Im Rahmen dieser Arbeit werden haftstellen-basierte Speicherzellen als mögliche Alternative zum bestehenden Floating-Gate Konzept untersucht. Hierbei wird zunächst mittels Simulation und ausgewählten Messverfahren das Verständnis der Funktionsweise vertieft. Der darauffolgende Abschnitt befasst sich mit der Verbesserung der elektrischen Eigenschaften, basierend auf Änderungen der verwendeten Materialien und dem räumlichen Aufbau. Abschließend erfolgt die Untersuchung der Anwendbarkeit des Zellkonzeptes in hochdichten Zellenfeldern.:Kurzfassung Abstract 1 Einleitung 2 Grundlagen aktiver Halbleiterelemente 2.1 Die MOS-Struktur 2.2 Der MOS-Feldeffekt-Transistor 2.3 Nichtflüchtige Festkörperspeicher 2.4 Speicherarchitekturen 2.5 Charakterisierungsmethoden von Halbleiter-Speicherelementen 3 Defektbasierte Ladungsspeicherung in dielektrischen Schichten 3.1 Physikalische Grundlagen von Haftstellen 3.2 Betrachtung der vertikalen Ladungsverteilung mit Hilfe von Simulationen 3.3 Ableitung der vertikalen Ladungsverteilung aus Messungen 4 Elektrisches Verhalten einer haftstellen-basierten Speicherzelle 4.1 Auswirkung von inhomogen verteilter Ladung in der Speicherschicht 4.2 Auswirkungen von Al2O3-Topoxid auf das Zellverhalten 4.3 Auswirkung des Steuerelektrodenmaterials auf das Zellverhalten 4.4 Einfluss von Kanal- und Source/Drain-Dotierung 5 Integration in eine stark skalierte NAND Architektur 5.1 Auswirkung struktureller Effekte auf die Speicherzelle 5.2 Störmechanismen beim Betrieb von stark skalierten NAND-Speichern 6 Zusammenfassung und Ausblick 6.1 Zusammenfassung 6.2 Ausblick Danksagung Lebenslauf Symbol- und Abkürzungsverzeichnis Literaturverzeichnis

Ferroelectric field-effect transistors (FeFET) based on hafnium oxide offer great opportunities for Logic-in-Memory applications, due to their natural ability to combine logic (transistor) and memory (ferroelectric material), their low-power operation, and CMOS compatible integration. Besides aggressive scaling, dense integration of FeFETs is necessary to make electronic circuits more area-efficient. This paper investigates the impact of ultra-dense co-integration of a FeFET and an n-type selector FET, sharing the same active area, arranged in a 2TNOR memory array. The examined FeFETs exhibit a very similar switching behavior as FeFETs arranged in a standard AND-type array, indicating that the ultra-dense co-integration does not degrade the FeFET performance, and thus, paves the path to a very fine-grained, ultra-dense Logic-in-Memory implementation. Based on this densely integrated 2TNOR array we propose a very compact design of a 4-to-1 multiplexer with a build-in look-up table, thus directly merging logic and memory.

The central theme of the research is an investigation into what motivates FET phase learners to learn. All learners are interested in learning certain things however, learners interests often do not correspond with what teachers are required to teach. Teachers are therefore constantly searching for ways to motivate learners to learn. This challenge is not easy for teachers in a culturally homogenous classroom, but becomes even greater when the classes are comprised of learners from diverse cultural backgrounds. So then how does a teacher motivate learners in general, and more specifically learners from different cultural orientations? This is a difficult question to answer but one that needs to be addressed considering the diversity of cultures found in the South African classroom. In this study an attempt is made to examine what motivates learners to learn, and the influence of culture on the motivation to learn of Further Education and Training (FET) phase learners in a multicultural classroom. Data on these two elements is collected through the use of structured questionnaires and focus group interviews and is analysed in order to answer the research question. / Psychology of Education / M. Ed. (Psychology of Education)

Several misconceptions show up when learners answer questions on Chemical Equilibrium during examinations. Literature from other researchers shows similar trend of misconceptions (Johnstone, 2000; Morais, Paiva and Barros, 2007; Adesoji and Babatunde, 2008) for example, ‘apply pressure to the reactants’ (Johnstone, 2000). This shows that Chemistry has no meaning to these learners and they end up with misconceptions as they try to memorise facts in order to pass examinations. Learners are taught before writing these examinations, but how are they taught the concepts of Chemical Equilibrium? A descriptive approach was used on an exploratory survey conducted in Thohoyandou Cluster among Physical Science (Chemistry) FET band Educators. Cluster sampling of 40 educators from 18 randomly sampled schools responded to questionnaires. Five ‘well experienced’ educators who have been producing ‘good’ results at Grade 12 NSC examinations and two Physical Sciences subject advisors were interviewed. Using Spearman Brown Split-Half statistical method a 0,891 reliability coefficient was obtained. Research results show lack or under utilisation of laboratory equipment, teaching strategies which promote rote learning. Lack of confidence of educators due to deficiency in topic content knowledge and pedagogical skills which promote conceptual understanding were identified. Problem of English language leading to communication breakdown between educator-learners and between learner-subject leading to emergency of knowledge gaps in learners. Educators consider professional development through re-training and workshops on subject content matter and teaching strategies as the way forward to improve the quality of teaching. Topic specific PCK focusing on problem-solving strategy was recommended as a means to increasing educators’ efficiency in teaching and enhance learners’ comprehension and achievement in Physical Science. / Science and Technology Education / M. Sc. (Mathematics, Science and Technology Education (Chemistry Education))

Thesis (PhD)--Stellenbosch University, 2013. / Bibliography / ENGLISH ABSTRACT: This study investigated a single research question, that is: How do teachers experience the implementation of the Further Education and Training (FET) National Curriculum Statement (NCS) for Physical Science? The focus of the study was on searching the inner consciousness of Physical Science teachers as they engaged with the teaching of the subject on a daily basis. It is in the inner consciousness where one finds the truth about people’s perceptions, beliefs, emotions, challenges and convictions about/towards phenomena that the study sought to determine. In so doing, this study searched for phenomenological truth about the daily realities Physical Science teachers are faced with, as they implement the NCS. Phenomenological truth is floatable, precarious in nature, and subject to an individual’s perception of truth. It is important to note that phenomenological truth makes no reference to absolute truth. At the time this study was conducted the NCS was the only policy document with legal status for schools in South Africa. As a result the NCS influences and directs the pedagogical practices of teachers. This is because the NCS has a specific expectation of Physical Science teachers with regards to their understanding of the content, the delivery of the content, the learning environment, and professionalism. Through searching the consciousness of teachers, they revealed how they experienced what they do in the Physical Science classroom. In other words, how they experience what, how, when and who they teach. Probing into the consciousness of teachers and how they experience the implementation of the NCS provides valuable insight into the quality of curriculum delivery. This study did not only focus on the implementation of the NCS, but also examined why it might be difficult for teachers to change their practices. Phenomenology is both a theory and a method. The study was guided by the ideas of Edmund Husserl - who is regarded by many phenomenologists as the father of phenomenology, Martin Heidegger, Maurice Merleau-Ponty, and many other phenomenologists. Husserl (cited in Derrida, 1967) believed that we should begin any explanation with experience, which is a scientific description that does not presuppose any significance of the existence of the metaphysical world. By delving into the complexities of experience one can locate the flowing life of an individual’s consciousness as it occurs. Husserl posited the belief returning to the things themselves (cited in, Derrida, 1967; Spanos, 1976; Groenewald, 2004) to describe the purity of experience as data. In this study I sampled three teachers and employed a phenomenological methodological framework to capture their lived experiences. I used one-on-one semi-structured face-to-face interviews to construct the data. In addition, field notes were used to turn the direct experiences and observations of the participants into vivid descriptions. In phenomenology researchers use field notes to make the voice of people heard in the text. I drew on Husserl, Heidegger and Merleau-Ponty’s philosophical pathways that a person must be understood from his position within a specific time and place to present the findings. The major finding in this study showed that the teachers’ consciousness, with respect to Physical Science teaching was negatively influenced by the legacy of apartheid-education. This negative consciousness through which they framed their thoughts and filtered their ideas became the collective mindset through which they personified their teaching. The study revealed that the delivery of the NCS (by the teachers) was mostly axiomatised by old habits and images in their thoughts engrained in their memory under apartheid education. The findings also showed that their (teachers’) consciousness with regards to the NCS unconsciously oscillated between the present and the past and that they continuously and unconsciously bring the past (old ideas and beliefs) into the present. The teachers constantly have to struggle against the phenomenological self or attitude and ceaselessly suppose and follow thoughts of pre-comprehension or preconception. / AFRIKAANSE OPSOMMING: Die doelwit van hierdie studie was om die volgende navorsingvraag te beantwoord: Hoe ervaar onderwysers die implementering van die Verdere Onderwys en Opleiding (VOO) Nasionale Kurrikulum Verklaring (NKV) vir Fisiese Wetenskap? Die hoofdoel was om meer insig te verkry oor wat binne onderwysers se psige plaasvind soos hulle op ‘n daaglikse basis hul uitleef in die Fisiese Wetenskapsklaskamer binne die raamwerk van die NKV. Dit is binne die psige waar hul persepsies, diepgewortelde waardes, emosies, en uitdagings rondom die NKV rus. Om hierdie rede is die studie geïntresseerd om die fenomenologiese waarheid van die alledaagse realiteite waarmee hulle aanhoudend gekonfronteer word, te myn. Fenominologiese waarheid is vloeibaar en verskil van persoon tot persoon en hou geen verwysing met absolute waarheid nie. Toe hierdie studie plaasgevind het, was die VOO NKV die enigste wettige beleidsdokument vir die deelnemers. Die onderwysers was dus verplig om die voorgeskrewe beginsels soos in die NKV saamgevat toe te pas in die voorbereiding en aanbieding van hul lesse. Die NKV beskryf in diepte die inhoud vir elke graad (10-12), hoe die inhoud aangebied moet word, die klaskamer atmosfeer, asook die professionalitiet van die opvoeders. Al die antwoorde soos saamgevat in laasgenoemde, lê bine die psige van die onderwysers. Die ondersoek van die psige van die onderwysers lei tot ‘n begrip van hoe, wat en waarom Fisiese Wetenskaps-onderswysers doen wat hulle doen. Alhoewel die fokus van hierdie studie op die implementering van die NKV is, dra dit ook by tot groeiende kennis aangaande hoekom onderwysers dit moeilik vind om hulle praktyke te verander wanneer dit kom by die hernuwing van ‘n kurrikulum. Fenomenologie is beide ‘n navorsingsmetode en ‘n teorie. Die literatuuroorsig van hierdie studie is geinspireer deur die idees van Edmund Husserl, wat bestempel word as die vader van fenomenolgie, asook Martin Heidegger, Maurice Merleau-Ponty, en veskeie ander fenomenoloë. Derrida (1967) is oortuig daarvan dat enige verduideliking akkuraat beskryf kan word indien geleefde ervaring in ag geneem word. Geleefde ervaring spreek direk tot die onderliggende psige van ‘n individu, en deur die psige te ondersoek, is dit moontlik om ‘n individu se oortuigings ten opsigte van sy/haar geloof, persepsies en uitdagings, asook hoe die individu reageer op hierdie aspekte te verstaan. Husserl gebruik die uitdrukking ‘returning to the things themselves’ wanneer hy verwys na die belangrikheid en oorspronlikheid van ervaring (vermeld in, Derrida, 1967; Spanos, 1976; Groenewald, 2004). Om hierdie rede is ‘n fenomenologiese metode gevolg om die lewenservaringe van drie swart onderwysers vas te vang. Hierdie fenomenologiese vertolkende ondersoek word deur veelvoudigemetodes van inligtingsinsameling gekenmerk. Inligting in hierdie studie oor die deelnemers se ervaringe is vekry deur middel van individuele onderhoude, en die ontleding van die inhoud daarvan. Addisionele inligting is verkry deur veldnotas. Die doelwit van die veldnotas was om die deelnemers se direkte ervaringe en waarnemings in besonderhede te beskryf. Die ontledingsbenadering van elke deelnemer is gedoen binne die raamwerk van Husserl, Heidegger en Merleau-Ponty wat gegrond is op teorieë wat die belangrikheid van plek en tyd uitbeeld. Die resultate van hierdie studie het getoon dat die onderliggende psige van elke deelnemer deur die nalatenskap van apartheid negatief beïnvloed is. Hierdie negatiewe denkpatrone waardeur die onderwysers se idees formuleer vorm die kollektiewe ingesteldheid waardeur hulle hul onderrigswêreld skep. Verder het die studie onthul dat hul aanbieding van die NKV meestal gedryf word deur ou gewoontes wat binne hul denke gekristalliseer het. Hulle vind dit dus moeilik om deur hierdie ou gewoontes te breek. Hul denke wissel gedurig tussen die verlede en die hede en roep die verlede voortdurend binne die hede. Alhoewel die bevindinge van hierdie studie gekoppel is aan plek en tyd is daar ‘n konstante struweling tussen die fenomenologiese self en hul ou gesette denke.

The aim of this study is to ascertain what misconceptions N2 students have about DC resistive circuits and how screencasts could effect on the rectification of these misconceptions. This study was conducted at the Kathu Campus of the Northern Cape Rural Further Education and Training College in the town Kathu in the arid Northern Cape. The empirical part of this study was conducted during the first six months of 2013. A design-based research (DBR) method consisting of four phases was used. DBR function is to design and develop interventions such as a procedure, new teachinglearning strategies, and in the case of this study a technology-enhanced learning (TEL) tool (screencast) with the purpose of solving a versatile didactic problem and to acquire information about the interventions of the TEL tool (screencast) on the learning of a student. In the first and second phase of DBR quantitative data for this research were gathered with the Determining and Interpreting Resistive Electric circuits Concepts Test (DIRECT) in order to determine the four most common misconceptions. The DIRECT test was conducted in the first trimester to find the misconceptions; the test was conducted in the second trimester also to confirm the misconceptions. Further quantitative data were collected from a demographic questionnaire. The qualitative data were collected by individual interviews in the fourth phase of the research project. Phase three of this study was the development of screencasts in the four most prominent misconceptions in DC resistive circuits of the students. The respondents of this study were non-randomly chosen and comprised of two groups, one in the first trimester of the year and one in the second trimester of the year, which enrolled for the N2 Electrical or Millwright courses. The respondents were predominant male and representing the three main cultural groups in the Northern Cape namely: Black, Coloured and White. The four misconceptions on DC resistive circuits that were identified were: (i) understanding of concepts, (ii) understanding of short circuit, (iii) battery as a constant current source, and (iv) rule application error. Screencasts clarifying the four misconceptions were developed and distributed to the respondents. On the foundation of the results of this research, it can be concluded that the students have several misconceptions around direct current resistive direct current circuits and that the use of TEL like screencasts can be used to solve some of these misconceptions. Screencasts could supplement education when they were incorporated into the tutoring and learning for supporting student understanding. The results of this research could lead to the further development and refinement of screencasts on DC resistive circuits and also useable guidelines in creating innovative screencasts on DC resistive circuits. / MEd (Curriculum Development), North-West University, Potchefstroom Campus, 2014

Passive sampling, as opposed to the conventional spot or bottle water sampling technique, has shown to be reliable and efficient in monitoring the toxicologically relevant, freely dissolved (e.g. bioavaialable) concentrations of a wide range of organic contaminants in water. At the same time, partitioning controlled delivery (passive dosing; PD) techniques promise to overcome many of the challenges associated with toxicity testing of hydrophobic substances that may bias the interpretation of toxicity data. The present study investigated the feasibility of coupling silicone rubber passive sampling devices (SR-PSDs) with bioassay techniques for both chemical and ecotoxicological assessment of complex mixtures of organic contaminants in the aquatic environment. SR-PSDs were deployed in water at various locations within the Ythan catchment (north east, Scotland, UK), Forth estuary and the Firth of Forth (east coast of central Scotland, UK) for 7 to 9 weeks. Following retrieval, extracts from the SR-PSDs were analysed for dissolved concentrations of a variety of organic contaminants including PAHs and PCBs using GC-MS and GC-ECD respectively and were screened for a wide range of pesticides using GC-MS/MS and LC-MS/MS. The extracts were further evaluated for acute cytotoxicity (i.e. neutral red uptake assay) and EROD induction potential using rainbow trout liver cell line (Oncorhynchus mykiss; RTL-W1) and for phytotoxicity and developmental toxicity potential using algal growth inhibition test (with a marine phytoplankton, Diacronema lutheri) and fish embryo toxicity test (with embryos from zebrafish Danio rerio) respectively. Overall, the individual and total dissolved concentrations of PAHs (ΣPAH40; parent and branched) and PCBs (ΣPCB32; ortho and mono-ortho) measured in water from the Ythan, Forth estuary and Firth of Forth were relatively low compared with other studies using PSDs. A number and level of pesticides, including insecticides, herbicides and fungicides of varying hydrophobicity (log KOWs ~2.25 to ~5.31) were detected in the silicone rubber (SR) extracts from the Ythan catchment, the Forth estuary and the Firth of Forth, suggesting input mainly from agricultural run-off and possibly from direct discharges. No statistically significant (p<0.05) acute cytotoxicity was observed following 48 h exposure of RTL-W1 cells to SR extracts from the Ythan catchment. But, on a sublethal level, for every site, statistically significant EROD activity was observed to some degree following 72 h exposure. In addition, developmental and algal toxicities on embryos of D. rerio and D. lutheri respectively, were measured in all the deployed samples compared with the procedural controls (undeployed samples). Interestingly, extracts of SR-PSDs from the Forth estuary and the Firth of Forth exhibited growth inhibitions on D. lutheri that were similar to those of extracts from the Ythan, even though, fewer numbers of pesticides were detected in the Forth estuary and Firth of Forth than the Ythan. This suggests that pesticides were not solely responsible for the observed effects in the Ythan catchment. To further improve data from toxicity testing of hydrophobic substances, the study identified the use of SR O-rings as a suitable passive dosing format in in vitro toxicity tests and was partially validated through their use in dosing RTL-W1 cells with two individual PAHs and subsequently determining cytotoxicity and EROD-activity.

Cette thèse porte sur l’étude de transistor à effet tunnel (TFET) en FDSOI à géométries planaire et triple grille/nanofils. Nous rapportons pour la première fois des TFETs fabriqués par un processus basse température (600°C), qui est identique à celui utilisé pour l’intégration monolithique 3D. La méthode “Dual IDVDS” confirme que ces TFETs fonctionnent par effet tunnel et non pas par effet Schottky. Les résultats des mesures électriques montrent que l’abaissement de la température de fabrication de 1050°C (HT) à 600°C (LT) ne dégrade pas les propriétés des TFETs. Néanmoins, les dispositifs réalisés à basse température montrent un courant de drain et de fuite plus élevés et une tension de seuil différente par rapport aux HT TFETs. Ces phénomènes ne peuvent pas être expliqués par le mécanisme d’effet tunnel. Le courant de pompage de charges révèle une densité d’états d’interface plus grande à l’interface oxide/Si pour les dispositifs LT que dans les TFETs HT pour les zones actives étroites. Par ailleurs, une analyse de bruit basse fréquence permet de mieux comprendre la nature des pièges dans les TFETs LT et HT. Dans les TFETs réalisés à basse température nous avons mis en évidence une concentration en défauts non uniforme à l’interface oxide/Si et à la jonction tunnel qui cause un effet tunnel assisté par piège (TAT). Ce courant TAT est responsable de la dégradation de la pente sous seuil. Ce résultat montre la direction à suivre pour optimiser ces structures, à savoir une épitaxie de très haute qualité et une optimisation fine des jonctions. Finalement, nous avons proposé de nouvelles architectures innovatrices de transistors à effet tunnel. L’étude de simulation TCAD montre que l’extension de la jonction tunnel dans le canal augmente la surface de la région qui engendre le courant BTBT. Une fine couche dopée avec une dose ultra-haute en bore pourrait permettre l’obtention à la fois d’une pente sous le seuil faible et un fort courant ON pour le TFET. / This thesis presents a study of FDSOI Tunnel FETs (TFETs) from planar to trigate/nanowire structures. For the first time we report functional “Low-Temperature” (LT) TFETs fabricated with low-thermal budget (630°C) process flow, specifically designed for top tier devices in 3D sequential integration. “Dual IDVDS” method confirms that these devices are real TFETs and not Schottky FETs. Electrical characterization shows that LT TFETs performance is comparable with “High-Temperature” (HT) TFETs (1050°C). However, LT TFETs exhibit ON-current enhancement, OFF-current degradation and VTH shift with respect to HT TFETs that cannot be explained via BTBT mechanism. Charge pumping measurements reveal a higher defect density at the top silicon/oxide interface for geometries with narrow widths in LT than HT TFETs. In addition, low-frequency noise analyses shed some light on the nature of these defects. In LT TFETs, we determined a non-uniform distribution of defects at the top surface and also at the tunneling junction that causes trap-assisted tunneling (TAT). TAT is responsible of the current generation that degrades the subthreshold swing. This indicates the tight requirements for quality epitaxy growth and junction optimization in TFETs. Finally, we proposed novel TFET architectures. TCAD study shows that the extension of the source into the body region provides vertical BTBT and a larger tunneling surface. Ultra-thin heavily doped boron layers could allow the possibility to obtain simultaneously a good ON-current and sub-thermal subthreshold slope in TFETs.

This doctoral thesis explores HR management through systems of production incentives in the construction sector which has been instrumental to the Spanish economy. The transformation of a time-based payment system to a performance or production-based payment system is difficult if you consider the complexity of the calculation and the environment in which prices are negotiated. In any case, before agreeing to a piece-rate determined price it is imperative that the person responsible for negotiating on behalf of the company knows the relationship of this piece rate compared to expected labour costs as an objective in the opening plans. The main objective of this thesis is to propose an algorithm in flowchart form that facilitates —from the data found in the costs study— knowledge about the price range within which the economic incentive for piece-rate compensation for any work should be established by applying a few simple conversion coefficients proposed by the model itself / Aquesta tesi doctoral es centra en la gestió dels recursos humans a través dels sistemes d'incentius a la producció. La transformació d'un sistema de pagament per temps a un sistema de pagament per rendiment o per producció no és senzill si es té en compte la complexitat del càlcul i l'entorn en el qual es pacten els preus. És imprescindible que abans d'acordar un determinat preu fet, el responsable de la negociació, conegui la relació d'aquest preu respecte els costos de mà d'obra que té previstos com a objectiu en el pressupost de producció. El principal objectiu d'aquesta tesi és proposar un algoritme que faciliti —a partir de les dades contingudes en l'estudi de costos—, conèixer l'interval de preus dins del qual s'hauria d'establir l'incentiu econòmic de remuneració a preu fet d'un treball qualsevol, mitjançant l'aplicació d'uns simples coeficients de conversió que proposa el propi model

Today there is a great deal of interest in the development of gas sensors for applications like air pollution monitoring, indoor environment control, detection of harmful gases in mines etc. Based on different sensing principles, a large variety of sensors such as semiconductor gas sensors, thermoelectric gas sensors, optical sensors and thermal conductivity sensors have been developed. The present thesis reports a detailed account of a novel method followed for the design and development of a thermoelectric gas sensor for sensing of Volatile Organic Compounds. Thermoelectric effect is one of the highly reliable and important working principles that is widely being put into practical applications. The thermoelectric property of semiconducting tin oxide film has been utilized in the sensor that has been developed. The thermoelectric property of semiconducting tin oxide film has been utilized in the sensor. The deposition parameters for sputtering of tin oxide film have been optimized to obtain a high seebeck coefficient. A test set-up to characterize the deposited films for their thermoelectric property has been designed and developed. A novel method of increasing the seebeck coefficient of tin oxide films has been successfully implemented. Thin films of chromium, copper and silver were used for this purpose. Deposition of the semiconducting oxide on strips of metal films has led to a noticeable increase in the seebeck coefficient of the oxide film without significantly affecting its thermal conductivity. The next part of our work involved development of a gas sensor using this thermoelectric film. These sensors were further tested for their response to volatile organic compounds. The sensor showed significant sensitivity to the test gases at relatively low temperatures. In addition to this, the developed sensor is also selective to acetone gas.