Dissertations / Theses: 'Surface ordering'

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Swanson, Brian D. "Surface freezing and surface induced ordering in liquid crystal films /." Thesis, Connect to this title online; UW restricted, 1992. http://hdl.handle.net/1773/9678.

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Thesis (Ph. D.)--University of Washington, 1992.
Vita. Accompanying video is in VHS Format and contains illustrations of observations described in chapter 2. Includes bibliographical references (leaves [222]-232).

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Chang, Grace C. Koch Christof. "Neural representation of surface ordering in visual areas V1, V2 and MT /." Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-05302003-111238.

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Hoogers, Gregor. "Ordering, diffusion and laser-induced disordering on Rh{111} and Rh{332} surfaces." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337980.

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Pekelsky, James Regan Carleton University Dissertation Engineering Electrical. "The automated ordering of moire fringe contours using local photometric modelling of surface shading." Ottawa, 1988.

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Wu, Jung-Sheng 1970. "Surface morphology and ordering in side-chain liquid crystal diblock and homopolymer ultrathin films." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8502.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002.
Includes bibliographical references.
Microphase-separated morphologies of side-chain liquid crystal (LC) diblock copolymers have been examined as substrate-supported thin films. The film thicknesses ranged from 0.5 to 10 times the block copolymer period (L). These novel materials are of interest because they exhibit self-oriented electro-optical properties in the bulk state, and may exhibit interesting field dependent nanometer-scale ordering as thin films. A primary challenge in taking advantage of these properties involves the fundamental understanding and control of the nano-domain morphology, which is strongly affected by the substrate, block copolymer properties, and LC alignment within the domains. In these studies, an amorphous side-chain LC diblock polymer system has been synthesized containing a side-chain mesogen with a chiral alkyl end. Experiments were conducted using Atomic Force Microscopy, Transmission Electron Microscopy, and X-ray Specular Reflectometry, to determine the complex surface morphology. Contact angle measurements and angle-resolved X-ray Photoelectron Spectrometry were also conducted to determine LC orientation at different interfaces. From this information, final models of complex morphologies were derived for different block copolymer compositions, including lamellar, cylindrical, and new smectic-bilayered morphologies. To better understand the ordering of the LC mesogen at different interfaces, LC homopolymer films were studied. LC anchoring was planar at the substrate, but homeotropic at the air interface due to exposure of the non-polar mesogen tail. Block copolymer thin films were then examined for compositions ranging from 40% to 85% weight fraction of the LC block.
(cont.) Due to the wetting properties of the LC diblock copolymer, novel LC terraces were observed on the top surfaces corresponding to single smectic layer spacing. For diblock thin films, both blocks coexist at the air surfaces to form a mixed surface. Hybrid morphologies, consisting of both symmetrical and anti-symmetrical wettings, were noted for the lamellar morphology with film thicknesses between 0.5 and 1.5Lo. The surface properties are determined by LC orientation, which depends on the film thickness. Homeotropic anchoring of the smectic LC mesogens at the air interface was observed in both the homopolymer and the block copolymers, resulting in smectic terraces on the top surfaces of the films. In thicker films, when the influence of the substrate was decreased, the lamellar orientation was found to undergo a transition from parallel stacking near the substrate to perpendicular arrangement at the air surface. Effects of annealing and solvent exposure on the resulting thin-film behavior were also addressed.
by Jung-Sheng Wu.
Ph.D.

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Drautz, Ralf. "Ab-initio statistical mechanics for ordering and segregation at the (110) surface of Ni90%-Al." [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10720644.

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Hellsing, Maja S. "Adsorption and Ordering of Surface Active Molecules and Particles at Solid Interfaces and in the Bulk." Doctoral thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-171739.

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Factors that influence the process of adsorption and order of dilute and concentrated systems of molecules and particles are explored in this thesis. The results are based largely on neutron scattering techniques. Study of the adsorption from dilute solutions of a common surfactant, AOT (sodium bis (2-ethylhexyl) sulfosuccinate), at a solid/liquid interface showed that AOT molecules adsorbed to the interface in a bilayer structure, with the hydrocarbon tails at maximum packing density even at very low concentrations. At higher AOT concentrations, a stack of fluctuating layers each separated by large amounts of water next to the dense bilayer was seen. The driving force for adsorption is dominated by self-assembly of AOT. It was found that an oriented lamellar phase wets the interface below the bulk concentration for formation of this phase. Proteins can be viewed as polymeric surfactants. The adsorption of proteins from seeds of the Moringa oleifera tree to a silicon oxide surface was studied to elucidate the mechanism of the protein as a flocculent in water treatment processes. The protein was found to adsorb at the interface as dense layers with a thickness suggestive of co-adsorption rather than single isolated molecules. The strong adsorption and tendency to associate in solution suggest mechanisms for flocculating particulate impurities in water. As with surfactants, dispersions of colloidal particles can assemble in regular structures by self-assembly. Polystyrene latex particles were studied and could form large three-dimensional crystals of about 1×1 cm2 in a 2 mm path cell. The diffraction pattern indicated a close packed structure with the 110 axis perpendicular to the container wall. The crystal was well-aligned and oriented by the direction of flow. At the solid interface large two-dimensional domains of about 20 cm2 of highly oriented particles were formed. The particle-particle separation at the surface and in the bulk was determined by the charge repulsion of the particles.

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Anaredy, Radhika Sudhakar. "The study of ionic liquid behavior at solid-liquid interfaces." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6540.

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Ionic liquids are organic salts with room temperature melting points. Their unique physicochemical properties make them popular choices in the fields of tribology, energy storage and production, and extractions. Previous studies show that IL’s interfacial volume, extending some nanometers from an adjacent surface, is characterized by the self-assembly of IL molecules into ordered structures. This ordering imparts unique properties which often govern the properties of ILs and affect their application in the aforementioned areas. This thesis describes research conducted to understand the behaviors and interactions of ILs at interfaces, along with investigations of bulk IL structures and transitions in the presence of water. The findings reported will help the scientific community by giving insight into the physical and chemical processes surrounding IL behavior, allowing ILs’ physicochemical properties to be more accurately tailored, via judicious synthesis, to a desired application. Major findings of this work show that the ordered interfacial region may extend up to two orders of magnitude further from the interface than previously thought. Specifically, this thesis shows several examples of reversible IL self-assembly into long-range ordered films that extend up to ~ 2 μm from a surface. This is approximately twelve times the thickness of interfacial region previously reported. Temperature controlled studies on the bulk structure of an IL at its phase transition temperatures aid in understanding the structural arrangement of molecules in the bulk fluid as a function of temperature. Spectroscopic analyses of these bulk studies and the above interfacial systems showed no similarities, indicating that the self-assembled interfacial structures are, in fact, unique. Being hygroscopic in nature, water is the most common impurity found in ILs. Water can affect IL intermolecular forces and the resulting structures in bulk fluids as well as at the interface. One of the chapter of this thesis describes these interactions, and the variably hydrated IL structures for two classes of ILs via spectroscopic and electrochemical techniques. The outcomes of this thesis will aid the community in understanding interfacial and bulk structures of ILs, as well as influences of temperature and water on these structures. The description of extended IL structures provides valuable insights into new design principles for truly task-specific ILs.

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Pizzirusso, Antonio <1980&gt. "Computer simulation of ordering and dynamics in liquid crystals in the bulk and close to the surface." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1693/.

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The aim of this PhD thesis is to investigate the orientational and dynamical properties of liquid crystalline systems, at molecular level and using atomistic computer simulations, to reach a better understanding of material behavior from a microscopic point view. In perspective this should allow to clarify the relation between the micro and macroscopic properties with the objective of predicting or confirming experimental results on these systems. In this context, we developed four different lines of work in the thesis. The first one concerns the orientational order and alignment mechanism of rigid solutes of small dimensions dissolved in a nematic phase formed by the 4-pentyl,4 cyanobiphenyl (5CB) nematic liquid crystal. The orientational distribution of solutes have been obtained with Molecular Dynamics Simulation (MD) and have been compared with experimental data reported in literature. we have also verified the agreement between order parameters and dipolar coupling values measured in NMR experiments. The MD determined effective orientational potentials have been compared with the predictions of MaierSaupe and Surface tensor models. The second line concerns the development of a correct parametrization able to reproduce the phase transition properties of a prototype of the oligothiophene semiconductor family: sexithiophene (T6). T6 forms two crystalline polymorphs largely studied, and possesses liquid crystalline phases still not well characterized, From simulations we detected a phase transition from crystal to liquid crystal at about 580 K, in agreement with available experiments, and in particular we found two LC phases, smectic and nematic. The crystalsmectic transition is associated to a relevant density variation and to strong conformational changes of T6, namely the molecules in the liquid crystal phase easily assume a bent shape, deviating from the planar structure typical of the crystal. The third line explores a new approach for calculating the viscosity in a nematic through a virtual exper- iment resembling the classical falling sphere experiment. The falling sphere is replaced by an hydrogenated silicon nanoparticle of spherical shape suspended in 5CB, and gravity effects are replaced by a constant force applied to the nanoparticle in a selected direction. Once the nanoparticle reaches a constant velocity, the viscosity of the medium can be evaluated using Stokes' law. With this method we successfully reproduced experimental viscosities and viscosity anisotropy for the solvent 5CB. The last line deals with the study of order induction on nematic molecules by an hydrogenated silicon surface. Gaining predicting power for the anchoring behavior of liquid crystals at surfaces will be a very desirable capability, as many properties related to devices depend on molecular organization close to surfaces. Here we studied, by means of atomistic MD simulations, the flat interface between an hydrogenated (001) silicon surface in contact with a sample of 5CB molecules. We found a planar anchoring of the first layers of 5CB where surface interactions are dominating with respect to the mesogen intermolecular interactions. We also analyzed the interface 5CBvacuum, finding a homeotropic orientation of the nematic at this interface.

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Maeda, Nobuo, and nobuo@engineering ucsb edu. "Phase Transitions of Long-Chain N-Alkanes at Interfaces." The Australian National University. Research School of Physical Sciences and Engineering, 2001. http://thesis.anu.edu.au./public/adt-ANU20011203.151921.

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An experimental study of phase transitions of long-chain n-alkanes induced by the effect of interfaces is described. ¶ The phase behaviour of long-chain n-alkanes (carbon number 14, 16, 17, 18) adsorbed at isolated mica surfaces and confined between two mica surfaces has been studied in the vicinity of and down to several degrees below the bulk melting points, Tm. Using the Surface Force Apparatus we have measured the thickness of alkane films adsorbed from vapour (0.97 [equal to or greater-than] p/p[subscript o] [equal to or greater-than] 0.997), studied capillary condensation transition, subsequent growth of capillary condensates between two surfaces, and phase transitions in both the adsorbed films and the condensates. By measuring the growth rate of the capillary condensates we have identified a transition in the lateral mobility of molecules in the adsorbed films on isolated mica surfaces. This transition to greater mobility occurs slightly above Tm for n-hexadecane, n-heptadecane and n-octadecane but several degrees below Tm for n-tetradecane, and is accompanied by a change in wetting behaviour and a measurable decrease in adsorbed film thickness for n-heptadecane and n-octadecane. Capillary condensates that form below Tm remain liquid, but may freeze if the degree of confinement is reduced by separation of the mica surfaces. An increase in the area of the liquid-vapour interface relative to that of the liquid-mica interface facilitates freezing in the case of the long-chain alkanes, which show surface freezing at the liquid-vapour interface. ¶ Although thermodynamic properties of the surface freezing transition have been rather well documented, the kinetics involved in formation of such ordered monolayers has so far received very little attention. We studied the surface tension of n-octadecane as a function of temperature in the vicinity of Tm, using the static Wilhelmy plate and the dynamic maximum bubble pressure methods. The two methods give different results on cooling paths, where nucleation of the surface ordered phase is involved, but agree on heating paths, where both methods measure properties of the equilibrium surface phase. On cooling paths, the surface of bubbles may supercool below the equilibrium surface freezing temperature. The onset of surface freezing is marked by a sharp drop in the surface tension. The transition is accompanied by an increased stability of the films resulting in longer bubble lifetimes at the liquid surface, which suggests that the mechanical properties of the surfaces change from liquid-like to solid-like. Our results suggest occurrence of supercooling of the monolayer itself.

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Yokoyama, Soichi. "Exploration of Photoreaction and Cooperative Self-Assembly of Photofunctional Molecules at Two-Dimensional Surface toward Nanodevices." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202723.

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Tavarone, Raffaele [Verfasser], Holger [Akademischer Betreuer] Stark, Holger [Gutachter] Stark, and Thomas [Gutachter] Gruhn. "Liquid-crystal ordering of photo-switchable molecules on a surface / Raffaele Tavarone ; Gutachter: Holger Stark, Thomas Gruhn ; Betreuer: Holger Stark." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156011469/34.

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Feng, Xunda Verfasser], Christian [Akademischer Betreuer] Bahr, Christoph F. [Akademischer Betreuer] Schmidt, and Stephan [Akademischer Betreuer] [Herminghaus. "Structures and Self-Organization at Liquid Crystal Interfaces: Surface Ordering and Anchoring / Xunda Feng. Gutachter: Christoph F. Schmidt ; Stephan Herminghaus. Betreuer: Christian Bahr." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044306505/34.

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Akoumeh, Rayane. "Films hiérarchiquement micro structurés en nid d’abeilles : élaboration, étude de la topographie et de la chimie de surface par TOF-SIMS." Thesis, Pau, 2016. http://www.theses.fr/2016PAUU3052/document.

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Dans le domaine des polymères, l'auto-organisation de la matière a été largement étudiée dans les dernières années et beaucoup de progrès dans le domaine des films ordonnés, générés par l'auto-assemblage de copolymères à blocs, ont été réalisés. Ce progrès est motivé par le fait que les films auto-assemblés possèdent des applications en biologie, photonique, adhésion. Le sujet initial de thèse est la fabrication des films structurés en nid d’abeilles formés par un bloc de copolymère contenant une partie hydrophobe ( à peu près 90%) et une partie hydrophile (10%) qui peuvent s’auto-organiser en nid d’abeilles. Les films de polymères préparés seront ultérieurement à la base d’une étude de complexation avec des métaux. Ceci sert à décontaminer les eaux usées des métaux ou pesticides. Durant ces années de thèse, une méthodologie d’analyse de surface est détaillée pour comprendre la topographie de ces films ainsi que la chimie de surface de ces derniers. Pour cette raison, divers techniques d’analyses sont utilisées pour décrire vigoureusement la surface de ces films afin d’optimiser ces films pour complexer les contaminants à origine industrielle.Une des techniques d’analyse de surface, i.e. TOF-SIMS (Time Of Flight-Secondary Ion Mass Spectroscopy), a prouvé être un outil efficace pour caractériser chimiquement la composition élémentaire et moléculaire de l’extrême surface et en profondeur. Cette technique était la technique de base de ces études. Elle la permis de décrire les empreintes spectrales ainsi que la distribution en surface et en profondeur de chaque polymère dans les films élaborés en nid d’abeilles
Since its introduction in 1994, the preparation of ordered porous polymer films by the breath figure “BF” method has received a considerable interest. Self-organized porous polymer films, with pores ordered into a hexagonal pattern, can be elaborated by a fast solvent evaporation method under a humid atmosphere, also called “Breath Figure” approach. The honeycomb films have found a panel of perspective applications ranging from materials with optical properties, biomaterial sensors, and scaffold for tissue engineering or highly hydrophobic surfaces. The main objective of this PhD thesis project is the fabrication of sensitive hierarchically self-organized bio inspired films based on organic compound trapping block copolymers. It is worth noting that one of the advantages of using block copolymer structure is that the first block confers the hydrophobic character, required for the elaboration and stability of HC structure, and the second block could provide an additional functionality such as hydrophilicity, stimuli-responsive character or trapping of targeted molecules (especially metals).During this thesis, a methodology of surface analysis is performed in order to understand the topography of these films as well as its surface chemistry. For this reason, various analytical techniques are used to describe the surface of these films vigorously in order to optimize these films to complex industrial contaminants.One of the techniques of surface analysis, i.e. TOF-SIMS (Time of Flight-Secondary Ion Mass Spectroscopy), has proved to be an effective tool for chemical characterization of the surface and in depth. This technique was the basic technique of our studies. It allowed the description of spectral finger prints as well as the distribution on the surface and in depth of each polymer in the structured films

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Schoenborn, Oliver Lars. "Phase-ordering kinetics on curved surfaces." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0011/NQ35313.pdf.

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Deak, David S. "Molecular ordering on nanostructured strontium titanate surfaces." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442394.

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Lima, Juliana Roberta Theodoro de. "Ordering homotopy string links over surfaces and a presentation for the generalized string links over surfaces." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/55/55135/tde-28042015-155522/.

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In this work, we prove that the set of link-homotopy classes of generalized string links over a closed, connected and orientable surface M of genus g ≥ 1 form a group, denoted by Bn(M) and we find a presentation for it. Moreover, we prove that its normal subgroup PBnn(M), namely, the homotopy string links over M, is bi-orderable. These results extend results proved by Juan GonzalezMeneses in [GM], [GM2] and Ekaterina Yurasovskaya in [Y], respectively. Also, we obtain an exact sequence for link-homotopy braid groups, which is an extension of [Go, Theorem 1].
Sem resumo

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Goh, Roland Ghim Siong. "Carbon nanotubes for organic electronics." Queensland University of Technology, 2008. http://eprints.qut.edu.au/20849/.

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This thesis investigated the use of carbon nanotubes as active components in solution processible organic semiconductor devices. We investigated the use of functionalized carbon nanotubes in carbon nanotubes network transistors (CNNFET) and in photoactive composites with conjugated polymers. For CNNFETs, the objective was to obtain detailed understanding of the dependence of transistor characteristics on nanotubes bundle sizes, device geometry and processing. Single walled carbon nanotubes were functionalized by grafting octadecylamine chains onto the tubes, which rendered them dispersible in organic solvents for solution processing. To investigate the dependence of electronic properties of carbon nanotubes networks on bundle size, we developed a centrifugal fractionation protocol that enabled us to obtain nanotube bundles of different diameters. The electronic properties of networks of nanotube bundles deposited from solution were investigated within a CNNFET device configuration. By comparing devices with different degree of bundling we elucidated the dependence of key device parameters (field effect mobility and on/off ratio) on bundle sizes. We further found that, in contrast to traditional inorganic transistors, the electronic properties of the CNNFETs were dominated by the channel rather than contact resistance. Specifically, the apparent mobility of our devices increased with decreasing channel length, suggesting that the charge transport properties of CNNFETs are bulk rather than contacts dominated. This meant that charge traps in the channel of the device had a significant effect on transport properties. We found that charge traps in the channel region introduced by adsorbed oxygen and silanol groups on the SiO2 surface were responsible for the dominant p-type conductance in as-fabricated devices. Based on this understanding, we demonstrated the p-type to n-type conversion of the transistor characteristics of CNNFETs by depositing nanotubes on electron-trapfree dielectric surfaces. Finally, by combining annealing and surface treatment, we fabricated CNNFETs with high n-type mobility of 6cm2/V.s. For polymer composites, the objective was to obtain detailed understanding of the interactions between carbon nanotubes and the conjugated polymer; a prerequisite for using these composites in organic electronic devices. We fabricated well dispersed nanotube/polymer composites by using functionalized carbon nanotubes and studied the effect of nanotubes addition on the photophysical properties of the technologically important conjugated polymer poly(3-hexylthiophene) (P3HT). Measurement of the photoluminescence efficiency of nanotubes/polymer composites showed that addition of 10wt% carbon nanotubes effectively quenched the polymer emission indicating close electronic interactions. This indicated that nanotubes/polymer composites have potential in organic photovoltaic or light-sensing devices. Further analysis of the steady-state photoluminescence spectra revealed that nanotube addition resulted in increased structural disorder in the polymer. The incorporation of structural disorder into the polymer with the addition of even a small amount of carbon nanotubes may be detrimental to charge transport. UV-vis adsorption studies revealed that one-dimensional templating of P3HT chains by nanotubes resulted in a red-shifted feature in the solutionstate optical adsorption spectra of P3HT. This suggested that presence of nanotube surface templates the polymer self-organisation to produce highly ordered coating of P3HT chains around the nanotube. In order to elucidate the nanoscale origin of this phenomenon, we performed detailed STM studies on individual nanotubes adsorbed with P3HT chains. Since carbon nanotubes can be considered as rolled up sheets of graphite, we also performed STM on P3HT chains assembly on graphite for comparison. For P3HT assembly on HOPG, we found that while 2D crystals were observed when P3HT was cast onto HOPG from dilute solution, a thicker and more disordered film resulted when cast from concentrated solutions and subsequent layers were more likely to align normal to an underlying monolayer of P3HT on the HOPG surface. STM studies of nanotube/polymer mixtures revealed that the P3HT chains are adsorbed on nanotubes surface in such a way that the thiophene and hexyl moieties of the polymer associated with the nanotube surface in identical manner to P3HT monolayer depositions on graphite. This resulted in the increased order as inferred from adsorption UV-Vis spectroscopy, where the polymer chains, which are otherwise prone to chain kinks and twists in solution, adopt a planar configuration when adsorbed onto the nanotube surface.

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Nania, Samantha Lynn. "Spectroscopic analysis of molecular fluids at the solid-liquid interface." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5972.

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Chemical and physical interactions play important roles in surface film formation and fluid slip at the fluid-solid interface. It has been shown that the fluid molecules at this solid interface behave differently than the molecules in the bulk. To investigate fluid film formation and the fluid’s transition between bulk and interfacial regions, a dynamic wetting technique is utilized. This technique allows the formation of variable thickness fluid films. When used in conjunction with vibrational spectroscopy and ellipsometry, direct analysis of variable thicknesses films, spanning the bulk to interfacial transition, can be obtained. Film thickness are predicted using the Landau-Levich model and the Lifshitz model, and comparisons generally agree with experimental results. According to hydrodynamic no slip boundary condition, fluid molecules near a solid surface can have no velocity with respect to the solid substrate. Recent theories state more specifically that, if a fluid comes in contact with an ultra-smooth surface (< 5-7 nm RMS roughness), the no slip boundary condition might be violated. We confirmed violation of the no slip boundary condition in two specific cases for fluid layers on SAM-modified substrates. To understand how the fluid/solid properties affect this condition, an acetophenone and bare silver surface was studied. Our results show that the structure and ordering of fluid molecules within these films are highly dependent on the film’s thickness and confinement. Temperature control wetting studies also corroborate with these results showing that as a frozen film of large thickness approaches the melting point, a molecular reorganization occurs creating a crystalline structure before the film melts into an isotropic bulk structure. Structure dependence on alkyl-chain length was then investigated using a series of trialkylamine fluids. Results show significant changes in the vibrational profile as a function of film thicknesses and rotational velocity as the alkyl-chains increase in length. These are ascribed to changes in primary carbon attached to the nitrogen as a function shearing and the rigidity of the molecule. These results reveal interactions taking place at the solid-liquid interface and have impacts on a broad spectrum of industrial, commercial, and research applications including lubrication and transportation vehicles.

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Ayissi, Serge Olivier. "Simulation of chiral ordering process in the adsorption of chiral organic molecules on metal surfaces by Monte Carlo methods." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490608.

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Experimental observations have shown that haloalkane molecules, e.g. l-cWorododecane, physisorbed on Si(111)-(7 x 7) self-assemble to form dimers stable to 100Ã‚Â° C which corral silicon adatoms. The corral size is governed by the haloalkane chain-length. Spectroscopic and theoretical evidence shows that the haloalkane dimer induces electron transfer to the corralled adatom. The enclosed silicon adatom, within a bistable dimeric corral of self-assembled chlorododecane molecules, switches its energy levels permanently (Type-II corrals) or discontinuously (Type-I corrals). Both types of corral, switching and stable, can be seen to alter the local surface charge distribution. Density Functional Theory and electron transport (STM) simulations of the switch and the stable molecular configurations can help the theoretical understanding of both phenomena in order to characterized the exact molecular conformations that produce field effects to the corralled silicon adatom and local surface charge distribution. Chiral heterogeneous catalysts are mostly fabricated from chiral molecules on a metal support. They playa crucial role in intermediate reactions in the fabrication of pharmacies, itself and important part of today's health econolPY. However, the key parameters in the fabrication of these catalysts, a requirements for their rational design, are still poorly understood despite years of experimental research. In essence, such an understanding can only come from high-level simulations. Here, we present the first predictions about the structure of such a catalyst, tartaric acid on a copper support, over the whole phase space of temperature and coverage. Interestingly, we find that molecular vibrations playa key role in the ensuing ordered structures, and that tuning the fabrication temperature should allow for a wide range of molecular separations, which can be targeted at specific molecules and reactions in chiral heterogeneous catalysis.

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Vogelgesang, Simon [Verfasser], Claus [Akademischer Betreuer] Ropers, Claus [Gutachter] Ropers, and Stefan [Gutachter] Mathias. "Ultrafast low-energy electron diffraction at surfaces : Probing transitions and phase-ordering of charge-density waves / Simon Vogelgesang ; Gutachter: Claus Ropers, Stefan Mathias ; Betreuer: Claus Ropers." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/117944924X/34.

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Melle, Michael [Verfasser], Martin [Akademischer Betreuer] Schoen, Carol K. [Akademischer Betreuer] Hall, and Sabine H. L. [Akademischer Betreuer] Klapp. "Anisotropic fluids and the manipulation of their ordering at curved surfaces / Michael Melle. Gutachter: Martin Schoen ; Sabine H. L. Klapp ; Carol K. Hall. Betreuer: Martin Schoen ; Carol K. Hall." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1066161313/34.

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Maiti, Subhankar. "Study Of Surface Ordering And Disordering." Thesis, 1996. http://etd.iisc.ernet.in/handle/2005/1594.

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Feng, Xunda. "Structures and Self-Organization at Liquid Crystal Interfaces: Surface Ordering and Anchoring." Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0015-9BFE-3.

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Chang, Grace C. "Neural Representation of Surface Ordering in Visual Areas V1, V2 and MT." Thesis, 2003. https://thesis.library.caltech.edu/2288/1/thesis_gracechang.pdf.

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Visual cortical areas V1, V2 and MT may participate in the representation of surface ordering, the arrangement of one surface in front of another. This work investigates the role of neurons of V1 and V2 in figure-ground representation in static stimuli, as well as the role of MT in surface ordering in dynamic stimuli.

Electrical recordings were made in V1 and V2 to determine whether neurons in these areas encode information about the identities of figure and ground, and also whether they respond to figure-ground cues. We recorded from 3 monkeys, one trained on a fixation task, and the other two on a match-to-sample task that ensured attention to the stimuli. The stimuli consisted of rectangles of differing contrast arranged in an unambiguous or ambiguous figure-ground configuration. The stimuli were positioned such that the cells' receptive fields were located either at the border between rectangles or in the interiors of rectangles. Cells demonstrating selectivity at borders or interiors of unambiguous figure-ground stimuli were considered selective for border ownership or figure vs. ground, respectively. Cells showing selectivity at borders or interiors of ambiguous figure-ground stimuli were considered selective for figure-ground cues.

Preliminary experiments on the fixating monkey suggested that a small fraction of cells in V1 and V2 might play a role in figure-ground interpretation. The results from the awake behaving monkeys further support the hypothesis that V1 and V2 play a role in figure-ground perception. In both areas we found cells demonstrating selectivity for border ownership, and in V2 we found cells demonstrating selectivity for figure over ground. However, in V1 and V2 there was also evidence a separate population was responding to the presence of figure-ground cues in the stimulus.

The experiments in MT were performed on two awake behaving monkeys. The stimuli were transparent rotating cylinders comprised of random dots moving along a sinusoidal gradient. The stimuli were bistable?perceived to rotate in one direction or its opposite. The monkeys indicated in which direction they perceived the cylinder?s front surface rotating. Cells were found whose firing correlated with the monkeys? bistable percept, even though the stimuli were identical.

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Chen, Po-Hung, and 陳柏宏. "Enhanced Magnetic Ordering and Spinterface of F4-TCNQ on Ni/Cu(100) Surface." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/16335760381212836833.

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碩士
國立清華大學
先進光源科技學位學程
102
We investigated the magnetic properties and spin interface of tetrafluorotetracyanoquinodimethane (F4-TCNQ)-tailored nickel (Cu(100)/Ni) surface which display enhanced magnetic ordering at lower critical thickness of Ni film. Surface magnetic anisotropy performed by the magneto-optical Kerr effect (MOKE) displays magnetic hardening upon F4-TCNQ adsorption. The magnetic domains inspected by photoelectron-emission microscope (PEEM) measurements also exhibits improved magnetic ordering with larger domain sizes and less domain boundary. To elucidate the origin of enhanced magnetic ordering after molecular tailoring, surface-sensitive and element specific X-ray Magnetic Circular Dichroism (XMCD) were employed. The XMCD reveals the orbital and spin moment of in-plane Ni is significantly increased, while that keep almost unaltered at out-of-plane. Through the strong superexchange coupling at in-plane, the nonmagnetic F4-TCNQ is spin polarized. Our results suggest the enhanced magnetic ordering of such organic-ferromagnetic interface is an effective spin filtering for constructing high efficient organic spintronics.

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Drautz, Ralf [Verfasser]. "Ab-initio statistical mechanics for ordering and segregation at the (110) surface of Ni90%-Al / vorgelegt von Ralf Drautz." 2003. http://d-nb.info/968815308/34.

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Buchner, Florian [Verfasser]. "STM investigation of molecular architectures of porphyrinoids on a Ag(111) surface : supramolecular ordering, electronic properties and reactivity = STM-Untersuchung von Porphyrinoiden auf einer Ag(111)-Oberfläche / vorgelegt von Florian Buchner." 2010. http://d-nb.info/1000613143/34.

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Vogelgesang, Simon. "Ultrafast low-energy electron diffraction at surfaces." Doctoral thesis, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E5A1-F.

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(9754796), Tyler R. Hayes. "DEVELOPMENT OF THERMALLY CONTROLLED LANGMUIR–SCHAEFER CONVERSION TECHNIQUES FOR SUB-10-NM HIERARCHICAL PATTERNING ACROSS MACROSCOPIC SURFACE AREAS." Thesis, 2020.

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As hybrid 2D materials are incorporated into next-generation device designs, it becomes more and more pertinent that methods are being developed which can facilitate large-area structural control of noncovalent monolayers assembled at 2D material interfaces. Noncovalent functionalization is often leveraged to modulate the physical properties of the underlying 2D material without disrupting the extended electronic delocalization networks intrinsic to its basal plane. The bottom-up nanofabrication technique of self-assembly permits sub-10-nm chemical patterning with low operational costs and relatively simple experimental designs.

The Claridge Group is interested in leveraging the unique chemical orthogonality intrinsic to the cellular membrane as a means of creating sub-10-nm hydrophilic-hydrophobic striped patterns across 2D material interfaces for applications ranging from interfacial wetting to large-area molecular templates to guide heterogeneous nanoparticle assembly. Using Langmuir–Schaefer conversion, standing phases of polymerizable amphiphiles at the air-water interfaces of a Langmuir trough are converted (through rotation) to lying-down phases on 2D material substrates. Using room temperature substrates, transfer of amphiphiles to a lowered substrate results in small domains and incomplete surface coverage.

Recognizing that heating the substrate during the LS conversion process may lower the energy barriers to molecular reorientation, and promote better molecular domain assembly, we developed a thermally controlled heated transfer stage that can maintain the surface temperature of the substrate throughout the deposition process. We found that heating during transfer results in the assembly of domains with edge lengths routinely an order of magnitude larger than transfer using room temperature substrates that are more stable towards rigorous repeat washing cycles with both polar and nonpolar solvents.

To promote the effectiveness of the LS conversion technique beyond academic environments for the noncovalent functionalization 2D material substrates for next-generation device designs, we designed and built a thermally controlled rotary stage to address the longstanding scaling demerit of LS conversion. First, we report the development of a flexible HOPG substrate film that can wrap around the perimeter of the heated disk and can be continuously cycled through the Langmuir film. We found that thermally controlled rotary (TCR) LS conversion can achieve nearly complete surface coverage at the slowest translation speed tested (0.14 mm/s). TCR–LS facilitates the assembly of domains nearly 10,000 μm² which were subsequently used as molecular templates to guide the assembly of ultranarrow AuNWs from solution in a non-heated rotary transfer step. Together, these findings provide the foundation for the use of roll-to-roll protocols to leverage LS conversion for noncovalent functionalization of 2D materials. A true roll-to-roll thermally controlled LS conversion system may prove to be advantageous and a cost-efficient process in applications that require large areas of functional surface, or benefit from long-range ordering within the functional film.

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Timmer, Frederic Yaw. "Diffraction studies on ordering of quasi-one-dimensional structures and nanowires on silicon surfaces induced by metals." Doctoral thesis, 2017. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2017112016336.

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In this thesis the morphology and the atomic structure of quasi-one-dimensional structures grown on Si were determined by means of diffraction experiments in combination with kinematic diffraction theory calculations. In the first and the second study a formerly unknown superstructure of Dy/Tb on Si(111) was characterized by means of STM, DFT, SPA-LEED experiments and kinematic diffraction calculations. Here, a structure model could be proposed which contains half as many subsurface Si vacancies as compared to the well-known superstructure of Dy/Tb on Si(111) it was derived from. Due to the decreased number of subsurface Si vacancies the reconstruction is subject to an uni-axial strain which is mitigated by the formation of domains separated by anti-phase domain boundaries. It could be shown that two different types of domains alternate across the surface forming quasi-one-dimensional domains. Additionally, the distribution of the domains could be derived by comparison with kinematic diffraction calculations. In the third study a deeper insight into the complex system of bundled rare-earth silicide nanowires on Si(001) was given. Here, the distributions of the NW width, the bundle width and the bundle distance were deduced from the diffraction patterns collected by SPA-LEED and the subsequent comparison to kinematic diffraction theory calculations. Additionally, it was shown that the (2 x 1) reconstruction sometimes observed on top of the NWs by STM cannot exist over larger parts of the sample and instead a (1 x 1) reconstruction needs to be assumed to explain the experimentally observed diffraction data. In the fourth study the atomic structure of the gold induced atomic wires of the Si(111)-(5 x 2)-Au system was analyzed. The Patterson function of the in-plane SXRD data was compared to the Patterson functions derived from the atomic structure models proposed in literature (AN, EBH, KK) ruling out the AN-model. By comparison of the experimental out-of-plane SXRD data to the corresponding (calculated) SXRD data for the EBH- and the KK-model the KK-model could be identified as the most probable model. Additionally, a refined atomic structure model was derived for the KK-model. In conclusion, the results presented in this thesis clearly display the power of diffraction experiments especially in conjunction with the comparison to kinematic diffraction theory calculations and prove that they are applicable even to low dimensional (e.g., quasi-one-dimensional) structures. Furthermore, it was shown that diffraction experiments can deliver complementary information (e.g., information on deeper atomic layers) as compared to local probing methods (e.g. STM or Atomic Force Microscopy) and especially the combination of local probing methods, DFT calculations and diffraction experiments allows for the explanation of even very complicated material systems.

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Clearfield, Howard M. "Low-energy electron diffraction studies of defect structures and ordering kinetics at p(lxl) surfaces GaAs(110) and GaAs(110) p(lxl)-Sb /." 1985. http://catalog.hathitrust.org/api/volumes/oclc/12098997.html.

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Thesis (Ph. D.)--University of Wisconsin--Madison, 1985.
Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 442-451).

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