa concentração relativa de PHB. Entretanto o grau de cristalização do PHB em cada blenda aumenta com a incorporação do polímero na blenda. Foi observado um aumento na dureza conforme aumentamos a concentração de PHB na blenda. As blendas foram caracterizadas como parcialmente miscíveis.
In this work, the study of polymer blends surfaces formed by a biodegradable polymer (poly3-hydroxybutyrate, PHB) and PVC (polyvinyl chloride) with different molar percentages of PHB is presented. The blends samples were prepared as membranes with PHB molar concentrations from 2 to 40%. The technique used to prepare the membranes was the solvent-casting technique, using dichloroethene as solvent. The chemical composition of the blends samples surfaces were characterized by X-ray photoelectron spectroscopy (XPS). Their morphologies and mechanical properties were studied by atomic force microscopy (AFM). Differential scanning calorimeter measures were obtained in order to know the blends miscibility. A PHB surface segregation of 18±2% was observed, even for the blends with lower PHB concentrations. However, the degree of the PHB crystallization in each blend increases with the increasing incorporation of PHB in the blend volume. An increase in the blends hardness was observed while the PHB blends concentration increases. The blends were founded to be partially miscible.

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Clarke, Coby James. "Ionic liquids as designer molecules for XPS peak fitting." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33303/.

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X-ray photoelectron spectroscopy (XPS) of ionic liquids (ILs) has become a valuable tool for the investigations of IL interfacial and physicochemical properties. The complex signals that result from elements which occupy a variety of chemical states, for example the C 1s photoemission, are often interpreted through chemical intuition and peak fitting parameters. This Thesis will present a new method to determine exact photoemission binding energies (B.E.s), through the comparison of multiple spectra. The designer aspect of ILs has been exploited in order to produce salts with small structural modifications. By comparing the C 1s and N 1s photoemissions of the structurally related samples, difference spectra have been produced. These spectra show the relative shifting of electron density between the two signals, revealing the initial and final locations of the changing photoemission. Using this technique, the current C 1s peak fitting models of imidazolium and pyridinium ILs have been examined. A variety of 4,4’-bipyridinium salts have also been used as a structural variation of pyridinium ILs to show how molecular symmetry and normalisation may be utilised in order to produce photoemissions equivalent to fragments of molecules. The subsequent C 1s difference spectra have provided carbon peak fitting models for mono- and di-alkylated 4,4’-bipyridinium salts. Without the use of XP difference spectra, these known fitting models would be almost impossible to determine. Finally, multiple complex difference spectra have been used to identify the exact B.E.s of C 1s photoemissions from a series of nitrile functionalised ILs. The complex difference spectra have also been analysed by inverse Gaussian fittings to show how additional information may be extracted from the characteristic shapes. The ‘construction’ of photoemissions is also demonstrated, whereby known B.E. peaks are assembled to accurately reproduce experimentally determined XP spectra.

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Alvær, Ingrid, and Silje Henriette Westgaard. "Implementation of Company-Specific Production Systems (XPS) in Multinational Companies : A comparative case study concerning implementation of XPS in two subsidiaries of Elkem." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for industriell økonomi og teknologiledelse, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20978.

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In order for multinational manufacturing companies to strengthen their position in a competitive global market, continuous improvement of the companies’ operations has received an increasing focus since the 1990s. In order to develop a lasting culture for continuous improvement, an increasing number of companies have developed ‘improvement programs’ tailored towards the company’s specific operations. This type of improvement programs have been denoted as company-specific production systems (XPS), and are inspired by principles from Lean Manufacturing and the Toyota Production System (TPS). In Norway, the multinational materials producer Elkem has been one of the pioneers within XPS with its Elkem Business System (EBS). Elkem’s EBS center has since the early 2000s implemented EBS in most subsidiaries within the company. There has been a heated debate in research over the transferability of TPS, as some argue that TPS is a universal set of management tools that can be transferred everywhere, while others deny the universal transferability of TPS, emphasizing the unique socio-economic context in which TPS exists. This study adopts the contingency perspective, believing TPS to be universally transferable but subject to organizational and external factors which influence the implementation at the recipient site. The contribution of this study is to increase the understanding of the conditions that influence implementation of XPS in the subsidiaries of a multinational company (MNC). In order to accomplish this, a comparative case study of two manufacturing units in Elkem is conducted, investigating one plant in Norway (Elkem Salten) and one plant in Iceland (Elkem Iceland). The two plants were chosen on the basis of their many similarities (production facilities, size, number of employees), which on a general basis should qualify the plants for an equal starting point when implementing XPS. However, while Elkem Salten appears to have experienced great success when implementing XPS, Elkem Iceland has experienced many challenges and relapses. Consequently, this case study seeks to examine why the implementation of EBS has varied to such a large extent between the two plants. In order to investigate this issue, the study first identifies i) factors influencing the local EBS implementation at each plant, ii) factors influencing the inter-unit EBS related sharing between the plants. As the research approach of this study is explanatory, and the investigated events are contemporary and possible to observe directly, a case study design was chosen to carry out the research. Drawing on the strengths of such a research design, the study employs multiple sources of evidence such as: focused and in-depth interviews, direct observation and several types of documentation. Further, in order to guide the selection of empirical data, the study uses theory from five streams of literature: absorptive capacity theory, change management, institutional theory, corporate socialization theory and agency theory. The choice of literature is based on a literature review conducted as a preliminary study during the autumn of 2011, within the field of ‘transfer of procedural knowledge within MNCs’. The background for the comparative case study was a perception that Elkem Salten had achieved a higher level of success with its XPS implementation compared to Elkem Iceland. However, the findings of this study create a more nuanced impression of the current situation: Although Elkem Salten can be said to have had a more efficient XPS implementation, resulting in a more systemized approach to XPS, Elkem Iceland has in recent years shown significant improvement. Still, the plant lacks a sufficient systemization of the XPS implementation, resulting in a lower efficiency of the implementation process. Further, past events in the plant’s history have influenced the implementation of XPS, giving the plant a difficult start. Yet, the findings show that both plants have some common areas of improvement potential, such as increasing the motivation and involvement related to XPS among employees at the operating level. The study identifies 19 factors through the reviewed literature that are believed to have an influence on the implementation and inter-unit sharing of XPS within MNCs. These factors can be classified according to three levels of analysis: subsidiary level, corporate level and national level. The expected influence of the factors are formulated in 13 theoretical propositions, which are tested based on the empirical data. Four of the propositions find strong support and are thus expected to be generalizable to other MNCs. Further, a holistic perspective is used to evaluate all the factors, showing that they intertwine and influence each other across the three levels of analysis, and across the five theoretical perspectives. Although the discussion suggests a complex interaction of the identified factors, some particular factors are identified as major determinants for the different outcomes of the two plants. Of the identified factors related to implementation of XPS, the discussion shows that the organizational inertia at Iceland has had a major influence on the outset of the plant’s XPS implementation, and left a challenging basis for further implementation. Further, the plant at Salten has had a major advantage over the plant at Iceland due to a higher level of prior related knowledge of the plant manager, and the plant management’s higher level of knowledge acquisition. This advantage has resulted in a more systemized approach to the implementation process, and a higher level of cross-functional communication. Of the identified factors related to inter-unit sharing of XPS, the discussion reveals that the lack of standardization in XPS implementation has been an important underlying factor, causing the existence of other barriers to sharing. Most importantly, the lack of standardization has complicated the use of corporate socialization mechanisms. Further, the sharing between units in the case company has mainly been facilitated by an XPS knowledge center, acting as an intermediary. The empirical findings reveal that this arrangement has been a bottleneck in the XPS sharing process. These factors have commingled, and led to a limited sharing of XPS related knowledge in the case company. Therefore, many valuable experiences related to XPS implementation have not been shared between units, contributing to the high variation in the level of XPS implementation. For managers of multinational companies, the findings imply that managing XPS in a multinational company is a complex undertaking. The findings show that providing subsidiaries with theoretical knowledge of XPS tools and methodology is not enough in itself. In order to achieve higher levels of implementation, local managers must possess a practical understanding of how to translate XPS related knowledge to the every-day situation of the plant. Further, focus should be on systemizing the intra-unit, cross-functional communication as well as the inter-unit knowledge sharing. In addition, managers of the parent company must communicate the importance of XPS related knowledge sharing, and promote a common corporate identity to strengthen inter-unit ties within the MNC. This study provides two main contributions to the theory. First, the study’s findings indicate a strong link between the field of procedural knowledge transfer and the implementation and sharing of XPS in MNCs. Based on this link, a set of propositions for investigating XPS implementation and sharing in MNCs is provided for future research. Second, the study proposes a theoretical model which explains how the investigated theories interact to explain XPS implementation and sharing in multinational companies.

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Jahel, Ali. "Étude de l'ajout d'un promoteur au système Pt-Sn supporté sur alumine chlorée utilisé en reformage catalytique." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20233.

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L'objectif de ce travail était d'étudier de manière approfondie l'effet de l'indium dans des catalyseurs trimétalliques de reformage catalytique à base de platine, étain et indium. Des catalyseurs ont ainsi été synthétisés selon différents protocoles de préparation et de multiples caractérisations (spectroscopies Mössbauer d'étain, XANES, EXAFS, IR-CO, MEBT, chimisportion du CO, TPR et TPD) ont été mises en oeuvre afin d'élucider l'impact de l'indium sur la nature des phases métalliques présentes au sein du catalyseur. Il a ainsi été montré que la nature des sites métalliques dépend de la méthode d'introduction de l'indium. Quand l'indium est précipité avec la source d'alumine des alliages de type PtxSn sont obtenus alors que lorsque les métaux sont imprégnés sur la surface de l'alumine des espèces subsitutionnelles Pt-Sn sont formées. Il a aussi été montré que l'augmentation de la teneur en indium entraine une augmentation de la concentration atomique d'étain dans les alliage PtxSn et un remplacement de l'étain par l'indium dans les espèces substitutionnelles. Nous avons également réussi à préparer des catalyseurs avec des quantités élevées d'alliage Pt3Sn sur la base des connaissances acquises sur l'impact de l'indium et en déposant l'étain par une réaction organométallique contrôlée de surface. D'un point de vue catalytique, les tests de reformage du n-heptane mettent en évidence l'impact positif de l'indium puisque les catalyseurs à base de Pt-Sn-In sont moins sélectifs pour les réactions parasites d'hydrogénolyse et d'hydrocraquage et plus sélectifs pour l'isomérisation que les catalyseurs à base de Pt-Sn
This work consists of a detailed study on the effect of indium in alumina supported trimetallic PtSnIn-based naphtha reforming catalysts. These catalysts were reproduced using different preparation protocols and the indium effect was investigated using 119Sn Mössbauer spectroscopy, XANES, EXAFS spectroscopies, IR-CO, STEM, CO chemisorption, TPR and TPD. It appears that the nature of the metallic active centres depends on the method with which indium was introduced. When co-precipitating the indium precursor with the Al source, PtxSn alloys were formed, whereas when metals were impregnated on the surface, substitutional Pt-Sn alloys were observed. Increasing the In content in the frst type of catalysts leads to an increase in the Sn concentration in PtxSn alloys, whereas a gradual replacement of Sn by indium in susbstitutinal alloys is observed in the second type of catalysts. These results allowed preparing catalysts with high Pt3Sn alloy contents using the effect of indium in catalysts prepared by Sn organometallic controlled surface reactions (CSR). From a catalytic point of view, n-heptane reforming tests show that trimetallic PtSnIn-based catalysts are less selective to hydrogenolysis and hydrocracking reactions, and highly selective to isomerisation, compared to the bimetallic PtSn-based catalyst

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Kozłowska, Magdalena. "Winkelaufgelöste XPS: Optimierung der mathematischen Modellierung und deren experimentelle Überprüfung." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976612089.

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Untiedt, Ingo. "XPS- und SIMS-Untersuchungen an Systemen vom Typ LaNi5-xMexDy." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=967391385.

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Kozlowska, Magdalena. "Winkelaufgelöste XPS: Optimierung der mathematischen Modellierung und deren experimentelle Überprüfung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1126554580144-69045.

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Heutzutage ist die Entwicklung neuer Technologien stark auf die Miniaturisierung und die Herstellung von Materialien im Nanometer-Bereich und deren Charakterisierung ausgerichtet. Besonders interessant sind Informationen über hergestellte "sandwich" Strukturen betreffs Art und Anzahl der Schichten, Dicke der Schichten und deren chemische Zusammensetzung. Die chemischen Informationen von den Proben sind sowohl nahe der Oberfläche als auch in tiefer liegenden Schichten (vergrabene Schichten) von Interesse. Da die üblichen Tiefenprofilverfahren durch das Auftreten von ionenstrahlinduzierten Probenschädigungen hier versagen, sind zerstörungsfreie Untersuchungen der Probenstruktur von Bedeutung. Winkelaufgelöste Röntgenphotoemissionsspektroskopie (ARXPS) ist eines der Verfahren, die ohne Beschädigung der Schichtstruktur der untersuchten Materialen Informationen über dünne Gebiete der Probe liefert. Die Charakterisierung der Probe basiert auf der Analyse der austretenden Photoelektronen unter verschiedenen Austrittswinkeln, weil damit die effektive Informationstiefe durch Analyse von Photoelektronenstrom aus verschiedenen Tiefen verändert wird. Die Untersuchungstiefe bei diesem Verfahren ist maximal ~10 nm. Aus dem ARXPS-Verfahren ist nur eine indirekte Information zu erhalten. Deshalb braucht man ein Werkzeug, mit dem die untersuchten Proben mit Hilfe von mathematischen Modellen quantitativ beschrieben werden können. In der vorliegenden Doktorarbeit wird gezeigt, dass die ARXPS-Modellrechnung unter bestimmten Voraussetzungen eine sinnvolle Methode zur Analyse von dünnen Barriere-, Oxid- und Segregationsschichtsystemen ist. Die Quantifizierung der ARXPS-Daten ist nur dann erfolgreich, wenn nicht nur der Einfluss der Abklinglänge der Photoelektronen berücksichtigt wird, sondern auch der Einfluss der mittleren Atomvolumina der Matrix in geeigneter Schichten und der korrigierten Empfindlichkeitsfaktoren berücksichtigt wird. Die Anpassung zwischen experimentellen und berechneten Daten verläuft unter Verwendung bestimmter Rand- und Grenzbedingungen durch Anwendung mathematischer Methoden gleichzeitig für alle betrachtete Winkel. Das Verhalten der ARXPS-Modellrechnung wurde unter verschiedenen Bedingungen überprüft. Zu diesem Zweck wurde eine theoretische Struktur simuliert, deren Verhalten (berechnete Schichtdicken, Bedeckungsgrad der Oberfläche mit der Kontamination, chemische Zusammensetzung der Schichten) untersucht wurde hinsichtlich der Einflüsse von verschiedener Dicken, von Rauhigkeiten an der Probeoberfläche, der Art der Kontamination an der Oberfläche die aus der ex situ Präparation resultiert, und der "Qualität" der betrachteten Information während der Quantifizierung (Peak-Fit Prozeduren). Zur Demonstration der Möglichkeiten der Modellrechnung wurden zwei Systeme untersucht. Das erste Schichtsystem Co/Al2O3/Al enthält eine dünne vergrabene Aluminiumoxid-Barriere, die durch Plasma-Oxidation mit Electron Cyclotron Resonance (ECR) bei unterschiedlichen Oxidationszeiten hergestellt wurde. Die Modellierung der Proben mit der ARXPS-Modellrechnung ergibt unterschiedliche Dicken von Al2O3, die mit der Zeit der Oxidation korrelieren. Je größer die Oxidationszeit ist, desto dickere Aluminiumoxidschichten bilden sich. Die Untersuchung der Alterungsprozesse an den ECR-Proben ergibt, dass die Dicke der Aluminiumoxide nicht beeinflusst wurde. Das bestätigt, dass die Co-Schicht erfolgreich Al2O3 vor weiterer Oxidation schützt. Das zweite Beispiel betrifft eine S/Fe Struktur, die während der Wärmebehandlung durch Schwefel-Segregation auf einer Fe(100)-Oberfläche entstanden ist. Mit Hilfe der ARXPS-Modellrechnung kann der Bedeckungsgrad mit dem Schwefel der Fe- Oberfläche berechnet werden. Um die Ergebnisse der Modellierung zu verifizieren, wurden die ausgewählten Strukturen mit anderen Methoden (z.B.: TEM, EELS, XRR) untersucht.

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Cass, Lindsey Margaret Rose. "An EPR and XPS study of paramagnetic species in wool." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329602.

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Kozlowska, Magdalena. "Winkelaufgelöste XPS: Optimierung der mathematischen Modellierung und deren experimentelle Überprüfung." Doctoral thesis, Technische Universität Dresden, 2004. https://tud.qucosa.de/id/qucosa%3A24564.

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Heutzutage ist die Entwicklung neuer Technologien stark auf die Miniaturisierung und die Herstellung von Materialien im Nanometer-Bereich und deren Charakterisierung ausgerichtet. Besonders interessant sind Informationen über hergestellte "sandwich" Strukturen betreffs Art und Anzahl der Schichten, Dicke der Schichten und deren chemische Zusammensetzung. Die chemischen Informationen von den Proben sind sowohl nahe der Oberfläche als auch in tiefer liegenden Schichten (vergrabene Schichten) von Interesse. Da die üblichen Tiefenprofilverfahren durch das Auftreten von ionenstrahlinduzierten Probenschädigungen hier versagen, sind zerstörungsfreie Untersuchungen der Probenstruktur von Bedeutung. Winkelaufgelöste Röntgenphotoemissionsspektroskopie (ARXPS) ist eines der Verfahren, die ohne Beschädigung der Schichtstruktur der untersuchten Materialen Informationen über dünne Gebiete der Probe liefert. Die Charakterisierung der Probe basiert auf der Analyse der austretenden Photoelektronen unter verschiedenen Austrittswinkeln, weil damit die effektive Informationstiefe durch Analyse von Photoelektronenstrom aus verschiedenen Tiefen verändert wird. Die Untersuchungstiefe bei diesem Verfahren ist maximal ~10 nm. Aus dem ARXPS-Verfahren ist nur eine indirekte Information zu erhalten. Deshalb braucht man ein Werkzeug, mit dem die untersuchten Proben mit Hilfe von mathematischen Modellen quantitativ beschrieben werden können. In der vorliegenden Doktorarbeit wird gezeigt, dass die ARXPS-Modellrechnung unter bestimmten Voraussetzungen eine sinnvolle Methode zur Analyse von dünnen Barriere-, Oxid- und Segregationsschichtsystemen ist. Die Quantifizierung der ARXPS-Daten ist nur dann erfolgreich, wenn nicht nur der Einfluss der Abklinglänge der Photoelektronen berücksichtigt wird, sondern auch der Einfluss der mittleren Atomvolumina der Matrix in geeigneter Schichten und der korrigierten Empfindlichkeitsfaktoren berücksichtigt wird. Die Anpassung zwischen experimentellen und berechneten Daten verläuft unter Verwendung bestimmter Rand- und Grenzbedingungen durch Anwendung mathematischer Methoden gleichzeitig für alle betrachtete Winkel. Das Verhalten der ARXPS-Modellrechnung wurde unter verschiedenen Bedingungen überprüft. Zu diesem Zweck wurde eine theoretische Struktur simuliert, deren Verhalten (berechnete Schichtdicken, Bedeckungsgrad der Oberfläche mit der Kontamination, chemische Zusammensetzung der Schichten) untersucht wurde hinsichtlich der Einflüsse von verschiedener Dicken, von Rauhigkeiten an der Probeoberfläche, der Art der Kontamination an der Oberfläche die aus der ex situ Präparation resultiert, und der "Qualität" der betrachteten Information während der Quantifizierung (Peak-Fit Prozeduren). Zur Demonstration der Möglichkeiten der Modellrechnung wurden zwei Systeme untersucht. Das erste Schichtsystem Co/Al2O3/Al enthält eine dünne vergrabene Aluminiumoxid-Barriere, die durch Plasma-Oxidation mit Electron Cyclotron Resonance (ECR) bei unterschiedlichen Oxidationszeiten hergestellt wurde. Die Modellierung der Proben mit der ARXPS-Modellrechnung ergibt unterschiedliche Dicken von Al2O3, die mit der Zeit der Oxidation korrelieren. Je größer die Oxidationszeit ist, desto dickere Aluminiumoxidschichten bilden sich. Die Untersuchung der Alterungsprozesse an den ECR-Proben ergibt, dass die Dicke der Aluminiumoxide nicht beeinflusst wurde. Das bestätigt, dass die Co-Schicht erfolgreich Al2O3 vor weiterer Oxidation schützt. Das zweite Beispiel betrifft eine S/Fe Struktur, die während der Wärmebehandlung durch Schwefel-Segregation auf einer Fe(100)-Oberfläche entstanden ist. Mit Hilfe der ARXPS-Modellrechnung kann der Bedeckungsgrad mit dem Schwefel der Fe- Oberfläche berechnet werden. Um die Ergebnisse der Modellierung zu verifizieren, wurden die ausgewählten Strukturen mit anderen Methoden (z.B.: TEM, EELS, XRR) untersucht.

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Swarbrick, Janine Cathy. "Hydrogen bonded nanostructures on surfaces : STM, XPS and electrospray deposition." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10245/.

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Molecules adsorbed on surfaces can show fascinating characteristics and properties. In particular the assembly of molecules into ordered arrays on surfaces is of great interest, whether one considers possible commercial applications or fundamental physical interactions. Specifically, the mediation of ordered molecular arrangements via hydrogen bonding yields many interesting structures. This thesis focusses primarily on the importance of hydrogen bonding between molecules on surfaces in ultra high vacuum (UHV), and how these interactions govern ordered phase formation. Scanning tunnelling microscopy is used to investigate the planar perylene derivative PTCDA on the hexagonal Ag-Si(111) (sqrt 3) * (sqrt 3)R30^o surface alone, with C_{60}, and with melamine. Interesting molecular architectures are observed including a square PTCDA arrangement, and a PTCDA-melamine hexagonal network which contains both stabilising hydrogen bonds and potentially repulsive interactions. Hydrogen bonding systems of pyridinecarboxylic acids on rutile TiO_2 have been studied using photoemission spectroscopy. Ordered films of isonicotinic acid were investigated using valence band photoemission, and an angular dependence is observed in valence band spectra as the angle between the sample and the incoming light is changed. Biisonicotinic acid was also studied on TiO_2 and on gold using core level photoemission to determine how it bonds to these surfaces; it is thought to chemisorb to both TiO_2 and gold through its carboxylic acid groups in an upright orientation. Some large or fragile molecules cannot be sublimed in vacuum for deposition as they fragment. Another research focus has been the development of a technique for depositing non-volatile molecules in vacuum directly from solution. Concepts of electrospray ionisation have been used in the development of a vacuum electrospray deposition system. The molecule is dissolved or suspended in solution and electrosprayed directly into a vacuum environment, with the result that molecules of interest are deposited on a sample without fragmentation or corruption. The samples may then be investigated with vacuum based techniques such as scanning tunnelling microscopy and photoemission spectroscopy.

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Shamout, Karim [Verfasser], Carsten [Akademischer Betreuer] Westphal, and Mirko [Gutachter] Cinchetti. "MgO/Co/GaAs(001) - an interface analysis by means of XPS and XPD / Karim Shamout ; Gutachter: Mirko Cinchetti ; Betreuer: Carsten Westphal." Dortmund : Universitätsbibliothek Dortmund, 2018. http://d-nb.info/1173421467/34.

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22

TRAVAGLIA, ELISABETTA. "Study of the growth and of the electronic and structural properties of two-dimensional materials." Doctoral thesis, Università degli Studi di Trieste, 2018. http://hdl.handle.net/11368/2919624.

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Negli ultimi dieci anni, dopo l'isolamento del grafene e lo studio delle sue eccezionali proprietà, la comunità scientifica ha rivolto la propria attenzione ai cristalli bidimensionali (2D), ed in particolare ai dicalcogenuri dei metalli di transizione (TMDCs). Sebbene molto sforzo sia stato profuso per portare la loro produzione su scala industriale e integrarli all'interno dei futuri dispositivi elettronici ed optoelettronici, un metodo che porti alla scalabilità di questi materiali è ancora una sfida. Questa tesi è focalizzata sul meccanismo di crescita dei TMDCs e studia gli aspetti legati al processo di nucleazione e le fasi che portano alla formazione del cristallo, in modo da identificare le condizioni ottimali per promuovere l'estensione dei domini dei layer. Inoltre la tesi investiga i metodi che permettono la produzione di campioni TMDCs con una singola orientazione, consentendo di ottenere una migliore qualità dei layer, grazie alla riduzione del numero di bordi di grano formati dalla coalescenza di isole con diversa orientazione e aprendo strade nuove verso l'applicazione di concetti come la spin-valletronica ai dispositivi di nuova generazione. La prima parte della tesi è dedicata alla crescita di MoS2 su diversi substrati metallici, come Au(111), Ag(111) e Ag(110), con lo scopo di investigare l'effetto dell'interazione tra il layer sovrastante e il substrato, e l'effetto della simmetria del substrato sulla formazione di layer estesi di MoS2. Per ottenere layer altamente cristallini formati da domini orientati allo stesso modo, è stato implementato un nuovo protocollo di crescita su Au(111) ed adattato poi per gli altri substrati, sebbene esso su questi ultimi producesse due orientazioni, pur mantenendo alta la cristallinità. E’ stata caratterizzata la struttura elettronica del MoS2/Au(111), con particolare interesse alla polarizzazione di spin fuori dal piano delle bande vicino a K e -K della zona di Brillouin. Abbiamo successivamente esplorato la crescita di WS2 su Au(111) per valutare la versatilità del metodo di crescita da noi sviluppato. Mediante la calibrazione dei parametri di crescita, sono stati ottenuti dei campioni altamente cristallini di WS2 con una singola orientazione, che sono stati successivamente utilizzati per studiare il coupling elettrone-fonone, derivando quindi preziose informazioni per le applicazioni sui device. L'ultima parte della tesi è dedicata all'intercalazione dell'ossigeno al di sotto del grafene cresciuto su Ir(111), con lo scopo di verificare se la presenza del grafene possa cambiare la geometria degli atomi di ossigeno sull'Ir(111). Comparando i risultati ottenuti dall'adsorbimento dell'ossigeno sull'Ir(111) pulito con quelli in presenza del grafene, è stato possibile vedere che le strutture dell'ossigeno formate sotto il grafene possono essere riprodotte sull'Ir(111) dosando delle specie fortemente ossidanti come l'NO2, concludendo che il grafene non interferisce in maniera apprezzabile con l'interazione adsorbato-substrato.
In the past ten years, after the isolation of graphene and the discovery of its outstanding properties, the scientific community has aimed its attention on a new class of materials, the two-dimensional (2D) atomic crystals, and particularly on the transition metal dichalcogenides (TMDCs). Though much effort is spent in the perspective of scaling up the production and integrating these materials in future electronic and optoelectronic devices, so far, a way towards sizable growth of 2D-TMDCs is still a challenge. This thesis is focused on the growth mechanism of TMDCs and studies aspects related to the nucleation process and the steps that lead to the formation of the crystals, in order to identify the optimal conditions to promote the increase of the domain size of the layers. In addition, the thesis investigates on the methods to produce TMDCs samples with a single domain orientation that allows to obtain better quality layers, thanks to the reduce presence of grain boundaries formed by the coalescence of islands with different orientations, and allows to open the path towards novel device concepts such as those based on the spin-valleytronic. This thesis is mainly devoted to the growth of MoS2 on different metallic substrates, namely Au(111), Ag(111) and Ag(110), with the aim of investigating the effect of the interaction between adlayer and substrate, and the effect of the substrate symmetry in the formation of extended layers of MoS2. In order to obtain a single domain orientation with respect to the substrate, a new growth protocol was developed on Au(111) and adapted also for the other substrates. The electronic structure of the MoS2/Au(111) sample was characterized, with a special attention to the out-of plane spin polarization of the bands near K and -K points of the Brillouin zone. We have subsequently explored the growth of single layer WS2 on Au(111) in order to evaluate the versatility of the developed growth method. By finding the proper growth parameters, we obtained high quality WS2 samples with a single orientation, that has been subsequently used to study the electron-phonon coupling thus deriving useful information for electronic device applications. The last part of the thesis is dedicated to the oxygen intercalation under graphene grown on Ir(111), with the aim of verifying whether the presence of graphene changes the adsorption geometry of the oxygen atoms on Ir(111). By comparing the results of oxygen adsorption on the bare Ir surface with those in the presence of graphene, it was possible to see that the oxygen overstructures formed under graphene can be reproduced on bare Ir(111) by dosing strongly oxidizing species such as NO2, concluding that graphene does not affect the adsorbate-substrate interaction.

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Zier, Michael. "Untersuchungen zu Schichtwachstum und Grenzflächen an Ta-basierten Dünnschichten mittels XPS." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1196176876848-09306.

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In der vorliegenden Arbeit wird das Wachstum von Ta- und TaN-Schichten auf Si- und SiO_2-Substraten untersucht Die Schichten werden dabei unter technologienahen Bedingungen mittels Magnetron-Sputtern abgeschieden. Die Untersuchungen erfolgen hauptsächlich mit winkelaufgelöster röntgenstrahlungsangeregter Photoelektronenspektroskopie (ARXPS). Die Analysen erfolgen in situ, ohne Unterbrechung des Ultrahochvakuums, um die Deposite vor Oxidation und Kontamination zu schützen. Zur zerstörungsfreien Tiefenprofilanalyse wird ein Quantifizierungsalgoritmus beschrieben und angewandt. Für die Kombination Ta/Si wird die Bildung einer zunächst unvollständigen TaSi_2-Schicht, danach das Aufwachsen von Ta auf diese Zwischenschicht beobachtet. Für die Kombination Ta/SiO_2 wird eine Reduktion des SiO_2-Substrates bei gleichzeitigem Aufwachsen von Ta-Oxiden beobachtet. Auf dem durchmischten Schichtstapel wächst danach Ta auf. Für die Kombination TaN/Si wird die Bildung einer Si-N-Zwischenschicht bei gleichzeitigem Wachsen einer TaN-Schicht beobachtet. Für die Kombination TaN/SiO_2 wird das Aufwachsen einer TaN-Schicht ohne Ausbilung von Zwischenschichten beobachtet. Das Wachstumsverhalten des Ta/Si-Systems wird zusätzlich mit in situ Rastertunnelmikroskopie und -spektroskopie untersucht. Es wurden Untersuchungen zur thermischen Stabilität von abgeschiedenen Schichten an den Systemen Ta/Si und TaN/SiO_2 durchgeführt. Als mögliche Alternative zur winkelaufgelösten XPS wurden Untersuchungen mittels synchrotronstrahlungsangeregter Photoelektronenspektroskopie bei variierter Anregungsenergie durchgeführt.

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Chalker, Paul R. "The oxidation of nickel and titanium studied by XPS and XAES." Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371219.

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Challinor, David Clive. "An XPS study of the reactivity of tin and magnesium surfaces." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375919.

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Fraser, Stuart. "Angle resolved XPS study of the migration of a silane additive." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369936.

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Valov, Ilia, Bjoern Luerßen, Eva Mutoro, and Jürgen Janek. "In situ XPS study on the electrochemical nitrogen incorporation in YSZ." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-187944.

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Valov, Ilia, Bjoern Luerßen, Eva Mutoro, and Jürgen Janek. "In situ XPS study on the electrochemical nitrogen incorporation in YSZ." Diffusion fundamentals 12 (2010) 66, 2010. https://ul.qucosa.de/id/qucosa%3A13896.

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Lunt, Patrick Joseph Brian. "XPS studies of surface ageing and discharge processes in polymeric insulators." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/xps-studies-of-surface-ageing-and-discharge-processes-in-polymeric-insulators(2329d184-6677-4981-988e-e17b95bae229).html.

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The ageing of polymer insulation occurs under long-term exposure to high electric fields and has attracted research due its relevance to high voltage insulation. In this work, polymers that have been electrically aged via a number of methods have been investigated using X-ray photoelectron spectroscopy (XPS). Despite some use in the investigation of outdoor insulation surfaces, XPS has not been used for investigations of polymer bulk electrical ageing before now. The first XPS measurements, using both small spot analysis and XPS imaging, are presented from the exposed inner surfaces of electrically aged artificial voids and electrical breakdown channels, as well as corona discharge aged surfaces and spark discharge by-products. XPS is shown to be a valuable technique for the investigation of polymer electrical ageing. Investigations into breakdown channels are supported by data acquired using X-ray photoemission electron microscopy (XPEEM) and scanning electron microscopy (SEM).Results show that the chemistry present at these surfaces takes the form of significant oxidation over a wide area with localised production of graphitic carbon. C-O-, C=O, and O-C=O species are detected in all cases. It is found that similar ageing products are present regardless of the ageing process or material investigated. However, the level of oxidation and relative ratio of the species seen with XPS is shown to be highly dependant on oxygen availability. Greater intensity of carbon oxides, and a shift towards highly oxidised species, is observed when there is more oxygen in the system. XPS imaging of breakdown channels reveals that high concentrations of oxidised components form on the outer edges of the channel, with graphitic carbon forming in the central regions. In addition, evidence for degradation is seen to extend at least 300 μm from channels in XPS imaging and at least ~650 μm in XPS line scans. Variation with the applied discharge energy was investigated for breakdown channels and spark discharge ageing. Evidence is seen for an energy dependence on the breakdown products, with higher energies producing relatively higher graphitic carbon and reduced oxidation products. Further, the relationship between the applied voltage and graphitic carbon concentration suggests an activated process with an energy barrier before graphitic carbon formation starts. XPS observations are supported by confocal Raman microprobe spectroscopy (CRMS) results from artificial voids and electrical breakdown channels, which identify graphitic carbon on a fluorescent background as the main features. XPS data indicate oxidised species are the origin of the fluorescence seen and provides quantitative information on the levels, chemical states and spatial distribution of these species and of graphitic carbon.

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Taylor, Michael. "To F-SIMS/XPS chemical depth profiling of synthetic polymer hydrogels." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/38755/.

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Over the last decade the beneficial properties of hydrogels as artificial cell culture supports have been extensively investigated. Certain synthetic hydrogels have been proposed to be similar in composition and structure to the native extracellular matrix of the stem cell niche, their in vivo cell habitat, which is a powerful component in controlling stem cell fate. The stem cell differentiation pathway taken is influenced by many factors. When culturing cells within or upon hydrogels the choice can be strongly dependent on the underlying 3D hydrogel chemistry which strongly influences hydrogel-cell interactions. The interrelationship between hydrogel chemistry and that of biomolecules in controlling cellular response ideally requires analysis methods to characterise the chemistry without labels and normally in 3D. Time-of-flight secondary ion mass spectrometry (ToF SIMS) has the potential to be utilised for through thickness characterisation of hydrogels. The frozen-hydrated sample format is well suited to minimise changes associated with dehydration or the complication of chemical ‘fixation’. There is however significant challenges associated with this sample format. Frost formation occurs on cold samples in the ambient atmosphere affecting the quality of chemical information acquired from depth profiling frozen hydrogel samples. We develop a simple method to remove this frost by blowing with gas prior to entry into the instrument which is shown to produce remarkably good profiles on a poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel film where a model protein, lysozyme, is incorporated to demonstrated how biomolecule distribution within hydrogels can be determined. A comparison of lysozyme incorporation is made between the situation where the protein is present in the polymer dip coating solution and lysozyme is a component of the incubation medium. It is shown that protonated water clusters H(H2O)n+ where n=5-11 that are indicative of ice are detected through the entire thickness of the pHEMA and the lysozyme distribution through the pHEMA hydrogel films can be determined using the intensity of characteristic fragment secondary ions. Quantitative TOF-SIMS analysis is highly desirable in biomaterial analysis as the amount and type of molecule in the material analysed may be determined. This has significant interest in hydrogel chemical analysis as cellular development on or within hydrogels may be highly influenced by the concentration and type of soluble molecule. Unfortunately, the matrix effect in SIMS changes the measured signal intensity of the analyte, preventing accurate quantitation. For this reason, we apply X-Ray Photoelectron Spectroscopy (XPS) on the equivalent samples as the ToF-SIMS in an attempt to correlate molecular ion yields to exact elemental concentrations. Similarly to ToF-SIMS the frozen-hydrated format in XPS is however still relatively unexplored. We apply the developed preparatory procedure in 3D XPS analysis of pHEMA/lysozyme hydrogel films in a hydrated state. We show that this format is suitable for alternative high vacuum analysis techniques. Furthermore, we show that lysozyme ingression and concentration can be determined through XPS. This work describes the first example of the characterisation of a hydrogel by ToF-SIMS and XPS in a frozen hydrated format, characterising hydrogels in a format most reflecting its native hydrated state at culture conditions. The described procedure allows for the mapping of biomolecules in a label free manner in 3D, furthermore allowing quantitative determination of biomolecule concentrations in hydrogels.

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RIGOLDI, AMERICO. "Sulfur chemical state at mineral surfaces - An XPS and XAES investigation." Doctoral thesis, Università degli Studi di Cagliari, 2011. http://hdl.handle.net/11584/266328.

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During the interaction of sulphide minerals with the environment many reactions may occur. The knowledge of sulphur chemical state is important in order to clarify the mechanisms of oxidation/dissolution and precipitation reactions also in biotic conditions on the surface of these minerals. To date different hypotheses have been proposed for identifying the sulphur compounds that may form but no consensus is reached so far because the identification has been carried out either only on the basis of the photoelectron signals or combining the photoelectron signal with the centroid of the X-ray induced SKLL Auger line. The objectives of this thesis are: the development of an analytical strategy for the unambiguous identification of sulphur chemical state in nanometer thick layers that form on mineral surfaces after leaching. To this purpose the acquisition of detailed spectra of a series of metal sulphides and of model systems made of mixtures of sulphur and polysulphides prepared under controlled conditions is necessary. Second objective was the establishment of the curve-fitting procedure to allow the separation of the different components present on the surface (sulphide, polysulphides, sulphates) not only of the S2p XP-spectra but also of the SKLL spectra. Based on these results the Auger parameter values will be determined and will be used together with the chemical state plot to distinguish the chemical state of sulphur species formed on the mineral surfaces after different surface treatments. In this way, the surface reactivity of sulphide minerals and more in general, of sulphur –bearing particles will be determined The present work is organized in six chapters: the first one presents a short overview on the environmental problems that may occur when sulphide minerals, especially, those bearing eco-toxic elements such as arsenic, are exposed to the acidic mine drainage in the presence of oxidants and/or of microorganisms which enhance oxidation kinetics. It then outlines the analytical strategy that was adopted in this work for the identification of the sulphur chemical state. In the second chapter a literature survey is provided: it underlines the role of sulphur in sulphide bearing minerals: Section 2.1 reports information about the mineral enargite and the chemical state of sulphur on its surface as it is available to date. Section 2.2 deals with the literature on the possibility of using the KLL Auger transition. In chapter 3 a brief description of X-ray photoelectron and X-ray excited Auger electron spectroscopy is given while the materials and methods used in the present work are presented in chapter 4. In chapter 5 – results and discussion - the X-ray photoelectron spectroscopy (XPS) and X-ray excited Auger electron spectroscopy (XAES) analyses on alkaline and transition metal sulphide and sulphates, polysulphides and sulphide minerals are presented. In particular the spectra recorded on the S2p and S KLL lines of the sulphides and sulphates are shown: they were collected for getting the peak fitting parameters and apply them to the model systems obtained by mixing sulphur with sodium tetrasulphide and to investigate the composition of mineral surfaces. Minerals were analysed freshly cleaved, ground and after air exposure. The chemical state of sulphur in sulphates, sulphides (alkali- and transition metal compounds, minerals) and polysulphide is then discussed. For the first time the X-ray excited Auger SKLL lines were fitted with parameters based on standards. In this way, which can be considered as an extension of previous work, a separation of the different components and a more precise determination of their kinetic energy were achieved. The Auger parameter and the chemical state plot were obtained by combining the S2p photoelectron lines and the SKLL Auger lines. On this basis a clear distinction of the chemical state of sulphur in sulphates, in alkali sulphides and in transition metal sulphides was possible. The chemical state of sulphur in the bulk of minerals such as enargite or pyrite was determined. The chemical state of sulphur that formed on the surface of compounds after exposure to air or after grinding was found to vary according the coordinating metal and its concentration. It can be assessed that the analytical approach developed in the presented thesis and based on the curve – fitting procedure applied to the X-ray induced Auger electron spectroscopy appears to be a very promising method for identifying the chemical state of sulphur and for providing a new insight in the surface chemistry of sulphide minerals.

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32

Polčák, Josef. "Analýza povrchů pevných látek pomocí fotoelektronů - počítačové řízení experimentů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-233975.

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Doctoral thesis is dealing with the methods for analysis of surfaces by photoelectrons being emitted by X-ray radiation. The methods are: X-ray Photoelectron Spectroscopy - XPS, Angle-resolved XPS - ARXPS and X-ray Photoelectron Diffraction - XPD. The work is especially focused on a method of ARXPS, which is used for the depth compositional analysis of sample surfaces. To obtain an information about the depth composition from the measured ARXPS spectra, a calculation software in the Matlab environment has been developed. The software has been tested both for simulated and real sample data. For an experimental implementation of these methods, a complete manipulation system has been developed. It ensures the transport of samples inside a vacuum apparatus and the experiment itself. The system is controlled mainly by a software and enables to run the experiments automatically.

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33

Grissa, Rabeb. "Apport de la Spectroscopie Photoélectronique à rayonnement X à l’étude de nouveaux matériaux d’électrodes pour microbatteries au lithium." Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3002.

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Les principales évolutions requises pour répondre aux besoins de la microélectronique visent à intégrer une micro-source d’énergie susceptible de fonctionner à plus bas potentiel que les systèmes actuels. Ainsi, en vue de répondre à cette demande, ce travail de recherche s’est focalisé sur l’étude, principalement par spectroscopie photoélectronique à rayonnement X (XPS), de deux matériaux d’électrode positive fonctionnant à 3 V vs Li+/Li : le spinelle LiMn2O4 et le Nasicon Fe2(MoO4)3. Le bismuth, matériau potentiel d’électrode négative susceptible de remplacer le lithium métallique et de subir le procédé de soudure classiquement utilisé en microélectronique (le solder reflow), est également étudié dans le cadre de cette thèse. Avant de caractériser ces matériaux en systèmes tout-solide, la première étape consiste à en étudier les comportements électrochimiques en électrolytes liquides. A cet effet, des couches minces d’une épaisseur d’environ 500 nm sont préparées par pulvérisation cathodique après une étape d’optimisation des paramètres de dépôt (puissance, pression partielle et totale dans l’enceinte de dépôt, température de recuit, …), puis caractérisées sur les plans structural (DRX), morphologique (SEM) et chimique (XPS, RBS, ICP). L’analyse des échantillons par XPS en fin de décharge et de charge a permis de mieux comprendre et d’expliquer les réactions électrochimiques se produisant au sein des matériaux et aux interfaces électrode/électrolyte dans les batteries au lithium. Une étude comparative avec un cyclage face au sodium a également été menée dans le cas du molybdate de fer et du bismuth, ce qui a permis d’identifier des comportements spécifiques lors de l’insertion/désinsertion des deux alcalins. L’homogénéité de la lithiation/sodation des couches minces a également été étudiée à partir de différentes analyses XPS menées après un procédé de décapage permettant de s’affranchir de la couche de passivation formée à l’interface électrode/électrolyte.Cette étude contribue à une meilleure connaissance des matériaux d’électrodes en cyclage pour micro-batteries au lithium et présente des perspectives très intéressantes d’intégration dans des dispositifs « tout solide »
The main evolutions required for microelectronic applications aim to integrate an energy microsource operating at lower potential than current systems. Thus, in order to meet this demand, this research work has been focused on the study, mainly by X-ray photoelectron spectroscopy (XPS), of two positive electrode materials operating at 3 V vs Li+/Li: the spinel-type material LiMn2O4 and the Nasicon-type one Fe2(MoO4)3. The bismuth, a potential negative electrode material likely to replace the metallic lithium and to undergo the soldering process conventionally used in microelectronics (the solder reflow), has also been studied in this work. Before studying these materials in all-solid-state systems, the first step consists in investigating their electrochemical behaviors in liquid electrolytes. For this purpose, 500 nm-thick thin films are prepared by magnetron sputtering after a step of deposition parameters optimization (power, partial and total pressures in the sputtering chamber, annealing temperature, etc.). Physicochemical proprieties of the deposited thin films are then investigated by XRD, SEM, XPS, RBS and ICP analyses. The analyses of the electrodes by XPS at the end of discharge and charge has allowed better understanding of the electrochemical reactions occurring within the electrode materials and at the electrode/electrolyte interfaces in lithium cells. A comparative study with cycling against sodium has also been carried out in the case of iron molybdate and bismuth materials. This has allowed identifying specific behaviors of the thin films during the insertion/extraction of the two alkalis. The homogeneity of the thin films lithiation/sodiation has also been studied from various XPS analyses realized after etching process which allows eliminating the passivation layer formed at the electrode/electrolyte interface.This study contributes to a better knowledge of three potential electrode materials candidates for lithium micro-batteries and presents very interesting perspectives of materials integration in all solid state systems

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Wang, Danghan. "An EPR and XPS study of transition metal ions doped on wool." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305135.

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Pokorný, David. "Studium morfologie velmi tenkých vrstev XPS analýzou více spektrálních čar jednoho prvku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-402568.

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This diploma thesis deals with methodology of thin film thickness determination using X-ray radiation of silver anode which provides radiation with energy of 2984,3 eV. This energy is twice as high as the standard aluminium radiation which allows a measurement of new photoelectron lines with higher bonding energy and it also provides thanks to the higher photoelectron energy greater information depth. In order to get the right results it was necessary to calibrate the spectrometer Kratos Axis Supra in the silver anode mode first and found out the form of the transmission function. The determination of the thickness of the thin layer was demonstrated by the comparation of the ratio of different photoelectron lines intensities with the theoretical model. For that purpose was specifically used the Si 1s and Si 2p peak bound in the substrate in the Si-Si bonding or in the thin oxid layer in the Si-O bonding. The results show that for thin SiO2/Si film thickness determination is the best to use the intensity ratio of only one photoelectron line. A silver anode however provides greater information depth.

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PISU, MANUELA. "Stability of dental alloys in artificial saliva: an electrochemical and XPS investigation." Doctoral thesis, Università degli Studi di Cagliari, 2014. http://hdl.handle.net/11584/266430.

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Alloys used in dentistry should have good mechanical properties and a very high corrosion resistance in order to be considered biocompatible. The oral cavity is a potentially highly corrosive environment thus stainless steels have been used frequently. Due to allergic reactions of about 10% of the population to nickel ions new nickel-free stainless steels have been developed. In this PhD thesis the Ni-free stainless steel DIN 1.4456 has been studied with electrochemical and XPS surface analytical techniques at 25°C and at 37°C. Surface analysis has shown that the alloy in artificial saliva forms a protective passive film at both temperatures. At 25°C the oxy-hydroxide film formed is enriched in oxidized chromium, after long immersion times (7 days) the nominal composition of oxidized manganese (18%) is found. Molybdenum in the film is slightly enriched. Angular resolved XPS performed on samples exposed at 37°C clearly indicate that the outer part of the passive film is composed essentially of iron oxy-hydroxide whereas chromium oxy-hydroxide is located at the inner part. Experiments with argon ion sputtering confirm that the inner part of the film is enriched in oxidized chromium and manganese whereas oxidized iron is strongly depleted. Both angle-resolved XPS and experiments with argon ion sputtering show that the alloy beneath the passive film is depleted in manganese. The kinetics of initial dissolution and film formation are more rapid at 37°C compared to 25°C but seem to follow the same mechanism. At 37°C the initial corrosion rate is much higher but its decrease with time is more rapid. After 24 h the dissolution rate is already lower then 0.2 μm/year, the steady state dissolution rate will be at least one decade lower. This very low dissolution rate has been confirmed by ICP solution analysis where the metal ion concentration was found to be below the detection limit of the technique for all the alloy elements. Finally a model is proposed that might explain the surface films formed after exposure to artificial saliva solution. During the short initial period with a relatively high corrosion rate iron and especially manganese (non-noble elements) dissolve. Chromium is the film-forming element and an inner chromium oxy-hydroxide film is formed. This film limits progressively the dissolution of the alloy: with time an outer iron oxy-hydroxide film is formed. Due to the dissolution of manganese, the manganese content immediately below the film is strongly depleted. On the contrary, molybdenum is present with about 7%. Such a layered structure of the surface is responsible for the high corrosion resistance and biocompatibility of the DIN 1.4456 stainless steel

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Jiang, Tingming. "Adsorption of chalcogen-based aromatic organic molecules on metal and dielectric surfaces by self-assembly and molecular beam expitaxy." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS581.

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Dans cette thèse, on a étudié la formation de monocouches auto-assemblées de différentes molécules de chalcogénure et de films minces de semiconducteurs organiques. Leurs caractéristiques électroniques et structurelles ont été étudiées principalement par la spectroscopie de photoélectron à rayons X à base de rayonnement synchrotron, la spectroscopie d’adsorption de rayons X à proximité de seuil, la microscopie à force atomique et la diffraction d'électrons à faible énergie. En outre, les caractéristiques d'adsorption du sélénium et du soufre ont été étudiées comme complément à l'étude des adsorptions des molécules comportant des atomes de chalcogène. Le XPS à haute résolution a été utilisé pour enquêter sur les monocouches auto-assemblées de benzèneselénol et de sélénophène sur Cu (111). L'étude détaillée des pics caractéristiques des niveaux du coeur a démontré l'existence de différents sites d'absorption des molécules et aussi avec les mesures NEXAFS l'apparition du clivage de la liaison Se-C. Ces conclusions sont étayées par l'étude de l’adsorption de sélénium atomique montrant également différents sites d'absorption pour le sélénium atomique avec différents environnements chimiques basés sur une étude XPS haute résolution des spectres caractéristiques Se3d, Se3p et l'imagerie LEED. On a étudié les adsorptions de molécules de polythiophène (nT, n = 1-4, 6) ainsi que pour le α, ω-diquaterthiophène (DH4T) et le dihexylsexithiophène (DH6T) sur les films Au (111) et films de Au sur le mica. Les résultats indiquent que les pics XPS S2p ont des contributions de molécules intactes sur différents sites d'adsorption et des molécules cassées. Ces conclusions sont étayées par les calculs DFT existants. La dissociation spontanée apparaît dans une mesure variable dans différents cas, ce qui pourrait être lié à différentes morphologies de surface, à l'existence de défauts et à la réactivité différentes liés a ces défauts. Des films ultra-minces d'α-sexithiophène (6T) ont été déposés sur des surfaces planes de CaF2 (111) / Si (111) et sur des surfaces striées de CaF2 (110) / Si (001) par épitaxie par faisceau moléculaire. L'image AFM de 6T sur CaF2 (111) montre de grandes îles avec des terrasses plates sans préférence dans le plan, tandis que des îlots étroits et allongés suivant l'ondulation du substrat sont formés pour 6T sur CaF2 (110). Les spectres XPS et NEXAFS indiquent que les interactions entre 6T et les surfaces sont négligeables et que les molécules s'alignent avec leur long axe perpendiculaire aux surfaces pour les deux cas
In this thesis, formation of self-assembled monolayers of different chalcogenide molecules and organic semiconductor thin films was investigated. Their electronic and structural characteristics have been investigated primarily by synchrotron based X-ray photoelectron, near edge X-ray absorption fine structure spectroscopy, Atomic force microscopy and low energy electron diffraction. In addition, the adsorption characteristics of selenium and sulfur were studied as a complement to the study of adsorptions of chalcogen headgroup molecules. The high resolution XPS was employed to investigate the self assembled monolayers of benzeneselenol and selenophene on Cu(111). The detailed study of characteristic core level peaks demonstrated the existence of different absorption sites of the molecules and also along with NEXAFS measurements the occurrence of Se-C bond cleavage. These conclusions are supported by the study of atomic selenium adsorptions showing also different absorption sites for the atomic selenium with different chemical environments based on high resolution XPS study of characteristic Se3d, Se3p spectra and LEED imaging. The adsorptions of polythiophene molecules (nT, n=1-4, 6) as well as for α, ω-diquaterthiophene (DH4T) and dihexylsexithiophene (DH6T) on Au(111) and Au films grown on mica was studied. The results indicate that the XPS S2p peaks have contributions from intact molecules on different adsorption sites and broken molecules complemented. These conclusions are supported by existing DFT calculations. Spontaneous dissociation appears to a variable extent in different cases, which could be related to different surface morphologies, existence of defects and ensuing differences reactivity.α-Sexithiophene (6T) ultrathin films were grown on CaF2(111)/Si(111) planar surfaces and on CaF2(110)/Si(001) ridged surfaces by molecular beam epitaxy. The AFM image of 6T on CaF2(111) shows large islands with flat terraces without in-plane preference, while narrow and elongated islands following the substrate corrugation are formed for 6T on CaF2(110). XPS and NEXAFS spectra indicate that the interactions between 6T and surfaces are negligible, and the molecules align with their long axis perpendicular to the surfaces for both cases

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Boucly, Anthony. "Catalytical reactions and environmental chemistry modifications as seen by synchrotron radiation NAP-XPS." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066237/document.

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La NAP-XPS est un nouvel outil révolutionnaire permettant d'utiliser les avantages d'une analyse XPS (Sensibilité aux différents éléments chimiques ainsi que leurs états) à une pression proche de l'ambiante (de l'ordre du mbar) ouvrant ainsi la voie aux études in situ en se rapprochant des conditions réels et. Deux domaines profitent de cette nouvelle machine : la chimie environnementale et la catalyse. Dans le domaine de la chimie environnementale je m'intéresse à l'étude de l'hydratation des argiles dites gonflantes. J'ai ici démontré qu'il est effectivement possible de suivre l'hydratation des contre-ions en mettant en évidence différents comportement en fonction de leurs natures. De plus j'ai pu mettre en évidence un phénomène de radiolyse sous faisceau de la pyridine en présence d'eau dans ces milieux confinés. Concernant la catalyse, j'ai étudié l'oxydation du CO sur des nanocatalyseurs composés notamment de platine un excellent catalyseur, mais sensible aux problèmes d'empoisonnement au CO. Cette réaction est pour nous une réaction prototype permettant de tester le comportement des nanocatalyseurs (Pt, Zn et PtZn). J'ai pu déterminer la température de début de la réaction d'oxidation du CO, de plus en ajoutant du zinc au platine et pour former un nanocatalyseur bimétallique, j'ai démontré qu'on améliore sa résistance à l'oxidation et il montré que le zinc seul est lui aussi capable de catalyser l'oxidation du CO sous forme de création/destruction de carbonate
The NAP-XPS is a revolutionary new tool that makes possible to use the advantages of a standard XPS analysis (sensitivity to the different chemical elements as well as their states) at a near-ambient pressure (mbar range) thus enabling in situ studies closer to real conditions. Two fields fully benefit from this new machine: environmental chemistry and catalysis. In our case for the field of environmental chemistry we are interested in studying the hydration of so-called swelling clays. I have here demonstrated that it is indeed possible to follow the hydration of counter-ions and highlighted different behavior according to their natures. Moreover, I have been able to demonstrate a beam induced pyridine photolysis phenomenon in the presence of water in these confined media. Concerning catalysis, I studied the oxidation of CO on nanocatalysts composed in particular of platinum an excellent catalyst but sensitive to the CO poisoning. This reaction is for us a prototypical reaction to test the behavior of Pt, Zn, PtZn nanocatalysts. Here, I have been able to determine the onset temperature of the CO oxidation reaction. Moreover, by adding zinc to platinum and forming a bimetallic nanocatalyst, I have improved its resistance to oxidation and proved that zinc alone is also capable of catalyzing the oxidation of CO in the form of creation / destruction of carbonate

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Selwyn, John. "A Mass Spectrometry and XPS Investigation of the Catalytic Decompostion of Formic Acid." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/22911.

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This thesis examines the catalytic characteristics of two materials with respect to the decomposition of Formic Acid. The decomposition of formic acid proceeds via two principal reaction pathways: dehydration and dehydrogenation. Dehydrogenation is a valuable reaction producing Hydrogen suitable for use in fuel cells whereas the dehydration pathway produces carbon monoxide, a poison for many fuel cell materials. One of the surface species, the formate ion, is also implicated in other important chemical reactions, most notably the water gas shift and the decomposition of methanol. The author seeks to document various intermediate surface species associated with the two reaction pathways with hope to use this information to future tailoring of catalysts for greater selectivity.

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Segala, Maximiliano. "Calculos de energias de ligação de camada interna pelo uso da teoria do funcional de densidade e suas aplicações." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249741.

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Orientador: Yuji Takahata
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-05T10:46:03Z (GMT). No. of bitstreams: 1 Segala_Maximiliano_D.pdf: 2643298 bytes, checksum: 90403c336f5d4adb79c5c766cea52068 (MD5) Previous issue date: 2005
Doutorado
Físico-Química
Doutor em Ciências

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41

Mueanngern, Yutichai. "Mechanistic Studies of Crotonadehyde Partial Hydrogenation and Ethanol Steam Reforming Reactions on Planar Catalysts—A Gas-Phase and Ambient Pressure XPS Study." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1576076945070127.

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42

Dally, Pia. "Cellules Solaires à base de Matériaux Pérovskites : De la caractérisation des matériaux à l’amélioration des rendements et de la stabilité." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI093.

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Au cours des dernières années, les cellules solaires à base de pérovskites hybrides ont attiré considérablement l’attention. Dès lors, grâce aux travaux de recherche intensifs déployés, les efficacités de ces cellules ont très rapidement évolué pour atteindre récemment un record de 25,2 %. Le caractère hybride (organique et inorganique) confère à cette classe de matériaux des propriétés optoélectroniques intéressantes, telles qu’une forte absorption optique, une grande longueur de diffusion des porteurs de charge ainsi que la facilité de mise en solution et de fabrication à faible coût. Néanmoins, parmi les défis qui restent à relever pour l’industrialisation de cette technologie, le problème de stabilité à long terme est sans doute l’un des principaux. Le but principal de ce travail de thèse est la compréhension et l’amélioration de la stabilité sous illumination des cellules solaires à base de pérovskite et, plus particulièrement, celles avec une architecture dite N-I-P (structure verre/ITO / Couche N / Pérovskite / Couche P/ Electrode d’or) à base de pérovskite CH3NH3PbI3 (MAPI).Au préalable des études de vieillissement, une étude DRX in situ détaillée de l’empilement verre /ITO /SnO2 /MAPI révèle le mécanisme de formation de la MAPI, préparée à partir du PbCl2 et MAI en solution, à partir d’une pérovskite chlorée MAPbCl3 par échange ionique Cl/I.L’étude en température de la MAPI a montré un haut niveau de contraintes présents dans ces couches minces, qui se traduit par un taux élevé de déformation par rapport à la poudre de MAPI.La stabilité sous illumination des dispositifs de ce système de référence a été étudiée et montre une importante perte d’efficacité des cellules complètes. Afin de comprendre l’origine de cette instabilité, une méthode de vieillissement différentiel a été mise au point et consiste à faire vieillir les différentes couches de l’empilement de la cellule séparément pour identifier la couche ou l’interface à l’origine de la dégradation sous illumination. Ces vieillissements ont montré que la raison de dégradation des cellules complètes, sur les longues échelles de temps, est causée par les couches au-dessus de la MAPI (couche P et électrode d’or). L’interface couche N / MAPI a été identifiée comme première cause d’instabilité (les premières centaines d’heures) sous illumination et sa dégradation a été étudiée grâce aux méthodes de caractérisations combinées XPS et ToFSIMS. Finalement, un système optimisé plus performant à base de pérovskite double cations FACsPbIBr a montré une meilleure stabilité sous illumination des cellules complètes
In the past few years, hybrid perovskite solar cells have attracted a considerable amount of research and have undergone rapid development as next generation photovoltaics. The power conversion efficiency has then been rapidly increasing and has recently exceeded 25%. This class of materials has interesting optoelectronic properties such as a high optical absorption, a large diffusion length of the charge carriers as well as a low manufacturing cost. Nevertheless, there are several challenges that need to be addressed before commercialization will be possible, most significantly the long-term stability. In this thesis work, the main goal is to understand and improve the performance and stability under illumination of N-I-P perovskite-based solar cells. A detailed study of the reference system using CH3NH3PbI3 perovskite (MAPI) is presented by studying the formation mechanism of MAPI and its thermal behavior after annealing by XRD techniques. It showed that MAI and PbCl2 precursors initially form a MAPbCl3 layer, which transforms to MAPbI3 in an anion exchange reaction during thermal annealing, inducing a high level of strain in the MAPI layers. Solar cells were aged under continuous illumination (1 sun / 35°C) and showed severe efficiency loss. The origin of devices instability under illumination were investigated in depth thanks to the differential aging. It consists in aging the different layers under illumination before the deposition of top layers in order to determine the key parameter (layer or interface) responsible of this degradation. Results have shown that for long time scales, the upper layers (P-layer and gold electrode are responsible of solar cells degradation, while the N layer / MAPI interface causes degradation at the first hundred hours. To get further insight into the role of ETL / MAPI interface on device behavior; advanced characterization methods, combining XPS and ToFSIMS, were developed and made it possible to study the degradation of the stack glass / ITO / N layer / MAPI, aged under illumination. Improved system with double cations perovskite Cs0.05FA0.95Pb (I 0.83Br0.17)3 have also been studied and show better stability under illumination of complete cells

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PATERA, LAERTE LUIGI. "In situ and in operando study of graphene growth and properties on metal surfaces." Doctoral thesis, Università degli Studi di Trieste, 2016. http://hdl.handle.net/11368/2907990.

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Il grafene, un singolo strato di atomi di carbonio, è stato recentemente proposto come un buon candidato per la tecnologia post-silicio, fornendo una piattaforma che potrebbe consentire di migliorare le prestazioni di dispositivi elettronici, come descritto dalla legge di Moore. La deposizione da vapori chimici (CVD) è un metodo di sintesi adatto per la produzione su larga scala di grafene di alta qualità. Questo processo sfrutta l'attività catalitica delle superfici di metalli di transizione per dissociare molecole di idrocarburi. Tra i possibili catalizzatori, il nichel è particolarmente interessante, a causa del prezzo basso e della possibilità di ottenere strati di grafene a temperature a partire da 400°C. Da un punto di vista di ricerca fondamentale, la crescita di grafene sulla superficie (111) del nichel rappresenta un caso particolare di epitassia, offrendo un buon modello per lo studio degli effetti del substrato sulle proprietà del grafene. In questa tesi, si sono studiati il processo di crescita, la morfologia e le proprietà elettroniche del grafene su Ni(111), mediante microscopia a scansione ad effetto tunnel (STM), spettroscopia di foto-emissione da raggi X (XPS) e tecniche di spettro-microscopia. Inizialmente, le diverse strutture di grafene sono identificate attraverso un approccio combinato sperimentale e teorico, rivelando la coesistenza di tre geometrie di adsorbimento epitassiale e la possibilità di ottenere domini di grafene che presentano una rotazione rispetto al substrato. La mappatura della struttura a banda rivela cambiamenti specifici nelle proprietà elettroniche, a seconda del grado di ibridazione degli orbitali del grafene con il metallo. Sulla base di questi risultati, la crescita grafene è indagata tramite in situ STM e XPS, in modo da chiarire i meccanismi in diverse condizioni sperimentali e valutare il ruolo cruciale svolto dal carburo di superficie e dalla contaminazione di carbonio. In particolare, si è studiata la correlazione tra i parametri di CVD, il processo di crescita e le strutture di grafene finali, fornendo ricette per la sintesi di strati di grafene con morfologie specifiche. La struttura atomica dei bordi delle isole di grafene è studiata, sia durante la crescita, mediante misure STM ad alta velocità, e dopo raffreddamento a temperatura ambiente, mostrando l'importanza della passivazione dei legami dangling. Poi, utilizzando la capacità del nostro sistema STM di acquisire filmati a video-rate, abbiamo identificato i siti attivi per l’attaccamento di carbonio durante la crescita, rivelando il ruolo attivo degli adatomi di nichel. Successivamente, la struttura dei difetti intrinseci è esaminata su scala atomica tramite STM e calcoli ab-initio, mostrando la presenza di adatomi di nichel intrappolati nella matrice di grafene, così come i bordi di grano e le distorsioni reticolari. Infine, sono studiate la crescita e le proprietà elettroniche del grafene bi-strato, rivelando la possibilità di sfruttare l’epitassia tra grafene e Ni (111) per limitare la formazione a solo due strati.
Graphene, a single layer of C atoms, has been recently proposed as a good candidate for post-silicon technology, providing a new platform that could allow improving electronic device performances, as described by the Moore’s Law. Chemical Vapour Deposition (CVD) is a suitable synthesis method for large-scale production of high quality graphene. This process exploits the catalytic activity of transition metal surfaces in dissociating hydrocarbon molecules. Among the possible catalysts, Ni is an appealing choice, due to the low price and the possibility to obtain graphene layers at temperature as low as 400°C. From a more fundamental point of view, graphene growth on the (111) surface of Ni represents a peculiar case of lattice-matched system, being a good model system for the study of the substrate effects on graphene properties. In this thesis, we study the growth process, the morphology and the electronic properties of graphene on Ni(111), by means of Scanning Tunneling Microscopy (STM), X-ray Photo-Emission Spectroscopy (XPS) and spectro-microscopy techniques. First, the different graphene structures are identified through a combined experimental and theoretical approach, revealing the coexistence of three epitaxial adsorption geometries and the possibility to obtain graphene domains that exhibits a rotation respect with the underlying substrate. Band structure mapping reveals specific changes in the electronic properties, depending on the degree of graphene orbital hybridization with the metal. Based on these findings, graphene growth is investigated by in-situ STM and XPS, clarifying the atomistic mechanisms under different experimental conditions and assessing the crucial roles played by surface carbide and C-contamination. In particular, we study the correlation between the CVD parameters, the growth process and the final graphene structures, being able to provide recipes for the synthesis of graphene layers with tailored morphologies. The atomic structure of graphene edges is studied, both during the growth, by means of high-speed STM measurements, and after cooling down to room temperature, addressing the importance of dangling bonds passivation. Then, employing the video-rate capability of our STM system, we identify the active sites for C attachment during growth, revealing the active role of Ni adatoms. Next, intrinsic defective structures are examined at the atomic scale by STM and ab-initio calculations, showing the presence of substitutional Ni adatoms trapped in the graphene matrix, as well as grain boundaries and lattice distortions. Finally, the growth and electronic properties of bi-layer graphene are investigated, revealing the possibility to exploit the lattice match between graphene and Ni(111) to limit the formation to two layers only.

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44

Kotsis, Konstantinos. "Ab-initio-Rechnungen zu O1s-XPS-Spektren von reinen und adsorbatbedeckten ZnO-Oberflächen." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=982351348.

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Lebiedz, Dirk. "Wasserstoffinduzierte Effekte im System Nd2(Fe/Co)14B eine SIMS- und XPS-Studie /." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=967429897.

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Tissot, Héloïse. "Beyond the gap of pressure : XPS studies of interfaces at near ambient pressures." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066615/document.

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Dans de nombreux procédés technologiques, tels que la fabrication de matériaux pour la microélectronique, l’étude des réactions chimiques à une électrode, ou encore la catalyse… L’interface entre la surface d’un solide ou d’un liquide avec un liquide ou une phase gaz joue un rôle fondamental. De façon analogue, les sciences de l’environnement ainsi que celles du vivant intègrent dans leurs modèles la réactivité aux interfaces solide/ liquide ou liquide/ gaz.L’XPS est une technique parfaitement adaptée à l’étude des interfaces et a été largement utilisée pour l’analyse des surfaces de solides. Le principal avantage de l’XPS est sa grande sensibilité aux surfaces. En effet, en raison du faible libre parcours moyen des électrons dans un solide, uniquement les photoélectrons provenant de l’extrême surface (1 – 10 nm) peuvent échapper à celle-ci. Cependant, l’XPS est traditionnellement utilisée dans des conditions d’ultravide (UHV) et cela pour deux raisons. La première est que les analyseurs d’électrons sont construits pour fonctionner en UHV. La seconde est que les électrons doivent pouvoir atteindre l’analyseur, or leur libre parcours moyen est faible dans un gaz à haute pression. Par exemple, à une pression de 1 mbar, des électrons possédant une énergie de 100 eV vont parcourir 1 mm alors qu’ en UHV ils pourront atteindre jusqu’ à 105 m.Dans le but de rendre possible l’utilisation de l’XPS à des pressions plus élevées, quelques groupes autour du monde, dont le groupe de Berkeley (sous la direction de M. Salmeron at de H. Bluhm) et celui du Fritz Haber Institute à Berlin, ont élaborés un équipement permettant d’atteindre des pressions proche de l’ambiant (5 mbar). La construction d’un analyseur d’électron capable de fonctionner à des pressions de l’ordre du mbar, c’est-à-dire à des pressions 7 ordres de grandeur supérieures à l’UHV, a été une avancée à la fois conceptuelle et technologique. Un système de pompage différentiel permet de maintenir l’échantillon dans des conditions dites environnementales tout en maximisant le libre parcours moyen des électrons de façon à ce qu’ils atteignent l’analyseur. De plus, des tensions sont appliquées à des lentilles électrostatiques dans le but d’accélérer et de focaliser ces électrons.Un système similaire (Near Ambient Pressure XPS, NAP-XPS) a été installé sur la ligne TEMPO du synchrotron Soleil en février 2013, le premier temps de faisceau ayant eu lieu au mois de mai suivant. Durant ma thèse, deux projets différents ont été développés, tous les deux liés à l’étude d’interfaces avec l’utilisation de la NAP-XPS.Le premier projet traite des procédés utilisés en micro-electronique pour déposer de fines couches d’oxydes : le dépôt chimique en phase vapeur (CVD) et la déposition de couches atomiques (ALD). En particulier, des molécules de la famille des silanes sont utilisées pour fonctionnaliser des surfaces d’oxyde de silicium ou comme précurseur, combiné à un agent oxydant comme l’eau pour le dépôt de films mince d’oxyde de silicium. Cependant, les mécanismes réactionnels des silanes sur les surfaces de silicium n’ont jamais été étudiés par des techniques telles que la microscopie a effet tunnel (STM) ou l’XPS et l’on sait peu de choses concernant leur mécanisme de dissociation et l’adsorption des divers fragments sur la surface
In many processes or technological objects, such as coating deposition, advanced material processing for electronics, magnetic or optical devices, electrochemical processes at an electrode, sensors and catalysis, etc. the interface between a surface of a solid and a liquid or a gas phase, plays a prominent role. Analogously, environmental sciences and sciences of the Living integrate into their models chemical reactions taking place at solid/liquid or liquid/gas interfaces.XPS is a powerful technique for interface analysis and has been widely use in the case of solid surface. The main advantage of XPS is its sensitivity to the material surface. Indeed, due to the low electron mean free path of electrons in a solid, only the photoelectrons at the extreme outer surface (1-10 nm) can escape the sample. However, XPS has traditionally been conducted under ultra-high vacuum (UHV) conditions. UHV conditions are utilized for two reasons. First, the analyzers are designed to work under UHV conditions. Second, the electrons must reach the detector and their mean free path is short at high pressures. For example at a pressure of 1 mbar, 100 eV electrons will travel 1 mm while under UHV conditions, the mean free path increases to 105 m. UHV chambers (10-10 mbar) help maximize the mean free path so that a high number of electrons will reach the detector/analyzer and the signal/noise ratio will increase making it possible to analyze the spectrum produced. This constraint makes UHV the standard environment of X-ray Photoelectron Spectroscopy (XPS) experiments.In order to make possible the use of XPS on a larger pressure range, a few groups around the world have designed photoemission equipment that can be operated under ambient pressure (up to 5 mbar). The Berkeley group (M. Salmeron LBNL-Materials Sciences Division, H. Bluhm LBNL-Chemical Sciences Division), who pioneered this field, has two such setups installed at the Advanced Light Source. The Fritz Haber Institute has built a high pressure XPS based on the Berkeley prototype, installed at BESSY synchrotron (Berlin), since 2002. The building of Ambient Pressure XPS (APXPS) analyzers of the Berkeley type, able to be operated at pressures in the range of 1 mbar, about 7 orders of magnitude higher than the pressure limit of conventional UHV equipment is both a technological and conceptual breakthrough. Differential pumping stages allow the sample to remain at environmental pressures, while maximizing the mean free path of emitted electrons, so they can reach the detector. Additionally, voltages are applied to electrostatic lenses in the unit to accelerate and focus the electrons onto the focal plane of the electron energy analyzer. A similar system Near-Ambient Pressure XPS, NAP-XPS), described in details in chapter 1, was delivered in December 2012 and installed at TEMPO beamline in February 2013. The first beamtime occurred in May 2013. During my thesis that started in October 2011 two different projects were developed, both related to interface analysis using the NAP-XPS instrument

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Leroy, Stéphane. "Etude d'interfaces électrode/électrolyte dans les batteries Li-ionApproche par XPS et AFM." Pau, 2006. http://www.theses.fr/2006PAUU3033.

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Les accumulateurs lithium-ion sont aujourd'hui la principale source d'énergie de l'électronique portable (téléphones, ordinateurs,. . . ). Leur capacité (quantité d'électricité pouvant être fournie) est gouvernée par la structure électronique et cristallographique des matériaux d'électrode, alors que leur tenue en cyclage et leur durée de vie sont fortement liées à l'interface électrode/électrolyte. Dans ce travail de thèse, nous avons entrepris l'étude approfondie de couches interfaciales à l'aide de techniques d'analyse de surface adaptées permettant l'obtention d'informations chimiques et morphologiques : la spectroscopie photoélectronique à rayonnements X (XPS) et la microscopie à force atomique (AFM). Une part importante du travail a été consacrée à l'étude des couches formées au niveau du matériau d'électrode négative (graphite) d'une batterie lithium-ion commerciale : LiCoO2 // EC/DMC/DEC (2/2/1) ; LiPF6 (1mol. L-1) // graphite. Des approches originales d'analyse ont été mises en œuvre : 1) Etude approfondie de composés de référence ; différents produits de dégradation du solvant et du sel de l'électrolyte ont été caractérisés de façon approfondie par XPS. 2) Etude du processus de formation de la couche par le biais d'analyses systématiques XPS et AFM à différents états de charge par un suivi pas à pas. 3) L'influence de la nature de l'électrolyte a également été examinée. Nous avons ensuite abordé l'étude des couches interfaciales formées au niveau de l'électrode positive (LiCoO2) de la batterie Li-ion commerciale. Une extension du travail à d'autres matériaux prometteurs d'électrode négative (Cu6Sn5, CoSn2) a également été entreprise
The lithium-ion batteries are today the principal source of energy of portable electronics (telephones, computers. . . ). Their capacity (quantity of electricity being able to be provided) is controlled by the electronic and crystallographic structure materials of electrode, whereas their behaviour in cycling and their lifespan are strongly related to the interface électrode/électrolyte. In this work of thesis, we undertook the thorough study of interfacial layers using adapted techniques of analysis of surface allowing obtaining chemical and morphological information : the X-ray photoelectronic spectroscopy (XPS) and atomic force microscopy (AFM). A significant share of work was devoted to the study of the layers formed on the level of material of negative electrode (graphite) of a commercial lithium-ion battery : LiCoO2// EC/DMC/DEC (2/2/1); LiPF6 (1mol. L-1)// graphite. Original approaches of analysis were implemented : 1) Thorough study of reference's composed; various breakdown products of solvent and the salt of the electrolyte were characterized thoroughly by XPS. 2) Study of the process of formation of the layer by the means of systematic analyses XPS and AFM in various states of load by a follow-up step by step. 3) The influence of the electrolyte's nature was also examined. We then approached the study of the interfacial layers formed on the level of the positive electrode (LiCoO2) of the commercial battery Li-ion. An extension of work to other promising materials of negative electrode (Cu6Sn5, CoSn2) was also undertaken

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Choudhury, Tanima. "An XPS study of the effect of ion bombardment on transition metal oxides." Thesis, Aston University, 1991. http://publications.aston.ac.uk/25142/.

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Jackman, Mark. "The functionalisation and defects of titania : a photoemission study." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-functionalisation-and-defects-of-titania-a-photoemission-study(d199335c-cb3d-4f08-964f-d84541a464cc).html.

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This thesis consists of photoemission studies of the rutile and anatase polymorphs of TiO2. It is split into two sections. In the first part, studies of the functionalisation of the rutile TiO2 (110) and the anatase TiO2 (101) surfaces with small organic molecules are presented. In the second part, studies of defects at the anatase TiO2 (101) surface are presented. Four organic molecules are investigated, p-aminobenzoic acid (pABA) and 3-fluoroaniline (3-FA) on anatase TiO2 (101), and dopamine and malonic acid (MA) on rutile TiO2 (110). The four adsorbates studied all have potential as dyes for dye-sensitised solar cells (DSSCS), and dopamine and pABA have the potential to be used as linkers for light sensitisers for photocatalytic applications such as DSSCs. Near-edge X-ray fine structure (NEXAFS) spectroscopy was used to determine the orientation of the molecules on the surface, and X-ray photoemission (XPS) spectroscopy was used to determine the chemical environment of the molecule on the surface. On the anatase TiO2 (101) surface, for pABA, the plane of the ring sits upright, normal to the surface, bonding through the carboxylic acid group after deprotonation. 3-FA also bonds upright, normal to the surface. It bonds through the amine group to the surface. It is unclear whether the molecule bonds dissociatively (the amine group deprotonating). On the rutile TiO2 (110) surface, dopamine is found to sit just off normal at ~ 78 º. It bonds through the catechol moiety after dissociation of the hydrogens. Both of the MA carboxylic acid protons dissociate and both moieties bond to the surface. MA is unstable under irradiation from insertion device beamlines. The defects in the anatase TiO2 (101) surface layers are investigated by XPS. Defects in the form of oxygen vacancies are observed in the band gap region of the photoelectron spectrum at around 1 eV binding energy (BE). Understanding the nature of these defects, intrinsic dopants in n-type TiO2 is imperative for photocatalytic applications. The effect of water adsorption on the stoichiometric and Ar cluster-ion-source-sputtered anatase TiO2 (101) surface is investigated at near-ambient pressures (NAP) and high vacuum. High vacuum studies show the anatase surface oxygen vacancies migrate to the subsurface region over time, as has been postulated with scanning tunnelling microscopy and density functional theory analysis. NAP-XPS is a developing technology allowing the analysis of surfaces and interfaces in "real-life" conditions. Results show water adsorbs in a similar fashion on both surfaces and reaches a saturation point between 0.6 and 1.8 mbar at room temperature, meaning there is little difference in reactivity between the stoichiometric and reduced surfaces. Oxygen vacancies are created at the TiO2 surface by insertion-device synchrotron radiation beamlines and the creation of these defects is monitored in situ with XPS. The bandgap state is made up of three components, relating to oxygen vacancies at 1.0 eV BE and two related components at 0.2 and 1.7 eV BE that are due to a surface 2D electron gas, created by electron doping via Nb impurities and synchrotron radiation-induced oxygen vacancies.

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Eglizaud, Noëlle. "Rétention et réduction de l'uranium à la surface de la pyrite." Paris 11, 2006. http://www.theses.fr/2006PA112230.

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Dans l’hypothèse d’un stockage du combustible usé en formation géologique profonde il est important d’évaluer la dispersion de l’uranium dans l’environnement. La pyrite est un minéral réducteur présent dans les argilites du Callovo-Oxfordien, formation actuellement à l’étude pour un tel stockage. Pourtant, l’impact de la pyrite sur la migration de l’uranium n’a été que peu étudié. Le but de la thèse était donc de comprendre les mécanismes de rétention et réduction de l’uranium (VI) à la surface de la pyrite (FeS2). Pour cela, les analyses chimiques des solutions ont été couplées aux études spectroscopiques de la surface (par XPS et Spectroscopie Raman essentiellement) et les études d’interaction ont été réalisées sous atmosphère anoxique en boîte à gants. La dissolution de la pyrite en suspension sous anoxie conduit à la libération de sulfoxyanions et de fer (II) qui est alors adsorbé à la surface de la pyrite. Cette adsorption a été confirmée par des études de dilution isotopique. L’uranium (VI) se fixe par une réaction d’échange avec le fer (II) adsorbé à la surface sur les sites soufrés de la pyrite, cette adsorption étant maximale au-delà de pH 5,5. Le cobalt (II) et l’europium (III) s’adsorbent également à la surface de la pyrite au-delà de pH 5,5, confirmant ainsi que la rétention sur la surface de la pyrite ne résulte pas nécessairement d’une réaction d’oxydoréduction. Lorsque la concentration en uranium retenu est inférieure à 4. 10-9 mol. G-1, une réaction d’oxydoréduction à la surface de la pyrite conduit à la formation d’un oxyde mixte d’uranium (VI) - (IV) solide ainsi que de soufre (d. O. > -I) solide, le fer restant au degré d’oxydation +II tout au long du processus. La formation des produits de réaction semble passiver la surface puisque lorsque la concentration en uranium retenu augmente, la réaction d’oxydoréduction n’est plus observée. La surface est saturée pour une concentration en uranium adsorbé de (3,4 ± 0,8). 10-7 mol. L-1. La constante d’adsorption est déterminée grâce à une modélisation de type Langmuir pour les concentrations en uranium retenu supérieures à 4. 10-9 mol. G-1. Elle est égale à 8. 107 L. Mol-1. Enfin, la présence d’uranium (VI) en grand excès devant la concentration de saturation permet d’observer une réaction d’oxydoréduction entre l’uranium (VI) non adsorbé et le fer (II) libéré par la dissolution de la pyrite. Les produits de cette réaction sont de l’uranium réduit en un oxyde mixte du type U4O9(s) et des (hydr)oxydes de fer (III) telle que la maghémite g-Fe2O3 (s), l’uranium (VI) pouvant alors être adsorbé sur cette phase néoformée
In the hypothesis of a storage of the spent fuel in a deep geological formation, understanding the uranium dispersion in the environment is important. Pyrite is a reducing mineral present in the Callovo-Oxfordian argilites, the geological formation actually studied for such a storage. However, pyrite impact on uranium migration has already been poorly studied. The aim of the study was to understand the mechanisms of uranium(VI) retention and reduction on the pyrite surface (FeS2). Solution chemistry was therefore coupled with solid spectroscopic studies (XPS and Raman spectroscopy). All uranium-pyrite interactions experiments were performed under an anoxic atmosphere, in a glove box. Pyrite dissolution under anoxic conditions releases sulphoxyanions and iron(II), which can then be adsorbed on the pyrite surface. This adsorption was confirmed by interaction experiments using iron(II) isotopic dilution. Uranium (VI) is retained by an exchange reaction with iron(II) adsorbed on sulphur sites, with a maximal amount of sorbed uranium at pH ≥ 5. 5. Cobalt(II) and europium(III) are also adsorbed on the pyrite surface above pH 5. 5 confirming then that reduction is not required for species to adsorb on pyrite. When the concentration of uranium retained is lower than 4x10-9 mol g-1, an oxidation-reduction reaction leads to the formation of a uranium (VI) – (IV) mixed oxide and to solid sulphur (d. O. > -I). During this reaction, iron remains mostly at the +II oxidation degree. The reaction products seem to passivate the pyrite surface: at higher amounts of retained uranium, the oxidation-reduction reaction is no longer observed. The surface is saturated by the retention of (3. 4 ± 0. 8)x10-7 mol L-1 of uranium(VI). Modelling of uranium sorption at high surface coverage (≥ 4x10-9 mol g-1) by the Langmuir model yields an adsorption constant of 8x107 L mol-1. Finally, a great excess of uranium(VI) above the saturation concentration allows the observation of an oxidation-reduction reaction between unadsorbed uranium(VI) and iron(II), coming from pyrite dissolution. The reaction products are then reduced uranium, such as U4O9(s), and iron(III) (hydr)oxides, such as maghemite g-Fe2O3 (s), the remaining uranium(VI) in the supernatant being possibly adsorbed on this new formed phase

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