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1
Imam, Mewlude. « CVD Chemistry of Organoborons for Boron-Carbon Thin Film Depositions ». Doctoral thesis, Linköpings universitet, Tunnfilmsfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-141548.
Texte intégralRésumé :
Boron-carbon thin films enriched with 10B are potential neutron converting layers for 10B-based solid state neutron detectors given the good neutron absorption cross section of 10B atoms in thin films. The common neutron-transparent base material, Al (melting point 660 °C), limits the deposition temperature and the use of chlorinated precursors forming corrosive by-products such as HCl. Therefore, the organoborons triethylboron B(C2H5)3 (TEB) and trimethylboron B(CH3)3 (TMB) are evaluated as precursors for CVD of BxC films. In order to get a complete understanding of the CVD behaviour of these precursors for deposition of boron containing films, both thermal CVD and plasma CVD of BxC films have been demonstrated. A gas phase chemical mechanism at the corresponding thermal CVD conditions was proposed by quantum chemical calculations while chemical mechanism in the plasma was suggested based on plasma composition obtained from Optical emission spectroscopy (OES). The behaviours of TEB and TMB in thermal CVD are investigated by depositing BxC films in both H2 and Ar atmospheres, respectively. Films deposited using TEB within a temperature window of 600 – 1000 °C are X-ray amorphous with 2.5 ≤ x ≤ 4.5. The impurity level of H is less than 1 at. % above 600 °C. Calculations predict that the gas phase reactions are dominated by β-hydride eliminations of C2H4 to yield BH3. In addition, a complementary bimolecular reaction path based on H2 assisted C2H6 elimination to BH3 is also present at lower temperatures in the presence of hydrogen molecules. As for films deposited with TMB, dense, amorphous, boron rich (B/C = 1.5-3) films are obtained at 1000 °C in both H2 and Ar atmosphere. The quantum chemical calculations suggest that the TMB molecule is mainly decomposed by unimolecular α- elimination of CH4 complemented by H2 assisted elimination of CH4. Plasma CVD of BxC thin films has been studied using both TMB and TEB as single-source precursors in an Ar plasma at temperatures lower than that allowed by thermal CVD. The effect of plasma power, TMB/TEB and Ar gas flow on film composition and morphology are investigated. The highest B/C ratio of 1.9 is found for films deposited at highest plasma power (2400 W) and high TMB flow (7 sccm). The H content in the films stays almost constant at 15±5 at. %. The B-C bonding is dominant in the films while small amounts of C-C and B-O exist, likely due to formation of amorphous carbon and surface oxidation. Film density is determined as 2.16±0.01 g/cm3 and the internal compressive stresses are measured to be less than 400 MPa. OES shows that TMB is decomposed to mainly atomic H, C2, BH, and CH. A plasma chemical model for decomposition of the TMB is constructed using a combination of film and plasma composition. It is suggested that the decomposition of TMB starts with dehydrogenation of the methyl groups followed by breakage of the B-C bonds to form the CH radicals. This bond breaking is at least partly assisted by hydrogen in forming the BH radicals. When films are deposited using TEB flow of 5 and 7 sccm, the B/C ratio is found to be plasma power dependent while the carbon content is almost not affected. The highest B/C ratio of 1.7 is obtained at the highest power applied (2400 W) and attributed to better dissociation of TEB at higher plasma power. The H content in the films is within 14-20 at. %. The density of films is increased to 2.20 g/cm3 with increasing plasma power and attributed to a higher energetic surface bombardment during deposition. The oxygen content in the film is reduced to less than 1 at. % with increasing plasma power due to the densification of the films preventing surface oxidation upon air exposure. Plasma composition from OES shows that the TEB molecules are also dissociated mainly to BH, CH, C2 and H. A plasma chemical model where the first ethyl group is split off by β-hydrogen elimination to form C2H4, which is further dehydrogenated to C2H2 and forms C2 and CH is suggested. The BH species is assumed to be formed by the dehydrogenation of remaining ethyl groups and breakage of the remaining B-C bonds to form BH.
2
Choi, Y. J. « Very high frequency plasma enhanced chemical vapour depositions for thin film transistors ». Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597635.
Texte intégralRésumé :
Hydrogenated amorphous silicon (a-Si:H) is increasingly being used in applications that require large-area, thin-film semiconductor. It can be deposited easily, at low temperature and low cost, on inexpensive substrates of almost any size by chemical vapour deposition methods. One of these applications of a-Si:H is the fabrication of thin-film transistors (TFTs) that are most often used in liquid crystal displays (LCDs). Plasma enhanced chemical vapour deposition (PECVD) is also called glow discharge deposition because of its visible luminosity of the plasma glow region, which is mainly the result of the de-excitation of emitting molecular and atomic species contained in the plasma. The field can be direct current (DC), radio frequency (RF), very high frequency (VHF), and microwave frequency. Deposition of a-Si:H employing the VHF-PECVD technique (typical frequency range 20-110 MHz) has been reported to yield an increase in deposition rate by one order of magnitude with respect to the conventional used frequency of 13.56 MHz, without adversely affecting material quality. The various electrical and optical properties of the VHF films were investigated as a function of main factors involved in the a-Si:H, SiNx, and n+ µc-Si layers deposition processes. The effects of the total pressure, the gases flow ratio, and the influence of VHF power have been intensively investigated to gain device-quality materials. Finally, a number of fabrication techniques and electrical testing were employed in order to realise high-performance thin film transistors with the optimised materials.
3
CALDIROLA, STEFANO. « Characterization of a supersonic plasma source for nanostructured thin films deposition ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2015. http://hdl.handle.net/10281/94564.
Texte intégralRésumé :
The controlled growth of nanostructured thin films represents a challenging field of research which is related to many different applications of great scientific relevance. The properties of many materials can be greatly enhanced by optimizing the nanoscale assembly processes: by modelling the nanoparticles which create and assemble a film it is possible to achieve very promising results, although it requires a bottom-up approach capable of tailoring the properties with a high level of control or a complex set-up. Plasma-based synthesis processes have been widely developed and applied for an increasing number of technologies leading to important achievements and many industrial-scale applications, in particular in the field of nanoscience.
Plasma Assisted Supersonic Jet Deposition offers a novel approach for nanostructured thin films deposition by combining a reactive plasma with a supersonic jet. An argon-oxygen inductively coupled plasma offers a reactive environment where a metalorganic precursor (titanium isopropoxide for TiO2 depositions) is dissociated and oxidized. The gas is then left to expand from a small orifice into a lower pressure vacuum vessel forming a supersonic jet, where the TiO2 nanoparticles are accelerated onto a substrate by the gas carrier mixture. This deposition technique has proven useful for the deposition of nanostructured thin film having a desired morphology at competitive deposition rates. In order to achieve an effective improvement of the synthesis process, an accurate knowledge of the expanding plasma jet chemistry and physics is of fundamental importance.
In this PhD project a deep characterization of the supersonic plasma jet was performed using different diagnostics. The plasma discharge in the reactor was monitored by optical emission spectroscopy, Langmuir probes and the measurement of voltage and current across the antenna of the ICP source. The supersonic plasma jet was characterized using a quadrupole mass spectrometer to sample the gas from the jet at different positions along its axis of symmetry. The detection of neutral species, radicals, ion fluxes and their energy distribution functions led to an understanding of the expanding plasma properties, its composition and its influence on thin films deposition. In addition to this, based on experimental observations, a MATLAB code was developed to reproduce the ion energy distribution functions numerically from first principle calculations. During this project plasma assisted supersonic jet deposition was also operated for the deposition of nanostructured TiO2 samples whose chemical, physical and morphological properties were analysed by FTIR, profilometry, ellipsometry, AFM and SEM.
4
Kroely, Laurent. « Process and material challenges in the high rate deposition of microcrystalline silicon thin films and solar cells by Matrix Distributed Electron Cyclotron Resonance plasma ». Phd thesis, Ecole Polytechnique X, 2010. http://pastel.archives-ouvertes.fr/pastel-00550241.
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High deposition rates on large areas are industrial needs for mass production of microcrystalline silicon (μc-Si:H) solar cells. This doctoral work aims at exploring the usefulness of Matrix Distributed Electron Cyclotron Resonance (MDECR) plasmas to process the intrinsic layer of μc-Si:H p-i-n solar cells at high rates. With the high dissociation of silane achieved in MDECR plasmas, deposition rates as high as 6nm/s and 2.8nm/s have been demonstrated in our lab for amorphous and microcrystalline silicon respectively, without hydrogen dilution. This technique is also promising because it can be easily scaled up on large areas, just by extending the matrix of elementary microwave applicators. This subject was a unique opportunity to cover the whole chain of this field of research : A new MDECR reactor has been specially designed and assembled during this project. Its maintenance and its improvement have been important technical challenges : for example, the addition of a load-lock enabled us to lower the oxygen concentration in our films by a factor of 10. The impact of the deposition parameters (e.g. the ion energy, the substrate temperature, different gas mixtures, the microwave power) has been explored in extensive parametric studies in order to optimize the material quality. Great efforts have been invested in the characterization of the films. Our strategy has been to develop a wide range of diagnostics (ellipsometry, Raman spectroscopy, SIMS, FTIR, XRD, electrical characterizations etc.). Finally, p-i-n cells have been processed with the selected interesting materials. The successive successful improvements in the material quality (e.g. diffusion lengths of holes parallel to the substrate as high as 250 nm) did unfortunately not result in high efficiency solar cells. Their limited performance is in particular due to a very poor response in the red part of the spectrum resulting in low current densities. Consequently, the potential sources of limitation of the reactor, the material and the device have been studied : e.g. the presence of “cracks” prone to post-oxidation in the highly crystallized materials and the risk of deterioration of the ZnO substrate or of the p-doped layer by a too high process temperature or by hydrogen diffusing from the plasma.
5
Xiao, Zhigang. « Synthesis of Functional Multilayer Coatings by Plasma Enhanced Chemical Vapor Deposition ». Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1081456822.
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6
Lau, Kenneth Ka Shun 1972. « Chemical vapor deposition of fluorocarbon films for low dielectric constant thin film applications ». Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/16748.
Texte intégralRésumé :
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2000.Includes bibliographical references.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Pulsed plasma enhanced and hot filament chemical vapor deposition have produced fluorocarbon films with the potential use as low dielectric constant interconnect materials in microelectronic circuits. Solid-state nuclear magnetic resonance spectroscopy was demonstrated as a valuable film characterization tool to understand structure-property processing fundamentals, quantifying film bonding environments and tracing structural instabilities. Thermal lability in fluorocarbon films was attributed to terminal end groups and low molecular weight molecules. High temperature thermal stability was achieved by minimizing such labile sources through a clean deposition of high molecular weight chains of poly(tetrafluoroethylene). Poly(tetrafluoroethylene) film porosity was introduced and controlled through the competition between nucleation and growth of film. Porous poly(tetrafluoroethylene) films were further integrated into a bridge layer and air gap dielectric interconnect scheme. With fluorocarbon materials deposited through such chemical vapor deposition methods, dielectric constants ranging from 2.1 to below 1.5 were conceivably attainable, thus potentially satisfying dielectric interconnect requirements to beyond the 0.1 [mu]m technology node.
by Kenneth Ka Shun Lau.
Ph.D.
7
Kim, Gwang-Soo 1975. « Multiscale modeling of thin film deposition processes ». Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29277.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002.Includes bibliographical references.
Ionized physical vapor deposition (IPVD) and electrochemical deposition (ECD) are two major thin film deposition processes in the microelectronics industry. The ion fluxes with high kinetic energies in IPVD process involve complex surface interactions that affect overall topology of the microscale features. Copper ECD process involves complex surface reactions and transport phenomena that ranges over different length scales. In this work, predictive simulation tools for these two processes have been developed by investigating the surface reaction and the transport phenomena in IPVD and ECD processes. In the IPVD process, molecular dynamics (MD) techniques with embedded-atom potentials are used to study the surface reactions for atoms with high impinging energies (30 - 50 eV). The surface reaction rates are combined with ballistic transport and level set methods. The resulting tool demonstrates the effect of the kinetic energy driven surface diffusion on the feature profile evolution. For the ECD process of copper, detailed surface kinetic mechanisms are developed based on the competitive adsorption/desorption model in the presence of three representative additives, poly ethylene glycol (PEG) and bis-(sodium sulfoprophyl) (SPS) and chloride. The proposed kinetic mechanism is capable of describing the synergistic effect of different additives on the copper deposition. Statistically designed experiments were performed with the rotating disk electrode (RDE) apparatus. A hydrodynamic model was developed for RDE and is used to fit the kinetic parameters that are independent of the transport effect.
(cont.) A reactor scale model is developed based on the Galerkin finite element method. The model includes momentum transport, transient mass transport, potential distribution and detailed surface kinetic mechanisms. The experimental film thickness uniformity on the blank wafer with commercial electrochemical deposition cell is compared with the simulation result. The reactor scale model is used to investigate the various effects on the film thickness uniformity including terminal effects and mass transport effects. The analysis shows the qualitative difference between two effects and how they can be eliminated. Also, the reactor scale simulation tool is used to model the pulse plating process. Improved performance of the pulse plating over the constant current operation suggests that the relaxation period is the critical parameter that determines the film thickness uniformity. A computationally efficient feature scale model is developed. Mass transport, potential distribution and detailed surface reactions are included in the model ...
by Gwang-Soo Kim.
Ph.D.
8
Garza, Ezra. « Pulsed Laser Deposition of Thin Film Heterostructures ». ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/459.
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Thin films of Strontium Ruthenate have been grown on Strontium Titanate and Lanthanum Aluminate (100) substrates by pulsed laser deposition. X-ray diffraction results show that the films grown on the Strontium Titanate are amorphous and polycrystalline on the Lanthanum Aluminate. Resistances versus temperature measurements show that the films exhibit semiconducting characteristics. In addition to the growth of Strontium Ruthenate thin films, multilayer heterostructures of Terfenol-D thin films on polycrystalline Lead Titanate thin films were grown by pulsed laser deposition. By using a novel experimental technique called magnetic field assisted piezoelectric force microscopy it is possible to investigate the magnetoelectric coupling between the electrostrictive Lead Titanate and magnetostrictive Terfenol-D thin film. Upon examination of the produced thin films the phase and amplitude components of the piezoelectric signal experience changes in response to an applied in-plane magnetic field. These changes provide experimental evidence of a magnetoelectric coupling between the Terfenol-D and Lead Titanate layers.
9
Rycroft, Ian M. « Electric, magnetic and optical properties of thin films, ultra thin films and multilayers ». Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318142.
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Chen, Yi. « Organic thin film transistors with mono-crystalline rubrene films by horizontal hot wall deposition ». Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66699.
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As promising candidates for future low-cost and flexible display applications, organic thin film transistors (OTFTs) have attracted considerable research interests for the past two decades. Recent advances in organic semiconductor theory and organic film growth/deposition techniques have resulted in OTFTs based on single crystalline organic films with performance approaching or even exceeding the present day's dominant amorphous silicon TFT technology. In this work, efforts have been made to explore suitable methods for the fabrication of thin film transistors based on high mobility organic semiconductors, such as rubrene and pentacene. In the early stage of this work, OTFTs with rubrene single crystals grown by PVT (Physical Vapor Transport) method were fabricated and measured with u-max,eff = 1.07 cm^2/V-s, ION/IOFF ~ 10^5 and VT = 0 V. However, it was noticed that these rubrene films are usually fragile and the adhesion to the substrates is often poor, leading to low reproducibility of functional devices. Hence, direct deposition of organic thin films to the substrates is a necessary measure to solve these problems. In this work, a horizontal hot wall deposition (HHWD) method has been developed to directly deposit high quality rubrene films onto the substrate under low pressure (P ~ 10^-6 torr). The resulted films were continuous with good coverage, however different structural phases from amorphous to near mono-crystalline were present. Through intensive studies on the film morphology and crystallinity of rubrene films deposited under different conditions, it is concluded that various factors can greatly affect the organic thin film growth, including surface treatment conditions, substrate orientations, source evaporation temperatures as well as substrate temperatures. Under the optimal deposition conditions, rubrene films are mono-crystalline with planar structure and grain sizes as large as 0.1 x 2En raison de leur potentiel de pouvoir contribuer à la diminution des coûts dans la fabrication des écrans plats flexibles, les transistors à couche mince organiques (OTFTs) ont attiré énormément d'intérêts dans les dernières décennies.Les avances récentes dans les théories sur les semiconducteurs organiques ainsi que celles sur les techniques de déposition et de croissance ont résulté au développement des OTFTs basés sur des couches organiques monocrystallines avec des performances approchant et même excédant celles dérivées des techniques de fabrication de TFTs de silicium amorphe qui sont couramment dominantes en industrie. Dans cette étude, des efforts ont étés mis pour explorer des méthodes convenables à la fabrication des transistors couches minces basés sur des semiconducteurs organiques à mobilité élevée comme le rubrène et le pentacène.Dans les premières étapes de cette étude, des OTFTs avec du rubrène monocrystalline dont la croissance a été atteinte par la méthode PVT ont été fabriqués et mesurés avec une max,eff = 1.07 cm^2/V-s, un ION/IOFF ~ 10^5 et un VT = 0 V. Il est à noter que ces couches de rubrène sont typiquement fragiles et l'adhésion aux substrats était souvent faible ce qui résultait en une reproductibilité réduite de dispositifs opérationnels. C'est alors que la déposition directe des couches minces organiques aux substrats devient une mesure nécessaire pour résoudre ces problèmes. Dans cette étude, une méthode de déposition à paroi chaude horizontale (HHWD) a été développée pour la déposition directe sous basse pression (P ~ 10^-6 torr)des couches de rubrène à haute qualité sur des substrats. Les couches résultantes sont continues avec une bonne couverture, tandis que des différentes phases structurelles amorphes et monocrystallines sont présentes. Par des études intensives sur la morphologie des couches et$
11
Charyshkin, Eugene V. « New methods of diamond and diamondlike films deposition ». Thesis, Queensland University of Technology, 1996.
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12
Gledhill, Sophie E. « Spray deposition of thin semiconductor films for use as buffer layers in CuInSâ†2 thin film solar cells ». Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393550.
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Lojewski, Brandon. « A Linear Multiplexed Electrospray Thin Film Deposition System ». Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5981.
Texte intégralRésumé :
Liquid spray is essential to industries requiring processes such as spray coating, spray drying, spray pyrolysis, or spray cooling. This thesis reports the design, fabrication, and characterization of a thin film deposition system which utilizes a linear multiplexed electrospray (LINES) atomizer. First, a thorough review of the advantages and limitations of prior multiplexed electrospray systems leads to discussion of the design rationale for this work. Next, the line of charge model was extended to prescribe the operating conditions for the experiments and to estimate the spray profile. The spray profile was then simulated using a Lagrangian model and solved using a desktop supercomputer based on Graphics Processing Units (GPUs). The simulation was extended to estimate the droplet number density flux during deposition. Pure ethanol was electrosprayed in the cone-jet mode from a 51-nozzle aluminum LINES atomizer with less than 3% relative standard deviation in the D10 average droplet diameter as characterized using Phase Doppler Interferometry (PDI). Finally a 25-nozzle LINES was integrated into a thin film deposition system with a heated, motion controlled stage, to deposit TiO2 thin films onto silicon wafers from an ethanol based nanoparticle suspension. The resulting deposition pattern was analyzed using SEM, optical profilometry, and macro photography and compared with the numerical simulation results. The LINES tool developed here is a step forward to enabling the power of electrospray for industrial manufacturing applications in clean energy, health care, and electronics.M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Miniature Engineering Systems
14
Wu, Genfa. « Energetic Deposition of Niobium Thin Film in Vacuum ». Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/28110.
Texte intégralRésumé :
Niobium thin films are expected to be free of solid inclusions commonly seen in solid niobium. For particle accelerators, niobium thin film has the potential to replace the solid niobium in the making of the accelerating structures. In order to understand and improve the superconducting performance of niobium thin films at cryogenic temperature, an energetic vacuum deposition system has been developed to study deposition energy effects on the properties of niobium thin films on various substrates. The system directly uses microwave power to create a pure niobium plasma, which can be used to extract niobium ion flux with controllable kinetic energy for direct deposition. The ultra high vacuum avoids the gaseous inclusions in thin films. A retarding field energy analyzer is developed and used to measure the kinetic energy of niobium at the substrate location. A systematic process for thin film characterization is developed and used to analyze the niobium thin films made by this energetic condensation. The properties of niobium thin films at several deposition energies are obtained, and the results show that there exists a preferred deposition energy around 115eV.Ph. D.
15
Haque, Yasmeen. « Deposition of plasma polymerized thin films / ». Thesis, Connect to this title online ; UW restricted, 1985. http://hdl.handle.net/1773/9848.
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Gustavsson, Lars-Erik. « Hollow Cathode Deposition of Thin Films ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6925.
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Al-Busaidy, Mohamed Said Kahalifa. « Energetic deposition of thin metal films ». Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/36128.
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The primary aim of this thesis was to study the physical effect of energetic deposition on metal thin films. The secondary aim is to enhance the quality of the films produced to a desired quality. Grazing incidence X-ray reflectivity (GIXR) measurements from a high-energy synchrotron radiation source were carried out to study and characterise the samples. Optical Profilers Interferometry, Atomic Force Microscope (AFM), Auger electron spectroscopy (AES), Medium energy ion spectroscopy (MEIS), and the Electron microscope studies were the other main structural characterisation tools used.
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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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Rieth, Loren Wellington. « Sputter deposition of ZnO thin films ». [Gainesville, Fla.] : University of Florida, 2001. http://purl.fcla.edu/fcla/etd/UFE0000349.
Texte intégralRésumé :
Thesis (Ph. D.)--University of Florida, 2001.Title from title page of source document. Document formatted into pages; contains xv, 262 p.; also contains graphics. Includes vita. Includes bibliographical references.
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Kaufmann, Christian A. « Chemical bath deposition of thin semiconductor films for use as buffer layers in CuInSâ†2 thin film solar cells ». Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393556.
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Okazaki, Nobuharu. « Molecular rectification with identical metal electrodes at low temperatures ». Thesis, University of Exeter, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251190.
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Ramezani-Namin, Mehrdad. « Optimization of glow discharge magnetron sputtering for deposition of high Tc superconducting thin films ». Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243149.
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Omar, Ozma. « Optical effects in Langmuir-Blodgett films of novel organic materials ». Thesis, Sheffield Hallam University, 1998. http://shura.shu.ac.uk/20143/.
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The high level of molecular control makes the Langmuir-Blodgett (LB) technique an appealing method of film deposition. The uniform nature of the films produced allows convenient investigation of intermolecular interactions and provides information pertaining to the orientation of molecules within films. LB films of two amphiphilic materials with contrasting molecular structures have been deposited. AmPc5 (a metal-free phthalocyanine (pc)) is a two-dimensional, cyclic molecule, whereas AmAzl (a resorcinol calixarene) possesses a three-dimensional basket-type structure. The amphiphilic nature of both molecules is as a result of functional side-chains. The AmPc5 spreading solution was prepared by dissolving in trichloroethane to a concentration of 0.1 mg/ml. After spreading 500-600 ul, the resulting Langmuir film was found to have a critical pressure of 28 mN/m and an area per molecule of 1.61 nm2 on the water surface. Monolayer deposition onto glass substrates enabled spectroscopic examination of the films and comparison to solution spectra. The solution spectrum shows the split Q-band absorption peaks at 700 nm and 733 nm characteristic of metal-free pc's. The LB film spectrum shows a broadening of both peaks and a red shift of the 733 nm peak, and a blue shift of the 700 nm peak. The 700 nm peak is suppressed as a result of the stack-like packing structure of AmPc5. Absorption spectra of floating AmPc5 monolayers imply that the material does not assume the monomer state at any stage of compression. This is characteristic of rigid molecules that induce order within the floating monolayer. The refractive indices (n) and extinction coefficients (k) were determined across the visible wavelength range. Both the n and k values are shown to increase with monolayer thickness, although the n value tends towards a steady value of 2.1. Deposition onto gold coated glass substrates enabled surface plasmon resonance analysis and determination of n and k at specific film thickness'. The n was found to increase with film thickness, tending towards a steady state value of 2.0. This is in excellent agreement with spectroscopic analysis. Absorption spectra measured using polarised light show AmPc5 exhibits dichroism. The calculations indicate that the pc ring lies almost perpendicular to the substrate. AmAzl was dissolved in chloroform to a concentration of 0.5 mg/ml with 10% ethanol to aid solubility. The optimum solution spreading quantity required to form a floating monolayer was found to be between 50 and 100 ul. The film was shown to have a critical pressure of 30 mN/m and an area per molecule of 1.86 nm2 on the water surface. Both LB film and solution spectra show a single absorbance peak at 454 nm which is due to transitions in the azo functional side chains. Calculation of n and k shows that they tend towards steady values of 1.5 and 2.0, respectively. The n obtained via surface plasmon resonance analysis shows a steady state value of 1.43 on silver coated glass and 1.35 on gold coated glass. This suggests a different type of packing structure on all three substrates. The lack of dichroism exhibited by AmAzl indicates the formation of in-plane amorphous films. AmAzl was deposited in alternating layers with tricosenoic acid. The structure was confirmed by X-ray diffraction studies and investigated using second harmonic generation. The second harmonic signal was shown to be proportional to the square of the number of bilayers.
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Klosterman, Luke J. « Deposition, Oxidation, and Adhesion Mechanisms of Conformal Polydopamine Films ». Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/702.
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The oxidation of dopamine in aqueous solutions deposits thin conformal films on a wide variety of material surfaces. These films consist of a material known as polydopamine (PDA), and they exhibit chemical and structural similarities to melanin pigments and adhesive proteins secreted by mussels. The facile synthesis and versatile adhesion of PDA enable the functional modification of numerous material surfaces for applications in biomedical devices, energy storage, and water purification. This thesis details fundamental investigations into the deposition, oxidation, and adhesive mechanisms of PDA films. Depositing PDA films on substrates with different controlled chemistries revealed the importance of solution pH and initial deposition rates on the morphology of the films. The deposition of PDA molecules with increasing pH depends on two competing factors: increased generation rate of PDA molecules versus increased solubility due to catechol ionization. The areal density and coverage of three-dimensional PDA islands is influenced by the surface charge and hydrophobicity of the substrate in aqueous solutions. Spectroscopic and electrochemical characterization of PDA films revealed that redox-inactive metal cations can accelerate the oxidation of PDA. The generation of radicals of 5,6-dihydroxyindole were monitored in situ via ultraviolet-visible spectroscopy as a function of cation concentration and pH. The extent of oxidation was quantified by cyclic voltammetry. The resulting oxidation modifies the metal sorption properties of PDA by generating more carboxylic acid groups and enhancing the iron chelation of the films. The adhesive stability of PDA films was characterized by delamination kinetics of films on SiO2 and indium tin oxide (ITO). PDA film adhesion is a substrate, salt, and oxidation-dependent phenomenon. Long-term adhesive stability of PDA films can be promoted by use of higher dopamine concentrations during synthesis, incorporation of multivalent cations, and avoiding alkaline conditions and strongly oxidizing electrical bias. Elastic moduli of PDA films were quantified by compressive thin film wrinkling, and the measured value of 2.0 ± 0.9 GPA agrees with simulations of PDA based on an oligomeric aggregate model. This thesis helps develop a framework for understanding the synthesis, composition, microstructure, and stability of PDA films.
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Hu, Xiaobing. « Deposition and characterisation of bismuth layer-structured ferroelectric films ». Thesis, University of Cambridge, 2006. https://www.repository.cam.ac.uk/handle/1810/194739.
Texte intégralRésumé :
Bismuth layer-structured ferroelectrics have been recognised as promising film materials for ferroelectric random access memory application due to their excellent fatigue resistance and other electrical properties. This work deals with the deposition and characterisation of epitaxial and polycrystalline W-doped SrBi2Ta2O9 (SBT) and lanthanide-doped bismuth titanate (BiT) films. SBT and W-doped SBT films were fabricated by pulsed laser deposition (PLD) on platinised silicon substrates. The effects of fabrication temperature and W-doping level on film properties were studied. The crystallinity of SBTW films improved with increasing fabrication temperatures, resulting in enhanced ferroelectric properties and dielectric properties above the fabrication temperature of 750 °C. Dense ceramic samples of Nd- and Sm-doped BiT (BNdT and BSmT) were successfully fabricated for PLD targets by solid state processing. Highly epitaxially (001)-, (118)-, and(104)-oriented Nd-doped bismuth titanate (BNdT) films were grown by PLD on (001)-, (011)-,and (111)-oriented SrTiO3 (STO) single crystal substrates, respectively. A three-dimensional orientation relationship between films and substrates was derived as: BNdT(001)//STO(001),BNdT[ 110 ]//STO[100]. Films showed strong dependence of structural and ferroelectric properties on the crystal orientation. PLD-grown BSmT films on platinised silicon substrates were studied as a function of fabrication temperature, effects of Pt bottom layer orientation, Sm doping level, and LaNiO3 buffer layer. An alkoxide-salt chemical solution deposition (CSD) method was adopted to prepare the precursors for BSmT (BNdT) film fabrication. Precursors of Bi-Sm(Nd)-Ti which were stable for at least eight months in air ambient were successfully developed. In-situ FT-IR studies suggest that acetic acid serves as chelating agent to improve the homogeneity of the precursor solution by generating a dense and homogeneous Ti-O-Ti polymeric network. The electrical properties of the films fabricated in this study (dielectric and ferroelectric properties, leakage current characteristics and electrical fatigue properties), are comparable or superior to these previously reported for similar films developed by other techniques or with other doping elements. Low temperature electrical properties of BSmT films suggest that the films are very promising for extremely low temperature nonvolatile memory applications. The results of BNdT films annealed at different oxygen partial pressure (O2, air, N2) showed that oxygen ambience affected structural properties of the films by enhancing the growth of perovskite phase (phase formation), increasing grain size (grain growth), and assisting the growth of (117)-oriented grains (crystallographic orientations). Piezoresponse force microscopy (PFM) was adopted to characterise BSmT films. Domain structures were clearly observed in a PLD-grown BSmT film, which were closely related to the grain structures. Domain manipulation was carried out in a CSD-derived BSmT film, showing that the film can be nearly uniformly polarised, which can be used in nanoscale device fabrication. Clear hysteresis loops were measured by PFM, which was an important proof of ferroelectricity. Large spatial variations of piezoelectric hysteresis loops of a CSD-derived BSmT film were observed across the film surface. Effective electrostriction coefficient (Qeff) of a PLD-grown BSmT film was measured, showing that BSmT films had better piezoelectric properties (higher Qeff, higher dzz) than SBT films, un-doped BiT ceramics and films. It suggests that BSmT films are promising piezoelectric materials for MEMS use.
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Gregory, Robert p. « Digital control of a MBE deposition system ». Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237668.
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Ravindran, Ramasamy. « Deposition and characterization of high permittivity thin-film dielectrics ». Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4530.
Texte intégralRésumé :
Thesis (M.S.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2009) Includes bibliographical references.
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Kaye, Simon Peter. « Ion-assisted deposition of molybdenum disulphide films ». Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238835.
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Zou, Shubing. « Deposition and characterization of HfO₂ thin films ». Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07112009-040501/.
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Halindintwali, Sylvain. « A study of hydrogenated nanocrystalline silicon thin films deposited by hot-wire chemical vapour deposition (HWCVD) ». Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
Texte intégralRésumé :
In this thesis, intrinsic hydrogenated nanocrystalline silicon thin films for solar cells application have been deposited by means of the hot &ndashwire chemical vapour deposition (HWCVD) technique and have been characterised for their performance. It is noticed that
hydrogenated nanocrystalline silicon is similar in some aspects (mainly optical) to its counterpart amorphous silicon actually used as the intrinsic layer in the photovoltaic industry. Substantial differences between the two materials have been found however in their respective structural and electronic properties.
We show that hydrogenated nanocrystalline silicon retains good absorption coefficients known for amorphous silicon in the visible region. The order improvement and a reduced content of the bonded hydrogen in the films are linked to their good stability. We argue that provided a moderate hydrogen dilution ratio in the monosilane gas and efficient process pressure in the deposition chamber, intrinsic hydrogenated nanocrystalline silicon with photosensitivity better than 102 and most importantly resistant to the Staebler Wronski effect (SWE) can be produced.
This work explores the optical, structural and electronic properties of this promising material whose study &ndash
samples have been exclusively produced in the HWCVD reactors based in the Solar Cells laboratory of the Physics department at the University of the Western Cape.
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Piskin, Fatih. « Deposition And Testing Of Thin Film Hydrogen Separation Membranes ». Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615550/index.pdf.
Texte intégralRésumé :
Industrial production of hydrogen from the syngas, generated from steam reformation of natural gas or coal gasification, sets conditions for hydrogen separation membranes in terms of operating conditions. An alternative source for hydrogen is a syngas generated by gasification of municipal solid wastes which are likely to set more stringent conditions for the separation membranes. There is therefore, a growing demand for separation membranes with improved permeability and particularly of low cost. Among various alternatives, metallic membranes are particularly attractive due to their high selectivity and permeability for hydrogen, exemplified by palladium (Pd). However, due to high cost of Pd there is still a demand to develop alternative metallic membranes that are of low cost and have improved durability. Efforts have therefore concentrated on either alloying Pd so as to reduce its cost or on alternative membrane compositions of particularly b.c.c. structure.
The current study deals with hydrogen separation membranes and aims to develop infrastructure for rapid identification of membrane compositions with improved permeability. The study is made up of three partsi) development of sputter deposition system that would allow deposition of multiple compositions in a single experiment, ii) development of substrate material that would support the thin film membranes and would allow permeability measurement and iii) development of a set-up to measure the permeability of the thin film membranes. In the present thesis, a sputter deposition system incorporating three targets was successfully constructed. The system as tested with palladium-niobium-titanium (Pd-Nb-Ti) ternary system after necessary adjustment would yield thin films of homogenous thickness (&le
7%) over a sample area of &asymp
150 mm diameter. A total of 21 substrates each in 19 mm diameter arranged in triangular form in the substrate holder could successfully be deposited where composition distributions covered a greater portion of Pd-Nb-Ti ternary phase diagram. The structure of the deposited thin films can successfully be controlled by substrate temperature as well as by the pressure of plasma gas (argon). With the help of these parameters, structural diversity can also be produced beside the compositional variation. As for substrates, two materials were investigated. These were titanium dioxide (TiO2) modified porous stainless steel (PSS) and anodic porous alumina (AAO). TiO2 modified PSS due to its associated surface roughness leads to the deposition of films with defected structure which as a result is not gas tight. AAO produced via anodization of aluminum foil had a regular (40-60 nm) pore structure that provides a suitable surface for thin film depositions which could be defect free. However, AAO is very delicate and fragile which makes it difficult to adapt it as a support material for permeability measurement/hydrogen separation purposes. Finally, a set-up was developed for measurement of hydrogen permeability which is capable of measurement over a wide pressure and temperature conditions, i.e. hydrogen pressures up to 10 bar and temperature as high as 450 °
C. It is recommended that so as to identify compositions with improved permeability, Nb or a similar metal which has extremely high permeability could be used as a support material. This would tolerate the evaluation of the films which are not totally defect free.
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Horley, Graeme Anthony. « Novel gallium and indium precursors for thin film deposition ». Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322883.
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Huq, Syed Ejazul. « Thin film deposition by the ionized cluster beam method ». Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304288.
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Schreiber, Simon Johannes. « Plasma deposition of microcrystalline silicon for thin film transistors ». Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621413.
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Plassmeyer, Paul. « Metal-Oxide Thin Films Deposited from Aqueous Solutions : The Role of Cation/Water Interactions ». Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22295.
Texte intégralRésumé :
Metal-oxide thin films are used in a wide variety of electronic devices. Although many techniques have been developed to deposit thin films of metal oxides, there is still a need for alternative cost- and energy-effective deposition methods. Deposition of metal oxide thin films from aqueous solutions of all-inorganic metal salts is a viable method that meets these needs. Although many aqueous-deposited metal-oxide thin films have been successfully incorporated into functioning devices, many of the mechanisms that occur as precursors transition to metal oxides are not well understood.
The work presented in this dissertation is primarily concerned with examining the processes that occur as metal oxide thin films form from spin-deposited aqueous precursor solutions with a particular focus on the role of H2O in these processes. Chapter I summarizes methods for thin film deposition, and describes the use of aqueous metal salt solutions as viable precursors for the deposition of metal oxide thin films. Chapter II investigates the precursor chemistry, film-formation processes and properties of LaAlO3 thin films deposited from aqueous precursors. This chapter also serves as general guide to the processes that occur as metal-oxide thin films form from spin-deposited aqueous precursors. Chapters III and IV focus on the effects of H2O(g) during spin-deposition of precursor thin films and during the annealing process in which precursors are converted to metal oxides, respectively. The presence of H2O(g) during spin-deposition has a striking effect on the thickness of the resulting thin films and also affects the elemental gradient and density profiles. During annealing, H2O(g) reduces the temperatures at which counterions are expelled and influences the metal-hydroxide framework formation and its condensation to a metal oxide. The data also indicate that H2O(g) enhances diffusion of gaseous byproducts from within the films. Chapter V focuses on precursor concentration and its impact on the thermal evolution of thin films. The processes involved in the conversion of precursors to metal oxide thin films occur at lower temperatures as precursor concentration decreases. Although this is likely in part due to thickness effects, concentration-dependent precursor speciation may also be involved in lowering the temperatures at which films densify.2019-02-17
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Akyildiz, Hasan. « Hydrogen Storage In Magnesium Based Thin Film ». Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612652/index.pdf.
Texte intégralRésumé :
ABSTRACT
HYDROGEN STORAGE IN MAGNESIUM BASED
THIN FILMS
Akyildiz, Hasan
Ph.D., Department of Metallurgical and Materials Engineering
Supervisor : Prof. Dr. Tayfur Öztü
rk Co-Supervisor : Prof. Dr. Macit Ö
zenbas October 2010, 146 pages A study was carried out for the production of Mg-based thin films which can absorb and desorb hydrogen near ambient conditions, with fast kinetics. For this purpose, two deposition units were constructed
one high vacuum (HV) and the other ultra high vacuum (UHV) deposition system. The HV system was based on a pyrex bell jar and had two independent evaporation sources. The unit was used to deposit films of Mg, Mg capped with Pd and Au-Pd as well as Mg-Cu both in co-deposited and multilayered form within a thickness range of 0.4 to 1.5 &mu
m. The films were crystalline with columnar grains having some degree of preferred orientation. In terms of hydrogen storage properties, Mg/Pd system yielded the most favorable results. These films could desorb hydrogen at temperatures not greater than 473 K. The study on crystalline thin films has further shown that there is a narrow temperature window for useful hydrogenation of thin films, the upper limit of which is determined by the intermetallic formation. The UHV deposition system had four independent evaporation sources and incorporated substrate cooling by circulating cooled nitrogen gas through the substrate holder. Thin films of Mg-Cu were produced in this unit via co-evaporation technique to provide concentrations of 5, 10 and 15 at. % Cu. The films were 250-300 nm thick, capped with a thin layer of Pd, i.e. 5-25 nm. The deposition was yielded nanocrystalline or amorphous Mg-Cu thin films depending on the substrate temperature. At 298 K, the films were crystalline, the structure being refined with the increase in Cu content. At 223 K, the films were amorphous, except for Mg:Cu=95:5. The hydrogen sorption of the films was followed by resistance measurements, with the samples heated isochronally, initially under hydrogen and then under vacuum. The resistance data have shown that hydrogen sorption behaviour of thin films was improved by size refinement, and further by amorphization. Among the films deposited, amorphous Mg:Cu=85:15 alloy could absorb hydrogen at room temperature and could desorb it at 223 K (50 º
C), with fast kinetics.
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Lindahl, Erik. « Thin Film Synthesis of Nickel Containing Compounds ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-111484.
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Johnson, Shevon. « Pulsed Laser Deposition of Hydroxyapatite Thin Films ». Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6839.
Texte intégralRésumé :
Pulsed laser deposition (PLD) was used to deposit hydroxyapatite (HA) thin films on various substrates, including silicon (100) and titanium (Ti-6Al-4V) alloy. Thin films of amorphous HA were deposited at room temperature and then annealed over a range of temperatures. The microstructure and composition of the films were determined using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and X-ray diffraction (XRD). The HA films were found to achieve total crystallinity at 350㮠The mechanical properties of the films were studied by means of nanoindentation and scratch adhesion testing. Crystalline and adherent HA thin films prepared using PLD and post deposition annealing have many potential medical and dental applications.
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Liljeholm, Lina. « Reactive Sputter Deposition of Functional Thin Films ». Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-175666.
Texte intégralRésumé :
Thin film technology is of great significance for a variety of products, such as electronics, anti-reflective or hard coatings, sensors, solar cells, etc. This thesis concerns the synthesis of thin functional films, reactive magnetron sputter deposition process as such and the physical and functional characterization of the thin films synthesized. Characteristic for reactive sputtering processes is the hysteresis due to the target poisoning. One particular finding in this work is the elimination of the hysteresis by means of a mixed nitrogen/oxygen processing environment for dual sputtering of Alumina-Zirconia thin films. For a constant moderate flow of nitrogen, the hysteresis could be eliminated without significant incorporation of nitrogen in the films. It is concluded that optimum processing conditions for films of a desired composition can readily be estimated by modeling. The work on reactively sputtered SiO2–TiO2 thin films provides guidelines as to the choice of process parameters in view of the application in mind, by demonstrating that it is possible to tune the refractive index by using single composite Six/TiO2 targets with the right composition and operating in a suitable oxygen flow range. The influence of the target composition on the sputter yield is studied for reactively sputtered titanium oxide films. It is shown that by using sub-stoichiometric targets with the right composition and operating in the proper oxygen flow range, it is possible to increase the sputter rate and still obtain stoichiometric coatings. Wurtzite aluminum nitride (w-AlN) thin films are of great interest for electro-acoustic applications and their properties have in recent years been extensively studied. One way to tailor material properties is to vary the composition by adding other elements. Within this thesis (Al,B)N films of the wurtzite structure and a strong c-axis texture have been grown by reactive sputter deposition. Nanoindentation experiments show that the films have nanoindentation hardness in excess of 30 GPa, which is as hard as commercially available hard coatings such as TiN. Electrical properties of w-(Al,B)N thin films were investigated. W-(Al,B)N thin films are found to have a dielectric strength of ~3×106 V/cm, a relatively high k-value around 12 and conduction mechanisms similar to those of AlN. These results serve as basis for further research and applications of w-(Al,B)N thin films. An AlN thin film bulk acoustic resonator (FBAR) and a solidly mounted resonator (SMR) together with a microfluidic transport system have been fabricated. The fabrication process is IC compatible and uses reactive sputtering to deposit piezoelectric AlN thin films with a non-zero mean inclination of the c-axis, which allows in-liquid operation through the excitation of the shear mode. The results on IC-compatibility, Q-values, operation frequency and resolution illustrate the potential of this technology for highly sensitive low-cost micro-biosensor systems for applications in, e.g. point-of-care testing.
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Oberste, Berghaus Jörg. « Induction plasma deposition of diamond thin films ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ44100.pdf.
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Martin, Tyler Philip. « Platinumisilica Thin Films by Chemical Vapor Deposition ». Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/MartinTP2002.pdf.
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Oberste, Berghaus Jürg. « Induction plasma deposition of diamond thin films ». Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20153.
Texte intégralRésumé :
Diamonds unrivaled properties generate an enormous potential in industrial applications for thin film diamond coatings. Diamond has the highest values of hardness, thermal conductivity and elastic modules of any known material. Polycrystalline diamond coatings can be produced from thermal plasmas by Chemical Vapor Deposition (CVD). The films created by this process are often very non uniform over the deposition area. The properties of the free flowing plasma above the deposition surface and the plasma chemistry in the boundary layer above the growing film are believed to play fundamental roles in the formation of the diamond film and its uniformity.In this study, an Ar/H2/CH4 plasma (8.65% H 2, 0.25% CH4) was created by a rf inductively coupled plasma torch for the deposition of diamond thin films on a molybdenum substrate probe (5 mm diam.). With the probe surface oriented normal to the plasma flow, growth rates in the order of 70 gm/hr were obtained for highly crystalline continuous films. Temperature and electron density profiles in the plasma free flow were determined from measurements by emission spectroscopy. (Abstract shortened by UMI.)
43
Sweeney, Timothy. « The electrophoretic deposition of ferroelectric thin films ». Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389804.
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Owens, Jessica Margaret. « The sputter deposition of oxide thin films ». Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627173.
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Li, Chen-Chung. « Ion assisted deposition of multicomponent thin films ». Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40039.
Texte intégralRésumé :
A novel in-situ stress measurement technique to study the formation kinetics of multi component oxide thin films was developed and was applied to PbTiO₃. Single phase PbTi 0₃ thin films were formed from the reaction between films in the deposited PbO ITi0₂ multilayer. The film stoichiometry was accurately controlled by depositing individual layers of the required thickness. Development of film stresses associated with the formation of the product layer at the PbO/Ti0₂ interface of the multilayers was used to monitor growth rate of the PbTiO₃ layer. It was found that growth of the PbTiO₃ phase obeyed the parabolic law and the effective activation energy was estimated to be 108 kJ/mole. It is believed that the mechanism of this reaction was dominated by grain boundary diffusion of the participating cations.Ph. D.
46
Britson, Jason Curtis. « Pulsed laser deposition of AlMgB₁₄ thin films ». [Ames, Iowa : Iowa State University], 2008.
Trouver le texte intégral
47
Huang, Ying-Hao, et 黃英豪. « A study of various depositions of absorption layers in CIGS thin film solar cells ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/22298356181624336824.
Texte intégralRésumé :
碩士聖約翰科技大學
機械與電腦輔助工程系碩士班
103
CIGS thin films have become one of the most important absorption layer in solar cells because of its high efficiency. This work characterizes flexible CIGS solar cells synthesized with various deposition methods. The Mo conducting films is sputtered on stainless steel shells, and utilizes sandwich deposition method (In/CuGa/In) to sputter CIG precursor films on the Mo/stainless steel substrates. Then, the CIGS absorption layers are synthesized with three stage high temperature selenization. The surface roughness, micro structure, composition, crystallization, and conductivity of the CIGS are characterized by the 3D profiler, scanning electronic microscope, energy dispersive spectrometer, X-ray diffraction machine, and Hall effects meter. To finish the solar cell, the ZnS buffer layer and AZO transparently conductive layer are deposited on the CIGS film with E-beam evaporation, sputtering, and atomic layer deposition. The result shows that the specimen of In 600 nm/ CuGa 300 nm/ In 600 nm with Cu/(In+Ga) ratio 0.941 behaves the best photoelectric performance.
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« Ferroelectric Lithium Niobate Surfaces for Depositions of Metallic Nanostructure and ZnO Semiconducting Thin Film ». Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.9290.
Texte intégralRésumé :
abstract: A distinct characteristic of ferroelectric materials is the existence of a reversible spontaneous polarization with the application of an electric field. The relevant properties ferroelectric lithium niobate surfaces include a low density of defects and external screening of the bound polarization charge. These properties result in unique surface electric field distribution with a strong electric field in the vicinity of domain boundaries, while away from the boundaries, the field decreases rapidly. In this work, ferroelectric lithium niobate (LN) is used as a template to direct the assembly of metallic nanostructures via photo-induced reduction and a substrate for deposition of ZnO semiconducting thin films via plasma enhanced atomic layer deposition (PE-ALD). To understand the mechanism the photo-induced deposition process the following effects were considered: the illumination photon energy and intensity, the polarization screening mechanism of the lithium niobate template and the chemical concentration. Depending on the UV wavelength, variation of Ag deposition rate and boundary nanowire formation are observed and attributed to the unique surface electric field distribution of the polarity patterned template and the penetration depth of UV light. Oxygen implantation is employed to transition the surface from external screening to internal screening, which results in depressed boundary nanowire formation. The ratio of the photon flux and Ag ion flux to the surface determine the deposition pattern. Domain boundary deposition is enhanced with a high photon/Ag ion flux ratio while domain boundary deposition is depressed with a low photon/Ag ion flux ratio. These results also support the photo-induced deposition model where the process is limited by carrier generation, and the cation reduction occurs at the surface. These findings will provide a foundational understanding to employ ferroelectric templates for assembly and patterning of inorganic, organic, biological, and integrated structures. ZnO films deposited on positive and negative domain surfaces of LN demonstrate different I-V curve behavior at different temperatures. At room temperature, ZnO deposited on positive domains exhibits almost two orders of magnitude greater conductance than on negative domains. The conductance of ZnO on positive domains decreases with increasing temperature while the conductance of ZnO on negative domains increases with increasing temperature. The observations are interpreted in terms of the downward or upward band bending at the ZnO/LN interface which is induced by the ferroelectric polarization charge. Possible application of this effect in non-volatile memory devices is proposed for future work.Dissertation/Thesis
Ph.D. Physics 2011
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Luo, Yu-Siang, et 羅渝翔. « Investigation of the Electrochromic Properties of WO3 Thin Film Prepared by Containing Hydrogens by DC and Pulsed DC Sputtering Depositions ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/46834604955187338967.
Texte intégralRésumé :
碩士國立雲林科技大學
電子與光電工程研究所碩士班
101
The rapid development of electrochromic materials has draw much attention to the evaluation of the performance of its devices. To understand the dynamic performance is necessary for the sake of making a reliable electrochromic device in commercial purpose, which in term mostly is all-solid-state electrochromic devices. The key to the success of these products reflects strongly on various electrochromic performance of such a device. These include response time, memory effect, transmittance, optical density change and color-bleach cyclic lifetime. In this study, the tungsten oxide thin film with high coloration efficiency and durability was prepared by direct current (DC) and pulsed direct current (pulsed DC) sputtering system with different hydrogen conditions. The 0.1M LiClO4 solution was used as an electrolyte in the measurement of electrochemistry. As the results, the tungsten oxide film have better optical density change when the gas flow ratio Ar:O2 was 60:42 sccm and hydrogen was 4sccm、3sccm entering the direct current (DC) and pulsed direct current (pulsed DC) sputtering system. As the thickness of film increased, the optical density change was increased. The film was defeated by a higher applied voltage. In the Raman spectra, when adding hydrogen into pulsed DC, the peak area of W6+ becomes stronger, but there is flaw appeared in W5+ and W4+ compared with DC which is not existed flaw. To the AC impedance, when adding hydrogen with the optimized parameters, the resistance value of pulsed DC is higher than DC, so there is a better performance in DC sputtering than pulsed DC to tungsten oxide.
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Lu, Yi-Cheng, et 盧奕誠. « Pulsed Laser Deposition of MnZnO Thin Film on ZnO Films ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/6x3639.
Texte intégralRésumé :
碩士國立臺北科技大學
光電工程系研究所
98
MnxZn1-xO has become an attractive material because of it’s ferromagnetic and optoelectronic properties. Here we demonstrate that MnZnO thin film can be synthesized via pulsed laser deposition (PLD) method and investigate it’s structural and optoelectronic properties. The thesis consists of two parts. In the first part, the MnxZn1-xO (0.02≦x≦0.2) thin film was grown on c-plane sapphire substrate by PLD method directly. Measurements include scanning electron microscope (SEM), X-ray diffraction (XRD), optical transmission spectra, and atomic force microscopy (AFM). In the second part, in attempt to improve crystalline properties of MnZnO, the ZnO thin film was grown on c-plane sapphire substrate before the growth of MnZnO. The SEM images reveal the thin film structure become rougher when x increase. The XRD shows that only (0002) peak exists and the peak moves to lower angle( lattice constants become larger) . The room-temperature photoluminescence (RTPL spectrum) showed that ultraviolet luminescence peak has blueshift with the increasing Mn composition, and full width at half maximum (FWHM) of PL spectrum became wider. Besides, this thesis showed the bandgap of MnZnO can be controlled with Mn composition and the RTPL of MnZnO was observed.