Tendo em vista a importância da calibração de instrumentos medidores de radiação e do conhecimento das principais características destes instrumentos, diversos tipos de câmaras de ionização foram intercomparados em termos de seus coeficientes de calibração e dependência energética, em feixes padrões de raios X, níveis radioterapia, radiodiagnóstico e radioproteção. Foi realizada uma intercomparação de activímetros utilizados em medicina nuclear, com três radionuclídeos: 67Ga, 201Tl e 99mTc. Todos os activímetros que participaram da intercomparação apresentaram resultados dentro dos limites recomendados pela norma CNEN-NE-3.05. Para completar o conjunto de qualidades de radiação do Laboratório de Calibração de Instrumentos do IPEN, foram estabelecidos feixes de radiação-X, nível radioproteção e radioterapia de energias baixas, seguindo recomendações internacionais. Três metodologias para a obtenção de coeficientes de calibração de câmaras de ionização não seladas em feixes de radiação-X foram estudadas e comparadas. Um conjunto de câmaras de ionização Victoreen, especialmente projetado para uso em intercomparações laboratoriais, foi submetido a testes de caracterização. O desempenho destas câmaras mostrou que elas podem ser utilizadas em feixes de radiação-X nível radioproteção de maneira segura, visto que nestes feixes estas câmaras apresentaram resultados em conformidade com recomendações internacionais. No entanto, seu uso em feixes de radioterapia e de radiodiagnóstico deve ser feito com algumas considerações, pois especialmente nos testes de dependência energética e de tempo de estabilização, estas câmaras não atenderam às respectivas recomendações internacionais. Este trabalho apresenta dados sobre o desempenho de diversos modelos de câmaras de ionização em diferentes feixes de radiação-X, fornecendo uma ferramenta para a escolha do instrumento mais adequado para a realização de medições em feixes de radiação ionizante / Since the calibration of radiation measurement instruments and the knowledge of their major characteristics are very important subjects, several different types of ionization chambers were intercompared in terms of their calibration coefficients and their energy dependence, in radiotherapy, diagnostic radiology and radioprotection standard beams. An intercomparison of radionuclide calibrators for nuclear medicine was performed, using three radionuclides: 67Ga, 201Tl and 99mTc; the results obtained were all within the requirements of the national standard CNEN-NE-3.05. In order to complete the range of radiation qualities of the Calibration Laboratory of IPEN, standard radiation beam qualities, radiation protection and low energy radiation therapy levels, were established, according international recommendations. Three methodologies for the calibration of unsealed ionization chambers in X-ray beams were studied and compared. A set of Victoreen ionization chambers, specially designed for use in laboratorial intercomparisons, was submitted to characterization tests. The performance of these Victoreen ionization chambers showed that they are suitable for use in radioprotection beams, because the results obtained agree with international recommendations. However, these Victoreen ionization chambers can be used in radiotherapy and diagnostic radiology beams only with some considerations, since their performance in these beams, especially in relation to the energy dependence and stabilization time tests, did not agree with the international recommendations for dosimeters used in radiotherapy and diagnostic radiology beams. This work presents data on the performance of several types of ionization chambers in different X-ray beams, that may be useful for choosing the appropriate instrument for measurements in ionizing radiation beams.

Uma série de testes foi aplicada a medidores portáteis de radiação ionizante para altas taxas de kerma no ar, especificamente medidores do tipo teletector. Estes detectores são do tipo Geiger Müller e são utilizados em rotinas de proteção radiológica em aceleradores, reatores, fontes de alta atividade e ainda em situações de emergência no Brasil, assim como em outros países. Também são encaminhados para calibração no Instituto de Pesquisa Energéticas e Nucleares (IPEN) e foram analisados para estabelecer parâmetros de comportamento destes detectores, especificando as suas sensibilidades e suas características operacionais. Foram realizados testes de variação da leitura dos equipamentos com a tensão da bateria, efeito de geotropismo, dependência energética, dependência angular. Com este testes foi possível determinar as características mais comuns e importantes destes equipamentos permitindo a elaboração de um programa de controle de qualidade. Foram calibrados 17 teletectors durante este trabalho e destes, 10 foram testados. Os testes foram realizados para caracterizar o sis tema gama de irradiação (dosimetria de feixe de radiação) que possui maior atividade e permite testes em medidores do tipo teletectors em uma maior faixa de medição. Desse modo foi feito o aperfeiçoamento do programa de controle de qualidade de medidores portáteis de radiação ionizante para altas taxas de kerma no ar no LCI, oque beneficiou os usuários deste tipo de equipamento, e ainda com medições e calibrações mais consistentes e com melhor controle de qualidade dos processos. / A series of tests was applied to portable survey meters for high rates of kerma in the air, specifically meters type teletector. These detectors are the Geiger- Müller type and are used in radioprotection routines in accelerators, nuclear reactors, irradiators systems with high activity sources and even in emergency situations in Brazil, as in other countries. They are also sent for calibration at the Instruments Calibration Laboratory (LCI) at the Institute of Energy and Nuclear Research (IPEN) and were analyzed to establish behavior parameters of these detectors, specifying their sensitivities and their operational characteristics. The reading variation tests were performed with the equipment battery voltage variation, geotropism effect, energy dependence, angular dependence; with these tests was possible to determine the most common and important features of these devices, allowing the development of a quality control program. In this work 17 teletectors were analyzed and ten detectors tested. The tests were performed to characterize the gamma irradiator system (dosimetry of dosimetry beam) which has higher activity and allows test in meters type teletector in a higher measuring range. Thus, it was made the improvement of the quality control program of portable survey meters of high rates of kerma in the air in the LCI, benefiting the users of such equipment and with measurements and calibrations more consistent and better quality control processes.

Uma série de testes foi aplicada a medidores portáteis de radiação ionizante para altas taxas de kerma no ar, especificamente medidores do tipo teletector. Estes detectores são do tipo Geiger Müller e são utilizados em rotinas de proteção radiológica em aceleradores, reatores, fontes de alta atividade e ainda em situações de emergência no Brasil, assim como em outros países. Também são encaminhados para calibração no Instituto de Pesquisa Energéticas e Nucleares (IPEN) e foram analisados para estabelecer parâmetros de comportamento destes detectores, especificando as suas sensibilidades e suas características operacionais. Foram realizados testes de variação da leitura dos equipamentos com a tensão da bateria, efeito de geotropismo, dependência energética, dependência angular. Com este testes foi possível determinar as características mais comuns e importantes destes equipamentos permitindo a elaboração de um programa de controle de qualidade. Foram calibrados 17 teletectors durante este trabalho e destes, 10 foram testados. Os testes foram realizados para caracterizar o sis tema gama de irradiação (dosimetria de feixe de radiação) que possui maior atividade e permite testes em medidores do tipo teletectors em uma maior faixa de medição. Desse modo foi feito o aperfeiçoamento do programa de controle de qualidade de medidores portáteis de radiação ionizante para altas taxas de kerma no ar no LCI, oque beneficiou os usuários deste tipo de equipamento, e ainda com medições e calibrações mais consistentes e com melhor controle de qualidade dos processos. / A series of tests was applied to portable survey meters for high rates of kerma in the air, specifically meters type teletector. These detectors are the Geiger- Müller type and are used in radioprotection routines in accelerators, nuclear reactors, irradiators systems with high activity sources and even in emergency situations in Brazil, as in other countries. They are also sent for calibration at the Instruments Calibration Laboratory (LCI) at the Institute of Energy and Nuclear Research (IPEN) and were analyzed to establish behavior parameters of these detectors, specifying their sensitivities and their operational characteristics. The reading variation tests were performed with the equipment battery voltage variation, geotropism effect, energy dependence, angular dependence; with these tests was possible to determine the most common and important features of these devices, allowing the development of a quality control program. In this work 17 teletectors were analyzed and ten detectors tested. The tests were performed to characterize the gamma irradiator system (dosimetry of dosimetry beam) which has higher activity and allows test in meters type teletector in a higher measuring range. Thus, it was made the improvement of the quality control program of portable survey meters of high rates of kerma in the air in the LCI, benefiting the users of such equipment and with measurements and calibrations more consistent and better quality control processes.

Nowadays, inspection process planning (IPP) for large volume metrology (LVM) attracts increasing attention in manufacturing and assembly industries such as aerospace and automotive, where large and complex assemblies and fabrications with complex surfaces are employed. Inspection is conventionally considered as a quality control manner. But there is changing shift to processes that are more related to the early design stage aiming to increase product performance and reduce costs by automation and elimination of rework. This is especially evident in the standardisation and implementation of Geometric Dimensioning and Tolerancing (GD&T) of new products and systems at the design stage. This study proposes a GD&T based systematic framework for the IPP of LVM systems within a digital environment. Orientating to solve the “what to measure” and “how to measure” problems in IPP, the prototype system has seven functional core modules including: tolerance feature analysis, instrument selection, inspection point selection, accessibility and visibility analysis, instrument setup and configuration, clustering analysis and measurement sequencing. An optimized inspection plan is output for the designer to evaluate the product design as well as for guiding the metrologist and process planner to conduct the inspection process. Heuristic rules, evolutionary algorithms and modern computational graphic techniques have been adopted to facilitate the supported functions. Coupled with state of art metrology systems, metrology and CAD software, the framework is able to work effectively and efficiently by means of incorporating international standards and industrial best practice. It is the first attempt to successfully minimise manual activities in the planning process for LVM systems, which results in improved efficiency, enhanced decision making and a better inspection plan overall. Two case studies have been conducted to validate the functionalities of the prototype system.

Este trabalho apresenta o procedimento que desenvolvemos e empregamos para determinar os valores a serem adotados para as energias de um conjunto de raios gama comumente utilizados como padrões de calibração, bem como sua respectiva matriz de covariância, esta obtida pela primeira vez. A matriz de covariância entre as energias destes padrões revelou muitos casos de correlações com valores absolutos maiores que 0,8, correlações estas que precisam ser corretamente consideradas para não comprometer a qualidade das análises efetuadas com o uso daquelas energias. No procedimento desenvolvido foi considerada a relação entre as energias dos raios gama (em múltiplos de eV) e as constantes fundamentais das quais dependem: h, e, c e o parâmetro de rede do Silício (aSi), o que possibilitou atualizar os resultados para as constantes fundamentais recomendadas de 2002. Uma metodologia para a inclusão de novos resultados experimentais ao conjunto de padrões de modo a preservar sua auto-consistência também foi desenvolvida neste trabalho. Este método considera adequadamente as covariâncias e atualiza todo o conjunto de padrões para incorporar as novas informações experimentais em uma única etapa. Por fim, utilizamos as metodologias de análise desenvolvidas e o conjunto de padrões aqui recomendados para analisar dados de medidas dos raios gama do decaimento do 233U e, assim, estudar a adequação de três diferentes modelos de estrutura nuclear para o 229Th, bem como as energias de excitação dos estados nucleares. A energia do primeiro estado excitado do 229Th, um estado metaestável de energia inferior a 10 eV, foi determinada com base naqueles diferentes modelos. / This work presents the procedure which we have developed and employed to determine the values to be adopted for the energies of a set of gamma-rays in common use as calibration standards, publishing for the fist time their respective covariance matrix. Several correlations with absolute values exceeding 0.8 were found, revealing the necessity of considering correctly the covariance matrix in any analysis to be done with the use of these standards in order not to interfere with the quality of the analysis. The procedure here presented considers correctly the relation between the gamma-ray energies (given in eV) and the fundamental constants h, e, c, and the lattice parameter (aSi), allowing the updating of the set with respect to the 2002 recommended values for those constants. A methodology for the inclusion of new experimental results in the set of standards, in a way which preserve its selfconsistency, was also developed in this work. In this method the updating of the whole set of standards is performed in a single step, while considering adequately the covariances. Finally, the standard set recommended here and the methodology developed in this work were employed to analyze data of gamma-rays measurement which follow the 233U decay and therewith to decide about the adequacy of three different nuclear structure models for 229Th and the excitation energy of its nuclear states. The energy of the first excited state of 229Th, a meta-stable state of less than 10 eV, was determined taking into account those different models.

A desfibrilação e a cardioversão elétricas são os procedimentos terapêuticos padrões para o tratamento, respectivamente, das arritmias de fibrilação e taquicardia ventricular. O funcionamento eficaz e seguro de desfibriladores e cardioversores requer uma manutenção preventiva e corretiva sendo, portanto, necessária uma avaliação freqüente do desempenho destes equipamentos. Esta avaliação deve incluir a medição das energias e das tensões e correntes de pico além do tempo de sincronismo para o caso de cardioversores, sendo normalmente realizada por dispositivos denominados analisador de desfibriladores e cardioversores. Para que um analisador de desfibriladores e cardioversores esteja apto a realizar os ensaios prescritos pelas Normas pertinentes, ele deve atender a varias condições, portanto, é necessário a determinação de uma especificação tida como minimamente desejável para um analisador de desfibriladores e cardioversores. Este trabalho descreve o desenvolvimento de um analisador de desfibriladores e cardioversores de fácil utilização e capaz de medir a energia entregue a uma resistência de 50 W, simulando a impedância transtorácica, além das tensões e correntes de pico, positiva e negativa. O analisador também engloba um simulador de ECG, com o qual também se pode realizar ensaios para a medição do tempo de sincronismo de um cardioversor. Uma avaliação do reconhecedor de ritmos de desfibriladores externos automáticos também pode ser realizada através da simulação de arritmias passíveis ou não de desfibrilação. A forma de onda do pulso desfibrilatório é apresentada em um display tipo LCD de 256 x 64 pontos e todos os parâmetros aferidos podem ser transmitidos a um computador por meio de uma interface serial RS-232. A avaliação das incertezas de medição do analisador foi realizada de acordo com documentos normativos e os resultados obtidos mostraram-se adequados às exigências de precisão determinadas pela Norma ANSI/AAMI: DF2, tendo apresentado uma incerteza expandida relativa para as medições de energia igual a 1,03% no pior caso. Os resultados obtidos para a capacidade do procedimento de calibração mostrou-se adequado para as especificações de um analisador de desfibriladores e cardioversores, tendo obtido como resultado, no pior caso, um índice de capacidade Cm igual a 2,82, que é bem superior a 1,0, limite mínimo para que o procedimento seja considerado capaz. Uma comparação do desempenho de outros seis analisadores com a especificação tida como minimamente desejada também foi realizada e demonstrou diversas deficiências desses analisadores. Uma comparação do desempenho de outros seis analisadores com a especificação tida como minimamente desejada também foi realizada e demonstrou diversas deficiências desses analisadores. / The electrical defibrillation and cardioversion are the standard therapeutic procedures for treatment of ventricular fibrillation and ventricular tachycardia arrhythmias, respectively. The effective and secure operation of defibrillators and cardioverter require preventive and corrective maintenance. Therefore, its necessary a frequent evaluation of the performance of these devices. This evaluation must include measuring the energy, peak voltage, peak currents and response time to synchronized discharge, and is usually done by devices called defibrillator and cardioverter analyzer. In order for a defibrillator analyzer to be capable to perform the tests required by relevant Standards, it must be in compliance with several conditions, therefore, it is necessary the determination of a minimum specification that is desirable for a defibrillator and cardioverter analyzer. This paper describes the development of a defibrillators and cardioverters analyzer that is easy to use and is capable of measuring the delivered energy to a 50W resistance, simulating the transthoracic impedance, and also the peak voltage and peak current, positive and negative. The analyzer also includes an ECG simulator which allows the performance of tests to measure the response time to synchronized discharge of a cardioverter. An evaluation of the rhythm recognition detector of automated external defibrillators can also be performed through the simulation of arrhythmias whether or not passives of defibrillation. The waveform of the pulse is presented in a LCD display of 256x 64 pixels and all parameters measured can be transmitted to a computer through a serial interface RS-232. The evaluation of the analyzer uncertainty in measurement was performed according to the prescriptions of normative documents and the results were in accordance with the accuracy prescriptions of the ANSI/AAMI: DF2 Standard, presenting an expanded relative uncertainty for the energy measurements equal to 1,03% for worst case. The results obtained for the capacity of the calibration process are appropriate for the specifications of a defibrillator and cardioverter analyzer, resulting, in the worst case, in an index of capacity Cm equal to 2,82, well above 1,0, the minimum value required to consider the procedure capable. A comparison of the performance of other six analyzers with the minimum specification that is desirable was also done and it demonstrated several deficiencies s with the analyzers.

A desfibrilação e a cardioversão elétricas são os procedimentos terapêuticos padrões para o tratamento, respectivamente, das arritmias de fibrilação e taquicardia ventricular. O funcionamento eficaz e seguro de desfibriladores e cardioversores requer uma manutenção preventiva e corretiva sendo, portanto, necessária uma avaliação freqüente do desempenho destes equipamentos. Esta avaliação deve incluir a medição das energias e das tensões e correntes de pico além do tempo de sincronismo para o caso de cardioversores, sendo normalmente realizada por dispositivos denominados analisador de desfibriladores e cardioversores. Para que um analisador de desfibriladores e cardioversores esteja apto a realizar os ensaios prescritos pelas Normas pertinentes, ele deve atender a varias condições, portanto, é necessário a determinação de uma especificação tida como minimamente desejável para um analisador de desfibriladores e cardioversores. Este trabalho descreve o desenvolvimento de um analisador de desfibriladores e cardioversores de fácil utilização e capaz de medir a energia entregue a uma resistência de 50 W, simulando a impedância transtorácica, além das tensões e correntes de pico, positiva e negativa. O analisador também engloba um simulador de ECG, com o qual também se pode realizar ensaios para a medição do tempo de sincronismo de um cardioversor. Uma avaliação do reconhecedor de ritmos de desfibriladores externos automáticos também pode ser realizada através da simulação de arritmias passíveis ou não de desfibrilação. A forma de onda do pulso desfibrilatório é apresentada em um display tipo LCD de 256 x 64 pontos e todos os parâmetros aferidos podem ser transmitidos a um computador por meio de uma interface serial RS-232. A avaliação das incertezas de medição do analisador foi realizada de acordo com documentos normativos e os resultados obtidos mostraram-se adequados às exigências de precisão determinadas pela Norma ANSI/AAMI: DF2, tendo apresentado uma incerteza expandida relativa para as medições de energia igual a 1,03% no pior caso. Os resultados obtidos para a capacidade do procedimento de calibração mostrou-se adequado para as especificações de um analisador de desfibriladores e cardioversores, tendo obtido como resultado, no pior caso, um índice de capacidade Cm igual a 2,82, que é bem superior a 1,0, limite mínimo para que o procedimento seja considerado capaz. Uma comparação do desempenho de outros seis analisadores com a especificação tida como minimamente desejada também foi realizada e demonstrou diversas deficiências desses analisadores. Uma comparação do desempenho de outros seis analisadores com a especificação tida como minimamente desejada também foi realizada e demonstrou diversas deficiências desses analisadores. / The electrical defibrillation and cardioversion are the standard therapeutic procedures for treatment of ventricular fibrillation and ventricular tachycardia arrhythmias, respectively. The effective and secure operation of defibrillators and cardioverter require preventive and corrective maintenance. Therefore, its necessary a frequent evaluation of the performance of these devices. This evaluation must include measuring the energy, peak voltage, peak currents and response time to synchronized discharge, and is usually done by devices called defibrillator and cardioverter analyzer. In order for a defibrillator analyzer to be capable to perform the tests required by relevant Standards, it must be in compliance with several conditions, therefore, it is necessary the determination of a minimum specification that is desirable for a defibrillator and cardioverter analyzer. This paper describes the development of a defibrillators and cardioverters analyzer that is easy to use and is capable of measuring the delivered energy to a 50W resistance, simulating the transthoracic impedance, and also the peak voltage and peak current, positive and negative. The analyzer also includes an ECG simulator which allows the performance of tests to measure the response time to synchronized discharge of a cardioverter. An evaluation of the rhythm recognition detector of automated external defibrillators can also be performed through the simulation of arrhythmias whether or not passives of defibrillation. The waveform of the pulse is presented in a LCD display of 256x 64 pixels and all parameters measured can be transmitted to a computer through a serial interface RS-232. The evaluation of the analyzer uncertainty in measurement was performed according to the prescriptions of normative documents and the results were in accordance with the accuracy prescriptions of the ANSI/AAMI: DF2 Standard, presenting an expanded relative uncertainty for the energy measurements equal to 1,03% for worst case. The results obtained for the capacity of the calibration process are appropriate for the specifications of a defibrillator and cardioverter analyzer, resulting, in the worst case, in an index of capacity Cm equal to 2,82, well above 1,0, the minimum value required to consider the procedure capable. A comparison of the performance of other six analyzers with the minimum specification that is desirable was also done and it demonstrated several deficiencies s with the analyzers.

L’effet Hall quantique (EHQ), observé par exemple dans des gaz bidimensionnels d’électrons (2DEGS) à basse température et sous fort champ magnétique, a révolutionné la métrologie des résistances car il permet d’obtenir un étalon quantique de résistance qui ne dépend que de e et h (respectivement la charge de l’électron et la constante de Planck). Une des missions des métrologues est de développer les étalons en améliorant leurs performances ou en les rendant plus facile à mettre en oeuvre (travaillant à plus haute température ou plus faible champ magnétique). Dans ce contexte, la physique du graphène suscite l’intérêt pour une application en métrologie. Une monocouche de graphène est une feuille d’un seul atome d’épaisseur constituée d’atomes de carbone disposés en nid d’abeille. Une bicouche de graphène est formée par empilement de deux monocouches. Les écarts en énergie entre les premiers niveaux de Landau dans la monocouche et dans la bicouche sont supérieurs par rapport à ceux dans GaAs ce qui rend l’EHQ dans le graphène plus robuste et laisse envisager le développement d’un étalon plus pratique. Durant ma thèse, nous avons mis en place un protocole de fabrication de barres de Hall en graphène exfolié comprenant un repérage optique, des lithographies électroniques, la métallisation, la gravure plasma… L’utilisation de substrat de silicium oxydé en surface rend possible l’utilisation d’une grille en face arrière. En outre la géométrie des échantillons répond au mieux aux critères métrologiques (canal central large, prises de tension bien définies, …). A basse température, le dopage résiduel obtenu après le recuit in situ est de l’ordre de 3-4x1011 cm-2. Les mobilités sont proches de 3000 cm2/(V.s) et 4000 cm2/(V.s) respectivement pour les échantillons monocouche et bicouche à la fois pour les électrons et les trous. Le transport mésoscopique a été caractérisé à basse température par des mesures de localisation faible et de fluctuations universelles de conductance. La longueur de cohérence que nous avons extraite est de l’ordre de 0.5 µm à 1.5 K. La résistance des contacts mesurée en régime d’EHQ est plutôt faible (typiquement quelques ohms). L’EHQ a été étudié en détail à basse température (300 mK < T <1.5 K) et sous fort champ magnétique (jusqu’à 18.5T) à la fois dans la monocouche et la bicouche en mesurant de manière précise la résistance de Hall (RH) et la résistance longitudinale (Rxx). Les mesures fines de RH sont réalisées à l’aide d’un pont de comparaison basé sur un Comparateur Cryogénique de Courant ; elles consistent à comparer indirectement l’EHQ dans l’échantillon de graphène à l’EHQ obtenu dans une barre de Hall en GaAs/AlGaAs qui est supposée fournir la valeur exacte RH/2. Nos mesures révèlent un accord entre la résistance de Hall dans le graphène et la valeur attendue avec une incertitude de quelques 10-7. Au plus faible courant et dans l’état de dissipation minimale (Rxx→0), nous avons obtenu un accord avec une incertitude relative de 3.10-7. Ce niveau de précision est principalement limité par la petite taille de nos échantillons et par les inhomogénéités de la densité qui y sont présents, ces deux caractéristiques amenant de faibles courants de rupture de l’EHQ (1-2 µA). Toutefois, nos résultats sont à ce jour les tests les plus précis concernant l’EHQ dans du graphène exfolié et les premiers tests sur une bicouche. Ils confirment le potentiel de l’EHQ dans le graphène pour une application en métrologie. / The quantum Hall effect (QHE) observed in two dimensional electron gases (2DEGs) at low temperature and under high magnetic induction, has revolutionized the resistance metrology because it leads to a universal and very reproducible quantum resistance standard only dependent on e and h (respectively the electron charge and Planck's constant). One of the metrologists' missions is to develop standards with improved performances and to notably make them more practical, working for example at higher temperature or lower magnetic induction. In this context, graphene physics could be very interesting for metrological applications. Monolayer graphene is a one atom thick layer of carbon atoms condensed in a honeycomb lattice. A bilayer graphene consists in two stacked monolayers. Larger energy spacings between the first Landau Levels in monolayer and in bilayer than in GaAs make the QHE in graphene more robust and give hope that more practical standards could be developed. During the PhD, we have set a protocol up in order to fabricate exfoliated graphene based Hall bars, including location with an optical microscope, e-beam lithography, metallization, plasma etching… Backgated using oxidized silicon wafers the devices were designed to fulfill at best the metrological requirements (large conduction channel, well defined voltage probes…). At low temperature, the typical charge carrier residual doping obtained after the annealing process was 3-4x1011 cm-2. Mobilities were close to 3000 cm2/(V.s) and 4000 cm2/(V.s) respectively for the monolayer and the bilayer based device both for holes and electrons. Mesoscopic transport was characterized at low temperature by weak localization and universal conductance fluctuations (UCF) measurements. The phase coherence length deduced was about 0.5 µm below 1.5 K. The resistance of the contacts, measured in the QHE regime, appeared to be rather low (typically few ohms). The QHE was investigated in details at low temperature (300 mK < T <1.5 K) and high magnetic field (up to 18.5 T) in both monolayer and bilayer graphene by refined measurements of the Hall resistance (RH) and also of the longitudinal resistance (Rxx). The accurate measurements of RH were performed using a Cryogenic Current Comparator based resistance bridge. They consist in an indirect comparison between the QHE in graphene and the QHE obtained in a GaAs based Hall bar, supposed to deliver the expected value RH/2. Our measurements showed an agreement of the Hall resistance in graphene with the expected value within some parts in 107. At the lowest biasing current and in the lowest dissipation state (where Rxx→0) it is possible to demonstrate an agreement within an uncertainty of 3 parts in 107. That accuracy is essentially limited by the small size, and the poor homogeneity of the carrier density of the graphene electronic systems, both acting for a very reduced breakdown current of the QHE (1-2 µA). Nevertheless these results are the most accurate tests of the QHE performed in exfoliated graphene and the first universality test of the QHE with bilayer graphene. They confirm the potential of the QHE in graphene for the metrological application.

Modern non-destructive approaches for quality control in manufacturing often rely on X-ray computed tomography to measure even difficult-to-reach features. Unfortunately, such measurements require hundreds or thousands of calibrated X-ray projections, which is a time-consuming process and may cause bottlenecks. In the recent state-of-the-art research, tens and hundreds of projections are still required. In this thesis, we examine the radiography physics, technologies, and ex- isting solutions, and we propose a novel approach for non-destructive dimensional measurements from a limited number of projections. Instead of relying on com- puted tomography, we formulate the measurements as a minimization problem in which we compare our parametric model to reference radiographs. We propose the whole dimensional measurements pipeline, including object parametrizations, material calibrations, simulations, and hierarchical optimizations. We fully im- plemented the method and evaluated its accuracy and repeatability using real radiographs of real physical objects. We achieved accuracy in the range of tens or hundreds of micrometers, which is almost comparable to industrial computed tomography, but we only used two or three reference radiographs. These results are significant for industrial quality control. Acquiring...

The Hartmann screen test (HST) is a well-known technique that has been used for many years in optical metrology. This thesis describes how the technique has been adapted to create a system for continuous in situ monitoring of the internal stress in thin films during plasma deposition. Stress is almost always present in thin films. Stress can affect the physical properties of film, and also influence phenomena which are important in the technology of thin film manufacture such as adhesion and crystallographic defects. For these reasons, it is very important to control and manage the film stress during manufacture of devices based on thin films. The commonest way to infer stress is to measure the change in substrate curvature that it produces. This is often done by comparison of substrate curvatures before and after deposition with surface profilometry, or interferometry. However, these methods are unsuitable for implementing during film deposition in the vacuum chamber. A novel method for measuring changes in curvature of the thin film substrate in situ has been developed, making use of the HST. An expanded laser beam is passed through a screen containing a number of small apertures, which breaks it up into several rays. After reflecting from the surface of the thin film wafer, the rays are received on an array detector as a spot pattern. Image processing is performed on the recorded spot images to determine the positions of spots accurately. Spot centre positions are recorded at start of deposition as a reference, then their displacement is tracked with time during deposition. The spot deflections are fitted to a theoretical model, in which the change in sample profile is described by a second-order surface. The principal axes of curvature of this surface and their orientation are obtained by a least-squares fitting procedure. From this, the thin film stress can be inferred and monitored in real time. Equipment using this technique has been designed and developed in prototype form for eventual use in the RMIT cathodic arc deposition facility. First experiments with a classic Hartmann screen configuration proved that the technique gave good results, but precision was limited by diffraction and interference effects in the recorded image which made determination of spot centres more difficult. A modified configuration was developed, in which a camera is focused on the Hartmann screen, giving much sharper spot patterns and improved resolution. Tests on the prototype system and comparison with other techniques have shown that it is possible to determine changes in sample curvature with a precision of approximately 0.01 m-1. This corresponds to stress changes of around 0.5 GPa for typical wafer and film thicknesses used in practice. The Hartmann screen test is straightforward to use and to interpret. Image processing and analysis of the recorded spot patterns can be automated and performed continuously in real time during thin film deposition. The system promises to be very useful for monitoring stress and thus controlling the deposition process for improved quality of thin film manufacture.