In this work, we have developed two different fabrication processes for relaxed Si₁₋xGex-on-insulator (SGOI) substrates: (1) SGOI fabrication by etch-back approach, and (2) by "smart-cut" approach utilizing hydrogen implantation. Etch-back approach produces SGOI substrate with less defects in SiGe film, but the SiGe film uniformity is inferior. "Smart-cut" approach has better control on the SiGe film thickness and uniformity, and is applicable to wider Ge content range of the SiGe film. We have also fabricated strained-Si n-MOSFET’s on SGOI substrates, in which epitaxial regrowth was used to produce the surface strained Si layer on relaxed SGOI substrate, followed by large-area n-MOSFET’s fabrication on this structure. The measured electron mobility shows significant enhancement (1.7 times) over both the universal mobility and that of co-processed bulk-Si MOSFET’s. This SGOI process has a low thermal budget and thus is compatible with a wide range of Ge contents in Si₁₋xGex layer. / Singapore-MIT Alliance (SMA)

Chromatin insulators are short DNA sequences that, together with enhancers and silencers, orchestrate gene transcription through DNA-protein interactions in eukaryotic genomes. It has been proposed that insulators operate at the chromatin level by generating functionally independent higher-order chromatin domains. Insulators may maintain the integrity of such domains using two properties: blocking enhancer-promoter interactions and blocking heterochromatin spreading. The gypsy insulator of Drosophila was identified as a region of the gypsy retrovirus responsible for the production of tissue-specific mutations in many genes. The Suppressor of Hairy wing [Su(Hw)] protein contains 12 zinc fingers that specifically bind the gypsy insulator. Upon DNA binding, Su(Hw) recruits a second protein, Modifier of Mdg4 67.2 [Mod(mdg4) 67.2], and the interaction of both proteins is required for insulator function in vivo. We have found that three different arrays of gypsy retrovirus insertions in a yellow transgene result in unique yellow phenotypes, showing that the enhancer-blocking activity of the Drosophila gypsy insulators depends on the relative orientation of the gypsy retroviruses on the chromosome. We also observed from transgenic lines with gypsy retrovirus or insulator insertions that interaction of insulators may be regulated by active enhancers according to the relative positions of the insulators flanking the enhancers. Moreover, we show that gypsy insulators can positively modulate yellow activation and result in wild-type levels of expression when placed upstream of enhancers in yellow transgenes in which enhancers are placed out of context by &#;-DNA spacers and fail to reproduce the expression levels of yellow in wings and body cuticle. Our results provide evidence indicating that this phenomenon is independent of the boundary activity. Genetic analysis using mod(mdg4)67.2 mutant lines containing gypsy retrovirus insertions revealed that the gypsy insulator may be placed close to the yellow promoter region and be intimately involved in transcriptional activation and repression. Therefore, we suggest that insulators may also function by mediating long range interactions between enhancers and promoters.

Polarization dependences of optical devices in highly-integrated optical systems become a major problem. To overcome this issue, one can implement polarization diversity scheme to achieve a single polarization on-chip network. One of the essential components in a polarization diversity scheme is the polarization beam splitter (PBS). In this thesis, we will a PBS based on a silicon-on-insulator (SOI) platform with reduced device size and broad operation bandwidth. We use the three-dimensional Finite-Difference Time-Domain (3D-FDTD) method to perform the simulation. First, we use two asymmetric waveguides to design an asymmetric directional coupler with only TE-like mode phase matching condition. We then tape the lower waveguide to keep the TE-polarized light, and split the TE- and TM- polarized light. By utilizing an asymmetrical directional coupler with a tapered waveguide, we have achieved a 7.3

This thesis presents the design and fabrication of coplanar waveguide to microstrip transitions and planar spiral inductors, and the design of metal-insulator-metal capacitors, a planar band-pass, and a low-pass filter structures as an application for the inductors and capacitors using the RF MEMS technology. This thesis also includes a packaging method for RF MEMS devices with the use of benzocyclobutene as bonding material. The transition structures are formed by four different methods between coplanar waveguide end and microstrip end, and they are analyzed in 1-20 GHz. Very low loss transitions are obtained by maintaining constant characteristic impedance which is the same as the port impedance through the transition structures. The planar inductors are formed by square microstrip spirals on a glass substrate. Using the self-inductance propery of a conductive strip and the mutual inductance between two conductor strips in a proper arrangement, the inductance value of each structure is defined. Inductors from 0.7 nH up to 20 nH have been designed and fabricated. The metal-insulator-metal capacitors are formed by two coplanar waveguide structures. In the intersection, one end of a coplanar waveguide is placed on top of the end of the other coplanar waveguide with a dielectric layer in between. Using the theory of parallel plate capacitors, the capacitance of each structure is adjusted by the dimensions of the coplanar waveguides, which obviously adjust the area of intersection. Capacitors from 0.3 pF up to 9.8 pF have been designed. A low-pass filter and a band-pass filter are designed using the capacitors and inductors developed in this thesis. In addition to lumped elements, the interconnecting transmission lines, junctions and input-output lines are added to filter topologies. The RF MEMS packaging is realized on a coplanar waveguide structure which stands on a silicon wafer and encapsulated by a silicon wafer. The capping chip stands on the BCB outer ring which promotes adhesion and provides semi hermeticity. Keywords: Transition between transmission lines, planar spiral inductor, metal-insulator-metal capacitor, RF MEMS packaging, surface micromachining.

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Detectors and sensors are an integral part of modern electronics and are crucial to highly sensitive applications. Metal-Insulator-Metal (MIM) tunnel junctions have been explored for the past five decades and are still being investigated due to its wide use of applications such as mixers, capacitors, detectors, rectifiers and energy conversion devices. In this research, various designs of thin film based tunnel junctions have been investigated and the optimum one picked for the purpose of a wide band detector up to 10GHz based on their sensitivities. A modified design with an isolation layer incorporating a self-aligning method to increase fabrication throughput was developed. A mask for the reliability testing of multiple devices with different areas was also developed. Nickel Oxide based insulators with different stoichiometries have been incorporated in the fabrication of the device to identify which stoichiometry gives the best performance for high frequency applications. Nickel Oxide (NiO), Zinc Oxide (ZnO) and the combination of the two have been deposited using reactive sputtering and investigated as insulator materials. The bilayer devices showed increased sensitivities at lower turn on voltages and very good efficiencies at 100MHz and 1GHz. Although, the MIM device provides a simple structure, some of the critical parameters required to quantify the device functionality are still being explored. Based on the parameters, a criterion was developed to help engineer a tunnel device for a desired detectivity.

There is no apparent, dominant interaction in heavy transition metal oxides (TMO), especially in 5d-TMO, where all relevant interactions are of comparable energy scales, and therefore strongly compete. In particular, the spin-orbit interaction (SOI) strongly competes with the electron-lattice and on-site Coulomb interaction (U). Therefore, any tool that allows one to tune the relative strengths of SOI and U is expected to offer an opportunity for the discovery and study of novel materials. BaIrO3 is a magnetic insulator driven by SOI whereas the isostructural BaRuO3 is a paramagnetic metal. The contrasting ground states have been shown to result from the critical role of the strong SOI in the iridate. This dissertation thoroughly examines a wide array of newly observed novel phenomena induced by adjusting the relative strengths of SOI and U via a systematic chemical substitution of the Ru4+(4d4) ions for Ir4+(5d5) ions in BaIrO3, i.e., in high quality single crystals of BaIr1-xRuxO3(0.0 < x < 1.0) . Our investigation of structural, magnetic, transport and thermal properties reveals that Ru substitution directly rebalances the competing energies so profoundly that it generates a rich phase diagram for BaIr1-xRuxO3 featuring two major effects: (1) Light Ru doping (0 < x < 0.15) prompts a simultaneous and precipitous drop in both the magnetic ordering temperature TC and the electrical resistivity, which exhibits metal-insulator transition at around TC. (2) Heavier Ru doping (0.41 < x < 0.82) induces a robust metallic and spin frustration state. For comparison and contrast, we also substituted Rh4+(4d5) ions for Ir4+(5d5) ions in BaIrO3, i.e. BaIr1-xRhxO3(0.0 < x < 0.10), where Rh only reduces the SOI, but without altering the band filling. Hence, this system remains tuned at the Mott instability and is very susceptible to disorder scattering which gives rise to Anderson localization.

No description available.

Il sera question dans ce mémoire de maîtrise de l’étude d’une nouvelle classification des états solides de la matière appelée isolant topologique. Plus précisément, nous étudierons cette classification chez le composé demi-Heusler GdBiPt. Nous avons principalement cherché à savoir si ce composé ternaire est un isolant topologique antiferromagnétique. Une analyse de la susceptibilité magnétique ainsi que de la chaleur spécifique du maté- riau montre la présence d’une transition antiferromagnétique à 8.85(3) K. Une mesure d’anisotropie de cette susceptibilité montre que les plans de spins sont ordonnés sui- vant la direction (1,1,1) et finalement des mesures de résistivité électronique ainsi que de l’effet Hall nous indiquent que nous avons un matériau semimétallique lorsque nous sommes en présence d’antiferromagnétisme. Présentement, les expériences menées ne nous permettent pas d’associer cet état métallique aux états surfaciques issus de l’état d’isolant topologique. / In this thesis will be discussed the study of a new way of characterizing state of matter called a topological insulator. We have mainly investigated whether the ternary compound GdBiPt, from the family of half-Heusler compounds, is an antiferromagnetic topological insulator. An analysis of the magnetic susceptibility and the specific heat of the material shows the presence of an antiferromagnetic transition at 8.85(3) K. A measurement of the anisotropy of the susceptibility shows that plan of spins are ordered according to the crystalline direction (1,1,1) and finally, measurements of electronic re- sistivity and Hall effect indicate that we have a semimetallic material when we are in the presence of antiferromagnetism. At the present, these experiments do not allow us to as- sociate this metallic state with the surface states associated with the topological insulator state of matter.

Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 110-113). Also available in electronic format on the Internet.