Growth and Characterization of Silicon Carbide Thin Films Using a Nontraditional Hollow Cathode Sputtering Technique

Silicon carbide (SiC) is considered a suitable candidate for high-power, high-frequency devices due to its wide bandgap, high breakdown field, and high electron mobility. It also has the unique ability to synthesize graphene on its surface by subliming Si during an annealing stage. The deposition of SiC is most often carried out using chemical vapor deposition (CVD) techniques, but little research has been explored with respect to the sputtering of SiC. Investigations of the thin film depositions of SiC from pulse sputtering a hollow cathode SiC target are presented. Although there are many different polytypes of SiC, techniques are discussed that were used to identify the film polytype on both 4H-SiC substrates and Si substrates. Results are presented about the ability to incorporate Ge into the growing SiC films for the purpose of creating a possible heterojunction device with pure SiC. Efforts to synthesize graphene on these films are introduced and reasons for the inability to create it are discussed. Analysis mainly includes crystallographic and morphological studies about the deposited films and their quality using x-ray diffraction (XRD), reflection high energy electron diffraction (RHEED), transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), Auger electron spectroscopy (AES) and Raman spectroscopy. Optical and electrical properties are also discussed via ellipsometric modeling and resistivity measurements. The general interpretation of these analytical experiments indicates that the films are not single crystal. However, the majority of the films, which proved to be the 3C-SiC polytype, were grown in a highly ordered and highly textured manner on both (111) and (110) Si substrates.

ESSAYS ON INTERNATIONAL RESEARCH AND DEVELOPMENT SPILLOVERS

The dissertation consists of three essays on international research and development spillovers. In the first essay, I investigate the degree to which differences in institutional arrangements among Sub-Saharan African countries determine the extent of benefits they derive from foreign research and development spillovers. In particular, I compare the international research and development spillovers for English common law and French civil law Sub-Saharan African countries. I show that differences in the legal origin of the company law or commercial codes in these countries may reflect the extent of barriers they place in the paths of firms that engage in the investment process. To tests this hypothesis, I constructed foreign R&D spillovers variable using imports as weights and employed the endogenous growth framework to estimate elasticities of productivity with respect to foreign R&D spillovers for a sample of 17 English common law and French Civil law Sub-Saharan African countries over the period 1980-2004. My results find support for the hypothesis. In particular, foreign R&D spillovers were higher in the English common law countries than in the French civil law countries. In the second essay, I examine the question of whether technical cooperation grants and overseas development assistance grants induce R&D knowledge spillovers in Sub-Saharan African countries. I test this hypothesis using data for 11 Sub-Saharan African countries over the period 1980-2004. I constructed foreign R&D spillovers using the technical cooperation grants and overseas development assistance grants as weights and employed the endogenous growth framework to provide quantitative estimates of foreign R&D spillover effects in 11 Sub-Saharan African countries. I find that technical cooperation grants and overseas development assistance grants are major mechanisms through which returns to R&D investments in G7 countries flows to Sub-Saharan African countries. However, their influence has declined over the years. Finally, the third essay tests the hypothesis that the relationship between a country's exporters and their foreign purchasing agents may lead to the exchange of ideas and thereby improve the manufacturing process and productivity in the exporting country. I test this hypothesis using disaggregated export data from OECD countries. The foreign R&D capital stock in this essay was constructed as exports weighted average of domestic R&D capital stock. I find empirical support for the hypothesis. In particular, capital goods exports generate more learning effects and therefore best explain productivity in OECD countries than non-capital goods exports.