11B4C containing Ni/Ti neutron multilayer mirrors PDF Download
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Author: Sjoerd Broekhuijsen
Publisher: Linköping University Electronic Press
ISBN: 9179296645
Category :
Languages : en
Pages : 67
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Book Description
The work in this thesis covers the design, growth and characterisation of neutron multilayers. The performance of these multilayers is highly dependent on the obtained interface width between the layers, even a modest improvement can offer a substantial increase in reflectivity performance. As multilayers are such an integral component of many neutron optical instruments, any improvement in terms of reflectivity performance has broad implications for all neutron scattering experiments. This project has been carried out with the construction of the European Spallation Source (ESS) in mind, but the principles extend to all neutron scattering sources. Ni/Ti is the conventional material system of choice for neutron optical components due to the high contrast in scattering length density (SLD). The reflected intensity of such components is largely dependent on the interface width, caused by the formation of nanocrystallites, interdiffusion, and/or intermixing. Apart from hampering the reflectivity performance, the finite interface width between the layers also limits the minimum usable layer thickness in the mirror stack. The formation of nanocrystallites has been eliminated by co-depositing of B4C . This has been combined with a modulated ion assistance scheme to smoothen the interfaces. X-ray reflectivity (XRR) measurements show significantly improvements compared to pure Ni/Ti multilayers. This has further been investigated using low neutron-absorbing 11B4C instead. After deposition, the 11B4C containing films have been characterized using neutron reflectometry, X-ray reflectivity, transmission electron microscopy, elastic recoil detection analysis, X-ray photoelectron spectroscopy. A large part of his work has focused on fitting X-ray and neutron reflectivity measurements in order to obtain structural parameters. The fits to the experimental data suggest a significant improvement in interface width for the samples that have been co-deposited with 11B4C using a modulated ion assistance scheme during deposition. Any accumulation of roughness has been eliminated, and the average initial interface width at the first bilayer has been reduced from 6.3 Å to 4.5 Å per bilayer. The respective reflectivity performance for these structural parameters have been simulated for a neutron supermirror (N = 5000) for both materials at a neutron wavelength at λ = 3 Å using the IMD software. The predicted reflectivity performance for the 11B4C containing samples amounts to about 71%, which is a significant increase compared to the pure Ni/Ti samples which have a predicted reflectivity of 62%. This results in a reflectivity increase from 0.84% to 3.3% after a total of 10 reflections, resulting in more than 400% higher neutron flux at experiment.
Author: Sjoerd Broekhuijsen
Publisher: Linköping University Electronic Press
ISBN: 9179296645
Category :
Languages : en
Pages : 67
Get Book Here
Book Description
The work in this thesis covers the design, growth and characterisation of neutron multilayers. The performance of these multilayers is highly dependent on the obtained interface width between the layers, even a modest improvement can offer a substantial increase in reflectivity performance. As multilayers are such an integral component of many neutron optical instruments, any improvement in terms of reflectivity performance has broad implications for all neutron scattering experiments. This project has been carried out with the construction of the European Spallation Source (ESS) in mind, but the principles extend to all neutron scattering sources. Ni/Ti is the conventional material system of choice for neutron optical components due to the high contrast in scattering length density (SLD). The reflected intensity of such components is largely dependent on the interface width, caused by the formation of nanocrystallites, interdiffusion, and/or intermixing. Apart from hampering the reflectivity performance, the finite interface width between the layers also limits the minimum usable layer thickness in the mirror stack. The formation of nanocrystallites has been eliminated by co-depositing of B4C . This has been combined with a modulated ion assistance scheme to smoothen the interfaces. X-ray reflectivity (XRR) measurements show significantly improvements compared to pure Ni/Ti multilayers. This has further been investigated using low neutron-absorbing 11B4C instead. After deposition, the 11B4C containing films have been characterized using neutron reflectometry, X-ray reflectivity, transmission electron microscopy, elastic recoil detection analysis, X-ray photoelectron spectroscopy. A large part of his work has focused on fitting X-ray and neutron reflectivity measurements in order to obtain structural parameters. The fits to the experimental data suggest a significant improvement in interface width for the samples that have been co-deposited with 11B4C using a modulated ion assistance scheme during deposition. Any accumulation of roughness has been eliminated, and the average initial interface width at the first bilayer has been reduced from 6.3 Å to 4.5 Å per bilayer. The respective reflectivity performance for these structural parameters have been simulated for a neutron supermirror (N = 5000) for both materials at a neutron wavelength at λ = 3 Å using the IMD software. The predicted reflectivity performance for the 11B4C containing samples amounts to about 71%, which is a significant increase compared to the pure Ni/Ti samples which have a predicted reflectivity of 62%. This results in a reflectivity increase from 0.84% to 3.3% after a total of 10 reflections, resulting in more than 400% higher neutron flux at experiment.
Author: Matthew Pelliccione
Publisher: Springer Science & Business Media
ISBN: 0387751092
Category : Technology & Engineering
Languages : en
Pages : 206
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Book Description
The focus of this book is on modeling and simulations used in research on the morphological evolution during film growth. The authors emphasize the detailed mathematical formulation of the problem. The book will enable readers themselves to set up a computational program to investigate specific topics of interest in thin film deposition. It will benefit those working in any discipline that requires an understanding of thin film growth processes.
Author: Michael Baake
Publisher: Cambridge University Press
ISBN: 1108514499
Category : Mathematics
Languages : en
Pages : 408
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Book Description
Quasicrystals are non-periodic solids that were discovered in 1982 by Dan Shechtman, Nobel Prize Laureate in Chemistry 2011. The mathematics that underlies this discovery or that proceeded from it, known as the theory of Aperiodic Order, is the subject of this comprehensive multi-volume series. This second volume begins to develop the theory in more depth. A collection of leading experts, among them Robert V. Moody, cover various aspects of crystallography, generalising appropriately from the classical case to the setting of aperiodically ordered structures. A strong focus is placed upon almost periodicity, a central concept of crystallography that captures the coherent repetition of local motifs or patterns, and its close links to Fourier analysis. The book opens with a foreword by Jeffrey C. Lagarias on the wider mathematical perspective and closes with an epilogue on the emergence of quasicrystals, written by Peter Kramer, one of the founders of the field.
Author: Marius Rodner
Publisher: Linköping University Electronic Press
ISBN: 9179296750
Category :
Languages : sv
Pages : 104
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Book Description
The work presented in this thesis focuses on epitaxial graphene on SiC as a platform for air quality sensors. Several approaches have been tested and evaluated to increase the sensitivity, selectivity, speed of response and stability of the sensors. The graphene surfaces have been functionalized, for example, with different metal oxide nanoparticles and nanolayers using hollow-cathode sputtering and pulsed laser deposition. The modified surfaces were investigated towards topography, integrity and chemical composition with characterization methods such as atomic force microscopy and Raman spectroscopy. Interaction energies between several analytes and nanoparticle-graphene-combinations were calculated by density functional theory to find the optimal material for specific target gases, and to verify the usefulness of this approach. The impact of environmental influences such as operating temperature, relative humidity and UV irradiation on sensing properties was investigated as well. To further enhance sensor performances, the first-order time-derivative of the sensor’s resistance was introduced to speed up sensor response and a temperature cycled operation mode was investigated towards selectivity. Applying these methods in laboratory conditions, sensors with a quantitative readout of single ppb benzene and formaldehyde were developed. These results show promise to fill the existing gap of low-cost but highly sensitive and fast gas sensors for air quality monitoring. Der Fokus dieser Thesis liegt auf der Erforschung von epitaxialem Graphen auf SiC als Plattform für Luftgütesensoren. Diverse Ansätze wurden untersucht, um die Sensitivität, Selektivität, Reaktionsgeschwindigkeit und Stabilität der Sensoren zu verbessern. Die Graphenoberfläche wurde unter anderem mit Metalloxid-Nanopartikeln oder nanometerdünnen Schichten funktionalisiert. Die funktionalisierten Sensorschichten wurden hinsichtlich ihrer Oberflächenbeschaffenheit, Unversehrtheit und chemischen Zusammensetzung mittels Rasterkraftmikroskopie und Raman Spektroskopie untersucht. Die Reaktionsenergien zwischen verschiedenen Analyten und Nanopartikel-Graphen-Kombinationen wurden mit Dichtefunktionaltheorie berechnet, um das optimale Material für spezifische Gase zu finden und um die Brauchbarkeit dieser Funktionalisierungsmethode zu verifizieren. Der Einfluss von äußeren Parametern wie Sensortemperatur, Luftfeuchte und UV-Einstrahlung auf die Sensoreigenschaften wurde ebenfalls untersucht. Um die Sensorleistung zu verbessern, wurde die erste zeitliche Ableitung des Sensorwiderstands als zusätzliches Signal eingeführt und ein temperaturzyklischer Betriebsmodus hinsichtlich seiner Eignung erforscht. Durch die Anwendung dieser Methoden ist es möglich, einzelne ppbs Benzol und Formaldehyd unter Laborbedingungen zu detektieren. Diese Ergebnisse sind vielversprechend, um die bestehende Lücke der günstigen, aber sehr sensitiven Sensoren für Luftqualitätsüberwachung zu schließen. Arbetet som presenteras i denna avhandling fokuserar på epitaxiell grafen på SiC som en plattform för luftkvalitetssensorer. Flera tillvägagångssätt har testats och utvärderats för att öka känsligheten, selektiviteten, responstiden, och stabiliteten hos sensorerna. Grafenytorna har modifierats till exempel med olika metalloxid-nanopartiklar och nanolager med användning av hålkatodsputtring och PLD. De modifierade ytorna undersöktes mot topografi, strukturell integritet och kemisk sammansättning med karakteriseringsmetoder som atomkraftsmikroskopi och Ramanspektroskopi. Interaktionsenergier mellan flera analyter och nanopartiklar-grafen- materialkombinationer beräknades med täthetsfunktionalteori för att hitta de optimala materialkombinationerna för specifika målgaser och för att verifiera användbarheten av ytmodifieringarna. Effekten av externa faktorer som arbetstemperatur, relativ fuktighet och UV-bestrålning på avkänningsegenskaper undersöktes också. För att ytterligare förbättra sensorprestanda introducerades första ordningens tidsderivat av sensorns resistans för att snabbare utvärdera sensorns respons, och ett temperaturcyklat driftläge i kombination med multivariat dataanalys undersöktes mot selektivitet. Genom att använda dessa metoder under laboratorieförhållanden utvecklades sensorer med en kvantitativ avläsning av enstaka ppb bensen och formaldehyd. Dessa resultat visar på en möjlig lösning för att fylla det hålrum som finns i dagens sensorteknologier för luftkvalitetsövervakning, där flera relevanta gaser i dagsläget inte kan mätas med kostnadseffektiva men mycket känsliga och snabba gassensorer.
Author:
Publisher: Academic Press
ISBN: 008054293X
Category : Science
Languages : en
Pages : 268
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Book Description
This volume provides the first comprehensive look at a pivotal new technology in integrated circuit fabrication. For some time researchers have sought alternate processes for interconnecting the millions of transistors on each chip because conventional physical vapor deposition can no longer meet the specifications of today's complex integrated circuits. Out of this research, ionized physical vapor deposition has emerged as a premier technology for the deposition of thin metal films that form the dense interconnect wiring on state-of-the-art microprocessors and memory chips.For the first time, the most recent developments in thin film deposition using ionized physical vapor deposition (I-PVD) are presented in a single coherent source. Readers will find detailed descriptions of relevant plasma source technology, specific deposition systems, and process recipes. The tools and processes covered include DC hollow cathode magnetrons, RF inductively coupled plasmas, and microwave plasmas that are used for depositing technologically important materials such as copper, tantalum, titanium, TiN, and aluminum. In addition, this volume describes the important physical processes that occur in I-PVD in a simple and concise way. The physical descriptions are followed by experimentally-verified numerical models that provide in-depth insight into the design and operation I-PVD tools.Practicing process engineers, research and development scientists, and students will find that this book's integration of tool design, process development, and fundamental physical models make it an indispensable reference.Key Features:The first comprehensive volume on ionized physical vapor depositionCombines tool design, process development, and fundamental physical understanding to form a complete picture of I-PVDEmphasizes practical applications in the area of IC fabrication and interconnect technologyServes as a guide to select the most appropriate technology for any deposition application*This single source saves time and effort by including comprehensive information at one's finger tips*The integration of tool design, process development, and fundamental physics allows the reader to quickly understand all of the issues important to I-PVD*The numerous practical applications assist the working engineer to select and refine thin film processes
Author: Daniel Lundin
Publisher: Elsevier
ISBN: 0128124547
Category : Technology & Engineering
Languages : en
Pages : 398
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Book Description
High Power Impulse Magnetron Sputtering: Fundamentals, Technologies, Challenges and Applications is an in-depth introduction to HiPIMS that emphasizes how this novel sputtering technique differs from conventional magnetron processes in terms of both discharge physics and the resulting thin film characteristics. Ionization of sputtered atoms is discussed in detail for various target materials. In addition, the role of self-sputtering, secondary electron emission and the importance of controlling the process gas dynamics, both inert and reactive gases, are examined in detail with an aim to generate stable HiPIMS processes. Lastly, the book also looks at how to characterize the HiPIMS discharge, including essential diagnostic equipment. Experimental results and simulations based on industrially relevant material systems are used to illustrate mechanisms controlling nucleation kinetics, column formation and microstructure evolution.
Author: Jorg Zegenhagen
Publisher: World Scientific
ISBN: 9814513105
Category : Science
Languages : en
Pages : 557
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Book Description
The X-ray standing wave (XSW) technique is an X-ray interferometric method combining diffraction with a multitude of spectroscopic techniques. It is extremely powerful for obtaining information about virtually all properties of surfaces and interfaces on the atomic scale. However, as with any other technique, it has strengths and limitations. The proper use and necessary understanding of this method requires knowledge in quite different fields of physics and technology. This volume presents comprehensively the theoretical background, technical requirements and distinguished experimental highlights of the technique. Containing contributions from the most prominent experts of the technique, such as Andre Authier, Boris Batterman, Michael J Bedzyk, Jene Golovchenko, Victor Kohn, Michail Kovalchuk, Gerhard Materlik and D Phil Woodruff, the book equips scientists with all the necessary information and knowledge to understand and use the XSW technique in practically all applications.
