Univ., Diplomarbeit--Dresden. / Literaturverz. S. 97 - 107.

Since its discovery in 2004, graphene has been widely touted as a potential replacement for silicon in the next generation of electronic circuits owing to its exceptionally high carrier mobilities and its ultra-thin body. Graphene field effect transistors (GFETs) show promising potential for use in analog and radio frequency (RF) applications, with theoretically predicted THz frequencies only being limited by fabrication challenges. High series resistance of the source/drain access regions in a GFET is one such major factor responsible for performance degradation. In this thesis, a simple and straightforward scheme of reducing this resistance by self-aligned spin-on-doping of graphene using surface transfer dopants is presented. Back-gated GFETs were fabricated on Si/SiO2 and doped using various surface transfer dopants. A novel method of spin-on-doping graphene using poly(ethyleneimine) (PEI) was developed. Top-gated GFETs with mobilities up to 6,900 cm2/Vs were fabricated and their access regions were spin-on-doped in a self-aligned manner offering a 3X reduction in the series resistance. GFET drive currents improved by up to 4X and transconductances up to 3X after self-aligned doping. GFETs were also fabricated on insulating quartz substrates with mobilities up to 5,600 cm2/Vs and showed performance enhancements up to 2X after self-aligned doping. / text

“Finding Heidi’s Story: The Evolution of ‘Dynamo Berlin’” examines the creative process of Margot Newcomer’s feature length script, “Dynamo Berlin.” It chronicles the thought process and revisions throughout a seven-month period. / text

The widespread use of performance-enhancing drugs among elite athletes is the most important policy problem in modern Olympic history. Although several works have addressed the subject (a few of which are admittedly excellent), they have been limited either temporally or by a lack of access to archival sources of information. Based on research in both American and foreign archives, this dissertation complements earlier, path-breaking works by tracing the evolution of Olympic doping policy from 1960 to the present. Olympic policymakers first seriously considered the subject of doping after suspicions arose that the death of Danish cyclist Knud Jensen at the 1960 Rome Olympic Games was triggered by the use of amphetamines. For most of the next decade, these officials attempted to define the doping problem and struggled to formulate a program for its solution. An international politics of doping consequently developed, under which the various bodies of the Olympic governance structure failed, due to their divergent interests and jurisdictions, to implement a coordinated plan. Until recently, administrators working at all levels of this organizational system tended to formulate doping policies with the idea of dampening the effects of public controversy. In addition, the influence of the Cold War on the Olympics exacerbated the situation, as national governments on both sides of the Iron Curtain, believing that success in the Olympic medals race was essential to their images abroad, condoned the use of ergogenic aids among elite competitors. It was not until Canadian track star Ben Johnson tested positive for an anabolic steroid after setting a new world record in the one-hundred meter sprint at the 1988 Seoul Games that a different policy direction was initiated. The involvement of national governments after the scandal led eventually to the creation of the World Anti-Doping Agency in November 1999. The consolidation of regulatory authority in this agency has transformed the issue of doping in the Olympics from a combined political and scientific problem to one based more appropriately on the latter. / text

The success of orthopaedic implants fixed in the skeletal system using bone ingrowth into porous surfaces is critically dependent on the extent and quality of the initial bone ingrowth and the subsequent long-term maintenance of the bone within the porous structure. Biologically-significant elements (Ca, Mg, Mn) were incorporated at concentrations up to 5 mol% in solid solution in yttia-stabilised tetragonal zirconia polycrystal (3YTZP), whilst controlling microstructure and phase composition, to investigate the effect of ceramic chemistry on cellular behaviour in vitro and bone ingrowth into porous structures in vivo. Cellular attachment, proliferation, and migration on the ceramics were investigated using in vitro assays using fibroblasts. Cells were able to adhere strongly and proliferate on all ceramic surfaces, exhibiting maximal proliferation and minimal migration on 3YTZP but significantly faster migration on doped-3YTZP. The TZP ceramics were therefore considered to support normal cellular processes and thus were suitable for further study in vivo. A technique based on pressure casting ceramic slurry into a polymer preform of the desire pore structure, followed by polymer burnout and then sintering, was developed for fabricating porous bioceramics containing highly-controlled three-dimensional pore geometries. The ability of a selected pore structure to support bone ingrowth was tested using hydroxyapatite by implanting samples into femoral cortical bone of adult sheep for 4 and 12 weeks. Bone was able to rapidly colonise the porous structure and remodel such that, by 12 weeks implantation time, the majority of the porosity was filled with mature lamellar bone. Porous scaffolds of pure 3YTZP and 3YTZP doped with 1 mol% Mg, 1 mol% Mn, 1 mol% Ca, or 5 mol% Ca were fabricated and tested in the sheep model. Bone ingrowth into the doped compositions was significantly greater than that into pure 3YTZP, and was similar to that into the porous hydroxyapatite, indicating that the dopants significantly promoted osteogenesis within the bioinert scaffolds. This finding has application in clinical applications in that the initial bone ingrowth and, potentially, the long-term maintenance of bone within the porous structure may be improved by the incorporation of small amounts of biologically significant elements.

The unique properties of diamond make it an excellent material for electronic and optical applications. It is particularly attractive for ultraviolet radiation dosimetry due to its intrinsic properties, which include biological tissue equivalence and visible blindness. Importantly, the advent of synthetic diamond, especially Chemical Vapour Deposition (CVD) diamond, has made it more economically viable for such applications. A thorough understanding of the electronic properties of diamond is needed before these applications can be fully explored. Consequently, this thesis investigates charge carrier trapping states in CVD polycrystalline diamond for the optimization of ultraviolet radiation dosimetry. / The technique of Thermally Stimulated Conductivity (TSC) is used to probe electrically active defects and is also applied for dosimetric read-out. A range of as-grown CVD polycrystalline diamond films are studied to determine attributes that favour dosimetric-related TSC. In doing so, we establish that dosimetric TSC in these films originate from defects at the grain boundaries with a correlation to high crystalline quality. / With this finding in hand, we then investigate the possibility of optimising diamond for dosimetry by controllably introducing extrinsic dosimetric defects using ion implantation. However, it is shown that these defects are not suitable for dosimetry and have a detrimental effect on the indigenous TSC signal. This study verifies the importance of crystalline quality on the indigenous dosimetric properties of CVD polycrystalline diamond. / The possibility of doping CVD diamond during growth is also investigated as a means for intentionally introducing extrinsic dosimetric defects. Sulphur is selected as the dopant based on the theoretical energy levels formed by this defect, and because the prospect of S doping in diamond remains an actively debated issue in the literature. We report for the first time defect levels extracted from TSC analysis of S-doped CVD diamond and find consistency with theoretical predications. In addition, the dominant TSC trap level in S-doped diamond shows promise for radiation dosimetry with certain properties exceeding many current radiation dosimeters. / The experimental results in this thesis lead to a deeper understanding of defect and trapping mechanisms in CVD polycrystalline diamond and establish attributes that favour TSC and related dosimetric properties in such films. This knowledge is fundamental to the realisation of diamond for ultraviolet dosimetry.

Thesis (doctoral)--Erasmus Universiteit Rotterdam, 2006. / Includes bibliographical references (leaves 356-367). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

Thesis (doctoral)--Erasmus Universiteit Rotterdam, 2006. / Includes bibliographical references (leaves 356-367).

Thesis (Ph. D.)--Louisiana State University, Baton Rouge, 2008. / Title from document title page.

Freie Universität Berlin, Diss., 2009.