Tesi sul tema "Metallic films"
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1
Sun, Tianyi. "Nano-optics of Perforated Metallic Films". Thesis, Boston College, 2014. http://hdl.handle.net/2345/bc-ir:103561.
Testo completoAbstract (sommario):
Thesis advisor: Krzysztof KempaThesis advisor: Zhifeng Ren
In the past few decades, accompanied by the fascinating development of micro- and nano-fabrication techniques, the successful integration of subwavelength optics and multilayer structures has led to a number of remarkable discoveries. In this work, I present both experimental and theoretical investigations of the optics of thin metallic films with micro-/nano-scale perforations in the UV-VIS-IR ranges. Different fabrication techniques are employed, including nanosphere lithography, grain boundary lithography, crack templates, and sintered nanoparticles. The optical properties these films are studied, revealing important relation between optical response and the film geometry. This includes the evolution of plasmonic resonances in a series of periodic arrays of holes in a metallic film, with hole sizes increasing gradually until an array of islands is achieved. This evolution is an analog of the percolation problem, and critical phenomena are observed at the percolation threshold. Multilayer broad-band electromagnetic absorbers are also designed and fabricated based on the study of these perforated films. Parallel with these observations, an analytical coherence model is proposed to bridge the subwavelength and superwavelength limits. Such a model also provides an alternative way to handle thin random structures, avoiding large quantity of numerical computation. These studies can find applications in the design of sensors, ultrathin solar cells and transparent electrodes, as well as in applications where random structures are widely used
Thesis (PhD) — Boston College, 2014
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
2
Yang, Fu-Liang. "Interdiffusion in metallic multilayers". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360566.
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3
Steinsiek, Christoph. "Molecular Beam Scattering from Ultrathin Metallic Films". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://hdl.handle.net/11858/00-1735-0000-0023-3EB8-2.
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4
Hoekstra, John. "The structural and mechanical properties of metallic multilayers /". Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/10582.
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5
Wu, Fan. "Microscopic and mesoscopic characteristics of granular metal films". Diss., Online access via UMI:, 2004.
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6
Boufelfel, Ahmed 1958. "STRUCTURAL CHARACTERIZATION OF SPUTTERED B.C.C.-B.C.C. METALLIC SUPERLATTICES". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276389.
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7
Rodekohr, Chad L. Bozack Michael J. Flowers George T. "Material factors influencing metallic whisker growth". Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/FALL/Mechanical_Engineering/Dissertation/Rodekohr_Chad_16.pdf.
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8
Xu, Wenjin. "Anomalous hall effect in ferromagnetic metallic thin films /". View abstract or full-text, 2010. http://library.ust.hk/cgi/db/thesis.pl?NSNT%202010%20XU.
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9
Warren, Andrew. "X-ray Scattering Investigations of Metallic Thin Films". Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5721.
Testo completoAbstract (sommario):
Nanometric thin films are used widely throughout various industries and for various applications. Metallic thin films, specifically, are relied upon extensively in the microelectronics industry, among others. For example, alloy thin films are being investigated for CMOS applications, tungsten films find uses as contacts and diffusion barriers, and copper is used often as interconnect material. Appropriate metrology methods must therefore be used to characterize the physical properties of these films. X-ray scattering experiments are well suited for the investigation of nano-scaled systems, and are the focus of this doctoral dissertation. Emphasis is placed on (1) phase identification of polycrystalline thin films, (2) the evaluation of the grain size and microstrain of metallic thin films by line profile analysis, and (3) the study of morphological evolution in solid/solid interfaces. To illustrate the continued relevance of x-ray diffraction for phase identification of simple binary alloy systems, Pt-Ru thin films, spanning the compositional range from pure Pt to pure Ru were investigated. In these experiments, a meta-stable extension of the HCP phase is observed in which the steepest change in the electronic work function coincides with a rapid change in the c/a ratio of the HCP phase. For grain size and microstrain analysis, established line profile methods are discussed in terms of Cu and W thin film analysis. Grain sizes obtained by x-ray diffraction are compared to transmission electron microscopy based analyses. Significant discrepancies between x-ray and electron microscopy are attributed to sub-grain misorientations arising from dislocation core spreading at the film/substrate interface. A novel "residual" full width half max parameter is introduced for examining the contribution of strain to x-ray peak broadening. The residual width is subsequently used to propose an empirical method of line profile analysis for thin films on substrates. X-ray reflectivity was used to study the evolution of interface roughness with annealing for a series of Cu thin films that were encapsulated in both SiO2 and Ta/SiO2. While all samples follow similar growth dynamics, notable differences in the roughness evolution with high temperature ex-situ annealing were observed. The annealing resulted in a smoothing of only one interface for the SiO2 encapsulated films, while neither interface of the Ta/SiO2 encapsulated films evolved significantly. The fact that only the upper Cu/SiO2 interface evolves is attributed to mechanical pinning of the lower interface to the rigid substrate. The lack of evolution of the Cu/Ta/SiO2 interface is consistent with the lower diffusivity expected of Cu in a Cu/Ta interface as compared to that in a Cu/SiO2 interface. The smoothing of the upper Cu/SiO2 interface qualitatively follows that expected for capillarity driven surface diffusion but with notable quantitative deviation.Ph.D.
Doctorate
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering
10
Peterson, Sarah M. "Influence of scale, geometry, and microstructure on the electrical properties of chemically deposited thin silver films /". Connect to title online (ProQuest), 2007. http://proquest.umi.com/pqdweb?did=1453183211&sid=2&Fmt=2&clientId=11238&RQT=309&VName=PQD.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Oregon, 2007.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 95-101). Also available online in ProQuest, free to University of Oregon users.
11
Genc, Arda. "Phase Stability in Metallic Multilayers". The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1204506282.
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Overman, Nicole Rebecca. "Yielding and fracture in nanolayered metallic composites". Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Summer2009/n_overman_061709.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in materials science and engineering)--Washington State University, August 2009.Title from PDF title page (viewed on Aug. 10, 2009). "School of Mechanical and Materials Engineering." Includes bibliographical references.
13
Soltanmoradi, Reyhaneh. "Structured Metallic Films for Enhanced Light Transmission and Absorption". Doctoral thesis, KTH, Optik och Fotonik, OFO, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166706.
Testo completoAbstract (sommario):
Photonic devices such as light emitters, detectors, solar cells etc. are playing increasingly important roles in modern society. Yet their structures and designs are still under constant improvement, driven mostly by advances in material science and progress in integration techniques. A common challenge in these devices is to precisely manage transmission and absorption of light when it enters or escapes active regions. In certain devices it is even required to have both high optical transmission as well as high electrical conductivity. The current thesis investigates how structured metallic films can be devised to meet these challenges. Our work demonstrates that nanostructured noble metals can be tailored as either transparent or highly absorptive at wavelengths of interest, with or without electrical conductivity.In the first part of this work, metallic photonic crystals in the form of a thin gold film with an array of holes were fabricated with various geometrical parameters (hole size, pitch and metal thickness) on different substrate materials to investigate the impact of each parameter on the transmittance spectra at mid- to long-wave infrared wavelengths. Pitch size is shown to be the dominating factor for the high-transmittance band positions. Fill factor and metal thickness collectively define the selectivity of the pass bands. The selective transmission of infrared light can be used to improve the performance of infrared detectors. In the second part of this work, a thin-film multilayer structure based on two coupled metal-insulator-metal optical resonators was investigated for achieving a transparent conductor at visible wavelength range. The fabricated silver-based sample has a figure of merit (transmissivity-over-resistance) comparable to that of the traditionally used indium tin oxide. Such structures can potentially be used in light-emitting diodes and displays. In the third part of this work, a thin gold nanoparticle layer is obtained from a thermal annealing process. The interplay between this nanoparticle layer and a substrate metal reflector gives rise to broadband extinction of light at the near-infrared wavelength range. Specular and diffuse reflectances were singled out. Samples with high absorption or high diffuse reflection are identified. The structures can potentially be incorporated in solar cells as diffuse back reflectors or as spectrally selective absorbers for solar thermal collectors. In the fourth part of this work, the possibility of using a metal-insulator-metal structure (based on titanium, alumina, and aluminum) for achieving artificial coloration is explored. Through a diffusion-assisted deposition procedure, the dielectric spacer has a laterally varying thickness. Thereby the sample exhibits a continuum of visible colors. The reflectance spectra of the fabricated sample in the visible range were measured, and agreement to theoretical calculation is found to be very good. The artificial colors can be patterned at various geometries. Their potential application, besides functioning as spectrally selective absorbers in optoelectronic devices, can be used for security applications of consumer and artistic products.QC 20150519
14
Cant, Nicola Elizabeth. "Electrostatic self assembly of multilayer films incorporating metallic nanoparticles". Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275671.
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Lim, Yong Yee. "Nanoindentation hardness studies of metallic surfaces and thin films". Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268686.
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Kienert, Jochen. "Ferromagnetism and interlayer exchange coupling in then metallic films". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2008. http://dx.doi.org/10.18452/15834.
Testo completoAbstract (sommario):
Die vorliegende Arbeit befasst sich mit dem ferromagnetischen Kondo-Gitter-Modell (s-d-, s-f-Modell) für Filmstrukturen. Die Spin-Fermion-Wechselwirkung des Modells kommt in Materialien vor, in denen lokalisierte Spins mit beweglichen Ladungsträgern wechselwirken, wie etwa in (verdünnten) magnetischen Halbleitern, Manganaten, oder Seltene-Erd-Verbindungen. Die durch die Ladungsträger vermittelte, indirekte Wechselwirkung zwischen den lokalisierten Spins reicht von der langreichweitigen, oszillierenden RKKY-Austauschwechselwirkung im Falle schwacher Kopplung bis zur kurzreichweitigen Doppelaustausch-Wechselwirkung bei starker Spin-Fermion-Kopplung. Beide Grenzfälle werden in dieser Arbeit durch die Abbildung des Problems auf ein effektives Heisenberg-Modell erfasst. Der Einfluss von reduzierter Translationssymmetrie auf die effektive Austauschwechselwirkung und auf die magnetischen Eigenschaften des ferromagnetischen Kondo-Gitter-Modells wird untersucht. Curie-Temperaturen werden für verschiedene Parameterkonstellationen berechnet. Die Auswirkungen von Ladungstransfer und von Gitter-Relaxation auf die magnetische Oberflächenstabilität werden betrachtet. Die Diskussion bezieht sich auf die Modifizierungen der Zustandsdichte und der kinetischen Energie im dimensionsreduzierten Fall, da die effektiven Austauschintegrale eng mit diesen Größen verknüpft sind. Die Bedeutung von Spinwellen für den Magnetismus dünner Filme und an der Oberfläche wird gezeigt. Die Interlagen-Austauschkopplung stellt ein besonders interessantes und wichtiges Beispiel der indirekten Wechselwirkung zwischen lokalisierten Momenten dar. Im Rahmen einer RKKY-Behandlung wird die Kopplung zwischen Monolagen in dünnen Filmen untersucht. Sie wird entscheidend durch die Art der ebenen und senkrechten Ladungsträgerdispersion bestimmt und ist jenseits eines kritischen Wertes der Fermi-Energie stark unterdrückt. Schließlich wird die temperaturabhängige magnetische Stabilität von interlagen-gekoppelten dünnen Filmen behandelt und die Bedingungen für einen temperaturgetriebenen magnetischen Reorientierungsübergang werden diskutiert.This thesis is concerned with the ferromagnetic Kondo lattice (s-d, s-f) model for film geometry. The spin-fermion interaction of this model refers to materials in which localized spins interact with mobile charge carriers like in (dilute) magnetic semiconductors, manganites, or rare-earth compounds. The carrier-mediated, indirect interaction between the localized spins comprises the long-range, oscillatory RKKY exchange interaction in the weak-coupling case and the short-range double-exchange interaction for strong spin-fermion coupling. Both limits are recovered in this work by mapping the problem onto an effective Heisenberg model. The influence of reduced translational symmetry on the effective exchange interaction and on the magnetic properties of the ferromagnetic Kondo lattice model is investigated. Curie temperatures are obtained for different parameter constellations. The consequences of charge transfer and of lattice relaxation on the magnetic stability at the surface are considered. Since the effective exchange integrals are closely related to the electronic structure in terms of the density of states and of the kinetic energy, the discussion is based on the modifications of these quantities in the dimensionally-reduced case. The important role of spin waves for thin film and surface magnetism is demonstrated. Interlayer exchange coupling represents a particularly interesting and important manifestation of the indirect interaction among localized magnetic moments. The coupling between monatomic layers in thin films is studied in the framework of an RKKY approach. It is decisively determined by the type of in-plane and perpendicular dispersion of the charge carriers and is strongly suppressed above a critical value of the Fermi energy. Finally, the temperature-dependent magnetic stability of thin interlayer-coupled films is addressed and the conditions for a temperature-driven magnetic reorientation transition are discussed.
17
Masood, Ansar. "Functional Metallic Glasses". Doctoral thesis, KTH, Teknisk materialfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-101901.
Testo completoAbstract (sommario):
For decades, Metallic Glass, with its isotropic featureless structure while exhibiting outstanding mechanical properties was possible only at a high rate of quenching and with at least one dimension in the submicron regime. This limitation was overcome with the discovery of Bulk Metallic glasses, BMGs, containing three or more elements following the additional two empirical rules of optimum geometric size differences and negative energy of mixing among the constituent elements. Since then thousands of Fe-, Ni-, Al-, Mg-, Ti- based BMGs have been discovered and comprehensively investigated mainly by groups in Japan and USA. Yet the discovery of new combinations of elements for BMGs is alchemy. We do not know with certainty which element when added will make possible a transition from being a ribbon to a bulk rod. In this thesis we report a discovery of castable BMGs rods on substitution of Fe by nickel in an alloy of FeBNb which could otherwise have been only melt-spun into ribbons. For example, we find that substitution of just 6 at.% of Fe raises the glass forming range, GFA, to as much as ∆Tx =40K while the other parameters for GFA like Trg, γ, and δ reach enhanced values 0.57, 0.38, and 1.40 respectively. Furthermore, the electrical conductivity is found to increase by almost a factor of two. Magnetically it becomes softer with coercivity 260mOe which further reduces to much lower values on stress relaxation. Ni does not seem to carry a magnetic moment while it enhances the magnetic transition temperature linearly with Ni concentration. We have investigated the role of Ni in another more stable BMGs based FeBNbY system in which case ∆Tx becomes as large as 94K with comparable enhancement in the other GFA parameters. Due to the exceptional soft magnetic properties, Fe-based bulk metallic glasses are considered potential candidate for their use in energy transferring devices. Thus the effect of Ni substitution on bulk forming ability, magnetic and electrical transport properties have been studied for FeBNb and FeBNbY alloy systems. The role of Ni in these systems is densification of the atomic structure and its consequence. We have exploited the superior mechanical properties of BMGs by fabricating structures that are thin and sustainable. We have therefore investigated studies on the thin films of these materials retaining their excellent mechanical properties. Magnetic properties of FeBNb alloy were investigated in thin films form (~200-400nm) in the temperature range of 5-300K. These Pulsed Laser deposited amorphous films exhibit soft magnetism at room temperature, a characteristic of amorphous metals, while they reveal a shift in hysteresis loop (exchange anisotropy, HEB=18-25Oe), at liquid helium temperature. When thickness of films is reduced to few nanometers (~8-11nm), they exhibit high transparency (>60%) in optical spectrum and show appreciably high saturation Faraday rotation (12o/μm, λ= 611nm). Thin films (~200-400nm) of Ni substituted alloy (FeNiBNb) reveal spontaneous perpendicular magnetization at room temperature. Spin-reorientation transition was observed as a function of film thickness (25-400nm) and temperature (200-300K), and correlated to the order/disorder of ferromagnetic amorphous matrix as a function of temperature. These two phase films exhibits increased value of coercivity, magnetic hardening, below 25K and attributed to the spin glass state of the system. Using the bulk and thin films we have developed prototypes of sensors, current meters and such simple devices although not discussed in this Thesis. Ti-based bulk metallic glasses have been attracting significant attention due to their lower density and high specific strength from structural application point of view. High mechanical strength, lower values of young’s modulus, high yield strength along with excellent chemical behaviors of toxic free (Ni, Al, Be) Ti-based glassy metals make them attractive for biomedical applications. In the present work, toxic free Ti-Zr-Cu-Pd-Sn alloys were studied to optimize their bulk forming ability and we successfully developed glassy rods of at least 14mm diameter by Cu-mold casting. Along with high glass forming ability, as-casted BMGs exhibit excellent plasticity. One of the studied alloy (Ti41.5Zr10Cu35Pd11Sn2.5) exhibits distinct plasticity under uniaxial compression tests (12.63%) with strain hardening before failure which is not commonly seen in monolithic bulk metallic glasses.QC 20120906
Hero-m
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Zhang, Qiang. "Ultrafast spin dynamics in half-metallic ferromagnetic thin film /". View online version; access limited to Brown University users, 2005. http://wwwlib.umi.com/dissertations/fullcit/3174709.
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Brett, Michael Julian. "Stoichiometry control mechanisms of bias sputtered zinc oxide films". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25579.
Testo completoAbstract (sommario):
This thesis reports the first detailed study of the stoichiometry control mechanisms and physical properties of ZnO films deposited by dc planar magnetron sputtering of a Zn target in a reactive Ar/0₂ atmosphere. Control of film stoichiometry was achieved using a subsidiary rf discharge at the substrate and a reactive gas baffle surrounding the target. The reactive gas baffle was shown to enhance film oxidation by decreasing the metal flux to the substrate and increasing the oxygen partial pressure near the substrate. Rutherford backscattering analysis of film stoichiometry demonstrated that the effect of the rf discharge was to increase the O/Zn composition ratio. This oxidation was shown to occur through preferential resputtering and preferential evaporation of excess Zn and by activation and ion plating of oxygen species. Resputtering and evaporation rates were found to be enhanced above that expected for bulk Zn, due to the weak bonding of surface adatoms during film growth.
Conducting ZnO films produced at various values of the rf-induced substrate bias voltage were characterized for electrical, optical and structural properties using Hall probe,. X-ray diffraction, electron microscope, and visible and infrared spectroscopy techniques. Films deposited at low substrate bias (0 to -50V) were found to have a large Zn excess (15%) resulting in low electron mobilities (1 cm²/Vs), high resistivities (10⁻² Ωcm) and were strongly absorbing in the visible. Films deposited at high substrate bias were nearly stoichiometric, optically transparent and had high electron mobilities (15 cm²/Vs) resulting in low resistivity (10⁻³ Ωcm). The optical properties of transparent conducting films for wavelengths 0.4 to 20 /im were modelled by the Drude theory of free electrons using measured electrical transport properties.
The original goal of this work, to develop a heat mirror coating suitable for manufacture, was achieved by bias sputter deposition of ZnO onto uncooled polyester sheet at deposition rates approaching 75 nm/min. The best heat mirror films had a transmission to solar energy of 75% and an 85% reflection of 300 K blackbody radiation.Science, Faculty of
Physics and Astronomy, Department of
Graduate
20
Dean, Colin. "Micromagnetic calculations of the magnetic properties of thin metallic films". Thesis, University of Central Lancashire, 1993. http://clok.uclan.ac.uk/19941/.
Testo completoAbstract (sommario):
A micromagnetic model has been developed to simulate the magnetisation in a metallic thin film. This is achieved by energy minimisation techniques. The energy of each grain in the medium includes Zeeman, anisotropy, magnetostatic and exchange. The magnetostatic energy is incorporated by considering each grain as a point dipole and its a magnitude was obtained in collaboration with J.J. Miles. The exchange coupling is incorporated by utilising the phenomenological expression introduced by Zhu and Bertram. The model consists of one thousand grains on a hexagonal lattice with periodic boundary conditions applied. The model was initially used to compute hysteresis loops and these agreed with loops produced by other micromagnetic models. AC Erased states were obtained by a technique we have developed based on simulated annealing. This produced erased states which were of low energy and well correlated. The erased state was found to consist of vortices, which increased in size as the exchange coupling increased. The difficulty of obtaining zero magnetisation was also found to increase as the exchange coupling increased - a problem also found experimentally. The Al plot was calculated from a comparison with the computed remanence curves. The Al plot undergoes a change from being negative in the purely magnetostatic case to positive in the presence of strong exchange coupling. This change in the form of Al agrees with experimental investigations. Furthermore, the magnitude of the magnetostatic interaction was varied. It was shown that by keeping the exchange coupling constant and varying the magnetostatic interactions, it was possible to change the form of Al. Thus, it is the detailed balance of the exchange and magnetostatic interaction which is of importance. The model was then extended to simulate magnetic force microscopy (MFM). The ac erased, dc demagnetised and recording medium consisting of two oppositely magnetised bits have been scanned to produce MFM images. The image of the recording medium agrees with the experimental image. It is anticipated that the images which we have produced will enhance the understanding of experimental images.
21
Narain, Pradeep Krishna. "Morphology and texture of metallic thin films on ceramic substrates". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243157.
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Zamani, Atieh. "Metallic Amorphous Thin Films and Heterostructures with Tunable Magnetic Properties". Doctoral thesis, Uppsala universitet, Materialfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-239950.
Testo completoAbstract (sommario):
The primary focus of this thesis is to study the effect of doping on magnetic properties in amorphous Fe100−xZrx alloys. Samples with compositions of x = 7,11.6 and 12 at.% were implanted with different concentrations of H. Moreover, the samples with a composition of x = 7 at.% were also implanted with He, B, C and N. Magnetic measurements were performed, using SQUID magnetometry and MOKE, in order to compare the as-grown and the implanted films. The Curie temperature (Tc) increases and the coercivity (Hc) decreases, with increasing dopant volume. We also found that Hc increases with temperature for B and C doped samples. Magnetization curves at low temperature validate the presence of non-collinear spin configurations in the as-grown films, which is suppressed after doping, resulting in films with tunable soft magnetic properties. We have also studied the effect of interlayer mixing and finite size effects on FeZr in Fe92Zr8/AlZr multilayer films, and found an anomalous increase of Tc with decreasing thickness. Strain induced changes in the magnetization of an amorphous Co95Zr5 film at the orthorhombic phase transition of the BaTiO3 substrate, was also studied. The results show that structural modifications of the substrate increases the stress and hence changes the magnetic anisotropy in the amorphous Co95Zr5 layer. Finally, the magnetization reversal of Co and CoX heterostructures, with X being Cr, Fe, Ni, Pd, Pt and Ru, has been studied. For this purpose a synthetic antiferromagnet structure, FM/NM/FM, was used, where FM is a ferromagnetic Co or CoX layer and NM is a nonmagnetic Ru spacer layer. The FM layers are coupled antiferromagnetically across the NM layer. For a range of FM layer thicknesses, the exchange stiffness parameter Aex and the interlayer coupling (JRKKY ) of the Co or CoX layers were obtained. This is done by fitting M(H) curves, measured by SQUID magnetometry, to a micromagnetic model. The alloying in CoX resulted in a decreasing Aex and also a reduced MS. The experimental results are in a good agreement with DFT calculations.
23
Hart, Robin. "Electrodeposition of metallic multilayers and single crystal films on GaAs". Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319397.
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Glover, Stephanie E. "Characterisation of half-metallic thin films using polarised neutron reflectometry". Thesis, University of Warwick, 2018. http://wrap.warwick.ac.uk/109208/.
Testo completoAbstract (sommario):
Half-metallic (HM) materials are promising candidates for spintronic devices due to their 100% spin polarisation at the Fermi level and their high TC, making them robust to thermal fluctuations. For HM to be used in devices, they need to be in thin film form and retain both SP and magnetisation through the film and at the substrate/interface. High quality thin films of both Co2FeAl0.5Si0.5 and Fe3O4 described in this thesis have been grown by collaborators, and are theoretically predicted to be HM. HM in a film can be indicated by measurements of the magnetic moment. This thesis shows that polarised neutron reflectivity (PNR) data from these HMs can be fitted to obtain the magnetisation profiles perpendicular to the surface. PNR measurements are fitted simultaneously with X-ray reflectivity. Complementary techniques such as microscopy, magnetometry and X-ray diffraction are used in order to limit the fit, give confidence in the extracted structural and magnetic profiles and to help explain the underlying reasons for the magnetic properties. One chapter is dedicated to describing the set up and methodology of reflectivity fitting. Co2FeAl0.5Si0.5 grown on Si(111) has both extended surface and interface regions, the latter due to Si diffusion as shown by microscopy. The structural and magnetic parameters in this region are not well defined and become strongly coupled creating non-unique solutions to the fit of the reflectivity data. One model uses electron energy loss spectroscopy data to constrain the composition across the interface, which limits the fit. This sample is found to have a magnetic dead layer at the interface. Co2FeAl0.5Si0.5 grown on Ge(111) on the other hand, has a small interface region due to lack of Ge diffusion from the substrate. As the fit parameters are better defined, a unique solution to the reflectivity data is obtained. A magnetic moment corresponding to HM is obtained for both Ge grown films with the decrease in magnetisation towards the substrate. Three samples of Fe3O4 grown on MgO(111) with different post-annealing temperatures were also studied. Structural and magnetic experimental techniques are combined to understand the affect post-annealing temperature has on the film properties. An unusual substrate/film epitaxial relationship is found out of plane: MgO(111)||Fe3O4(100). Further temperature dependent studies investigate the change in magnetism below the Verwey transition TV ~ 120 K.
25
Nyman, May. "Synthesis and characterization of precursors for chemical vapor deposition of metal oxide thin films". Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07112009-040219/.
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Jaffey, Deborah Mary. "The structure, electronic properties and reactivity of the Sm/Cu(111) system". Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254523.
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Craib, Glenn R. G. "Thin film structural determination and surface analysis". Thesis, University of Aberdeen, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320771.
Testo completoAbstract (sommario):
A combined approach to the use of surface analysis techniques and X-ray diffraction has been introduced. In particular the development of the microstructure of UHV evaporated thin metallic films has been investigated with a view to clarifying influences on microstructure (particularly texture). This study has shown the wide range of experimental parameters which affect the final film structure, such as temperature, oblique incidence and substrate roughness. An automated energy dispersive X-ray diffractometer has been developed for the study of thin film texture. The required corrections for loss of intensity due to sample positioning have been developed and verified. Pole figures have been collected for erbium and nickel thin films (thickness 200-1200 nm) grown on molybdenum or glass substrates. Results for the erbium films show a substantial effect on the texture of the film, contributed by the temperature of the substrate during deposition. The texture varies from mixed fiber at low temperature, to a strong single fiber orientation at around 663 K, to mixed fiber at higher temperatures. The strong orientation at 663 K has been shown to vary from either (002) to (101) depending on as yet unknown experimental conditions. The effect of substrate roughness appears to be only in the degree of orientation and it does not affect the overall nature of the texture of the film. The texture of the nickel films shows a form of "granular epitaxy" at substrate temperatures above 300 K. The presence of tensile stress within one of these nickel thin film samples has been determined and is interpreted to give support to a proposed mode of granular epitaxy.
28
Baddeley, Christopher John. "Structural, electronic and catalytic studies of Au/Pd systems". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309333.
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Chen, Tse-Shih. "Dependence of stress and resistivity of sputtered copper films on deposition conditions /". Online version of thesis, 1989. http://hdl.handle.net/1850/10686.
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30
Asano, H., N. Koduka, K. Imaeda, M. Sugiyama e M. Matsui. "Magnetic and junction properties of half-metallic double-perovskite thin films". IEEE, 2005. http://hdl.handle.net/2237/6775.
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Wardle, Richard M. "On the interpretation of ion scattering studies of ultrathin metallic films". Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/33677.
Testo completoAbstract (sommario):
Medium Energy Ion Scattering studies of the thin metallic film systems created by the deposition of Ag on AI(100), non AI(100) and Au on Fe(100) were conducted. Work was specifically focussed on expanding the arsenal of data analysis methods available to the researcher of such structures by the interpretation of the data obtainable from this, the most versatile, of the Rutherford backscattering based techniques. For the Ag on Al(100) system it has been shown that significant surface reconstruction occurs for a coverage of 1.05 ML. An investigation, by means of an original atom-by-atom simulation fitting approach was conducted, with the aim of examining the validity of a documented model of this reconstruction. The results suggested that the documented model is inadequate, but a more suitable model was not found. The 3.57 ML Ag coverage was studied extensively by means of quantitative comparison with simulations, including the use of a novel layer-by-Iayer compositional analysis technique. This study culminated in the production of a highly credible model based on the depth profiling of the first six atomic layers of a prospective, epitaxial, fcc structure. It was qualitatively argued that the 6.12 ML Ag film was fcc in nature with extremely limited intermixing between the substrate and the overlayer.
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Gruber, Patric Alfons. "Mechanical properties of ultra thin metallic films revealed by synchrotron techniques". [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-33206.
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Parker, Stephen Christy. "Particle nucleation, growth, and sintering of metallic films on oxide substrates /". Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/9788.
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Singh, Laura Jane. "Co₂MnSi Heusler alloy thin films". Thesis, University of Cambridge, 2005. https://www.repository.cam.ac.uk/handle/1810/34601.
Testo completoAbstract (sommario):
This thesis investigates the growth of intermetallic compounds by co-sputtering from single elemental targets. The preliminary work involved constructing a sputtering set-up to grow abinary alloy (Sm-Co) and investigating how to control the composition spread that was obtained. Having achieved this, a larger sputtering flange was built up to grow the ternary Heusler alloy, Co₂MnSi. Co₂MnSi has been predicted to be a half-metallic ferromagnet, which means that there is an energy gap in the minority spin band at the Fermi energy. This leads to 100% spin polarised conduction electrons, which would enable ideal spin-device performance to be obtained. Co₂MnSi is particularly promising because it is predicted to have a large energy gap in the minority band of ~0.4 eV and has the highest Curie temperature among the known Heuslers of 985 K. Initially, Co₂MnSi was grown on a-plane sapphire and stoichiometric films were single phase and highly (110) textured, without the use of a seed layer. They exhibited the bulk value of the saturation magnetisation, Ms and films grown at the highest deposition temperature (715 K) showed the lowest resistivity (47 μΩcm at 4.2 K) and the lowest room temperature coercivity (18 Oe). The spin polarisation of the transport current, Pt of a 400 nm film grown at this deposition temperature was 54%, consistent with measurements on bulk single crystals. Ms decreased with decreasing film thickness indicating a graded disorder. By growing on GaAs (001), which has a similar lattice parameter to Co₂MnSi it was expected that this disordered region would be confined to the first few atomic layers. However, this was not the case because interfacial reactions resulted in the formation of an epitaxial Mn-As region, and a thin interfacial layer that was Co-Ga rich. This prevented the lattice matching of the Co₂MnSi to the GaAs(001) hence hindering epitaxial growth of the Heusler. The reaction zone also meant that films exhibited a Ms slightly below the bulk value. The expected fourfold anisotropy was not obtained for this cubic material, which is most likely due to the anisotropy of the reconstructed GaAs surface. Inspite of this anomalous behaviour, Pt was 55%, similar to the result obtained on sapphire, indicating that either Pt is independent of orientation or that the Heusler surface reconstructs in the same way. Films showed some improved properties to films grown on a-plane sapphire, indicating the potential of growing on this technologically important substrate. With this in mind, pseudo spin valves involving Co₂MnSi as one of the ferromagnetic electrodes were fabricated in both the CIP and CPP configurations. Clear low-field spin-valve contributions were observed at 15 K but the MR values are much lower than that expected from a PSV with a predicted 100% spin polarised electrode.
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Starr, David E. "Microcalorimetric heats of adsorption, surface residence times and sticking probabilities of metals on metal-oxide, and silicon substrates /". Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/8492.
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Qiu, Chunong. "Preparation and investigation of doped ZnO films". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64065.
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Han, Qi. "Chemically modified electrodes with inorganic films of noble metal complexes and metal oxides : preparation, characterization and applications /". View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202002%20HAN.
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Abou, Mourad Houssam. "Metallic to insulating transition in disordered pulsed laser deposited silicide thin films". [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001000.
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Agrawal, Ashwin. "Bactericidal thin sol-gel films on metallic implants - an in-vitro study". Thesis, Boston University, 2012. https://hdl.handle.net/2144/12259.
Testo completoAbstract (sommario):
Thesis (M.A.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.Periprosthetic infections are a major complication of joint replacement and other orthopedic surgeries. The majority of these infections are caused by S. aureus which, when they grow on an implant, develop into a bacterial biofilm. The bacterial biofilms are very difficult to kill and have resistances up to one thousand fold more than their planktonic counterparts. Therefore, it is desirable to have a technology which can prevent biofilm growth on implants. Herein we demonstrate that the room temperature silica sol-gel process can be used to form thin films incorporating vancomycin and famesol on metallic implants. We evaluate the characteristics of these thin films and evaluate their bactericidal effects against methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA). We determined that thin sol-gel films release drugs through degradation which is both time-dependent and drug-load-dependent. In addition, it is found that famesol is useful for decreasing the "burst" release ofvancomycin resulting in more controlled drug delivery. It was determined that famesol has bactericidal effects against MSSA, but not against MRSA; however, famesol worked well as an adjuvant to vancomycin. When famesol was used as an adjuvant in combination with vancomycin, a 10 to 1000 fold decrease in bacterial film growth was seen on the implant. These results clearly demonstrated that the novel thin sol-gels films with vancomycin and famesol can be used for targeted drug delivery on implants to substantially prevent bacterial biofilm growth.
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Leib, Jeffrey Scott. "Relationships between grain structure and stress in thin Volmer-Weber metallic films". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/46682.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.Includes bibliographical references (leaves 150-154).
In Volmer-Weber growth, islands that nucleate on the substrate surface impinge and coalesce into grains of a continuous film. During deposition of these polycrystalline films, the intrinsic stress for materials of sufficiently high mobility often evolves through three distinct stages, switching from compressive to tensile and back to compressive. Many studies of stress evolution during this process have indicated that a tensile stress develops as the islands coalescence, with the peak stress occurring when the film become continuous. The magnitude of this tensile stress is strongly dependent on the grain structure. The grain structure is in turn strongly dependent on atomic processes at the substrate surface at the onset of film growth. In this study, Kinetic Monte Carlo simulations were used to investigate the relationship between characteristics of the amorphous surface, nucleation and growth of islands, and the tensile stresses observed as films form. It is demonstrated that island nucleation on amorphous substrates can be dominated by the spatial characteristics of the amorphous surface. The simulation parameters providing the best fit to experimental data from gold deposited on silicon nitride included a trapping energy of ET = 0.69 eV. The compressive stresses that develop have also been shown to reversibly change during interruptions of growth. One proposed model for this reversibility is that the compressive stress is related to adatom trapping and de-trapping at grain boundaries, while others attribute the stress to surface changes. In the current study, intrinsic stresses monitored in-situ using a capacitive curvature measurement system are studied with respect to the film grain structure, deposition rate, and substrate temperature.
(cont.) The kinetics of the post-deposition tensile rise receive special attention. The "reversible" compressive stress exhibited by polycrystalline, low melting point fcc metal films is found to be absent in epitaxial cases. The stress magnitude in polycrystalline films is shown to be inversely related to grain size and very weakly dependent on temperature. Densification stresses from abnormal grain growth are found to account for the post-deposition tensile rise. Finally, the compressive stresses observed during the deposition of polycrystalline, high mobility gold films is explained using a simple model of trapping of adatoms as grain boundary interstitials.
by Jeffrey S. Leib.
Ph.D.
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Laosiritaworn, Yongyut. "Modelling the magnetic properties of thin metallic films using Monte-Carlo simulation". Thesis, University of Warwick, 2002. http://wrap.warwick.ac.uk/73508/.
Testo completoAbstract (sommario):
In this thesis, Monte Carlo studies of the static critical behaviour of metallic magnetic thin-films are presented. The studies make use of a finite size scaling method designed for anisotropic shaped structures. This finite size scaling method is based on an assumption that a single correlation length is required to describe a thin-film close to its critical temperature and has lead to the derivation of formulae from which thin-film critical temperatures and exponents can be extracted. Monte Carlo simulations for Ising thin-films are carried out in order to verify the validity of the assumption and hence the formulae. Various algorithms and seed numbers for a random number generator are tested to minimise statistical errors. These studies also show the evolution from 2D to 3D-like behaviours as the films' thicknesses are increased. Critical temperatures and exponents are investigated for simple cubic (SC), body centred cubic (BCC) and face centred cubic (FCC) thin-films. Our Ising 2D and 3D results are also shown to give good agreement with previous Monte Carlo work. We then move on to study in a more realistic model of a magnetic thin-film in which the 'exchange parameters' and anisotropic constants are extracted from 'first principles' electronic structure calculations, and used in Monte Carlo simulations of a classical Heisenberg model. We model thin-films of Fe grown on a W(OOl) substrate which have been subjected to extensive experimental investigation. In line with the Mermin-Wagner theorem, we find a slow convergence for the magnetisation with the system size L in 2D which is consistent with expected absence of finite magnetisation in the finite temperatures in the thermodynamic limit. From the thin-film results in finite size systems, the magnetisation in the surface layers is weaker than those in the inner layers and a similar trend is found for the susceptibility. Slow magnetisation convergence with size is also observed for all thin-films (thickness varying from 2 to 8 layers). Because of this and the sensitivity to statistical errors, only critical temperatures and 'susceptibility critical exponents' can be extracted from the susceptibility functions. The results again show a crossover from 2D towards 3D-like behaviour. The critical temperatures are lower than those calculated from mean-field approximations and are in good agreement with experimental values where available. The differences in results between isotropic and anisotropic systems in which the anisotropic constants are very small in comparison to 'exchange interactions' are not significant.
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Karanikas, Christos Fotios. "Supercritical fluid deposition of thin metal films kinetics, mechanics and applications /". Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/dissertations/AAI3359900/.
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Kaplan, Maciej. "Thermal Stability of Amorphous MoSiZr Thin Films". Thesis, Uppsala universitet, Materialfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-298165.
Testo completoAbstract (sommario):
Metallic glass is a class of materials which have a disordered structure of atoms, due to this, glasses lack grains and grain boundaries, which are present in their crystalline counterparts. Metallic glasses have many interesting properties worth investigating, such as high corrosion resistance or high mechanical strength. However, metallic glasses are metastable and will therefore crystallise if heated above the crystallisation temperature. MoSiZr alloys have been studied and to gain knowledge of how the composition affects the crystallisation temperature, which enables further improvement of thermal stability. Crystallisation temperatures of the MoSiZr alloys were investigated by heat treatments in vacuum and ex-situ X-ray diffraction and X-ray reflectivity analysis. The highest thermal stability of the alloys was exhibited by M48Si48Zr4, Mo43Si50Zr7, Mo50Si40Zr10 and Mo45Si43Zr12, they remained amorphous after heat treatment at 1073 K. The resulting crystalline phases are Mo3Si, Mo5Si3 and ZrO2. Oxidation of Zr in the alloys is present only when the Zr content is at least 10 at%, crystallisation is otherwise mainly driven by formation of Mo3Si. Further improvement of the thermal stability is possible by introducing new alloying elements at the cost of those that promote crystallisation. Keeping the content of Zr below 10 at% is of great importance to prevent oxidation.
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Endle, James Patrick. "MOCVD of multimetal and noble metal films /". Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Arnold, C. S. "Magnetic susceptibility observation of a spin-reorientation transition in Fe/2 ML Ni(111)/W(110) films". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30067.pdf.
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Yoshida, Y., I. Hirabayashi, H. Kurosaki, H. Akata, K. Higashiyama e Y. Takai. "Growth mechanism of YBa2Cu3O7-y thin films on the metallic tapes by MOCVD". IEEE, 2001. http://hdl.handle.net/2237/6795.
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Beach, Geoffrey S. D. "The COxFe₁₀₀₋x metal/native oxide multilayer /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3090452.
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Smith, Bruce W. "Optically transparent IR reflective heat mirror films of ZNS-AG-ZNS /". Online version of thesis, 1989. http://hdl.handle.net/1850/11360.
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Dowling, Mark Craig. "Growth and magnetic characterisation of some metallic thin films and other related systems". Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361120.
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Ogasawara, Kazuyoshi. "Metallic Conduction of BO-Complex Conductive Langmuir-Blodgett Films, where BO is bisethylenedioxytetrathiafulvalene". 京都大学 (Kyoto University), 1996. http://hdl.handle.net/2433/86234.
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