Afin d’optimiser les composants de l’industrie de la microélectronique, il est essentiel d’établir le lien entre la texture cristallographique des matériaux constitutifs et leurs propriétés électriques, thermiques et mécaniques. Ainsi, il est nécessaire de disposer d’outils capables de cartographier la morphologie et l’orientation cristallographique des grains à l’échelle nanométrique. La technique ACOM, implémentée sur un Microscope Electronique en Transmission (MET), permet d’obtenir ces informations en exploitant les figures de diffraction électronique. Dans cette thèse, les capacités de cette technique sont évaluées, à la fois pour déterminer la microtexture de matériaux confinés dans quelques dizaines de nanomètres, et pour répondre aux problématiques associées à la fabrication de nouveaux circuits. Cette étude montre dans un premier temps l’importance de l’optimisation des conditions opératoires du MET afin de diminuer les erreurs d’indexation. Des analyses quantitatives de microtexture sont ensuite menées sur des films minces de siliciures de nickel-platine pour différents dopage du substrat, concentration en platine, et température de recuit. Enfin, le cas d’une superposition de signaux de diffraction observé lorsque plusieurs grains sont contenus dans l’épaisseur de l’échantillon est étudié. Les résultats montrent que les erreurs d’indexation restent rares dans ce cas et que les grains de plus large fraction volumique sont majoritairement sélectionnés par l’algorithme d’indexation. Une méthode est alors proposée pour traiter la totalité de l’information détectée dans les clichés de diffraction. Elle s’appuie sur l’indexation successive des orientations cristallographiques après soustraction préalable des réflexions associées à l’orientation précédemment indexée. Les capacités de cet outil en termes de caractérisation de la morphologie des grains superposés sont finalement comparées à deux autres techniques basées sur la reconstruction d’images en champ sombre et sur la factorisation en matrices non-négatives. / The development of advanced nodes in microelectronics requires to understand the impact of crystal size and orientation on the electrical, thermal and mechanical properties of materials. New tools have been developed to map the grains orientation and morphology of nanometer-scaled structures. Among them, the Automated Crystal Orientation Mapping technique used on a Transmission Electron Microscope (ACOM-TEM) is based on the indexation of electron diffraction patterns. The aim of this study was to evaluate the abilities and limitations of the ACOM-TEM technique for the characterization of microelectronics-related materials. Consequently, its ability to analyze nano-sized materials and the possibility of answering problematics related to microelectronics front-end fabrication challenges were investigated. The study highlighted in the first place the importance of the TEM illumination settings. The results showed that minimizing the electron probe convergence angle even at the cost of a larger size has decreased mis-indexation issues. These optimum settings were used to perform quantitative texture analysis of NiPt-silicide thin films. Finally, the case of superimposed diffraction patterns related to overlapping grains was analyzed. Experiments showed that mis-indexing remains limited despite the superimposition and that grains with larger fraction volume were preferentially selected by template matching. A dedicated method was also proposed to overcome crystal overlapping issues. The approach is based on iterative re-indexation of diffraction patterns after subtraction of the reflections related to the previous ACOM best match. Considering the same diffraction patterns data-set, the capabilities of this method to recover the grains size and morphology were compared to two recent techniques based respectively on the analysis of virtual dark field (VDF) images and non-negative matrix factorization (NMF).

Thesis (MMed)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Background The annual burden of stillbirths is estimated to be more than 3 million deaths globally. Depending on the perinatal classification used, up to two thirds of deaths are reported as unknown.Gardosi, et al (2006) developed the ReCoDe system, which identified the relevant condition at the time of death in utero. The system aims to identify what went wrong in utero, without necessarily indentifying why fetal demise occurred. With comparison to the conventional Wigglesworth classification, the authors were able to reduce the number of unexplained stillbirths from 66.2% to 15.2%. The Perinatal Problem Identification Program (PPIP) is the nationally implemented perinatal classification system in South Africa. The PPIP database recorded approximately 660 000 births from the 1st January 2006 until 31st December 2007. This reflects approximately 40% of all births in health institutions in South Africa during this time period. There were 11742 stillbirths recorded in on the PPIP database for this two year period.Unexplained stillbirths formed 24% of the total perinatal deaths. The Saving Babies Report 2006-2007 has suggested that funding andresearch resources be directed to identifying the causes of deaths in this group. Objective: Our primary objective was to compare the outcomes of the PPIP to the ReCoDe classification system developed by Gardosi, with special attention as to reducing the number of unexplained stillbirths. Methods: We conducted a retrospective descriptive study on the perinatal deaths occurring at or presenting to the Department of Obstetrics and Gynaecology at Tygerberg Hospital, Cape Town, South Africa, for the time period extending from 01 January 2008 to 31 December 2008. A weekly Perinatal Mortality Audit meeting (PNM) is held at Tygerberg Hospital. In attendance at these meetings are General obstetricians, Fetal-maternal specialists, Neonatologists, Pathologists, a Geneticist, Obstetric and Paediatric Registrars. Relevant clinical details are summarised from clinical notes and Perinatal Losses data forms. These forms are specific to Tygerberg Hospital and completed by the attending doctor at first consultation. Placental histology and post-mortem examination would have been performed in certain cases as per the departmental protocol. All perinatal deaths, both stillborn and neonatal deaths weighing more than 499g, are discussed at this forum and consensus then reached on a primary and final cause of death. This information is then entered into the PPIP database, along with any identifiable avoidable factors.The investigators separately reviewed the information available from the Perinatal Losses and the PIPP V2.2 data capture forms and then reclassified each stillbirth according to the ReCoDe hierarchal system Results: We studied the data sheets of 406 stillbirths of babies of whom the deaths had been previously classified according to the PPIP classification. The median maternal age was 25.65 years (range 14 – 45) while the median birth weight was 1127 grams (range 500 – 4100).The vast majority of these stillbirths occurred in singleton pregnancies and are also classified as extremely low birth weight. The three major causes of stillbirth over the study period were antepartum haemorrhage (24.4%), hypertensive disorders (22.4%) and spontaneous preterm labour (11.1%). Within the ReCoDe classification, the leading categories were in the placental group (33.2%), fetal group (21.6%) and the maternal group (20%). The unexplained group (PPIP IUD group), from the index study constitutes 8.1% (33 of 406) of cases, while the number of unclassified stillbirths in the primary ReCoDe classification accounted for 15% (60 of 406) of the total. The main reasons for this difference is that ReCoDe does not incorporate preterm labour as a cause, and uses customised growth charts for identifying fetal growth restriction. Conclusion: PPIP remains the gold standard in Perinatal Audit in South Africa.We would recommend that ReCoDe be evaluated prospectively, alongside the established PPIP system, to better compare their performance outcomes. The development of customized fetal growth potential charts relevant to the local population should be explored. The Perinatal Losses data capture form should be revised to be more comprehensive and relevant. / AFRIKAANSE OPSOMMING: Agtergrond Die jaarlikse las van doodgeboortes word geskat op meer as 3 miljoen sterftes wêreldwyd. Afhangende van die perinataleklassifikasiesisteem wat gebruik word, tot twee derdes van sterftes is aangemeld as onbekend. Gardosi, et al (2006) het die ReCoDesisteemontwikkel, wat die betrokke toestand in die tyd van die dood in utero geïdentifiseer. Die sisteem het ten doel om te identifiseer wat verkeerd geloop het in utero, sonder om noodwendig te indentifiseer waarom fetaledood plaasgevind het. Invergelyking met die konvensionele Wigglesworth klassifikasie, was die skrywers in staat om die getal van die onverklaarbare dood geboortes van 66,2% tot 15,2% te verminder. Die Perinataleprobleemidentifikasie Program (PPIP) is die nasionaalgeïmplementeerperinataleklassifikasiesisteemin Suid-Afrika. Die PPIP databasis aangeteken ongeveer 660 000 geboortes van die 1ste Januarie 2006 tot 31 Desember 2007. Dit weerspieël ongeveer 40% van alle geboortes in die gesondheids-instellings in Suid-Afrika gedurende hierdie tydperk. Daar was 11.742 doodgeboortes aangeteken in op die PPIP databasis vir hierdie twee jaartydperk. Onverklaarbaredoodgeboortesvorm 24% van die totaleperinatalesterftes. Die Saving Babies Verslag 2006-2007 het voorgestel dat befondsing en navorsing gerig word aan die identifisering van die oorsake van sterftes in hierdie groep. Doelstelling: Ons primêre doel was om die uitkomste van die PPIP te vergelyk met die ReCoDeklassifikasiesisteem wat deur Gardosiontwikkelis , met spesiale aandag aan die vermindering van die aantal van onverklaarbaredoodgeboortes. Metodes: Ons het'n retrospektiewebeskrywendestudie uitgevoer op die perinatalesterftes wat aangemeld het by die noodeenheid van die Departement Obstetrie en Ginekologie aanTygerberg Hospitaal, Kaapstad, Suid-Afrika, vir die tydperk wat strek vanaf 01 Januarie 2008 tot 31 Desember 2008. 'n Weeklikse Perinatale Mortaliteit Ouditvergadering (PNM) word gehou by Tygerberg Hospitaal. In die bywoning van hierdie vergaderings is Algemene Verloskundiges, Fetale-moederskant Spesialiste, Neonatoloë, Patoloë, 'n Genetikus, Obstetriese en Pediatriese Klienieseassistente. Relevante kliniese inligting is uit die kliniese notas en perinataleverliesedatavorms opgesom. Hierdie vorms is spesifiek na die Tygerberg-hospitaal en deur die dokter by die eerstekonsultasie voltooi. Plasentale histologie en post-mortem ondersoek sou voltooi gewees het in sekere gevalle soos per die departementeleprotokol. Alle perinatalesterftes, beide doodgebore en neonatalesterftes wat meer as 499g, word bespreek op hierdie forum en konsensus bereik oor 'n primêre en finale oorsaak van die dood. Hierdie inligting word dan in die PPIP databasis, saam met 'n identifiseerbare voorkombare faktore. Die navorsers afsonderlik die inligting beskikbaar van die perinataleverliese en die PIPP v2.2 datavasleggingsvorms en dan herklassifiseer elke stilgeboorte volgens die ReCoDehiërargiesestelsel. Results: Ons bestudeer die data velle van 406 doodgeboortes van babas van wie die sterftes voorheen volgens die PPIP klassifikasie geklassifiseer is. Die mediaanmoeder se ouderdom was 25,65jaar (range 14? 45?) Terwyl die mediaangeboortegewig was 1127 gram (reeks 500? 4100). Die oorgrote meerderheid van hierdie doodgeboortes plaasgevind in Singleton swangerskappe en word ookgeklassifiseer as &'n baie lae geboortegewig. Die drie grootste oorsake van doodgeboorte oor die studietydperk was antepartum bloeding (24,4%), die hipertensiewesiektes (22,4%) en &'n voortydsekraam (11,1%). Binne die ReCoDeSistematiek, die voorstekategorieë in die plasentalegroep (33,2%), die fetalegroep (21,6%) en die moedergroep (20%). Die onverklaarbaregroep (PPIP IUD groep), van die indeksstudie behels 8,1% (33 van 406) van gevalle, terwyl die aantal van ongeklassifiseerde doodgeboortes in die primêre ReCoDeSistematiek verantwoordelik vir 15% (60 406) van die totaal. Die belangrikste redes vir die verskil is dat ReCoDenieneemvoortydsekraam as &'n oorsaak, en gebruike aangepasgroeikaarte vir die identifisering van fetalegroeibeperking. Gevolgtrekking: PPIP bly die gouestandaard in Perinataleoudit in Suid-Afrika. Ons sal aanbeveel dat ReCoDe vooruitwerkend geëvalueer word, saam met die gevestigde PPIP stelsel, om beter te vergelyk hulprestasieuitkomste. Die ontwikkeling van persoonlikefetalegroeipotensiaalkaarte met betrekking tot die plaaslike bevolking moet ondersoek word. Die perinataleverliese data capture vorm moet hersien word om meer omvattende en relevant te wees.

abstract: Nanocrystalline (NC) and Ultrafine-grained (UFG) metal films exhibit a wide range of enhanced mechanical properties compared to their coarse-grained counterparts. These properties, such as very high strength, primarily arise from the change in the underlying deformation mechanisms. Experimental and simulation studies have shown that because of the small grain size, conventional dislocation plasticity is curtailed in these materials and grain boundary mediated mechanisms become more important. Although the deformation behavior and the underlying mechanisms in these materials have been investigated in depth, relatively little attention has been focused on the inhomogeneous nature of their microstructure (particularly originating from the texture of the film) and its influence on their macroscopic response. Furthermore, the rate dependency of mechanical response in NC/UFG metal films with different textures has not been systematically investigated. The objectives of this dissertation are two-fold. The first objective is to carry out a systematic investigation of the mechanical behavior of NC/UFG thin films with different textures under different loading rates. This includes a novel approach to study the effect of texture-induced plastic anisotropy on mechanical behavior of the films. Efforts are made to correlate the behavior of UFG metal films and the underlying deformation mechanisms. The second objective is to understand the deformation mechanisms of UFG aluminum films using in-situ transmission electron microscopy (TEM) experiments with Automated Crystal Orientation Mapping. This technique enables us to investigate grain rotations in UFG Al films and to monitor the microstructural changes in these films during deformation, thereby revealing detailed information about the deformation mechanisms prevalent in UFG metal films. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2017