Dissertations / Theses on the topic 'Material modifications by ion beam'

V této práci je představeno zařízení pro ozařování MeV ionty při tandemovém urychlovači na univerzitě v Uppsale. Jsou podány základy teorie interakce iontů s pevnou látkou a modifikace materiálu pomocí iontů s vysokou energií. Zařízení tandemového urychlovače je popsáno počínaje generací iontů a konče dopadem iontů na vzorek v hlavní komoře zařízení pro iontové ozařování. Následně jsou detailně charakterizovány modifikace systému pro přesun vzorků a popsán princip jeho funkce. Pilotní aplikace upraveného systému v oblasti materiálových modifikací je prezentována na příkladu ozařování Ge kvantových teček. Homogenita rozložení iontů na vzorku při ozařování je testována pomocí simulace elektrostatického deflektoru.

Diante da crescente necessidade de materiais com melhores propriedades para aplicações nos diversos campos da ciência e da tecnologia, a irradiação com feixes iônicos mostra-se como uma importante ferramenta de modicação de materiais. A irradiação de polímeros, em especial, fornece sempre novas perspectivas de aplicabilidade para esses materiais. Diante disso, o presente trabalho tem como objetivo estudar quais são e como ocorrem os processos de modicação de polímeros irradiados com feixes de íons de alta energia. Para essa investigação, amostras de politetrauoroetileno (PTFE) e poli éter éter cetona (PEEK) foram irradiadas no acelerador Unilac do GSI Helmholtzzentrum für Schwerionenforschung GmbH, em Darmstadt, Alemanha, com feixes de íons C, Xe, Au e U, de energia entre 3,6 e 11,4 MeV/u. As amostras foram submetidas à irradiação sob temperatura ambiente e temperatura criogênica (20-40 K). A análise das amostras irradiadas foi realizada através das seguintes técnicas: análise de gases residuais (RGA), espectroscopia de absorção UV-Vis, espectroscopia de absorção no infravermelho com transformada de fourier (FTIR) e difração de raios X (XRD). Observou-se que durante a irradiação do PTFE, os principais processos de modicação são as quebras moleculares e a formação do radical CF3 como grupo terminal e lateral. Além desses, também ocorrem processos de entrelaçamento e formação de estruturas insaturadas, com ligações duplas internas e terminais. Os principais fragmentos voláteis são o CF e o CF3. Durante a irradiação do PEEK observou-se liberação de gás hidrogênio em grande quantidade, como consequência da quebra dos anéis aromáticos do polímero. Algumas reações de recombinação deram origem a formação dos grupos alcino, éster, uorenona e álcool. Além disso o processo de carbonização da amostra foi responsável pelo aumento da condutividade do material. Durante a irradiação sob temperatura criogênica, alguns processos de recombinação nos materiais foram dicultados e grande parte dos elementos voláteis gerados permaneceu congelada no interior do polímero, sendo liberada durante posterior aquecimento até temperatura ambiente. Alguns modelos propostos para explicar efeitos de degradação térmica ou após irradiação com feixe de elétrons foram estendidos com sucesso aos resultados da irradiação com íons pesados e de alta energia.
Nowadays the demand for materials with improved properties for application in different elds of science and technology is constant. Ion beam irradiation is a usual and important tool of modication of materials and polymer irradiation, in particular, has given new perspectives of use for these modied materials. Hence, the aim of this work is the identication of the processes of modication of polymers irradiated with high energy ion beams and how they occur. In this investigation, samples of polytetrauorethylene (PTFE) and poly-ether etherketone (PEEK) were irradiated at the Unilac accelerator at GSI Helmholtzzentrum for Schwerionenforschung GmbH, at Darmstadt, Germany, with C, Xe, Au and U beams with energy between 3.6 and 11.4 MeV/u. The samples were irradiated at room and cryogenic (20-40 K) temperature. The sample analyses were performed through: Residual Gas Analysis (RGA), UV-Vis Absorption Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and X Ray Diraction (XRD). Under irradiation, the main processes of modication of PTFE were the chain scissioning and the formation of CF3 terminal and side group. Besides that, cross-linking and new unsaturated structures were also observed, evidenced by the formation of terminal and internal double bonds. CF3 and CF were the main degassed fragments that were observed. During irradiation of PEEK, a great amount of hydrogen gas was liberated as a consequence of the scission in the aromatics rings. Some rearrangement reactions occurred and gave rise to formation of the following groups: alkyne, esther, uorenon and alcohol. Moreover, the process of carbonization in the sample caused an increase in the polymer conductivity. When irradiated under cryo-temperature some recombination processes became more dicult and most of the volatile fragments remained frozen in the polymers. Some degradation models proposed to explain damage effects after thermal and electron beam exposure were sucessfully extended to the obtained results in the case of irradiation with swift heavy ions.

In the last years, there is a rise of interest in investigation and fabrication of nanometer sized magnetic structures due to their various applications (e.g. for data storage or micro sensors). Over the last several decades ion beam implantation became an important tool for the modification of materials and in particular for the manipulation of magnetic properties. Nanopatterning and implantation can be done simultaneously using focused-ion beam (FIB) techniques. FIB implantation and standard ion implantation differ in their beam current densities by 7 orders of magnitude. This difference can strongly influence the structural and magnetic properties, e.g. due to a rise of the local temperature in the sample during ion implantation. In previous investigations both types of implantation techniques were studied separately. The aim of the current research was to compare both implantation techniques in terms of structural changes and changes in magnetic properties using the same material system. Moreover, to separate any possible annealing effects from implantation ones, the influence of temperature on the structural and magnetic properties were additionally investigated. For the current study a model material system which is widely used for industrial applications was chosen: a 50 nm thick non-ordered nano-crystalline permalloy (Ni81Fe19) film grown on a SiO2 buffer layer based onto a (100)-oriented Si substrate. The permalloy films were implanted with a 30 keV Ga+ ion beam; and also a series of as-deposited permalloy films were annealed in an ultra-high vacuum (UHV) chamber. Several investigation techniques were applied to study the film structure and composition, and were mostly based on non-destructive X-ray investigation techniques, which are the primary focus of this work. Besides X-ray diffraction (XRD), providing the long-range order crystal structural information, extended X-ray absorption fine structure (EXAFS) measurements to probe the local structure were performed. Moreover, the film thickness, surface roughness, and interface roughness were obtained from the X-ray reflectivity (XRR) measurements. Additionally cross-sectional transmission electron microscope (XTEM) imaging was used for local structural characterizations. The Ga depth distribution of the samples implanted with a standard ion implanter was measured by the use of Auger electron spectroscopy (AES) and Rutherford backscattering (RBS), and was compared with theoretical TRIDYN calculation. The magnetic properties were characterized via polar magneto-optic Kerr effect (MOKE) measurements at room temperature. It was shown that both implantation techniques lead to a further material crystallization of the partially amorphous permalloy material (i.e. to an increase of the amount of the crystalline material), to a crystallite growth and to a material texturing towards the (111) direction. For low ion fluences a strong increase of the amount of the crystalline material was observed, while for high ion fluences this rise is much weaker. At low ion fluences XTEM images show small isolated crystallites, while for high ones the crystallites start to grow through the entire film. The EXAFS analysis shows that both Ni and Ga atom surroundings have a perfect near-order coordination corresponding to an fcc symmetry. The lattice parameter for both implantation techniques increases with increasing ion fluence according to the same linear law. The lattice parameters obtained from the EXAFS measurements for both implantation types are in a good agreement with the results obtained from the XRD measurements. Grazing incidence XRD (GIXRD) measurements of the samples implanted with a standard ion implanter show an increasing value of microstrain with increasing ion fluence (i.e. the lattice parameter variation is increasing with fluence). Both types of implantation result in an increase of the surface and the interface roughness and demonstrate a decrease of the saturation polarization with increasing ion fluence. From the obtained results it follows that FIB and standard ion implantation influence structure and magnetic properties in a similar way: both lead to a material crystallization, crystallite growth, texturing and decrease of the saturation polarization with increasing ion fluence. A further crystallization of the highly defective nano-crystalline material can be simply understood as a result of exchange processes induced by the energy transferred to the system during the ion implantation. The decrease of the saturation polarization of the implanted samples is mainly attributed to the simple presence of the Ga atoms on the lattice sites of the permalloy film itself. For the annealed samples more complex results were found. The corresponding results can be separated into two temperature regimes: into low (≤400°C) and high (>400°C) temperatures. Similar to the implanted samples, annealing results in a material crystallization with large crystallites growing through the entire film and in a material texturing towards the (111) direction. The EXAFS analysis shows a perfect near-order coordination corresponding to an fcc symmetry. The lattice parameter of the annealed samples slightly decreases at low annealing temperatures, reaches its minimum at about ~400°C and slightly rises at higher ones. From the GIXRD measurements it can be observed that the permalloy material at temperatures above >400°C reaches its strain-free state. On the other hand, the film roughness increases with increasing annealing temperature and a de-wetting of the film is observed at high annealing temperatures. Regardless of the material crystallization and texturing, the samples annealed at low temperatures demonstrate no change in saturation polarization, while at high temperatures a rise by approximately ~15% at 800°C was observed. The rise of the saturation polarization at high annealing temperatures is attributed to the de-wetting effect.

This dissertation is related to the understanding of catalytic reactions of metal oxides. For several decades, the surfaces and bulk of materials have been probed to determine additional properties that relate to photocatalytic applications. This investigation furthers these efforts by the (a) modification of a metal oxide surface to isolate known influences of chemical properties and (b) proposing and utilizing a novel methodology for attribution of photocatalytic activity to a discernable influence. For the first effort, by effectively utilizing a known technique for a new application on a metal oxide, such isolations can be made despite unfavorable states. For the second effort, a reduction in the influence of surface states for metal oxides is effectively performed, providing the isolation of influences originating from the bulk. The challenge with such a proposal is verifying such bulk states have been adequately isolated as external influences would obviously distort any conclusions. Thus, techniques to both create such bulk states and eliminate unwanted combinations thereof are additionally required and must be provided for. Lastly, a determination of the photocatalytic activity is made to these states and results are provided.

Hard gold thin films and coatings are widely used in electronics as an effective material to reduce the friction and wear of relatively less expensive electrically conductive materials while simultaneously seeking to provide oxidation resistance and stable sliding electrical contact resistance (ECR). The main focus of this dissertation was to synthesize nanocrystalline Au films with grain structures capable of remaining stable during thermal exposure and under sliding electrical contact stress and the passing of electrical current. Here we have utilized a physical vapor deposition (PVD) technique, electron beam evaporation, to synthesize Au films modified by ion implantation and codeposited ZnO hardened Au nanocomposites. Simultaneous friction and ECR experiments of low fluence (< 1x10^17 cm^-2) He and Ar ion implanted Au films showed reduction in friction coefficients from ~1.5 to ~0.5 and specific wear rates from ~4x10^-3 to ~6x10^-5 mm^3/N·m versus as-deposited Au films without significant change in sliding ECR (~16 mΩ). Subsurface microstructural changes of He implanted films due to tribological stress were analyzed via site-specific cross-sectional transmission electron microscopy (TEM) and revealed the formation of nanocrystalline grains for low energy (22.5 keV) implantation conditions as well as the growth and redistribution of cavities. Nanoindentation hardness results revealed an increase from 0.84 GPa for as-deposited Au to ~1.77 GPa for Au uniformly implanted with 1 at% He. These strength increases are correlated with an Orowan hardening mechanism that increases proportionally to (He concentration)1/3. Au-ZnO nanocomposite films in the oxide dilute regime (< 5 vol% ZnO) were investigated for low temperature aging stability in friction and ECR. Annealing at 250 °C for 24 hours Au-(2 vol%)ZnO retained a friction coefficient comparable to commercial Ni hardened Au of ~ 0.3 and sliding ECR values of ~35 mΩ. Nanoindentation hardness increases of these films (~2.6 GPa for 5 vol% ZnO) are correlated to microstructure via high resolution TEM and scanning electron microscope cross-sections to both Hall-Petch and Orowan strengthening mechanisms. Also presented is a correlation between electrical resistivity and grain size in the oxide dilute range based on the Mayadas-Shatzkes (M-S) electron scattering model. Using the M-S model in combination with a model describing solute drag stabilized grain growth kinetics we present a new technique to probe grain boundary mobility and thermal stability from in-situ electrical resistivity measurements during annealing experiments.

Dissertation to obtain a Master degree in Biotechnology
Studies of atomic force microscopy (AFM), a technique commonly associated with material sciences, in the field of biotechnology, with special emphasis on molecular biology and bionanotechnology elements, are presented herein. DNA, insulin and restriction enzymes were analysed as isolated objects, in order to document properties like morphology and behaviour, and also on the interactions between each other. The interaction between DNA and the EcoRV restriction endonuclease was especially highlighted. Gold nanoparticles were also studied in an attempt to establish a relationship between functionalization and average diameter shifts, as perceived by AFM. Given the nature of these objects of study, both immobilization and preparation protocols were modified and evaluated, considering measurements in air or in liquid. To serve the objective of developing probes with higher sensitivity and resolution, especially for liquid measurements, AFM cantilevers were modified through metallic coatings and scanning electron microscopy assisted with focused ion beam (SEM-FIB). Tests performed with these probes confirmed that the modifications were successful, the probes are functional and can aid in the production of better quality images, through the acquisition of sharper data in comparison with non-modified probes.

In der vorliegenden Arbeit wird erstmals das QQDS-Magnetspektrometer für die höchstauflösende Ionenstrahlanalytik leichter Elemente am Helmholtz-Zentrum Dresden-Rossendorf umfassend vorgestellt. Zusätzlich werden sowohl alle auf die Analytik Einfluss nehmenden Parameter untersucht als auch Methoden und Modelle vorgestellt, wie deren Einfluss vermieden oder rechnerisch kompensiert werden kann. Die Schwerpunkte dieser Arbeit gliedern sich in fünf Bereiche. Der Erste ist der Aufbau und die Inbetriebnahme des QQDS-Magnetspektrometers, der zugehörige Streukammer mit allen Peripheriegeräten und des eigens für die höchstauflösende elastische Rückstoßanalyse entwickelten Detektors. Sowohl das umgebaute Spektrometer als auch der im Rahmen dieser Arbeit gebaute Detektor wurden speziell an experimentelle Bedingungen für die höchstauflösende Ionenstrahlanalytik leichter Elemente angepasst und erstmalig auf einen routinemäßigen Einsatz hin getestet. Der Detektor besteht aus zwei Komponenten. Zum einen befindet sich am hinteren Ende des Detektors eine Bragg-Ionisationskammer, die zur Teilchenidentifikation genutzt wird. Zum anderen dient ein Proportionalzähler, der eine Hochwiderstandsanode besitzt und direkt hinter dem Eintrittsfenster montiert ist, zur Teilchenpositionsbestimmung im Detektor. Die folgenden zwei Schwerpunkte beinhalten grundlegende Untersuchungen zur Ionen-Festkörper-Wechselwirkung. Durch die Verwendung eines Magnetspektrometers ist die Messung der Ladungszustandsverteilung der herausgestreuten Teilchen direkt nach einem binären Stoß sowohl möglich als auch für die Analyse notwendig. Aus diesem Grund werden zum einen die Ladungszustände gemessen und zum anderen mit existierenden Modellen verglichen. Außerdem wird ein eigens entwickeltes Modell vorgestellt und erstmals im Rahmen dieser Arbeit angewendet, welches den ladungszustandsabhängigen Energieverlust bei der Tiefenprofilierung berücksichtigt. Es wird gezeigt, dass ohne die Anwendung dieses Modells die Tiefenprofile nicht mit den quantitativen Messungen mittels konventioneller Ionenstrahlanalytikmethoden und mit der Dickenmessung mittels Transmissionselektronenmikroskopie übereinstimmen, und damit falsche Werte liefern würden. Der zweite für die Thematik wesentliche Aspekt der Ionen-Festkörper-Wechselwirkung, sind die Probenschäden und -modifikationen, die während einer Schwerionen-bestrahlung auftreten. Dabei wird gezeigt, dass bei den hier verwendeten Energien sowohl elektronisches Sputtern als auch elektronisch verursachtes Grenzflächendurchmischen eintreten. Das elektronische Sputtern kann durch geeignete Strahlparameter für die meisten Proben ausreichend minimiert werden. Dagegen ist der Einfluss der Grenzflächendurchmischung meist signifikant, so dass dieser analysiert und in der Auswertung berücksichtigt werden muss. Schlussfolgernd aus diesen Untersuchungen ergibt sich für die höchstauflösende Ionenstrahlanalytik leichter Elemente am Rossendorfer 5-MV Tandembeschleuniger, dass die geeignetsten Primärionen Chlor mit einer Energie von 20 MeV sind. In Einzelfällen, wie zum Beispiel der Analyse von Bor, muss die Energie jedoch auf 6,5 MeV reduziert werden, um das elektronische Sputtern bei der notwendigen Fluenz unterhalb der Nachweisgrenze zu halten. Der vierte Schwerpunkt ist die Untersuchung von sowohl qualitativen als auch quantitativen Einflüssen bestimmter Probeneigenschaften, wie beispielsweise Oberflächenrauheit, auf die Form des gemessenen Energiespektrums beziehungsweise auf das analysierte Tiefenprofil. Die Kenntnis der Rauheit einer Probe an der Oberfläche und an den Grenzflächen ist für die Analytik unabdingbar. Als Resultat der genannten Betrachtungen werden die Einflüsse von Probeneigenschaften und Ionen-Festkörper-Wechselwirkungen auf die Energie- beziehungsweise Tiefenauflösung des Gesamtsystems beschrieben, berechnet und mit der konventionellen Ionenstrahlanalytik verglichen. Die Möglichkeiten der höchstauflösenden Ionenstrahlanalytik werden zudem mit den von anderen Gruppen veröffentlichten Komplementärmethoden gegenübergestellt. Der fünfte und letzte Schwerpunkt ist die Analytik leichter Elemente in ultradünnen Schichten unter Berücksichtigung aller in dieser Arbeit vorgestellten Modelle, wie die Reduzierung des Einflusses von Strahlschäden oder die Quantifizierung der Elemente im dynamischen Ladungszustandsnichtgleichgewicht. Es wird die Tiefenprofilierung von Mehrschichtsystemen, bestehend aus SiO2-Si3N4Ox-SiO2 auf Silizium, von Ultra-Shallow-Junction Bor-Implantationsprofilen und von ultradünnen Oxidschichten, wie zum Beispiel High-k-Materialien, demonstriert
In this thesis the QQDS magnetic spectrometer that is used for high resolution ion beam analysis (IBA) of light elements at the Helmholtz-Zentrum Dresden-Rossendorf is presented for the first time. In addition all parameters are investigated that influence the analysis. Methods and models are presented with which the effects can be minimised or calculated. There are five focal points of this thesis. The first point is the construction and commissioning of the QQDS magnetic spectrometer, the corresponding scattering chamber with all the peripherals and the detector, which is specially developed for high resolution elastic recoil detection. Both the reconstructed spectrometer and the detector were adapted to the specific experimental conditions needed for high-resolution Ion beam analysis of light elements and tested for routine practice. The detector consists of two compo-nents. At the back end of the detector a Bragg ionization chamber is mounted, which is used for the particle identification. At the front end, directly behind the entrance window a proportional counter is mounted. This proportional counter includes a high-resistance anode. Thus, the position of the particles is determined in the detector. The following two points concern fundamental studies of ion-solid interaction. By using a magnetic spectrometer the charge state distribution of the particles scattered from the sample after a binary collision is both possible and necessary for the analysis. For this reason the charge states are measured and compared with existing models. In addition, a model is developed that takes into account the charge state dependent energy loss. It is shown that without the application of this model the depth profiles do not correspond with the quantitative measurements by conventional IBA methods and with the thickness obtained by transmission electron microscopy. The second fundamental ion-solid interaction is the damage and the modification of the sample that occurs during heavy ion irradiation. It is shown that the used energies occur both electronic sputtering and electronically induced interface mixing. Electronic sputtering is minimised by using optimised beam parameters. For most samples the effect is below the detection limit for a fluence sufficient for the analysis. However, the influence of interface mixing is so strong that it has to be included in the analysis of the layers of the depth profiles. It is concluded from these studies that at the Rossendorf 5 MV tandem accelerator chlorine ions with an energy of 20 MeV deliver the best results. In some cases, such as the analysis of boron, the energy must be reduced to 6.5 MeV in order to retain the electronic sputtering below the detection limit. The fourth focus is the study of the influence of specific sample properties, such as surface roughness, on the shape of a measured energy spectra and respectively on the analysed depth profile. It is shown that knowledge of the roughness of a sample at the surface and at the interfaces for the analysis is needed. In addition, the contribution parameters limiting the depth resolution are calculated and compared with the conventional ion beam analysis. Finally, a comparison is made between the high-resolution ion beam analysis and complementary methods published by other research groups. The fifth and last focus is the analysis of light elements in ultra thin layers. All models presented in this thesis to reduce the influence of beam damage are taken into account. The dynamic non-equilibrium charge state is also included for the quantification of elements. Depth profiling of multilayer systems is demonstrated for systems consisting of SiO2-Si3N4Ox-SiO2 on silicon, boron implantation profiles for ultra shallow junctions and ultra thin oxide layers, such as used as high-k materials

L'évolution du spectre infrarouge du benzène adsorbe sur des faujasites est suivie en fonction de la composition chimique des adsorbants (zéolites désaluminées, zéolite y ou x, zéolites modifiées par des ions Na, Rb, etc) et de la quantité de benzène adsorbé. On note que 4 formes de benzène ont été mises en évidence, dont l'une est faiblement fixée sur les solides.

Les batteries, et en particulier les batteries lithium-ion (Li-ion), sont devenues des vecteurs de stockage de l'énergie particulièrement adaptés à l'avènement des très nombreuses applications portables (téléphones ou ordinateurs). Dans le but d'améliorer et de rendre plus sûrs ces vecteurs, il est impératif de pouvoir comprendre et caractériser de la manière la plus précise les matériaux les constituant et les interfaces les séparant. Pour cela, l'utilisation d'outils puissants et adaptés est essentielle, notamment depuis l'apparition de matériaux ayant une architecture à l'échelle nanométrique. Ainsi, l'utilisation de la Microscopie Electronique en Transmission (MET) est particulièrement prometteuse, pour sa capacité à analyser les propriétés morphologiques, structurales ou chimiques à cette échelle. Fort de ce constat, nous avons tenté de réaliser la première observation in situ dans un MET d'une batterie en cours de cyclage électrochimique. La première partie de ce manuscrit est dédiée à la présentation de la stratégie utilisée. En effet, les nombreuses difficultés liées à la fois à l'environnement du MET et à la nature même d'une batterie, nous ont forcé à faire des choix basés sur l'analyse de l'état de l'art, principalement en termes de matériaux, de technologies et d'équipements expérimentaux. Ainsi, ce projet est basé sur l'étude d'une microbatterie Li-ion tout solide. Le deuxième chapitre est lui consacré au procédé de fabrication par ablation laser de ces microbatteries tout solide, avec notamment la synthèse et la caractérisation de chacun des matériaux actifs constitutifs. La troisième partie décrit les solutions envisagées pour lever certaines des incertitudes qui avaient été identifiées. Nous avons ainsi réussi la première observation ex situ par MET d'une "nanobatteries" obtenue par découpe d'une microbatterie à l'aide d'un faisceau d'ions focalisés (FIB) dans un MEB à double faisceaux. Les analyses par MET entre des coupes de batteries après dépôt et ayant subi un cyclage électrochimique ont permis de mettre en évidence, pour la première fois, de nombreux dommages ou des mécanismes de détérioration des interfaces. Les premiers essais, et notamment la configuration utilisée, n'ayant pas permis de réaliser les premiers tests de cyclage in situ dans un MET, plusieurs modifications ont dû être opérées, qui sont présentées dans le dernier chapitre. Ce nouveau design a permis d'expérimenter un cyclage in situ sur des "nanobatteries" et de mettre en lumière les derniers challenges à relever.

Photonic crystals (PhCs) are periodic dielectric structures that exhibit a photonic bandgap, i.e., a range of wavelength for which light propagation is forbidden. The special band structure related dispersion properties offer a realm of novel functionalities and interesting physical phenomena. PhCs have been manufactured using semiconductors and other material technologies. However, InP-based materials are the main choice for active devices at optical communication wavelengths. This thesis focuses on two-dimensional PhCs in the InP/GaInAsP/InP material system and addresses their fabrication technology and their physical properties covering both material issues and light propagation aspects. Ar/Cl2 chemically assisted ion beam etching was used to etch the photonic crystals. The etching characteristics including feature size dependent etching phenomena were experimentally determined and the underlying etching mechanisms are explained. For the etched PhC holes, aspect ratios around 20 were achieved, with a maximum etch depth of 5 microns for a hole diameter of 300 nm. Optical losses in photonic crystal devices were addressed both in terms of vertical confinement and hole shape and depth. The work also demonstrated that dry etching has a major impact on the properties of the photonic crystal material. The surface Fermi level at the etched hole sidewalls was found to be pinned at 0.12 eV below the conduction band minimum. This is shown to have important consequences on carrier transport. It is also found that, for an InGaAsP quantum well, the surface recombination velocity increases (non-linearly) by more than one order of magnitude as the etch duration is increased, providing evidence for accumulation of sidewall damage. A model based on sputtering theory is developed to qualitatively explain the development of damage. The physics of dispersive phenomena in PhC structures is investigated experimentally and theoretically. Negative refraction was experimentally demonstrated at optical wavelengths, and applied for light focusing. Fourier optics was used to experimentally explore the issue of coupling to Bloch modes inside the PhC slab and to experimentally determine the curvature of the band structure. Finally, dispersive phenomena were used in coupled-cavity waveguides to achieve a slow light regime with a group index of more than 180 and a group velocity dispersion up to 10^7 times that of a conventional fiber.
QC 20100712

Controlled thermonuclear fusion may become an attractive future electrical power source. The most promising of all fusion machine concepts is called a tokamak. The fuel, a plasma made of deuterium and tritium, must be confined to enable the fusion process. It is also necessary to protect the wall of tokamaks from erosion by the hot plasma. To increase wall lifetime, the high-Z metal tungsten is foreseen as wall material in future fusion devices due to its very high melting point. This thesis focuses on the following consequences of plasma impact on a high-Z wall: (i) erosion, transport and deposition of high-Z wall materials; (ii) fuel retention in tokamak walls; (iii) long term effects of plasma impact on structural machine parts; (iv) dust production in tokamaks. An extensive study of wall components has been conducted with ion beam analysis after the final shutdown of the TEXTOR tokamak. This unique possibility offered by the shutdown combined with a tracer experiment led to the largest study of high-Z metal migration and fuel retention ever conducted. The most important results are:   - transport is greatly affected by drifts and flows in the plasma edge; - stepwise transport along wall surfaces takes place mainly in the toroidal direction; - fuel retention is highest on slightly retracted wall elements; - fuel retention is highly inhomogeneous.   A broad study on structural parts of a tokamak has been conducted on the TEXTOR liner. The plasma impact does neither degrade mechanical properties nor lead to fuel diffusion into the bulk after 26 years of duty time. Peeling deposition layers on the liner retain fuel in the order of 1g and represent a dust source. Only small amounts of dust are found in TEXTOR with overall low deuterium content. Security risks in future fusion devices due to dust explosions or fuel retention in dust are hence of lesser concern.

QC 20170630

Obwohl Wasserstoff omnipräsent ist, ist seine Analytik anspruchsvoll und es stehen nur wenige analytische Verfahren zur Auswahl. Unter diesen nimmt die auf einer Kernreaktion von Wasserstoff und Stickstoff basierende N-15-Methode einen herausragenden Platz ein. Sie liefert eine ortsaufgelöste Wasserstoffkonzentration bis in den ppm-Bereich in oberflächennahen Schichten (kleiner 2 µm). Gegenstand der Arbeit sind die Darstellung der Theorie der N-15-Kernreaktionsanalyse (NRA), des experimentellen Aufbaus des entsprechenden Strahlrohrs am Ionenbeschleuniger der BAM und der Auswertung der Messergebnisse. Ziel ist die erstmalige Charakterisierung eines Referenzmaterials für die H-Analytik auf Basis von amorphen Silizium (aSi) auf einem Si[100]-Substrat. International wird von den metrologischen Instituten NIST [REE90] und IRMM [VAN87] je ein Referenzmaterial für die Heißextraktion in Form von Titanplättchen angeboten. Diese sind aber für die oberflächennahen Verfahren (NRA, ERDA, GDOES, SIMS) nicht nutzbar, da die oberflächennahe Konzentration von Wasserstoff in Titan nicht konstant ist. Die Homogenität der mittels CVD abgeschiedenen aSi:H-Schichten wurde untersucht. Dazu wurden pro Substrat für ca. 30 Proben die Wasserstofftiefenprofile gemessen, mittels eines innerhalb der Arbeit entstandenen Programms entfaltet und der statischen Auswertung unterzogen. Das Ergebnis waren Mittelwert und Standardabweichung der Wasserstoffkonzentration, sowie ein Schätzer für den Beitrag der Inhomogenität zur Meßunsicherheit. Die Stabilität des potentiellen Referenzmaterials wurde durch die Konstanz der Ergebnisse von Wiederholtungsmessungen der Wasserstoffkonzentrtion während der Applikation einer hohen Dosis von N-15 Ionen bewiesen. In einem internationalen Ringversuch wurde die Rückführbarkeit der Messergebnisse nachgewiesen. Teilnehmer waren 13 Labore aus 7 Ländern. Eingesetzt wurden N-15 und F-19 NRA, ERDA und SIMS. Besonderer Beachtung wurde der Bestimmung der Messunsicherheiten gewidmet. Für die Charakterisierung der aSi:H-Schichten wurden neben der NRA die Weißlichtinterferometrie, Ellipsometrie, Profilometrie und Röngenreflektometrie, sowie die IR- und Ramanspektroskopie genutzt. Die Stöchiometrie des eingesetzten Standardmaterials Kapton wurde mittels NMR-Spekroskopie und CHN-Analyse überprüft. [VAN87] Vandendriessche, S., Marchandise, H., Vandecasteele, C., The certification of hydrogen in titanium CRM No318, Brüssel-Luxembourg,1987 [REE90] Reed, W.P., Certificate of Analysis SRM 352c, Gaithersburg, NIST, 1990

Obwohl Wasserstoff omnipräsent ist, ist seine Analytik anspruchsvoll und es stehen nur wenige analytische Verfahren zur Auswahl. Unter diesen nimmt die auf einer Kernreaktion von Wasserstoff und Stickstoff basierende N-15-Methode einen herausragenden Platz ein. Sie liefert eine ortsaufgelöste Wasserstoffkonzentration bis in den ppm-Bereich in oberflächennahen Schichten (kleiner 2 µm). Gegenstand der Arbeit sind die Darstellung der Theorie der N-15-Kernreaktionsanalyse (NRA), des experimentellen Aufbaus des entsprechenden Strahlrohrs am Ionenbeschleuniger der BAM und der Auswertung der Messergebnisse. Ziel ist die erstmalige Charakterisierung eines Referenzmaterials für die H-Analytik auf Basis von amorphen Silizium (aSi) auf einem Si[100]-Substrat. International wird von den metrologischen Instituten NIST [REE90] und IRMM [VAN87] je ein Referenzmaterial für die Heißextraktion in Form von Titanplättchen angeboten. Diese sind aber für die oberflächennahen Verfahren (NRA, ERDA, GDOES, SIMS) nicht nutzbar, da die oberflächennahe Konzentration von Wasserstoff in Titan nicht konstant ist. Die Homogenität der mittels CVD abgeschiedenen aSi:H-Schichten wurde untersucht. Dazu wurden pro Substrat für ca. 30 Proben die Wasserstofftiefenprofile gemessen, mittels eines innerhalb der Arbeit entstandenen Programms entfaltet und der statischen Auswertung unterzogen. Das Ergebnis waren Mittelwert und Standardabweichung der Wasserstoffkonzentration, sowie ein Schätzer für den Beitrag der Inhomogenität zur Meßunsicherheit. Die Stabilität des potentiellen Referenzmaterials wurde durch die Konstanz der Ergebnisse von Wiederholtungsmessungen der Wasserstoffkonzentrtion während der Applikation einer hohen Dosis von N-15 Ionen bewiesen. In einem internationalen Ringversuch wurde die Rückführbarkeit der Messergebnisse nachgewiesen. Teilnehmer waren 13 Labore aus 7 Ländern. Eingesetzt wurden N-15 und F-19 NRA, ERDA und SIMS. Besonderer Beachtung wurde der Bestimmung der Messunsicherheiten gewidmet. Für die Charakterisierung der aSi:H-Schichten wurden neben der NRA die Weißlichtinterferometrie, Ellipsometrie, Profilometrie und Röngenreflektometrie, sowie die IR- und Ramanspektroskopie genutzt. Die Stöchiometrie des eingesetzten Standardmaterials Kapton wurde mittels NMR-Spekroskopie und CHN-Analyse überprüft. [VAN87] Vandendriessche, S., Marchandise, H., Vandecasteele, C., The certification of hydrogen in titanium CRM No318, Brüssel-Luxembourg,1987 [REE90] Reed, W.P., Certificate of Analysis SRM 352c, Gaithersburg, NIST, 1990

Cette thèse porte sur l’évaluation des techniques pour la tomographie chimique par STEM EDX : mise au point des procédures expérimentales, traitement des données, reconstruction des volumes, analyse de la qualité des résultats obtenus et évaluation de la complexité globale. Les performances très limitées de l’analyse STEM EDX font que peu d’études, jusqu’à aujourd’hui, se sont portées sur cette technique. Cependant, les avancées très notables procurées par les nouveaux détecteurs ‘SDD’ ainsi que les sources électroniques X-FEG haute brillance, rendant l’analyse STEM EDX 2D très rapide, ont relancé la possibilité de la tomographie chimique ; la technique demande toutefois à être mise au point et évaluée (performances et complexité). Nous avons travaillé sur un microscope Tecnai Osiris permettant d’acquérir des cartographies chimiques EDX de centaines de milliers de pixels avec une résolution de l’ordre du nanomètre en quelques minutes. Nous avons choisi de préparer par FIB des échantillons en forme de pointe et d’utiliser un porte-objet permettant une exploration angulaire de 180° sans ombrage. Puis, à l’aide d’échantillons modèles (billes de SiO2 dans une résine), nous avons évalué les déformations d’échantillon par l’irradiation du faisceau électronique. Ceci nous a permis de proposer une méthode pour limiter cet effet par déposition d’une couche de 20 nm de chrome. Des simulations d’images ont permis d’évaluer les logiciels et méthodes de reconstruction. La méthodologie de chaque étape d’une analyse de tomographie STEM EDX a ensuite été expliquée, et l’intérêt de la technique démontré grâce à la comparaison de l’analyse 2D et 3D d’un transistor FDSOI 28 nm. La qualité des reconstructions (rapport signal-sur-bruit, résolution spatiale) a été évaluée en fonction des paramètres expérimentaux à l’aide de simulations et d’expériences. Une résolution de 4 nm est démontrée grâce à l’analyse d’une mire et d’un transistor « gate all around ». Pour ce même transistor, la possibilité et l’intérêt d’analyse de défaillance à l’échelle nanométrique est prouvée. Une analyse d’un défaut de grille d’une SRAM ou de trous dans un pilier en cuivre permettent d’expliquer l’intérêt d’une combinaison d’un volume HAADF (morphologie et résolution < 4 nm) et du volume EDX (information chimique). La conclusion est que cette technique, qui reste encore à améliorer du point de vue de sa simplicité, montre déjà son utilité pour l’analyse et la mise au point des technologies avancées (nœud 20 nm et après)
This thesis focuses on the evaluation of the STEM EDX chemical tomography technique: development of experimental procedures, data processing and volumes reconstruction, quality analysis of the results and evaluation of the overall complexity. Until now, STEM EDX analysis performances were very limited, so only few studies about this technique have been realized. However, very significant progress procured by the new SDD detectors as well as by the high brightness electronic sources (X-FEG), making the STEM EDX 2D analysis very fast, have revived the possibility of the chemical tomography, although the technique has to be developed and evaluated (performance and complexity). We have worked on a Tecnai Osiris which acquires EDX chemical mapping of hundreds of thousands of pixels with resolution of one nanometer and in a few minutes. We chose to prepare the rod-shaped samples by FIB and use a sample holder allowing an angle of exploration of 180° without shadowing effects. Then, using model samples (SiO2 balls in resin), we evaluated the sample deformation due to the electron beam irradiation. This allowed us to propose a method to reduce this effect by depositing a 20 nm chromium layer. Images simulations were used to evaluate the software and the reconstruction methods. The methodology of each step of the STEM EDX tomography analysis is then explained and the technique interest is demonstrated by comparing the 2D and the 3D analysis of a transistor 28 nm FDSOI. The quality of the reconstructions (signal-to-noise ratio, spatial resolution) was evaluated, in function of experimental parameters, using simulations and experiments. A resolution of 4 nm is demonstrated through the analysis of a test pattern and a "gate all around” transistor. For the same transistor, the possibility and the interest of a failure analysis at the nanoscale is proven. Analyses of a SRAM gate fail or of the holes in a copper pillar explain the benefits of a combination between a HAADF volume (morphology and resolution < 4 nm) and an EDX volume (chemical information). To conclude, this technique, which still needs to be improved in terms of simplicity, is already showing its usefulness for the analysis and the development of advanced technologies (20nm node and beyond)

Die vorliegende Arbeit entstand im Rahmen einer Kooperation des Forschungszentrums Dresden-Rossendorf mit Qimonda Dresden GmbH & Co. OHG. Mithilfe der hochauflösenden Rutherford-Streuspektrometrie (HR-RBS) wurden das Diffusionsverhalten und Schichtwachstum von ZrO2 auf SiO2 und TiN im Anfangsstadium untersucht. Auf Grund der exzellenten Tiefenauflösung von 0,3 nm an der Oberfläche stand die Analyse von Konzentrationsprofilen in ultradünnen Schichten, respektive an deren Grenzflächen im Vordergrund. Zur qualitativen Verbesserung der Messergebnisse wurde erstmals ein zweidimensionaler positionsempfindlicher Halbleiterdetektor in den Aufbau der HR-RBS implementiert und charakterisiert. Außerdem wurde ein Messverfahren in Betrieb genommen, das mögliche Schädigungen durch den Ioneneintrag in die Messprobe minimiert. Durch die Optimierung der experimentellen Bedingungen und die Entwicklung eines Programmpaketes zur Unterstützung des Analysten konnte ein effizienter Routine-Messablauf erstellt werden. Im Moment einer binären Kollision zwischen einfallendem Ion und Targetelement kommt es bei kleinem Stoßparameter zu Veränderungen des Ladungszustands der gestreuten Ionen, insbesondere durch die abrupte Geschwindigkeitsänderung des Projektils und der Überlappung der Elektronenwolken. Bei der HR-RBS mit Energie separierendem Dipolmagneten muss zur Interpretation von Streuspektren die Ladungszustandsverteilung der gestreuten Projektile bekannt sein. Erstmalig konnte eine signifikante Abhängigkeit der Ladungszustandsverteilung gestreuter C-Ionen sowohl von der Schichtdicke als auch der Ordnungszahl des detektierten Targetelements, hier der vierten Nebengruppe, nachgewiesen werden. Diese gewonnen Erkenntnisse ermöglichten systematische Untersuchungen zum ZrO2-Schichtwachstum im Anfangsstadium. Zur Herstellung der ZrO2-Schichten wurde die Atomlagenabscheidung (ALD) verwendet. Anhand der nachgewiesenen Agglomeration von ZrO2 auf nativen SiO2 wurde mithilfe der Rasterkraftmikroskopie (AFM) zur Bestimmung von Oberflächenrauigkeiten eine Methode konzipiert, welche die Auswirkung lokaler Schichtdickeninhomogenitäten auf die niederenergetische Flanke eines Streuspektrums berücksichtigt. Auf dieser Grundlage durchgeführte Simulationsrechnungen ergeben, dass keine Diffusion von Zr in die darunter liegende Schicht stattfand, jedoch eine ZrSiO4-Grenzflächenschicht existiert. Für das Wachstum von ZrO2 auf TiN wird aus den hoch aufgelösten Streuspektren ein völlig anderes Verhalten abgeleitet. Messungen zu Oberflächentopografien der TiN-Schicht liefern nicht zu vernachlässigende Werte für die Rauigkeit. Um den Einfluss der Oberflächenrauigkeit auf die Form des hoch aufgelösten Spektrums erfassen zu können, wurde eine Software entwickelt. Auf Basis von AFM-Messungen ermöglicht dieses Programm das Extrahieren einer Energieverteilung aus den Weglängen von ausschließlich an der Oberfläche gestreuten Ionen. Unter Berücksichtigung des Effekts der Oberflächenrauigkeit auf die HR-RBS Spektrenform konnte die Diffusion von Zr in das polykristalline TiN erstmals verifiziert werden. Die Beobachtungen weisen daraufhin, dass bereits nach dem ersten ALD-Zyklus ein geringer Anteil der deponierten Zr-Atome bis in eine Tiefe von etwa 3 nm in das TiN diffundiert. Die vorläufigen Ergebnisse legen Korngrenzendiffusion nahe
This thesis originated from a cooperation between Research Center Dresden-Rossendorf and Qimonda Dresden GmbH & Co. OHG. By means of High Resolution Rutherford Backscattering Spectrometry (HR-RBS) the diffusion behaviour and layer growth of ZrO2 on SiO2 and TiN in the initial regime were investigated. The analysis of concentration profiles in ultrathin layers and interfaces was the focus of this work, made possible by the excellent depth resolution of less than 0.3 nm near the surface. For the first time a two-dimensional position sensitive semiconductor detector was implemented and characterized in the setup of the HR-RBS for the improvement of the quality of the measurement results. Furthermore, a measurement procedure was put into operation that allowed the reduction of ion induced damage. Through the optimization of the experimental conditions and the development of a program package for the support of the analyst, an efficient measurement procedure could be routinely ensured. At the time of a binary collision between the incident ion and the target element with a small impact factor, the charge state changes frequently, especially due to the abruptly decreasing ion velocity of the projectile and the overlapping of the electron clouds. For HR-RBS with an energy-separating dipole magnet, the charge state distribution of the scattered ions must be known for the interpretation of the measured spectra. For the first time a significant dependence of the charge state distribution of the scattered C ions on the layer thickness as well as atomic number of the detected target elements, here from the fourth subgroup, was emonstrated. This new knowledge allowed systematic investigations of the ZrO2 layer growth in the initial regime. The ZrO2 layers were produced by means of the atomic layer deposition (ALD). Based on the evidence for agglomeration of ZrO2 on SiO2 a method was introduced, which takes local thickness variations into account during the simulation of the HR-RBS spectra. An accurate statement about the ZrO2/SiO2 interface was possible due to the extraction of the thickness variation by the atomic force microscopy (AFM). The boundary surface is sharp except for a small intermediate ZrSiO4 layer and no diffusion of Zr atoms in SiO2 could be detected. A quite different behaviour could be derived from high resolution spectra for the growth of ZrO2 on TiN. Measurements of the surface topography of the TiN layer revealed non negligible values for the surface roughness. A program was developed to capture the influence of the surface roughness on the shape of the high resolution spectrum. This software uses AFM measurements to extract an energy distribution from calculated path length differences for ions scattered at the sample surface. Diffusion of Zr into polycrystalline TiN was demonstrated for the first time taking into account the effect of the surface roughness on the shape of the spectra. This observation indicates that already after the first ALD reaction cycle a small part of the deposited Zr atoms diffuses into the TiN layer up to a depth of 3 nm. Such preliminary results suggest grain boundary diffusion

This thesis focuses on the effect of microstructural variation on the mechanical properties and deformation behavior of ductile iron. To research and determine these effects, two grades of ductile iron, (i) GJS-500-7 and (ii) high silicon GJS-500-14, were cast in a geometry containing several plates with different section thicknesses in order to produce microstructural variation. Microstructural investigations as well as tensile and hardness tests were performed on the casting plates. The results revealed higher ferrite fraction, graphite particle count, and yield strength in the high silicon GJS-500-14 grade compared to the GJS-500-7 grade. To study the relationship between the microstructural variation and tensile behavior on macroscale, tensile stress-strain response was characterized using the Ludwigson equation. The obtained tensile properties were modeled, based on the microstructural characteristics, using multiple linear regression and analysis of variance (ANOVA). The models showed that silicon content, graphite particle count, ferrite fraction, and fraction of porosity are the major contributing factors that influence tensile behavior. The models were entered into a casting process simulation software, and the simulated microstructure and tensile properties were validated using the experimental data. This enabled the opportunity to predict tensile properties of cast components with similar microstructural characteristics. To investigate deformation behavior on micro-scale, a method was developed to quantitatively measure strain in the microstructure, utilizing the digital image correlation (DIC) technique together with in-situ tensile testing. In this method, a pit-etching procedure was developed to generate a random speckle pattern, enabling DIC strain measurement to be conducted in the matrix and the area between the graphite particles. The method was validated by benchmarking the measured yield strength with the material’s standard yield strength. The microstructural deformation behavior under tensile loading was characterized. During elastic deformation, strain mapping revealed a heterogeneous strain distribution in the microstructure, as well as shear bands that formed between graphite particles. The crack was initiated at the stress ranges in which a kink occurred in the tensile curve, indicating the dissipation of energy during both plastic deformation and crack initiation. A large amount of strain localization was measured at the onset of the micro-cracks on the strain maps. The micro-cracks were initiated at local strain levels higher than 2%, suggesting a threshold level of strain required for micro-crack initiation. A continuum Finite Element (FE) model containing a physical length scale was developed to predict strain on the microstructure of ductile iron. The material parameters for this model were calculated by optimization, utilizing the Ramberg-Osgood equation. The predicted strain maps were compared to the strain maps measured by DIC, both qualitatively and quantitatively. To a large extent, the strain maps were in agreement, resulting in the validation of the model on micro-scale. In order to perform a micro-scale characterization of dynamic deformation behavior, local strain distribution on the microstructure was studied by performing in-situ cyclic tests using a scanning electron microscope (SEM). A novel method, based on the focused ion beam (FIB) milling, was developed to generate a speckle pattern on the microstructure of the ferritic ductile iron (GJS-500-14 grade) to enable quantitative DIC strain measurement to be performed. The results showed that the maximum strain concentration occurred in the vicinity of the micro-cracks, particularly ahead of the micro-crack tip.
Denna avhandling fokuserar på effekten av variationer i mikrostrukturen på mekaniska egenskaper och deformationsbeteende hos segjärn. För att undersöka dessa effekter, två olika sorter av segjärn, (i) GJS-500-7 och (ii) högkisellegerad GJS-500-14, gjutits till plattor av olika tjocklekar för att generera mikrostrukturvariationen. Mikrostrukturundersökning, samt drag- och hårdhetsprov gjordes på de gjutna plattorna. Resultaten visade att en högre ferritfraktion, grafitpartikelantal och sträckgräns i den högkisellegerade GJS-500-14-sorten jämfört med GJS-500-7. För att studera förhållandet mellan mikrostrukturell variation och spännings-töjningsbeteendet på makroskala, modellerades detta med hjälp av Ludwigson-ekvationen. De erhållna spännings-töjningsegenskaperna modellerades baserat på mikrostrukturell karaktäristika genom multipel linjärregression och variansanalys (ANOVA). Modellerna visade att kiselhalt, grafitpartikelantal, ferritfraktion och porfraktion var de viktigaste bidragande faktorerna. Modellerna implementerades i ett simuleringsprogram för gjutningsprocessen. Resultatet från simuleringen validerades med hjälp av experimentella data som inte ingick i underlaget för regressionsanalysen. Detta möjliggjorde att prediktera spännings-töjningsbeteendet och dess variation hos gjutna segjärns komponenter med liknande sammansättning och gjutna tjocklekar som användes i denna studie. För att kunna undersöka deformationsbeteendet på mikroskala utvecklades en metod för kvantitativ mätning av töjning i mikrostrukturen, genom DIC-tekniken (digital image correlation) tillsammans med in-situ dragprovning. I denna metod utvecklades en grop-etsningsprocess för att generera ett slumpvis prickmönster, vilket möjliggjorde DIC-töjningsmätning i matrisen och i området mellan grafitpartiklarna med tillräcklig upplösning. Metoden validerades genom benchmarking av den uppmätta sträckgränsen mot materialets makroskopiska sträckgräns mätt med konventionell dragprovning. Det mikrostrukturella deformationsbeteendet under dragbelastning karakteriserades. Under elastisk deformation avslöjade töjningsmönstret en heterogen töjningsfördelning i mikrostrukturen, och bildandet av skjuvband mellan grafitpartiklar. Sprickbildning initierades vid låg spänning och redan vid de spänningsnivåer som ligger vis ”knät” på dragprovningskurvan, vilket indikerar energidissipering genom både begynnande plastisk deformation och sprickbildning. Den lokala töjningen vis sprickinitiering skedde då den lokala töjningen översteg 2%, vilket indikerar att detta skulle kunna vara en tröskelnivå för den töjning som erfordras för initiering av mikro-sprickor. En kontinuum Finita Element (FE) modell utvecklades för att prediktera töjningen hos ett segjärn och dess fördelning i segjärns mikrostruktur. Materialparametrarna för denna modell optimerades genom att anpassa parametrarna i Ramberg-Osgood ekvationen. De predikterade töjningsfördelningarna jämfördes med de experimentell uppmätta töjningsmönstren uppmätta med DIC, både kvalitativt och kvantitativt. Töjningsmönstren överensstämde i stor utsträckning, vilket resulterade i att modellerna kunde anses vara validerade på mikronivå. För att kunna mäta töjningsmönster under dynamiska förlopp på mikronivå utvecklades en metod för att skapa prickmönster och att utföra in-situ CT provning i ett svepeletronmikroskop (SEM). Prickmönstret skapades genom avverkning med en fokuserad jonstråle (FIB), och provades på det ferritiska segjärnet (GJS-500-14 grad). Resultaten visade att maximal töjningskoncentration fanns i närheten av mikrosprickorna, framförallt framför sprickspetsen.

With further development of high-power accelerators and nuclear reactors, there is a strong demand for structural materials that can withstand extreme operational conditions, e.g., large heat loads, mechanical and thermal stresses, high intensity and long-term ion irradiation. Carbon-based materials show excellent thermal transport properties and thus efficient heat dissipation required for such applications. Under ion beam irradiation, graphite also has the advantage of lower stopping power and lower radiation induced activation compared to metals. For these reasons, polycrystalline graphite is commonly used in extreme radiation environments, e.g. beam dumps. In the past, neutron-irradiation effects in graphite have been studied in detail, whereas data on material behavior under exposure to high-energy ion beams is scarce. This thesis focuses on changes of structural and thermophysical properties induced by swift heavy ion irradiation in well-oriented flexible graphite (FG) and in fine-grained isotropic polycrystalline graphite (PG). To investigate radiation-induced degradation processes, graphite samples were irradiated with 4.8 and 5.9 MeV/u 12C, 48Ca, 129Xe, 197Au, and 238U ions with fluences up to ~2×10^14 ions/cm2 at the UNILAC accelerator of the GSI Helmholtz Centre for Heavy Ion Research, Darmstadt. Structural transformations along the ion range were monitored by Raman spectroscopy complemented by scanning electron microscopy. The corresponding modifications of thermophysical properties were characterized using laser flash analysis and frequency domain photothermal radiometry. The response of FG and PG to high-energy ion beams is shown to be quite different, which is ascribed to the different initial microstructure and microtexture of these graphite materials. Radiation damage in flexible graphite follows the trend of the nuclear energy loss and yields a weak or no correlation with the electronic energy loss up to 30 keV/nm. The density of point defects produced via elastic collisions monotonously increases along the ion range and causes a pronounced thermal diffusivity degradation from ~550 down to 50 mm2/s for the Au ion irradiation at a fluence of ~1×10^14 ions/cm2. In contrast, in polycrystalline graphite, both nuclear and electronic (above a certain threshold) energy loss contribute to material modifications. Raman spectroscopy reveals the same type of damage for low Z (Ca) and high Z (Au, U) ions at the end of the ion range (last ~15 µm), where the nuclear energy loss is maximal. Within the range section dominated by the electronic energy loss, the irradiation with Au and U ions (high energy loss of 20-25 keV/nm) causes significant disordering, crystallite refinement and misalignment as well as partial amorphization. At the highest applied fluence of 5×10^13 ions/cm2, this leads to a structure similar to glassy carbon. Exposure to Ca ions of the same fluence produces just a slight increase of the defect density. The corresponding drop of the thermal diffusivity is from 80 mm2/s (virgin) to ~5 mm2/s for Au ions and to ~70 mm2/s for Ca ions. Damage cross-sections in both graphite materials are calculated based on the evolution of the Raman parameters and thermophysi-cal properties as a function of fluence. Raman parameters assigned to the lattice disorder and thermal diffusivity values show a strong correlation, providing the possibility to estimate heat transfer properties of graphite materials by means of Raman spectroscopy.

The search for alternative methods of synthesizing cubic boron nitride (cBN), one of the hardest known materials, at low thermo-baric conditions has stimulated considerable research interest due to its great potential for numerous practical industrial applications. The practical applications are motivated by the material’s amazing combination of extraordinarily superior properties. The cBN phase is presently being synthesized from graphite-like boron nitride modifications at high thermo-baric conditions in the presence of catalytic solvents or by ion–beam assisted (chemical and physical) deposition methods. However, the potential and performance of cBN have not been fully realized largely due to central problems arising from the aforementioned synthesis methods. The work reported in this dissertation is inspired by the extensive theoretical investigation of the influence of defects in a ecting the transformation of the hexagonal boron nitride (hBN) phase to the cBN phase that was carried out by Mosuang and Lowther (Phys Rev B 66, 014112 (2002)). From their investigation, using an ab-initio local density approach, for the B, C, N, and O simple defects in hBN, they concluded that the defects introduced into hBN could facilitate a low activation–energy hexagonal-to-cubic boron nitride phase transformation, under less extreme conditions. We use ion implantation as a technique of choice for introducing ‘controlled’ defects into the hot–pressed polycrystalline 99.9% hBN powder samples. The reasons are that the technique is non–equilibrium (not influenced by dilusion laws) and controllable, that is the species of ions, their energy and number introduced per unit area can be changed and monitored easily. We investigate the structural modifications of hBN by ion implantation. Emphasis is given to the possibilities of influencing a low activation–energy hBN-to-cBN phase transformation. The characterization of the structural modifications induced to the hBN samples by implanting with He+ ions of energies ranging between 200 keV and 1.2 MeV, at fluences of up to 1.0 1017 ionscm2, was accomplished by correlating results from X-Ray Di raction (XRD), micro-Raman (-Raman) spectroscopy measurements, and two-dimensional X-Y Raman (2D-Raman) mapping measurements. The surface to pography of the samples was investigated using Scanning Electron Microscopy (SEM). E orts to use Surface Brillouin Scattering (SBS) were hampered by the transparency of the samples to the laser light as well as the large degree of surface roughness. All the implantations were carried out at room temperature under high vacuum. 2D-Raman mapping and -Raman spectroscopy measurements done before and after He+ ion irradiation show that an induced hBN-to-cBN phase transformation is possible: nanocrystals of cBN have been observed to have nucleated as a consequence of ion implantation,the extent of which is dictated by the fluences of implantation. The deviationof the measured spectra from the Raman spectra of single crystal cBN is expected, has been observed before and been attributed to phonon confinement e ects. Also observed are phase transformations from the pre-existing hBN modification to: (a) the amorphous boron nitride (aBN), (b) the rhombohedral boron nitride (rBN) modifications, (c) crystalline and amorphous boron clusters, which are a result of the agglomeration of elementary boron during and immediately after ion implantation. These transformations were observed at high energies. Unfortunately, the XRD measurements carried out could not complement the Raman spectroscopy outcomes probably because the respective amounts of the transformed materials were well below the detection limit of the instrument used in the former case.

博士
國立清華大學
原子科學系
91
Ion Beam is a powerful tool in Material Research due to the unique capability of analysis and modification of material. The thesis reports my research works using the ion beam produced from accelerators in Tsing Hua University, including RBS/w Channeling, Elastic Recoiled Detection, Particle Induced X-ray Emission, Ion Implantation,αradioactive source preparation by recoiled implantation and stopping power measurement using partial coated Si detector. We have successfully built a complete detection and analysis system for the studies of RBS/w Channeling, Elastic Recoiled Detection, and Particle Induced X-ray Emission. The results of Ion Implantation andαradioactive source preparation show the potential for further applications and researches of material science.

碩士
逢甲大學
纖維與複合材料學系
101
Recently, the demand for energy is increasing due to advanced technology development. The energy density, output power, effective duration and safety of Li-ion battery is much better than those of tradition al battery. The production of Li-ion battery becomes the main trend of industry, from cumbrous to thin and light. Wherein the lithium-ion battery cathode materials of lithium iron phosphate (LiFePO4) has attracted much attention, because of its good thermal stability, affordability, safety, stability of functioning voltage, non-toxic and flat voltage profile, etc. These advantage have actually been used in electric vehicles. However, it still has a low ionic diffusivity and poor electronic conductivity, therefore many researchers add metal which decreases the particle size to improve its performance. In this study, particle size of lithium iron phosphate was reduced after milling, the surface thereon was coated with nano-silver. Here, we are explore and discuss the benefits of nanosilver on transferring electrics and Li-ion. A polyol method was used in this study, we added silver nitrate (AgNO3) in the Ethylene Glycol (EG) at 140 ℃, and then added polyvinyl pyrrolidone (PVP) as a protective agent. After that, we added glucose reaction for 2 hours. Finally the surface of lithium iron phosphate was coated with reduced silver particles. After drying, a slurry composition of powders in proportion of Lithium iron phosphate- silver: Carbon black: PVDF ratio is 75:15:10 wt% and coated to the cathode electrode for cyclic voltammetry tests. Experimental results showed that lithium iron phosphate powder was milled with zirconium beads 200 g in dimethyl sulfoxide (DMSO) solvent at 800 rpm for 1 hour. Its particle size was 234.7 nm that decreased 79.2 % compared with non-milled powder. As PVP protective agent was added, the uniformity of particle size and surface coating of lithium iron phosphate coated with nano silver was found in PVP of 10K. After 300 ℃ and 0.5 hr thermal treatment, the PVP polymer content with poor electric conductivity decreased 46.8 %. The capacity of capacitor was 84.24 mAh / g which increased capacitance of 15.80% compared to lithium iron phosphate without adding nano silver particles. Therefore, lithium iron phosphate coated with nano silver particles can improve the lithium ion diffusion and decrease electric conductivity.

In der vorliegenden Arbeit wird erstmals das QQDS-Magnetspektrometer für die höchstauflösende Ionenstrahlanalytik leichter Elemente am Helmholtz-Zentrum Dresden-Rossendorf umfassend vorgestellt. Zusätzlich werden sowohl alle auf die Analytik Einfluss nehmenden Parameter untersucht als auch Methoden und Modelle vorgestellt, wie deren Einfluss vermieden oder rechnerisch kompensiert werden kann. Die Schwerpunkte dieser Arbeit gliedern sich in fünf Bereiche. Der Erste ist der Aufbau und die Inbetriebnahme des QQDS-Magnetspektrometers, der zugehörige Streukammer mit allen Peripheriegeräten und des eigens für die höchstauflösende elastische Rückstoßanalyse entwickelten Detektors. Sowohl das umgebaute Spektrometer als auch der im Rahmen dieser Arbeit gebaute Detektor wurden speziell an experimentelle Bedingungen für die höchstauflösende Ionenstrahlanalytik leichter Elemente angepasst und erstmalig auf einen routinemäßigen Einsatz hin getestet. Der Detektor besteht aus zwei Komponenten. Zum einen befindet sich am hinteren Ende des Detektors eine Bragg-Ionisationskammer, die zur Teilchenidentifikation genutzt wird. Zum anderen dient ein Proportionalzähler, der eine Hochwiderstandsanode besitzt und direkt hinter dem Eintrittsfenster montiert ist, zur Teilchenpositionsbestimmung im Detektor. Die folgenden zwei Schwerpunkte beinhalten grundlegende Untersuchungen zur Ionen-Festkörper-Wechselwirkung. Durch die Verwendung eines Magnetspektrometers ist die Messung der Ladungszustandsverteilung der herausgestreuten Teilchen direkt nach einem binären Stoß sowohl möglich als auch für die Analyse notwendig. Aus diesem Grund werden zum einen die Ladungszustände gemessen und zum anderen mit existierenden Modellen verglichen. Außerdem wird ein eigens entwickeltes Modell vorgestellt und erstmals im Rahmen dieser Arbeit angewendet, welches den ladungszustandsabhängigen Energieverlust bei der Tiefenprofilierung berücksichtigt. Es wird gezeigt, dass ohne die Anwendung dieses Modells die Tiefenprofile nicht mit den quantitativen Messungen mittels konventioneller Ionenstrahlanalytikmethoden und mit der Dickenmessung mittels Transmissionselektronenmikroskopie übereinstimmen, und damit falsche Werte liefern würden. Der zweite für die Thematik wesentliche Aspekt der Ionen-Festkörper-Wechselwirkung, sind die Probenschäden und -modifikationen, die während einer Schwerionen-bestrahlung auftreten. Dabei wird gezeigt, dass bei den hier verwendeten Energien sowohl elektronisches Sputtern als auch elektronisch verursachtes Grenzflächendurchmischen eintreten. Das elektronische Sputtern kann durch geeignete Strahlparameter für die meisten Proben ausreichend minimiert werden. Dagegen ist der Einfluss der Grenzflächendurchmischung meist signifikant, so dass dieser analysiert und in der Auswertung berücksichtigt werden muss. Schlussfolgernd aus diesen Untersuchungen ergibt sich für die höchstauflösende Ionenstrahlanalytik leichter Elemente am Rossendorfer 5-MV Tandembeschleuniger, dass die geeignetsten Primärionen Chlor mit einer Energie von 20 MeV sind. In Einzelfällen, wie zum Beispiel der Analyse von Bor, muss die Energie jedoch auf 6,5 MeV reduziert werden, um das elektronische Sputtern bei der notwendigen Fluenz unterhalb der Nachweisgrenze zu halten. Der vierte Schwerpunkt ist die Untersuchung von sowohl qualitativen als auch quantitativen Einflüssen bestimmter Probeneigenschaften, wie beispielsweise Oberflächenrauheit, auf die Form des gemessenen Energiespektrums beziehungsweise auf das analysierte Tiefenprofil. Die Kenntnis der Rauheit einer Probe an der Oberfläche und an den Grenzflächen ist für die Analytik unabdingbar. Als Resultat der genannten Betrachtungen werden die Einflüsse von Probeneigenschaften und Ionen-Festkörper-Wechselwirkungen auf die Energie- beziehungsweise Tiefenauflösung des Gesamtsystems beschrieben, berechnet und mit der konventionellen Ionenstrahlanalytik verglichen. Die Möglichkeiten der höchstauflösenden Ionenstrahlanalytik werden zudem mit den von anderen Gruppen veröffentlichten Komplementärmethoden gegenübergestellt. Der fünfte und letzte Schwerpunkt ist die Analytik leichter Elemente in ultradünnen Schichten unter Berücksichtigung aller in dieser Arbeit vorgestellten Modelle, wie die Reduzierung des Einflusses von Strahlschäden oder die Quantifizierung der Elemente im dynamischen Ladungszustandsnichtgleichgewicht. Es wird die Tiefenprofilierung von Mehrschichtsystemen, bestehend aus SiO2-Si3N4Ox-SiO2 auf Silizium, von Ultra-Shallow-Junction Bor-Implantationsprofilen und von ultradünnen Oxidschichten, wie zum Beispiel High-k-Materialien, demonstriert.
In this thesis the QQDS magnetic spectrometer that is used for high resolution ion beam analysis (IBA) of light elements at the Helmholtz-Zentrum Dresden-Rossendorf is presented for the first time. In addition all parameters are investigated that influence the analysis. Methods and models are presented with which the effects can be minimised or calculated. There are five focal points of this thesis. The first point is the construction and commissioning of the QQDS magnetic spectrometer, the corresponding scattering chamber with all the peripherals and the detector, which is specially developed for high resolution elastic recoil detection. Both the reconstructed spectrometer and the detector were adapted to the specific experimental conditions needed for high-resolution Ion beam analysis of light elements and tested for routine practice. The detector consists of two compo-nents. At the back end of the detector a Bragg ionization chamber is mounted, which is used for the particle identification. At the front end, directly behind the entrance window a proportional counter is mounted. This proportional counter includes a high-resistance anode. Thus, the position of the particles is determined in the detector. The following two points concern fundamental studies of ion-solid interaction. By using a magnetic spectrometer the charge state distribution of the particles scattered from the sample after a binary collision is both possible and necessary for the analysis. For this reason the charge states are measured and compared with existing models. In addition, a model is developed that takes into account the charge state dependent energy loss. It is shown that without the application of this model the depth profiles do not correspond with the quantitative measurements by conventional IBA methods and with the thickness obtained by transmission electron microscopy. The second fundamental ion-solid interaction is the damage and the modification of the sample that occurs during heavy ion irradiation. It is shown that the used energies occur both electronic sputtering and electronically induced interface mixing. Electronic sputtering is minimised by using optimised beam parameters. For most samples the effect is below the detection limit for a fluence sufficient for the analysis. However, the influence of interface mixing is so strong that it has to be included in the analysis of the layers of the depth profiles. It is concluded from these studies that at the Rossendorf 5 MV tandem accelerator chlorine ions with an energy of 20 MeV deliver the best results. In some cases, such as the analysis of boron, the energy must be reduced to 6.5 MeV in order to retain the electronic sputtering below the detection limit. The fourth focus is the study of the influence of specific sample properties, such as surface roughness, on the shape of a measured energy spectra and respectively on the analysed depth profile. It is shown that knowledge of the roughness of a sample at the surface and at the interfaces for the analysis is needed. In addition, the contribution parameters limiting the depth resolution are calculated and compared with the conventional ion beam analysis. Finally, a comparison is made between the high-resolution ion beam analysis and complementary methods published by other research groups. The fifth and last focus is the analysis of light elements in ultra thin layers. All models presented in this thesis to reduce the influence of beam damage are taken into account. The dynamic non-equilibrium charge state is also included for the quantification of elements. Depth profiling of multilayer systems is demonstrated for systems consisting of SiO2-Si3N4Ox-SiO2 on silicon, boron implantation profiles for ultra shallow junctions and ultra thin oxide layers, such as used as high-k materials.

碩士
國立成功大學
機械工程學系
89
The material structure , mechanical properties and tribological performances of Diamond-like carbon (a-C:H) and nitrogen-containing diamond-like carbon (a-C:N:H) films deposited by ion-beam process were studied in this thesis. The distribution of film residual stress were obtained also using the theory developed in the content. Besides, local Young’s modulus of a-C:H:N thin film can be obtained by measuring the length of film wrinkle. About scratch test, the relationship of friction coefficient and scratch length in a-C:H:N thin films could be divided into four major regions distinctly. Therefore, the critical normal load could also be decided by the criterion discussed above. 　　The films’ structure has been analysed by Raman and X-ray photoelectron spectroscopy. The optical properties, index of refraction and extinction coefficient, were measured by ellipsometer. In the study of tribological performance, aluminum ring and stainless steel flat substrate were used as upper and lower specimen respectively. In the results of experiments, nitrogen doped in Diamond-like thin film will increase the amount of sp2 bond and decrease average internal stress inside the film simultaneously.

碩士
國立成功大學
機械工程學系碩博士班
90
The adhesion effects to the load-depth curves of nano-indentation test and the theoretical relation of micro/nano hardness are researched in this study. The effect of nitrogen containing and film thickness to the a-C:H and a-H(N) diamond like carbon film structures and micro/nano mechanical and tribological properties is involved, too. The hardness and Young’s modulus are measured by nano-indentation performed by NanoTest, and the capillary attraction and van der Wall force calculated in order to assess the adhesion effect of different nitrogen containing and film thickness. In the residual stresses of films, the profile data are measured before and after coating by 3-D profilemeter and the radius of curvature are calculated by regression; therefore the residual stress can be obtained by the radius of curvature before and after coating according to the stress theory and the effect of the residual stress can be discussed. In measuring tribological properties, we scanned and scratched sample surfaces by Scanning Probe Microscope and NanoTest with different speeds and loads. In examining samples, we measured composition and bonding by ESCA and Raman spectrum, and measured the optical properties by Ellipsometer. According to the experimental results, the adhesion effects to the load-depth curves are significant as the indentation depth is lower than 50 nm, and the effect gets larger as depth decreases. And we found that the very thin (about 50 nm) diamond like carbon film has large hardness and Young’s modulus and excellent anti-wear property and surface roughness. There are two characters in this study: (1) considering the capillary attraction and van der Wall force under nano-scale and observing the fact that the hardness without considering adhesion effect is much larger; (2) Obtaining hardness by the energy method and considering the effects of elastic work due to elastic recovery and adhesion work due to adhesive forces.