Thesis (Ph.D.)--Drexel University, 2009. / Includes abstract and vita. Includes bibliographical references (leaves 110-122).

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 164-173). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 212-225). Available also in a digital version from Dissertation Abstracts.

In general, La-based high-k gate dielectric owns superior properties to offer transistor excellent characteristics. Thus, amorphous InGaZnO thin-film transistor with La-based high-k gate dielectric has been investigated in this thesis. Different approaches have been adopted to improve the device performance. First of all, the influence of gate-dielectric annealing in oxygen for different times on the device characteristics of the amorphous InGaZnO thin-film transistor with HfLaO gate dielectric has been investigated. It is demonstrated that this annealing treatment can effectively suppress the negative oxide charges. Moreover, it is discovered that this annealing treatment can suppress the acceptor-like border and interface traps. Accordingly, a high saturation carrier mobility of 35.2 〖cm〗^2/V∙s is achieved for the 30’-annealed device. Then, the effects of dielectric-annealing gas (O2, N2 and NH3) for a fixed annealing time of 10 min on the device characteristics are studied, and improvements by the dielectric annealing are observed for each gas. Among the samples, the N2-annealed sample has a high saturation carrier mobility of 35.1 〖cm〗^2/V∙s, the lowest subthreshold swing of 0.206 V/dec and a negligible hysteresis. On the contrary, the O2-annealed sample shows poorer performance due to a decrease of electron concentration in InGaZnO. Furthermore, the NH3-annealed sample displays the lowest threshold voltage (1.95 V) due to increased gate-oxide capacitance and generated positive oxide charges. Next, the effects of fluorine incorporation in amorphous InGaZnO by ion implant on the characteristics of InGaZnO thin-film transistor have been investigated. The electrical characteristics can be improved by this treatment due to increase of carrier concentration and passivation of defects in the InGaZnO film. Consequently, the saturation carrier mobility can be increased to 34.0 〖cm〗^2/V∙s, and the output current can be nearly doubled. However, device degradation is observed for very high fluorine dose above 1.0×1015 /〖cm〗^2. Then, another method for fluorine incorporation has been studied by treating the amorphous InGaZnO film in a CHF3/O2 plasma. The saturation carrier mobility can be improved to as high as 39.8 〖cm〗^2/V∙s. Then, a new high-k material is proposed by investigating the effects of Ta incorporation in the La2O3 gate dielectric of amorphous InGaZnO thin-film transistor. Since the Ta incorporation is found to effectively enhance the moisture resistance of the La2O3 film, both the dielectric roughness and trap density at/near the InGaZnO/dielectric interface can be reduced, resulting in a significant improvement in the electrical characteristics of the device. Nevertheless, excessive incorporation of Ta can degrade the device characteristics due to newly-generated Ta-related traps. Finally, the proposed TaLaO is compared with Ta2O5 as the gate dielectric of amorphous InGaZnO thin-film transistor. It is found that the electrical characteristics of the device can be effectively improved by the incorporation of La in the Ta2O5 gate dielectric, which is ascribed to the fact that La incorporation can enlarge the band gap of Ta oxide and its conduction-band offset with InGaZnO, and also reduce the trap densities in the Ta2O5 gate dielectric and at the InGaZnO/gate-dielectric interface. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

No description available.

Nonlinear optical phenomena associated with high-order soliton breakup in photonic crystal fibres and squeezed state generation in three dimensional photonic crystal microcavities are investigated. In both cases, the properties of periodically patterned, high-index contrast dielectric structures are engineered to control the dispersion and local field enhancements of the electromagnetic field. Ultra-short pulse propagation in a polarization-maintaining microstructured fibre (with 1 um core diameter and 1.1 m length) is investigated experimentally and theoretically. For an 80 MHz train of 130 fs pulses with average propagating powers in the fibre up to 13.8 mW, the output spectra consist of multiple discrete solitons that shift continuously to lower energies as they propagate in the lowest transverse mode of the fibre. The number of solitons and the amount that they shift both increase with the launched power. All of the data is quantitatively consistent with solutions of the nonlinear Schrodinger equation, but only when the Raman nonlinearity is treated without approximation, and self-steepening is included. The feasibility of using a parametric down-conversion process to generate squeezed electromagnetic states in 3D photonic crystal microcavity structures is investigated for the first time. The spectrum of the squeezed light is theoretically calculated by using an open cavity quantum mechanical formalism. The cavity communicates with two main channels, which model vertical radiation losses and coupling into a single-mode waveguide respectively. The amount of squeezing is determined by the correlation functions relating the field quadratures of light coupled into the waveguide. All of the relevant model parameters are realistically estimated using 3D finite-difference time-domain (FDTD) simulations. Squeezing up to ~20% below the shot noise level is predicted for reasonable optical excitation levels. To preserve the squeezed nature of the light generated in the microcavity, a unidirectional coupling geometry from the microcavity to a ridge waveguide in a slab photonic crystal structure is studied. The structure was successfully fabricated in a silicon membrane, and experimental measurements of the efficiency for the signal coupled out of the structure are in good agreement with the result of FDTD simulations. The coupling efficiency of the cavity mode to the output channel is ~60%.

No description available.

No description available.

No description available.

The strength development of young masonry mortar and prism is studied through measuring the electrical properties of hydrating mortar by using TWIN-tape capacitance sensor. The dielectric properties over the frequency range of 10 kHz to10 MHz varies during hydration of mortar, providing a means for monitoring the strength development. This investigation confirms that the lower frequencies (less than 100 kHz) are very efficient in monitoring hydration of mortar. In addition, wireless sensing electronics is employed to monitor the strength gain process of young masonry prisms. Moreover, the freezing and thawing temperatures of masonry mortar and prism are identified by using three different techniques. Furthermore, the strength gain process of mortar is investigated at cold ambient temperatures, i.e. ambient temperature below 5ºC, by using dielectric measurements. This investigation reveals that the mortar gains strength at temperatures as low as 0ºC, whereas it partially freezes at -1º c and completely freezes at -2ºC.