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1
Droschke, Sonja. « X-Ray Photoemission Spectroscopy Characterization of Fe(II)- and Fe(III)-Phthalocyanine Molecular Films ». Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-257183.
Texte intégralRésumé :
This thesis investigates the electronic structure of iron phthalocyanine (Fe(II)Pc) andiron phthalocyanine chloride (Fe(III)PcCl) immobilized on surfaces. For this purposetwo different deposition methods are used and compared: smearing the molecularpowder under atmosphere condition and evaporation of a molecular layer inultra-high vacuum. The electronic states of FePc and FePcCl are probed withphotoelectron spectroscopy (PES) and compared in relation to the ionic state of thecentral metal (Fe). The PE spectra show that evaporation of FePcCl at around 350°Cresults in dissociation of the chlorine from the FePc molecule, which is stable at thistemperature. Mass spectroscopic measurements during heating of FePcCl in ultra-highvacuum (UHV) show a clear Cl signal for temperature still below 250°C. Theoreticalcalculations of the binding energy for Cl in FePcCl seem to indicate dissociation of theCl from the molecules.
2
Doran, Brian. « Preparation and characterization of Ribonucleic acid (RNA)/inorganic materials interfaces using photoemission spectroscopy ». [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000385.
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Zborowski, Charlotte. « Characterization of deeply buried interfaces by Hard X-ray Photoelectron Spectroscopy ». Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC025/document.
Texte intégralRésumé :
Cette thèse vise à améliorer la méthode d'analyse du fond continu inélastique afin de l'appliquer à des cas qui présentent un intérêt technologique. En effet, ces améliorations sont cruciales car elles portent sur des critères de précision et de gain de temps, plus particulièrement pour l’étude de dispositifs présentant plusieurs couches profondément enterrées de matériaux bien distincts. Ainsi, l'analyse du fond continu inélastique associée à la spectroscopie de photoélectrons à rayons X durs (HAXPES) présente un grand intérêt car l’HAXPES permet de sonder plus profondément dans un échantillon qu'avec la spectroscopie de photoélectrons à rayons X classique (XPS). Ce présent travail porte sur des échantillons technologiquement pertinents, principalement des transistors à haute mobilité d'électrons (HEMTs), à certaines étapes cruciales de leur processus de fabrication, tels que des recuits. Il est donc très important que ces analyses soient effectuées de manière non destructive afin de préserver les interfaces enterrées. Ce sont souvent l'emplacement de phénomènes complexes qui sont critiques pour les performances du dispositif et une meilleure compréhension est une condition préalable à l’amélioration des dispositifs. Dans ce travail, les phénomènes de diffusion en profondeur sont étudiés grâce à l’analyse du fond continu inélastique associée à l’HAXPES (en utilisant le logiciel QUASES) pour des profondeurs allant jusqu'à 60 nm. Les résultats de distribution en profondeur présentent des écarts par rapport aux mesures TEM inférieures à 5%. Le choix des paramètres d'entrée de la méthode est discuté pour une large gamme d'échantillons et des règles simples en sont issues qui rendent l'analyse réelle plus facile et plus rapide à effectuer. Enfin, il a été montré que la spectromicroscopie faite avec la technique HAXPEEM peut fournir des spectres à chaque pixel utilisables pour l’analyse du fond continu inélastique. Cela peut fournir une cartographie 3D de la distribution en profondeur des éléments de manière non-destructiveThis thesis aims at improving the inelastic background analysis method in order to apply it to technologically relevant samples. Actually, these improvements are utterly needed as they concern criteria of accuracy and time saving particularly for analysis of devices presenting deeply buried layers with different materials. For this purpose, the interest of the inelastic background analysis method is at its best when combined with hard X-ray photoelectron spectroscopy (HAXPES) because HAXPES allows to probe deeper in the sample than with conventional X-ray photoelectron spectroscopy (XPS). The present work deals with technologically relevant samples, mainly the high-electron mobility transistor (HEMT), at some crucial steps of their fabrication process as annealing. Actually, it is very important that these analyses shall be performed non-destructively in order to preserve the buried interfaces. These are often the location of complex phenomena that are critical for device performances and a better understanding is often a prerequisite for any improvement. In this thesis, the in-depth diffusion phenomena are studied with the inelastic background analysis technique (using the QUASES software) combined with HAXPES for depth up to 60 nm. The depth distribution results are determined with deviations from TEM measurements smaller than a typical value of 5%. The choice of the input parameters of the method is discussed over a large range of samples and simple rules are derived which make the actual analysis easier and faster to perform. Finally, it was shown that spectromicroscopy obtained with the HAXPEEM technique can provide spectra at each pixel usable for inelastic background analysis. This is a proof of principle that it can provide a 3D mapping of the elemental depth distribution with a nondestructive method
Denne afhandling har til formål at forbedre den uelastiske baggrundsanalysemetode til anvendelser i den til teknologiske industri. Faktisk er disse forbedringer absolut nødvendige, for at opnå nøjagtighed og tidsbesparelse, især for analyse af prøver med dybt begravede lag af forskellige materialer. Til det formål er interessen for den uelastiske baggrundsanalysemetode bedst i kombination med hård røntgenfotoelektron-spektroskopi (HAXPES), fordi HAXPES gør det muligt at probe dybere i prøven end med konventionel røntgenfotoelektron-spektroskopi (XPS). Dette arbejde beskæftiger sig med teknologisk relevante prøver, hovedsagelig høj-elektron mobilitetstransistor (HEMT), på nogle afgørende trin i deres fremstillingsproces som fx annealing. Faktisk er det meget vigtigt, at disse analyser udføres på en ikke-destruktiv måde for at bevare de begravede grænseflader. Det er ofte her de komplekse fysiske fænomener opstår, som er kritiske for fuktionaliteten, og en bedre forståelse af grænsefladerne er ofte en forudsætning for at kunne forbedre denne. I denne afhandling studeres de dybdegående diffusionsfænomener med den uelastiske baggrundsanalyse teknik (ved hjælp af QUASES software) kombineret med HAXPES for dybder op til 60 nm. Dybdestributionsresultaterne har afvigelser fra TEM-målinger mindre end en typisk værdi på 5%. Valget af input parametre for metoden er diskuteret på bagground af et stort udvalg af prøver samt omfattende simuleringer og enkle regler er udledt, hvilket gør den praktiske analyse nemmere og hurtigere at udføre. Endelig blev det vist, at spektromikroskopi opnået med HAXPEEM-teknikken kan tilvejebringe spektre ved hver enkelt pixel som kan anvendes til uelastisk baggrundsanalyse. Dette viser at i princippet kan en 3D-billeddannelse af den elementære dybdefordeling bestemmes ikke destruktivt
4
DRERA, GIOVANNI. « ELECTRONIC STRUCTURE OF TIO2 THIN FILMS AND LAALO3-SRTIO3 HETEROSTRUCTURES : THE ROLE OF TITANIUM 3D1 STATES IN MAGNETIC AND TRANSPORT PROPERTIES ». Doctoral thesis, Università degli Studi di Milano, 2012. http://hdl.handle.net/2434/168728.
Texte intégralRésumé :
The scope of this Thesis is the study of the electronic structure of two Ti-based oxide systems, TiO2 thin films and the ultra-thin LaAlO3-SrTiO3 (LAO-STO) heterojunctions, which display remarkable physical phenomena, so far not completely understood. In both cases, the titanium-related electronic states are expected to play a fundamental role and thus have been probed by means of X-ray photoemission spectroscopies.
A weak room-temperature ferromagnetism (FM) has been recently detected in slightly reduced TiO2 thin film and in other oxides, such as HfO2 and CaO; since these materials are insulating closed-shell systems, this phenomenon has been classified as "d0 magnetism". Magnetism in these compounds seems to be related to the growth methodology and ultimately to the presence of structural defects, such as oxygen vacancies. Therefore, a thorough analysis of titanium electronic states, and especially of the defect-related Ti3+ energy levels, is needed in order to understand the origin of magnetic interactions.
In the first part of this Thesis, a comprehensive magnetic characterization of a set of TiO2 samples is given, together with the analysis of Ti 3d-related states carried out with X-ray photoemission (XPS) and resonant photoemission (ResPES). A set of N-doped TiO2 thin films have also been grown, in order to verify the effect of doping on the TiO2 magnetism. The hypothesis of a clustered oxygen-vacancies origin of FM is then discussed in the light of the experimental and theoretical results.
Another interesting oxide system in which the stoichiometry of Ti ions play a fundamental role is the LAO-STO interface. LAO and STO, separately, are two band insulators, with an empty shell electronic structure (3d0 for STO, 4f0 for LAO) and a similar perovskite structure; however, the interface created by growing LAO on the top of STO (001) has found to become metallic, hosting a 2D electron gas. This heterostructure becomes conductive only when the STO is terminated with a TiO2 layer; therefore, the Ti-related electronic states are expected to host the metallic states.
The second part of this Thesis is devoted to the study of conductive and insulating LAO-STO interfaces, carried out by XPS, X-ray absorption (XAS) and with ResPES techniques. The stoichiometry of each atomic species has been evaluated through a comparison with LAO and STO single crystals. A resonance enhancement of the conductive Ti states, associated to a small fraction of Ti3+ ions is reported and compared to theoretical calculations. On the basis of these results, the origin of metallic states in ultra-thin LAO-STO interfaces is properly addressed. In addition, a characterization of the intermixing and the disorder at the LAO-STO interface has been done through angle-resolved XPS, providing important information on the intermixing of light cations (Al, Ti) otherwise missed by X-ray diffraction techniques.
5
Caro, Anne-Sophie. « Fonctionnalisation de surfaces d'acier inoxydable afin d'inhiber les premières étapes de formation d'un biofilm ». Paris 6, 2008. http://www.theses.fr/2008PA066560.
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Foster, Geoffrey M. « DEFECT AND METAL OXIDE CONTROL OF SCHOTTKY BARRIERS AND CHARGE TRANSPORT AT ZINC OXIDE INTERFACES ». The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524050368601169.
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Venturini, Federica. « Soft X-ray photoemission spectroscopy ». Université Joseph Fourier (Grenoble), 2005. http://www.theses.fr/2005GRE10175.
Texte intégralRésumé :
La motivation principale de cette thèse a été de déterminer les avantages et les inconvénients de l'utilisation de la spectroscopie de photoémission résolue en angle dans le domaine des rayons X mous. L'étude d'un système bien connu, Ag(001) nous permet de discuter plusieurs questions telles que le rôle de la quantité de mouvement du photon, la pertinence de l'approximation d'électron libre à l'état final, et le rôle des phonons. La polarisation de la lumière incidente a aussi été exploitée. En choisissant un tel système, nous avons aussi voulu comparer les résultats expérimentaux avec des spectres calculés de photoémission résolue en angle dans cette gamme d'énergie. Le comportement à basse température atypique des composés de Cérium est généralement imputé à l'effet Kondo. Des résultats originaux ont été obtenus en étudiant la bande de valence de trois composés monocristallins iso-structuraux de Cérium, CeCu2Ge2, CeNi2Ge2 et CeC02Ge2. La position du seuil d'absorption M5 du Cérium dans la bande d'énergie des rayons X mous est exploitée pour isoler la contribution 4f à ces spectres. De plus, l'utilisation de photons incidents d'énergie relativement élevée permet de minimiser les effets de surface. Les spectres de photoémission présentés dam cette thèse incluent des études de dépendance en température, des spectres à la résonance, des spectres résolus en angle ou bien intégrés angulairement. Les premiers sont en accord avec le modèle d'impureté unique d'Anderson, alors que les derniers suggèrent qu'il est important de prendre en compte le réseau cristallinThe main motivation behind this thesis has been to determine both the advantages and the disadvantages ofthe soft X-ray application of angle-resolved photoemission spectroscopy. The investigation of a weil known system, Ag(001), enables us to discuss several questions such as the role of the photon momentum, the applicability ofthe fiee-electron-like final state approximation and the role ofphonons. The polarisation of the incoming light has also been exploited. The choice of such a system also cornes from our des ire to compare the results with calculations of angle-resolved photoemission spectra in this energy range. The anomalous low temperature properties of Ce-based compounds are generally related to the Kondo effect. Original results have been obtained by investigating the valence band of three iso-structural single crystalline Ce compounds, CeCu2Ge2, CeNi2Ge2 and CeC02Ge2. The location of the Ce M5 absorption edge within the soft X-ray energy range is exploited in order to isolate the 4f contribution to the spectra. Added to this, the use of relatively high incoming photon energies allows minimising the surface contribution. Temperature dependent, resonant, angle-resolved and angle-integrated photoemission measurements have been performed. The former are in qualitative agreement with the single impurity Anderson model, whereas the latter suggest the importance of taking the lattice into account
8
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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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.
Texte intégralRésumé :
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 inhabituellesThis 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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Doutt, Daniel R. « THE ROLE OF NATIVE POINT DEFECTS AND SURFACE CHEMICAL REACTIONS IN THE FORMATION OF SCHOTTKY BARRIERS AND HIGH N-TYPE DOPING IN ZINC OXIDE ». The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366199639.
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Jabeen, Fauzia. « III-V semiconducting nanowires by molecular beam epitaxy ». Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3097.
Texte intégralRésumé :
2007/2008This thesis is devoted to the study of the growth of III-V nanowires (NWs) by catalyst assisted and catalyst free molecular beam epitaxy (MBE). The nanostructures have been routinely characterized by scanning electron microscopy (SEM) and, to a minor extent by transmission electron microscopy (TEM). X-ray photoemission spectroscopy (XPS), scanning photoemission microscopy (SPEM), extended X-ray absrorption fi ne structure analysis (EXAFS), photoluminescence (PL) and trans- port measurements have given an important contribution on specifi c topics. The first section of this thesis reports on GaAs, InAs, and InGaAs NWs growth by Au assisted MBE. A substrate treatment is proposed that improves uniformity in the NWS morphology. Thanks to a careful statistical analysis of the NWs shape and dimensions as a function of growth temperature and duration, evidence is found of radial growth of the NWs taking place together with the axial growth at the tip. This eff ect is interpreted in term of temperature dependent diff usion length of the cations on the NWs lateral surface. The control of the NWs radial growth allowed to grow core shell InGaAs/GaAs NWs, displaying superior optical quality. A new procedure is proposed to protect NWs surface from air exposure. This procedure allowed to perform ex-situ SPEM studies of electronic properties of the NWs. The second part of this thesis is devoted to Au-free NWs growth. GaAs and InAs NWs were successfully grown for the first time using Mn as catalyst. Incorporation of Mn in the NW is studied using EXAFS technique. It is shown that Mn atoms are incorporated in the body of GaAs NWs. Use of low growth temperature is suggested in order to improve the Mn incorporation inside GaAs NWs and obtain NWs with magnetic properties. Finally, growth of GaAs and InAs NWs on cleaved Si subtrate is demonstrated without the use of any outside metal catalyst. Two kinds of nanowires have been obtained. The experimental findings suggest that the two types of nanowires grow after di fferent growth processes.
Questa tesi e' dedicata allo studio della crescita di nanofili di semiconduttori III- V tramite epitassia da fasci molecolari (MBE) assistita da catalizzatore e senza l'uso di catalizzatori. Le nanostrutture sono state caratterizzate sistematicamente tramite microscopia elettronica a scansione (SEM), e in maniera minore microscopia elettronica in trasmissione (TEM). Altre tecniche come la spettroscopia di fotoemissione da raggi x (XPS), la microscopia da fotoemissione in scansione (SPEM), la spettroscopia di assorbimento x (in particolare la extended X-ray absorpition fine structure analysis (EXAFS)) la fotoluminescenza (PL), e il trasporto elettrico hanno dato importanti contributi su problematiche specifiche. La prima parte di questa tesi riguarda la crescita di nanofili di GaAs, InAs e InGaAs tramite MBE assistita da oro. Viene proposto un trattamento del substrato che migliora nettamente l'omogeneita' morfologica dei nanofili. Grazie ad un'attenta analisi statistica della forma e delle dimensioni dei nanofili in funzione della temperatura e del tempo di crescita e' stata dimostrata la crescita radiale dei nanofili, che avviene insieme alla crescita assiale che ha luogo alla punta del nanofilo. Le osservazioni sperimentali sono state interpretate in termini di dipendenza dalla temperatura della lunghezza di diffusione dei cationi sulle super ci laterali dei nanofili. Il controllo della crescita radiale ha permesso di crescere nanofili di InGaAs/GaAs core shell, costituiti cioe' da una anima centrale di InGaAs (core) e uno strato esterno di GaAs (shell) , che hanno dimostrato eccellente qualita' ottica. Viene quindi proposta una nuova procedura per proteggere la super ficie dei nanofili durante l'esposizione all'aria. Grazie a questa e' stato possibile realizzare ex-situ uno studio SPEM delle proprieta' elettroniche dei nanofili. La seconda parte della tesi riguarda la crescita di nanofili senza l'uso di oro. Viene per la prima volta dimostrata la possibilita' di crescere nanofili di GaAs e InAs usando il manganese come catalizzatore. L'incorporazione del Mn come impurezza nei nanofili e' stata studiata tramite EXAFS. Le misure hanno dimostrato che atomi di Mn sono effettivamente incorporate nel corpo dei nano fili. La crescita delle nanostrutture a temperatura piu' bassa potrebbe migliorare qualitativamente l'incorporazione del Mn e permettere la crescita di nanofili con proprieta' magnetiche. Viene in fine dimostrata la crescita di nanofili di GaAs e di InAs senza l'utilizzo di materiali diversi da quelli costituenti il semiconduttore. Tale risultato e' ottenuto su superfici sfaldate di silicio. Sono state osservate nanostrutture di due tipi, che sulla base dei dati sperimentali sembrano essere dovuti a due diversi meccanismi di crescita.
XXI Ciclo
1977
12
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.
Texte intégralRésumé :
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.
13
Magnuson, Martin. « Electronic structure studies using resonant X-ray and photoemission spectroscopy ». Doctoral thesis, Uppsala universitet, Fysiska institutionen, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-973.
Texte intégralRésumé :
This thesis addresses the electronic structure of molecules and solids using resonant X-ray emission and photoemission spectroscopy. The use of monochromatic synchrotron radiation and the improved performance of the instrumentation have opened up the possibility of detailed analyses of the response of the electronic systems under interaction with X-rays. The experimental studies are accompanied by numerical ab initio calculations in the formalism of resonant inelastic scattering. The energy selectivity has made it possible for the first time to study how the chemical bonds in a molecule break up during resonant inelastic X-ray scattering. In the conjugated polymer systems, the element selectivity of the X-ray emission process made it possible to probe the different atomic elements separately. The X-ray emission technique proved to be useful for extracting isomeric information, and for measuring the change in the valence levels at different degrees of doping. In this thesis, spectral satellite features in transition metals were thoroughly investigated for various excitation energies around a core-level threshold. By measuring the relative spectral intensity of the satellites it was possible to extract information on the partial core-level widths. Using the nickel metal system as an example, it was shown that it is possible to probe the different core-excited states close toshake-up thresholds by measuring the relative spectral intensity variation of the Auger emission.Resonant photoemission measurements showed unambiguous evidence of interference effects. Theseeffects were also thoroughly probed using angle-dependent measurements. The combination of X-rayemission and absorption were useful for studying buried layers and interfaces due to the appreciable penetration depth of soft X-rays. X-ray scattering was further found to be useful for studying low-energy excited states of rare earth metallic compounds and transition metal oxides.
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Haidu, Francisc. « Tailoring the Electronic and Optical Properties of Molecular Thin Films by Reducing and Oxidising Agents ». Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-159012.
Texte intégralRésumé :
Heutzutage wächst die Nachfrage nach neuartigen Geräten, die teilweise (hybrid) oder völlig aus organischen halbleitenden Materialien hergestellt sind. Der Grund dafür sind die geringen Herstellungskosten sowie die hohe Flexibilität im Moleküldesign und damit einstellbare optische, elektronische und Spintronik-Eigenschaften. Bisher sind mit großem Erfolg organische Leuchtdioden (OLED), organische Solarzellen und gedruckte organische Elektronik-Bauelemente hergestellt worden. Auf Grund ihrer langen Spin-Lebensdauer sind Moleküle auch für Spintronik-Anwendungen sehr geeignet.
In dieser Arbeit wurden die elektronischen und optischen Eigenschaften von vier ausgewählten Molekülen analysiert. Davon wurden Kupfer- und Mangan-Phthalocyanin (CuPc und MnPc) für die Untersuchung der Anordnung des Energieniveaus an der Metall-Organischen Halbleitern (M-O) Grenzfläche verwendet. Außerdem werden die andere zwei Moleküle tris(8-hydroxy-quinolinato) Aluminium(III) (Alq3) und N,N’-diphenyl-N,N’-bis(1-naphthyl)-1,1’-biphenyl-4,4’-diamine (α-NPD) häufig in OLED-Strukturen als Elektron- beziehungsweise Loch-Leiter verwendet. Die Proben sind mittels organischer Molekularstrahl-Abscheidung (OMBD) auf Co (oder Au) Folien beziehungsweise auf einseitig poliertem Si(111) Einkristall hergestellt worden.
Im ersten Teil der Arbeit wurde die Entwicklung der Grenzfläche zwischen CuPc und Co (oder Au) Substrat mittels Valenzband- und Inverser Photoelektronen-spektroskopie (VB-PES und IPES) analysiert und herausgefunden, dass ein „Öffnung“ der Bandlücke mit dem Wachstum der Molekularschicht erfolgt. Ähnliches findet bei die MnPc/Co-Grenzfläche statt. Diese Erkenntnisse sind sehr wichtig für die Entwicklung von zukünftigen leistungsfähigen Spintronik Geräten.
Der zweite Teil fokussiert auf die Änderungen der elektronischen Eigenschaften von MnPc und Alq3 während der Oxidation (O2-Aussetzung) beziehungsweise Reduktion (Kalium-Abscheidung). Abgesehen von den VB-PES und IPES Messungen, bieten die Röntgenphotoelektronenspektroskopie (XPS) und die Röntgen-Nahkante-
Absorptions-Spektroskopie (NEXAFS) wichtige Informationen w. z. B. die Menge von K in der Molekülschicht und den Spin-Zustand im undotierten und im dotierten MnPc.
Der dritte Teil beschäftigt sich mit den optischen Eigenschaften von MnPc, Alq3 und α-NPD als Reinmaterialien sowie mit K-dotierten Molekülen, in situ verfolgt mittels spektroskopischer Ellipsometrie (SE). Vom SE-Spektrum wurde der Imaginärteil der dielektrischen Funktion abgeleitet. Während α-NPD fast keine Änderung im Absorptionsspektrum nach der Dotierung zeigt, zeigt Alq3 dagegen ein Wandel zu einer dotierten Phase mit kleine Änderungen im Spektrum. Dabei hat MnPc drei stabile dotierte Phasen mit großen spektralen Änderungen. Außerdem zeigt die Oxidation von MnPc umgekehrt Eigenschaften zur dotierten Phase. Alle diese Messungen sind einzigartig und sehr wichtig für die Entwicklung von OLED und Spintronik Geräten.
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Unuigbe, David Moweme. « Characterisation of silicon nanoparticles produced by mechanical attrition using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoemission spectroscopy ». Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/12105.
Texte intégralRésumé :
Includes abstract.Includes bibliographical references.
The establishment of printing technologies, using nanoparticle based inks, promises inexpensive manufacture of electronic devices. However, to produce working devices, nanoparticles have to meet requirements on size, shape, and composition. In the application of silicon nanoparticles in electronics, it is important that a network of interconnecting particles is formed through which charge transport can take place. Of further importance is that there is an absence of surface oxide in order to maintain a direct silicon-silicon connection within the network. In this work, cheap and scalable production of silicon nanoparticles is achieved efficiently with a top-down process of mechanical attrition by high energy milling.
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Magnuson, Martin. « Electronic Structure Studies Using Resonant X-ray and Photemission Spectroscopy ». Doctoral thesis, Uppsala University, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-56480.
Texte intégralRésumé :
This thesis addresses the electronic structure of molecules and solids using resonant X-ray emission and photoemission spectroscopy. The use of monochromatic synchrotron radiation and the improved performance of the instrumentation have opened up the possibility of detailed analyses of the response of the electronic systems under interaction with X-rays. The experimental studies are accompanied by numerical ab initio calculations in the formalism of resonant inelastic scattering. The energy selectivity has made it possible for the first time to study how the chemical bonds in a molecule break up during resonant inelastic X-ray scattering. In the conjugated polymer systems, the element selectivity of the X-ray emission process made it possible to probe the different atomic elements separately. The X-ray emission technique proved to be useful for extracting isomeric information, and for measuring the change in the valence levels at different degrees of doping. In this thesis, spectral satellite features in transition metals were thoroughly investigated for various excitation energies around a core-level threshold. By measuring the relative spectral intensity of the satellites it was possible to extract information on the partial core-level widths. Using the nickel metal system as an example, it was shown that it is possible to probe the different core-excited states close toshake-up thresholds by measuring the relative spectral intensity variation of the Auger emission.Resonant photoemission measurements showed unambiguous evidence of interference effects. Theseeffects were also thoroughly probed using angle-dependent measurements. The combination of X-rayemission and absorption were useful for studying buried layers and interfaces due to the appreciable penetration depth of soft X-rays. X-ray scattering was further found to be useful for studying low-energy excited states of rare earth metallic compounds and transition metal oxides.
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Lemon, Christine Elizabeth. « Atmospheric Corrosion of Silver Investigated by X-ray Photoelectron Spectroscopy ». The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1350660429.
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Ehrman, James D. « X-Ray Photoelectron Spectroscopy Studies of Orthopedic Materials ». University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1248115447.
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Lebrun, Delphine. « Thiolsulfinates/Thiolsulfonates formation : X-ray photoelectron spectroscopy (XPS) of oxidized thiols on flat surfaces ». Thesis, Uppsala universitet, Materialfysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160332.
Texte intégralRésumé :
In order to find another way to fix peptides on surfaces we study the chemical and electro oxidation of a Silicon flat surface after silanization. Traditional experimental setup is used to make the oxidations and Xray photoelectron spectroscope (XPS) is used to analyze the surfaces. We find that chemical oxidation works well but we cannot fix the Alanine molecule on the surface, unlike the electro oxidation which works for peptides fixation. We need to focus on the electro oxidation process, use a more accurate method to analyze the samples and probably used a higher Alanine concentration.
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Nishino, Yoichi, Takahiro Sugiura, Suguru Tanaka, Yuko Tamada, Yusuke Sandaiji, Hidetoshi Miyazaki, Manabu Inukai et al. « Soft X-ray photoemission study of thermoelectric alloys Fe2−x−yIryV1+xAl and Fe2−xV1+x−yTiyAl ». Elsevier, 2011. http://hdl.handle.net/2237/20776.
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MIYAZAKI, Hidetoshi, Kazuo SODA, Masahiko KATO et Shinya YAGI. « Soft x-ray photoemission study of the Heusler-type Fe_2VAl_1-zGe_z alloys ». Elsevier, 2007. http://hdl.handle.net/2237/9386.
Texte intégral
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Jagst, Eda [Verfasser]. « Surface functional group characterization using Chemical Derivatization X-ray Photoelectron Spectroscopy (CD-XPS) / Eda Jagst ». Berlin : Freie Universität Berlin, 2010. http://d-nb.info/1024743934/34.
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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.
Texte intégralRésumé :
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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Jain, Varun. « Preparation, Functionalization, and/or Characterization by X-ray Photoelectron Spectroscopy of Carbon Surfaces for Biosensors and Other Materials ». BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8113.
Texte intégralRésumé :
My dissertation is primarily divided into two parts. The first deals with the preparation, functionalization, and characterization of carbon surfaces prepared by direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS) as substrates for bioarrays. Part two discusses applications of XPS peak fitting in surface chemical analysis. Chapter 1, the introduction, includes (i) a discussion of the construction of bioarrays and the preparation of sputtered surfaces, e.g., by DCMS and HiPIMS, and also functionalization (bioconjugate) chemistry with special emphasis on the importance of covalent functionalization of surfaces, and (ii) a discussion of the surface characterization techniques and accompanying analysis methods I have primarily used, which include X-ray photoelectron spectroscopy (XPS), near-ambient pressure XPS (NAP-XPS), XPS peak fitting, and contact angle goniometry (wetting). Chapter 2 discusses the preparation, characterization, and functionalization of DCMS and HiPIMS carbon surfaces for bioarrays. Here, two functionalization chemistries are explored, where the activity of DCMS and HiPIMS carbon towards amidation and amination is compared. Chapter 3 focuses on the use of Gaussian-Lorentzian sum (GLS) and Gaussian-Lorentzian product (GLP) line shapes in the context of peak fitting XPS narrow scans. This discussion includes a comparison of the GLS and GLP line shapes with the Voigt function. Chapters 4 and 5 discuss the applications of XPS peak fitting in materials characterization. Chapter 4 talks about XPS data analysis in the context of the chemical vapor deposition of various aminosilanes and their effect on peptide stability and purity. Chapters 5 describes the surface chemical analysis of various materials by NAP-XPS, including accompanying data analysis and/or peak fitting. The materials probed here cannot be analyzed at ultra-high vacuum by conventional XPS, hence, they are analyzed by NAP-XPS. Chapter 5 is divided into 5 sections. Section 5.1.1 discusses the characterization and analysis of a solution of bovine serum albumin (BSA) by peak fitting the C 1s and O 1s peak envelopes. Section 5.1.2 discusses the analysis of polytetrafluoroethylene (PTFE) at different pressures. Here, the effect of increasing background pressure and X-ray illumination time on the equivalent widths of the F 1s narrows scans is shown. Environmental charge compensation is also discussed here. Section 5.1.3 includes the analysis of poly(γ-benzyl L-glutamate) (PBLG), where the C 1s and O 1s peak envelopes were peak fitted to determine/confirm the structure and composition of this polymer. Section 5.1.4 contains an analysis and comparison of three different human hair samples: (i) untreated, (ii) colored, and (iii) bleached. Here, a comparison of the Si 2p, S 2p, and C 1s peaks illustrates the effects of the different treatments. Section 5.1.5 shows the characterization and analysis of liquid and solid phosphate buffered saline (PBS). Chapter 6 presents conclusion of my work and discusses future work.
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Wu, Hao-Hsuan. « Angle-Resolved X-Ray Photoemission Spectroscopy of Self-Assembled Polymer Films on AlGaN/GaN Field Effect Transistors ». The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1305639462.
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Koch, Kevin David. « Temperature, photon energy and thickness dependent studies of Cs 5p core-levels on Cu(100), development of photoemission equipment and the 6m-TGM at CAMD / ». Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3037512.
Texte intégral
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Pašiškevičius, Audrius. « Synthesis of the Vanadium Oxide Compounds and Investigation by X-Ray Photoelectron Spectroscopy Method ». Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110219_122819-95620.
Texte intégralRésumé :
The thin films of oxide xerogels and bronzes and molecular oxide xerogels and bronzes of vanadium compounds were synthesized by sol-gel technology method. The chemical composition of mentioned compounds was investigated using XPS method in order to determine the valence of metal ions. It is shown that it is possible to produce the thin films of vanadium oxide bronzes using simple methods. The possibility to use vanadium-ammonium oxide hydrated compounds as materials for producing the ammonium sensors is shown in the dissertation.Šiame darbe panaudojant zolis-gelis technologiją, susintetinti vanadžio junginių oksidinių kserogelių ir bronzos bei molekulinių oksidinių kserogelių ir bronzų plonieji sluoksniai. Visų minėtų medžiagų cheminė sudėtis ištirta Rentgeno fotoelektronų spektroskopijos metodu, siekiant nustatyti metalų jonų valentines būsenas. Panaudojant zolis-gelis technologiją, galima gana paprastais metodais, nenaudojant sudėtingos technologinės įrangos, gaminti vanadžio oksidinių bronzų plonuosius sluoksnius. Vanadžio amonio hidratuoti oksidiniai junginiai gali būti naudojami kaip medžiagos amoniako dujų jutikliams gaminti.
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McGovern, William Robert. « Characterization of carbon-molecule-metal junctions by cyclic voltammetry, raman spectroscopy and X-Ray photoelectron spectroscopy ». The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1114560996.
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Parker, Andrew Donald. « Oxidative dissolution of chalcopyrite in ferric media : an x-ray photoelectron spectroscopy study ». Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/140.
Texte intégralRésumé :
The oxidative dissolution of chalcopyrite in ferric media often produces incomplete copper recoveries. The incomplete recoveries have been attributed to inhibition caused by the formation of a metal deficient sulphide and the deposition of elemental sulphur and jarosite. Although these phases have been qualitatively identified on the surface of chalcopyrite, none have been quantitatively identified. The aim of the project was to quantitatively analyse the surface before and after oxidative dissolution, with X-ray photoelectron spectroscopy (XPS), and to use the phases identified as the basis for mechanisms of dissolution and inhibition.XPS analysis was performed on chalcopyrite massive fractured under anaerobic atmosphere and chalcopyrite massive and concentrate oxidised in 0.1 M ferric sulphate (pH 1.9) and 0.2 M ferric chloride (pH 1.6) at 50, 65 and 80ºC. Quantitative XPS analysis of the chalcopyrite surfaces required the development of programs that accounted for the observed XPS spectra. The output of these programs was used to construct profiles of the chalcopyrite surfaces and the deposited phases. These surface profiles were correlated with copper recoveries determined for chalcopyrite concentrate dissolution under the same conditions.The surface of chalcopyrite before oxidative dissolution reconstructs to form a `pyritic' disulphide phase. This phase is oxidised in ferric media to form thiosulphate via the incorporation of oxygen atoms from the hydration sphere. The thiosulphate reacts in the oxidising conditions of low pH to form elemental sulphur, sulphite and sulphate. The sulphate complexes with ferric to produce hydronium jarosite. This reaction occurs at the surface during the initial stages of dissolution and in the bulk solution during the latter stages. This precipitation of hydronium jarosite during the latter stages of dissolution corresponds to inhibition of the dissolution reaction. It is therefore concluded hydronium jarosite is responsible for inhibiting the oxidative dissolution of chalcopyrite in ferric media.The identification of hydronium jarosite as the inhibiting phase is consistent with the industrial practice of removing `excess' iron from the ferric solution before oxidative dissolution. However, additional iron and sulphate are generated at the chalcopyrite surface during oxidative dissolution. These high iron and sulphate concentrations combine with the low pH and high temperatures favoured for the oxidative dissolution of chalcopyrite to produce ideal conditions for jarosite precipitation. Therefore, pH must be lowered further to prevent jarosite precipitation and enhance copper recoveries from chalcopyrite in ferric media.
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Johnson, Brian Ivins. « Preparation and Detailed X-Ray Photoelectron Spectroscopy and Spectroscopic EllipsometryAnalysis of Ultrathin Protective Coatings ». BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8119.
Texte intégralRésumé :
Ultra-thin films (UTFs) are important in many applications, seen in the semiconductor industry, in chromatography, in sensing, in microfluidics, in aerospace, and in robotics. They also protect materials from corrosion, change surface energies, limit water intrusion into materials, allow material self-cleaning and self-healing, provide scratch resistance, and impart other specific chemical properties. In many cases, UTFs drastically alter surface properties and therefore their applications. It is imperative that proper and consistent characterization be performed on coatings to confirm and understand their desired properties. In Chapter two, Al oxidation under MgF2 protective layers is studied using real time X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). These tools allowed me to monitor Al oxidation for both short (hours) and long (months) periods of time. XPS revealed the chemical changes that took place in these materials as a function of time, and these changes were verified with SE. These studies help increase an understanding of aluminum changes under MgF2 protective layers. The third chapter demonstrates ab initio calculations guided X-ray photoelectron spectroscopy (XPS) analysis of surfaces functionalized with fluorinated silanes. This study addresses deficiencies in the literature where CF2:CF3 ratios from experimental XPS data do not match theoretical CF2:CF3 ratios. In a systematic approach, I developed semi-empirical models directed both by ab initio calculations and adjustable, empirical parameters. These models were effective in describing the raw data and exceeded fitting methods used in literature. In Chapter four, SiO2 UTFs with variable thicknesses deposited on Eagle XG® glass substrates are characterized. Challenges associated with this work consisted of similar optical functions of the film and substrate as well as backside reflections from the substrate. These obstacles were met using a multi-sample analysis (MSA), a variable angle spectroscopic ellipsometric approach, and mechanical abrasion/roughening of the substrate backside. With these approaches, I developed a model that precisely fit the data collected from all the samples and gave the correct optical function of the material along with thickness values for each film. Surface characterization represents a commitment of resources. It takes time to make measurements, and it takes time to analyze and understand the results. As presented in this work, I increase understanding of ultra-thin films at interfaces using both a multi-tool approach as well as using multiple analytical methods on data collected from each tool.
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Parker, Andrew Donald. « Oxidative dissolution of chalcopyrite in ferric media : an x-ray photoelectron spectroscopy study ». Curtin University of Technology, School of Science and Computing, 2008. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=118673.
Texte intégralRésumé :
The oxidative dissolution of chalcopyrite in ferric media often produces incomplete copper recoveries. The incomplete recoveries have been attributed to inhibition caused by the formation of a metal deficient sulphide and the deposition of elemental sulphur and jarosite. Although these phases have been qualitatively identified on the surface of chalcopyrite, none have been quantitatively identified. The aim of the project was to quantitatively analyse the surface before and after oxidative dissolution, with X-ray photoelectron spectroscopy (XPS), and to use the phases identified as the basis for mechanisms of dissolution and inhibition.XPS analysis was performed on chalcopyrite massive fractured under anaerobic atmosphere and chalcopyrite massive and concentrate oxidised in 0.1 M ferric sulphate (pH 1.9) and 0.2 M ferric chloride (pH 1.6) at 50, 65 and 80ºC. Quantitative XPS analysis of the chalcopyrite surfaces required the development of programs that accounted for the observed XPS spectra. The output of these programs was used to construct profiles of the chalcopyrite surfaces and the deposited phases. These surface profiles were correlated with copper recoveries determined for chalcopyrite concentrate dissolution under the same conditions.
The surface of chalcopyrite before oxidative dissolution reconstructs to form a `pyritic' disulphide phase. This phase is oxidised in ferric media to form thiosulphate via the incorporation of oxygen atoms from the hydration sphere. The thiosulphate reacts in the oxidising conditions of low pH to form elemental sulphur, sulphite and sulphate. The sulphate complexes with ferric to produce hydronium jarosite. This reaction occurs at the surface during the initial stages of dissolution and in the bulk solution during the latter stages. This precipitation of hydronium jarosite during the latter stages of dissolution corresponds to inhibition of the dissolution reaction. It is therefore concluded hydronium jarosite is responsible for inhibiting the oxidative dissolution of chalcopyrite in ferric media.
The identification of hydronium jarosite as the inhibiting phase is consistent with the industrial practice of removing `excess' iron from the ferric solution before oxidative dissolution. However, additional iron and sulphate are generated at the chalcopyrite surface during oxidative dissolution. These high iron and sulphate concentrations combine with the low pH and high temperatures favoured for the oxidative dissolution of chalcopyrite to produce ideal conditions for jarosite precipitation. Therefore, pH must be lowered further to prevent jarosite precipitation and enhance copper recoveries from chalcopyrite in ferric media.
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Saffarini, Ghassan. « X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and density study of ternary chalcogenide glasses based on Ge-Se and Ge-S ». Thesis, Brunel University, 1991. http://bura.brunel.ac.uk/handle/2438/7396.
Texte intégralRésumé :
Glasses of the systems Ge-Se-X (X = Ga, Sn, Bi, Sb), Ge-S-Y (Y = Ag, Ga, Sn, Bi) and Se-S have been examined using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), density and differential scanning calorimetry (DSC). Two of the compositions, GeSe2 and (GeSe2)92Ga8, have also been examined by extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). The emphasis of the XPS measurements was on the changes in the binding energies with composition of the core peaks of the glasses, and on the plasmon energy losses from the L3M4,5M4,5 Auger lines of Se and Ge. It was found that there were small shifts in the binding energies of the core peaks on substitution but the plasmon energy changed markedly with composition. For the XRD measurements, the focus was on two features : (a) to ensure that the samples prepared were truely amorphous and (b) to confirm the presence of the first sharp diffraction peak (FSDP) on the interference functions. The density measurements showed that the addition of the third element (X or Y) to the binary resulted in an increase in the relative density except for one system, Ge-Se-Sn, which showed the opposite behaviour. The DSC measurements showed that the addition of the third element to the binary resulted in a decrease in the glass transition temperatures. The EXAFS and XANES measurements of GeSe2 and (GeSe2)92Ga8 glasses showed that there was very little change in the local order around the Ge atom in GeSe2 glass with increase in temperature and that the local order around the Ge atom changes on alloying GeSe2 with Ga. Correlations between parameters and measured properties of the ternary alloys have been investigated. It has been found that the parameter
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Hansson, Evelina. « Surface Analysis of Aluminium Alloy AA3003 Exposed to Immersion Corrosion Test : An X-Ray Photoelectron Spectroscopy Study ». Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-150170.
Texte intégralRésumé :
Corrosion is a common issue which must be accounted for when designing all metal products in our society. Many factors need to be considered when new alloys are created, and further knowledge of the corrosion process would be of great use for companies worldwide. The purpose of this thesis was to investigate if X-ray Photoelectron Spectroscopy, XPS, can be used to characterise and quantify corrosion products. With the goal to develop a method that can be used for further studies to increase our understanding of the corrosion process. Aluminium alloy AA3003 was subjected to an immersion corrosion test in an acidified salt solution for different periods of time and the produced chemical compounds were characterised using XPS. The results revealed a direct connection between corrosion time and formed product, which after characterisation proved to be aluminium hydroxide, Al(OH)3. It was concluded that XPS can be used for corrosion studies and is a method that shows great potential and should be further developed.I metallindustrin är korrosion ett ständigt förekommande problem som måste tas i beaktande vid design av metallprodukter. Många faktorer är avgörande när nya legeringar utvecklas och en djupare kunskap om korrosionsprocessen och dess mekanismer är av stort värde för företag världen över. Syftet med detta examensarbete var att undersöka huruvida röntgen-fotoelektron-spektroskopi, XPS, kan användas för att kvalitativt och kvantitativt karakterisera de korrosionsprodukter som bildas vid korrosion. Med målet att presentera en metod som kan användas för att vidare undersöka och öka vår förståelse för korrosionsprocessen. Aluminiumlegering AA3003 utsattes för accelererad korrosion i en surgjord saltlösning under varierande tid och korrosionsprodukter karakteriserades med XPS. Resultatet påvisade direkt korrelation mellan korrosionstid och mängd produkt. Korrosionsprodukten visade sig vara aluminiumhydroxid, Al(OH)3, och med det i åtanke kunde slutsatsen dras att XPS kan användas vid studier av korrosion. Den utvärderade metoden visar stor potential och detta examensarbete öppnar upp för vidare forskning som kan komma att öka förståelsen för korrosionsprocessen och hur den kan kontrolleras.
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Lei, Yu-Guo. « Surface morphology and chemical composition of polymers studied by AFM, XPS and ToF-SIMS / ». View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CENG%202002%20LEI.
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Graham, Amy L. « Characterization of Heterojunctions via X-Ray and UV Photoemission Spectroscopy : Energy Level Implications for Single and Mixed Monolayer SAMs, CdSe Nanoparticle Films, and Organic Semiconductor Depositions ». Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195913.
Texte intégralRésumé :
This work has centered on the interface dipoles arising at heterojunctions between metals, semiconductor nanoparticles, self-assembled monolayers, and organic semiconductor materials. Alkanethiol self-assembled monolayers, CdSe nanocrystals, and the organic semiconductors zinc phthalocyanine (ZnPc) and Buckminster fullerene (C60) were the basis of these investigations. UV photoemission spectroscopy has proven to be an invaluable tool to observe the vacuum level shifts for these analyses while using XPS to corroborate surface structure. With a full evaluation of these surfaces, the shifts in the vacuum level, valence ionizations, and core ionizations, the impact of these interfaces, as well as their influence on the subsequent deposition of organic semiconductor layers is established.Alkanethiols possessing varying dipole moments were examined on gold and silver substrates. The viability of these alkanethiols was demonstrated to predictively adjust the work function of these metals as a function of their intrinsic dipole moments projected to surface normal, and established differences between Ag--S and Au--S bonds. The capability of the SAMs to modify the work function of gold provided an opportunity for mixed monolayers of the alkanethiols to produce a precise range of work functions by minimal adjustments of solution concentration, which were examined with a simple point dipole model.Photoemission spectroscopy offers a thorough analysis of CdSe nanoparticle films. Despite a plethora of research on these nanocrystals, there still is controversy on the magnitude of the shift in the valence band with diameter. In our research we found the majority of the valence band shift could be attributed to the interface dipole, ignored previously. Meanwhile, the valence band tethered films was obscured by the sulfur of the thiol tether.Finally, organic semiconductor layers deposited on SAMs on gold exhibited various interface dipole effects at these heterojunctions. Charge transfer states of ZnPc did not favor energy level alignment on the SAM/Au substrates used; C60 demonstrated vacuum level shifts on C15 and C12ph alkanethiol monolayers consistent with the interface charge transfer (ICT) model. These results provide credibility to models recently demonstrated in the literature for other passivated metal surfaces, and include the viability of SAMs in these discussions.
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Jagst, Eda [Verfasser], Manfred [Gutachter] Hennecke et Rainer [Gutachter] Haag. « Surface Functional Group Characterization Using Chemical Derivatization X-ray Photoelectron Spectroscopy (CD-XPS) / Eda Jagst ; Gutachter : Manfred Hennecke, Rainer Haag ». Berlin : Bundesanstalt für Materialforschung und -prüfung (BAM), 2011. http://d-nb.info/1122741030/34.
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Rufe, Eric. « Assessing the Reactive Surface Area of Phlogopite during Acid Dissolution : An Atomic Force Microscopy, X-ray Photoelectron Spectroscopy, and Low Energy Electron Diffraction Study ». Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/31837.
Texte intégralRésumé :
The behavior during dissolution of edge and basal surfaces of the mica phlogopite were examined using in situ atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) in an attempt to characterize the reactive surface area during dissolution. Mica minerals are the ideal material for this study because they offer a high degree of structural anisotropy. Therefore surfaces with different structures are easily identified. Dissolution is shown to proceed preferentially by removal of material from {hk0} edges. Dissolution rates were calculated by measuring the volume of material removed from etch pits, and normalizing to either the â reactiveâ surface area of {hk0} edges exposed at pit walls, or to a total â BET-equivalentâ surface area. Rates normalized to total surface area are in the range of dissolution rates reported in the literature. Edge surface normalized rates are about 100 times faster. Long-term in situ AFM observations of phlogopite dissolution reveal that exposed (001) surfaces also display a distinct reactivity, though it operates on a different time scale. The top layer is shown to expand between 39 and 63 hours in contact with pH 2 HCl solution. Subsequent LEED analysis shows that the (001) surface becomes amorphous upon reacting with pH 2 HCl. Compositional characterization of the phlogopite after reaction shows that for pitted phlogopite surfaces, dissolution is characterized by leaching of octahedral cations and polymerization of the silica-enriched residual layer. No chemical changes or polymerization are observed for freshly cleaved unpitted phlogopite after reaction with pH 2 HCl for 24 hours. This suggests a gallery access mechanism is facilitated by edge attack, and is only significant on exposed (001) surfaces after a certain amount of dissolution by edge attack.Master of Science
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Knut, Ronny. « New Materials for Spintronics : Electronic structure and magnetism ». Doctoral thesis, Uppsala universitet, Yt- och gränsskiktsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-167415.
Texte intégralRésumé :
Materials exhibiting new functionalities due to interdependent electric (e.g. conductivity) and magnetic properties are potentially interesting for spintronics applications. We have investigated electronic and magnetic properties by means of x-ray spectroscopies and SQUID magnetometry in several magnetic materials, often in the form of thin films, which have shown promising properties for applications. One of the main subjects has been studies of inter-diffusion between layers in multilayer structures, which is an important factor for spin-dependent transport and magnetic properties. These studies have been performed by high kinetic (HIKE) photoemission spectroscopy where high photon energies increase the bulk sensitivity in comparison to soft x-ray photoemission spectroscopy. Cu/Ni multilayers were studied mainly as a model system and revealed a diffusion process that was dependent on layer thicknesses and capping materials. CoFeB/MgO/CoFeB, which is used as a magnetic field sensor in hard drives, has recently been shown to exhibit a perpendicular magnetic anisotropy (PMA) switchable by electric fields. We have studied both the interface quality and magnetic properties of thin CoFeB layers exhibiting PMA. Layered structures of full Heusler alloys Co2MnGe/Rh2CuSn have been proposed as a promising candidate for current-perpendicular-to-plane giant magneto-resistance sensors. Using HIKE,we have shown that diffusion of atoms, mainly Mn, occurs at temperatures lower than what is used in device fabrication, which likely contributes to the limited magneto-resistance values obtained. Lately, a large body of research has been performed on semiconductors doped with transition metal elements with the hope to find a ferromagnetic semiconductor at room temperature, a foundation for new devices combining spin and charge in their functionality. We have investigated Co and Fe doping in ZnO for different concentrations of the dopants and different annealing temperatures. The Co and Fe atoms are shown to forms clusters for which antiferromagnetic interactions are dominating.
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Nordlund, Dennis. « Core Level Spectroscopy of Water and Ice ». Doctoral thesis, Stockholm : Fysikum, Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-181.
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Lindblad, Rebecka. « Electronic Structures and Energy Level Alignment in Mesoscopic Solar Cells : A Hard and Soft X-ray Photoelectron Spectroscopy Study ». Doctoral thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-221450.
Texte intégralRésumé :
Photoelectron spectroscopy is an experimental method to study the electronic structure in matter. In this thesis, a combination of soft and hard X-ray based photoelectron spectroscopy has been used to obtain atomic level understanding of electronic structures and energy level alignments in mesoscopic solar cells. The thesis describes how the method can be varied between being surface and bulk sensitive and how to follow the structure linked to particular elements. The results were discussed with respect to the material function in mesoscopic solar cell configurations. The heart of a solar cell is the charge separation of photoexcited electrons and holes, and in a mesoscopic solar cell, this occurs at interfaces between different materials. Understanding the energy level alignment between the materials is important for developing the function of the device. In this work, it is shown that photoelectron spectroscopy can be used to experimentally follow the energy level alignment at interfaces such as TiO2/metal sulfide/polymer, as well as TiO2/perovskite. The electronic structures of two perovskite materials, CH3NH3PbI3 and CH3NH3PbBr3 were characterized by photoelectron spectroscopy and the results were discussed with support from quantum chemical calculations. The outermost levels consisted mainly of lead and halide orbitals and due to a relatively higher cross section for heavier elements, hard X-ray excitation was shown useful to study the position as well as the orbital character of the valence band edge. Modifications of the energy level positions can be followed by core level shifts. Such studies showed that a commonly used additive in mesoscopic solar cells, Li-TFSI, affected molecular hole conductors in the same way as a p-dopant. A more controlled doping can also be achieved by redox active dopants such as Co(+III) complexes and can be studied quantitatively with photoelectron spectroscopy methods. Hard X-rays allow studies of hidden interfaces, which were used to follow the oxidation of Ti in stacks of thin films for conducting glass. By the use of soft X-rays, the interface structure and bonding of dye molecules to mesoporous TiO2 or ZnO could be studied in detail. A combination of the two methods can be used to obtain a depth profiling of the sample.
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Farha, Rana. « Nanostructures organométalliques : croissance par photochimie de couches inorganiques sous films de Langmuir ». Paris 6, 2007. http://www.theses.fr/2007PA066429.
Texte intégralRésumé :
Notre but est de former des interfaces organo-minérales d’épaisseur nanométrique. Pour ce faire, nous déposons une monocouche organique (film de Langmuir) sur une solution contenant les ions métalliques. La croissance du film inorganique est obtenue par réaction photochimique au niveau des têtes amphiphiles de la monocouche organique qui sert donc de « moule » pour les ions adsorbés. Nous avons étudié deux systèmes par des mesures thermodynamiques, d’AFM et d’XPS. Dans le système platine/DODA, la monocouche organique est chargée positivement et on observe la formation de plaques métalliques d’épaisseur nanométrique à l’interface solution/air. Ces plaques, formées en deux étapes, ont une épaisseur de 3 à 4 nm. Nous les avons étudiés après 24 h et 96 h de réaction. Leur taille latérale et leur rigidité évoluent au cours du temps, ainsi que leur nature chimique qui se rapproche au cours du temps de celle du platine métallique. La réaction reste cependant inachevée au bout de 4 jours. Dans le cas du système Argent/acide béhénique, nous avons mis en évidence la formation de plaques d’argent sous la monocouche d’acide béhénique. Ces plaques de 3 à 5 nm d’épaisseur, semblent être formées par de l’argent métallique.
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GIAMPIETRI, ALESSIO. « GROWTH, LOCAL STRUCTURAL AND ELECTRONIC PROPERTIES, AND BAND ALIGNMENT AT SRTIO3-BASED ALL-OXIDE HETEROJUNCTIONS ». Doctoral thesis, Università degli Studi di Milano, 2017. http://hdl.handle.net/2434/476679.
Texte intégralRésumé :
Recent advances in the growth of epitaxial oxide thin films have fostered a steady increase of research on oxide heterojunctions, which are now produced with unprecedented quality. Applications of these systems in the field of electronics, photovoltaics and photocatalysis strongly rely on the capability to master band gap engineering on the atomic scale. Strontium titanate (SrTiO3) is the substrate of choice commonly used in the production of all-oxide heterostructures, as in many cases these systems display a two dimensional electron gas (2DEG) confined at the interface, such as in the LaAlO3/SrTiO3 junction. The band offsets at the interface determine on which of the constituent materials the 2DEG will be confined, and provide additional information on the degree of confinement as well, so the study of the band alignment in oxide-based heterostructures is of crucial importance. Novel properties and functionalities can be achieved upon substitution of LaAlO3 with other oxide materials, an example being the BiFeO3 perovskite. In fact, BiFeO3 is a multiferroic material, and a complete control of the BiFeO3/SrTiO3 heterostructure may allow the tuning of the 2DEG at the interface through the application of an external electric or magnetic field. A 2DEG is also observed in the Al2O3/SrTiO3 junction, which show electron mobilities greater than those previously measured in perovskite-based heterojunctions. Despite in many structures the 2DEG is not observed, different interesting applications can still be obtained, such as in the CuO/SrTiO3 heterostructure, which is a promising material for the production of solar cells and for photoelectrochemical water splitting applications. The main objective of this work is to demonstrate the growth of high quality BiFeO3/SrTiO3, Al2O3/SrTiO3 and CuO/SrTiO3 heterostructures by off-axis sputtering, and to provide a detailed analysis of the interface properties. The band alignment at the interface is thus measured and discussed for each of these materials.
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Dhakal, Dileep, Thomas Waechtler, Schulz Stefan E, Robert Mothes, Stefan Moeckel, Heinrich Lang et Thomas Gessner. « In-situ XPS Investigation of ALD Cu2O and Cu Thin Films after Successive Reduction ». Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-147043.
Texte intégralRésumé :
This talk was presented in the 14th International Conference on Atomic Layer Deposition (ALD 2014) in Kyoto, Japan on 18th June 2014.
Abstract
Atomic Layer Deposition (ALD) is emerging as a ubiquitous method for the deposition of conformal and homogeneous ultra-thin films on complex topographies and large substrates in microelectronics. Electrochemical deposition (ECD) is the first choice for the deposition of copper (Cu) into the trenches and vias of the interconnect system for ULSI circuits. The ECD of Cu necessitates an electrically conductive seed layer for filling the interconnect structures. ALD is now considered as a solution for conformal deposition of Cu seed layers on very high aspect ratio (AR) structures also for technology nodes below 20 nm, since physical vapor deposition is not applicable for structures with high AR. Cu seed layer deposition by the reduction of Cu2O, which has been deposited from the Cu(I) β-diketonate [(nBu3P)2Cu(acac)] (1) used as Cu precursor, has been successfully carried out on different substrates like Ta, TaN, SiO2, and Ru [1, 2]. It was found that the subsequent gas-phase reduction of the Cu2O films can be aided by introducing catalytic amounts of a Ru precursor into the Cu precursor, so that metallic copper films could potentially obtained also on non-catalytic substrates [3, 4]. In this work, in situ X-ray photoelectron spectroscopy (XPS) investigation of the surface chemistry during Cu2O ALD from the mixture of 99 mol % of 1 and 1 mol % of [Ru(η5 C5H4SiMe3)(η5-C7H11)] (2) as ruthenium precursor, and the reduction of Cu2O to metallic Cu by formic acid carried out on SiO2 substrate are demonstrated. Oxidation states of the Cu in the film are identified by comparing the Cu Auger parameter (α) [5] with literature data. α calculated after ALD equals 362.2 eV and after reduction equals 363.8 eV, comparable to the Cu2O and metallic Cu in thin-films [6] respectively. In addition, <10 % of Cu(I), Cu(II), and Cu(OH)2 species are identified from the Cu 2p3/2 and Cu L3VV Auger spectrum after reduction. Consequently, the ALD Cu2O is successfully reduced to metallic copper by in-situ thermal reduction using formic acid.
[1] T. Waechtler et al., J. Electrochem. Soc., 156 (6), H453 (2009).
[2] T. Waechtler et al., Microelectron. Eng., 88, 684 (2011).
[3] S. Mueller et al., Conference Proceedings SCD 2011, Semiconductor Conference Dresden, pp. 1-4.
[4] T. Waechtler et al., US Patent Application Publication, US 2013/0062768.
[5] C. D. Wagner, Faraday Discuss. Chem. Soc., 60, 291 (1975).
[6] J. P. Espinós et al., J. Phys. Chem. B, 106, 6921 (2002).
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Suzuki, Noriaki. « Applications of time-of-flight secondary ion mass spectrometry (TOF-SIMS) and x-ray photoelectron spectroscopy (XPS) to study interactions of genetically engineered proteins with noble metal films / ». Thesis, Connect to this title online ; UW restricted, 2006. http://hdl.handle.net/1773/10618.
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Wu, Meiyi. « Development of the x-ray standing waves methodology to probe the interfaces of periodic multilayers ». Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS175/document.
Texte intégralRésumé :
La qualité des interfaces dans les multicouches périodiques est essentielle au développement de miroirs réfléchissant efficacement dans les domaines des rayons X et extrême ultraviolet (X-EUV). De manière générale, la structure des interfaces dépend des possibles interdiffusion et processus chimiques aux interfaces entre couches. L'idée principale de cette thèse est d'appliquer la technique des ondes stationnaires dans le domaine X à la caractérisation de matériaux, principalement mais non exclusivement aux multicouches périodiques. Cette méthode est basée sur l'interférence de deux faisceaux de rayons X cohérents. L'interférence constructive sur un plan anti-nodal amplifie le champ électrique tandis que l'interférence destructive minimise ce dernier sur un plan nodal. Cette technique des ondes stationnaires dans le domaine X permet l'excitation (photoémission, fluorescence, ...) d'endroits spécifiques dans un empilement périodique de matériaux. De cette manière, les spectres expérimentaux ainsi obtenus sont principalement les spectres caractéristiques des atomes situés sur un plan anti-nodal. Combinée avec d'autres techniques expérimentales telles que la spectroscopie d'émission X (XES) ou la spectroscopie de photoélectrons dans le domaine X (XPS), une information sélective en profondeur, avec une sensibilité sub-nanométrique, peut être obtenueThe interfacial information of periodic multilayers can be crucial for the development of reflecting mirrors which operate in the X-ray and extreme ultraviolet (X-EUV) ranges. Such information may contain the interdiffusion and chemical process at the interfaces of the layers. The idea of this thesis is to apply the X-ray standing wave technique to the characterization of materials, mainly but not limited to the periodic multilayers. X-ray standing wave technique enables to enhance the excitation (photoemission, fluorescence etc.) of specific locations within a periodic stack. The nature of such advantage is the interference of two coherent X-ray beams. One may compare the X-ray standing waves with the mechanical standing waves. The constructive interference at the anti-nodal plane amplifies the electric field; while the destructive interference at the nodal plane minimizes the electric field. In this way, the experimental spectra obtained under standing wave field will be mostly the material located on the anti-nodal plane. Combined with other techniques such as X-ray emission spectroscopy and X-ray photoelectron spectroscopy, a depth-selective information with a sub-nanoscale sensitivity can be obtained
46
Watcharinyanon, Somsakul. « Characterization of Self-Assembled Monolayers of Oligo(phenyleneethynylene) Derivatives on Gold ». Licentiate thesis, Karlstad : Faculty of Technology and Science, Physics, Karlstad University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-800.
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Bellanger, Marc. « Etude comparative des traitements laser excimère et plasma à décharge barrière diélectrique pour l'amélioration de l'adhésion PBT / Cuivre ». Paris 6, 2006. http://www.theses.fr/2006PA066145.
Texte intégralRésumé :
La thèse a pour étude les effets d’une irradiation laser excimère à 248 nm dans l’air sous le seuil d’ablation d’un film de Poly Butylène Téréphtalate (PBT). Différentes techniques d’analyses de surface permettent de caractériser les modifications de surface provoquée par ce procédé et les conséquences sur les propriétés d’adhérence d’un dépôt d’une fine couche métallique de cuivre par évaporation thermique. Ces effets sont comparés à ceux d’un traitement plasma à décharge barrière diélectrique (DBD) dans l’air à la pression atmosphérique. Cette étude montre que le greffage de fonctions polaires oxygénées et/ou azotés selon les procédés utilisés permettent de renforcer l’adhésion chimique entre le cuivre et le PBT ce qui améliore considérablement les propriétés d’adhérence.
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Vardareli, Tugba. « Polymerization And Characterization Of Allyl Methacrylate ». Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607469/index.pdf.
Texte intégralRésumé :
Allyl methacrylate, AMA was polymerized by chemical initiator and by γ
-radiation under different conditions. The polymer obtained is mostly gel type with some soluble fractions at lower conversions. Arrhenius activation energy is 82.3 kJ/mol for chemical initiated polymerization. The polymer was characterized by FT-IR, NMR, DSC, TGA, XPS, XRD, DLS, and MS methods. It was found that about 98-99% of allyl side groups retained as pendant even after completion of the polymerization, while 1-2% may give crosslinking and/or cyclization that yields lactones and anhydrides. The spectroscopic and thermal results of the work showed that the reaction is not cyclopolymerization, but may have end group cyclization. Molecular weight of 1.1x106 was measured by DLS. Therefore, insolubility is due to the high molecular weight of polymer, even in the early stage of polymerization rather than crosslinking. The Tg of PAMA was observed as 94º
C before curing, upon curing at 150-200º
C, Tg increased to 211º
C as measured by DSC. The thermal treatment of polymer at about 350º
C gave anhydride by linkage type degradation, following side group cyclization. The XPS analysis showed the presence of radical fragments of AIBN and CCl4 associated with oligomers. The MS and TGA thermograms showed two or three stage degradations depending on solubility. The first stage was mostly linkage type degradation for the fragmentation of pendant allyl groups at 225-350º
C. In the second stage, at 395-515º
C, the degradation is random scission and depolymerization.
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Dell'angela, Martina. « Organic molecules at metal surfaces : the role of functional groups in self-assembly and charge transfer ». Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3071.
Texte intégralRésumé :
2007/2008The understanding of the interaction of organic molecules with metal surfaces is crucial for tailoring the desired properties of future devices that can be employed for molecular electronics or biomedical applications. Self-assembly of complex supramolecular structures and charge transfer through molecular films or even through single molecules are some of the properties that have recently attracted much interest both for possible applications and for more fundamental studies. The molecule-surface interaction takes place thanks to the functional groups that constitute the molecule. The choice of appropriate functional groups of the molecules allows their use as building blocks in the fabrication of complicate architectures [1]. In fact, the functional entities can influence molecule-molecule and molecule-surface interactions, governing the self-assembly of the molecules on the surface. In particular, in the thesis I will report on the characterization by means of Helium Atom Scattering (HAS), X-ray Photoemission Spectroscopy (XPS), Near Edge X-ray Absorption Fine Structure (NEXAFS) and Scanning Tunneling Microscopy (STM) of the self-assembly in ultra high vacuum (UHV) conditions of L-methionine molecules on different metal substrates (Ag(111), Cu(111), Au(111), Au(110)). L-methionine is an amino acid with three functional groups which can interact with the substrate or with other molecules: the amino (-NH2), the carboxyl (-COOH) and the thioether (-S-). Moreover, the first two can change their charge state in a protonated amino group (-NH+ 3 ) and a deprotonated carboxyl group (-COO−): the molecules are called zwitterionic and it is allowed the formation of hydrogen bonds between them. Hydrogen bonding between zwitterionic molecules is responsible for the crystallization in the solid state. In the thesis I have studied how, depending on the choice of the substrate and the growth conditions, L-methionine molecules form assemblies with different morphologies and different chemical states of the building blocks. L-methionine molecules deposited on Ag(111) and Au(111) are in the zwitterionic state and interact strongly via hydrogen bonding forming dimers of molecules. The weak interaction with the substrate allows the organization of these dimers in extended bidimensional nanogratings composed of chains of length extending in the micrometer range and with tunable periodicity across the chains. At temperatures below 270K, L-methionine on Cu(111) forms short aggregates of zwitterionic dimers. By increasing the substrate temperature above 300K the charge state of the amino group changes and also the interaction with the surface. Molecules are anionic (-NH2 and -COO−) and form again charged nanogratings. The anionic state of the molecules can also be obtained on the Au(110) surface, where the interaction of the amino and thioether groups with the gold inhibits the formation of zwitterionic dimers via hydrogen bonding. The functional groups in the molecules can also influence their transport properties. The final goal of miniaturization in molecular electronics research is the formation and characterization of a nanoelectronic device in which a molecule between two electrodes plays the role of an active conducting element. In such a device the interaction between the functional groups anchoring the molecule to the electrodes and the electrodes is a crucial element in order to understand and control the conduction. Recent STM-break junction experiments [2] have shown that Au-molecule-Au contacts with amino (- NH2) terminated molecules are better defined than Au-molecule-Au contacts formed with thiol (-SH) terminated molecules [3]. The strong interaction of thiols with gold surfaces is well known in literature and the self-assembly of thiolated molecules is widely employed in many applications. In contrast, the weak interaction of amino terminated molecules with gold is poorly studied. Theoretical calculations suggest that the amine lone pair is responsible for bonding and that it prefers to bind to undercoordinated gold atoms. Within this framework, in the thesis I report on the study of growth of thin films of 1,4-benzenediamine and p-toluidine on two different Au surfaces, where the atoms present different coordination: Au(111) and Au(110). Both molecules interact more strongly with the low coordination (110) surface. By means of Resonant Photoemission Spectroscopy (RPES) it has been possible to disentangle molecular orbitals and determine the ones involved in the charge transfer at the surface. In both cases the charge transfer involves states localized also on the nitrogen atoms indicating a possible interaction of the molecule with the surface through nitrogen atoms. I also studied the assembly of three benzene substituted diamines on Au(111). These results complement very well the results obtained from conduction experiments of different amine-terminated molecules and combined with theoretical investigations can help understanding the basics of the molecular charge transport mechanism. [1] Barth J.V., Costantini G., Kern K., Nature, 437 (2005) 671 [2] Venkataraman L., Klare J. E., Nuckolls C., Hybertsen M. S., Steigerwald M. L., Nature, 442 (7105), 904 (2006) [3] Schreiber F., Progress in Surface Science, 65 (5-8) (2000) 151
Lo studio dell’interazione di molecole organiche con superfici metalliche è di fondamentale importanza per la progettazione di futuri dispositivi che possiedano proprietà ben controllabili in modo tale che possano essere usati per l’elettronica molecolare o per applicazioni biomediche. L’autoassemblaggio di complesse strutture ”supramolecolari” e il trasferimento di carica attraverso film molecolari o anche attraverso singole molecole sono alcune delle proprietà che hanno attratto di recente grande interesse sia per le possibili applicazioni future che per studi di tipo più fondamentale. L’interazione molecola-superficie avviene attraverso i gruppi funzionali che costituiscono le molecole. Molecole con appropriate funzionalizzazioni possono essere usate come mattoni elementari nella fabbricazione di architetture complesse [1]. Infatti, tali gruppi funzionali possono influenzare le interazioni del tipo molecola-molecola e molecola-superficie che governano l’autoassemblaggio delle molecole sulla superficie. In particolare, in questa tesi riporter`o circa la caratterizzazione mediante diffrazione di atomi di elio (HAS), spettroscopia di fotoemissione di raggi X (XPS), misure di assorbimento di raggi X (NEXAFS) e microscopia ad effetto tunnel (STM) dell’autoassemblaggio in condizioni di ultra alto vuoto (UHV) di molecole di L-metionina su diversi substrati metallici (Ag(111), Cu(111), Au(111), Au(110)). La molecola di L-metionina `e un amminoacido che presenta tre gruppi funzionali i quali possono interagire con il substrato o con altre molecole: il gruppo amminico (-NH2), il gruppo carbossilico (- COOH) e il gruppo tioetere (-S-). I primi due possono inoltre cambiare il loro stato di carica originando un gruppo amminico protonato (-NH+ 3 ) e un gruppo carbossilico deprotonato (COO−): in tal caso le molecole sono dette zwitterioniche ed è permessa la formazione di legami a idrogeno tra esse. I legami a idrogeno tra molecole zwitterioniche sono responsabili della loro cristallizzazione nello stato solido. In questa tesi ho studiato come, a seconda della scelta del substrato e delle condizioni di cescita, le molecole di L-metionina formino strutture assemblate che presentano diverse morfologie e diversi stati chimici delle molecole costituenti. Le molecole di L-metionina depositate su Ag(111) e Au(111) sono zwitterioniche e interagiscono fortemente tra di loro tramite legami a idrogeno a formare dimeri di molecole sulla superficie. La debole interazione con il substrato permette l’organizzazione di questi dimeri in estesi reticoli bidimensionali di dimensione nanometrica composti da catene di lunghezza nel range micrometrico e con spaziatura tra le catene controllabile. A temperature sotto 270K, le molecole di L-metionina su Cu(111) formano corti aggregati di dimeri zwitterionici. Aumentando la temperatura del substrato oltre 300K lo stato di carica del gruppo amminico cambia e quindi l’interazione con la superficie. Le molecole sono anioniche (-NH2 e COO−) e formano di nuovo reticoli carichi. Lo stato anionico delle molecole si può ottenere anche sulla superficie di Au(110) dove l’interazione dei gruppi amminico e tioetere con l’oro inibisce la formazione di dimeri zwitterionici via legami a idrogeno. I gruppi funzionali nelle molecole possono anche influenzare le loro proprietà di trasporto. Lo scopo finale della miniaturizzazione nella ricerca nel campo dell’elettronica molecolare è la formazione e caratterizzazione di un dispositivo nanoelettronico in cui una molecola immobilizzata tra due elettrodi gioca il ruolo di elemento conduttivo attivo. In tale dispositivo il controllo dell’interazione tra i gruppi funzionali che tengono la molecola attaccata gli elettrodi e gli elettrodi è un elemento cruciale per la comprensione e il controllo della conduzione. Recenti esperimenti del tipo STM break junction [2] hanno motrato che contatti del tipo Au-molecola-Au con molecole con terminazioni amminiche (NH2) sono meglio definiti che contatti del medesimo tipo con molecole con terminazione tiolica (-SH) [3]. La forte interazione dei tioli con superfici d’oro è ben nota in letteratura e l’autoassemblaggio di molecole con terminazione tiolica è largamente utilizzato in molte applicazioni. In contrasto, la debole interazione di molecole con terminazione amminica con superfici d’oro è stata poco studiata. Recenti calcoli teorici hanno previsto che le molecole si legano alla superficie d’oro attraverso il ”lone pair” localizzato sull’azoto e che sono preferiti i legami con atomi di oro di bassa coordinazione. In particolare, nella tesi riporterò i risultati dello studio della crescita di film sottili di 1,4-benzenediamina e p-toluidina su due diverse superfici d’oro, i cui atomi di superficie presentano diversa coordinazione: Au(111) e Au(110). Ambedue le molecole interagiscono più fortemente con la superficie di bassa coordinazione (110). Tramite la tecnica di fotoemissione risonante (RPES) è stato possibile individuare gli orbitali molecolari e determinare quelli coinvolti nel trasferimento di carica all’interfaccia. In ambedue i casi il trasferimento di carica coinvolge stati che sono localizzati anche sull’atomo di azoto, il che indica una possibile interazione della molecola con la superficie attraverso i gruppi amminici. Ho anche studiato l’assemblaggio su Au(111) di tre diverse benzene-diamine con vii diversi sostituenti legati all’anello. Questi risultati sono un complemento ai risultati ottenuti da esperimenti di conduzione di molecole con diverse terminazioni amminiche e combinati con le investigazioni teoriche possono aiutare nella comprensione dei fondamenti dei meccanismi di trasporto di carica nelle molecole. [1] Barth J.V., Costantini G., Kern K., Nature, 437 (2005) 671 [2] Venkataraman L., Klare J. E., Nuckolls C., Hybertsen M. S., Steigerwald M. L., Nature, 442 (7105), 904 (2006) [3] Schreiber F., Progress in Surface Science, 65 (5-8) (2000) 151
XXI Ciclo
1981
50
Maurau, Rémy. « Etude de l'influence du régime d'une décharge à barrière diélectrique dans un mélange HMDSO/N², sur les propriétés d'un procédé de dépôt ». Paris 6, 2009. https://pastel.archives-ouvertes.fr/pastel-00006139.
Texte intégralRésumé :
Nous avons étudié un procédé de dépôt par décharge à barrière diélectrique à la pression atmosphérique, pour l’obtention de films organosiliciés contenant des fonctions amine. Nous avons étudié l’effet du régime dans lequel opère la décharge sur la production de certaines espèces, telles que CN et CN2. En couplant ces résultats à l’analyse des films réalisés, nous avons pu mettre en évidence le fait que dans un régime filamentaire, le précurseur est fragmenté de manière plus importante. En particulier, les liaisons Si-CH3 sont détruites. Cependant, la quantité d’azote introduite dans le film, qui dépend pour beaucoup de celle de carbone, est plus importante dans le cas d’une décharge de Townsend, et le taux de fonctions amines est plus important. Le taux d’azote dépend également de la nature du substrat. La quantité d’azote introduite dans les films est en effet supérieure dans le cas d’un dépôt sur verre. Aucune explication n’a cependant été apportée à ce phénomène. Des cratères son également apparu dans les films obtenus sur cuivre en régime filamentaire.