Graphene is widely considered to be a promising candidate for a new generation of electronics, but there are many outstanding fundamental issues that need to be addressed before this promise can be realized. This thesis focuses on the production and properties of graphene grown epitaxially on the carbon terminated face (C-face) of hexagonal silicon carbide leading to the construction of a novel graphene transistor structure. C-face epitaxial graphene multilayers are unique due to their rotational stacking that causes the individual layers to be electronically decoupled from each other. Well-formed C-face epitaxial graphene single layers have exceptionally high mobilities (exceeding 10,000 cm ²/Vs), which are significantly greater than those of Si-face graphene monolayers. This thesis investigates the growth and properties of C-face single layer graphene. A field effect transistor based on single layer graphene was fabricated and characterized for the first time. Aluminum oxide or boron nitride was used for the gate dielectric. Additionally, an all graphene/SiC Schottky barrier transistor on the C-face of SiC composed of 2DEG in SiC/Si₂O ₃ interface and multilayer graphene contacts was demonstrated. A multiple growth scheme was adopted to achieve this unique structure.

This thesis reports a comprehensive study of quaternary BeMgZnO alloy and BeMgZnO/ZnO heterostructures for UV-optoelectronics electronic applications. It was shown that by tuning Be and Mg contents in the heterostructures, high carrier densities of two-dimensional electron gas (2DEG) are achievable and makes its use possible for high power RF applications. Additionally, optical bandgaps as high as 5.1 eV were achieved for single crystal wurtzite material which allows the use of the alloy for solar blind optoelectronics (Eg>4.5eV) or intersubband devices. A systematic experimental and theoretical study of lattice parameters and bandgaps of quaternary BeMgZnO alloy was performed for the whole range of compositions. Composition independent bowing parameters were determined which allows accurate predictions of experimentally measured values. The BeMgZnO thin films were grown by plasma assisted molecular beam epitaxy (P-MBE) in a wide range of compositions. The optimization of the growth conditions and its effects on the material properties were explored. The surface morphology and electrical characteristics of the films grown on (0001) sapphire were found to critically depend on the metal-to-oxygen ratio. Samples grown under slightly oxygen-rich conditions exhibited the lowest RMS surface roughness (as low as 0.5 nm). Additionally, the films grown under oxygen-rich conditions were semi-insulating (>105 Ω∙cm), while the films grown under metal-rich conditions were semiconducting (~102 Ω∙cm). Additionally, with increasing bandgap Stokes shift increases, reaching ~0.5 eV for the films with 4.6 eV absorption edge suggests the presence of band tail states introduced by potential fluctuations and alloying. From spectrally resolved PL transients, BeMgZnO films grown on a GaN/sapphire template having higher Mg/Be content ratio exhibit smaller localization depth and brighter photoluminescence at low temperatures. The optimum content ratio for better room temperature optical performance was found to be ~2.5. The BeMgZnO material system and heterostructures are promising candidates for the device fabrication. 2DEG densities of MgZnO/ZnO heterostructures were shown to improve significantly (above 1013 cm-2) by adding even a small amount of Be (1-5%). As an essential step toward device fabrication, reliable ohmic contacts to ZnO were established with remarkably low specific contact resistivities below 10-6 Ohm-cm2 for films with 1018 cm-3 carrier density.

The analysis of this thesis is to examine whether foreign investors can fully rely on the standard of FPS in BITs for the protection of their investments in the territories of host States which has been mandated to States by international law. This question cannot be answered without giving insights into the content and structure of the origin of FPS standard and adopts a dynamic based-perspective of the interpretation of FPS under VCLT 1969, encompassing the relationship between FPS and CIL. It investigates the tribunals' interpretation of the clause using case laws and literatures to identify and explore the underlying explanatory process behind tribunals' case findings and outcomes. The study examines the critical realism that the obligation of FPS standard does not place absolute liability to a host State, rather the exercise of a reasonable degree of vigilance. It evaluates the controversy surrounding the relationships between FPS and FET, and illuminates on how the two standards may co-evolve which has led to various arbitral tribunals' divergence opinions interpretation of the two principles. The evaluation of the application of FPS to digital assets is dynamic in this research as it addresses the nature of threats investors face globally today over cyber attacks of digital investments. The thesis also emphasis on balancing up investors' rights and obligation, which explains the measures that States can apply to prevent foreign investors from engaging in illegitimate activities. Having look at all these issues, circumstances, and the controversies surrounding FPS standard, the result found is that there is a existence of a gap in this area of the law, that would mean that foreign investors cannot completely rely on the principle of FPS for the protection of their investments in the territories of the host unless this lacunae is properly filled by both the States and arbitral tribunals, especially the tribunals' interpretative meaning of the standard of FPS.

Efeitos causados pela interação da radiação ionizante em dispositivos eletrônicos consis- tem numa preocupação crescente em diversos segmentos, como as aplicações aeroespaci- ais e em física de altas energias. Entre os efeitos de radiação induzidos por íons pesados estão os chamados de Efeitos de Eventos Isolados (Single Event Effects - SEE), em que o impacto de um único íon pode ser capaz de gerar um efeito observável, através da elevada deposição de energia e consequente geração de pares elétron-lacuna. O estudo destes efeitos requer um acelerador de partículas capaz de prover feixes uniformes de íons pesados com baixo fluxo. Neste trabalho, desenvolvemos um sistema para produ- ção de feixes de íons pesados para estudar SEE no Acelerador Pelletron 8UD, utilizando as técnicas de desfocalização e espalhamento múltiplo em folhas de ouro. O sistema foi projetado para prover feixes com intensidades entre 10 2 e 10 5 partículas/s/cm 2 com uniformidade maior que 90% numa área circular de diâmetro de 1,5 cm, operando em regime de alto-vácuo. Um manipulador de amostras permite a movimentação do dispo- sitivo sob teste com precisão de 2,5 m e um sistema de aquisição de dados dedicado foi desenvolvido, permitindo a automação de medidas. O sistema foi caracterizado com feixes de 1 H, 12 C, 16 O, 19 F, 28 Si, 35 Cl e 63 Cu a várias energias, apresentando fluxo e uni- formidade adequados aos experimentos em diversas configurações de focalização e folhas espalhadoras, e tem sido utilizado por diversos grupos de pesquisa. O novo sistema foi utilizado para estudar o efeito das camadas de isolamento e metalização na coleta de carga e geração de eventos observáveis em um dispositivo analógico e em um disposi- tivo digital, de modo a estabelecer metodologias de trabalho adequadas para estudos precisos de mecanismos de ocorrência de efeitos de radiação. O dispositivo analógico estudado foi um transistor p-MOS, onde o sinal de corrente induzido pelo impacto de íons diversos foi analisado de modo a obter a seção de choque de eventos e a cargaix gerada, permitindo determinar a espessura da camada de metalização em 1,28(2) m, e a camada de coleta de carga dependente do LET e alcance da partícula incidente, variando entre 6,0 e 11,0 m. O dispositivo digital estudado foi uma memória SRAM 28nm, onde foi observada uma forte dependência da seção de choque de eventos com a penetração do feixe no dispositivo. Associando as camadas de metalização e isolamento a um meio efetivo de interação, obteve-se que toda a área sensível do dispositivo só pode ser excitada, isto é, nela ocorrerem eventos observáveis, para partículas com alcance, no meio efetivo, entre 14 e 20 m, embora partículas com alcance de até 10 m sejam capazes de sensibilizar até 50% da área ativa do dispositivo. / Effects on electronic devices caused by interactions of ionizing radiation are a main concern in several fields, such as aerospace applications and high-energy physics. Among the heavy-ion induced radiation effects are the Single Event Effects, in which a strike of a single ion can be enough to generate an observable effect, as a result of the high energy deposition and thus electron-hole pairs generation. The study of these effects requires the use of uniform, low-flux particle beams. In this work, we developed a system for production of heavy ion beams for SEE studies at Pelletron 8UD accelerator, through the defocusing and multiple scattering in gold foil techniques. The setup can provide ion beams with intensities ranging from 10 2 e 10 5 particles/s/cm 2 with uniformity better than 90% in an circular area of 1.5 cm diameter, operating under high-vacuum. A sample manipulador allows device under test positioning with a precision of 2.5 m, and a dedicated data acquisition system was developed, allowing measurement automation. The system was characterized with 1 H, 12 C, 16 O, 19 F, 28 Si, 35 Cl and 63 Cu ion beams at several energies, presenting flux and uniformity adequate for SEE studies in many different configurations, and it is being used by several research groups. The new facility was used to study the effect of isolation and metalization layers in charge collection and observable events generation in an analog and in a digital device, in order to establish proper metodologies for precise studies of radiation effects mecanisms. The analog device studied was a p-MOS transitor, from which the heavy-ion impact induced current signal was analised to obtain cross-section and colected charge, allowing to determine metalization layer thickness to be 1.28(2) m, and charge collection dependency on particle LET and range, varying from 6.0 to 11.0 m. The digital device studied was a 28nm SRAM memory, where a strong dependency of cross-section with particle range in the device was observed. Associating to the metal and insulating layers an effectivexi medium, it was observed that the complete sensitive area can be excited only by particle with ranges in effective medium between 14 and 20 m, although particles with ranges up to 10 m are capable of sensibilizing up to 50% of devices active area.

A major difficulty in the fabrication of nanostructure based electronics is the lack of effective processes capable of precisely arranging nanostructures into predefined positions. Top-down approaches introduce increased complexity and a high cost for practical industrial use, while bottom-up approaches are probabilistic in nature and do not provide precise control of nanostructure properties (i.e., number, diameter), which influence device performance. Alternatively, nanomanipulation promises specificity, precision and programmed motion and its automation may facilitate the large-scale fabrication of nanostructure based devices. This study focuses on the development of an automated contact detection algorithm which positions an end-effector in contact with a target surface without the need for additional equipment, devices or sensors. We demonstrate this algorithm as an enabling feature for automated nano-FET biosensor construction with precise control over nanowire parameters thereby reducing device-to-device variability and also potentially allowing us to optimize individual device performance.

A major difficulty in the fabrication of nanostructure based electronics is the lack of effective processes capable of precisely arranging nanostructures into predefined positions. Top-down approaches introduce increased complexity and a high cost for practical industrial use, while bottom-up approaches are probabilistic in nature and do not provide precise control of nanostructure properties (i.e., number, diameter), which influence device performance. Alternatively, nanomanipulation promises specificity, precision and programmed motion and its automation may facilitate the large-scale fabrication of nanostructure based devices. This study focuses on the development of an automated contact detection algorithm which positions an end-effector in contact with a target surface without the need for additional equipment, devices or sensors. We demonstrate this algorithm as an enabling feature for automated nano-FET biosensor construction with precise control over nanowire parameters thereby reducing device-to-device variability and also potentially allowing us to optimize individual device performance.

A fast and efficient hierarchical optimization engine was developed to benchmark and optimize various emerging device and interconnect technologies and system-level innovations at the early design stage. As the semiconductor industry approaches sub-20nm technology nodes, both devices and interconnects are facing severe physical challenges. Many novel device and interconnect concepts and system integration techniques are proposed in the past decade to reinforce or even replace the conventional Si CMOS technology and Cu interconnects. To efficiently benchmark and optimize these emerging technologies, a validated system-level design methodology is developed based on the compact models from all hierarchies, starting from the bottom material-level, to the device- and interconnect-level, and to the top system-level models. Multiple design parameters across all hierarchies are co-optimized simultaneously to maximize the overall chip throughput instead of just the intrinsic delay or energy dissipation of the device or interconnect itself. This optimization is performed under various constraints such as the power dissipation, maximum temperature, die size area, power delivery noise, and yield. For the device benchmarking, novel graphen PN junction devices and InAs nanowire FETs are investigated for both high-performance and low-power applications. For the interconnect benchmarking, a novel local interconnect structure and hybrid Al-Cu interconnect architecture are proposed, and emerging multi-layer graphene interconnects are also investigated, and compared with the conventional Cu interconnects. For the system-level analyses, the benefits of the systems implemented with 3D integration and heterogeneous integration are analyzed. In addition, the impact of the power delivery noise and process variation for both devices and interconnects are quantified on the overall chip throughput.

Neuf ans sont passés depuis la découverte du graphène, tous très dense de travaux de recherche et publications que, petit à petit, ont mieux illuminé les propriétés de ce matériau extraordinaire. Avec une meilleure compréhension de ses meilleures qualités, une idée plus précise des applications que mieux pourront profiter de son use a été défini. Dispositifs à haute fréquence, comme mélangeurs et amplificateurs de puissance, et l'électronique Flexible et Transparent sont les domaines les plus prometteurs. Dans ces domaines une grande attention est dévouée à deux sujets : la réduction des dimensions des transistors à base de graphène, pour réduire le temps de propagation des porteurs de charge et atteindre des pourcentages de transport balistique toujours plus élevés ; et l'optimisation des parasites de contact. Tout les deux sont très bénéfiques pou la maximisation des figures de mérite du dispositif. En cette thèse, deux modèles ont été développés pour aborder ces sujets : le premier est dédié aux transistors quasi-balistiques de graphène de grande surface comme aussi aux transistors graphène nano-ruban. Ceci démontre la corrélation entre le transport balistique et diffusive et la longueur du dispositif, et extrait les courants DC grand signal et les transconductances. Le second reproduit la conduction à haute fréquence à travers le graphène et son impédance parasite de contact. Le dernier modèle a aussi motivé la conception et fabrication d'un test bed RF sur une technologie dédié sur plastique, fait qui permet la caractérisation RF de l'impédance de contact et de l'impédance spécifique d'interface avec du graphène monocouche accru par CVD.

Since 2006 Further Education and Training (FET) Colleges have been recapitalised through massive government investment in order to improve infrastructure, implement a more relevant curriculum and assist college learners financially to gain access to the different learning programmes. A new curriculum with 11 programmes was introduced and implemented under the National Certificate Vocational (NCV). The results of the 2007 examinations, were disappointing and in general, the national performance of the learners was dismal. Policy requirements for certification and promotion to the next level stipulated that learners need to pass all 7 subjects in a programme. The main aim of the study was to identify variables that are the best predictors of academic success of first year FET students. Thus, if these predictors are considered during the admission process of first year FET students, it could lead to overall improved first year pass rate at FET Colleges and contribute towards the enhancement of human resources and economical development of our country. In order to achieve the research aim and objectives, a literature study and an empirical investigation were conducted. The literature study focussed on cognitive and non-cognitive factors that contribute to academic success of students at colleges. The empirical investigation departed from a positivist paradigm to determine which variables contributed the best towards the prediction of academic success of first year NCV Level 2 students at FET Colleges and a quantitative non-experimental, ex post facto approach was followed .The results of the General Scholastic Aptitude Test (GSAT), the Learning and Study Strategies Inventory – High School version (LASSI-HS), grade mark average and biographical details of the registered first year NCV Level 2 students of the Vuselela FET College (Potchefstroom and Klerksdorp campuses) in 2008 (n=309), were used to determine whether any of these variables significantly predicted the academic success of these students. The investigation revealed that: • None of the LASSI-HS scales were predictors of academic success of the first year NCV Level 2 students; • The GSAT (Total) was a predictor of academic success of these students; • None of the biographical variables, i.e. age or gender, were predictors of academic success; and • Grade mark average on students’ last school reports, was a predictor of academic success. These findings revealed that Grade mark average, and GSAT-(Total) (which is also an indication of intelligence quotient (IQ)) were the best predictors of academic success of first year NCV Level 2 students at the Potchefstroom and Klerksdorp campuses of the Vuselela FET College. / Thesis (MEd (Educational Psychology))--North-West University, Potchefstroom Campus, 2013.

Since 2006 Further Education and Training (FET) Colleges have been recapitalised through massive government investment in order to improve infrastructure, implement a more relevant curriculum and assist college learners financially to gain access to the different learning programmes. A new curriculum with 11 programmes was introduced and implemented under the National Certificate Vocational (NCV). The results of the 2007 examinations, were disappointing and in general, the national performance of the learners was dismal. Policy requirements for certification and promotion to the next level stipulated that learners need to pass all 7 subjects in a programme. The main aim of the study was to identify variables that are the best predictors of academic success of first year FET students. Thus, if these predictors are considered during the admission process of first year FET students, it could lead to overall improved first year pass rate at FET Colleges and contribute towards the enhancement of human resources and economical development of our country. In order to achieve the research aim and objectives, a literature study and an empirical investigation were conducted. The literature study focussed on cognitive and non-cognitive factors that contribute to academic success of students at colleges. The empirical investigation departed from a positivist paradigm to determine which variables contributed the best towards the prediction of academic success of first year NCV Level 2 students at FET Colleges and a quantitative non-experimental, ex post facto approach was followed .The results of the General Scholastic Aptitude Test (GSAT), the Learning and Study Strategies Inventory – High School version (LASSI-HS), grade mark average and biographical details of the registered first year NCV Level 2 students of the Vuselela FET College (Potchefstroom and Klerksdorp campuses) in 2008 (n=309), were used to determine whether any of these variables significantly predicted the academic success of these students. The investigation revealed that: • None of the LASSI-HS scales were predictors of academic success of the first year NCV Level 2 students; • The GSAT (Total) was a predictor of academic success of these students; • None of the biographical variables, i.e. age or gender, were predictors of academic success; and • Grade mark average on students’ last school reports, was a predictor of academic success. These findings revealed that Grade mark average, and GSAT-(Total) (which is also an indication of intelligence quotient (IQ)) were the best predictors of academic success of first year NCV Level 2 students at the Potchefstroom and Klerksdorp campuses of the Vuselela FET College. / Thesis (MEd (Educational Psychology))--North-West University, Potchefstroom Campus, 2013.