Ce mémoire de thèse traite de l'étude de jonctions pn silicium planaires, réalisées par épitaxie localisée, avec un nouveau type de microscopie à émission de photoélectrons (XPEEM) filtré en énergie. L'objectif est d'améliorer notre compréhension des facteurs influençant l'imagerie XPEEM de jonctions modèles avec une perspective à plus long terme d'application de cette technique aux cas réels.Sur les trois types de jonction réalisées présentant des champs électriques variables (P+/P, N+/P, P+/N), nous avons d'abord mis en œuvre un procédé de passivation en trois étapes afin de se rapprocher de conditions en bandes plates en surface. Ce procédé nous a permis d'étudier la position des niveaux électroniques de part et d'autre des jonctions grâce à une imagerie en XPEEM spectroscopique avec électrons secondaires (travail de sortie local), électrons de cœur Si 2p et bande de valence, avec à la fois avec des sources X de laboratoire et le rayonnement synchrotron. Un mécanisme de contraste des images en électrons de cœur dû à la toute première couche atomique de surface a été montré. Ensuite, nous avons mis en évidence le rôle du champ électrique au niveau de la zone de déplétion des jonctions qui décale la position apparente de cette dernière dans l'image XPEEM. Nous avons comparé les résultats expérimentaux avec des simulations (logiciel SIMION) afin d'estimer son influence sur les conditions d'imagerie. Enfin, nous avons étudié l'impact de la technique d'imagerie en champ sombre sur la localisation de la jonction réelle au niveau de la surface de l'échantillon. / This thesis addresses the problem of imaging of model systems planar silicon pn junctions, fabricated by localized epitaxy, using the novel energy-filtered X-ray PhotoElectron Emission Microscope (XPEEM). The objective is to improve the understanding of the phenomena influencing the XPEEM images of the junctions, with as long-term perspective, a possible application of this method in a complementary way to existing techniques of 2D dopant mapping.The studies were carried out over three types of junction realized to this purpose and presenting variable electrical field (P+/P, N+/P, P+/N). We firstly developed and optimized a passivation protocol in three-steps which yielded a surface close to flat band conditions. This process allowed us to deduce band alignments as a function of doping level and type on both side of the junction thanks to spectroscopic XPEEM imaging of secondary electrons (to determine local work function), Si 2p core-level and valence band with both laboratory photon sources and synchrotron radiation. Contrast in core-level imaging due to the first atomic layer of the surface was also shown.Then, we highlighted the role of the lateral electric field across the depletion zone of a pn junction which shifts the apparent position of the latter in PEEM imaging. We compared experimental results and simulations performed with SIMION software to estimate the influence of pn junctions on PEEM imaging. Dark field imaging of the junction was also simulated. Comparison with the experimental results showed that it can be used to localize the real junction.

Dans cette thèse, des films à base de graphène ont été étudiés comme alternatives viables dans la fabrication d'électrodes transparentes (TCE). Elle met l'accent sur des couches fines de graphène (FLG), sur l'oxyde de graphène réduit (RGO) et leurs hybrides avec des nanotubes de carbone (NTCs) pour être utilisé comme TCE dans les cellule solaires organiques (OSC). Les FLGs et RGO ont été préparés par des méthodes d'exfoliation mécanique ou en phase liquide assistée par micro-ondes. Ces nanomatériaux dilués dans un solvant liquide ont été déposé en couche mince par aérographe. Des caractérisations de transport de charge ont été obtenues grâce à la méthode des 4 pointes. Ces échantillons ont été caractérisés: leur transparence(UV-Visible), leur morphologie et leur topographique (MEB, MET, AFM) ainsi que le travail de sortie (UPS). Pour obtenir des informations sur la qualité structurelle des échantillons, nous avons utilisés les méthodes de spectroscopie XPS, Raman et la photoluminescence. / Graphene mate rials have been researched as viable alternatives of transparent conductors electrodes (TCEs) in this thesis. Current study focuses on few layer graphene (FLG), reduced graphene oxide (rGO) and their hybrids with carbon nanotubes (CNTs) for TCE applications inorganic solar cells (OSCs). FLGs and rGOs have been prepared by mechanical and microwave-assisted exfoliation methods. This films of these materials have been produced by hot-spray method. Results of charge transport characterizations by four-point probes, transparency (UV-Vis), measurements, along with morphological (SEM, TEM) and topgraphic (AFM) studies of films have been presented. UPS studies were performed to determine for a work-function. XPS,Raman and Photoluminescence studies have been employed to obtain the information about the structural quality of the samples.

Die steigende Dynamik sowie der steigende Konkurrenzdruck, dem deutsche und europäische Produktionsunternehmen aufgrund von Individualisierungs- und Globalisierungstendenzen ausgesetzt sind, erfordert neue Konzepte zur Gestaltung effizienter Prozesse und damit konkurrenzfähiger Produkte. Trotz oder gerade wegen eines vielfach hohen Automatisierungsniveaus und der damit verbundenen Komplexität sind viele Arbeitssysteme durch einen hohen Anteil an Personalkosten für technikerhaltende Arbeitsaufgaben geprägt. Die vorliegende Arbeit stellt einen Ansatz vor, wie bestehende automatisierte Arbeitssysteme analysiert, bewertet und bzgl. des Personaleinsatzes optimiert werden können.

No description available.

No description available.

The study investigated the impact of computer simulations on the teaching and learning of photoelectric effect in Grade 12. The Grade 12 Physical Sciences curriculum has components of physics and chemistry. The photoelectric effect is a section in the physics curriculum and examination in the National Senior Certificate. In this case study, thirty learners were randomly divided into three groups in one rural school in the Frances Baard district in the Northern Cape Province. A randomised pre-test - post-test control group design was implemented. Data were collected through pre and post tests, by observation of the lessons and learner interviews. An analysis of variance performed showed that there was no significant difference on pre-test scores for the three groups. A paired -sample t-test on the post-test scores discovered that the Teacher-Centred Experimental Group (TCEG) performed better than the Learner-Centred Experimental Group (LCEG); (t statics, t (9) = -6.135, p < 0.05). In addition, the Control Group (CG) where the teacher used the traditional method of teaching performed even better than the Learner-Centred Experimental group. An analysis of covariance on the post-test scores with learners' pre-test scores as the covariate showed a significant effect on the instructional group favouring the TCEG (F (2,29) = 52.763, p < 0.05). The Hake's normalised gain, <g> was used to measure the effectiveness of the intervention. The normalised gain showed a high-g (0.794) for the TCEG, a medium-g (0.405) for the CG and a low-g (0.134) for the LCEG. The interview data also confirms that the TCEG learners benefited more than the LCEG learners. It is, therefore, suggested that the TCEG approach is a better method for the effective teaching of photoelectric effect. / Science and Technology Education / M. Sc. (MSTE)

For the past decades, Kelvin probe force microscopy (KPFM) developed from a sidebranch of atomic force microscopy to a widely used standard technique. It allows to measure electrostatic potentials on any type of sample material with an unprecedented spatial resolution. While the technical aspects of the method are well understood, the interpretation of measured data remains object of intense research. This thesis intends to prove an advanced view on how sample systems which are typical for ultrahigh resolution imaging, such as organic molecular submonolayers on metals, can be quantitavily analysed with the differential charge density model. In the first part a brief introduction into the Kelvin probe experiment and atomic force microscopy is given. A short review of the theoretical background of the technique is presented. Following, the differential charge density model is introduced, which is used to further explain the origin of contrast in Kelvin probe force microscopy. Physical effects, which cause the occurence of local differential charge densities, are reviewed for several sample systems that are of interest in high resolution atomic force microscopy. Experimental evidence for these effects is presented in the second part. Atomic force microscopy was used for in situ studies of a variety of sample systems ranging from pristine metal surfaces over monolayer organic adsorbates on metals to ferroelectric substrates both, with and without organic thin film coverage. As the result from these studies, it is shown that the differential charge density model accurately describes the experimentally observed potential contrasts. This implies an inherent disparity of the measurement results between the different Kelvin probe force microscopy techniques; a point which had been overseen so far in the discussion of experimental data. Especially for the case of laterally strong confined differential charge densities, the results show the opportunity as well as the necessity to explain experimental data with a combination of ab initio calculations of the differential charge density and an electrostatic model of the tip-sample interaction.