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Enhanced Laser Ion Acceleration from SolidsKluge, Thomas 06 November 2012 (has links)
This thesis presents results on the theoretical description of ion acceleration using ultra-short ultra-intense laser pulses. It consists of two parts. One deals with the very general and underlying description and theoretic modeling of the laser interaction with the plasma, the other part presents three approaches of optimizing the ion acceleration by target geometry improvements using the results of the first part. In the first part, a novel approach of modeling the electron average energy of an over-critical plasma that is irradiated by a few tens of femtoseconds laser pulse with relativistic intensity is introduced.
The first step is the derivation of a general expression of the distribution of accelerated electrons in the laboratory time frame. As is shown, the distribution is homogeneous in the proper time of the accelerated electrons, provided they are at rest and distributed uniformly initially. The average hot electron energy can then be derived in a second step from a weighted average of the single electron energy evolution. This result is applied exemplary for the two important cases of infinite laser contrast and square laser temporal profile, and the case of an experimentally more realistic case of a laser pulse with a temporal profile sufficient to produce a preplasma profile with a scale length of a few hundred nanometers prior to the laser pulse peak. The thus derived electron temperatures are in excellent agreement with recent measurements and simulations, and in particular provide an analytic explanation for the reduced temperatures seen both in experiments and simulations compared to the widely used ponderomotive energy scaling.
The implications of this new electron temperature scaling on the ion acceleration, i.e. the maximum proton energy, are then briefly studied in the frame of an isothermal 1D expansion model. Based on this model, two distinct regions of laser pulse duration are identified with respect to the maximum energy scaling. For short laser pulses, compared to a reference time, the maximum ion energy is found to scale linearly with the laser intensity for a simple flat foil, and the most important other parameter is the laser absorption efficiency. In particular the electron temperature is of minor importance. For long laser pulse durations the maximum ion energy scales only proportional to the square root of the laser peak intensity and the electron temperature has a large impact. Consequently, improvements of the ion acceleration beyond the simple flat foil target maximum energies should focus on the increase of the laser absorption in the first case and the increase of the hot electron temperature in the latter case.
In the second part, exemplary geometric designs are studied by means of simulations and analytic discussions with respect to their capability for an improvement of the laser absorption efficiency and temperature increase. First, a stack of several foils spaced by a few hundred nanometers is proposed and it is shown that the laser energy absorption for short pulses and therefore the maximum proton energy can be significantly increased. Secondly, mass limited targets, i.e. thin foils with a finite lateral extension, are studied with respect to the increase of the hot electron temperature. An analytical model is provided predicting this temperature based on the lateral foil width. Finally, the important case of bent foils with attached flat top is analyzed. This target geometry resembles hollow cone targets with flat top attached to the tip, as were used in a recent experiment producing world record proton energies. The presented analysis explains the observed increase in proton energy with a new electron acceleration mechanism, the direct acceleration of surface confined electrons by the laser light. This mechanism occurs when the laser is aligned tangentially to the curved cone wall and the laser phase co-moves with the energetic electrons. The resulting electron average energy can exceed the energies from normal or oblique laser incidence by several times. Proton energies are therefore also greatly increased and show a theoretical scaling proportional to the laser intensity, even for long laser pulses.
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Systém pro podporu výuky dynamických datových struktur / System for Support of Dynamic Data Structures LearningTrávníček, Jiří Unknown Date (has links)
The main objective of this work is to design and implement an application that can be used as an aid for the education of programming essentials. Particularly, the attention focuses on the domain of dynamic data structures. The target application will be implemented with the use of web technologies so that it can be run in an ordinary WWW browser. First of all, a brief introduction recapitulates the data structures to be covered. Then the work summarizes the usable technologies available within the web browsers with the focus on the particular technology (which is DHTML) that will become the target platform. The most significant part of this work then discusses the design of the final application. This rather theoretical part is then followed by the description of the practical implementation. A short user manual is also included.
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Zabezpečení bezdrátových senzorových sítí / Wireless Sensor Networks SecurityNagy, Jan January 2007 (has links)
This thesis deals with the security of wireless sensor networks, mainly of the industrial standard ZigBee. The aim of the work is to familiarize with the 802.15.4 standard and the ZigBee technology, especially with present methods of security in this field. I have also analysed the requirements for the security of this technology. Further aim of this work is the introduction of the ZigBee kit and description of the Microchip's ZigBee stack. Analysis of the stack is connected with practical test of security functions in the ZigBee laboratory.
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The applicability and scalability of probabilistic inference in deep-learning-assisted geophysical inversion applicationsIzzatullah, Muhammad 04 1900 (has links)
Probabilistic inference, especially in the Bayesian framework, is a foundation for quantifying uncertainties in geophysical inversion applications. However, due to the presence of high-dimensional datasets and the large-scale nature of geophysical inverse problems, the applicability and scalability of probabilistic inference face significant challenges for such applications. This thesis is dedicated to improving the probabilistic inference algorithms' scalability and demonstrating their applicability for large-scale geophysical inversion applications. In this thesis, I delve into three leading applied approaches in computing the Bayesian posterior distribution in geophysical inversion applications: Laplace's approximation, Markov chain Monte Carlo (MCMC), and variational Bayesian inference.
The first approach, Laplace's approximation, is the simplest form of approximation for intractable Bayesian posteriors. However, its accuracy relies on the estimation of the posterior covariance matrix. I study the visualization of the misfit landscape in low-dimensional subspace and the low-rank approximations of the covariance for full waveform inversion (FWI). I demonstrate that a non-optimal Hessian's eigenvalues truncation for the low-rank approximation will affect the approximation accuracy of the standard deviation, leading to a biased statistical conclusion. Furthermore, I also demonstrate the propagation of uncertainties within the Bayesian physics-informed neural networks for hypocenter localization applications through this approach.
For the MCMC approach, I develop approximate Langevin MCMC algorithms that provide fast sampling at efficient computational costs for large-scale Bayesian FWI; however, this inflates the variance due to asymptotic bias. To account for this asymptotic bias and assess their sample quality, I introduce the kernelized Stein discrepancy (KSD) as a diagnostic tool. When larger computational resources are available, exact MCMC algorithms (i.e., with a Metropolis-Hastings criterion) should be favored for an accurate posterior distribution statistical analysis.
For the variational Bayesian inference, I propose a regularized variational inference framework that performs posterior inference by implicitly regularizing the Kullback-Leibler divergence loss with a deep denoiser through a Plug-and-Play method. I also developed Plug-and-Play Stein Variational Gradient Descent (PnP-SVGD), a novel algorithm to sample the regularized posterior distribution. The PnP-SVGD demonstrates its ability to produce high-resolution, trustworthy samples representative of the subsurface structures for a post-stack seismic inversion application.
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A Hardware/Software Stack for Heterogeneous SystemsLehner, Wolfgang, Castrillon, Jeronimo, Lieber, Matthias, Klüppelholz, Sascha, Völp, Marcus, Asmussen, Nils, Aßmann, Uwe, Baader, Franz, Baier, Christel, Fettweis, Gerhard, Fröhlich, Jochen, Goens, Andrés, Haas, Sebastian, Habich, Dirk, Härtig, Hermann, Hasler, Mattis, Huismann, Immo, Karnagel, Tomas, Karol, Sven, Kumar, Akash, Leuschner, Linda, Ling, Siqi, Märcker, Steffen, Menard, Christian, Mey, Johannes, Nagel, Wolfgang, Nöthen, Benedikt, Peñaloza, Rafael, Raitza, Michael, Stiller, Jörg, Ungethüm, Annett, Voigt, Axel, Wunderlich, Sascha 17 July 2023 (has links)
Plenty of novel emerging technologies are being proposed and evaluated today, mostly at the device and circuit levels. It is unclear what the impact of different new technologies at the system level will be. What is clear, however, is that new technologies will make their way into systems and will increase the already high complexity of heterogeneous parallel computing platforms, making it ever so difficult to program them. This paper discusses a programming stack for heterogeneous systems that combines and adapts well-understood principles from different areas, including capability-based operating systems, adaptive application runtimes, dataflow programming models, and model checking. We argue why we think that these principles built into the stack and the interfaces among the layers will also be applicable to future systems that integrate heterogeneous technologies. The programming stack is evaluated on a tiled heterogeneous multicore.
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Accelerated Testing of the End-plate Assembly of a Redox Flow BatteryJindal, Saksham January 2022 (has links)
As the world transitions to intermittent renewable energy sources like solar and wind, the need for long-duration energy storage technologies is becoming more and more prominent. In this regard, flow batteries are seen as a promising solution, owing to their inherent advantages like decoupling of power and energy, extremely high cycle life and negligible self-discharge. However, there are multiple engineering challenges to overcome before the widespread application of flow batteries. This study, carried out at a leading manufacturer of vanadium-based flow batteries, VoltStorage GmbH, addresses one of those challenges related to the hydraulic sealing of the endplate assembly of the battery. The endplate assembly is prone to losing its structural integrity over the continuous operation, thus failing to achieve its intended purpose of hydraulic sealing. Additionally, it is susceptible to enhanced contact resistance during operation, thus harming the battery performance. Therefore, the primary objective of this study was to develop a modular test rig that could evaluate the endplate assembly's performance in an accelerated manner but without using electrolytes to eliminate the complications of dealing with the sulfuric acid solution (i.e. electrolyte). So, air was chosen as the working fluid to offer clean and highly repeatable testing. The study began with a literature review of the flow batteries. It was found that the literature concerning the engineering aspects of a flow battery was limited. Therefore, it was followed by an in-depth analysis of the stack design of VoltStorage and the engineering challenges linked to the endplate assembly. Importantly, the root cause of the problem of hydraulic sealing was identified, which was the pressure cycling of the monopole. After that, the test rig was designed and developed based on the understanding of the engineering challenge and to realize the objective of a modular design. The design modularity was desirable to test multiple assemblies simultaneously without increasing the floor footprint. Three parameters were chosen to characterize the assembly: monopole deflection, internal resistance and air leak rate. Due to the system's complexity, experiments to monitor these parameters were divided into two phases, i.e., rig qualification and full-scale testing. The first phase aimed to characterize their baseline behaviour and evaluate the rig's robustness; the next phase aimed at monitoring their behaviour evolution with continuous operation. The monopole deflection measurements during the first phase indicated a maximum deflection of 0.3 mm. The air-electrolyte equivalence was also established by making the deflection behaviour similar during air and electrolyte operation. Much higher pressure had to be applied with air (~1.6 bar gauge) than water (~0.8 bar gauge) to achieve this equivalence. Moreover, the internal resistance and air leak rate measurements conducted during the first phase provided baseline values (6.341 ± 0.731 mΩ and 1.241 ± 0.091 Pa∙l/s, respectively, with a 95% confidence level) against which any change during continuous operation could be differentiated. However, the full-scale testing could not be performed due to the global supply chain disruptions and the limited time frame of the project. Nevertheless, a vital objective of the design, to modularize the rig so that it could be scaled up quickly and test multiple assemblies simultaneously to facilitate the rapid prototyping of different designs, was realized in the project. Flow batteries are a promising technology for long-duration energy storage, although there are some challenges to overcome. In addition, to be defined as a truly sustainable solution, the problems linked with vanadium mining and the high capital costs of the system have to be eliminated. With the rapidly expanding development and deployment of these systems, it is expected that they will be an essential part of our future grids. To conclude, in this project, a testing system was developed which could perform a dry mechanical and electrical integrity check of the endplate assembly of a flow battery in an accelerated manner. The system could prove to be vital in enhancing the reliability of stack-based systems and hence foster their widespread applicability. The future work that can benefit this system is assembling the set of 5 short stacks and performing a continuous operation to monitor the behaviour evolution of the stacks. This step would help assess the testing system's shortcomings and subsequently make the required modifications. / I takt med att världen övergår till intermittenta förnybara energikällor som sol- och vindkraft blir behovet av teknik för energilagring med lång varaktighet alltmer framträdande. Flödesbatterier ses i detta avseende som en lovande lösning på grund av deras inneboende fördelar, t.ex. frikoppling av kraft och energi, extremt lång livslängd och försumbar självurladdning. Det finns dock flera tekniska utmaningar som måste övervinnas innan flödesbatterier kan användas på bred front. Den här studien, som utfördes hos VoltStorage GmbH, en ledande tillverkare av vanadiumbaserade flödesbatterier, tar upp en av dessa utmaningar som rör den hydrauliska tätningen av batteriets ändplatta. Ändtplattan är benägen att förlora sin strukturella integritet under kontinuerlig drift, vilket innebär att den inte uppnår sitt avsedda syfte, nämligen hydraulisk tätning. Dessutom är den känslig för ökat kontaktmotstånd under drift, vilket skadar batteriets prestanda. Det primära målet med denna studie var därför att utveckla en modulär testrigg som kan utvärdera ändplattans prestanda på ett påskyndat sätt, men utan att använda elektrolyter för att eliminera komplikationerna med att hantera svavelsyralösningen (dvs. elektrolyten). Därför valdes luft som arbetsvätska för att erbjuda rena och mycket repeterbara tester. Studien inleddes med en litteraturgenomgång av flödesbatterier. Det konstaterades att litteraturen om de tekniska aspekterna av ett flödesbatteri var begränsad. Därför följdes den av en djupgående analys av VoltStorages stapelkonstruktion och de tekniska utmaningarna i samband med ändplattans montering. Det var viktigt att identifiera grundorsaken till problemet med hydraulisk tätning, vilket var tryckcykling av monopolen. Därefter utformades och utvecklades testriggen utifrån förståelsen av den tekniska utmaningen och för att förverkliga målet med en modulär konstruktion. Modulariteten i konstruktionen var önskvärd för att testa flera enheter samtidigt utan att öka golvytan. Tre parametrar valdes ut för att karakterisera enheten: monopolens avböjning, inre motstånd och luftläckagehastighet. På grund av systemets komplexitet delades experimenten för att övervaka dessa parametrar upp i två faser, dvs. kvalificering av riggen och provning i full skala. Den första fasen syftade till att karakterisera deras grundbeteende och utvärdera riggens robusthet, medan nästa fas syftade till att övervaka deras funktionella respons utveckling vid kontinuerlig drift. Mätningarna av monopolens nedböjning under den första fasen visade på en maximal nedböjning på 0,3 mm. Likvärdigheten mellan luft och elektrolyt fastställdes också genom att utböjningsbeteendet var likartat under drift med luft och elektrolyt. Ett mycket högre tryck måste tillämpas med luft (~1,6 bar gauge) än med vatten (~0,8 bar gauge) för att uppnå denna likvärdighet. Dessutom gav de mätningar av det inre motståndet och luftläckaget som utfördes under den första fasen basvärden (6,341 ± 0,731 mΩ respektive 1,241 ± 0,091 Pa∙l/s, med en konfidensnivå på 95 %) mot vilka eventuella förändringar under kontinuerlig drift kunde särskiljas. Den fullskaliga testningen kunde dock inte genomföras på grund av störningar i den globala leveranskedjan och projektets begränsade tidsram. Ett viktigt mål med konstruktionen, att modularisera riggen så att den snabbt kan skalas upp och testa flera enheter samtidigt för att underlätta snabb prototypframställning av olika konstruktioner, förverkligades dock i projektet. Flödesbatterier är en lovande teknik för energilagring under lång tid, även om det finns vissa utmaningar att övervinna. För att kunna definieras som en verkligt hållbar lösning måste dessutom de problem som är kopplade till vanadinbrytning och systemets höga kapitalkostnader undanröjas. Med den snabbt ökande utvecklingen och spridningen av dessa system förväntas de bli en viktig del av våra framtida nät. Sammanfattningsvis utvecklades i detta projekt ett testsystem som kan utföra en torr mekanisk och elektrisk integritetskontroll av ändplattan i ett flödesbatteri på ett påskyndat sätt. Systemet kan visa sig vara avgörande för att öka tillförlitligheten hos stapelbaserade system och därmed främja deras utbredda användbarhet. Det framtida arbete som kan gynna detta system är att montera en uppsättning av fem korta staplar och utföra en kontinuerlig operation för att övervaka staplarnas funktionella responsutveckling. Detta steg skulle hjälpa till att bedöma testsystemets brister och därefter göra de ändringar som krävs.
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Optical coupling effects between plasmon resonances in disordered metal nanostructures and a nanocavityÖqvist, Elin January 2024 (has links)
Ultra-thin solar cells that incorporate earth-abundant and non-toxic materials are promising candidates in the endeavor toward sustainable energy harvesting. Methods to counteract the inevitable low absorption of thinner semiconductor layers are of high interest and have raised considerable attention in the research society. In an attempt to increase the absorption of these types of assemblies, optical coupling effects between the localized surface plasmon resonances (LSPR) of disordered Au nanostructures and a Fabry-Pérot cavity were studied using a previously established absorber/spacer/reflector stack. The disordered Au array was fabricated by evaporating a thin Au film on a substrate with a 55 nm SiO2 dielectric spacer and a 100 nm Al reflecting film, followed by thermal annealing. Nominal Au film thicknesses in the range of 5-25 Å and annealing temperatures of 200-500 oC were investigated. In situ spectroscopic ellipsometry measurements during the subsequent atomic layer deposition (ALD) of tin monosulfide (SnS) allowed analysis of how the optical properties of the SnS/Au absorber layer changed as a function of the growing SnS layer thickness. By employing the Transfer Matrix Method with the estimated optical properties from the in situ analysis, the absorptance of the absorber/spacer/reflector stacks was simulated as a function of the spacer thickness, revealing any signs of the characteristic anti-crossing behavior. It was discovered that a nominal Au film thickness of 25 Å, annealed at 450 oC, and coated with a SnS film of ∼13 nm primed toward the π-phase, resulted in strong optical coupling between the cavity mode and the LSPR. The energy difference at the avoided crossing in the specular reflectance measurement gave an estimated Rabi-splitting energy of 537 meV. This corresponded to about 40% of the original LSPR energy, placing itself within the ultra-strong coupling regime. To evaluate the relevance of the thin-layered structure in photovoltaic applications, more advanced computational methods are required to estimate the useful absorption that occurs in the SnS layer. Nevertheless, these results elucidate the realization of strong optical coupling effects between disordered Au nanostructures and a Fabry-Pérot cavity, and further the possibility of using scalable fabrication methods for this type of ultra-thin absorber/spacer/reflector stack.
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High-k Dielectrics For Metal-Insulator-Metal CapacitorsRevathy, P 07 1900 (has links) (PDF)
Metal-insulator-metal (MIM) capacitors are used for analog, RF, and DRAM applications in ICs. The International Technology Roadmap for Semiconductors (ITRS) specifies continuing increase in capacitance density (> 7 fF/ m2), lower leakage current density (< 10 8 A/cm2), very low effective oxide thickness (EOT < 1 nm, for DRAM applications), and better capacitance density-voltage (C-V) linearity ( < 100 ppm/V2, for analog/RF applications). In addition, the maximum fabrication/processing temper-ature should not be greater than 400 0C, in order to be compatible with the thermal budget of back-end fabrication steps. Low dielectric constants of conventional SiO2 and Si3N4 capacitors limit the capacitance densities of these devices. Although scaling down of dielectric thickness increases the capacitance density, it results in large leakage current density and poor C-V linearity.
In this work, the effects of high-k materials (Eu2O3, Gd2O3, TiO2) on the device performance of MIM capacitors are studied. The performance of multi-dielectric stack, and doped-dielectric stack devices are also investigated. The effects of anneal temperature, anneal ambient, anneal mode, and dielectric thickness on device performance are evaluated. C-V, current density-voltage (J-V), and reliability measurements are performed to benchmark the electrical performance, and this is correlated to the structural and material properties of the films through ellipsometry, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) measurements.
High-performance MIM capacitors are fabricated by using (RF sputtered) Eu2O3 dielectric. The fabricated devices are subjected to different anneal conditions, to study their device performance. Forming gas (FG) and argon (Ar) annealed devices are shown to have higher capacitance densities (7 fF/ m2jF G), lower leakage current densities (3.2 10 8 A/cm2jAr at -1 V), and higher , compared to oxygen (O2) annealed de-vices ( 100kHz = 193 ppm/V2jO2). The electrical characterization results are correlated with the surface chemical states of the films through XPS measurements. The annealing ambient is shown to alter the surface chemical states, which, in turn, modulate the electrical characteristics.
High-density MIM capacitors are fabricated by using (RF sputtered) Gd2O3, and Gd2O3-Eu2O3 stacked dielectrics. The fabricated Gd2O3 capacitors are also subjected to different anneal conditions, to study their device performance. Although Gd2O3 capacitors provide high capacitance density (15 fF/ m2), they suffer from high leakage current density, high , and poor reliability. Therefore, stacked dielectrics of Gd2O3 and Eu2O3
(Gd2O3/Eu2O3 and Eu2O3/Gd2O3) are fabricated to reduce leakage current density, improve , and improve reliability, with only a marginal reduction in capacitance density, compared to Gd2O3 capacitors. Density of defects and barrier/trap heights are extracted for the fabricated capacitors, and correlated with the device characteristics.
High-performance MIM capacitors with bilayer dielectric stacks of (ALD-deposited) TiO2-ZrO2, and Si-doped ZrO2 are characterized. Devices with (ALD-deposited) TiO2/ ZrO2/TiO2 (TZT) and AlO-doped TZT stacks are also characterized. The influence of doping on the device performance is studied. The surface chemical states of the deposited films are analyzed by high-resolution XPS. The structural analysis of the samples is performed by XRD measurements, and this is correlated to the electrical characteristics of the devices. Reliability measurements are performed to study the effects of constant voltage and current stress on device performance. High capacitance density (> 45 fF/ m2), low leakage current density (< 5 10 8 A/cm2 at -1 V, for most devices), and sub-nm EOT are achieved. These parameters exceed the ITRS specifications for DRAM storage capacitors.
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Kan projekt med öppen källkod användas delvis eller helt för at tuppfylla behoven för routing-applikationer? / Could open source projects be used partly or completely to fulfill the needs for routing-applications?Adugna, Leykun, Laic, Goran January 2020 (has links)
I dagens samhälle är det inte ovanligt för företag och organisationer att hitta bättre och alternativa mjukvaror med öppen källkod för att lösa sina behov. De söker programvaror som har de nödvändiga egenskaperna som krävs för att driva sin verksamhet och eventuellt ersätta egenutvecklad programvara för att spara tid och undvika onödiga kostnader. Denna avhandling har undersökt företagens behov av routing-applikationer och tagit fram ett förslag med hjälp av egenutvecklad testbädd. Den egenutvecklade testbädden kan användas av företag för att avgöra om den önskade öppen källkod programvara är lönsamt att implementera i ens verksamhet. Den routing-applikation som visade sig vara bättre än den befintliga är FRRouting(Free Range Routing). Lösningen som föreslås av studien har givit bevisad effekt genom ett pilotprojekt där öppen källkod har varit framgångsrikt på ett kvalitetsmässigt, funktionellt och kostnadseffektivt sätt att ersätta en befintlig programvara / Companies are looking into the open source community in the hope of finding a better alternative software to replace their existing software suit. They are looking for software that has the necessary properties required to run their business and possibly help them avoid unnecessary costs and save time. This thesis has examined the needs of routing application for companies and presented a suggestion by using self-developed testbed. The testbed can be used by companies to decide the beneficial of implementing the desired routing application software. The routing application that gave the best result in this study is FRRouting (Free Range Routing). The solution proposed by the study has been proven to be effective through a pilot project where open source program has been successful by retaining the expected quality, functionality in a cost-effective way.
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Evaluation of novel metalorganic precursors for atomic layer deposition of Nickel-based thin films / Evaluierung neuartiger metallorganischen Präkursoren für Atomlagenabscheidung von Nickel-basierten DünnschichtenSharma, Varun 04 June 2015 (has links) (PDF)
Nickel und Nickel (II) -oxid werden in großem Umfang in fortgeschrittenen elektronischen Geräten verwendet. In der Mikroelektronik-Industrie wird Nickel verwendet werden, um Nickelsilizid bilden. Die Nickelmono Silizid (NiSi) wurde als ausgezeichnetes Material für Source-Drain-Kontaktanwendungen unter 45 nm-CMOS-Technologie entwickelt. Im Vergleich zu anderen Siliziden für die Kontaktanwendungen verwendet wird NiSi wegen seines niedrigen spezifischen Widerstand, niedrigen Kontaktwiderstand, relativ niedrigen Bildungstemperatur und niedrigem Siliziumverbrauchs bevorzugt. Nickel in Nickelbasis-Akkus und ferromagnetischen Direktzugriffsspeicher (RAMs) verwendet. Nickel (II) oxid wird als Transistor-Gate-Oxid und Oxid in resistive RAM genutzt wird.
Atomic Layer Deposition (ALD) ist eine spezielle Art der Chemical Vapor Deposition (CVD), das verwendet wird, um sehr glatte sowie homogene Dünnfilme mit hervorragenden Treue auch bei hohen Seitenverhältnissen abzuscheiden. Es basiert auf selbstabschließenden sequentielle Gas-Feststoff-Reaktionen, die eine präzise Steuerung der Filmdicke auf wenige Angström lassen sich auf der Basis. Zur Herstellung der heutigen 3D-elektronische Geräte, sind Technologien wie ALD erforderlich. Trotz der Vielzahl von praktischen Anwendungen von Nickel und Nickel (II) -oxid, sind einige Nickelvorstufen zur thermischen basierend ALD erhältlich.
Darüber hinaus haben diese Vorstufen bei schlechten Filmeigenschaften führte und die Prozesseigenschaften wurden ebenfalls begrenzt. Daher in dieser Masterarbeit mussten die Eigenschaften verschiedener neuartiger Nickelvorstufen zu bewerten. Alle neuen Vorstufen heteroleptische (verschiedene Arten von Liganden) und Komplexe wurden vom Hersteller speziell zur thermischen basierend ALD aus reinem Nickel mit H 2 als ein Co-Reaktionsmittel gestaltet. Um die neuartige Vorläufer zu untersuchen, wurde eine neue Methode entwickelt, um kleine Mengen in einer sehr zeitsparend (bis zu 2 g) von Ausgangsstoffen zu testen. Diese Methodologie beinhaltet: TGA / DTA-Kurve analysiert der Vorstufen, thermische Stabilitätstests in dem die Vorläufer (<0,1 g) wurden bei erhöhter Temperatur in einer abgedichteten Umgebung für mehrere Stunden wurde die Abscheidung Experimenten und Film Charakterisierungen erhitzt. Die Abscheidungen wurden mit Hilfe der in situ Quarzmikrowaage überwacht, während die anwendungsbezogenen Filmeigenschaften, wie chemische Zusammensetzung, physikalische Phase, Dicke, Dichte, Härte und Schichtwiderstand wurden mit Hilfe von ex situ Messverfahren untersucht.
Vor der Evaluierung neuartiger Nickelvorstufen ein Benchmark ALD-Prozess war vom Referenznickelvorläufer (Ni (AMD)) und Luft als Reaktionspartner entwickelt. Das Hauptziel der Entwicklung und Optimierung von solchen Benchmark-ALD-Prozess war es, Standard-Prozessparameter wie zweite Reaktionspartner Belichtungszeiten, Argonspülung Zeiten, gesamtprozessdruck, beginnend Abscheidungstemperatur und Gasströme zu extrahieren. Diese Standard-Prozessparameter mussten verwendet, um die Prozessentwicklung Aufgabe (das spart Vorläufer Verbrauch) zu verkürzen und die Sublimationstemperatur Optimierung für jede neuartige Vorstufe werden. Die ALD Verhalten wurde in Bezug auf die Wachstumsrate durch Variation des Nickelvorläuferbelichtungszeit, Vorläufer Temperatur und Niederschlagstemperatur überprüft. / Nickel and nickel(II) oxide are widely used in advanced electronic devices . In microelectronic industry, nickel is used to form nickel silicide. The nickel mono-silicide (NiSi) has emerged as an excellent material of choice for source-drain contact applications below 45 nm node CMOS technology. As compared to other silicides used for the contact applications, NiSi is preferred because of its low resistivity, low contact resistance, relatively low formation temperature and low silicon consumption. Nickel is used in nickel-based rechargeable batteries and ferromagnetic random access memories (RAMs). Nickel(II) oxide is utilized as transistor gate-oxide and oxide in resistive RAMs.
Atomic Layer Deposition (ALD) is a special type of Chemical Vapor Deposition (CVD) technique, that is used to deposit very smooth as well as homogeneous thin films with excellent conformality even at high aspect ratios. It is based on self-terminating sequential gas-solid reactions that allow a precise control of film thickness down to few Angstroms. In order to fabricate todays 3D electronic devices, technologies like ALD are required.
In spite of huge number of practical applications of nickel and nickel(II) oxide, a few nickel precursors are available for thermal based ALD. Moreover, these precursors have resulted in poor film qualities and the process properties were also limited. Therefore in this master thesis, the properties of various novel nickel precursors had to be evaluated. All novel precursors are heteroleptic (different types of ligands) complexes and were specially designed by the manufacturer for thermal based ALD of pure nickel with H 2 as a co-reactant.
In order to evaluate the novel precursors, a new methodology was designed to test small amounts (down to 2 g) of precursors in a very time efficient way. This methodology includes: TGA/DTA curve analyses of the precursors, thermal stability tests in which the precursors (< 0.1 g) were heated at elevated temperatures in a sealed environment for several hours, deposition experiments, and film characterizations. The depositions were monitored with the help of in situ quartz crystal microbalance, while application related film properties like chemical composition, physical phase, thickness, density, roughness and sheet resistance were investigated with the help of ex situ measurement techniques.
Prior to the evaluation of novel nickel precursors, a benchmark ALD process was developed from the reference nickel precursor (Ni(amd)) and air as a co-reactant. The main goal of developing and optimizing such benchmark ALD process was to extract standard process parameters like second-reactant exposure times, Argon purge times, total process pressure, starting deposition temperature and gas flows. These standard process parameters had to be utilized to shorten the process development task (thus saving precursor consumption) and optimize the sublimation temperature for each novel precursor. The ALD behaviour was checked in terms of growth rate by varying the nickel precursor exposure time, precursor temperature and deposition temperature.
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