Browsing by Author "Dr. Douglas Barlage, Committee Member"

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Growth and Characterization of Epitaxial ZnO Thin Films on GaN(0001) Epilayers and ZnO{0001} Substrates Using Metalorganic Chemical Vapor Depositon
(2005-06-29) Pierce, Jonathan Mark; Dr. Douglas Barlage, Committee Member; Dr. George Rozgonyi, Committee Member; Dr. Robert Davis, Committee Chair
ZnO thin films were produced on GaN(0001) epilayers and ZnO(0001) substrates utilizing an iterative process requiring a structured low temperature (480°C) layer followed by a high temperature (800°C) densification step to create approximately 200 nm of contiguous film. This process is subsequently repeated to achieve thicker films with each iteration producing approximately 200 nm of dense film. Diethylzinc was used as the zinc source, UHP oxygen (O2) as the oxygen source, and UHP argon as both the carrier and diluent gas. Nitrous (N2O) and nitric oxide (NO2) were also used both as potential oxygen sources in the pure state as well as mixed with oxygen in the chamber and for nitrogen doping of the growing film. Major impurities of C, H, and N were incorporated into the films with the majority of the incorporation occurring during the low temperature step. Films grown using N2O + O2 contained an average of 5 x 1017 cm-3 atomic nitrogen while films using NO2 + O2 had an average nitrogen concentrations of 9 x 1019 cm-3. Needle microstructures were observed for low temperature layers using O2 and N2O + O2, while networked structures formed when using NO2 + O2. The surface of the densified films contained hexagonal pits that increased in number and depth with an increase in film thickness. Triple-axis XRD measurements indicated that the crystal structure of the films mimic the underlying substrates. A comparative analysis of undoped and N-doped films using capacitance voltage and photoluminescence measurements showed that the N-doped films were more insulating than the undoped films and the incorporation of nitrogen decreases the amount of excitonic peaks observed in the PL spectra. The 3.367 eV ionized donor bound exciton becomes dominant in N-doped films relative to the 3.361 eV donor bound exciton that dominates the undoped films. A preliminary inductively coupled plasma etching study determined that the smoothest sidewalls and surfaces were obtained using an ICP power of 600 W, a DC bias of 50 V, 5 mtorr total pressure, and 20 sccm of pure flowing BCl3 The etch rate under these conditions was 40 nm/min.
Implementation of Microwave Measurements Using Novel Calibration Techniques
(2003-05-19) Goswami, Aditya; Dr. Michael B. Steer, Committee Chair; Dr. Douglas Barlage, Committee Member; Dr. Griff Bilbro, Committee Member
NetA (Network Analysis) tools for calibration of microwave measurements has been implemented. NetA contains calibration and de-embedding procedures as data analysis MATLAB routines. The Through Line method for calibration of two ports has been used and the NetA process flow has also been explained. Complex characteristic impedance of the micro-strip transmission line has been calculated using the ETRL (Enhanced TRL)technique. Results have been simulated using NetA tools. A LabVIEW Implementation of NetA has also been implemented so as to enhance the usability of NetA and also provide the capability of Real--time microwave calibration and de-embedding.
Modeling of RF Field effects due to MRI Fields in Patients with a Retinal Implant
(2007-11-18) Jasti, Srinivas; Dr. Gianluca Lazzi, Committee Chair; Dr. Kevin Gard, Committee Member; Dr. Douglas Barlage, Committee Member
Performance Analysis of System-on-Chip Applications of Three-dimensional Integrated Circuits
(2006-03-01) Schoenfliess, Kory Michael; Dr. W. Rhett Davis, Committee Chair; Dr. Paul Franzon, Committee Member; Dr. Douglas Barlage, Committee Member
In the research community, three-dimensional integrated circuit (3DIC) technology has garnered attention for its potential use as a solution to the scaling gap between MOSFET device characteristics and interconnects. The purpose of this work is to examine the performance advantages offered by 3DICs. A 3D microprocessor-based test case has been designed using an automated 3DIC design flow developed by the researchers of North Carolina State University. The test case is based on an open architecture that is exemplary of future complex System-on-Chip (SoC) designs. Specialized partitioning and floorplanning procedures were integrated into the design flow to realize the performance gains of vertical interconnect structures called 3D vias. For the post-design characterization of the 3DIC, temperature dependent models that describe circuit performance over temperature variations were developed. Together with a thermal model of the 3DIC, the performance scaling with temperature was used to predict the degree of degradation of the delay and power dissipation of the 3D test case. Using realistic microprocessor workloads, it was shown that the temperatures of the 3DIC thermal model are convergent upon a final value. The increase in delay and power dissipation from the thermal analysis was found to be negligibly small when compared to the performance improvements of the 3DIC. Timing analysis of the 3D design and its 2D version revealed a critical path delay reduction of nearly 26.59% when opting for a 3D implementation. In addition, the 3D design offered power dissipation savings of an average of 3% while running at a proportionately higher clock frequency.