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1
Lee, Hyunjin. "Radiative properties of silicon wafers with microroughness and thin-film coatings". Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07092006-181152/.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2006.Zhang, Zhuomin, Committee Chair ; Joshi, Yogendra, Committee Member ; Lee, Kok-Meng, Committee Member ; Gallivan, Martha, Committee Member ; Zhao, Yiping, Committee Member.
2
Guegan, Johan. "Experimental investigation into the influence of roughness on friction and film thickness in EHD contacts". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/53388.
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The roughness of machined surfaces such as those in bearings and gears is characterized by asperities which cover a wide spectrum of wavelengths and heights. When the height of the asperities becomes comparable to the lubricant film thickness, the roughness is known to influence friction and wear behaviour. This thesis reports an experimental investigation into the effect of roughness on the film thickness and friction in EHD contact. This work focuses on the particular roughness case of ridges oriented parallel to the rolling-sliding direction, such as the ones produced on raceways during the manufacturing process of rolling element bearings. To carry-out this research a ball-on disk test rig was used to model the contact between the ball and the ring of a ball bearing. The disks were made of glass to enable the lubricant film thickness to be measured through an optical technique based on optical interferometry. The ball specimens were made of AISI 52100 steel and they were roughened with a cutting tool, resulting in longitudinally oriented roughness ridges showing a dominant wavelength and amplitude. The friction was measured through a torque meter attached to the ball shaft. A duo-chromatic system using two LEDs was developed in order to be able to measure the film thickness over a wider range of film thickness. A novel procedure was also introduced to enable the film thickness in rough EHD contacts to be measured accurately. The film thickness and the friction produced by specimens with various amplitude and wavelength were measured under pure rolling and rolling-sliding conditions. The roughness was found to have a big influence on both film build-up and friction. In particular, under the same operating condition, a rough specimen will generate a thinner minimum film and a higher friction compared to a smooth specimen. At the top of the asperities, a micro-EHD film was found to form. As suggested by friction and pressure measurements, the conditions in this micro film are severe enough to reach the limiting shear stress of the lubricant.
3
Cardwell, Nicholas Don. "Effects of Realistic First-Stage Turbine Endwall Features". Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/36121.
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The modern gas turbine engine requires innovative cooling techniques to protect its internal components from the harsh operating environment typically seen downstream of the combustor. Much research has been performed on the design of these cooling techniques thus allowing for combustion temperatures higher than the melting point of the parts within the turbine. As turbine inlet temperatures and efficiencies continue to increase, it becomes vitally important to correctly and realistically model all of the turbine's external cooling features so as to provide the most accurate representation of the associated heat transfer to the metal surfaces. This study examines the effect of several realistic endwall features for a turbine vane endwall. The first study addresses the effects of a mid-passage gap, endwall misalignment, and roughness on endwall film-cooling. The second study focuses on the effect of varying the combustor-to-turbine gap width. Both studies were performed in a large-scale low speed wind tunnel with the same vane geometry. Geometric and flow parameters were varied and the variation in endwall cooling effectiveness was evaluated.
Results from these studies show that realistic features, such as surface roughness, can reduce the effectiveness of endwall cooling designs while other realistic features, such as varying the combustor-to-turbine gap width, can significantly improve endwall cooling effectiveness. It was found that, for a given coolant mass flowrate, a narrow combustor-turbine gap width greatly increased the coverage area of the leaked coolant, even increasing adiabatic effectiveness upstream of the vane stagnation point. The turbine designer can also more efficiently utilize leaked coolant from the combustor-to-turbine gap by controlling endwall misalignment, thereby reducing the overall amount of film-cooling needed for the first stage.Master of Science
4
Shioya, Nobutaka. "Development of Analytical Technique of Molecular Orientation in a Thin Film and Its Application to Low-Crystallinity Organic Thin Films Having a Surface Roughness". Kyoto University, 2018. http://hdl.handle.net/2433/232268.
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Aghasi, Paul P. "Dependence of Film Cooling Effectiveness on 3D Printed Cooling Holes". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1458893416.
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Webb, Joshua J. "The Effect of Particle Size and Film Cooling on Nozzle Guide Vane Deposition". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313528110.
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Pavlík, František. "Studium vlivu parametru elipticity na rozložení tloušťky mazacího filmu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229941.
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Diploma thesis deals with elastohydrodynamic lubrication of point contacts, which surfaces are influenced by topography and velocity vector of one rubbing surface is misaligned. Author summarizes knowledge of previously published research articles, which fundamentally enrich current state of knowledge. Diploma thesis contains experimental measurement results of the film thickness and the way of lubrication film formation in elliptical contact for different ellipticity parameters, kinds of rubbing surfaces and angles of the velocity vector. New findings have helped to better understand the behaviour of highly loaded lubricated contacts taking place in machine components and completed the current state of knowledge with results that can be used in next thorough study of this issue.
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Fratini, Christopher M. "Study of the Morphology and Optical Properties of Propylene/Ethylene Copolymer Films". Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/27211.
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The development of a new catalyst system by The Dow Chemical Company has resulted in the production of isotactic polypropylene and propylene/ethylene copolymers with a unique defect and comonomer distribution. This work investigated the morphology and optical properties of cast and compression molded films made from the homopolymer and copolymers with up to 20 mol% ethylene comonomer. The defect distribution of the Dow Chemical copolymers resulted in materials with lower crystallinity than Ziegler-Natta or metallocene-made materials of similar ethylene content. These materials exhibited a gamma-phase crystal content ranging from 0-95%, depending on ethylene content, processing condition, and catalyst type.
The gamma-phase crystal content of quiescently crystallized copolymer films was found to significantly influence their bulk optical properties, presumably through a change in the spherulite birefringence. The bulk haze, clarity, and transparency of a homopolymer film were degraded through annealing treatments, which decreased the fraction of gamma-phase crystallinity and increased the thickness of existing lamellae, resulting in an increased intensity of scattered light and a corresponding degradation in the optical properties of the film. The haze, clarity, transparency, and gloss of the copolymer films were found to improve at higher comonomer content and higher cooling rates. The variation in the length scale and degree of disorder in the bulk morphology of films processed under different conditions was shown to correlate with the optical quality of the films, with smaller scale morphologies scattering less light and resulting in films with better optical properties.
It was also shown that no single metric can completely describe the optical quality of a polymer film; the relative importance of haze, transparency, and gloss, which depends on the intended application of the film, was discussed. The influence of surface scattering from the films was controlled through the compression molding of films using substrates of different surface roughness. The contribution of light scattered from the surface of the films was isolated and found to play a significant role in the degradation of optical quality.Ph. D.
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Sugar, Joshua D. "Mechanisms of microstructure development at metallic-interlayer/ceramic interfaces during liquid-film-assisted bonding". Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2003. http://www.osti.gov/servlets/purl/825347-j6A0Su/native/.
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Thesis (M.S.); Submitted to the University of California, Berkeley, CA (US); 1 Dec 2003.Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--54185" Sugar, Joshua D. USDOE Director. Office of Science. Basic Energy Sciences (US) 12/01/2003. Report is also available in paper and microfiche from NTIS.
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Simon, Darren, i s3027589@student rmit edu au. "Chemistry and Morphology of Polymer Thin Films for Electro-Optical Application". RMIT University. Applied Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070123.122707.
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Thin polymer films and their properties have been investigated. The characteristics of crystalline polymers according to film thickness have been improved using polycaprolactone (PCL). The melting enthalpy of PCL has increased when the film thickness decreased and the peak melting temperature showed no significant changes with film thickness. Film thickness variation influenced surface roughness and crystal size. Optical microscope images showed the rougher surface of thicker films. The spinning time has shown no influence on film thickness and no significant changes to surface roughness. Thin films of block copolymers were used in the surface modification study; films studied included poly(styrene-b-butadiene-b-styrene) (SBS) and poly(styrene-b-isoprene-b-styrene) (SIS) and their surface modifications have been controlled using different methods of treatment. Films of SIS heated at different temperatures have shown different surface texture and roughness. Films treated at low temperature (45 °C) had smooth surfaces when compared with films heated at high temperature (120 °C and 160 °C). Phase separation of SIS heated at (120 °C and 160 °C) caused bulges of different sizes to cover the surface. The height and width of the bulges showed variation with film thickness and heating. Substrate interaction with SBS and SIS block copolymer films showed different surface texture when using the same type of substrate and different texture were obtained when SBS solutions were spun onto different substrates. It has been demonstrated that using different solvents in copolymer preparation caused different texture. Thermal and surface property variations with film thickness have been improved using amorphous polymers. Surface roughness of poly(methyl methacrylate) PMMA and disperse red 1-poly(methyl methacrylate) DR1-PMMA, PMMA has improved using thickness variation. Glass transition temperature measurement has increased when film thickness was increased. The glass transition temperature (Tg) and surface roughness of UV15 UV - curable coating polymer has been modified using UV curing and heating methods. Tg variation was observed when curing time and curing intensity were changed causing the optical properties of the polymer to be more variable. A plasma etcher caused wrinkles to occur on the surface of unheated UV15. Tg of UV15 increased when curing time increased. The Fourier Transform Infrared Spectroscopy (FTIR) spectra of cured UV15 film have shown peak variations of the ester and carbon double bond regions over the range of 1850-1700 cm-1. Urethane-Urea (UU) Polymer thin films were used to investigate optical properties and develop an optical waveguide. Absorption and transmission properties of light using non-linear optical (NLO) polymer was investigated and used in optical waveguide fabrication. Refractive indices were measured to examine UU films at two different wavelengths. A UU film of 1 µm thickness caused a maximum absorption at max = 471 nm also obtained at 810 nm wavelength. Many methods of fabrication were used; photolithography, plasma etching in a barrel reactor and thin film deposition using sputtering and evaporation. Etched depths from 1 μm to 100 μm were obtained. An optical waveguide has been prepared using plasma etching of a cured UV15 as a cladding layer on a silicon substrate.
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Bock, Bradley D. "Surface influences on falling film boiling and pool boiling of saturated refrigerants : influences of nanostructures, roughness and material on heat transfer, dryout and critical heat flux of tubes". Thesis, University of Pretoria, 2020. http://hdl.handle.net/2263/78711.
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Falling film evaporators that operate in the nucleate boiling regime in the refrigeration industry offer a number of advantages over their flooded counterparts such as lower refrigerant charge and at times improved heat transfer. Existing literature has not characterised the influence of surface characteristics on the falling film boiling process, and they are poorly understood for the pool boiling process. The purpose of this study was therefore to experimentally measure the influence of roughness, material and nanostructures on the heat transfer of falling film boiling and pool boiling of saturated refrigerants on the outside of horizontal tubes. The critical heat flux point was measured if it occurred, and the falling film heat transfer enhancement ratio, critical dryout threshold and general dryout characteristics were investigated in the study.
The tubes tested consisted of plain copper, stainless steel and mild steel tubes that were polished and roughened with various grades of sandpaper. Furthermore, three types of nanostructured surfaces were applied to polished copper tubes, namely a layer-by-layer (LbL) coating of silica nanoparticles, a copper oxide (CuO) nanostructure coating and a commercial nanocoating process termed nanoFLUX.
The nanoFLUX tube had the highest heat transfer coefficients of tubes tested under both pool boiling and falling film conditions, with between 40 and 200% higher heat transfer coefficients than those of a polished copper tube. The nanoFLUX surface outperformed the other surfaces due to a combination of rougher microstructure and a unique heat transfer mechanism, possibly linked to capillary wicking of liquid inside the nanochannels of the porous coating.
The falling film heat transfer enhancement ratio was found to increases as surface roughness was increased on plain tubes, suggested to be as a result of enhanced microlayer evaporation from the trapped sliding bubbles in the thin flowing film.
The nanoFLUX and CuO surfaces experienced lower critical heat flux as a result of departure from nucleate boiling under pool boiling and falling film boiling conditions compared with plain surfaces.. However, the nanoFLUX and CuO tubes performed well in terms of critical dryout at lower heat fluxes. The wicking capabilities of the nanoFLUX and CuO surfaces were thought to be the cause of their improved dryout capabilities at lower heat fluxes, but increased heat fluxes possibly led to dryout of the nanostructures resulting in operation in the Cassie-Baxter state and subsequent reduced wettability.Thesis (PhD)--University of Pretoria, 2020.
Mechanical and Aeronautical Engineering
PhD (Mechanical Engineering)
Unrestricted
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Moraru, Laurentiu Eugen. "Numerical Predictions and Measurements in the Lubrication of Aeronautical Engine and Transmission Components". University of Toledo / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1125769629.
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Šperka, Petr. "In-situ studium změny topografie třecích povrchů v elastohydrodynamickém kontaktu". Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-233978.
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This dissertation thesis deals with elastohydrodynamic lubrication (EHL) of surfaces with real roughness. Systematic study of surface harmonic components behaviour, during their passage of the EHL contact, by other authors led to retrieval of a uniform principle according which individual harmonic components deform inside the contact. Although the amplitude attenuation model can provide rapid tool for more accurate surface assessment in design process it has not been validated on real surfaces till now. The thesis represents pioneering work on quantitative analysis of real surfaces EHD measurements. It contains original and new results with real and model roughness features that in many cases confirm theoretical expectations. Deeper understanding of surface roughness behaviour inside EHL contact, which is typical for machine parts like bearings, gears, cams etc., can help to improve design process of the components and ultimately enable machines and equipment to work with lower energy requirements and higher durability.
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Dahal, Lila R. "Spectroscopic Ellipsometry Studies of Thin Film a-Si:H Solar Cell Fabrication by Multichamber Deposition in the n-i-p Substrate Configuration". University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1365202814.
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Fabricius, John. "Homogenization of some problems in hydrodynamic lubrication involving rough boundaries". Doctoral thesis, Luleå tekniska universitet, Matematiska vetenskaper, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25734.
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This thesis is devoted to the study of some homogenization problems with applications in lubrication theory. It consists of an introduction, five research papers (I–V) and a complementary appendix.Homogenization is a mathematical theory for studying differential equations with rapidly oscillating coefficients. Many important problems in physics with one or several microscopic scales give rise to this kind of equations, whence the need for methods that enable an efficient treatment of such problems. To this end several mathematical techniques have been devised. The main homogenization method used in this thesis is called multiscale convergence. It is a notion of weak convergence in Lp spaces which is designed to take oscillations into account. In paper II we extend some previously obtained results in multiscale convergence that enable us to homogenize a nonlinear problem with a finite number of microscopic scales. The main idea in the proof is closely related to a decomposition of vector fields due to Hermann Weyl. The Weyl decomposition is further explored in paper III.Lubrication theory is devoted to the study of fluid flows in thin domains. More generally, tribology is the science of bodies in relative motion interacting through a mechanical contact. An important aspect of tribology is to explain the principles of friction, lubrication and wear. The mathematical foundations of lubrication theory are given by the Navier–Stokes equation which describes the motion of a viscous fluid. In thin domains several simplifications are possible, as shown in the introduction of this thesis. The resulting equation is named after Osborne Reynolds and is much simpler to analyze than the Navier--Stokes equation.The Reynolds equation is widely used by engineers today. For extremely thin films, it is well-known that the surface micro-topography is an important factor in hydrodynamic performance. Hence it is important to understand the influence of surface roughness with small characteristic wavelengths upon the solution of the Reynolds equation. Since the 1980s such problems have been increasingly studied by homogenization theory. The idea is to replace the original equation with a homogenized equation where the roughness effects are “averaged out”. One problem consists of finding an algorithm for computing the solution of the homogenized equation. Another problem consists of showing, on introducing the appropriate mathematical definitions, that the homogenized equation is the correct method of averaging. Papers I, II, IV and V investigate the effects of surface roughness by homogenization techniques in various situations of hydrodynamic lubrication. To compare the homogenized solution with the solution of the deterministic Reynolds equation, some numerical examples are also included.Godkänd; 2011; 20110408 (johfab); DISPUTATION Ämnesområde: Matematik/Mathematics Opponent: Professor Guy Bayada, Institut National des Sciences Appliquées de Lyon (INSA-LYON), Lyon, France, Ordförande: Professor Lars-Erik Persson, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Tisdag den 7 juni 2011, kl 10.00 Plats: D2214/15, Luleå tekniska universitet
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Wang, Guoqing. "Thin water films driven by air through surface roughness". [Ames, Iowa : Iowa State University], 2008.
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Fong, Tsz Wang. "Surface roughness parameter at synthesis of cubic boron nitride films". access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174143a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.
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Picard, Loïc. "Mise au point d'additifs siliciés pour l'adhérisation d'élastomères silicone sur supports métalliques". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0114.
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L’objectif de ces travaux de thèse était de développer un primaire d’adhésion stable, permettant l’adhérisation de tous types d’élastomères silicone sur une grande majorité de surfaces métalliques, et ce de façon reproductible. Dans un premier temps, une étude bibliographique détaillée des différentes formulations de primaire à base de silanes utilisées pour l’adhésion de tous types d’élastomères silicone (EVC, EVF et LSR) a été effectuée. Pour compléter la compréhension du système métal/primaire d’adhésion/élastomère silicone étudié, trois formulations de primaire, dont une formulation « maison », et trois élastomères silicone ont été analysés et leurs compositions, ainsi que leurs propriétés en adhésion, ont été déterminées. La caractérisation de différentes résines silicone composant la formulation « maison » de primaire a également été effectuée. Cette dernière a ensuite été optimisée en synthétisant de nouvelles résines silicone, en ajustant les taux de chaque composant et en changeant le type de catalyseur. Dans un second temps, la caractérisation physico-chimique des primaires d’adhésion enduits sur la surface d’un métal (aluminium) a été effectuée. La topologie des films de primaire (épaisseur, rugosité et uniformité) et leurs propriétés de mouillage ont été déterminées. Ces résultats ont été complétés par la caractérisation des faciès de rupture des pièces composites métal/primaire/élastomère silicone. À la suite de ces différentes analyses complémentaires, le paramètre gouvernant la sélectivité d’un primaire d’adhésion pour un grade d’EVC a été isolé. Une courbe modèle permettant la formulation d’un primaire polyvalent a été proposée et validée par la formulation d’un primaire d’adhésion pouvant adhérer les différents grades d’EVC sélectionnés pour cette étudeThis PhD work aimed at developing a stable primer of adhesion, allowing the bonding of all types of silicone elastomers onto a vast majority of metallic surfaces, in a reproducible way. In a first approach, a detailed bibliographic study was performed on the different primer based-silane formulations used for the adhesion of any types of silicone elastomers (HCR, RTV and LSR). To better understand the metal/primer/silicone elastomer system, three primer formulations, including a homemade formulation, and three silicone elastomers were analyzed and their compositions, and adhesive properties, were determined. The characterization of different silicone resins entering in the composition of the homemade primer formulation was also carried out. The latter was optimized by synthetizing new silicone resins, by adjusting the content of each component and by changing the type of catalyst. In a second step, the characterization of the physical chemistry of the primer formulations coated on a metal surface (aluminum) was performed. The topology of the primer films (thickness, roughness and uniformity) and their wettability were determined. These information were completed by the characterization of fracture profiles of the composite part metal/primer/silicone elastomer. Following these additional analyses, the parameter governing the selectivity of a primer formulation for a grade of HCR was isolated and a model curve for the formulation of a polyvalent primer was proposed. This curve was validated by the formulation of a primer which can bond the different grades of HCR selected for this study
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Watson, Shannon M. "Impact of large scale substrate roughness on giant magnetoresistive thin films". W&M ScholarWorks, 2005. https://scholarworks.wm.edu/etd/1539623488.
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This dissertation presents an investigation on the effects of large scale roughness on the properties of giant magnetoresistive multilayers. The large scale roughness (sigmarms > 5 nm) is introduced into giant magnetoresistive thin films through the substrate. Current-in-plane (CIP) and current-perpendicular-to-the-plane (CPP) thin films were deposited by dc magnetron and triode sputtering. All films were characterized for roughness, magnetic and electronic behavior.;Our research on both pseudo spin valves and exchange-biased spin valves shows that long length scale roughness does not have a significant detrimental effect on GMR thin films. For the CIP films, we find that a decrease in GMR correlates to an increase in minimum film resistivity. as the minimum resistivity increased, the maximum resistivity increased linearly with a slope ∼1. This suggests that the decrease in GMR may primarily be an effect of increased spin-independent scattering resulting from the increased film roughness. The CPP films showed a similar relationship between minimum and maximum resistance. Studying the effect of such large scale substrate roughness is important for applications in which GMR multilayers are deposited on non-standard substrates and buffer layers including flexible media.
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Yousaf, Yusra. "Surface roughness characterisation of the polymeric films by atomic force microscopy". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/surface-roughness-characterisation-of-the-polymeric-films-by-atomic-force-microscopy(84735afa-6dd4-419a-9821-0646311ab4cd).html.
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Probe microscopy techniques (Atomic Force Microscopy and Kelvin Force Microscopy) have been shown to be instrumental in the analysis of samples; such as resists and nanostructured materials. Through these techniques detailed surface information has been derived, including information such as surface roughness and surface charge distribution. Poly(Methylmethacrylate) (PMMA), remains at the forefront of resists utilised in e-beam lithography in the electronics industry. Surface morphology (specifically roughness) analysis remains a key parameter of investigation, particularly in the examination of polymeric films. This research aimed to investigate PMMA based electron beam resists as well as a novel (SML) resist material in terms of suitability for electron-beam lithography. Various concentrations (5, 7, 8, 9 and 11% w/v) of both PMMA and the novel resist material were spin-coated onto silica substrates. Samples were baked at 180oC for 3 minutes and examined under ultra-high vacuum using Omicron AFM/SPM to derive RMS values in order to assess roughness in addition to thickness measurements taken. SML resists were then utilised in the development of a new digital etch onto InGaAs/InAlAs wafer. The novel, SML resist material was found to offer smoother resist surface even at higher concentrations of polymer, a difference which was observed to be statistically significant (p<0.01). The SML resist was also notably thicker than the comparable PMMA resist (p>0.05) indicating that lower concentrations of the novel resist would be required to achieve the required resist thickness. Digital etching rates were found to be in agreement with previously documented findings. SML was concluded to be a superior resist in terms of thickness and smoothness, with AFM being further established as an essential characterization technique.
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Hu, Jin. "Experimental and theoretical investigation of roughness effects on thin laminar fluid films". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ27957.pdf.
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Rahman, Mohammed Magfurar. "MAPPING SURFACE SOIL MOISTURE AND ROUGHNESS BY RADAR REMOTE SENSING IN THE SEMI-ARID ENVIRONMENT". Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1193%5F1%5Fm.pdf&type=application/pdf.
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ROGER, JEAN-PAUL. "Contributions a l'etude des surfaces, interfaces et films minces par la methode mirage". Paris 6, 1988. http://www.theses.fr/1988PA066509.
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Detection in situ d'un depot metallique sur une electrode rugueuse avec une sensibilite d'une fraction de couche monoatomique; analyse et modelisation des effets de rugosite pour des surfaces metalliques, caracterisation optique et thermique de couches minces semiconductrices et mise en evidence d'une absorption de surface
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Trigoulet, Nicolas. "Probing barrier-type anodic alumina films on nano-patterned substrates". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/probing-barriertype-anodic-alumina-films-on-nanopatterned-substrates(7c888ffd-f901-4993-b30d-05fc0a3bf514).html.
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The growth of barrier-type anodic alumina films formed by anodizing relatively rough substrates has been shown to proceed by high field ionic conduction. As a result of the ionic transport and the induced plasticity, smoothing of the oxide surfaces and the metal/oxide interfaces arises. However, such a smoothing model was deduced from topographical observations and, therefore little insight was gained about the transport mechanism leading to the flattening of the anodized specimens. Recently, the development of porous anodic alumina has been demonstrated to proceed by coupled ionic migration and material flow resulting from the field-induced mechanical stress. For rough metal surfaces, the electric field distribution is non-uniform across the specimen surface. Considering the square-dependence of the electrostrictive stress on the electric field and the distribution of the electric field across surface, a significant gradient of mechanical stress may arise across the anodic oxide layer during anodizing. As a result, stress-driven transport may participate, in addition to high field ionic conduction, to the smoothing of the specimen surface. Transport mechanisms were investigated during anodizing of patterned superpure aluminium specimens, by examination of the distributions of incorporated species, used as markers and tracers. The nature of the migration processes have been determined in correlation with the changes in the concentration of the tracer profiles as well as the variations in the anodic oxide film compositions.
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Rayan, Mihir K. "Spray deposition of biomolecular thin films". [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002681.
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Lehmann, Daniel, Falko Seidel i Dietrich R. T. Zahn. "Thin films with high surface roughness: thickness and dielectric function analysis using spectroscopic ellipsometry". Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-136724.
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An optical surface roughness model is presented, which allows a reliable determination of the dielectric function of thin films with high surface roughnesses of more than 10 nm peak to valley distance by means of spectroscopic ellipsometry. Starting from histogram evaluation of atomic force microscopy (AFM) topography measurements a specific roughness layer (RL) model was developed for an organic thin film grown in vacuum which is well suited as an example. Theoretical description based on counting statistics allows generalizing the RL model developed to be used for all non-conducting materials. Finally, a direct input of root mean square (RMS) values found by AFM measurements into the proposed model is presented, which is important for complex ellipsometric evaluation models where a reduction of the amount of unknown parameters can be crucial. Exemplarily, the evaluation of a N,N’-dimethoxyethyl-3,4,9,10-perylene-tetracarboxylic-diimide (DiMethoxyethyl-PTCDI) film is presented, which exhibits a very high surface roughness, i.e. showing no homogeneous film at all.
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Bodart, Vincent. "Controle de la croissance d'empilements ultra-minces carbone tungstene et silicium-tungstene par ellipsometrie cinetique in-situ : application aux miroirs pour x-mous". Paris 7, 1987. http://www.theses.fr/1987PA077094.
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Dans le but d'obtenir des reflecteurs de bragg pour rx mous, on realise par pulverisation avec controle ellipsometrique in situ des empilements de 200 couches nanometriques. Observation de la formation des interfaces a l'echelle atomique, evaluation des rugosites d'interface
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Espinosa, Jorge D. "De-wetting of cobalt thin films on sapphire". Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5314.
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Thesis (Ph. D.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains ix, 106 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 102-105).
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Agra-Kooijman, Deña Mae G. "Liquid Crystal Alignment and Relaxation Dynamics at Surface Modified Thin Polymer Films". Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1228148263.
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Gilliam, David R. "A study of contact between a profile meter stylus and polymer films on roughened substrates". Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45727.
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When a polymer film is deposited onto a roughened substrate, the film masks over the underlying substrate roughness. Then when attempting to measure the roughness of the polymer film surface using a stylus-type profile meter, the pressure between the tip of the stylus and the film is sufficient to plastically deform the polymer surface. The result is a possible erroneous measurement of the surface roughness of the polymer film. This thesis reports on attempts to quantify the actual roughness of the polymer film from the measurement obtained by the profile meter. Extensive surface profile data were collected and analyzed to determine the characteristics of the surface of the substrate and of the coating on the substrate. The tracks made by the stylus in the film were then observed in a scanning electron microscope, from which the depth of the stylus tracks were measured. The effects of the film thickness, stylus traversing speed, and substrate roughness on the stylus penetration depth, the variation in the depth, and the measured film roughness are assessed and discussed. It was found that using the fastest stylus traversing speed minimizes the variation of the stylus penetration depth and thus results in the most accurate measurement of the film surface. To predict this stylus indentation depth, a plane strain plastic deformation model is developed using slip-line field theory. It is found that the slip-line model gives good estimates of the stylus indentation depth when the film thickness is large.Master of Science
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Nemani, Lingeshwar. "Effect of SnO2 Roughness and CdS Thickness on the Performance of CdS/CdTe Solar Cells". Scholar Commons, 2005. https://scholarcommons.usf.edu/etd/790.
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Textured SnO2 films as TCO have been investigated to determine the effect of surface roughness on the performance of CdS/CdTe solar cells. Film roughness was controlled by varying the substrate temperature. Characterization of the SnO2 films has also carried out using AFM measurements. It was found that increase in substrate temperature results in increased roughness of the film.
A series of cells were fabricated with different CdS thicknesses to determine the combined effect of SnO2 roughness and CdS thickness. As a part of fabrication process, cells were subjected to different post deposition treatments. It was observed that roughness seems to be critical when CdS remained in the final device is thin. The performance of CdS/CdTe devices fabricated was characterized using J-V and spectral response measurements. It was found that cells with initial CdS thickness of 1000 showed better performance than those with thicker CdS for the same roughness of SnO2.
Conversion efficiency of 13.37% was achieved by increasing the SnO2 roughness and depositing thicker CdS initially.
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Herffurth, Tobias [Verfasser], Andreas [Akademischer Betreuer] Tünnermann, Richard [Akademischer Betreuer] Kowarschick i Miloslav [Akademischer Betreuer] Ohlidal. "Light scattering and roughness analysis of optical surfaces and thin films / Tobias Herffurth. Gutachter: Andreas Tünnermann ; Richard Kowarschick ; Miloslav Ohlidal". Jena : Thüringer Universitäts- und Landesbibliothek Jena, 2015. http://d-nb.info/1072622106/34.
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Mallett, Jonathan James. "Electrochemical deposition, characterisation of metal films, and the modification of electrodes by near-field photolithography". Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324298.
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Avila, Solis Sandra Milagros. "Evaluación in vitro de la microrugosidad superficial de dos resinas tipo Bulk Fill inmersas a dos bebidas rehidratantes con pH de 2,79 y 3,3". Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/628127.
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Objetivo: Comparar in vitro la rugosidad superficial de una resina compuesta tipo BulkFill: Aura® BulkFill (SDI) con la resina Tetric N-Ceram® BulkFill (Ivoclar Vivadent) al ser inmersas a dos bebidas rehidratantes: Sporade® y Gatorade®.
Materiales y métodos: Se utilizaron 88 especímenes de resina divididos en cuatro grupos, confeccionados con una matriz metálica (10mm x 4mm). Se insertó las resinas con una espátula de resina, y se fotoactivó con la lámpara Elipar LedTM, con una intensidad de 1200 mW/cm2. Se sumergieron los especímenes en agua destilada. A las 24 horas, se midió la rugosidad con el rugosímetro Mitutoyo SJ-210P. Luego, se realizó la inmersión en bebidas rehidratantes y se midió la rugosidad final a los 7 días.
Resultados: La rugosidad inicial y final de las resinas Aura® BulkFill (SDI) y Tetric N-Ceram® BulkFill (Ivoclar Vivadent) presentaron diferencias significativas después de la inmersión en bebidas rehidratantes. Para los especímenes de Aura® BulkFill (SDI) al someterla a Sporade® se encontró una media inicial de 1.20 y una media final de 1.76 y los valores para Gatorade® fueron 0.77 y 1.73. Mientras que la rugosidad superficial de Tetric N-Ceram® BulkFill (Ivoclar Vivadent) al sumergirla en Sporade® fue 0.82 y 1.55, y en Gatorade® 0.77 y 1.73. Al comparar la diferencia de la rugosidad superficial final e inicial (deltas), la resina Aura® BulkFill presentó diferencias significativas mientras que, Tetric N-Ceram® BulkFill no tuvo diferencias al sumergirlas en ambas bebidas rehidratantes.
Conclusiones: Las resinas estudiadas incrementaron su rugosidad luego de ser inmersas a las bebidas mencionadas.Objective: To compare in vitro the surface roughness of a BulkFill composite resin: Aura® BulkFill (SDI) with Tetric N-Ceram® BulkFill resin (Ivoclar Vivadent) when immersed in two rehydration drinks: Sporade® and Gatorade®. Materials and methods: 88 resin specimens divided into four groups were used, with a metal matrix (10 mm x 4 mm). The resins were inserted with a resin spatula, and photo-activated with the Elipar LedTM lamp, with an intensity of 1200 mW/cm2. The specimens were immersed in distilled water. After 24 hours, the roughness was measured with the Mitutoyo SJ-210P rugosimeter. Then, the immersion in rehydration drinks was performed and the final roughness was measured after 7 days. Results: The initial and final roughness of the resins Aura® BulkFill (SDI) and Tetric N-Ceram® BulkFill (Ivoclar Vivadent) showed significant differences after immersion in rehydration drinks. For specimens of Aura® BulkFill (SDI) when subjected to Sporade® an initial mean of 1.20 and a final average of 1.76 was found and the values for Gatorade® were 0.77 and 1.73. While the surface roughness of Tetric N-Ceram® BulkFill (Ivoclar Vivadent) when immersed in Sporade® was 0.82 and 1.55, and in Gatorade® 0.77 and 1.73. When comparing the difference of the final and initial surface roughness (deltas), the Aura® BulkFill resin showed significant differences while, Tetric N-Ceram® BulkFill did not have differences when immersing them in both rehydration drinks. Conclusions: The resins studied increased their roughness after being immersed in the aforementioned beverages.
Tesis
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Mammei, Russell Rene. "Thin Films for the Transport of Polarized Ultracold Neutrons for Fundamental Symmetry Study". Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/28714.
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The use of ultracold neutrons (UCN) to study fundamental parameters such as the neutron lifetime and decay correlations in polarized neutron beta decay are poised to make significant contributions to our understand of the Standard Model and its extensions. To this end, the UCNA experiment is pursuing a precision measurement (0.2%) of the angular correlation between the neutron spin and the direction of emission of the electron in polarized neutron decay (the ``A'' asymmetry). The UCNA experiment makes use of the spallation-driven solid deuterium (SD2) UCN source at the Los Alamos Neutron Science Center (LANSCE). The UCN leave the source and are 100% polarized by passing through a strong magnetic field before their decay is observed by a very sensitive electron spectrometer.
UCN guides facilitate the transfer of UCN from the source to the spectrometer. Common guide materials include stainless steel, copper, aluminum, and quartz. Often a thin film is applied to these components to increase their ability to transport/bottle and preserve the polarization of UCN. In the region of the SD2 UCN source, nickel-58 films are applied, whereas once the UCN are polarized, diamond-like carbon (DLC) films are employed. This dissertation covers the application, process developments, and characterization of these coatings. In addition a study concerning the surface finish resulting from the mechanical polishing and electropolishing of the guides that make up the UCNA beamline is presented.
Ph. D.
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Melo, Leonidas Lopes de. "Dinâmica de crescimento de filmes de platina e ouro". Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-26022014-093131/.
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O caráter aleatório e não homogêneo do crescimento de filmes finos, por processo de deposição, leva à formação de uma superfície rugosa que obedece, em geral, a uma geometria fractal. A dinâmica de crescimento da superfície do filme pode ser descrita por meio de modelos de crescimento discretos, simulações numéricas e equações diferenciais estocásticas. Os modelos e as equações nos fornecem os expoentes críticos, que descrevem o comportamento da rugosidade com a escala de observação e tempo de deposição. Crescemos filmes de platina e ouro através da técnica de implantação e deposição de íons por imersão em plasma metálico. Determinamos experimentalmente os expoentes críticos por meio de microscopia de tunelamento. Comparamos os nossos resultados experimentais com previsões dadas por alguns modelos teóricos. Verificamos que há um bom acordo entre eles e as previsões dadas pela equação estocástica de Kardar, Parisi e Zhang. A estrutura cristalina dos materiais também foi analisada por meio de difração de raios x.The randomness and inhomogeneities in the growth of thin films generate a rough surface obeying, in general, fractal geometry. The growth dynamics of film surface can be described by theoretical discrete models, numerical simulations and stochastic differential equations. Models and equations give the critical exponents that describe the behavior of roughness with the observation scale and deposition time. We have synthesized platinum and gold films by metal plasma immersion ion implantation and deposition. We have measured the critical exponents by Scanning Tunneling Microscopy. Our experimental results were compared with some theoretical models predictions. We verified that there is a good agreement between them and the theoretical predictions given by the Kardar, Parisi and Zhang stochastic equation. The crystallographic structure was also analyzed by X-ray diffraction.
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Duvivier, Pierre-Yves. "Étude expérimentale et modélisation du contact électrique et mécanique quasi statique entre surfaces rugueuses d'or : application aux micro-relais mems". Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2010. http://tel.archives-ouvertes.fr/tel-00740248.
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L'étude du contact électrique quasi statique à plusieurs échelles permet de comprendre celui des micro-relais MEMS. Au cours de ce travail, une modélisation fine du contact est développée pour valider des lois de comportement établies à partir des mesures obtenues grâce à la mise au point de deux dispositifs expérimentaux originaux : la balance de précision, qui permet de réaliser un contact à l'échelle macroscopique entre barreaux croisés recouverts des films minces des matériaux à tester, et un nanoindenteur instrumenté pour la mesure électrique reproduisant un micro-contact identique à celui des micro-relais. Ils permettent tous deux de mener une étude comparative de différents échantillons en fonction de la force (de la dizaine de µN à quelques N), du courant (du µA à l'A), de l'état de surface (rugosité) ou encore du temps ; le contact étant caractérisé par sa résistance électrique. Ce travail concerne principalement le contact réalisé entre films minces en Au, matériau de contact de référence pour les applications micro-relais MEMS. L'étude des contacts de grande dimension a néanmoins été élargie à Ru, Rh, Pt et à l'alliage Au-Ni.Les résultats obtenus à l'aide de la balance de précision ont démontré la nécessité de prendre en compte l'influence de la configuration en film mince des matériaux de contact, tant du point de vue mécanique (rugosité) qu'électrique (répartition des lignes de courant). Leur comparaison à une modélisation statistique du contact rugueux donne des résultats satisfaisants. Cette approche a par ailleurs nécessité le développement d'un algorithme d'analyse d'image des relevés topographiques réalisés au microscope à force atomique, permettant ainsi de quantifier précisément les positions, taille et rayon de courbure de chaque aspérité de la surface.Les mesures effectuées à l'aide du nanoindenteur ont mis en évidence l'effet de la durée de fermeture des microcontacts sur la valeur de la résistance électrique. Le fluage des aspérités serait en partie responsable de la décroissance temporelle observée, aboutissant à des valeurs de résistance limite comparables à celles calculées à l'aide d'une modélisation numérique du contact entre des aspérités discrétisées et une sphère lisse.
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Pepenene, Refuoe Donald. "Macroscopic and Microscopic surface features of Hydrogenated silicon thin films". University of the Western Cape, 2018. http://hdl.handle.net/11394/6414.
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Magister Scientiae - MSc (Physics)An increasing energy demand and growing environmental concerns regarding the use of fossil fuels in South Africa has led to the challenge to explore cheap, alternative sources of energy. The generation of electricity from Photovoltaic (PV) devices such as solar cells is currently seen as a viable alternative source of clean energy. As such, crystalline, amorphous and nanocrystalline silicon thin films are expected to play increasingly important roles as economically viable materials for PV development. Despite the growing interest shown in these materials, challenges such as the partial understanding of standardized measurement protocols, and the relationship between the structure and optoelectronic properties still need to be overcome.
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Boukezzata, Messaoud. "Mecanismes d'oxydation des si-lpcvd fortement dopes au bore". Toulouse 3, 1988. http://www.theses.fr/1988TOU30183.
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Etude de la cinetique et des mecanismes d'oxydation thermique de films dopes a 210**(20) cm**(-3) b "in situ" et par implantation post-depot. Les resultats prennent en compte les influences du mode de dopage et de la microstructure initiale des films (qui varie d'un etat quasi-amorphe a un etat nettement polycristallin). Leur analyse s'appuie sur a) un logiciel de modelisation de l'oxydation de si et la comparaison avec la cinetique d'oxydation de temoins monocristallins qui permettent de les exprimer en termes de constante de diffusion d et de la vitesse de reaction de surface k::(s) de l'oxydation, b) la comparaison entre depots non dopes, dopes a b par implantation ou "in situ" et c) le suivi des proprietes structurales (rugosite, diagrammes rheed, observations tem) et electroniques des films
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Silva, Marcelo de Assumpção Pereira da. "Análise de superfícies de filmes finos de polianilina depositados em diferentes substratos por microscopia de força atômica". Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-06062007-191316/.
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Este trabalho apresenta um estudo sobre a morfologia de filmes finos de polianilina, fabricados por diferentes processos e depositados sobre diferentes substratos pela técnica de microscopia de força atômica (AFM). Os processos usados para a fabricação dos filmes foram o de espalhamento fluido, o de centrifugação, o de auto montagem e o eletroquímico. Os substratos usados foram: vidro, ouro/cromo/vidro, quartzo, ITO, silício e mica. Além da análise visual da qualidade dos filmes, ou seja, do grau de recobrimento do substrato e da uniformidade dos filmes, foram feitas análises de parâmetros quantitativos através de medidas de rugosidade. Usando modelos de crescimento como o de deposição balística e de análise de rugosidade, como o da densidade do espectro de potência, (transformada de Fourier da rugosidade da imagem em função da freqüência espectral) em superfícies auto-afins, foram obtidos parâmetros como: expoente de rugosidade, comprimento característico de correlação e dimensão fractal. Apesar dos filmes de polianilina serem sistemas extremamente complexos, - compostos de macromoléculas formando uma estrutura semicristalina - os parâmetros obtidos por esses modelos, que foram elaborados para sistemas bem mais simples, deram resultados muito bons e auto-coerentes. Como conclusão, mostramos que a conjuminação da técnica de microscopia de força atômica com esses modelos compõem um método poderoso para o estudo de filmes finos orgânicos.This work presents a detailed study about the characteristic of thin films of polyaniline, fabricated by different methods and deposited over different substrates using Atomic Force Microscopy technique (AFM). The processes used for film depositions were casting, spin-coating, self-assembly, and the electrochemistry methods. The substrata used were: glass plates, gold/chromium/glass, quartz, ITO, silicon, and mica. Besides the visual analysis, that observes the film uniformity and verifies the coating degree of the substratum, the application of some mathematical models was employed to obtain quantitative parameters about the roughness of the film surfaces. From the ballistic deposition model, developed to explain growing processes, and the power spectrum density that takes the Fourier transform of the roughness in function of the spectral frequency, both developed for self-affine surfaces, it was obtained parameters as: the roughness exponent, the correlation characteristic length, and the fractal dimension. Despite the highly complex structure of the polyaniline - composed by macromolecules forming a semicrystalline structure- the obtained parameters by such models developed for very simple systems, provided reasonable and self-coherent results. As a final result of this work we showed that the synergy between the AFM technique and the above mentioned models compose a powerful method for the study of thin organic films.
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Blažková, Naďa. "Povrchová topografie a-CSi:H vrstev připravených v kontinuálním režimu PECVD". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2018. http://www.nusl.cz/ntk/nusl-376884.
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The thesis describes surface topography of a-CSi:H films deposited by continuous wave plasma enhanced chemical vapor deposition (PECVD) based on tetravinylsilane monomer (TVS). Thin films are completely used in many fields of modern technologies and their physical and mechanical properties are affected by thin film preparation techniques. In this thesis the thin films were deposited by PECVD method on silicon wafers with the pure TVS monomer. Deposited samples were topographically described and analyzed using atomic force microscopy (AFM). The main characteristics which were described are RMS roughness, autocorrelation function and a size distribution of grains on the thin film surface. Analysis was realized with two sets of samples with different powers and thickness. The main results were statistically evaluated like a mixture of object on the surface prepared in different deposition conditions.
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Albuquerque, Diego Aparecido Carvalho. "Deposição e caracterização de filmes ultrafinos de óxido de titânio depositados por Sputtering RF". Universidade Federal de São Carlos, 2012. https://repositorio.ufscar.br/handle/ufscar/1167.
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This work studied ultrathin films of titanium oxide deposited by the technique r. f. reactive sputtering with different oxygen flows and different deposition times. Optical properties were studied (ultra-violeta/Visível) and the surface morphology (Atomic Force Microscopy). The composition and structural properties of the films were analyzed by X-ray diffraction and Rutherford Backscattering Spectroscopy. The films are amorphous and rough (fractal dimension around 2.6 to 2.7 and roughness around 1.6 to 2.5 nm). The stoichiometry was fairly close to the titanium dioxide (TiO2). The optical energy Gap obtained by three different models presented values between 3.0 to 3.5 eV.
Neste trabalho foram estudados filmes ultrafinos de óxido de titânio depositados pela técnica sputtering reativo r.f., com diferentes fluxos de oxigênio e diferentes tempos de deposição. Foram estudadas as propriedades ópticas (Ultra-Violeta/Visível), bem como a morfologia da superfície (Microscopia de Força Atômica). As propriedades estruturais e a composição dos filmes foram estudadas por Difração de raios-X e por Rutherford Backscattering Spectroscopy. Os filmes são amorfos e com superfície rugosa (dimensão fractal em torno de 2,6 - 2,7 e rugosidade em torno de 1,6 - 2,5 nm). A estequiometria ficou bastante próxima do dióxido de titânio (TiO2). A energia do Gap óptico obtido por três modelos distintos apresentou valores entre 3,0 3,5 eV.
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Abreu, Caio Palumbo de. "Deposição e caracterizações óptica e morfológica de filmes finos de TIOX depositados por sputtering R.F". Universidade Federal de São Carlos, 2013. https://repositorio.ufscar.br/handle/ufscar/1168.
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Previous issue date: 2013-02-19This work studied ultrathin films of titanium oxide were deposited on two substrates, such as pure Si (100) and glass corning 7059, by using r.f. magnetron sputtering with different oxygen flows and maintaining another parameters constant. For the purpose of this work, while keeping all parameters constant, varying only the oxygen flow (reactive gas), it was expected to identify the flow of transition between films of substoichiometric TiOx and TiO2 films, and analyze whether there forming nanostructured TiO2 films because the literature shows that variation of control parameters important characteristics of the nanoparticles as medium sized fraction of coverage of the substrate crystal structure and stoichiometry. The chemistries of the ultrathin films were analyzed through technique of Rutherford Backscattering Spectroscopy (RBS), the surface morphology by Atomic Force Microscopy (AFM), the crystallinity by X-Ray Diffraction (XRD) and the optical properties by UV-vis Spectroscopy. Were deposited ultrathin films with substoichiometric compositions for depositions with 0.10% O2 and 0.35% O2. For depositions between 0.67% O2 and 6.00% O2, films were obtained with concentrations of [O]/[Ti] of about 1.9, near the chemical composition of titanium dioxide (TiO2). Films with concentrations close to the TiO2 showed amorphous, but with characteristics of formation of anatase phase. The optical properties presented optical gap values between 3.33 eV and 3,78 eV and had no significant variation, as calculated by E03, E04 and ETauc methods. The roughness of the films decreased proportionally with increasing oxygen flow in the depositions.
No presente trabalho foram estudados filmes finos de óxido de titânio, depositados em dois substratos, Si (100) e vidro Corning 7059, por meio da utilização da técnica de pulverização catódica por rádio freqüência - magnetron sputtering r.f. - com diferentes fluxos de oxigênio e os outros parâmetros mantidos constantes. Com isso, esperava-se identificar o fluxo de transição entre os filmes de TiOx subestequiométricos e filmes de TiO2, analisar se haveria formação de filmes de TiO2 nanoestruturados e diferenças entre os gaps ópticos. As composições químicas dos filmes finos foram analisadas por meio da técnica de espectroscopia de retroespalhamento Rutherford (RBS), a morfologia da superfície por Microscopia de Força Atômica (AFM), a cristalinidade por difração de raios-X (XRD) e as propriedades ópticas por espectroscopia UV-Visível. Foram depositados filmes finos com composições subestequiométricas nas deposições com 0,10% de O2 e 0,35% de O2. Para deposições de O2 entre 0,67% e 6,00%, os filmes foram obtidos com concentrações de [O]/[Ti] de aproximadamente 1,9, ou seja, perto da composição química do dióxido de titânio (TiO2). Filmes com concentrações de [O]/[Ti] próximas ao TiO2 apresentaram-se amorfas, mas com características de formação de fase anatase. As propriedades ópticas não apresentaram nenhuma variação significativa nos valores de gap óptico, com valor entre 3,33 eV e 3,78 eV, calculado pelos métodos E03, E04 e ETauc. A rugosidade dos filmes diminuiu proporcionalmente com o aumento do fluxo de oxigênio nas deposições.
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Pereira, Anderson de Jesus. "Efeito de uma barreira cinética em modelos de crescimento de interfaces com mobilidade limitada". Universidade Federal de Viçosa, 2012. http://locus.ufv.br/handle/123456789/4264.
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Previous issue date: 2012-07-19Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
In thin film growth, morphology is one of the most important characteristics. In particular, the appearance of self-assembled three-dimensional structures, characterized by mounds, with origin attributed to barriers that cause an imbalance between up- and downhill currents in stepped surfaces. In this dissertation we study the effects of the introdution of a kinetic barrier that appears when we include the normal diffusion to the substrate in the migration between different planes in the models ofWolf-Villain and Das Sarma-Tamborenea. The aim is to investigate the morphological changes and growth dynamics of interfaces due to this barrier in one and two-dimensional substrates. In our simulations simulations, we observed interfaces with structures characterized by the presence of mounds, with typical morphological patterns observed in films with self-assembled three-dimensional structures, not observed for the WV and DT models without the kinetic barrier. In the WV and DT models with kinetic barrier in d = 1 + 1 and d = 2 + 1 dimensions, we find that the growth exponent goes to 1=2 in the asymptotic limit. We calculate the ascendent and descendent currents between terraces and determine the average flow of particles in steps per site. We observe a descendent current in the steps for both models, approaching an zero value after a long time, where we would expect a balance between upward and downward particle flow and also saturating the width interface.
No crescimento de filmes finos, a morfologia é uma das mais importantes características. Em particular, o aparecimento de estruturas tridimensionais auto-arranjadas, caracterizada por morros, com origem atribuída a barreiras que causam um desequilíbrio entre o fluxo de partículas ascendente e descendente em superfícies com degraus. Nessa dissertação estudamos os efeitos da introdução de uma barreira cinética que aparece quando incluímos a difusão normal ao substrato na migração entre planos diferentes nos modelos de Wolf-Villain (WV) e Das Sarma-Tamborenea (DT). O objetivo é investigar as alterações morfológicas e a dinâmica de crescimento de interfaces devido a essa barreira em substratos unidimensionais e bidimensionais. Em nossas simulações observamos inferfaces com estruturas caracterizadas pela presença de morros, com padrões morfológicos típicos observados em filmes com estruturas tridimensionais auto-arranjadas o que não é observado para os modelos WV e DT, sem a barreira cinética. Nos modelos WV e DT com barreira cinética em d = 1 + 1 e d = 2 + 1 dimensões, encontramos que o expoente de crescimento vai para 1=2 no limite assintótico. Calculamos a corrente ascendente e descendente entre terraços e determinamos o fluxo médio de partículas nos degraus por sítio. Observamos uma corrente descendente nos degraus para ambos os modelos, que se aproxima de um valor nulo após um tempo longo, onde esperamos um equilíbrio entre o fluxo de partículas ascendentes e descendentes e além disso, a saturação da largura da interface.
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Brunot-Gohin, Céline. "Optimisation des états de surface du titane et des alliages en nickel-titane par des films multicouches de polyélectrolytes". Phd thesis, Université Claude Bernard - Lyon I, 2009. http://tel.archives-ouvertes.fr/tel-00771411.
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L'optimisation des états de surface constitue un enjeu majeur pour les biomatériaux utilisés dans le domaine biomédical. Le titane (Ti) et ses alliages à base de nickel (NiTi) restent à ce jour les biomatériaux métalliques de prédilection dans nos applications cliniques en Odontologie (implants dentaires, instruments endodontiques, et arcs orthodontiques). Le but de nos recherche est d'optimiser les surfaces du Ti et NiTi en les fonctionnalisant par des films multicouches de polyélectrolytes (FMP). Notre travail propose d'étudier différents paramètres devant être impérativement validés avant d'envisager une quelconque application biomédicale in vivo avec ce type de revêtement. Une recherche bibliographique exhastive appuie notre recherche expérimentale. Le premier axe du travail propose de déterminer si des FMP peuvent effectivement s'adsorber chimiquement sur le Ti et le NiTi. qui plus est, une étude biologique est réalisée avec des cellules humaines pour tester la biocompatibilité des ces surfaces fonctionnalisées. La deuxième partie se concentre sur la biocompatibilité de la couche précurseur des FMP à base de polyéthyléneimine (PEI). Les résultats mettent en lumière une certaine cytotoxicité de la PEI envers des ostéoblastes et des fibroblastes gingivaux humain. Pour clore ce travail, nous réalisons des essais de stérilisation afin d'évaluer l'influence d'un tel procédé sur les FMP en terme de caractérisations physico-chimique et biologique des surfaces. La perspective d'une application biomédicale avec les FMP semble prometteuse, notamment en y introduisant des molécules bioactives. Cependant, bien d'autres paramètres sont encore à étudier avant d'envisager une application expérimentale et/ou clinique in vivo. Nous pouvons citer par exemple, le vieillissement des FMP, leur comportement en milieu salivaire ou fluoré, ou encore leur résistance à l'usure. Ces différents éléments rentrent dans les perspectives d'un projet post-doctoral.
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Chagroune, Lakhdar. "Modélisation de l'émissivité d'une surface en utilisant une approche fractale". Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL115N.
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L’oxydation des échantillons de tungstène chauffés par effet Joule, est réalisée dans un spectrophotomètre infrarouge sous atmosphère contrôlée (10^-2 torr d'oxygène) et à des températures T ≥ 1100 K pour créer des surfaces rugueuses. La morphologie de la couche d'oxyde est caractérisée par analyseur d'images à partir du cliché d'une coupe réalisée par microscopie électronique à balayage. On assimile l'oxyde à une superposition de films minces, dont l'un hétérogène, contenant la rugosité, est étudié par la théorie de BRUGGMAN en vue de déterminer sa constante diélectrique. Les propriétés optiques d'un corps hétérogène sont interprétées généralement à partir de la théorie des milieux dispersés qui ne tient compte que très partiellement de la rugosité des surfaces. Ce travail expose la conception et l'élaboration d'outils destinés à caractériser l'influence de la complexité et de la forme de la rugosité sur l'émissivité d'une surface, selon une approche originale qui tient compte de la morphologie réelle des surfaces (profils fractals). Le calcul de l'émissivité d'une surface rugueuse est mené de la manière suivante: numérisation des profils expérimentaux calcul de la constante diélectrique d'une couche homogène optiquement équivalente contenant la rugosité du profil considéré calcul du facteur moyen de dépolarisation gm par une méthode originale de remplissage du profil par des ellipsoïdes utilisation de la théorie des films minces, pour calculer l'émissivité monochromatique et directionnelle de cette surface. Une étude analogue a été réalisée sur des profils théoriques crées par interpolation fractale, pour la validation théorique du modèle. Nous mettons en évidence une relation entre la dimension fractale, l'émissivité et le facteur de dépolarisation
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Ortega, Luc. "Caractérisation par rayons X des isolants amorphes d'oxynitrures de silicium, SiOxNyHz, préparés en couches minces par PECVD". Grenoble 1, 1993. http://www.theses.fr/1993GRE10169.
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Ce memoire est consacre a la caracterisation des couches minces amorphes d'oxynitrures de silicium sioxnyhz preparee par pecvd. Ces materiaux isolants jouent un role de plus en plus important dans le domaine de la microelectronique. Ils ont donne lieu a un programme europeen de recherche esprit-deson qui a implique six laboratoires europeens et dans lequel nous sommes intervenus. Nous nous sommes attaches a caracteriser les oxynitrures de silicium a l'aide de plusieurs techniques x: reflectometrie x, diffusion des rayons x en incidence rasante, exafs, xanes et xps. L'epaisseur, la densite et la rugosite des couches ont ete determinees. Il est apparu que les couches sont peu denses pour les compositions proches du nitrure de silicium a cause de la presence d'hydrogene. La densite evolue en fonction du taux d'incorporation d'oxygene par rapport a l'azote, o/(o+n), dans le materiau avec une transition caracteristique pour o/(o+n)=0,4 qui est a relier aux proprietes physiques des oxynitrures. Par ailleurs, nous avons trouve une forte rugosite pour les couches deposees sur fluorure de calcium liee au mode de croissance. L'etude structurale a constitue notre principal centre d'interet et a necessite la mise en uvre de plusieurs techniques experimentales du fait que le materiau est compose de plusieurs especes atomiques. Les experiences de diffusion des rayons x ont ete realisee en incidence rasante afin de minimiser la contribution parasite due au substrat. Il est montre que la structure des oxynitrures de silicium etudies n'est pas constituee d'un simple melange des phases binaires: silice et nitrure de silicium amorphes. Un effet sur les premieres distances interatomiques si-o et si-n a ete observe qui a ete interprete par une certaine homogeneisation des sites si-o-si et si-nh-si pour les oxynitrures de composition intermediaires. D'autres caracteristiques sont aussi rapportees
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劉性義. "In type Ⅱ roughness Superconductor film the Nucleation fieldΗc3". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/55911786058063365720.
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Liao, Yi-Chiann, i 廖怡茜. "Effect of surface roughness of SnO2 film for light trapping phenomenon". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/35808422006810899802.
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碩士國立成功大學
材料科學及工程學系碩博士班
97
Transparent Conductive Oxide (TCO) thin films, which show high conductivity and high transmittance in the visible wavelength range, have been used as the transparent electrode in solar cell devices. For application in solar cell, increasing surface roughness of transparent conductive oxide thin films is able to enhance light scattering at the rough surface and increase light path. This is so-called light trapping effect. Such an effect can increase the light absorption in solar cell and enhance the efficiency of solar cell. TCO material used in this study was RF-magnetron-sputtered tin dioxide thin film. The surface of SnO2 film was treated by chemical etching method. The etching effect on surface morphology of SnO2 film before and after heat-treatment was investigated. The effect of different sputter pressure on the surface morphology and light scattering was also examined. In addition, a patterned structure was established on glass substrates using lithography method and then followed by sputtering SnO2 film. The light scattering of patterned substrates was also discussed. The experimental results show the electrical and optical properties of SnO2 film increased after heat treatment, and the etched SnO2 film had different appearance. The etching effect is more pronounced on as-deposited film than the heat-treated film because of the densification on heat-treated film. Also, the structure of SnO2 film was influenced by different sputter pressure. The surface of SnO2 film after etching show island-like structure, and the island-like structure was more noticeable with decreasing sputter pressure, and it also enhance light scattering. SnO2 film at 1*10-2torr have the strongest light scattering with Haze value about 30% to 50% (1000nm~350nm). In addition, the regular pattern on glass substrates using lithography method was prepared, and followed by sputtering of SnO2 film. So the SnO2 film with patterned surface can be prepared without sacrificing electrical property of SnO2 film. The results showed that the SnO2 film with micrometer size (about 10μm) pattern can increase the Haze value. The SnO2 film with 2-D pattern show better light trapping effect than that with 1-D pattern. The Haze value of SnO2 film with pyramidal pattern is about 22%.
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Hwu, Chwan-Jing, i 胡傳菁. "Surface Roughness Effects on the Squeeze Film Characteristics of Partial Journal Bearing". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/18904834786032075178.
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碩士中原大學
機械工程學系
88
The present study examines the surface roughness effects on the squeeze film characteristics of a finite partial journal bearing. We can derive the Reynolds’ equation from the momentum equations and the continuity equation and further adopt the stochastic models to develop the stochastic Reynolds’ equation describing the uniform, isotropic roughness. After obtaining the pressure distribution of the squeeze film, we can calculate the surface roughness effects on the squeeze film characteristics. The results of the study show that the surface roughness effects have negative influence both on the load-carrying capacity or the time-height relationship.