Because of its attractive material properties like high hardness, high toughness, and excellent high temperature strength, materials like silicon nitride are becoming more common for use in high performance applications. However, there have been limited studies of the fatigue behavior of small cracks in silicon nitride and other materials toughened by grain bridging mechanisms. This study explores using micro Raman spectroscopy, fatigue crack growth data and results from static fracture experiments to determine a bridging stress profile for silicon nitride doped with MgO and Y₂O₃ as sintering additives. These bridging stress profiles allow for the creation of a geometry specific fatigue threshold R-curve which can be used to develop a fatigue endurance strength prediction tool to aid in the design of products using the material. Cyclical fatigue experiments conducted on bend beams with induced semi-elliptical surface cracks were conducted to verify the prediction tool. The results show that no bend beams with this crack geometry failed below the predicted endurance level. It is expected that this method can be extended to create fatigue endurance strength predictions for other materials similarly toughened by grain bridging and other mechanisms. / Graduation date: 2013

In this study, SiO2-xFx films were deposited on Si and amorphous silicon, their physical and chemical properties were measured. An Al/ SiO2-xFx /Si and Al/ SiO2-xFx/a-Si/Si MOS structures were used for the electrical measurements. To improve the electrical properties, we investigated the characteristics of SiO2-xFx films after annealing in nitrogen and oxygen ambient. We can find the leakage current density can be reduced to about 1.09¡Ñ 10-6 A/cm2 and 1.03¡Ñ 10-7 at -1 MV/cm and at 1 MV/cm after annealing in oxygen ambient. Although the leakage current is improved one order but the dielectric constant is increase.

No description available.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

by Poon Ming-Cheong. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves [163-175]

Silicon and silicon nitride thin films were growth on Si and glass substrates at room temperature by ratio-frequency (r-f) magnetron sputtering. The electrical characteristics of the silicon nitride films were characterized using I-V and C-V measurement under different growth condition, including r-f power, nitrogen partial pressure, and hydrogen partial pressure. Minimum current leakages for MIS structure as low as 2¡Ñ10 A/cm were obtained at 1 MV/cm electrical field with hysteresis voltage about 2V. The root-mean square surface roughness of the silicon nitride film is less then 1nm. In addition, silicon nitride capacitors with indium-tin-oxide as electrodes were fabricated. Silicon thin films prepared by R.F. magnetron sputtering at room temperature are amorphous. The measurements on the variation of the photo-conductivity were used to characterize the characteristics of the Si film.

Thesis (M.S.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Jan. 21, 2010). Includes bibliographical references (p. 57-58) .

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

Not available / text

published_or_final_version / Physics / Master / Master of Philosophy