Doctor of Philosophy / Department of Chemical Engineering / Vikas Berry / Graphene - a single atom thick two dimensional sheet of sp[superscript]2 bonded carbon atoms arranged in a honeycomb lattice - has shown great promise for both fundamental research & applications because of its unique electrical, optical, thermal, mechanical and chemical properties. Derivatization of graphene unlocks a plethora of novel properties unavailable to their pristine parent “graphene”. In this dissertation we have synthesized various structural and chemical derivatives of graphene; characterized them in detail; and leveraged their exotic properties for diverse applications. We have synthesized protein/DNA/ethylenediamine functionalized derivatives of graphene via a HATU catalyzed amide reaction of primary-amine-containing moieties with graphene oxide (GO) – an oxyfunctional graphene derivative. In contrast to non-specificity of graphene, this functionalization of GO has enabled highly specific interactions with analytes. Devices fabricated from the protein (concanavalin – A) and DNA functionalized graphene derivatives were demonstrated to enable label-free, specific detection of bacteria and DNA molecules, respectively, with single quanta sensitivity. Room temperature electrical characterization of the sensors showed a generation of ~ 1400 charge carriers for single bacterium attachment and an increase of 5.6 X 10[superscript]12 charge carriers / cm[superscript]2 for attachment of a single complementary strand of DNA. This work has shown for the first time the viability of graphene for bio-electronics and sensing at single quanta level. Taking the bio-interfacing of graphene to the next level, we demonstrate the instantaneous swaddling of a single live bacterium (Bacillus subtilis) with several hundred sq. micron (~ 600 µm[superscript]2) areal protein-functionalized graphene sheets. The atomic impermeability and high yield strength of graphene resulted in hermetic compartmentalization of bacteria. This enabled preservation of the dimensional and topological characteristics of the bacterium against the degrading effects of harsh environments such as the ultrahigh vacuum (~ 10[superscript]-5 Torr) and high intensity electron beam (~ 150 A/cm[superscript]2) in a transmission electron microscope (TEM) column. While an unwrapped bacterium shrank by ~ 76 % and displayed significant charge buildup in the TEM column; a wrapped bacterium remained uncontracted and undamaged owing to the graphenic wraps. This work has shown for the first time an impermeable graphenic encasement of bacteria and its application in high vacuum TEM imaging without using any lengthy traditional biological TEM sample preparation techniques. In an inch-scale, we fabricated robust free-standing paper composed of TWEEN/Graphene composite which exhibited excellent chemical stability and mechanical strength. This paper displayed excellent biocompatibility towards three mammalian cell lines while inhibiting the non-specific binding of bacteria (Bacillus cereus). We predict this composite and its derivatives to have excellent applications in biomedical engineering for transplant devices, invasive instrument coatings and implants. We also demonstrate a novel, ultra-fast and high yield process for reducing GO to reduced graphene oxide (RGO) using a facile hydride-based chemistry. The RGO sheets thus-produced exhibited high carrier mobilities (~ 100-600 cm[superscript]2/V•s) and reinstatement of the ambipolar characteristic of graphene. Raman spectra and UV-Vis spectroscopy on the RGO sheets displayed a high degree of restoration of the crystalline sp2 lattice with relatively low defects. We fabricated graphene nanoribbons (GNRs) – 1D structural derivatives of graphene – using a nano-scale cutting process from highly oriented pyrolytic graphite (HOPG) blocks, with widths pre-determinable between 5 nm to 600 nm. The as-produced GNRs had very high aspect ratio in the longitudinal direction (~ 0.01); exhibited predominantly mono-layered structure (< 10 % bilayer); and smooth edges (Raman I[subscript]D/G ~ 0.25 -0.28). Low temperature electrical transport measurements on back-gated thin film GNR devices were performed and a carrier mobility of ~ 20 ± 4 cm[superscript]2/V•s with sheet resistances of 2.2-5.1 MΩ / □ was extracted. Despite the ~ 50 nm thicknesses of the films, a clear bandgap scaling was observed with transport via variable range hopping (VRH) in 2 and 3 dimensions. This work demonstrates the first fully functional narrow pristine GNR thin-film field effect transistors (FETs). In addition we fabricated graphene quantum dots (GQDs) – 0D derivatives of graphene with dimensions < 100 nm – using a slight variation of our nano-scale cutting strategy, where the cleavage process is carried out in two dimensions. A high degree of control on the dimensions (Std. Dev. of ~ 5 nm for 50 X 50 nm square GQDs) and shape (pre-determinable between square, rectangle, triangle and trapezoid) of the as-synthesized GQDs is demonstrated. The optical properties of the GQDs such as the UV-Vis absorbance and photoluminescence were studied and their facile tunability was demonstrated depending on their dimensions. This work demonstrates for the first time the high throughput fabrication of GQDs with tunable dimensions and shape.

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Thesis (PhD)--Stellenbosch University, 2012. / Includes bibliography / ENGLISH ABSTRACT: During the Decade of Education for Sustainable Development (DESD) (2004-2015), better teaching and learning of environmental education and education for sustainable development (EE and ESD) in schools is one of the main responses to the worsening state of the global environment. Environmental concerns are integrated into the South African school curricula; in the General Education and Training (Grades R-9) (GET) and Further Education and Training (FET) phases through the principles that underpin the curricula such as social justice, a healthy environment, human rights and inclusivity. While a cross-curricula approach to teaching and learning is followed in the GET phase, environmental concerns are infused in each subject at FET level. Because geography deals with human-environment relationships and is interdisciplinary, it is considered to be one of the main vehicles for teaching EE and ESD. To respond to the need for better teaching and learning of EE and ESD during the DESD, the main aim of this research project was to find out how EE and ESD are being implemented through the geography curriculum in South African secondary schools at FET level. The investigation sought answers to questions related to: opportunities for teaching EE and ESD in the geography National Curriculum Statement; the geography teachers’ perspectives on EE and ESD; the extent to which the teachers incorporate the teaching of EE and ESD in the geography lessons; pedagogical approaches used by the geography teachers; and, the barriers to teaching environmental concerns through the geography curriculum. A qualitative case study research design, underpinned by the interpretive research paradigm, was used. A sample of 10 senior geography teachers comprising 8 males and 2 females participated in the study. They were drawn from five Western Cape secondary schools selected through purposeful sampling in such a way that the sample of schools is representative of the socio-economic and sociocultural context of the Western Cape as far as possible. Data were generated from biographic questionnaires and semi-structured interviews. Data were also generated from lesson observation and the analysis of documents such as the geography NCS, work schedules and lesson plans. The use of different research instruments ensured the triangulation of data sources in order to address issues of validity and reliability. The qualitative data were then analysed through thematic analysis. The study found that the sustainable development theme is central to the curriculum. Additionally, strategies of implementing EE and ESD such as the enquiry approach, the issues-based approach and the need to impart critical thinking skills are suggested in the curriculum. The teacher participants experience conceptual barriers concerning the nature of EE and ESD and that of notion of integrated geography promoted by the curriculum document. As a result, some of the teacher participants have difficulties in identifying EE and ESD themes in the curriculum document and incorporating them in the lessons. Furthermore, the teacher participants have difficulties in distinguishing learner activities from learnercentred approaches underpinned by constructivist learning theories as observed by Janse van Rensburg & Lotz-Sisitka (2000) and in using the enquiry learning approach. Some teacher participants prefer using traditional teacher-centred approaches which enable them to finish syllabuses in time for examinations. The use of learner-centred approaches such as fieldwork is hindered by barriers such as shortage of resources, class time, large classes, deteriorating discipline, heavy workload and policy contradiction. This study revealed a gap between policy rhetoric and practice in the teacher participants’ efforts to implement EE and ESD through the geography NCS. / AFRIKAANSE OPSOMMING: Beter omgewingsopvoeding-onderrig en -leer van volhoubare ontwikkeling (OO/OVO) in skole is een van die hoofresponse op die toenemende agteruitgang in die toestand van die wêreldomgewing in die Dekade van Opvoeding vir Volhoubare Ontwikkeling (DOVO) (2004-2015). OO/OVO is geïntegreer in die Suid-Afrikaanse skoolkurrikulum; in die Algemene Onderwys en Opleidingfase (Grade R tot 9) (AOO) en die Verdere Onderwys en Opleidingsfase (VOO) deur die beginsels wat die leerplan onderlê soos sosiale geregtigheid, ‘n gesonde omgewing, menseregte en inklusiwiteit. Alhoewel ‘n kruiskurrikulêre benadering tot onderrig en leer in die AOO-fase gevolg word, word OO/OVO by elke vak op die VOO-vlak geïntegreer. Omdat geografie oor mens-omgewingverhoudings handel en interdissiplinêr is, word die vak as een van die hoofvoertuie vir die onderwys van OO/OVO beskou. Om op die behoefte vir beter onderrig en leer van OO/OVO tydens die DOVO te reageer, is die hoofdoel van hierdie navorsingsprojek om vas te stel hoe OO/OVO deur die geografiekurrikulum in Suid-Afrikaanse sekondêre skole op VOO-vlak geïmplimenteer word. Die ondersoek het antwoorde gesoek op vrae wat verband hou met: geleenthede vir die onderrig van OO/OVO in die geografie Nasionale Kurrikulumverklaring (NKV); die perspektiewe van geografie-onderwysers oor OO/OVO; die mate waartoe onderwysers die onderrig van OO/OVO in geografie-lesse inkorporeer; die pedagogiese benaderings wat geografie-onderwysers gebruik; en die hindernisse ten opsigte van die onderrig van OO/OVO in die geografie-kurrikulum. ‘n Kwalitatiewe gevallestudie-navorsingsontwerp, ondersteun deur die interpretatiewe navorsingsparadigma, is ingespan. ‘n Steekproef van 10 senior geografie-onderwysers, bestaande uit agt mans en twee vroue is by die studie betrek. Hulle is uit vyf Wes-Kaapse sekondêre skole geselekteer deur middel van doelgerigte steekproefneming op so ‘n wyse dat die monster van skole so ver moontlik die sosiaal-ekonomiese en sosiaal-kulturele kontekste van die Wes-Kaap weerspieël. Inligting is verkry uit biografiese vraelyste en semi-gestruktureerde onderhoude, asook deur waarneming van lesse en deur die ontleding van dokumente soos die NKV vir geografie, werkskedules en lesplanne. Die van verskillende navorsingsinstrumente is gebruik ter ondersteunin van die triangulasie van data ten einde geldigheids- en betroubaarheidskwessies aan te spreek. Die kwalitatiewe data is daarna aan tematiese ontleding onderwerp. Die studie bevind dat volhoubare ontwikkeling ‘n sentrale tema in die kurrikulum is. Daarbenewens word strategieë om OO/OVO te implementeer, soos die ondersoekleerbenadering, die kwessiegebaseerde benadering en die behoefte om kritiese denkvaardighede te ontwikkel, in die kurrikulum voorgestel. Die onderwyserdeelnemers ervaar konseptuele hindernisse met betrekking tot die aard van OO/OVO en die nosie van geïntegreerde geografie wat die kurrikulumdokument bevorder. Gevolglik vind sommige onderwyserdeelnemers dit moeilik om OO/OVO in die leerplandokument te identifiseer en in hul lesse te inkorporeer. Verder ondervind die onderwyserdeelnemers probleme om leerderaktiwiteite te onderskei van die leerdergesentreerde benaderings wat onderlê word deur konstruktiwistiese leerteorieë soos deur Janse van Rensburg & Lotz-Sisitka (2000) waargeneem en om die ondersoekleerbenadering te gebruik. Sommige onderwyserdeelnemers verkies om tradisionele onderwysergesentreerde benaderings wat hulle in staat stel om kurrikula betyds vir eksamens af te handel. Die gebruik van leerdergesentreerde benaderings soos veldwerk word gestrem deur belemmeringe soos hulpbrontekorte, beperkte klastyd, groot klassse, verswakkende dissipline, hoë werklading en teenstrydighede in die beleid. Die studie het ‘n gaping tussen beleidsretoriek en die praktyk in die onderwyserdeelnemers se pogings om OO/OVO te implementeer wat in die geografie NKV ingewerk is, uitgewys.

NASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching performance, development and manufacturing costs, and total mass of power electronics systems. Availability of a hardened fast-switching power MOSFET will allow space-borne power electronics to approach the current level of terrestrial technology, thereby facilitating the use of more modern digital electronic systems in space. It is believed that the use of a p+/p-epi starting material for the LDMOS will offer better hardness against single-event burnout (SEB) and single-event gate rupture (SEGR) when compared to vertical devices fabricated on an n+/n-epi material. By placing a source contact on the bottom-side of the p+ substrate, much of the hole current generated by a heavy ion strike will flow away from the dielectric gate, thereby reducing electrical stress on the gate and decreasing the likelihood of SEGR. Similarly, the device is hardened against SEB by the redirection of hole current away from the base of the device's parasitic bipolar transistor. Total dose hardness is achieved by the use of a standard complementary metal-oxide semiconductor (CMOS) process that has shown proven hardness against total dose radiation effects.

Ce travail de recherche a été principalement motivé par les avantages importants apportés par la technologie UTBB FDSOI aux applications analogiques et RF de faible puissance. L'objectif principal est d'étudier le comportement dynamique du transistor MOSFET du type UTBB FDSOI et de proposer des modèles prédictifs et des recommandations pour la conception de circuits intégrés RF, en mettant un accent particulier sur le régime d'inversion modérée. Après une brève analyse des progrès réalisés au niveau des architectures du transistor MOSFET, un état de l’art de la modélisation du transistor MOSFET UTBB FDSOI est établi. Les principaux effets physiques impliqués dans le transistor à double grille avec une épaisseur du film de 7 nm sont passés en revue, en particulier l’impact de la grille arrière, à l’aide de mesures et de simulations TCAD. La caractéristique gm/ID en basse fréquence et la caractéristique ym/ID proposée pour la haute fréquence sont étudiées et utilisées dans une conception analogique efficace. Enfin, le modèle NQS haute fréquence proposé reproduit les mesures dans toutes les conditions de polarisation y compris l’inversion modérée jusqu’à 110 GHz. / This research work has been motivated primarily by the significant advantages brought about by the UTBB FDSOI technology to the Low power Analog and RF applications. The main goal is to study the dynamic behavior of the UTBB FDSOI MOSFET in light of the recent technology advances and to propose predictive models and useful recommendations for RF IC design with particular emphasis on Moderate Inversion regime. After a brief review of progress in MOSFET architectures introduced in the semiconductor industry, a state-of-the-art UTBB FDSOI MOSFET modeling status is compiled. The main physical effects involved in the double gate transistor with a 7 nm thick film are reviewed, particularly the back gate impact, using measurements and TCAD. For better insight into the Weak Inversion and Moderate Inversion operations, both the low frequency gm/ID FoM and the proposed high frequency ym/ID FoM are studied and also used in an efficient first-cut analog design. Finally, a high frequency NQS model is developed and compared to DC and S-parameters measurements. The results show excellent agreement across all modes of operation including very low bias conditions and up to 110 GHz.

The objective of this work is to provide a comprehensive analysis of the small-signal and broadband noise performance of highly scaled silicon-based field-effect transistors (FETs), and develop high-frequency noise models for robust radio frequency (RF) circuit design. An analytical RF noise model is developed and implemented for scaled Si-CMOS devices, using a direct extraction procedure based on the linear two-port noise theory. This research also focuses on investigating the applicability of modern CMOS technologies for extreme environment electronics. A thorough analysis of the DC, small-signal AC, and broadband noise performance of 0.18 um and 130 nm Si-CMOS devices operating at cryogenic temperatures is presented. The room temperature RF noise model is extended to model the high-frequency noise performance of scaled MOSFETs at temperatures down to 77 K and 10 K. Significant performance enhancement at cryogenic temperatures is demonstrated, indicating the suitability of scaled CMOS technologies for low temperature electronics. The hot-carrier reliability of MOSFETs at cryogenic temperatures is investigated and the worst-case gate voltage stress condition is determined. The degradation due to hot-carrier-induced interface-state creation is identified as the dominant degradation mechanism at room temperature down to 77 K. The effect of high-energy proton radiation on the DC, AC, and RF noise performance of 130 nm CMOS devices is studied. The performance degradation is investigated up to an equivalent total dose of 1 Mrad, which represents the worst case condition for many earth-orbiting and planetary missions. The geometric scaling of MOSFETs has been augmented by the introduction of novel FET designs, such as the Si/SiGe MODFETs. A comprehensive characterization and modeling of the small-signal and high-frequency noise performance of highly scaled Si/SiGe n-MODFETs is presented. The effect of gate shot noise is incorporated in the broadband noise model. SiGe MODFETs offer the potential for high-speed and low-voltage operation at high frequencies and hence are attractive devices for future RF and mixed-signal applications. This work advances the state-of-the-art in the understanding and analysis of the RF performance of highly scaled Si-CMOS devices as well as emerging technologies, such as Si/SiGe MODFETs. The key contribution of this dissertation is to provide a robust framework for the systematic characterization, analysis and modeling of the small-signal and RF noise performance of scaled Si-MOSFETs and Si/SiGe MODFETs both for mainstream and extreme-environment applications.

Im ESF geförderten Projekt E-PISA sind verschiedene, hoch innovative, von der globalen Forschungslandschaft ausgezeichnete und gleichzeitig industrierelevante technische Entwicklungen im Bereich der Mikrosystemtechnik, Medizintechnik und Industrie 4.0 vorangetrieben worden. Fokus der technischen Entwicklung waren zum einen Grundlagenforschung und zum anderen Applikationen von Mikrosystemen auf Basis piezoelektrischer Dünnschichten mit Aluminiumnitrid und Elektronik mit Carbon-Nano-Tubes.:Liebe LeserInnen, 5 E-PISA Team 6 Innovative Applikationen 11 Innovative Technologien 13 Regionaler Bezug 15 Wissenstransfer in Zahlen 17 Piezoelektrisches Dünnschicht-Aluminiumnitrid für Mikrosysteme 19 Mikro-opto-elektro-mechanische Systeme 23 Acoustic Emission Sensoren 29 Drucksensoren für medizinische Katheter 33 Kristallwachstum 37 Innovationssysteme, Märkte und Forschungsnetzwerke 45 Zuverlässigkeit piezoelektrischer Schichtsysteme der Mikrotechnologie 51 Veröffentlichungen und Auszeichnungen 53 Zukunftsfähigkeit 61 Danksagung 63