Thesis (PH. D)--University of Nebraska. / "Bibliography": p. 16. Also issued in print.

Thesis (PH. D)--University of Nebraska. / eContent provider-neutral record in process. Description based on print version record. "Bibliography": p. 16.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007. / Dr. John Cressler, Committee Member ; Dr. John Papapolymerou, Committee Chair ; Dr. Manos Tentzeris, Committee Member.

No description available.

This research presents an analysis of low cost fabrication techniques for embedded thin film resistors suitable for large volume needs. High frequency applications are targeted from 2 to 40GHz. Two approaches are taken. The first utilizes commercially available foils to produce resistors using only thermocompression bonding and wet chemical etching. The second method utilizes electroless plating with a modified plasma treatment to promote adhesion to organic materials. This process uses only chemical baths to form the thin films. Several RF and millimeter wave applications using these processes have been explored including terminations and attenuators. Accurate simulations of resistor performance were obtained using impedance boundaries in conjunction with the finite element method. Resistors created using the foil transfer process are measured to be accurate within 5% of these simulated values. Electroless values are currently accurate to around 40%, with research underway expected to improve this to around 10%.

No description available.

No description available.

Thesis (M.S. in electrical engineering)--Washington State University, August 2006. / Includes bibliographical references (p. 64-65).

<p> Tantalum thin film resistors have been reactively sputtered in oxygen and nitrogen simultaneously. The films studied had resistivities ranging from 400μΩ-cm to 3 x 10^4 μΩ-cm. The corresponding TCR values ranged from -50 ppm/°C to -2,000 ppm/°C. Conductance-temperature measurements show that electrical conduction in discontinuous films of metallic islands (typically 100 A°) largely surrounded by regions of Ta2O5 (typically 50 A°) may be due to a tunneling mechanism of negative TCR operating concurrently with a metallic mechanism of positive TCR via interconnected metallic islands.</p> <p> Irradiation of these discontinuous films by 150 keV protons produces a conductance increase which is attributed to an enhanced tunneling mechanism via electronic defect levels in the inter-island oxide regions. During irradiation of these films at 30°K, the conductance change increases and approaches apparent saturation. This nonlinearity is attributed to a combination of spontaneous recombination and close-pair thermal annealing. The number of unstable sites surrounding each defect is found to be ≥ 4. Thermal recovery of the conductance proceeds in two main stages: Stage A (34°K to 150°K) is attributed to close-pair or correlated recombination; Stage B (150°K to 300°K) is attributed to uncorrelated migration of defects to gap-island interfaces, as is indicated by the greatly reduced Stage B annealing which is observed for continuous, polycrystalline films of Ta2O5, having a typical grain size of 1,500 A°. Negative annealing stages (characterized by a conductance increase) indicate a metallic conduction process via connected metallic islands.</p> <p> For 286°K irradiation of discontinuous films, the conductance initially increases with fluence in a nonlinear fashion until a threshold fluence is reached, at which point the conductance decreases with fluence. The nonlinearity of the conductance increase is attributed to trapping of mobile radiation-produced defects at gap-island interfaces during irradiation. The subsequent conductance decrease is attributed to a shift in the Fermi level, and thus the height of the tunneling barrier, as the result of the formation of unequal concentrations of stable radiation-produced donor and aeceptor defects since unequal concentrations of these defects can be expected to annihilate at the gap-island interface. The absence of this conductance decrease in continuous polycrystalline films is consistent with this model, since the absence of gap-island interfaces is expected to result in equal concentrations of stable donor and acceptor levels being produced.</p> <p> The observed negative increase in TCR with fluence is attributed to an increase in the proportion of the tunneling mechanism of negative TCR (as the result of radiation-produced defects in the inter-island oxide regions) relative to the proportion of the metallic conduction mechanism of positive TCR. The difference between the TCR recovery after irradiation at 30°K (little recovery between 150°K and 300°K) and the conductance recovery (about 50 percent of the recovery occurs between 150°K and 300°K) is attributed to the expected greater influence of metallic recovery on the annealing of the film TCR relative to the annealing of the film conductance.</p> / Thesis / Doctor of Philosophy (PhD)

Due to the low current ratings of the currently available silicon carbide (SiC) switches they cannot be employed in high-power converters. Thus, it is necessary to parallel-connect several switches in order to reach higher current ratings. This paper presents an investigation of parallel-connected normally-on SiC junction field effect transistors. There are four crucial parameters affecting the effectiveness of the parallel-connected switches. However, the pinch-off voltage and the reverse breakdown voltage of the gates seem to be the most important parameters which affect the switching performance of the devices. In particular, the spread in these two parameters might affect the stable off-state operation of the switches. The switching performance and the switching losses of a pair of parallel-connected devices having different reverse breakdown voltages of the gates is investigated by employing three different gate-driver configurations. It is experimentally shown that using a single gate-driver circuit the switching performance of the parallel-connected devices is almost identical, while the total switching losses are lower compared to the other two configurations. / <p>QC 20121116</p>