In transgenic research the precise control of transgene expression is crucial in order to obtain transformed organisms with expected desirable traits. A broad range of transgenic plants use the constitutive cauliflower mosaic virus (CaMV) 35S promoter to drive expression of selectable marker genes. Due to its strong enhancer function, this promoter can disturb the specificity of nearby eukaryotic promoters. When inserted immediately downstream of the 35S promoter in transformation vectors, special DNA sequences called insulators can prevent the influence of the CaMV35S promoter/enhancer on adjacent tissue-specific promoters for the transgene. Insulators occur naturally in organisms such as yeasts and animals but few insulators have been found in plants. Therefore, the goal of this study is to identify DNA sequences with insulator activity in Arabidopsis thaliana. A random oligonucleotide library was designed as an initial step to obtain potential insulators capable of blocking enhancer-promoter interactions in transgenic plants. Fragments from this library with insulator activity were identified and re-cloned into pB31, in order to confirm their activity. To date, one insulator sequence (CLO I-3) has been identified as likely possessing enhancer-blocking activity. Also, two other oligonucleotide sequences (CLO II-10 and CLO III-78) may possess insulator activity but more sampling is needed to confirm their activity. Further studies are needed to validate the function of plant insulator(s) and characterize their associated proteins.

Non conventional gate insulators for MOS devices are generally dielectrics that depart considerably from the classic Si0₂ used extensively in this technology. The work presented here reflects the research and development of an existing compound, Ta₂0₅, and its application as a gate insulator for both MOS capacitors and transistors. The oxide is grown both thermally and anodically from pure sputtered tantalum metal over silicon wafers. Succesful dielectrics suitable for gate insulators were obtained using both methods. High relative permittivity (≃26-28) being characteristic of tantalum pentoxide, offers considerable advantage over classic silicon dioxide gate insulators, however higher leakage currents (100 to 1000 times greater) were encountered in MOS Capacitor samples at room temperature. A method for processing the tantalum metal was developed using the liftoff technique, and it was successfully applied to both MOS capacitors and field effect transistors. Furthermore, devices were fabricated in the form of MOS Transistors, which exhibited good Id vs. Vds characteristics, with Vgs as a parameter. Gate leakage currents were low, as a double dielectric Ta₂0₅ over Si0₂ structure was used as gate insulator. A small signal model of this class of devices is presented, that takes into account the non zero gate leakage current. Another successful technique, interfacial oxidation of Ta₂0₅ over Si, was used in fabricating MOS Capacitors that yielded also low leakage currents and high specific capacitances. The purpose of this Thesis is to report the development at the University of British Columbia of the double gate insulator MOSFET technology based on the Tantalum Pentoxide-Silicon Dioxide (Ta₂0₅/Si0₂) heteromorphic structure. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The widespread use of electronics in more avenues of consumer use is increasing. Applications range from medical instrumentation that directly can affect someone's life, down hole sensors for oil and gas, aerospace, aeronautics, and automotive electronics. The increased power density and harsh environment makes the reliability of the packaging a vital part of the reliability of the device. The increased importance of analog devices in these applications, their high voltage and high temperature resilience is resulting in challenges that have not been dealt with before. In particular packaging where insulative properties are vital use polymer resins modified by ceramic fillers. The distinct dielectric properties of the resin and the filler result in charge storage and release of the polarization currents in the composite that have had unpredictable consequences on reliability. The objective of this effort is therefore to investigate a technique that can be used to measure the polarization in filled polymer resins and evaluate reliable molding compounds. A valuable approach to measure polarization in polymers where charge release is tied to the glass transition in the polymer is referred to as thermally stimulated depolarization current (TSDC) technique. In this dissertation a new TSDC measurement system was designed and fabricated. The instrument is an assembly of several components that are automated via a LabVIEW program that gives the user flexibility to test different dielectric compounds at high temperatures and high voltage. The temperature control is enabled through the use of dry air convection heating at a very slow rate enabling controlled heating and cooling. Charge trapping and de-trapping processes were investigated in order to obtain information on insulating polymeric composites and how to optimize it. A number of material properties were investigated. First, polarization due to charges on the filer were investigated using composites containing charged and uncharged particles using quartz and ion exchange montmorillonite silicates in an epoxy matrix. The thermally-activated charge release shows a difference in the composite characteristics and preparation. This difference indicates that the trap levels depend on the de-trapping process and on the chemical nature of the trap site. Using a numerical approach to the release spectra, a model was developed to examine through short time testing, important parameters such as glass transition temperature, residual polarization, depolarization peak, window polarization modeling and activation energy of relaxations. Second the design of mold compounds that could combine manufacturing (temperature of molding), geometric (thickness of packaging material), composition (amount and size of filler) effects was developed using a novel design of experiments approach. The statistical DOE enabled the determination of which causes should be considered when designing a mold compound that has minimal polarization both as singular variables as well as combined variables. Finally, the DOE approach was used to develop a high temperature reliable molding compound through use of combined fillers of thermally conductive and nonconductive fillers having different shapes. Through the systematic approach to developing a technique and designing a mold compound addressing the multiple impacts on reliability of packaging, the dissertation provides an approach to the design, selection, performance and durability of molding compounds.

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The generation of electron-hole pairs in materials has great importance. In direct bandgap semiconductor materials, the mechanism of radiative recombination of electron-hole pairs leads to the emission of photons, which is the basis of Light Emitting Diodes (LEDs). The excitation of electron-hole pairs by absorption of photons is the active process in photodiodes, solar cells, and other semiconductor photodetector devices. In optoelectronic devices such as optical switches which are based on transmission and reflection of the photons, electron-hole pairs excitation is a key for the device performance. Diodes and transistors are also great discoveries in electronics which rely on the generation and recombination of electron-hole pairs at p-n junctions. In three-dimensional topological insulators (3D TIs) materials nanostructures excitation of electron-hole pairs can be utilized for the quantum memory, quantum information and quantum teleportation. In two-dimensional (2D) layered materials like graphene, MoS2, MoSe2, WS2 and WSe2 generation and recombination of electron hole pairs is main process at p-n junctions, infrared detectors and sensors. This PhD thesis is concerned with the physics of different types of electron-hole pairs in various materials, such as wide-bandgap semiconductors, 3D topological insulators, and plasmonic excitations in metallic nanostructures. The materials of interest are wide bandgap semiconductors such as TiO2 , 3D TIs such as Pb1-xSnxTe and the 2D layered materials such as MoS2 and MoO3. We study the electronic and optical properties in bulk and nanostructures and find applications in the area of semiclassical and quantum information processing. One of the interesting applications we focus in this thesis is shift in surface plasmon resonance due to reduction in index of refraction of surrounding dielectric environment which in turns shifts the wavelength of surface plasmon resonance up to 125 nm for carrier density of 10^22/cm^3. Employing this effect, we present a model of a light controlled plasmon switching using a hybrid metal-dielectric heterostructures. In 3D TIs nanostructures, the time reversible spin partners in the valence and conduction band can be coupled by a left and a right handed circular polarization of the light. Such coupling of light with electron-hole pair polarization provides an unique opportunity to utilize 3D TIs in quantum information processing and spintronics devices. We present a model of a 3D TI quantum dot made of spherical core-bulk heterostructure. When a 3D TI QD is embedded inside a cavity, the single-photon Faraday rotation provides the possibility to implement optically mediated quantum teleportation and quantum information processing with 3D TI QDs, where the qubit is defined by either an electron-hole pair, a single electron spin, or a single hole spin in a 3D TI QD. Due to excellent transport properties in single and multiple layers of 2D layered materials, several efforts have demonstrated the possibility to engineer electronic and optoelectronic devices based on MoS2. In this thesis, we focus on theoretical and experimental study of electrical property and photoluminescence tuning, both in a single-layer of MoS2.We present theoretical analysis of experimental results from the point of view of stability of MoO3 defects in MoS2 single layer and bandstructures calculation. In experiment, the electrical property of a single layer of MoS2 can be tuned from semiconducting to insulating regime via controlled exposure to oxygen plasma. The quenching of photoluminescence of a single sheet of MoS2 has also been observed upon exposure to oxygen plasmas. We calculate the direct to indirect band gap transitions by going from MoS2 single sheet to MoO3 single sheet during the plasma exposure, which is due to the formation of MoO3 rich defect domains inside a MoS2 sheet.

Metal - metal and to an extent metal - insulator contact or triboelectric charging are well known phenomena with good theoretical understanding of the charge exchange mechanism. However, insulator – insulator charging is not as well understood. Theoretical and experimental research has been performed that shows that the surface charge on an insulator after triboelectric charging with another insulator is rapidly dissipated with lowered atmospheric pressure. This pressure discharge is consistent with surface ions being evaporated off the surface once their vapor pressure falls below the saturation vapor pressure. A two-phase equilibrium model based on an ideal gas of singly charged ions in equilibrium with a submonolayer adsorbed film was developed to describe the pressure dependence of the surface charge on an insulator. The resulting charge density equation is an electrostatic version of the Langmuir isotherm for adsorbed surface particles, which describes well the experimental observations.

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