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McCaughan, Adam Nykoruk. "Superconducting thin film nanoelectronics". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101576.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 163-171).
Superconducting devices have found application in a diverse set of fields due to their unique properties which cannot be reproduced in normal materials. Although many of these devices rely on the properties of bulk superconductors, superconducting devices based on thin films are finding increasing application, especially in the realms of sensing and amplification. With recent advances in electron-beam lithography, superconducting thin films can be patterned into geometries with feature sizes at or below the characteristic length scales of the superconducting state. By patterning 2D geometries with features smaller than these characteristic length scales, we were able to use nanoscale phenomena which occur in thin superconducting films to create superconducting devices which performed useful tasks such as sensor amplification, logical processing, and fluxoid state sensing. In this thesis, I describe the development, characterization, and application of three novel superconducting nanoelectronic devices: the nTron, the yTron, and the current-controlled nanoSQUID. These devices derive their functionality from the exploitation of nanoscale superconducting effects such as kinetic inductance, electrothermal suppression, and current-crowding. Patterning these devices from superconducting thin-films has allowed them to be integrated monolithically with each other and other thin-film superconducting devices such as the superconducting nanowire single-photon detector.
by Adam Nykoruk McCaughan.
Ph. D.
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Banerjee, Archan. "Optimisation of superconducting thin film growth for next generation superconducting detector applications". Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8573/.
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There is a growing demand for superconducting detectors with single photon sensitivity from near- to far infrared wavelengths. Emerging application areas include imaging, remote sensing, astronomy and free space communications. Two superconducting device technologies, superconducting nanowire single-photon detectors (SSPDs/SNSPDs) and microwave kinetic inductance detectors (MKIDs) have the potential to outperform off-the-self semiconductor technologies and offer scalability to large arrays. Fabrication of high efficiency superconducting detectors strongly depends on the quality of superconducting thin films. The original work presented in this thesis has explored the growth and optimization of several superconducting thin film materials for next generation superconducting detectors. Films have been grown in an ultra-high vacuum sputter deposition system and an atomic layer deposition system. Since its initial demonstration, NbN and NbTiN have been predominantly used as the base material for SNSPDs. In this work, we have explored the optimization of both the materials with an emphasis on NbTiN. NbTiN is optimized by heating the substrates to 800 ̊C achieving a Tc of 10.4 K for a film thickness of 5.5 nm on silicon substrate. Due to their crystalline nature superconducting properties of NbN or NbTiN thin films are strongly correlated with the lattice parameters of substrate properties. This causes a restriction on the substrate choice and integration of SNSPD devices with complex circuits. Amorphous superconducting materials can be promising alternatives for this purpose. We have explored growth and optimization of amorphous MoSi and MoGe thin films. Both the materials are co-sputtered to tune the composition. For 5 nm thick MoSi film on silicon substrate we obtain Tc of 5.5 K. For MKID fabrication, TiN can be an useful base material due to its high sheet resistance and widely tuneable superconducting properties. TiN thin films have been sputtered on heated (500 ̊C) silicon substrates with a Tc of 3.9 K for a 90 nm thick film. The dielectric constants of the thin films as a function of wavelength (270-2200 nm) have been determined via variable angle spectroscopic ellipsometry (VASE). Atomic structure and stoichiometry of the films have been characterized in high resolution transmission electron microscopy (HRTEM). This study enables us to precisely control film properties and thus tailor superconducting films to the requirements of specific photon-counting applications.
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Beringer, Douglas. "Thin Film Approaches to The Srf Cavity Problem: Fabrication and Characterization of Superconducting Thin Films". W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1499449840.
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Superconducting Radio Frequency (SRF) cavities are responsible for the acceleration of charged particles to relativistic velocities in most modern linear accelerators, such as those employed at high-energy research facilities like Thomas Jefferson National Laboratory’s CEBAF and the LHC at CERN. Recognizing SRF as primarily a surface phenomenon enables the possibility of applying thin films to the interior surface of SRF cavities, opening a formidable tool chest of opportunities by combining and designing materials that offer greater benefit. Thus, while improvements in radio frequency cavity design and refinements in cavity processing techniques have improved accelerator performance and efficiency – 1.5 GHz bulk niobium SRF cavities have achieved accelerating gradients in excess of 35 MV/m – there exist fundamental material bounds in bulk superconductors limiting the maximally sustained accelerating field gradient (approximately 45 MV/m for Niobium) where inevitable thermodynamic breakdown occurs. With state of the art niobium based cavity design fast approaching these theoretical limits, novel material innovations must be sought in order to realize next generation SRF cavities. One proposed method to improve SRF performance is to utilize thin film superconducting-insulating-superconducting (SIS) multilayer structures to effectively magnetically screen a bulk superconducting layer such that it can operate at higher field gradients before suffering critically detrimental SRF losses. This dissertation focuses on the production and characterization of thin film superconductors for such SIS layers for radio-frequency applications.
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Farrar, Simon Richard. "Excimer laser ablation characterisation for superconducting thin film applications". Thesis, University of Hull, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282366.
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Yoshida, Yutaka, Yusuke Ichino, Masashi Miura, Yoshiaki Takai, Kaname Matsumoto i Ataru Ichinose. "High critical current density in high field in Sm/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 6+y/ thin films". IEEE, 2005. http://hdl.handle.net/2237/6776.
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Yoshida, Yutaka, Kimihiko Sudoh, Yusuke Ichino, Izumi Hirabayashi, Yoshiaki Takai, 隆. 吉田 i 祐亮 一野. "Growth mechanism and surface morphologies of Sm/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 6+y/ thin films". IEEE, 2003. http://hdl.handle.net/2237/6746.
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Elfassy, Laurent Albert Isaac. "Josephson junctions in high temperature superconducting patterned thin film resonators". Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624725.
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Kumar, Dinesh. "Critical current and Lorentz force effects in superconducting thin films". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337985.
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Richardson, Kurt Antony. "The manufacture of high temperature superconducting tapes and films". Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242413.
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Guruswamy, Tejas. "Nonequilibrium behaviour and quasiparticle heating in thin film superconducting microwave resonators". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277214.
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In this thesis I describe work on developing theoretical and numerical models of supercon- ducting thin-film microwave resonators. Superconducting resonators are used in a variety of applications, one of which is as kinetic inductance detectors (KIDs). KIDs are ultra-low noise, highly sensitive, multiplexable detectors, with uses in a wide variety of fields including astrophysics, medical imaging, and particle physics. Resonators are also crucial for supercon- ducting qubit readout, superconducting mixers and parametric amplifiers, and as multiplexers for other devices. The results described in this thesis apply to all thin film resonators, but are primarily described in the context of KIDs. I develop models of how constant absorbed power affects superconducting thin films, driving them out of thermal equilibrium with the bath. Using the Chang & Scalapino equations, I calculate numerically the steady-state quasiparticle and phonon distributions for various sources of power (sub-gap and above-gap photons and phonons, single frequency and broadband). Many new results emerge, a few of which are: the quasiparticle heating effects of microwave power, explaining the experimentally measured saturation of resonator performance; the frequency dependence of the quasiparticle generation efficiency in the sub-mm wavelength range; and the importance of phonon trapping in thin films at low temperatures. I then use these nonequilibrium results in higher-level device models. Starting from a generic framework for resonators, I present and implement a model of a KID with variable thermal isolation. I calculate the effects of quasiparticle heating on both the large-signal and small-signal behaviour, highlighting the effects of electrothermal feedback caused by readout power. Electrothermal feedback is shown to be able to increase or decrease the magnitude and bandwidth of the responsivity and noise, depending on the operating point. Finally, I propose an experimental measurement of quasiparticle heating effects in a new device – a four-port ring resonator. In such a device, unlike in the standard two-port resonator, the device can be heated and read out independently. I develop detailed models for the thermal and electrical behaviour of these devices, and suggest a scheme by which the quasiparticle heating effects of microwave power, predicted in this thesis, can be measured.
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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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Hutson, D. "The design, construction and operation of practical thin film superconducting quantum interference devices (SQUIDs)". Thesis, University of Strathclyde, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382345.
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Ichino, Yusuke, Yutaka Yoshida, Kouichi Inoue, Toshinori Ozaki, Yoshiaki Takai, Kaname Matsumoto, Masashi Mukaida, Ryusuke Kita, Ataru Ichinose i Shigeru Horii. "Effect of BaZrO3 Addition and Film Growth on Superconducting Properties of (Nd,Eu,Gd)Ba2Cu3Oy Thin Films". IEEE, 2009. http://hdl.handle.net/2237/13894.
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Ichino, Yusuke, Kimihiko Sudoh, Koji Miyachi, Yutaka Yoshida, Yoshiaki Takai, 祐亮 一野 i 隆. 吉田. "Orientation mechanism of REBa/sub 2/Cu/sub 3/O/sub y/ (RE = Nd, Sm, Gd, Y, Yb) thin films prepared by pulsed laser deposition". IEEE, 2003. http://hdl.handle.net/2237/6741.
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尤志一 i Chi-yat Ben Yau. "Fabrication of superconducting YBa2Cu3Oy thin film on YSZ substrates with or without a Eu2CuO4 buffer layer". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31225421.
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Yau, Chi-yat Ben. "Fabrication of superconducting YBa2Cu3Oy thin film on YSZ substrates with or without a Eu2CuO4 buffer layer". Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22713402.
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SONG, YONG. "Electrical Transport Measurement of Niobium Thin Superconducting Film Above An Array of Magnetic Quantum Dots". University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1212102762.
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Valente-Feliciano, Anne-Marie. "Development of SRF monolayer/multilayer thin film materials to increase the performance of SRF accelerating structures beyond bulk Nb". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112254/document.
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La réduction du cout de construction et d’exploitation des futurs accélérateurs d particules, a grande et petite échelles, dépend du développement de nouveaux matériaux pour les surfaces actives des structures supraconductrices en radiofréquence (SRF). Les propriétés SRF sont essentiellement un phénomène de surface vu que la profondeur de pénétration (profondeur de pénétration de London, λ) des micro-ondes (RF) est typiquement de l’ordre de 20 à 400 nm en fonction du matériau. Lorsque les procédés de préparation de surface sont optimises, la limite fondamentale du champ RF que les surfaces SRF peuvent supporter est le champ RF maximum, Hc₁, au-delà duquel le flux magnétique commence à pénétrer la surface du supraconducteur. Le matériau le plus utilise pour des applications SRF est le niobium (Nb) massif, avec un champ Hc₁ de l’ordre de 170 mT, qui permet d’atteindre un champ accélérateur de moins de 50 MV/m. Les meilleures perspectives d’amélioration des performances des cavités SRF sont liées à des matériaux et méthodes de production produisant la surface SRF critique de façon contrôlée. Dans cette optique, deux avenues sont explorées pour utiliser des couches minces pour augmenter les performances des structures SRF au-delà du Nb massif, en monocouche ou en structures multicouches Supraconducteur-Isolant-Supraconducteur (SIS) : La première approche est d’utiliser une couche de Nb déposée sur du cuivre (Nb/Cu) à la place du Nb massif. La technologie Nb/Cu a démontré, au cours des années, être une alternative viable pour les cavités SRF. Toutefois, les techniques de dépôt communément utilisées, principalement la pulvérisation magnétron, n’ont jusqu’à présent pas permis de produire des surfaces SRF adaptées aux performances requises. Le récent développement de techniques de dépôt par condensation énergétiques, produisant des flux d’ions énergétiques de façon contrôlée (telles que des sources d’ions ECR sous ultravide) ouvrent la voie au développement de films SRF de grand qualité. La corrélation entre les conditions de croissance, l’énergie des ions incidents, la structure et les performances RF des films produits est étudiée. Des films Nb avec des propriétés proches du Nb massif sont ainsi produits. La deuxième approche est basée sur un concept qui propose qu’une structure multicouche SIS déposée sur une surface de Nb peut atteindre des performances supérieures à celles du Nb massif. Bien que les matériaux supraconducteurs à haute Tc aient un champ Hc₁ inférieur à celui du Nb, des couches minces de tels matériaux d’une épaisseur (d) inférieure à la profondeur de pénétration voient une augmentation de leur champ parallèle Hc₁ résultant au retardement de la pénétration du flux magnétique. Cette surcouche peut ainsi permettre l’écrantage magnétique de la surface de Nb qui est donc maintenue dans l’état de Meissner à des champs RF bien plus importants que pour le Nb massif. La croissance et performance de structures multicouches SIS basées sur des films de NbTiN, pour le supraconducteur, et de l’AlN, pour le diélectrique, sont étudiées. Les résultats de cette étude montrent la faisabilité de cette approche et le potentiel qui en découle pour l’amélioration des performances SRF au-delà du Nb massifThe minimization of cost and energy consumption of future particle accelerators, both large and small, depends upon the development of new materials for the active surfaces of superconducting RF (SRF) accelerating structures. SRF properties are inherently a surface phenomenon as the RF only penetrates the London penetration depth λ, typically between 20 and 400 nm depending on the material. When other technological processes are optimized, the fundamental limit to the maximum supportable RF field amplitude is understood to be the field at which the magnetic flux first penetrates into the surface, Hc₁. Niobium, the material most exploited for SRF accelerator applications, has Hc₁~170 mT, which yields a maximum accelerating gradient of less than 50 MV/m. The greatest potential for dramatic new performance capabilities lies with methods and materials which deliberately produce the sub-micron-thick critical surface layer in a controlled way. In this context, two avenues are pursued for the use of SRF thin films as single layer superconductor or multilayer Superconductor-Insulator-Superconductor structures: Niobium on copper (Nb/Cu) technology for superconducting cavities has proven over the years to be a viable alternative to bulk niobium. However the deposition techniques used for cavities, mainly magnetron sputtering, have not yielded, so far, SRF surfaces suitable for high field performance. High quality films can be grown using methods of energetic condensation, such as Electron Cyclotron Resonance (ECR) Nb ion source in UHV which produce higher flux of ions with controllable incident angle and kinetic energy. The relationship between growth conditions, film microstructure and RF performance is studied. Nb films with unprecedented “bulk-like” properties are produced. The second approach is based on the proposition that a Superconductor/Insulator/Superconductor (S-I-S) multilayer film structure deposited on an Nb surface can achieve performance in excess of that of bulk Nb. Although, many higher-Tc superconducting compounds have Hc₁ lower than niobium, thin films of such compounds with a thickness (d) less than the penetration depth can exhibit an increase of the parallel Hc₁ thus delaying vortex entry. This overlayer provides magnetic screening of the underlying Nb which can then remain in the Meissner state at fields much higher than in bulk Nb. A proof of concept is developed based on NbTiN and AlN thin films. The growth of NbTiN and AlN films is studied and NbTiN-based multilayer structures deposited on Nb surfaces are characterized. The results from this work provide insight for the pursuit of major reductions in both capital and operating costs associated with future particle accelerators across the spectrum from low footprint compact machines to energy frontier facilities
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Hoffmann, Axel F. "Periodic pinning in superconducting Nb thin films /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p9917952.
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Grigg, John Antony Hugh. "Superconductive Effects in Thin Cluster Films". Thesis, University of Canterbury. Department of Physics and Astronomy, 2012. http://hdl.handle.net/10092/10376.
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In this thesis, the superconductive and superresistive properties of thin percolating films of lead nanoclusters are presented. The samples were created by depositing clusters from an inert gas aggregation cluster source onto substrates held at either room temperature or 10K.
Observations of the characteristic behaviours of the samples were made through R(T ) and V (I) measurements. Several interesting features were observed - smooth and discrete steps in the R(I) curves, hysteresis between increasing and decreasing bias currents, and non-zero resistances at superconducting temperatures. Explanations are proposed in terms of theoretical models of several phenomena - phase slips, phase slip centres and hotspots - which have seen little prior application to percolating systems in literature.
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Pizzol, P. "Superconductive thin films for RF applications". Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3027993/.
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A particle accelerator is a complex machine, made of different parts constantly evolving in step with the technology advancements. One part of the accelerator, the LINAC, has nearly reached its maximum potential. This structure provides the acceleration through resonating cavities that under RF excitation transduce power into accelerating gradient. Superconductive structures are necessary to reduce the energy drain that these LINACs require. Niobium is the material of choice thanks to its high Tc and high field of first penetration Hc, but the research now has pushed the material to its limits. In addition, the infrastructure required to cool and operate a superconducting LINAC is very energy intensive and costly. New research avenues are opening aimed at reducing the costs of operating a superconducting LINAC. One of them is to create thin layers of niobium and niobium alloys on a high thermal conductive material, copper. If successful, the cost reduction in creating a functional Nb on Cu cavity versus a full Nb cavity will be substantial: a lower quantity of Nb will be required and better cooling will be achieved thanks to the higher thermal conductivity of Cu. This work aims at depositing Nb and Nb alloys on Cu substrates by using Chemical vapour deposition methods (CVD, PECVD, ALD) to verify if the obtained films are superconductive and can be employed in SRF applications. A series of different CVD chambers have been designed, built and evaluated to deposit the niobium-based superconducting films. Gas flow simulations were made by using Ansys Fluent to aid the understanding of the deposition results. The importance of a properly designed system has been highlighted, influencing factors like growth rate, uniformity and quality of the films. The deposition results were studied by electron microscopy (SEM, TEM, FIB), X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to investigate their structural properties while the superconductivity was assessed by residual resistivity ratio (RRR) measurements, SQUID and localized magnetometry. The use of the chlorine-based precursors was anticipated to be detrimental to the stainless steel reactors used, due to the repeated cycles of hot HCl gas exposure followed by air / moisture. However, the heightened corrosion speed of the chamber resulted in the inclusion of iron precipitates in the niobium films. This issue was addressed by redesigning the deposition chamber. One of the thesis objectives was to evaluate the feasibility of using chemical vapour deposition to coat copper for SRF cavities. CVD processes based on the chlorinated precursors (NbCl5 and TiCl4) have been evaluated and successful depositions of Nb, NbN, and NbTiN on copper substrates has been demonstrated. Further, it has been demonstrated that Nb-based films can be deposited by CVD on copper with superconductive properties for the first time. It has been shown that CVD can be used to produce niobium coatings, with Tc matching the bulk material although with lower field of first penetration. The temperature influenced greatly the films: above 500 C no chlorine residue was present in the films, and no oxygen contamination thanks to the UHV deposition chambers. The best results were obtained by depositing at 700 C, with an RRR of 30 and large crystallites (500 nm across). The results suggest that the films would have more bulk Nb like properties if deposited at higher temperatures, but going above 700 C would compromise the Cu substrate by softening it or melting it. The NbN and NbTiN films possess structural properties matching the literature reference materials, however it was not possible to separate these films from the copper structures by dissolution. Consequently, their superconductive properties could not be measured, however the availability of new local magnetometry techniques will make this feasible in the future.
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Burton, Matthew. "Superconducting Thin Films for The Enhancement of Superconducting Radio Frequency Accelerator Cavities". W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1530192378.
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Bulk niobium (Nb) superconducting radio frequency (SRF) cavities are currently the preferred method for acceleration of charged particles at accelerating facilities around the world. However, bulk Nb cavities have poor thermal conductance, impose material and design restrictions on other components of a particle accelerator, have low reproducibility and are approaching the fundamental material-dependent accelerating field limit of approximately 50MV/m. Since the SRF phenomena occurs at surfaces within a shallow depth of ~1 µm, a proposed solution to this problem has been to utilize thin film technology to deposit superconducting thin films on the interior of cavities to engineer the active SRF surface in order to achieve cavities with enhanced properties and performance. Two proposed thin film applications for SRF cavities are: 1) Nb thin films coated on bulk cavities made of suitable castable metals (such as copper or aluminum) and 2) multilayer films designed to increase the accelerating gradient and performance of SRF cavities. While Nb thin films on copper (Cu) cavities have been attempted in the past using DC magnetron sputtering (DCMS), such cavities have never performed at the bulk Nb level. However, new energetic condensation techniques for film deposition, such as High Power Impulse Magnetron Sputtering (HiPIMS), offer the opportunity to create suitably thick Nb films with improved density, microstructure and adhesion compared to traditional DCMS. Clearly use of such novel technique requires fundamental studies to assess surface evolution and growth modes during deposition and resulting microstructure and surface morphology and the correlation with RF superconducting properties. Here we present detailed structure-property correlative research studies done on Nb/Cu thin films and NbN- and NbTiN-based multilayers made using HiPIMS and DCMS, respectively.
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Bogorin, Daniela Florentina. "Superconducting Iridium Thin Films as Transition Edge Sensors". Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/190.
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Transition edge sensors are the detectors of choice for a wide range of applications; from dark matter search, neutrino search, to cosmic radiation detection from near infrared to millimeter wavelengths. We are developing transition edge sensors using superconducting iridium thin films and we are proposing their use for future dark matter and neutrino search experiments. Our Ir films are deposited using an radio frequency (RF) magnetron sputtering and photolithographic techniques and measured using an adiabatic refrigerator capable of reaching temperatures of a few tens of mK. This thesis presents a detailed description of superconducting iridium thin films from the fabrication process to the characterization of the film properties at room temperature and low temperature. Alternative options for the bias circuit used to read out the TES signals will be discussed, we are proposing the use of RLC resonant circuits and transformers instead of SQUIDS.
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Satchell, Nathan David. "Hybrid superconducting/ferromagnetic thin films for super-spintronics". Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15556/.
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This thesis examines the interaction between superconductivity and inhomogeneous ferromagnetism. Through careful engineering of the interface, it is possible to unlock a new spin aligned triplet Cooper pair, which is capable of penetrating and modifying the magnetisation of a ferromagnet in proximity to a singlet, s-wave, BCS, superconductor. This triplet state is the building block for the new class of super-spintronic devices. Two candidate ferromagnetic systems in which to study the spin aligned triplet are considered. Firstly, the rare-earth ferromagnet erbium is fabricated using sputter deposition. Neutron diffraction measurements show the retention of the conical magnetic state in the thin film form for the first time. This conical state makes it an ideal candidate material for triplet Cooper pair generation. Placing erbium next to superconducting niobium has a drastic effect on the critical temperature of the superconductor, causing a suppression and oscillation of Tc with erbium thickness. In addition the remanent state of erbium at a single thickness can be used as a control to switch the niobium from the superconducting state into the normal state. The second system studied is the superconducting spin valve. In this system the inhomogeneity is engineered in a multi-layer structure using exchange biased Co. To study the nature and extent of the triplet Cooper pair in this structure, large scale facility techniques are employed to look for expected changes to the magnetic state of the heterostructure, with the onset of superconductivity. Surprisingly, no observation directly attributable to the triplet Cooper pair was observed. Instead a new type of induced ferromagnetism in a normal metal coupled to the superconducting spin valve was discovered.
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Schneider, Christof Walter. "Inductive characterisation of thin superconducting films and bilayers". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337384.
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Lai, H. C. "The deposition of high temperature superconducting thin films". Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317209.
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Vernon-Parry, Karen Dorothy. "The microstructure and properties of superconducting thin films". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280799.
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Bramley, Annette. "Thallium-based superconducting thin films for microwave applications". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364170.
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Abu, Bakar Mizarina. "Microwave properties of high temperature superconducting thin films". Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289384.
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One of the most exciting studies of contemporary physics is that of high temperature superconductor (HTS). Since its discovery, a large body of experimental and theoretical work by various groups has attempted to achieve a common understanding of this phenomenon. One of the main driving forces for applications centres on the possibility of new and improved microwave devices based on HTS materials, mainly due to the large reduction in the surface resistance that HTS has to offer. However, various problems need to be addressed before the use of HTS materials can be justified, for example fundamental issues such as the nonlinearity of these materials with respect to microwave power, which form the basis of this work. Microwave measurements were conducted on four magnetron sputtered and three laser ablated, Icm2 YBCO thin films, grown on LaAI03 and MgO substrates, respectively, employing the dielectric (rutile) resonator and coplanar resonator techniques. The low power response of the films was initially analysed, looking for clues to the underlying pairing mechanisms in these films. Power dependence and microwave intennodulation distortion (lMD) measurements were conducted between 12 K to 60 K to investigate the nonlinear response of the films, both in zero and finite dc (10 mT) fields. The effect of patterning on the microwave response of the films was also studied. From these measurements, it was observed that the microwave losses of these films are extrinsic in nature, probably a consequence of weak links/defects, and the results also show that films fabricated from the same technique can have significantly varying quality.
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Alani, Ahmed. "Preparation and properties of ceramic superconducting thin films". Thesis, Liverpool John Moores University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261443.
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Lee, Hu Jong. "Two dimensional phase transitions in superconducting thin films /". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487261919112954.
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Thiede, David Anthony 1965. "Optical response in high temperature superconducting thin films". Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278027.
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Since the discovery of a class of superconducting materials with critical temperatures as high as 125 degrees kelvin, there has been a great deal of research interest in their possible application to optical radiation detection, particularly in the infrared spectrum. The motivation for this research is the promise of a fast detector operating at elevated temperatures that is sensitive to low level optical signals and that operates out to the far IR. It has been shown that thin films of these high temperature superconductors (HTS) exhibit a change in their electrical properties when exposed to optical radiation. However, in order to make a practical detector out of HTS materials, the mechanisms of this response must be fully understood. The purpose of this research is to investigate the spectral, temporal and thermal characteristics of this electrical response in an effort to better understand the mechanisms involved.
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Hummert, Stephanie Maria. "Magneto-Optical Imaging of Superconducting MgB2 Thin Films". W&M ScholarWorks, 2007. https://scholarworks.wm.edu/etd/1539626854.
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Grira, Sarra. "Microstructure, texture and superconductive properties of High Temperature Superconducting "HTS" oxides : yBCO thin films and bulk NBCO and YBCO". Thesis, Metz, 2009. http://www.theses.fr/2009METZ005S/document.
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Ce travail concerne l'étude de la texture et de la microstructure en relation avec les propriétés supraconductrices Tc et Jc de supraconducteurs haute température critique SHTc : YBCO et NBCO. Les techniques de caractérisation utilisées pour la microstructure sont la diffraction de RX et la diffraction d'électrons (Electron Back-Scatter Diffraction) "EBSD". Tc et Jc ont été déduits des mesures d'aimantation et de susceptibilité magnétique au SQUID (Superconducting Quantum Interference Device) et PPMS (Physical Properties Measument System). La première partie de l'étude traite de la caractérisation de la texture de couches minces SHTc d'YBCO, et de la possibilité de déterminer les relations d'épitaxie par EBSD entre le film déposé et la couche tampon. Ce type d'échantillon est constitué d'un substrat de saphir sur lequel 3 couches successives ont été déposées dont 300 nm de YBCO, destinées aux applications électrotechniques comme limiteurs de courant. La deuxième partie concerne l'étude de matériaux massifs supraconducteurs YBCO et NBCO fabriqués par différentes techniques. L'effet du dopage d'YBCO avec de l'argent a été étudié sur des échantillons fabriqués par la technique dite de "texturation par croissance orientée" soit MTG (Melt Textured Growth) et sous une faible pression partielle d'oxygène. Le dopage jusqu'à un certain pourcentage d'argent améliore la microstructure ainsi que la densité de courant critique. Une comparaison des caractéristiques physiques et structurales d'échantillons NBCO oxygénés ex-situ et YBCO in-situ, élaborés par MTG sous champ magnétique intense a été effectuée. De même des échantillons NBCO texturés par la technique de fusion de zone (Zone Melting) oxygénés respectivement in-situ et ex-situ ont été étudiés. Ils présentent des textures similaires avec présence de macles pour NBCO oxygéné ex-situThe aim of this work is the study of crystallographic texture and microstructure in connection with the superconducting properties (Tc and Jc) of High Temperature Superconducting (HTS) materials: YBCO and NBCO. Microstructure is studied by X-Ray Diffraction (XRD) and Electron backscatter Diffraction (EBSD). The Determination of critical temperature (Tc) and critical current density (Jc) are made with Superconducting Quantum Interference Device (SQUID) magnetometer or Physical Properties Measurement System (PPMS). The first part of this work investigates the crystallographic textures of the YBCO film by using EBSD in order to deduce the epitaxial relationship between the superconducting layer and the buffer layer. This thin film is made up of three successive deposits (among which 300 nm of YBCO), used in fault current limiters for electrical engineering applications. The second part presents the study of NdBa2Cu3O7-d (NBCO) and YBCO bulks prepared by various techniques. The effect of silver doping of YBCO has been studied on samples prepared by the Melt Textured Growth (MTG) technique under low oxygen partial pressure. The doping up to a given amount of silver enhances the microstructure and the critical current density. A comparison of the physical and structural characteristics between NBCO oxygenated exsitu and YBCO oxygenated in-situ, prepared by MTG under high magnetic field has been made. Zone-melted NBCO samples textured by zone melting method oxygenated respectively in-situ and ex-situ have been studied. These samples exhibit the same texture with the occurrence of twins for the NBCO oxygenated ex-situ
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Cuadra-Solís, Pedro-de-Jesús. "Vortex Dynamics in Superconducting Thin Films under Microwave Fields". Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/348552.
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In this thesis we have studied the vortex dynamics in type-2 superconducting thin films made of La1.82Sr0.18CuO4, patterned Pb and MgB2, by means of the combination of microwave, dc and ac measurements. In particular, we explore first the magnetic moment response in real time under continuous and pulsed microwave mode, and second commensurability effects both in presence of microwave fields under ac susceptibility mode and using microwave reflection spectrometry.
To carry out these measurements, we have designed and developed a low-temperature microwave setup to be used inside of an rf-SQUID-based magnetometer. This layout has been used to perform measurements under different microwave modes, namely sweeping, pulsed and power reflected. A theoretical model has been proposed to obtain an estimation of the characteristic frequencies and the electric and magnetic fields of the resonant structure formed by a multi-turn coil with a sample loaded in its core.
We presents the results on vortex dynamics of superconducting thin films made of La1.82Sr0.18CuO4, patterned Pb and MgB2 under continuous and pulsed microwave modes. In the first set of experiments, the temporal- and frequency-dependent magnetic moment has been investigated at different values of the temperature, dc magnetic fields, and nominal microwave power in the three samples. Irregularities forming ripples, small steps, jumps and negative peaks at discrete frequency values under different thermodynamics variables (temperature and dc magnetic field) and microwave nominal powers have registered. The presence of these frequency-triggered anomalies has been interpreted as nucleation of instabilities in the propagation of the flux front and explained by considering the energy fed at some specific resonant modes, the vortex dynamics in thin-film geometry, and the contribution from the microwave electric and magnetic fields generated in the coil. In the second set of experiments, the temporal evolution of the sample magnetization has been recorded when single microwave pulses are applied at fixed values of temperature, dc magnetic fields, pulse duration and nominal power in the La1.82Sr0.18CuO4, and MgB2 samples. The onset of a significant variation in the sample magnetization which exists below threshold values of temperature, dc magnetic field, and pulse duration is interpreted as an avalanche-like flux penetration. The microwave fields are suggested to contribute to the nucleation of the fast vortex diffusion. The additional microwave electric field is surmised to guarantees the occurrence vortex instabilities under adiabatic conditions via the enhancement of the flux flow resistivity.
We expose results obtained for patterned Pb under ac susceptibility and microwave power reflection techniques. The in-phase and out-of-phase components of the ac susceptibility are measured under the combination of crossed dc and microwave magnetic fields at different fixed values of microwave power and frequency for temperature close to Tc. The results show that commensurability effects are strongly dependent on the values of the frequency and nominal power of the microwave radiation. The magnetic field dependence of the microwave backward reflection coefficient is studied in a wide range of temperature (from 6.80 K to 7.20 K) at different fixed microwave resonant modes and powers. Commensurability effects related to the matching of the vortex lattice parameter and the antidot array spacing at integer and fractional matching field values have been observed as peaks in the magnetic field dependence of the microwave backward reflection coefficient for different values of temperature, frequency and power. These peaks appear as a result of the contribution of the vortex dynamics to the reflected signal a the matching fields and their observation depends on the values of the microwave power supplied to the sample.L’objectiu d’aquesta tesi és estudiar la dinàmica de vòrtexs en diverses capes primes superconductores de tipus-2. En particular, explorem la resposta del moment magnètic en temps real a camps continus i polsats de microones. A més, estudiem els efectes de commensurabilitat mitjançant mesures de susceptibilitat magnètica en presència de camps de microones, i fent servir també espectrometria de reflexió de microones. Les mostres utilitzades en aquesta tesis són mostres de capes primes superconductores fetes de LaSrCuO, Pb amb una formació periòdica micro-forats o antidots i MgB2. Les mesures dels moments magnètics, de la magnetització en funció del temps i de la susceptibilitat magnètica es van realitzar amb un magnetòmetre MPMS basat en un dispositiu rf-SQUID. Per realitzar mesures de microones a baixes temperatures, es va dissenyar una sonda formada per un cable coaxial semi-rígid el qual acaba en una bobina de múltiples voltes amb la mostra localitzada al seu nucli (CS). Per caracteritzar l’estructura ressonant formada pel CS, s’ha proposat un model teòric basat en el ressonador helicoïdal. L’estudi de la dinàmica de vòrtexs sota l’escombrat de freqüència es va dur a terme en les tres mostres esmentades anteriorment. La relaxació monòtona és interrompuda per la presència d’irregularitats en forma de salts, pics negatius, ondulacions i petits passos. Aquestes anomalies apareixen a cert valors de la freqüència de microones i a diferents valors de les variables termodinàmiques (temperatura i camp magnètic continu) i dels paràmetres d’excitació de microones (potència i freqüència). La presència d’irregularitats en la resposta del moment magnètic en funció de la freqüència apareix determinada per la freqüència ressonant del CS. Altres aspectes que poden afavorir l’aparició d’aquestes irregularitats són la geometria de la capa fina i la contribució dels camps elèctrics i magnètics de microones. Aquests últims resulten significatius a la vora de la regió mostra-bobina i poden ajudar a activar inestabilitats termo-electromagnètiques dels vòrtexs. Particularment, la contribució del camp elèctric pot facilitar el desenvolupament d’aquesta mena d’inestabilitat en condicions adiabàtiques. El registre de la variació temporal de la magnetització sota la influència d’un pols de microones es va dur a terme en las mostres LaSrCuO i MgB2. Les corbes d’evolució temporal de la variació de la magnetització mostren clarament un règim de ràpida difusió dels vòrtexs. Aquest règims existeixen dins d’un marge de valors del camp magnètic continu, la temperatura, i la durada del pols. A més, aquestes corbes presenten valors de màxima difusió en funció d’aquests mateixos paràmetres. La presència d’aquestes inestabilitats disparades pels pols sembla que resulten de la contribució dels camps elèctrics i magnètics de microones i de la geometria de capa prima. Les mesures dels components de la susceptibilitat magnètica en funció del camp magnètic continu irradiat amb diferents valors de potència i freqüència de microones mostren els característics efectes de commensurabilitat per a múltiples enters i fraccionaris dels camps de coincidència (matching). Les corbes a diferents valors de freqüència i potència mostra que l’augment de qualsevol d’aquest dos paràmetres resulta en la reducció de l’apantallament i l’increment de la dissipació. Aquest efecte va ser confirmat realitzant mesures de les components de la susceptibilitat magnètica en funció de la potència als diferents valors de la freqüència de microones. Les corbes del mòdul del coeficient de reflexió de microones en funció del camp magnètic continu a una potència i freqüència de microones fixes, mesurades a diferents valors de temperatura, mostren clarament els efectes de commensurabilitat. L’empremta d’aquest efecte es mostra en forma de pics a valors enters i fraccionaris dels camps de coincidència. L’observació dels pics a les corbes del coeficient de reflexió apareix com a resultat de la contribució de la dinàmica de vòrtexs al senyal reflectit als camps de coincidència. La presència d’aquest pics es pot explicar considerant els conceptes de la conductivitat complexa del model de dos fluids, la longitud de penetració de London i les forces que descriuen la dinàmica de vòrtexs en l’equació de balanç fenomenològic. Les limitacions tèrmiques de la sonda experimental han estat testades fent mesures del coeficient de reflexió en funció del camp magnètic continu a diferents valors de la potència de microones, per a valors fixos de temperatura.
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Shapoval, Tetyana. "Local imaging of magnetic flux in superconducting thin films". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-27206.
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Local studies of magnetic flux line (vortex) distribution in superconducting thin films and
their pinning by natural and artificial defects have been performed using low-temperature
magnetic force microscopy (LT-MFM).
Taken a 100 nm thin NbN film as an example, the depinning of vortices from natural
defects under the influence of the force that the MFM tip exerts on the individual vortex was
visualized and the local pinning force was estimated. The good agreement of these results with
global transport measurements demonstrates that MFM is a powerful and reliable method to
probe the local variation of the pinning landscape. Furthermore, it was demonstrated that the
presence of an ordered array of 1-μm-sized ferromagnetic permalloy dots being in a magneticvortex
state underneath the Nb film significantly influences the natural pinning landscape of
the superconductor leading to commensurate pinning effects. This strong pinning exceeds the
repulsive interaction between the superconducting vortices and allows vortex clusters to be
located at each dot. Additionally, for industrially applicable YBa$_2$Cu$_3$O$_{7-\delta} thin films the main
question discussed was the possibility of a direct correlation between vortices and artificial
defects as well as vortex imaging on rough as-prepared thin films. Since the surface roughness
(droplets, precipitates) causes a severe problem to the scanning MFM tip, a nanoscale wedge
polishing technique that allows to overcome this problem was developed. Mounting the sample
under a defined small angle results in a smooth surface and a monotonic thickness reduction
of the film along the length of the sample. It provides a continuous insight from the film
surface down to the substrate with surface sensitive scanning techniques.
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Shimozawa, Masaaki. "Superconducting properties of heavy fermion thin films and superlattices". 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188463.
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Dew, Steven K. "Preparation and characterization of high temperature superconducting thin films". Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27834.
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Thin films of the Bi₂Sr₂Ca₂Cu₃O[sub y] superconductor with T[sub c] in excess of 106K were produced through a two step process involving rf magnetron sputtering of an oxide target followed by annealing in oxygen. The effects of various production parameters on the deposition and quality of the films were studied.
During deposition, ion bombardment of the films directly in front of the sputtering target lead to an increase in film density and to resputtering. Films from this area tended to flake off of the substrate during processing. Heating the substrate during deposition reduced the flaking problem, but caused the concentration of bismuth to drop at temperatures above 350° C.
Optimal post-deposition processing conditions were dependent on several factors including film composition, lead doping, and oxygen concentration in the annealing atmosphere. After processing, only lead doped films resulted in significant amounts of 2223 and zero resistance T[sub c]'s above 100K. The optimal initial film composition was Pb[sub 1.1]Bi₂Sr₂Ca₂Cu₃O[sub y]. The best annealing conditions for such films were 865-875°C for 16 h in flowing oxygen.
During processing, films developed in a sequence of 2201, 2212, and, in lead doped films, 2223. The lead dopant was steadily lost during processing, and no detectable amounts remained in some of the best films after processing. Development of the 2223 phase stopped when the lead loss from the films was essentially complete.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Zhang, Ying Zi. "Magneto-electrical properties of Bi-2201 superconducting thin films". Doctoral thesis, Universite Libre de Bruxelles, 2000. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211752.
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Zhao, Yue. "Fabrication and characterization of superconducting PLD MgB2 thin films". Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060719.121046/index.html.
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Issa, Almoutaz. "Laser ablation, deposition of high temperature superconducting thin films". Thesis, University of Hull, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384805.
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Shapoval, Tetyana. "Local imaging of magnetic flux in superconducting thin films". Doctoral thesis, Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, 2009. https://tud.qucosa.de/id/qucosa%3A25239.
Pełny tekst źródłaStreszczenie:
Local studies of magnetic flux line (vortex) distribution in superconducting thin films and
their pinning by natural and artificial defects have been performed using low-temperature
magnetic force microscopy (LT-MFM).
Taken a 100 nm thin NbN film as an example, the depinning of vortices from natural
defects under the influence of the force that the MFM tip exerts on the individual vortex was
visualized and the local pinning force was estimated. The good agreement of these results with
global transport measurements demonstrates that MFM is a powerful and reliable method to
probe the local variation of the pinning landscape. Furthermore, it was demonstrated that the
presence of an ordered array of 1-μm-sized ferromagnetic permalloy dots being in a magneticvortex
state underneath the Nb film significantly influences the natural pinning landscape of
the superconductor leading to commensurate pinning effects. This strong pinning exceeds the
repulsive interaction between the superconducting vortices and allows vortex clusters to be
located at each dot. Additionally, for industrially applicable YBa$_2$Cu$_3$O$_{7-\delta} thin films the main
question discussed was the possibility of a direct correlation between vortices and artificial
defects as well as vortex imaging on rough as-prepared thin films. Since the surface roughness
(droplets, precipitates) causes a severe problem to the scanning MFM tip, a nanoscale wedge
polishing technique that allows to overcome this problem was developed. Mounting the sample
under a defined small angle results in a smooth surface and a monotonic thickness reduction
of the film along the length of the sample. It provides a continuous insight from the film
surface down to the substrate with surface sensitive scanning techniques.
43
Miranda, Felix Antonio. "Microwave response of high transition temperature superconducting thin films". Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055533862.
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Pullan, Penelope Anne. "Flux pinning in yttrium barium copper oxide superconducting thin films". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320038.
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Chern, Jin-Dong. "Optical and microwave responses of high temperature superconducting thin films". Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282502.
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Sakeek, Hazem Falah Hashem. "High Tâ†c superconducting thin films by laser ablation technique". Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334640.
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Campion, Richard. "An investigation into superconducting thin films : (103/013) oriented YBCO". Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262960.
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Scott, Kenneth. "The pulsed laser deposition of high temperature superconducting thin films". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240068.
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Vemulakonda, Padma Prasuna S. "Comparative Characterization of Superconducting Thin Films Fabricated by Different Techniques". Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1176576035.
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Tashiro, Hidenori. "Time-resolved infrared studies of superconducting molybdenum-germanium thin films". [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008001.
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