Dissertations / Theses: 'Surfaces and Interfaces'

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Carrico, A. S. "Excitations near surfaces and interfaces." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355719.

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Bose, Sumit. "Pattern formation at semiconductor interfaces and surfaces." [S.l.] : [s.n.], 2001. http://edocs.tu-berlin.de/diss/2000/bose_sumit.pdf.

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Heffelfinger, Jason Roy. "Ceramic surfaces, interfaces and solid-state reactions /." Diss., ON-CAMPUS Access For University of Minnesota, Twin Cities Click on "Connect to Digital Dissertations", 1997. http://www.lib.umn.edu/articles/proquest.phtml.

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Liedke, Bartosz. "Ion beam processing of surfaces and interfaces." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-79526.

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Self-organization of regular surface pattern under ion beam erosion was described in detail by Navez in 1962. Several years later in 1986 Bradley and Harper (BH) published the first self-consistent theory on this phenomenon based on the competition of surface roughening described by Sigmund's sputter theory and surface smoothing by Mullins-Herring diffusion. Many papers that followed BH theory introduced other processes responsible for the surface patterning e.g. viscous flow, redeposition, phase separation, preferential sputtering, etc. The present understanding is still not sufficient to specify the dominant driving forces responsible for self-organization. 3D atomistic simulations can improve the understanding by reproducing the pattern formation with the detailed microscopic description of the driving forces. 2D simulations published so far can contribute to this understanding only partially. A novel program package for 3D atomistic simulations called TRIDER (TRansport of Ions in matter with DEfect Relaxation), which unifies full collision cascade simulation with atomistic relaxation processes, has been developed. The collision cascades are provided by simulations based on the Binary Collision Approximation, and the relaxation processes are simulated with the 3D lattice kinetic Monte-Carlo method. This allows, without any phenomenological model, a full 3D atomistic description on experimental spatiotemporal scales. Recently discussed new mechanisms of surface patterning like ballistic mass drift or the dependence of the local morphology on sputtering yield are inherently included in our atomistic approach. The atomistic 3D simulations do not depend so much on experimental assumptions like reported 2D simulations or continuum theories. The 3D computer experiments can even be considered as 'cleanest' possible experiments for checking continuum theories. This work aims mainly at the methodology of a novel atomistic approach, showing that: (i) In general, sputtering is not the dominant driving force responsible for the ripple formation. Processes like bulk and surface defect kinetics dominate the surface morphology evolution. Only at grazing incidence the sputtering has been found to be a direct cause of the ripple formation. Bradley and Harper theory fails in explaining the ripple dynamics because it is based on the second-order-effect 'sputtering'. However, taking into account the new mechanisms, a 'Bradley-Harper equation' with redefined parameters can be derived, which describes pattern formation satisfactorily. (ii) Kinetics of (bulk) defects has been revealed as the dominating driving force of pattern formation. Constantly created defects within the collision cascade, are responsible for local surface topography fluctuation and cause surface mass currents. The mass currents smooth the surface at normal and close to normal ion incidence angles, while ripples appear first at incidence angles larger than 40°. The evolution of bimetallic interfaces under ion irradiation is another application of TRIDER described in this thesis. The collisional mixing is in competition with diffusion and phase separation. The irradiation with He ions is studied for two extreme cases of bimetals: (i) Irradiation of interfaces formed by immiscible elements, here Al and Pb. Ballistic interface mixing is accompanied by phase separation. Al and Pb nanoclusters show a self-ordering (banding) parallel to the interface. (ii) Irradiation of interfaces by intermetallics forming species, here Pt and Co. Well-ordered layers of phases of intermetallics appear in the sequence Pt/Pt3Co/PtCo/PtCo3/Co. The TRIDER program package has been proven to be an appropriate technique providing a complete picture of mixing mechanisms.

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Ramos, Marta Maria Duarte. "Theory of processes at surfaces and interfaces." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305546.

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Goldar, Arach. "X-ray reflection from surfaces and interfaces." Thesis, University of Bath, 2001. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760774.

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Burr, Tracey Alexandra 1967. "Electrical properties of silicon surfaces and interfaces." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9689.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.
Includes bibliographical references (p. 159-168).
This work addresses two scientific challenges associated with diminishing device size. First, alternative surface passivation chemistries are investigated to meet the narrowing process tolerances for high quality silicon surfaces. Second, Si-based light emitting devices are studied to address a longer-term move towards photons instead of electrons for data transfer. A concerted effort is made to engineer environmentally benign solutions to these challenges. Highly effective Si( 100) surface passivation is achieved by immersing wafers in very dilute solutions of methanolic iodine. The electrical quality of Si surfaces is monitored in terms of surface recombination lifetime, employing radio frequency photo conductance decay (rfPCD) measurements. J/methanol treated surfaces are shown to have higher lifetimes and greater air stability than hydrogen terminated surfaces, while retaining comparable planarity and smoothness. Using XPS, UPS, and ATR-FTIR, the identity of the primary passivating surface species is ascertained to be a methoxysilane (Si-OCH3), and the most plausible passivation mechanism is deduced. Our results clearly illustrate the relationship between chemical passivation and electrical passivation. Thin films of visibly emitting silicon nanoparticles are fabricated using a pulsed laser ablation supersonic expansion technique. The electrical and electroluminescence characteristics of devices containing these films are shown to be controlled by carrier transport through the nanoparticulate silicon layer. A conduction mechanism encompassing both geometric and electronic effects most effectively relates the high resistivity with structural properties of the films. The observed temperature dependent PL, EL, and I-V characteristics of the devices are consistent with a model in which carrier transport is controlled by space-charge-limited currents or tunneling through potential barriers on a percolating lattice.
by Tracey Alexandra Burr.
Ph.D.

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Ercole, Ari. "Thin film magnetism at surfaces and interfaces." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624863.

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Abrakhi, Sanae. "Surfaces à mouillabilité modulable." Thesis, Cergy-Pontoise, 2011. http://www.theses.fr/2011CERG0561/document.

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Des matériaux polymères photosensibles ont été élaborés selon trois méthodes différentes : la synthèse de réseaux, la technique de Langmuir-Blodgett et le spin-coating. Les modulations des propriétés de mouillage induites par stimulus lumineux ont été étudiées par mesures dynamiques d'angle de contact et corrélées aux processus photochimiques mis en jeu, isomérisation trans→cis et/ou dimérisation des groupements photosensibles.Deux types de polymères photosensibles ont été synthétisés, un polymère cellulosique portant des groupements cinnamate et des copolymères associant les propriétés photo-induites de groupements azobenzène aux propriétés anti-adhésives de monomères fluorés. La densité de groupements photosensibles a été variée soit par modification de la densité de greffage des cinnamates sur le polymère cellulosique, soit par changement de la composition du copolymère. Les processus photochimiques induits sous irradiation UV ont été étudiés en solution puis au sein des différents matériaux. Après caractérisation des deux types de films élaborés avec ces polymères, films de Langmuir-Blodgett et films spin-coatés, et des matériaux réticulés, les propriétés de mouillage de l'eau et du diiodométhane ont été étudiées avant et après irradiation UV. Les résultats obtenus montrent que la méthode d'élaboration des surfaces et l'environnement des groupements photosensibles jouent un rôle significatif sur les processus photochimiques mis en jeu et les modulations des propriétés de mouillage associées
We report on the elaboration of photosensitive polymer materials using three different methods : synthesis of polymer networks, the Langmuir-Blodgett technique and the spin-coating. The modulation of the photo-induced wetting properties has been studied by dynamic contact angle measurements and correlated to the photochemical processes, trans→cis isomerization and/or dimerization of the photosensitive groups.Two different photosensitive polymers have been synthesized, a cellulosic polymer modified by cinnamate groups and copolymers which combine the photo-induced properties of azobenzene groups and the anti-adhesive properties of fluorinated monomers. The density of photosensitive groups was varied by changing either the grafting density of cinnamate groups in the cellulosic polymer, or the composition of the copolymer. The photochemical processes of these photosensitive polymers were characterized in solution as well as in the different films or materials. After characterization of the two types of films prepared with these polymers, Langmuir-Blodgett and spin-coated films, and of the crosslinked materials, the wetting properties of water and diiodomethane were studied before and after UV irradiation. The results show that the sample preparation and the photosensitive groups environment play a significant role in the involved photochemical processes and the associated wetting properties

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Sternberg, Michael. "The atomic structure of diamond surfaces and interfaces." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963146955.

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Walls, Michael Gerard. "Electron energy-loss spectroscopy of surfaces and interfaces." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254503.

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Lucas, Christopher Andrew. "X-ray scattering studies of surfaces and interfaces." Thesis, University of Edinburgh, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253861.

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Vlachos, Georgios. "Adhesion and dewetting phenomena of surfaces and interfaces." Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414622.

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Lin, Simon Chengchien. "Applications of field theory in surfaces and interfaces." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/12424.

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BEHNAMGMADER, ALIASGHADER. "Proprietes mecaniques des surfaces et interfaces d'implants orthopediques." Paris, ENSAM, 1999. http://www.theses.fr/1999ENAM0018.

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Le but de ce travail est d'etudier l'influence des parametres correspondant a l'etat de, surface comme la rugosite, sur le fonctionnement mecanique des elements utilises pour la prothese de la hanche. Pour cela, deux problemes parmi les plus importants sont retenus : l'usure dans les surfaces articulaires et l'adherence du revetement d'hydroxyapatite sur les protheses de la hanche. Pour les essais de frottement, des parametres relatifs a la profondeur (r a), la largeur et la distance (s m) et la forme (s k) des irregularites du profil de la surface des tetes explantees en ta6v et en cocr sont d'abord etudies. Les deux mecanismes du frottement abrasif et de la fatigue sont detectes par les essais pion - disque, et l'avantage de l'evaluation du coefficient de frottement y est discute. L'endommagement de la surface de l'alliage ta6v et l'influence du contact en mouvement est egalement observe. L'evaluation de l'adherence du depot ceramique de l'hydroxyapatite (hap) sur le substrat en ta6v est precedee par la caracterisation mecanique de la rupture par indentation de l'hap dense. Celui-ci est un materiau fragile dont la tenacite est inferieure a 1,1 mpa. M 0 , 5 et tres sensible a la propagation des fissures laterales avec le temps. Ensuite, le role de l'etat de surface du substrat et de l'epaisseur du revetement sur l'adherence sont etudiees par les observations microscopiques ainsi que des essais d'indentation, d'arrachement et de rayure. La cause la plus importante de la faible adherence (de nature mecanique) est due a la methode de fabrication (torche a plasma). Il s'agit de fissures interfaciales (en premier) et aussi de fissures paralleles a l'interface ou de porosites. D'apres les resultats de ce travail nous preconisons un revetement d'hydroxyapatite d'une epaisseur d'environ 90 m depose par torche a plasma sur un substrat de ta6v grossierement sable (r a = 2,29 0,40 m).

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Tao, Chenggang. "Fluctuations on metal surfaces and molecule/metal interfaces." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7638.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Dept. of Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Cairns, John William. "The interfaces of II-VI/III-V semiconductors." Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296381.

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Patitsas, Stathis Nikos. "Electron wavefunctions at crystal interfaces." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29738.

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A one dimensional analysis of the boundary conditions of the electron energy eigenfunc-tion at a sharp interface between two crystals was made. An attempt to evaluate these conditions in terms of known band structure was made. It was concluded that this cannot be done in general. It was shown, however, that if the interface has the proper symmetry properties, the boundary conditions can be expressed in terms of only one unknown, energy-dependent parameter. It was concluded that setting this parameter equal to one gives boundary conditions which, though more general, are equivalent to the commonly used effective mass boundary conditions when they are applicable. It was concluded from numerical results for the transmission coefficient of the symmetric interface, that in general, these boundary conditions, which depend only on known band structure, do not give a good approximation to the exact answer. Since the energy dependence of the parameter mentioned above is described quite well qualitatively using the nearly free electron approximation or the tight-binding approximation, the applicability of any boundary conditions depending only on band structure can be predicted using these simple theories. The exact numerical results were calculated using the transfer matrix method. It was also concluded that the presence of symmetry in the interface either maximizes or minimizes the transmission coefficient. A tight-binding calculation showed that the transmission coefficient depends on an interface parameter which is independent of band structure. The transmission coefficient is maximized when this parameter is ignored. It was concluded that the effective mass equation is of little use when applied to this problem. Some transfer matrix results pertaining to the barrier and the superlattice were obtained.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

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Lima, Francisco Nogueira. "Interfaces híbridas de estireno sobre silício." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-06102014-115406/.

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Este trabalho trata do estudo teórico atomístico das conformações da molécula de estireno sobre a superfície de Si(100)(2xl):H. Estudamos a molécula fisissorvida e quimissorvida sobre esta superfície. Os cálculos foram realizados através de Dinâmica Molecular Clássica. Nós reparametrizamos o Universal Force Field (UFF) com base em cálculos ab initio para sistemas modelo, e comparação a dados experimentais. Nossos resultados indicam que no processo de fississorção a região de vale da superfície é preferencial, e ocorre formação de agregados de moléculas antes do contato com a superfície. Quando passamos à análise da quimissorção de uma molécula, a região de vale permanece sendo o sítio preferencial para a posição do grupo vinil. Para as conformações de linhas de estireno, a estrutura mais estável tem todas as moléculas dispostas sobre a região de vale (ordenamento tipo \"pilha-1r\"); identificamos também outra estrutura, quase degenerada em energia, na qual o grupo vinileno se dispõe em conformação tipo \"espinha de peixe\", alternando entre a região de vale e sobre o dímero.
In this work we present a theoretical study of ,the conformation of styrene molecules on the Si(100)(2xl):H surface. We studied the conformations for styrene molecules physisorbed and chemisorbed on this surface. The study was conducted by Classical Molecular Dynamics. We performed a re-parametrization of the Universal Force Field (UFF), based on ab initio calculations for model structures, and comparison to experimental data. Our results show that for the physisorbed situations, the styrene molecules preferentially interact with the surface valley. We also identified that the molecules aggregate in clusters before reaching the surface. The valley is again the region of lowest energy for the vinylene position, for chemisorption of a single styrene molecule on the monohydride surface. For systems where we have a styrene layer chemisorbed on the dimer row, the most stable structure has ali the molecules arranged on the valley region o f the surface ( 1r -stack); we find another structure, almost degenerate in energy, in which molecules arrange in a herringbone- like configuration, with the vinylene group alternating between the valley and dimer regions.

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Tallarida, Massimo. "Electronic properties of semiconductor surfaces and metal, semiconductor interfaces." [S.l.] : [s.n.], 2005. http://www.diss.fu-berlin.de/2005/196/index.html.

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Peruffo, Massimo. "Functionalisation of surfaces and interfaces : molecules, particles and crystals." Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/3779/.

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This thesis is concerned with understanding and directing the functionalisation of solid surfaces with materials: molecules, nanoparticles and crystals. Both conducting (electrode) and insulating surfaces are of interest. For molecular functionalisation, a sweep potential procedure has been developed to assist the formation of self assembled monolayers (SAMs) of a ruthenium thiolated complex. Electrochemical investigations were employed to characterised the SAM formed on a platinum electrode. Nanoparticles formation explored two distinct routes. First Pd nanoparticles were successfully formed within ultra-thin Nafion films via impregnation and a chemical reduction method. Morphological investigations utilised atomic force microscopy. The electrocatalytic properties of the nanocomposite material were elucidated for the hydrogen oxidation reaction. The methodology used for the preparation of this nanocomposite material shows promise for applications in sensors and fuel cells. Second, the potential-assisted deposition of pre–formed perthiolated-ß-cyclodextrin-capped Pt nanoparticles method is described. Pt nanoparticles (5 nm diameter) were deposited in a controlled fashion on indium tin oxide and highly oriented pyrolytic graphite electrodes. The Pt nanoparticles formed in this way were electrocatalytically active towards hydrogen generation and oxidation. This new approach for the deposition of metal nanoparticles with controlled surface density provides a new tool for the investigation of electrocatalytic processes. A major focus of the second part of the thesis has been the development of methods to study crystal deposition at extreme supersaturation. For this purpose a delivery system for calcium carbonate at high-supersaturation ion has been coupled with a quartz crystal microbalance and in–situ optical microscopy. The dynamics and quantitative evaluation of calcium carbonate deposition onto foreign solid substrates, and the effect of various additives, are described. Ex– situ studies, scanning electron microscopy and microRaman spectroscopy, allowed the morphological characterisation of the phases deposited. The transformation of ACC to calcite has been explored in details. In the study of additives, a significant finding was that citrate concentration shows a nonmonotonic behaviour on the amount of scale deposited. Fast screening of different additives (polymeric and molecular) and a quantitative ranking of their inhibitory properties on calcium carbonate deposition on a gold surface is described. Molecular and polymeric additives showed different inhibitory mechanisms on the scaling process and the technique employed gave a better insight into their mode of action.

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Capaz, Rodrigo Barbosa 1968. "Ab initio studies of semiconductors : defects, surfaces and interfaces." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10812.

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Zheng, Pengyuan. "Electron Scattering at Surfaces and Interfaces of Transition Metals." Thesis, Rensselaer Polytechnic Institute, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10010793.

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The effect of surfaces on the electron transport at reduced scales is attracting continuous interest due to its broad impact on both the understanding of materials properties and their application for nanoelectronics. The size dependence of for conductor?s electrical resistivity ? due to electron surface scattering is most commonly described within the framework of Fuchs and Sondheimer (FS) and their various extensions, which uses a phenomenological scattering parameter p to define the probability of electrons being elastically (i.e. specularly) scattered by the surface without causing an increase of ? at reduced size. However, a basic understanding of what surface chemistry and structure parameters determine the specularity p is still lacking. In addition, the assumption of a spherical Fermi surface in the FS model is too simple for transition metals to give accurate account of the actual surface scattering effect. The goal of this study is to develop an understanding of the physics governing electron surface/interface scattering in transition metals and to study the significance of their Fermi surface shape on surface scattering. The advancement of the scientific knowledge in electron surface and interface scattering of transition metals can provide insights into how to design high-conductivity nanowires that will facilitate the viable development of advanced integrated circuits, thermoelectric power generation and spintronics. Sequential in situ and ex situ transport measurements as a function of surface chemistry demonstrate that electron surface/interface scattering can be engineered by surface doping, causing a decrease in the ?. For instance, the ? of 9.3-nm-thick epitaxial and polycrystalline Cu is reduced by 11-13% when coated with 0.75 nm Ni. This is due to electron surface scattering which exhibits a specularity p = 0.7 for the Cu-vacuum interface that transitions to completely diffuse (p = 0) when exposed to air. In contrast, Ni-coated surfaces exhibit partial specularity with p = 0.3 in vacuum and p = 0.15 in air, as Cu2O formation is suppressed, leading to a smaller surface potential perturbation and a lower density of localized surface states, yielding less diffuse electron scattering. The localized surface density of states (LDOS) at the Fermi level N(Ef) as a primary parameter determining the surface scattering specularity is further confirmed by a different surface dopant. In particular, the measured sheet resistance of 9-25-nm-thick epitaxial Cu(001) layers increases when coated with dTi = 0.1-4.0 monolayers (ML) of Ti, but decreases again during exposure to 37 Pa of O2. The corresponding changes in ? are a function of dCu and dTi and are due to a transition from partially specular electron scattering at the Cu surface to completely diffuse scattering at the Cu-Ti interface, and the recovery of surface specularity as the Ti is oxidized. X-ray reflectivity and photoelectron spectroscopy indicate the formation of a 0.47?0.03 nm thick Cu2O surface layer on top of the TiO2-Cu2O during air exposure, while density functional calculations of TiOx cap layers as a function of x = 0-2 and dTi = 0.25-1.0 ML show a reduction of N(Ef) by up to a factor of four. This reduction is proposed to be the key cause for the recovery of surface specularity and results in electron confinement and channeling in the Cu layer upon Ti oxidation. Transport measurements at 293 and 77 K confirm the electron channeling and demonstrate the potential for high-conductivity metal nanowires by quantifying the surface specularity parameter p = 0.67?0.05, 0.00?0.05, and 0.35?0.05 at the Cu-vacuum, Cu-Ti, and Cu-TiO2 interfaces. In order to determine the effect of the Fermi surface shape on the size effect, experimental and simulation results are combined to study how the resistivity changes with film thickness dw on monocrystalline W layers with different surface orientation, W(001) and W(110). As the first step of the experiments, the growth of epitaxial W(001) layers on MgO(001) substrates by ultra-high vacuum magnetron sputtering is studied, in order to obtain an alternative W layer orientation in addition to the well-known growth of epitaxial W(011) on Al2O3 substrates. X-ray diffraction ?-2? scans, ?-rocking curves, and pole figures show that 5-400 nm thick W(001) layers grown at Ts = 900 ?C are monocrystalline with a relaxed lattice constant of 3.167?0.001 nm, as determined from high resolution reciprocal space mapping. The magnitude of the residual in-plane compressive strain decreases from -1.2?0.1% to 0.1?0.1% with increasing dw. This is attributed to the glide of threading dislocations which increases the average misfit dislocation length, causing relaxation of the stress associated with differential thermal contraction. X-ray reflectivity measurements indicate smooth surfaces with a root-mean-square surface roughness ?1.0 nm and a roughness exponent of 0.38 for dw below 20 nm. Secondly, the effect of surface roughness on surface scattering is investigated to ensure its contribution to the resistivity size effect is properly included when comparing W films grown on different substrates. In fact it is found the ? of in situ annealed 4-20 nm thick epitaxial W(001) layers grown on MgO(001) samples show weaker dw dependence than that of unannealed samples in vacuum and air at both 295 and 77 K although completely diffuse surface scattering are present on both sets of films. No significant change in the structural quality of the samples after annealing is observed for d ? 20 nm. While a combination of X-ray reflectivity and Atomic Force Microscope study on surface morphology shows flatter surface mounds after annealing. Consequently, in situ annealing treatment is carried out on both epitaxial W(110) and W(001) from dw =4-320 nm to obtain surface with comparable rms roughness and lateral correlation length. Thus the ? increase due to the surface roughness is estimated in similar degree for the two types of films. Finally, a transport model for thin films with anisotropic Fermi surfaces is presented, which includes the effect of electron surface scattering. Simulations done using the calculated W Fermi surface show the resistivity ? to be 1.15-2.23 and 1.21-3.14 times larger than that of bulk W for (011) and (001) oriented thin films, respectively at a layer thickness d = 37.5- 3.75 nm, indicating an orientation dependent surface scattering effect on ?. The resistivity of epitaxial W(110) increases from 5.77?0.03 to 13.24?0.24 ??-cm as d decreases from 320 to 5.7 nm, but increases stronger for epitaxial W(001) from ? = 5.77?0.03 to 24.42?0.58 ??-cm for d = 320 and 4.5 nm. This orientation dependence is quantified with a different effective mean free path lambda(110) = 18.5?0.3 nm vs lambda(001) = 33?0.4 nm at 295 K by fitting using ? vs t with the Fuchs-Sondheimer (FS) model for spherical Fermi surfaces since their surface scattering is found completely diffuse by sequential in situ and ex situ electron transport measurements. Similarly, the ? from simulation can be fitted to obtain another set of lambda(110) and lambda(001) . The ratio lambda(110)/lambda(001) = 0.57?0.01 from simulations, in good agreement with 0.56?0.01 from experiment. The orientation dependent size effect is the result of (1) the projected Fermi surface area along the surface normal and (2) the rate of electrons approaching the surfaces due to the anisotropic electron Fermi velocity distribution along different directions.

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Bigerelle, Maxence. "Caracterisation geometrique des surfaces et interfaces applications en metallurgie." Paris, ENSAM, 1999. http://www.theses.fr/1999ENAM0003.

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Ce travail a pour but d'etudier les relations entre differents mecanismes physiques rencontres en sciences des materiaux et la morphologie des surfaces et interfaces. La signification physique, les methodes numeriques et les artefacts (rayon du palpeur, bruit haute frequence, regression lineaire) du calcul de la dimension fractale sont principalement developpes. Une methode de calcul originale plus precise que les precedentes est creee pour estimer la dimension fractale d'un signal et generalisee a trois dimensions. Les relations entre l'aire et le perimetre d'un objet sont analysees en relation avec les resultats de la bibliographie et critiquees. Nos algorithmes de calculs sont valides sur des courbes theoriques puis appliques a des exemples concrets choisis dans les domaines metallurgiques et des procedes de fabrication : - relations entre brillance et rugosite sur des toles d'acier doux laminees, puis sur des echantillons polis (acier, aluminium, cuivre et etain), - nouveau procede de polissage, - modelisation analytique de la modification d'une interface metallique chauffee dans le vide, - simulation du grossissement de grain par la methode de monte carlo, - grossissement d'un grain d'aluminium en fonction du temps de maintien, - proliferation de cellules osteoblastiques humaines sur un substrat metallique en ta6v. Ces divers exemples montrent que la dimension fractale est un parametre pertinent de caracterisation.

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Vardhireddy, M. "Electronic properties of modified gallium arsenide surfaces and interfaces." Thesis(Ph.D.), University of Poona, 1989. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/6086.

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Cabibil, Hyacinth (Hyacinth Liesl). "Sulfur-induced Corrosion at Metal and Oxide Surfaces and Interfaces." Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc277765/.

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Sulfur adsorbed on metallic and oxide surfaces, whether originating from gaseous environments or segregating as an impurity to metallic interfaces, is linked to the deterioration of alloy performance. This research dealt with investigations on the interactions between sulfur and iron or iron alloy metallic and oxide surfaces under ultrahigh vacuum conditions. Sulfur was either intentionally dosed from a H2S source on an atomically clean metal surface, or segregated out as an impurity from the bulk to the metal surface by annealing at elevated temperatures.

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Steinberger, Audrey Charlaix Elisabeth. "Nanorhéologie écoulement limite et friction à l'interface liquide-solide /." [s.l.] : [s.n.], 2006. http://tel.archives-ouvertes.fr/docs/00/13/42/61/PDF/these_311006.pdf.

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Saad, Nadine. "Caractérisation par ondes acoustiques des surfaces fonctionnalisées." Phd thesis, Université de Valenciennes et du Hainaut-Cambresis, 2012. http://tel.archives-ouvertes.fr/tel-00747257.

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La fonctionnalisation des surfaces permet d'en modifier leur comportement vis-à-vis des propriétés physico-chimiques de fluides. Nous avons restreint notre étude à la caractérisation par méthode acoustique des interfaces microstructurées silicium-fluide pour lesquelles une gravure physique d'un réseau de piliers de petites dimensions a été réalisée. Les propriétés de ces interfaces vis-à-vis des liquides dépendent de la géométrie des gravures, des propriétés du fluide et des conditions d'interaction du fluide avec la surface. Notre objectif a été de confronter des modèles de comportement en terme de mouillabilité de ces surfaces aux mesures des coefficients de réflexion des ondes ultrasonores. Une première étape du travail a consisté à modéliser le coefficient de réflexion d'une onde ultrasonore incidente sur une surface microtexturée en fonction de l'état du liquide sur la surface. Deux états physiques caractéristiques ont étés étudiés : l'état où le liquide reste au sommet des piliers (état Cassie) et celui où le liquide pénètre dans le réseau de piliers (état Wenzel). Deux modèles numériques ont été développés : le premier repose sur la modélisation par éléments finis utilisant COMSOL MULTIPHYSICS et le second modèle numérique utilise une méthode explicite aux différences finies.La technique expérimentale est fondée sur une méthode de mesure du coefficient de réflexion électrique d'un transducteur ultrasonore haute fréquence à l'aide d'un analyseur de réseau, qui permet après traitement d'en déduire le coefficient de réflexion à l'interface.Les résultats originaux obtenus démontrent qu'une onde acoustique de compression est sensible à l'état d'un liquide sur une surface microtexturée.

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29

Szabo, Tamas. "Energy transfer at gas-liquid interface towards energetic materials /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4797.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on February 29, 2008) Vita. Includes bibliographical references.

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30

Baranowski, Roman. "The properties of polymer/solvent systems at surfaces and interfaces." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25767.pdf.

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31

Jönsson, Stina Karin Maria. "Towards flexible organic electronics : photoelectron spectroscopy of surfaces and interfaces /." Linköping : Univ, 2004. http://www.bibl.liu.se/liupubl/disp/disp2004/tek895s.pdf.

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32

Hamid, Abd Rani bin Abd. "Phonon scattering at surfaces and interfaces studied using heat pulses." Thesis, Lancaster University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235637.

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33

Eder, Katja Daniela. "Surfaces and interfaces in nano-scale and nano-structured materials." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17217.

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In this thesis, advanced characterisation methods, including atom probe tomography (APT) and transmission Kikuchi diffraction (TKD) were employed to study surface and interfaces in a range of nano-scale and nano-structured materials. These techniques were used to measure solute segregation towards grain boundaries and to explore the relationship between grain boundary segregation and grain boundary mobility. APT was also used to characterise the structure of nanoparticles used as catalysts, and the adsorption behaviour of sulphur on catalytic surfaces, to gain more information about the structure-activity relationships, and deactivation processes. This research included the development and improvement of new and existing APT sample preparation techniques, conducting the experiments, and data analysis. The first part of this thesis is concerned with nanocrystalline alloys processed by severe plastic deformation. In the second part the exceptional hardening of an 316L austenitic steel during annealing was also investigated using APT. This thesis also concentrated on the study of nanoparticles for catalysis via APT. Systematic investigations of different APT sample preparation techniques were performed in order to find a way of producing reproducible and reliable specimens. Different acquisition parameters, substrates and coatings were tested to improve the APT data quality. Experiments were conducted in which needles were dipped in thiophene. Here the aim was to investigate the phenomenon of sulphur poisoning by using APT to investigate how thiophene bonds with different metal substrates. A glovebag setup was designed for the transfer of APT samples in a controlled environment, to avoid oxidation of the samples. This allowed the comparison of oxidised and un-oxidised specimen states. In the last part of this thesis, the accuracy of crystallographic information contained within APT datasets was verified for the first time by comparing the datasets to TKD measurements.

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34

Van, Wyck Neal Edward. "MULTIPHOTON SPECTROSCOPY OF THIN FILMS AND SURFACES (NONLINEAR, WAVEGUIDES, INTERFACES)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/291294.

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35

Walliser, André. "Caractérisation des interactions liquide-fibre élementaire par mouillage." Mulhouse, 1992. http://www.theses.fr/1992MULH0248.

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Un système expérimental, Microwetting (marque Du Pont de Nemours), a été développé dans le but de déterminer, localement et avec précision, l'énergie de surface de fibres élémentaires par mouillage. Un faible volume de liquide est mis en contact avec une fibre en un endroit sélectionné de la surface. En l'absence d'étalement spontané, se forme alors une goutte de liquide qui adopte une conformation soit axisymétrique soit non-axisymétrique par rapport à l'axe de la fibre. Dans le premier cas, l'angle de contact entre la goutte et la fibre est calculé grâce à une équation qui relie l'angle au diamètre de la fibre, à la longueur et au diamètre de la goutte. Dans le cas d'une conformation non-axisymétrique, nous avons établi un modèle fondé sur la projection mathématique, aux volumes de gouttes nuls, des variations de paramètres géométriques de la goutte. Ce modèle conduit à la détermination de l'angle de contact représentatif des interactions à l'interface. Ainsi les mesures par mouillage sur fibres élémentaires permettent le calcul des composantes dispersive et non-dispersive de l'énergie superficielle quelles que soient les manifestations macroscopiques des interactions solide-liquide

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36

Vivek, Manali. "Etats topologiques aux surfaces de perovskites d'oxydes de métaux de transition." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS216/document.

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Le sujet de la topologie dans les oxydes, en particulier à la surface des oxydes de pérovskite comme SrTiO₃, ou à l'interface de LaA1O₃ / SrTiO₃ sera étudié dans cette thèse. Les deux matériaux, à leurs surfaces orientées (001), contiennent un état métallique limité à quelques nanomètres de la surface. De plus, nous montrerons qu'il existe certains croisements de trois bandes autour desquelles des perturbations vont provoquer l'apparition d'un spectre de bandes inversées et gappées. Ceux-ci conduiront à des états de bord topologiques qui peuvent être détectés via la supraconductivité induite comme dans le cas des puits quantiques topologiques ou des nanofils des supraconducteurs-semi-conducteurs. Ensuite, la surface orientée (111) de LaA1O₃ / SrTiO₃ sera étudiée lorsque les mesures de transport de Hall révèlent une transition de un à deux porteurs par dopage électrostatique. Une explication basée sur un modèle de liaisons fortes incluant des corrélations U de Hubbard sera proposée, ce qui donnera lieu à des croisements de bandes entre les sous-bandes favorisant les états topologiques. Enfin, une étude ab-initio de CaTiO₃ sera effectuée pour expliquer l'état métallique qui existe à sa surface (001) orientée et pour prédire le magnétisme dans le système. CaTiO₃ est différent des autres composés étudiés précédemment, en raison de la grande rotation et de l'inclinaison des octaèdres d'oxygène entourant le Ti, ce qui complique les faits. La structure avec et sans lacunes d'oxygène sera étudiée en profondeur pour fournir des détails sur la bande de conduction et leurs caractères orbitaux
The subject of topology in oxides, in particular at the surfaces of perovskite oxides like SrTiO₃, or at the interface of LaA1O₃/SrTiO₃ will be investigated in this thesis. Both compounds, at their (001) oriented surfaces, contain a metallic state confined to a few nanometers at the surface. In addition, we will show that there exist certain three band crossings around which perturbations will cause an inverted and gapped band spectrum to appear. These will lead to topological edge states which can be detected via induced superconductivity as in the case of topological quantum wells or superconductor-semiconductor nanowires. Next, the (111) oriented surface of LaA1O₃/SrTiO₃ will be studied where Hall transport measurements reveal a one to two carrier transition via electrostatic doping. An explanation based on a tight binding modelling including Hubbard U correlations, will be proposed which will give rise to band crossings between sub-bands promoting topological states. Finally, an ab-initio study of CaTiO₃ will be performed to explain the metallic state which exists at its (001) oriented surface and to predict magnetism in the system. CaTiO₃ is different from the other compounds studied previously, due to the large rotation and tilting of the oxygen octahedra surrounding the Ti, which complicates the picture. The structure with and without oxygen vacancies will be studied in-depth to provide details about the conduction band and their orbital characters

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37

Williams, M. P. "Computations on static and dynamic models of solid surfaces." Thesis, De Montfort University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372059.

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38

Béal, Ludovic. "Contrôle des interfaces dans les films nanocomposites." Chambéry, 2005. http://www.theses.fr/2005CHAMS031.

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L'objectif de ce travail consiste à étudier l'influence de copolymères à blocs sur les propriétés de films nanocomposites composés d'une matrice de polyméthacrylate de butyle (PBMA) renforcée par des nanoparticules de silice, réalisés par mélange de dispersions aqueuses. Pour cela, nous avons dans un premier temps réalisé la synthèse d'une série de copolymères à blocs amphiphiles composés de méthacrylate de butyle et d'acide méthacrylique par polymérisation anionique et modification thermique. Les solutions aqueuses micellaires de ces différents copolymères blocs ont été caractérisées par résonance magnétique nucléaire, par diffusion de rayonnements (lumière et neutrons), par chromatographie d'exclusion stérique et par des mesures de tension superficielle. Le comportement des copolymères à blocs à l'interface eau/latex est étudié par adsorption des copolymères à blocs à la surface d'un latex, par polymérisation en émulsion et par des tests de stabilité colloïdale. Enfin, les relations entre morphologie et propriétés viscoélastiques sont étudiées sur les films nanocomposites en fonction du taux de silice, des conditions de filmification, de la teneur et de la composition des copolymères à blocs
This work aims at studying the influence of block copolymers on properties of nanocomposite films composed of a poly(butyl methacrylate) matrix reinforced by silica nanoparticles, realized by mixing aqueous dispersions. First, a series of amphiphilic block copolymers composed of butyl methacrylate and methacrylic acid has been synthesized by anionic polymerization and thermal treatment. Aqueous micellar solutions of block copolymers have been characterized by nuclear magnetic resonance, by scattering techniques (Iight, neutron), by steric exclusion chromatography and by surface tension measurements. The behavior of block copolymers at latex/water interface was studied by adsorption of block copolymers at latex surface, by emulsion polymerization and by test of colloidal stability. Finally, the relationships between morphology and viscoelastic properties are studied on nanocomposite films as a function of silica content, fraction and composition of block copolymers

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39

Bouali, Bachir. "Contribution à l'étude des phénomènes de mouillage pour la caractérisation des surfaces et interfaces : maîtrise de la physico-chimie et de la morphologie des surfaces pour régler les propriétés fonctionnelles des interfaces : applications industrielles." Lyon 1, 1998. http://www.theses.fr/1998LYO10132.

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La maitrise du comportement d'une surface est un element important qui intervient dans divers processus technologiques et biologiques tels que la lubrification, l'usure, l'adhesion, la glisse, la detergence, l'adsorption des proteines l'etude des phenomenes a l'interface est determinante pour l'optimisation de ces processus. Le mouillage peut etre considere comme un outil d'investigation pour etudier les proprietes d'une telle interface et notamment les proprietes d'usage caracteristiques de chaque domaine d'application. Dans le present travail, nous avons exploite differentes approches de la mouillabilite aussi bien pour la description du liquide mouillant que du solide mouille. Dans un premier temps, nous nous sommes attaches a decrire, les interactions moleculaires a l'interface liquide - solide et a evaluer la pertinence les differents modeles proposes pour estimer l'energie de surface du solide. Nous avons ensuite examine les relations entre la topographie de la surface solide et les angles de contact a l'aide d'une approche pluridisciplinaire originale faisant intervenir les aspects morphologiques et physico-chimiques de cette surface. La partie liquide de l'interface a ete prise en compte en etudiant le comportement au mouillage de differents liquides sur des surfaces solides connues et bien caracterisees. Enfin, nous avons etudie l'hysteresis de mouillage a partir du comportement dynamique de gouttes de liquide decrochant sur une surface inclinable. L'ensemble des travaux exposes constitue une contribution a la caracterisation de l'interface liquide-solide et propose une methodologie generale d'approche de cette interface.

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40

Nunnery, Grady A. "The influence of surface curvature on polymer behavior at inorganic surfaces." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33929.

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Nanoscale surfaces were examined in order to determine the influence of surface curvature on polymer behavior at polymer-ceramic interfaces, as well as the influence of nanoparticles in cellulosic media. Poly(methyl methacrylate) and block copolymers thereof were adsorbed onto porous alumina substrates of various pore sizes in order to determine how polymer and copolymer adsorption behavior at nanoscale surfaces differs from adsorption onto flat surfaces. It was determined that chain density on concave surfaces dramatically decreases as curvature increases in much the same way that it does on convex surfaces (e.g. on the surface of nanoparticles), and physical models are provided to explain this similarity. Diblock copolymer adsorption is observed to vary dramatically with solvent quality and block asymmetry and can be correlated with the surface curvature very similarly to the adsorptive behavior of homopolymers on those same surfaces. The addition of nanoparticles to cellulosic media was investigated as a means to significantly modify the properties of cellulosic composites with minimal additions of nanoparticles. Although cellulose is among the most abundant polymers on earth, its primary uses are limited to bulk commodity goods, such as paper and textiles. This work demonstrates a simple means to control cellulosic fluid viscosity, thereby increasing the versatility of these biopolymers in additional applications with higher value-added potential. The formation of iron-cellulosic nanocomposites by the in-situ thermolysis of metal carbonyls to form metallic nanoparticles was performed and was analyzed by viscometry among other techniques. It was determined that the nanocomposites that were formed exhibited significantly increased viscosity, up to the point of gelation. Additionally, an introduction to the expansive field of nanocomposites is provided, including how and why composite properties change abruptly as filler size approaches the nanoscale. An extensive background on this diverse field as it relates to the current work is provided with an emphasis on cellulosic nanocomposites and the dependence of curvature on polymer-surface interactions. A detailed account of the experimental work relevant to this work is provided, including materials and characterization methods. Future work is proposed for both cellulosic nanocomposites as well as for curvature-dependent polymer adsorption. Finally, conclusions are drawn from the entire work and its implications to the greater field of nanocomposites.

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41

Liedke, B. "Ion beam processing of surfaces and interfaces – Modeling and atomistic simulations." Helmholtz-Zentrum Dresden-Rossendorf, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-85366.

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Self-organization of regular surface pattern under ion beam erosion was described in detail by Navez in 1962. Several years later in 1986 Bradley and Harper (BH) published the first self-consistent theory on this phenomenon based on the competition of surface roughening described by Sigmund’s sputter theory and surface smoothing by Mullins-Herring diffusion. Many papers that followed BH theory introduced other processes responsible for the surface patterning e.g. viscous flow, redeposition, phase separation, preferential sputtering, etc. The present understanding is still not sufficient to specify the dominant driving forces responsible for self-organization. 3D atomistic simulations can improve the understanding by reproducing the pattern formation with the detailed microscopic description of the driving forces. 2D simulations published so far can contribute to this understanding only partially. A novel program package for 3D atomistic simulations called trider (TRansport of Ions in matter with DEfect Relaxation), which unifies full collision cascade simulation with atomistic relaxation processes, has been developed. The collision cascades are provided by simulations based on the Binary Collision Approximation, and the relaxation processes are simulated with the 3D lattice kinetic Monte-Carlo method. This allows, without any phenomenological model, a full 3D atomistic description on experimental spatiotemporal scales. Recently discussed new mechanisms of surface patterning like ballistic mass drift or the dependence of the local morphology on sputtering yield are inherently included in our atomistic approach. The atomistic 3D simulations do not depend so much on experimental assumptions like reported 2D simulations or continuum theories. The 3D computer experiments can even be considered as ’cleanest’ possible experiments for checking continuum theories. This work aims mainly at the methodology of a novel atomistic approach, showing that: (i) In general, sputtering is not the dominant driving force responsible for the ripple formation. Processes like bulk and surface defect kinetics dominate the surface morphology evolution. Only at grazing incidence the sputtering has been found to be a direct cause of the ripple formation. Bradley and Harper theory fails in explaining the ripple dynamics because it is based on the second-order-effect ‘sputtering’. However, taking into account the new mechanisms, a ‘Bradley-Harper equation’ with redefined parameters can be derived, which describes pattern formation satisfactorily. (ii) Kinetics of (bulk) defects has been revealed as the dominating driving force of pattern formation. Constantly created defects within the collision cascade, are responsible for local surface topography fluctuation and cause surface mass currents. The mass currents smooth the surface at normal and close to normal ion incidence angles, while ripples appear first at θ ≥ 40°. The evolution of bimetallic interfaces under ion irradiation is another application of trider described in this thesis. The collisional mixing is in competition with diffusion and phase separation. The irradiation with He+ ions is studied for two extreme cases of bimetals: (i) Irradiation of interfaces formed by immiscible elements, here Al and Pb. Ballistic interface mixing is accompanied by phase separation. Al and Pb nanoclusters show a self-ordering (banding) parallel to the interface. (ii) Irradiation of interfaces by intermetallics forming species, here Pt and Co. Well-ordered layers of phases of intermetallics appear in the sequence Pt/Pt3Co/PtCo/PtCo3/Co. The trider program package has been proven to be an appropriate technique providing a complete picture of mixing mechanisms.

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42

Treske, Uwe. "Valence changes at interfaces and surfaces investigated by X-ray spectroscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-162589.

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In this thesis valence changes at interfaces and surfaces of 3d and 4f systems are investigated by X-ray spectroscopy, in particular X-ray photoemission (XPS), X-ray absorption (XAS) and resonant photoemission spectroscopy (ResPES). The first part addresses the electronic properties of the oxides LaAlO3, LaGaO3 and NdGaO3 grown by pulsed laser deposition on TiO2-terminated SrTiO3 single crystals along (001)-direction. These polar/non-polar oxide interfaces share an insulator to metal phase transition as a function of overlayer thickness including the formation of an interfacial two dimensional electron gas. The nature of the charge carriers, their concentration and spatial distribution, and the band alignment near the interface are studied in a comparative manner and evaluated quantitatively. Irrespective of the different overlayer lattice constants and bandgaps, all the heterostructures behave similarly. Rising Ti3+ concentration is monitored by Ti 2p XPS, Ti L-edge XAS and by resonantly enhanced Ti 3d excitations in the vicinity of EF (ResPES) when the layer number n increases. This indicates that the active material is in all cases a near interface SrTiO3 layer of 4nm thickness. Band bending in SrTiO3 occurs but no electric field is detected inside the polar overlayers. Essential aspects of the findings are captured by scenarios where the polar forces are alleviated by surface defect creation or the separation of photon generated electron-hole pairs in addition to the electronic reconstruction at n = 4 unit cells layer thickness. Furthermore, deviations from an abrupt interface are found by soft X-ray photoemission spectroscopy which may affect the interface properties. The surface sensitivity of the measurements has been tuned by varying photon energy and emission angle. In contrast to the core levels of the other elements, the Sr 3d line shows an unexpected splitting for higher surface sensitivity, signaling the presence of a second strontium component. From a quantitative analysis it is concluded that during the growth process a small amount of Sr atoms diffuse away from the substrate and segregate at the surface of the heterostructure, possibly forming strontium oxide. In the second part of this thesis the heavy fermion superconductors CeMIn5 (M = Co, Rh, Ir) are investigated by temperature- and angle-dependent XPS. In this material class the subtle interplay between localized Ce 4f and itinerant valence electrons dominate the electronic properties. The Ce 3d core level has a very similar shape for all three materials and is indicative of weak f-hybridization. The spectra are analyzed using a simplified version of the Anderson impurity model, which yields a Ce 4f occupancy that is larger than 0.9. The temperature dependence shows a continuous, irreversible and exclusive broadening of the Ce 3d peaks, due to oxidation of Ce at the surface
In der vorliegenden Dissertation werden Valenzänderungen an Grenzflächen und Oberflächen mittels Verfahren der Röntgenspektroskopie untersucht, zu denen die Röntgenphotoelektronen- (XPS), die Röntgenabsorptions- (XAS) und die resonante Photoelektronenspektroskopie (ResPES) gehören. Kapitel 3 behandelt die elektronischen Eigenschaften der Oxide LaAlO3, LaGaO3 und NdGaO3, welche mittels Laserdeposition (PLD) auf TiO2-terminierte SrTiO3 Einkristalle entlang (001)-Richtung gewachsen wurden. Diese polaren/nicht-polaren Oxidgrenzflächen weisen einen Isolator-Metall Phasenübergang als Funktion der Schichtdicke auf, bei dem sich ein zwei dimensionales Elektronengas an der Grenzfläche bildet. Die Eigenschaften dieser Ladungsträger, deren Konzentration und räumliche Ausdehnung, sowie der Verlauf der Energiebänder an der Grenzfläche werden vergleichend untersucht und quantitativ bestimmt. Es wird gezeigt, dass sich die drei untersuchten Grenzflächen, trotz unterschiedlicher Gitterkonstanten und Energiebandlücken, ähnlich verhalten. Das mit der Schichtdicke ansteigende Ti3+ Signal wird im Ti 2p XPS, Ti L-Kante XAS und durch die resonant verstärkten Ti 3d Anregungen nahe EF (ResPES) nachgewiesen. Daraus lässt sich schlussfolgern, dass in allen Fällen eine SrTiO3 Schicht mit einer Dicke von 4nm der eigentlich aktive Bereich ist. Im SrTiO3 tritt eine Bandverbiegung auf, ein elektrisches Feld in der polaren Deckschicht kann jedoch nicht nachgewiesen werden. Grundlegende Aspekte dieser Ergebnisse sind in einem Szenario vereinbar, bei dem die polaren Kräfte durch die Entstehung von Oberflächendefekten, durch die Trennung von photoneninduzierten Elektronen-Lochpaaren und durch eine elektronische Umordnung bei 4 uc Schichtdicke eliminiert werden. Des Weiteren werden Abweichungen von einer abrupten Grenzfläche mittels weich-Röntgenphotoelektronenspektroskopie festgestellt, die die Grenzflächeneigenschaften beeinflussen können. Für oberflächenempfindlichere Messbedingungen zeigt die Sr 3d Anregung, im Gegensatz zu Rumpfniveaus anderer Elemente, eine unerwartete Aufspaltung, was nur durch das Vorhandensein einer zweiten chemischen Strontiumkomponente zu erklären ist. Aus quantitativen Betrachtungen lässt sich schließen, dass einige Strontiumatome während des Wachstums an die Oberfläche diffundieren und möglicherweise Strontiumoxid gebildet wird. Der zweite Schwerpunkt der vorliegenden Arbeit ist die Untersuchung von Schwer-Fermionen Supraleitern CeMIn5 (M = Co, Rh, Ir) mittels temperatur- und winkelabhängiger XPS. Bei dieser Materialklasse dominiert das feine Zusammenspiel zwischen lokalisierten Ce 4f und frei beweglichen Leitungselektronen die elektronischen Eigenschaften. Das Ce 3d Rumpfniveauspektrum besitzt für die drei Materialien eine sehr ähnliche Form, die auf eine schwache f-Hybridisierung schließen lässt. Die Spektren werden mittels einer vereinfachten Version des Anderson-Impurity Modells analysiert, wobei sich eine Ce 4f Besetzung von mehr als 0,9 ergibt. Die Temperaturabhängigkeit zeigt eine kontinuierliche und irreversible Verbreiterung ausschließlich für die Ce 3d Anregung, dieser Umstand kann einer Oxidation der reaktiven Ceratome an der Oberfläche zugeordnet werden

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43

Gutmann, Sebastian. "Electronic Structure Characterization of Nanocrystalline Surfaces and Interfaces with Photoemission Spectroscopy." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3137.

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In this study, photoemission spectroscopy (PES) was used to investigate the electronic properties of nanocrystalline titanium dioxide (TiO2), zinc oxide (ZnO), and cadmium selenide (CdSe). Electrospray deposition technique enabled the preparation of thin films in vacuum from a dispersion prepared outside the vacuum chamber. This method also allowed the step-wise formation of interfaces and the monitoring of the evolution of the electronic structure with intermittent PES characterization. The work function of nanocrystalline TiO2 and ZnO was measured with ultraviolet photoemission spectroscopy (UPS) and low-intensity x-ray photoemission spectroscopy (LIXPS). Measurements on environmentally contaminated surfaces revealed an instantaneous and permanent work function decrease of 0.3-0.5 eV upon exposure to ultraviolet radiation during a UPS measurement. The work function reduction is likely to be related to the formation of a surface dipole caused by the photo-chemical hydroxylation of surface defects. This phenomenon was further investigated with regard to its influence on the electronic structure of the indium tin oxide (ITO)/TiO2 interface found in dye-sensitized solar cells. The experiments suggest that UV radiation can cause a small but significant change of the charge injection barriers at the interface. The determined band line-ups revealed electron injection barriers of ~0.3-0.5 eV, while UV radiation caused an increase of about 0.15 eV. This might have the potential to further impede electron transfer to the ITO electrode and affect the performance of solar cell device. Another type of photovoltaic cell using nanocrystalline material is a heterojunction bulk solar cell. Conversion efficiencies of such devices are currently only about 3% due to the inefficient charge separation at interfaces formed by blending organic and inorganic material. An approach to improve efficiencies in such devices is the use of covalently bonded conductive polymer/inorganic hybrid nanocrystals. In this study a prototypical model system was investigated with PES with the aim to develop a measurement protocol that allows the determination of electronic properties for such hybrid materials. The comparison of the relative core-level binding energies of the organics-functionalized CdSe nanocrystal compared to the ligand-free CdSe nanocrystal and the arylselenophosphate ligand material enabled the determination of the electronic structure at the interface. Core-level measurements support the hypothesis that the Se functionality of the organic ligand coordinates to the Cd sites on the nanopthesis surface.

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44

Hudson, John Matthew. "Specular and diffuse X-ray scattering studies of surfaces and interfaces." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5516/.

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The behaviour of thin film semiconducting and magnetic devices depends upon the chemical and physical status of the as-grown structure. Since the dimensions of many devices can be in the Angstrom and nanometre region, characterisation techniques capable of measuring chemical and physical parameters in this regime are necessary if an understanding of the effect of specimen structure on observed properties is to be achieved. This thesis uses high resolution x-ray scattering techniques to characterise sub-micron layered structures of semiconducting and magnetic materials. Double crystal diffraction is routinely employed in the semiconductor industry for the on line inspection of sample quality. While material parameters such as sample perfection and layer composition may be rapidly deduced, the non-destructive measurement of layer thickness is more difficult (particularly for multilayered samples) and lengthy simulation procedures are often necessary to extract the thickness information from a double crystal diffraction profile. However, for semiconductor structures which act as Bragg case interferometers, oscillations (known as thickness fringes) appear in the diffracted profile. The period of these fringes can be directly related to layer thickness. Attempts to Fourier transform diffraction data, in order to automatically extract the frequency" of thickness fringes, have previously been only partially successful. It is shown that the relatively weak intensity of the thickness fringes and the presence of the substrate peak in the analysed diffraction data, drastically reduce the quality of the subsequent Fourier transform. A procedure for the manipulation of diffraction data is suggested, where an "average” envelope is fitted to the thickness fringes and used to normalise the data. The application of an auto-correlation is shown to further increase the quality of the Fourier transform of the normalised data. The application of Fourier transform techniques to the routine analysis of double crystal diffraction data is discussedA novel technique for the measurement of absolute lattice parameters of single crystals is presented, which is capable of determining lattice constants with an absolute accuracy of around 2 parts in 10(^5). The technique requires only the use of a conventional triple crystal diffractometer with motorised 20 circle movement and the provision for a fine, precise rocking motion of the analyser. To demonstrate the technique, exemplary measurements on GaAs and InAs crystals are presented. Triple crystal diffi-action analysis has been performed on three material systems of current technological interest; the Hg(_1-x)Mn(_x)Te on GaAs, the Cd(_1-x)Hg(_x)Te on CdTe/Cd(_1-x)Zn(_x)Te and the low temperature grown GaAs systems. Studies on the Hg(_1-x)Mn(_x)Te on GaAs system reveal that the principal contribution to the rocking curve widths of layers grown using the direct alloy growth (DAG) method, arise from the tilt (i.e., mosaicity) of layer sub-grains. This finding is confirmed by double crystal topography which shows that the layers are highly mosaic with a typical grain size of (130±5)µm. Topographic studies of Hg(_1-x)Mn(_x)Te on GaAs, grown using the interdiffused multilayer process (IMP), show that sample quality is significantly improved with single crystal material being produced using this growth method. Triple crystal diffraction studies of the Cd(_1-x)Hg(_x)Te on CdTe/Cd(_0.96)Zn(_0.04)Te systems reveal several findings. These are that the main contribution to rocking curve widths is from lattice tilts and that the tilt distribution increases as the layer thickness decreases. Further, the quality of the Cd(_0.96)Zn(_0.04)Te substrate analysed is superior to that of the CdTe and that Cd(_1-x)Hg(_x)Te layers grown on Cd(_0.96)Zn(_0.04)Te substrates are generally of a higher quality than those grown on CdTe. Triple crystal analysis of MBE and ALE grown GaAs films, deposited at low growth temperatures, show that, at equivalent temperatures, superior quality films are grown by the ALE technique. Narrow lattice dilation and tilt distributions are reported for GaAs films grown at temperatures as low as 300ºC by the ALE method. While diffraction techniques are highly suitable for the study of relatively perfect crystalline material, they are not appropriate to the analysis of heavily dislocated or even amorphous specimens. This is not the case for the Grazing Incidence X-Ray Reflectivity (GIXR) technique, whose sensitivity is not dependent upon sample structure. The GIXR technique is currently attracting increasing interest following the development of commercial instruments. In this thesis, GIXR has been used to probe the layer thickness and interfacial roughness of a series of magnetic multilayer samples and Si/Si(_x)Ge(_1-x) superlattices. The technique is shown to be capable of measuring layer thickness to an accuracy of one monolayer. Modelling of specular GIXR data for the Si/Si(_x)Ge(_1-x) superlattices has shown that the magnitude of interfacial roughness is different for the two types of interface within the high Ge content superlattice samples, the Si(_x)Ge(_1-x)→Si interface possessing a long range sinusoidal roughness of (0.9±0.3)nm, in addition to die short range roughness of (0.5±0.2)nm present at all interfaces. By collecting the diffuse scatter from a GIXR experiment, conformal, or correlated, roughness has been observed in both the multilayer and superlattice samples.

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45

Cocks, Ian David. "Titanium dioxide surfaces and interfaces studied using ESDIAD, LEED and STM." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366351.

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46

Liedke, B. "Ion beam processing of surfaces and interfaces – Modeling and atomistic simulations." Helmholtz-Zentrum Dresden-Rossendorf, 2011. https://hzdr.qucosa.de/id/qucosa%3A22148.

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Self-organization of regular surface pattern under ion beam erosion was described in detail by Navez in 1962. Several years later in 1986 Bradley and Harper (BH) published the first self-consistent theory on this phenomenon based on the competition of surface roughening described by Sigmund’s sputter theory and surface smoothing by Mullins-Herring diffusion. Many papers that followed BH theory introduced other processes responsible for the surface patterning e.g. viscous flow, redeposition, phase separation, preferential sputtering, etc. The present understanding is still not sufficient to specify the dominant driving forces responsible for self-organization. 3D atomistic simulations can improve the understanding by reproducing the pattern formation with the detailed microscopic description of the driving forces. 2D simulations published so far can contribute to this understanding only partially. A novel program package for 3D atomistic simulations called trider (TRansport of Ions in matter with DEfect Relaxation), which unifies full collision cascade simulation with atomistic relaxation processes, has been developed. The collision cascades are provided by simulations based on the Binary Collision Approximation, and the relaxation processes are simulated with the 3D lattice kinetic Monte-Carlo method. This allows, without any phenomenological model, a full 3D atomistic description on experimental spatiotemporal scales. Recently discussed new mechanisms of surface patterning like ballistic mass drift or the dependence of the local morphology on sputtering yield are inherently included in our atomistic approach. The atomistic 3D simulations do not depend so much on experimental assumptions like reported 2D simulations or continuum theories. The 3D computer experiments can even be considered as ’cleanest’ possible experiments for checking continuum theories. This work aims mainly at the methodology of a novel atomistic approach, showing that: (i) In general, sputtering is not the dominant driving force responsible for the ripple formation. Processes like bulk and surface defect kinetics dominate the surface morphology evolution. Only at grazing incidence the sputtering has been found to be a direct cause of the ripple formation. Bradley and Harper theory fails in explaining the ripple dynamics because it is based on the second-order-effect ‘sputtering’. However, taking into account the new mechanisms, a ‘Bradley-Harper equation’ with redefined parameters can be derived, which describes pattern formation satisfactorily. (ii) Kinetics of (bulk) defects has been revealed as the dominating driving force of pattern formation. Constantly created defects within the collision cascade, are responsible for local surface topography fluctuation and cause surface mass currents. The mass currents smooth the surface at normal and close to normal ion incidence angles, while ripples appear first at θ ≥ 40°. The evolution of bimetallic interfaces under ion irradiation is another application of trider described in this thesis. The collisional mixing is in competition with diffusion and phase separation. The irradiation with He+ ions is studied for two extreme cases of bimetals: (i) Irradiation of interfaces formed by immiscible elements, here Al and Pb. Ballistic interface mixing is accompanied by phase separation. Al and Pb nanoclusters show a self-ordering (banding) parallel to the interface. (ii) Irradiation of interfaces by intermetallics forming species, here Pt and Co. Well-ordered layers of phases of intermetallics appear in the sequence Pt/Pt3Co/PtCo/PtCo3/Co. The trider program package has been proven to be an appropriate technique providing a complete picture of mixing mechanisms.

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47

M'Passi-Mabiala, Bernard. "Relaxation et magnetisme des surfaces et interfaces des metaux de transition." Université Louis Pasteur (Strasbourg) (1971-2008), 1996. http://www.theses.fr/1996STR13183.

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Nous avons dans le cadre de la theorie de la fonctionnelle de la densite locale derive rigoureusement une expression generale de la variation de l'energie totale d'un systeme metallique au premier ordre par rapport aux deplacements atomiques. Nous tenons compte dans notre modele de toutes les contributions a l'energie notamment les contributions de bande, de coulomb, d'echange et correlation ainsi des termes ioniques. L'etude du mecanisme de la relaxation de surface en liaisons fortes conduit a un changement de signe de la contribution des electrons d au champ de forces quand on va du milieu en fin de serie. Ce changement est relie a l'augmentation du terme repulsif de la force, qui depend fortement de la structure electronique au niveau de fermi. Nous obtenons dans un schema classique des liaisons fortes d une relaxation vers l'exterieur pour les surfaces (001) de rh, pd et ni en accord avec les resultats experimentaux et une contraction pour les surfaces (001) du fe et du cr paramagnetiques. L'etude des surfaces (001) du fe ferromagnetique et du cr antiferromagnetique en utilisant l'hamiltonien de hubbard pour la structure electronique conduit a une contraction de surface ; les moments magnetiques correspondants sont deduits d'une maniere autocoherente. On remarque en compraison avec l'etat non relaxe une chute drastique du moment magnetique a la surface (001) du cr ; la variation du moment magnetique pour le fe n'est pas significative. L'etude du magnetisme gele a l'interface cr/v montre la forte influence de la face cristallographique: les investigations sur des films cr#3v#1 presentent un couplage antiferro par plan pour les faces (001), (111) et antiferro dans le pour la face (011). L'influence de l'epaisseur des couches v adsorbees est discutee

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Bourdoucen, Hadj. "Etude des surfaces d'InP et des interfaces InP-isolant par photoluminescence." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376033378.

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49

Gray, Jeremy Jason. "Optical studies of surfaces and interfaces in UHV and electrochemical environments /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.

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50

Mkhonto, Donald. "Computer simulation study of apatite mineral surfaces and interfaces with silicates." Thesis, University of Limpopo (Turfloop Campus), 2005. http://hdl.handle.net/10386/940.

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Thesis (Ph.D (Physics)) --University of Limpopo, 2005
We have derived a potential model for °uorapatite Ca10(PO4)6F2, ¯tted to structure, elastic constants and vibrational frequencies of the phosphate groups, which is compatible with existing calcite and °uorite potential mod- els. We then modelled the structure and stabilities of the dry and hydrated f0 0 0 1g, f1 0 1 0g, f1 0 1 1g, f1 1 2 0g, f1 0 1 3g and f1 1 2 1g surfaces, which calculations con¯rmed the experimental dominance of the f0 0 0 1g surface, which is prominently expressed in the calculated thermodynamic morphologies. The dehydrated morphology further shows the experimental f1 1 2 1g twinning plane, while the f1 0 1 0g cleavage plane is expressed in the hydrated morphology. Molecular adsorption of water has a stabilising e®ect on all six surfaces, where the surfaces generally show Langmuir be- haviour and the calculated hydration energies indicate physisorption (73 - 88 kJ mol¡1). The chains of °uoride ions surrounded by hexagonal calcium channels can become distorted in two major ways during relaxation: either by a shortening/lengthening of the FF distances, when the channel is perpendicular to the surface, or by distortion of the CaF bonds when the channel is parallel to the surface. Both distortions occur when the channel runs at an angle to the surface. Other relaxations include compression of the calcium sub-lattice and rotation of surface phosphate groups. We have modelled adsorption of a range of organic molecules onto dif- ferent °uorapatite surfaces, due to the importance of organic/ inorganic in- teractions in biological situations. We have selected organic molecules that represent a model for the carboxylic acids, alkyl hydroxamates and those 3 that contain both the aldehyde and hydroxyl functional groups. Adhesion of these organic molecules on the surfaces has shown strong interaction between the surface's Ca ions and the molecule's oxygens, more especially the car- bonyl oxygens than any other interactions. It was found that the number of interactions between the ions of adsorbate molecule and the mineral surfaces thus contribute signi¯cantly to the exothemicity of adsorption. Further more, simulations of apatite thin ¯lms at a range of ®-quartz surfaces have shown how the strength of adhesion between thin ¯lms of ap- atite material and ceramic silica surfaces is crucially dependent upon both the orientation of the ¯lm relative to the substrate and the nature of the silica surfaces, a ¯nding that is important in a wide number of applications, from basic geological research on intergrowth of phosphate and silicate rock minerals to the search for more e®ective surgical implant materials. It was shown that although the unrelaxed quartz surface is more reactive toward the apatite ¯lm, the more regular thin ¯lm structures grown at the pre-relaxed quartz surfaces lead to more stable interfaces. Film growth at the unrelaxed quartz surface is energetically increasingly unfavorable, whereas growth at the pre-relaxed surface is calculated to continue beyond the ¯rst layer, where the adhesion energy is convergent with the layer growth of the thin ¯lm. Ad- hesion of apatite thin ¯lm on hydroxylated surfaces of ®-quartz has shown to be energetically less favourable than at dry surfaces. This was because the thin ¯lm interact mainly with the hydroxyl ions on the surface of quartz. However, the adhesion energy is still convergent with layer growth of the thin ¯lm on the hydroxylated surfaces.
National Research Foundation of South Africa (NRF), Council for Scientific and Industrial research (CSIR), and the University of the North

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