To see the other types of publications on this topic, follow the link: Electron backscattering.
Dissertations / Theses on the topic 'Electron backscattering'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 27 dissertations / theses for your research on the topic 'Electron backscattering.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Kapraun, Dustin F. "Monte Carlo Techniques for Predicting Electron Backscattering." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20011205-133453.
Full textAbstract:
KAPRAUN, DUSTIN FREDERICK. Monte Carlo Techniques for Predicting Electron Backscattering. (Under the direction of Dr. H.T. Tran.) The objective of this research is to develop and implement an algorithm that can accurately and efficiently predict backscatter yield and the trajectories and energies of electrons backscattered by solids. Taking into account the energy and direction of an incident electron, as well as the atomic number, atomic mass and density of the solid, our program determines a statistically reasonable path for the electron through the solid via Monte Carlo techniques. Such a model can and has been used in a variety of applications, but in this case we are interested in predicting the behavior of backscattered electrons. When applied to large numbers of electrons, the program provides statistically accurate results. In particular, excellent agreement is seen between the backscatter coefficients measured by Hunger and Kuchler and those predicted by our program. Furthermore, the angular distributions and energy distributions of backscattered electrons predicted by our program are consistent with those measured by Bishop.
2
Marmitt, Gabriel Guterres. "Metal oxides of resistive memories investigated by electron and ion backscattering." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/170451.
Full textAbstract:
O memristor é um dos dispositivos mais promissores sendo estudados para múltiplos usos em sistemas eletrônicos, com aplicações desde memórias não voláteis a redes neurais artificiais. Seu funcionamento é baseado na formação e ruptura de filamentos condutores nanométricos, o que altera drasticamente a resistência do dispositivo. Estes filamentos são formados pela acumulação de vacâncias de oxigênio, portanto um profundo entendimento da autodifusão de oxigênio nestes sistemas é necessário. Medidas acuradas da difusão em óxidos metálicos foi obtida com o desenvolvimento de uma análise quantitativa do espectro em energia de elétrons retroespalhados. A inovadora técnica de RBS de elétrons (ERBS) utiliza elétrons de alta energia ( 40 keV) para investigar a região próxima a superfície (10–100 nm). Medidas da região de alta perda de energia – chamada de Spectroscopia de Perda de Alta-Energia de Elétrons Refletidos (RHEELS) – também exibe características da estrutura eletrônica dos materiais. Um procedimento cuidadoso para o ajuste de espectros de ERBS foi desenvolvido, e então aplicado na análise de amostras multi camada de Si3N4/TiO2, e medidas de band gap de alguns óxidos, como SiO2, CaCO3 e Li2CO3. Simulações de Monte Carlo foram empregadas no estudo dos efeitos de espalhamento múltiplo nos espectros de ERBS, e uma descrição dielétrica dos espalhamentos inelásticos extendeu as simulação para também considerarem os picos de exitação plasmônica observados em RHEELS. Estas ferramentas de análise foram integradas em um pacote chamado PowerInteraction. Com o uso deste, uma série de medidas de autodifusão de oxigênio em TiO2 foram conduzidas. As amostras eram compostas por dois filmes de TiO2 depositados por sputtering, um dos quais enriquecido com isótopo 18 de oxigênio. Após tratamentos térmicos, perfis de difusão foram obtidos pelo rastreio das concentrações relativas dos isótopos de oxigênio nos dois filmes. Do comportamento logarítmico dos coeficientes de difusão em relação à temperatura, uma energia de ativação de 1.05 eV para a autodifusão de oxigênio em TiO2 foi obtida. Análises por feixes de íons, como RBS e NRA/NRP (Análise/Perfilometria por Reação Nuclear), também forneceram informações complementares.The memristor is one of the most promising devices being studied for multiple uses in future electronic systems, with applications ranging from nonvolatile memories to artificial neural networks. Its working is based on the forming and rupturing of nano-scaled conductive filaments, which drastically alters the device’s resistance. These filaments are formed by oxygen vacancy accumulation, hence a deep understanding of the self-diffusion of oxygen in these systems is necessary. Accurate measurements of oxygen self-diffusion on metal oxides was achieved with the development of a quantitative analysis of the energy spectrum of the backscattering of electrons. The novel technique called Electron Rutherford Backscattering Spectroscopy (ERBS) uses the scattering of high energy electrons ( 40 keV) to probe the sample’s near surface (10–100 nm). Measurements of the high energy loss region – called Reflection High-Energy Electron Loss Spectroscopy (RHEELS) – also exhibit characteristics of the material’s electronic structure. A careful procedure was developed for the fitting of ERBS spectra, which was then applied on the analysis of multi-layered samples of Si3N4/TiO2, and measurements of the band gap of common oxides, such as SiO2, CaCO3 and Li2CO3. Monte Carlo simulations were employed to study the effects of multiple elastic scatterings in ERBS spectra, and a dielectric function description of inelastic scatterings extended the simulation to also consider the plasmon excitation peaks observed in RHEELS. These analysis tools were integrated into a package named PowerInteraction. With its use, a series of measurements of oxygen self-diffusion in TiO2 were conducted. The samples were composed of two sputtered deposited TiO2 layers, one of which was enriched with the 18 mass oxygen isotope. After thermal annealing, diffusion profiles were obtained by tracking the relative concentration of oxygen isotopes in both films. From the logarithmic temperature dependence of the diffusion coefficients, an activation energy of 1.05 eV for oxygen self-diffusion in TiO2 was obtained. Common ion beam analysis, such as RBS and NRA/NRP (Nuclear Reaction Analysis/Profiling), were also used to provide complementary information.
3
Lehan, John Philip. "Microstructural investigations of optical coatings by backscattering spectrometry, electron diffraction, and spectrophotometry." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/184997.
Full textAbstract:
Backscattering spectrometry with MeV ⁴He ion beams is investigated as a tool for determining composition with applications to optical coatings. Equations for the compositional analysis of thin films are reviewed. The effect of nuclear charge screening on compositional analysis by MeV ⁴He beams is discussed and examples involving the lanthanide trifluorides illustrate the importance of this correction to avoid possibly erroneous conclusions about sample composition. High probe beam energy is also briefly discussed as a method of reducing the overlap of peaks in backscattering spectra which reduces the technique's accuracy. Complications such as non-Rutherford scattering cross sections for light elements are addressed and an example given. The application of backscattering spectrometry to the depth profiling of elemental constituents in thin films is discussed. It is found that the backscattering spectrum itself provides a reasonable depth profile; however, its depth resolution is limited by the energy resolution of the detection system and energy straggling of the probe beam in the solid. In addition, the depth profile suffers from considerable noise. A method is derived using the principle of maximum likelihood which allows hypothetical depth profiles to be tested and the effects of energy straggling and detection system resolution to be separated from the depth profile. Several examples involving two hypothetical depth profile models are presented. Finally, backscattering spectrometry is combined with scanning electron microscopy, transmission electron microscopy, electron diffraction, x-ray photoelectron spectroscopy, and spectrophotometry in a microstructural survey of hafnium dioxide optical coatings deposited by electron beam evaporation and ion-assisted deposition (IAD). It is found that hafnium dioxide films deposited at temperatures below 300°C are amorphous and exhibit a negative optical inhomogeneity. The refractive index as well as the inhomogeneity are strongly influenced by the oxygen present during film deposition. The inhomogeneity can be removed by IAD which also increases the refractive index of the film. In addition, low energy IAD is found to increase the refractive of the films without affecting the inhomogeneity. This is explained by the preferential sputtering of hydroxide from the growing film surface by the bombarding ions.
4
Thiagarajan, Kannan. "Tight-binding calculations of electron scattering rates in semiconducting zigzag carbon nanotubes." Licentiate thesis, Mittuniversitetet, Institutionen för informationsteknologi och medier, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-13162.
Full textAbstract:
The technological interest in a material depends very much on its electrical, magnetic, optical and/or mechanical properties. In carbon nanotubes the atoms form a cylindrical structure with a diameter of the order 1 nm, but the nanotubes can be up to several hundred micrometers in length. This makes carbon nanotubes a remarkable model for one-dimensional systems. A lot of efforts have been dedicated to manufacturing carbon nanotubes, which is expected to be the material for the next generation of devices. Despite all the attention that carbon nanotubes have received from the scientific community, only rather limited progress has been made in the theoretical understanding of their physical properties. In this work, we attempt to provide an understanding of the electron-phonon and electron-defect interactions in semiconducting zigzag carbon nanotubes using a tight-binding approach. The electronic energy dispersion relations are calculated by applying the zone-folding technique to the dispersion relations of graphene. A fourth-nearest-neighbour force constant model has been applied to study the vibrational modes in the carbon nanotubes. Both the electron-phonon interaction and the electron-defect interaction are formulated within the tight-binding approximation, and analyzed in terms of their quantum mechanical scattering rates. Apart from the scattering rates, their components in terms of phonon absorption, phonon emission, backscattering and forward scattering have been determined and analyzed. The scattering rates for (5,0), (7,0), (10,0), (13,0) and (25,0) carbon nanotubes at room temperature and at 10K are presented and discussed. The phonon scattering rate is dependent on the lattice temperature in the interval 0-0.17 eV. We find that backscattering and phonon emission are dominant over forward scattering and phonon absorption in most of the energy interval. However, forward scattering and phonon absorption can be comparable to backscattering and phonon emission in limited energy intervals. The phonon modes associated with each peak in the electron-phonon scattering rates have been identified, and the similarities in the phonon scattering rates between different nanotubes are discussed. The dependence of the defect scattering rate on the tube diameter is similar to that of the phonon scattering rate. Both the phonon and the defect scattering rates show strong dependence on the tube diameter (i.e., the scattering rate decreases as a function of the index of the nanotube). It is observed that the backscattering and forward scattering for electrons interacting with defects occur with same frequency at all energies, in sharp contrast to the situation for phonon scattering. It is demonstrated that the differences in the scattering rate between different tubes are mainly due to the differences in their band structures.
5
LOW, MARJORIE. "Estudo do desenvolvimento da textura durante a recristalização primária de aços ferríticos por difração de raios X e difração de elétrons retroespalhados." reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11449.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:52:01Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:57:53Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
6
SERNA, MARILENE M. "Estudo comparativo da analise de macrotextura pelas tecnicas de difracao de raios X e difracao de eletrons retroespalhados." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11013.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:46:56Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:09:47Z (GMT). No. of bitstreams: 1 09060.pdf: 8685574 bytes, checksum: 4cca556c554e4dce4f2f896a6cd6f9fd (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
7
Annan, Kofi Ahomkah. "Effect of hot working characteristics on the texture development in AISI 430 and 433 ferritic stainless steel." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/25436.
Full textAbstract:
The last seven hot rolling passes of the ferritic stainless steels (FSS) AISI 430 and AISI 433 (the latter an Al-added variant of 430) were simulated on Gleeble-1500D® and Gleeble-3800TM® thermo-mechanical simulators to investigate the effect of temperature, strain rate and inter-pass time on the development of texture in these steel grades and its subsequent influence on ridging. The compression tests were carried out over a wide range of strain rates (0.1 s-1 to 5 s-1, 25 s-1 and 50 s-1) and temperatures (1100 to 820 oC) with different inter-pass times (2 s, 10 s, 20 s and 30 s). The transition temperature from dynamic recrystallization (which may introduce a texture change) to dynamic recovery (in which no texture changes are expected) was determined by examining the relationship between the mean flow stress and the deformation temperature in multi-pass tests. Both macrotexture (XRD) and microtexture (EBSD) analyses were employed to characterise and study the texture present in these steels. It was found that the texture in the central layer of the compressed sample is a strong recrystallization-type. The through-thickness textural and microstructural banding was found to be responsible for ridging in these grades of stainless steels. Dynamic recrystallization which promotes the formation of the desired ã-fibre texture leading to high ductility, formability and eventually reduction or elimination of ridging, was found to occur in both AISI 430 and AISI 433 at high temperatures, low strain rates and longer inter-pass times with multi-pass testing. Generally AISI 433 has a stronger gamma texture developed than the AISI 430 when hot rolled under similar conditions, which leads to improved ductility and less ridging in AISI 433 than AISI 430.Dissertation (MSc)--University of Pretoria, 2012.
Materials Science and Metallurgical Engineering
unrestricted
8
Nxusani, Ezo. "Synthesis and analysis of Novel Platinum group Metal Chalcogenide Metal Quantum Dot and Electrochemical Markers." University of the Western Cape, 2018. http://hdl.handle.net/11394/6424.
Full textAbstract:
Magister Scientiae - MSc (Chemistry)Although cadmium and lead chalcogenide quantum dot have excellent optical and photoluminescent properties that are highly favorable for biological applications, there still exists increasing concerns due to the toxicity of these metals. We, therefore, report the synthesis of new aqueous soluble IrSe quantum dot at room temperature utilizing a bottom-up wet chemistry approach. NaHSe and H2IrCl6 were utilized as the Se and Ir source, respectively. High-resolution transmission electron microscopy reveals that the synthesized 3MPA-IrSe Qd are 3 nm in diameter. The characteristics and properties of the IrSe Qd are investigated utilizing, Selected Area electron diffraction, ATR- Fourier Transform Infra-Red Spectroscopy, Energy Dispersive X-ray spectroscopy, Photoluminescence, Cyclic Voltammetry and chronocoulometry. A 3 fold increase in the optical band gap of IrSe quantum dot in comparison to reported bulk IrSe is observed consistent with the effective mass approximation theory for semiconductor materials of particles sizes < 10 nm. The PL emission of the IrSe quantum dot is at 519 nm. Their electro-activity is studied on gold electrodes and exhibit reduction and oxidation at - 107 mV and +641 mV, with lowered reductive potentials. The synthesized quantum dot are suitable for low energy requiring electrochemical applications such as biological sensors and candidates for further investigation as photoluminescent biological labels.
9
Magogodi, Steven Mothibakgomo. "Hydrogen storage capacity of the Ti-Pd multilayer systems." University of the Western Cape, 2020. http://hdl.handle.net/11394/7711.
Full textAbstract:
>Magister Scientiae - MScHydrogen has high energy density and it is regarded as the future energy carrier. Hydrogen can be stored as a gas in high-pressure cylinders, as a liquid in cryogenic tanks and as a solid in metal hydrides. The storage of hydrogen in gas and liquid form has many limitations. Light metal hydrides show high energy density and are a promising and more practical mode of hydrogen storage. In particular, titanium and its alloys are promising metal hydrides for hydrogen storage due to their high affinity to hydrogen. The aim of this study is to investigate the effect of thermal annealing on hydrogen storage capacity of Ti-Pd multilayer systems. Ti-Pd multilayer films were prepared on CP-Ti (commercial pure Ti) and Ti6Al4V substrates using an electron beam evaporator equipped with a thickness monitor. The sequential deposition of layers Pd(50nm)/Ti(25nm)/Pd(50nm) was done at a constant deposition rate of 0.6 Å/s. The first batch of samples were thermally annealed at 550 °C in vacuum for two hours, the second batch of samples were annealed at 550 oC under H2(15%)/Ar(85%) gas mixture for two hours and the third series of samples was annealed under pure H2 gas at 550 oC for one hour. SEM showed relatively homogeneous and smooth topography of surfaces in as-deposited samples, while a rough textured surface was observed in both samples annealed under vacuum and under H2/Ar gas mixture. The samples annealed under pure H2 gas did not show any sign of crystallites grow but instead a relatively smooth surface with sign of etching. XRD revealed structural transformation as evidenced by the presence of PdTi2 phase in samples annealed under vacuum; in samples annealed under the gas mixture Pd2Ti was noted in addition to TiH2 and TiO2. While the TiH2 phase is an indication of hydrogen absorption, the TiPd2 phase suggests intermixing of the deposited layers and the presence of TiO2 is evidence of oxidation. The samples annealed under pure H2 gas showed only TiH2 with no trace of structural transformation. RBS confirmed the intermixing of layers in the samples annealed under vacuum and H2(15%)/Ar(85%) gas mixture, while samples annealed under pure H2 gas did not show any intermixing of layers. ERDA revealed an average H content of ~ 3.5 at.% in CP-Ti and ~6.2 at.% in Ti6Al4V for samples annealed under H2(15%)/Ar(85%) gas mixture. We recorded an hydrogen content of ~19.5 at.% in CP-Ti annealed under pure H2 while ~25.5 at.% was found in Ti6Al4V annealed under the same conditions. When the thickness of the Pd catalyst layers was increased to 100 nm (i.e. Pd (100 nm)/Ti (25 nm)/Pd (100 nm)), only ~ 12.5 at.% and 11.2 at. % hydrogen content was recorded in samples prepared on CP-Ti and Ti6Al4V alloy respectively, both annealed under pure hydrogen for one hour as above.
10
Liebig, Andreas. "Amorphous, Nanocrystalline, Single Crystalline: Morphology of Magnetic Thin Films and Multilayers." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8355.
Full text
11
Gorfu, Paulos. "Untersuchung von Dünnschichtsystemen mittels Elektronenstrahl-Mikroanalyse." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1237375992053-95064.
Full textAbstract:
Die Arbeit beschäftigt sich mit der Erweiterung der für dicke Proben schon mit Erfolg eingesetzten Werkstoffanalytischen Methode Elektronenstrahl-Mikroanalyse (ESMA) mittels Peak/Untergrund-Verhältnissen auf die Analyse von dünnen Schichten (unter 1 μm) zur qualitative und quantitativen Elementanalyse sowie zur Ermittlung von Schichtdicken. Weiterhin wird auf der Basis von einer ESMA-Methode für zwei dünne Schichten auf einem Substrat wird ein Modell zur Ermittlung des Phasenwachstumskoeffizienten für eine intermetallische Phase die sich bei der Diffusion zwischen einer dünnen Schicht und einem Substrat bildet, mittels ESMA-Messungen bei gleichzeitiger Erwärmung der Probe dargestelltThe paper deals with the application of the materials analysis method EPMA by peak-to-background ratios, which is currently being used for the analysis of thick samples successfully, to thin layers (less than 1 μm) for the quantitative element analysis as well as for thickness prediction. In addition a model has been established on the Basis of an EPMA method for two films on a substrate for deriving the phase growth coefficient of an inter-metallic phase which grows during the diffusion between a thin layer and a substrate from EPMA measurements while simultaneously heating the sample
12
Gorfu, Paulos. "Untersuchung von Dünnschichtsystemen mittels Elektronenstrahl-Mikroanalyse." Doctoral thesis, Technische Universität Dresden, 1991. https://tud.qucosa.de/id/qucosa%3A23789.
Full textAbstract:
Die Arbeit beschäftigt sich mit der Erweiterung der für dicke Proben schon mit Erfolg eingesetzten Werkstoffanalytischen Methode Elektronenstrahl-Mikroanalyse (ESMA) mittels Peak/Untergrund-Verhältnissen auf die Analyse von dünnen Schichten (unter 1 μm) zur qualitative und quantitativen Elementanalyse sowie zur Ermittlung von Schichtdicken. Weiterhin wird auf der Basis von einer ESMA-Methode für zwei dünne Schichten auf einem Substrat wird ein Modell zur Ermittlung des Phasenwachstumskoeffizienten für eine intermetallische Phase die sich bei der Diffusion zwischen einer dünnen Schicht und einem Substrat bildet, mittels ESMA-Messungen bei gleichzeitiger Erwärmung der Probe dargestellt.The paper deals with the application of the materials analysis method EPMA by peak-to-background ratios, which is currently being used for the analysis of thick samples successfully, to thin layers (less than 1 μm) for the quantitative element analysis as well as for thickness prediction. In addition a model has been established on the Basis of an EPMA method for two films on a substrate for deriving the phase growth coefficient of an inter-metallic phase which grows during the diffusion between a thin layer and a substrate from EPMA measurements while simultaneously heating the sample.
13
Waterton, Michael. "Characterisation and evolution of the grain boundary network in BCC metals." Thesis, Swansea University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678443.
Full text
14
Chelda, Samir. "Simulation du parcours des électrons élastiques dans les matériaux et structures. Application à la spectroscopie du pic élastique multi-modes MM-EPES." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2010. http://tel.archives-ouvertes.fr/tel-00629659.
Full textAbstract:
La spectroscopie EPES (Elastic Peak Electron Spectroscopy) permet de mesurer le pourcentage he d'électrons rétrodiffusés élastiquement par la surface d'un échantillon soumis à un bombardement électronique. C'est une méthode non destructive et extrêmement sensible à la surface. L'objectif de ce travail est de modéliser le cheminement des électrons élastiques dans la matière grâce à une simulation informatique basée sur la méthode Monte Carlo. Cette simulation contribue de manière essentielle à la connaissance et à l'interprétation des résultats expérimentaux obtenus par spectroscopie EPES. Nous avons, de plus, adapté cette simulation à différentes surfaces transformées à l'échelle micrométrique et nanométrique. A l'aide d'une méthode originale, basée sur une description couche par couche du matériau, j'ai réalisé un programme informatique (MC1) rendant compte du cheminement des électrons élastiques dans les différentes couches du matériau. Le nombre d'électrons ressortant de la surface dépend de nombreux paramètres comme : la nature du matériau à étudier, l'énergie des électrons incidents, l'angle d'incidence, les angles de collection des analyseurs. De plus, je me suis intéressé à l'effet de la rugosité de la surface et j'ai démontré qu'elle joue un rôle déterminant sur l'intensité du pic élastique. Ensuite, grâce à l'association de la spectroscopie EPES et de la simulation Monte Carlo, j'ai déduit les modes de croissance de l'or sur substrat d'argent et de cuivre. Les effets de l'arrangement atomique et des pertes énergétiques de surfaces ont ensuite été étudiés. Pour cela, une deuxième simulation MC2 tenant compte de ces deux paramètres a été réalisée permettant d'étudier les surfaces à l'échelle nanométriques. Ces paramètres jusqu'alors non pris en compte dans notre simulation MC1, joue un rôle essentiel sur l'intensité élastique. Ensuite, j'ai obtenu une formulation simple et exploitable pour l'interprétation des résultats obtenus par la simulation MC2 pour un analyseur RFA. Afin de valider, les différents résultats de la simulationMC2, j'ai réalisé des surfaces de silicium nanostructurées, à l'aide de masques d'oxyde d'alumine réalisés par voie électrochimique. J'ai pu créer des nano-pores par bombardement ionique sous ultravide sur des surfaces de silicium. Afin de contrôler la morphologie de la surface, j'ai effectué de l'imagerie MEB ex-situ. La simulation Monte Carlo développée associée aux résultats EPES expérimentaux permet d'estimer la profondeur, le diamètre et la morphologie des pores sans avoir recours à d'autres techniques ex-situ.Cette simulation MC2 permet de connaître la surface étudiée à l'échelle nanométrique.
15
Moscatelli, Michel. "Role du molybdene dans la dissolution et la passivation d'alliages nickel-molybdene : influence du soufre." Paris 6, 1987. http://www.theses.fr/1987PA066542.
Full textAbstract:
Les effets d'amelioration des capacites de passivation apportees par le molybdene et les effets de depassivation induits par le soufre adsorbe et en solution solide ont ete etudies en milieu h::(2)so::(4) sur des alliages monocristallins a base de nickel contenant 2% et 6% de molybdene, a l'aide de techniques electrochimiques et radiochimiques (traceur s**(35))
16
Do, Ngoc-Long. "Etude de l'oxydation thermique du titane et du zirconium sous irradiation aux ions d'argon dans le domaine du MeV (E ≤ 15 MeV)." Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00780772.
Full textAbstract:
Nous avons montré que l'irradiation aux ions d'argon d'énergie comprise entre 1 et 15 MeV cause des dommages en surface du titane et du zirconium, qui prennent la forme d'une oxydation accélérée et/ou d'une cratérisation dont les effets évoluent en fonction de l'énergie du projectile et de l'atmosphère de recuit (température et pression), simulant les conditions environnementales représentatives de l'interface gaine/combustible d'un réacteur REP. Par AFM, nous avons montré que la surface du titane et du zirconium était attaquée par bombardement aux ions d'argon, à haute température (jusqu'à 500°C) en milieu faiblement oxydant (sous pression d'air sec raréfié comprise entre 5,7 10-5 Pa et 5 10-3 Pa) et à une dose moyenne fixée à environ 5 1014 ions.cm-2. On observe ainsi la formation de cratères nanométriques sur toute la surface du titane irradié entre 2 et 9 MeV et celle du zirconium irradié à 4 MeV, dont les caractéristiques varient en fonction de la température et de la pression. Dans le cas du couple Ar/Ti, l'efficacité d'endommagement superficiel augmente lorsque l'énergie du projectile diminue de 9 à 2 MeV. Par ailleurs, alors que la surface du titane apparaît transparente au faisceau d'ions à 15 MeV, celle du zirconium révèle de nombreux cratères micrométriques entourés d'un large halo sombre. Les caractéristiques des cratères (taille et densité superficielle) diffèrent de façon significative de celles observées à la fois dans le domaine des basses énergies (keV) où le dépôt d'énergie est contrôlé par les collisions balistiques (Sn) et dans le domaine des hautes énergies (MeV - GeV) où le dépôt d'énergie est contrôlé par les excitations électroniques (Se), ce qui n'était pas complètement inattendu dans le domaine d'énergie intermédiaire étudié, dans lequel des effets de pouvoir d'arrêt combiné Sn - Se sont envisageables. Par XPS couplé au décapage ionique, nous avons montré qu'il existe un effet d'irradiation sur l'oxydation thermique du titane, exacerbée sous faisceau d'ions d'argon entre 2 et 9 MeV, et qu'il existe aussi un effet d'énergie sur l'épaisseur et la stœchiométrie de l'oxyde. L'étude menée par Ellipsométrie Spectroscopique sur les films d'oxyde formés entre 1 et 9 MeV a corroboré ces résultats et montré précisément qu'il existe un pic d'oxydation en fonction de l'énergie d'ions d'argon, qui présente un maximum à 3 MeV, dans les conditions de l'expérience. Les mesures de gain d'oxygène effectuées par NBS confirment l'existence de ce pic d'oxydation. Les résultats acquis à ce jour par NBS concernant l'oxydation thermique du zirconium sous irradiation à l'argon de 4 et 9 MeV confirment les travaux antérieurs du groupe Aval du Cycle Electronucléaire de l'Institut de Physique Nucléaire de Lyon, et suggèrent fortement l'existence d'un pic d'oxydation dans la même plage d'énergie de projectile que pour le titane.
17
ADEKOYA, OLUSEYI. "Etude du recuit thermique rapide des defauts d'implantation dans le silicium : epitaxie en phase solide et guerison des imperfections residuelles." Paris 7, 1987. http://www.theses.fr/1987PA077265.
Full textAbstract:
Etude de l'activation electrique des dopants (donneur p; accepteur b) et de l'elimination des defauts residuels dans si monocristallin par recristallisation epitaxique des couches, amorphisees par implantation ionique, et par recuit thermique rapide. Controle de la qualite des couches par retrodiffusion de rutherford et microscopie electronique en transmission et de l'elimination des defauts residuels par la methode dlts (niveau profond a 0,55 ev de la bande de valence). Confirmation de cette elimination des defauts par recuit thermique rapide apres fusion laser de si, avant et apres implantation ionique. Analyse du role electrique des defauts (contraintes thermoelastiques, association impurete-defaut primaire) dans si n, non implante, par des mesures dlts, capacite tension et courant-tension; reduction de leur concentration par depot d'une fine couche d'oxyde
18
Jaouen, Christiane. "Etude des mécanismes des transformations de phase induites par irradiation aux ions dans les systèmes métalliques." Poitiers, 1987. http://www.theses.fr/1987POIT2019.
Full textAbstract:
Etude par mesure de conductivite electrique, par retrodiffusion rutherford et par microscopie ionique en transmission des differents aspects du melange ionique dans le systeme mt/al (mt=fe, co, ni) et fe-mg. Analyse des differents facteurs controlant la formation d'une phase et celle d'une phase amorphe. Analyse des mecanismes de transformation cristal-amorphe de l'alliage ni::(50)al::(50) en couche mince. Influence des parametres d'irradation sur cette transformation
19
Ravel, Frédéric. "Contribution à l'étude de l'implantation fer dans les grenats par microscopie électronique en transmission." Grenoble 1, 1986. http://www.theses.fr/1986GRE10127.
Full textAbstract:
Etude des effets de l'implantation d'ions fers dans y::(3)al::(5)o::(12),gd::(3)ga::(5)o::(12) et y::(3)fe::(5)o::(12) par differentes techniques (microscopie electronique en transmission, retrodiffusion rutherford, diffraction rx). Les changements structuraux et les modifications des proprietes magnetiques dus a l'implantation sont etudies avant et apres recuit
20
Weckmann, Armin. "Material migration in tokamaks : Erosion-deposition patterns and transport processes." Doctoral thesis, KTH, Fusionsplasmafysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209758.
Full textAbstract:
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
21
Guo-ShunTsai and 蔡國順. "On Noise Statistics of Electron Backscattering Diffraction." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/81502162351396635303.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系碩博士班
98
In this study, the effect of sample preparation on the angular resolution was investigated using 99.99% copper single crystal which was produced by Bridgeman method. Specimen of single crystal coppers were mechanically polished using 1, 0.3, 0.02μm and electro-polishing, respectively. And then all EBSD measurements were performed using a step size of 85nm under 30kV. It was found that using larger polishing particle size results in a larger orientation spread. As the polishing particle size were decreased from 1 to 0.02μm, the value of , that is, 95% of the total values, was also reduced from 4.0° to 1.0° and 0.8° for electro polishing. The misorientation noise can be defined as Type I and Type II. Type I means “random noise” in the range of 0° and 0.7°, which is a random distribution. Besides, Type II is called “sample preparation noise” between 0.7° and that usually exists near scratched areas. Moreover, the range between 0.7° and are 3.3°、0.4°、0.3°、0.1°for using polishing particle size of 1、0.3、0.02μm and electro polishing, respectively.
22
DelphicChen and 陳志慶. "On Spatial and Angular Resolutions in Electron Backscattering Diffraction." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/19101640434882982174.
Full textAbstract:
博士國立成功大學
材料科學及工程學系碩博士班
100
For nanoscale microstructure analysis the spatial resolution of the EBSD is of very importance. It is well known several factors affect the spatial resolution. However, until now, it lacks of a quantitative measurement of the spatial resolution. In addition to the spatial resolution the angular resolution also plays an important role in EBSD analysis technique for fine subgrain microstructures after heavy deformation. In this study, therefore, the spatial and angular resolutions of the EBSD system are investigated. Bicrystals of silver, copper, and aluminum were combined with a digital image correlation method to investigate the physical spatial resolution of EBSD, that is, the lateral and longitudinal resolutions. At the same time the effect of accelerating voltage and probe current was systematically investigated on the physical spatial resolution for Ag, Cu, and Al, respectively. The lateral and longitudinal resolutions show high dependency on the accelerating voltage for Al. However, for Cu and Ag, the lateral and longitudinal resolution does not show such dependency on accelerating voltage as in Al for less than 10kV. Moreover, the probe current does not play a role on both lateral and longitudinal resolutions. The best lateral resolutions for Al, Cu, and Ag are 40.5, 33.7, and 12.1 nm, respectively. The best longitudinal resolutions of 74.5, 44.7, and 23.3 nm were obtained for Al, Cu, and Ag, respectively. A novel measurement of the depth resolution in EBSD was firstly proposed. The application of a tilted twin boundary enables us to measure the depth resolution under consideration of the electron channeling effect. Considering the channeling effect, the best physical depth resolution of 38 nm for Cu was achieved at 5 kV and 10 nA which is much larger than that obtained with a coating layer. As for the angular resolution, a new filter combining the bilateral filter and the orientation averaging was developed in this study. The proposed orientation bilateral filter has two features: preservation of boundary structures or deformed substructures and significant reduction in orientation noise after only one pass. It was implemented in this study to enhance the angular precision of orientation maps for deposited and deformed structures of pure Cu obtained from EBSD measurements. Applying the filter to the deformed and deposited structures, the relative angular accuracy is enhanced from 0.71° to 0.251° and 0.071°, respectively.
23
JimmyHuang and 黃俊銘. "Effects of Coating Thickness and Atomic Number on Backscattering Electron Signals in Metallic and Ceramic Substrates." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/07665745500883161716.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系碩博士班
101
This thesis will propose some methods to solve the oxidation problem on metals and charging problem on ceramics.We deposited a thin conductive film on the surface of substrates, then it would separate the directly contact with atmosphere for metals and conduct the electrons out of the surface for ceramics.But the coating thin film will interfere the incident electrons and block the backscattering electrons out of substrates, so we will discuss the relationship between the atmoic number, film thickness and electron signals. In the experiment, we chose the Al,Cu,Ag as metal substrates, Al2O3 ,ZrO2 ,CeO2 as ceramic substrates, and Al,Ni,Pt as coating materials. After sample preparation, we used e-beam deposition to coat thin film from 0 to 8 nm with 2nm a step. Then used FE-SEM to do EBSD mapping, and analyzed with TSL OIM Analysis 6, Image J. Furthermore, using CASIO 4.2 software to simulate the condition in SEM scanning to compete the result with experiment. According to the results, no matter what the metals or ceramics are, when increasing the substrate atomic number, the backscattering electron signals is stronger than small atomic number materials, and the signal descendant rate is slow. Additionally, we also discussd the effect of thin film thickness and their atomic number. First, we found that the thicker coating film, the faster signals decay rate. Second, the larger atomic number of coating materials, the higher descendant rate for backscattering electron signals. But we found a exception for Pt coating. Based on the Pt physical properties, the adhesion force for Pt is not quiet well when depositing on substrates, so it is easy to peel off or form the island structure. Owing to the film morphology, the cross-section area for inelastic collide is shrinking, then the interference on elastic backscattering electrons is also reduced. So compare with the rule of larger coating atomic number, larger signals decay rate, it is not suitable for Pt materials. Last but also the more important,the best condition for solving charging problme and oxidation problem is coating a thin film under 2nm. Even though the coating film will also dimish the backscattering electorn signals, it is still under the acceptable range for resolving by TSL OIM Analysis 6 software.
24
Majiet, Siradz. "Using internet-enabled remote instrumentation for research and training in physics: evaluation ofdifferent diffusion barriers for silver metallization." Thesis, 2007. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_7713_1259932803.
Full textAbstract:
The growth of the Internet has led to many interesting developments for both educational and commercial purposes. In this project an attempt was made to use the Internet for a research purpose to facilitate the determination of the thermal stability of diffusion barriers. Another purpose of this thesis is to investigate the teaching and training use of the Internet through the development of online interactive tools and activities as well as materials. The training aspects are mentioned as it is hoped that this thesis can serve as a form of documentation of the use of the Internet, while the central part was the determination of thermal stability of TiN, TaN and TiW diffusion barriers on Ag.
25
Majiet, Siradz. "Using internet-enabled remote instrumentation for research and training in physics: evaluation of different diffusion barriers for silver metallization." 2007. http://hdl.handle.net/11394/3656.
Full textAbstract:
>Magister Scientiae - MScThe growth of the Internet has led to many interesting developments for both educational and commercial purposes. In this project an attempt was made to use the Internet for a research purpose to facilitate the determination of the thermal stability of diffusion barriers. Another purpose of this thesis is to investigate the teaching and training use of the Internet through the development of online interactive tools and activities as well as materials. The training aspects are mentioned as it is hoped that this thesis can serve as a form of documentation of the use of the Internet, while the central part was the determination of thermal stability of TiN, TaN and TiW diffusion barriers on Ag.
26
Kheswa, Ntombizonke Yvonne. "Synthesis and characterisation of 114Cd targets." Thesis, 2011. http://hdl.handle.net/11394/3681.
Full textAbstract:
>Magister Scientiae - MScTo study nuclear reactions and nuclear structures, target materials are bombarded with high-energy particles. The target material can either be in a form of a metal film or gas. A target material designed to study certain nuclear reactions or to produce nuclei to study their structure should yield as minimum as possible of competing reactions under ion bombardment. This requires a chemically and isotopically pure target material prepared as a self supporting thin film, or as alternative, prepared on a thin career foil. Additional requirement for lifetime measurement experiments are homogeneity and precise thickness of the target material. Some of the data obtained from the stopping power experiment where targets of 114Cd were used for lifetime measurement are presented. Moreover, a nuclear target should influence the spectroscopic resolution as little as possible. Thus, film thickness must be adjusted to the respective reaction under study while observing the optimum thickness homogeneity.
27
Soori, Abhiram. "Electronic Transport in Low-Dimensional Systems Quantum Dots, Quantum Wires And Topological Insulators." Thesis, 2013. http://etd.iisc.ernet.in/2005/3341.
Full textAbstract:
This thesis presents the work done on electronic transport in various interacting and non-interacting systems in one and two dimensions. The systems under study are: an interacting quantum dot [1], a non-interacting quantum wire and a ring in which time-dependent potentials are applied [2], an interacting quantum wire and networks of multiple quantum wires with resistive regions [3, 4], one-dimensional edge stages of a two-dimensional topological insulator [5], and a hybrid system of two-dimensional surface states of a three-dimensional topological insulator and a superconductor [6].
In the first chapter, we introduce a number of concepts which are used in the rest of the thesis, such as scattering theory, Landauer conductance formula, quantum wires, bosonization, topological insulators and superconductor.
In the second chapter, we study transport through a quantum dot with interacting electrons which is connected to two reservoirs. The quantum dot is modeled by two sites within a tight-binding model with spinless electrons. Using the Lippman-Schwinger method, we write down an exact two-particle wave function for the dot-reservoir system with the interaction localized in the region of the dot. We discuss the phenomena of two-particle resonance and rectification.
In the third chapter, we study pumping in two kinds of one-dimensional systems:
(i) an infinite line connected to reservoirs at the two ends, and (ii) an isolated ring. The infinite line is modeled by the Dirac equation with two time-independent point-like backscatterers that create a resonant barrier. We demonstrate that even if the reservoirs are at the same chemical potential, a net current can be driven through the channel by the application of one or more time-dependent point-like potentials. When the left-right symmetry is broken, a net current can be pumped from one reservoir to the other by applying a time-varying potential at only one site. For a finite ring, we model the system by a tight-binding model. The ring is isolated in the sense that it is not connected to any reservoir or environment. The system is driven by one or more time-varying on-site potentials. We develop an exact method to calculate the current averaged over an infinite amount of time by converting it to the calculation of the current carried by certain states averaged over just one time period. Using this method, we demonstrate that an oscillating potential at only one site cannot pump charge, and oscillating potentials at two or more sites are necessary to pump charge. Further we study the dependence of the pumped current on the phases and the amplitudes of the oscillating potentials at two sites.
In the fourth chapter, we study the effect of resistances present in an extended region in a one-dimensional quantum wire described by a Tomonaga-Luttinger liquid model. We combine the concept of a Rayleigh dissipation function with the technique of bosonization to model the dissipative region. In the DC limit, we find that the resistance of the dissipative patch adds in series to the contact resistance. Using a current splitting matrix M to describe junctions, we study in detail the conductances of: a three-wire junction with resistances and a parallel combination of resistances. The conductance and power dissipated in these networks depend in general on the resistances and the current splitting matrices that make up the network. We also show that the idea of a Rayleigh dissipation function can be extended to couple two wires; this gives rise to a finite transconductance analogous to the Coulomb drag.
In the fifth chapter, we study the effect of a Zeeman field coupled to the edge states of a two-dimensional topological insulator. These edge states form two one-dimensional channels with spin-momentum locking which are protected by time-reversal symmetry. We study what happens when time-reversal symmetry is broken by a magnetic field which is Zeeman-coupled to the edge states. We show that a magnetic field over a finite region leads to Fabry-P´erot type resonances and the conductance can be controlled by changing the direction of the magnetic field. We also study the effect of a static impurity in the patch that can backscatter electrons in the presence of a magnetic field.
In the sixth chapter, we use the Blonder-Tinkham-Klapwijk formalism to study trans-port across a line junction lying between two orthogonal topological insulator surfaces and a superconductor (which can have either s-wave or p-wave pairing). The charge and spin conductances across such a junction and their behaviors as a function of the bias voltage applied across the junction and various junction parameters are studied. Our study reveals that in addition to the zero conductance bias peak, there is a non-zero spin conductance for some particular spin states of the triplet Cooper pairs. We also find an unusual satellite peak (in addition to the usual zero bias peak) in the spin conductance for a p-wave symmetry of the superconductor order parameter.