Thesis (Ph. D.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (DR. ENG.)--John Hopkins University, 1938. / Cover title. Mimeographed. Bibliography: leaves 71-72.

Thesis (Professional Degree)--University of Missouri, School of Mines and Metallurgy, 1935. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed July 15, 2010) Includes index (p. 23-24).

Thesis (DR. ENG.)--John Hopkins university, 1938. / Cover-title. Mimeographed. "References": leaves 71-72.

Non conventional gate insulators for MOS devices are generally dielectrics that depart considerably from the classic Si0₂ used extensively in this technology. The work presented here reflects the research and development of an existing compound, Ta₂0₅, and its application as a gate insulator for both MOS capacitors and transistors. The oxide is grown both thermally and anodically from pure sputtered tantalum metal over silicon wafers. Succesful dielectrics suitable for gate insulators were obtained using both methods. High relative permittivity (≃26-28) being characteristic of tantalum pentoxide, offers considerable advantage over classic silicon dioxide gate insulators, however higher leakage currents (100 to 1000 times greater) were encountered in MOS Capacitor samples at room temperature. A method for processing the tantalum metal was developed using the liftoff technique, and it was successfully applied to both MOS capacitors and field effect transistors. Furthermore, devices were fabricated in the form of MOS Transistors, which exhibited good Id vs. Vds characteristics, with Vgs as a parameter. Gate leakage currents were low, as a double dielectric Ta₂0₅ over Si0₂ structure was used as gate insulator. A small signal model of this class of devices is presented, that takes into account the non zero gate leakage current. Another successful technique, interfacial oxidation of Ta₂0₅ over Si, was used in fabricating MOS Capacitors that yielded also low leakage currents and high specific capacitances. The purpose of this Thesis is to report the development at the University of British Columbia of the double gate insulator MOSFET technology based on the Tantalum Pentoxide-Silicon Dioxide (Ta₂0₅/Si0₂) heteromorphic structure. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The main objective of this research project was to develop a methodology which can be used to assist in developing an insulator pollution severity application map (INSMAP), more particularly for South Africa. The techniques must be able to assist in determining pollution severity levels. At the inception of this project a phase one insulator pollution severity application map was available; this map was based on an existing corrosion map, climatic maps and dust gauge measurements. The phase one map was conservative and did not highlight localised pollution. To confirm and possibly improve on this map, a phase two map was developed, which was based on feedback from Eskom field personnel via an electronic insulator pollution questionnaire survey (based on IEC 60815 guidelines).Jhe questionnaire was incorrectly completed in most cases due to a lack of understanding by field personnel of environmental pollution and the impact on insulator performance. This resulted in an unrealistic map with exaggerated contamination levels. To confirm the findings of the phase one map, a phase three approach was followed, which was focused on an investigation into pollution measurement techniques and methodologies. Based on the phase one map, a need was identified to confirm by measurements the impact of distance-to-coast. Also, the validity of installing a dust gauge at 3 metres above ground level, while insulators are at a height of 8 to 40 meters, had to be investigated. Two pollution monitoring programmes were established: a distance-to-coast and height-above-ground environmental pollution study. Various test methods are described with a complete testing procedure, descriptive equations and related pollution severity classifications for insulator pollution (DDG and ESDD) and corrosion (CLIMAT and metal specimens). The distance-to-coast test results confirm the phase one map, while the height-aboveground measurements justify the installation of dust gauges at 3 metres above ground level. Good correlations were found for the distance-to-coast study between insulator pollution severity and corrosion rates. From the height-above-ground study, a slight (insignificant) decrease in pollution levels was found for increase in height for insulator pollution and corrosion tests. Recommendations are made on setting up a basic pollution monitoring station. Key words: Insulator pollution, Corrosion, Distance, Height. / AFRIKAANSE OPSOMMING: Die hoofoogmerk van hierdie navorsingprojek was die ontwikkeling van 'n metodiek om 'n isolator besoedelingskaart saam te stel, meer spesifiek vir Suid Afrika. Die tegnieke moet die besoedelingsvlakke en impak-afstand van elke besoedelingvlak aandui. 'n Fase een isolator besoedelingskaart het reeds bestaan by die aanvang van hierdie projek, hierdie kaart was gebaseer op 'n bestaande korrosiekaart. Die fase een kaart was baie konserwatief en het nie lokale besoedeling aangedui nie. Dit was besluit om die fase een kaart te verbeter en 'n fase twee kaart was ontwikkel wat gebaseer was op 'n elektroniese isolator-besoedeling vraelys wat deur Eskom se tegniese veldpersoneel voltooi is. Die vraelys is in baie gevalle verkeerdelik ingevul, as gevolg van 'n gebrek aan die kennis oor besoedeling en die impak daarvan op isolatorprestasie. Dit het tot 'n onrealistise kaart gelei met onakurate besoedelingsvlakke. 'n Fase drie ontwikkeling is begin, waar 'n ondersoek gekyk het na metingstegnieke en metodiek vir besoedelingsmetings. 'n Volledige toetsprosedure, beskrywende vergelykings en besoedelingklassifikasies is ontwikkel vir die isolator-besoedeling (DDG en ESDD) en korrosietoetse (CLIMAT en metaal monsters). Toetsstasie seleksiekriterea vir die geografiese plasing van 'n toetsstasie is vasgestel. Twee toetsprogamme is vasgestel: 'n afstand-van-see en 'n hoogte-bo-grondvlak besoedelingsstudie. Die afstand-van-see studie het 'n impak-afstand vir elke besoedelingsvlak vir beide isolatorbesoedeling en korrosietoetse vasgestel. 'n Goeie korrelasie is vasgestel tussen isolator-besoedeling en korrosievlakke. Vir die hoogte-bo-grondvlak studie was gevind dat daar 'n klein (weglaatbare) vermindering in besoedelingsvlakke met toename in hoogte bo grondvlak vir isolatorbesoedeling- en korrosievlakke onstaan. 'n Goeie korrelasie bestaan tussen isolatorbesoedeling- en korrosievlakke. Aanbevelings word gemaak vir die opstel van 'n basiese besoedelingsmetingstasie. Sleutelwoorde: Isolator besoedeling, Korrosie, Afstand, Hoogte.