In the past few decades, Si-based CMOS technology is approaching to its physical quantum limit by scaling down the gate length and gate oxide thickness to achieve higher drive current for low power and high speed application. High k/III-V stack provides an alternative solution because III-V based metal-oxide-semiconductor (MOS) devices have higher drive current due to the higher electron mobility than silicon. Also high k oxides lower the gate leakage current significantly due to larger thickness under the same equivalent oxide thickness (EOT) compared with SiO₂ beyond the 22 nm node. The main obstacle for high k/III-V based MOSFETs is the lack of high quality, thermodynamically stable insulators that passivate the interface, which is also the main driving force in the research area of high k/III-V stack. One of the main focuses of this dissertation is developing a fabrication process flow to lower the interface trap density to enhance the performance of MOSFETs with high k oxides on III-V substrates. Also, an emerging memory device with SiO[subscript x] is also developed. This device can be electrically switched between a high-resistance state (HRS, or OFF-state) and a low-resistance state (LRS, or ON-state). Also it shows high potential for next generation nonvolatile memories due to its small cell area, fast write/erase time, low write voltage, good endurance and scalability. The other main focuses of this dissertation is studying the electroforming, set/reset voltages and passivation issue in this resistive random access memory (RRAM or ReRAM). The first part of this dissertation is about lowering the interface trap density of high k/III-V stack by using a thin layer of Al₂O₃ or LaAlO₃. ALD Al₂O₃/HfO₂ bi-layer gate oxide with different Al₂O₃ thickness (0, 5, 10Å) was deposited. Also ALD LaAlO₃/HfO₂ bi-layer gate oxide with different LaAlO₃ thickness (0, 5, 10, 20, 30, 42Å) was deposited. The total EOT of the bi-layer was maintained at ~1.8nm. Also single La[subscript x]Al[subscript 1-X]O (X =0.25, 0.33, 0.5, 0.66, 0.75) gate dielectric with different La doping level was deposited (EOT=2.5±0.4nm). Device characteristics are compared by using different thickness of interfacial layer. The second part of this dissertation is about F incorporation into high k oxide by using SF₆ plasma. The effect of SF₆ plasma treatment of HfO₂ on III-V substrates is demonstrated. Also effect of different plasma power and different treatment time of SF₆ plasma is studied to optimize plasma conditions. High k bilayer (Al₂O₃/HfO₂) is also used to further improve the device performance by better interface passivation with Al₂O₃. HfO₂ gate oxide dielectric is also engineered using SF₆ plasma treatment to incorporate more F. The third part is a study of III-V tunneling FET using In[subscript 0.7]Ga[subscript 0.3]As p-n junction. The device performance with different n doping concentration is compared. Higher n doping concentration will increase the drive current by reducing the tunneling width while too higher n doping concentration results in tunneling in the middle of p-n junction and significantly increase the subthreshold swing. The forth part is the electroforming, set/reset and passivation study of ReRAM device with SiO[subscript x]. Different methods to reduce the electroforming voltage are developed. Set/reset process is also studied and a possible model is proposed to explain the set/ reset process. A new device structure without sidewall edge is studied for passivation and application in air. The final part is the summary of Ph.D work and also suggestions for future work are discussed. / text

Continuous downscaling of transistor size has been the major trend of the semiconductor industry for the past half century. In recent years, however, fundamental physical limits to continued downscaling were encountered. In order to overcome these limits, the industry experimented --- and continues to experiment --- with many new materials and architectures. Non-invasive, in-line methods of characterizing critical properties of these structures are in demand. This dissertation develops optical second-harmonic generation (SHG) to characterize performance-limiting defects, band alignment or strain distribution in four advanced electronic material systems of current interest: (1) Hot carrier injection (HCI) is a key determinant of the reliability of ultrathin silicon-on-insulator (SOI) devices. We show that time-dependent electrostatic-field-induced SHG probes HCI from SOI films into both native and buried oxides without device fabrication. (2) Band offsets between advanced high-k gate dielectrics and their substrates govern performance-limiting leakage currents, and elucidate interfacial bond structure. We evaluate band offsets of as-deposited and annealed Al₂O₃, HfO₂ and BeO films with Si using internal photoemission techniques. (3) Epi-GaAs films grown on Si combine the high carrier mobility and superior optical properties of III-V semiconductors with the established Si platform, but are susceptible to formation of anti-phase boundary (APB) defects. We show that SHG in reflection from APB-laden epi-films is dramatically weaker than from control layers without APBs. Moreover, scanning SHG images of APB-rich layers reveal microstructure lacking in APB-free layers. These findings are attributed to the reversal in sign of the second-order nonlinear optical susceptibility [chi]⁽²⁾ between neighboring anti-phase domains, and demonstrate that SHG characterizes APBs sensitively, selectively and non-invasively. (4) 3D integration --- i.e. connecting vertically stacked chips with metal through-Si-vias (TSVs) --- is an important new approach for improving performance at the inter-chip level, but thermal stress of the TSVs on surrounding Si can compromise reliability. We present scanning SHG images for different polarization combinations and azimuthal orientations that reveal the sensitivity of SHG to strain fields surrounding TSVs. Taken together, these results demonstrate that SHG can identify performance-limiting defects and important material properties quickly and non-invasively for advanced MOSFET device applications. / text

The semiconductor alloy indium gallium nitride (InxGa1-xN) offers substantial potential in the development of high-efficiency multi-junction photovoltaic devices due to its wide range of direct band gaps, strong absorption and other optoelectronic properties. This work uses a variety of characterization techniques to examine the properties of InxGa1-xN thin films deposited in a range of compositions by a novel plasma-enhanced evaporation deposition system. Due to the high vapour pressure and low dissociation temperature of indium, the indium incorporation and, ultimately, control of the InxGa1-xN composition was found to be influenced to a greater degree by deposition temperature than variations in the In:Ga source rates in the investigated region of deposition condition space. Under specific deposition conditions, crystalline films were grown in an advantageous nano-columnar microstructure with deposition temperature influencing column size and density. The InxGa1-xN films were determined to have very strong absorption coefficients with band gaps indirectly related to indium content. However, the films also suffer from compositional inhomogeneity and In-related defect complexes with strong phonon coupling that dominates the emission mechanism. This, in addition to the presence of metal impurities, harms the alloy’s electronic properties as no significant photoresponse was observed. This research has demonstrated the material properties that make the InxGa1-xN alloy attractive for multi-junction solar cells and the benefits/drawbacks of the plasma-enhanced evaporation deposition system. Future work is needed to overcome significant challenges relating to crystalline quality, compositional homogeneity and the optoelectronic properties of In-rich InxGa1-xN films in order to develop high-performance photovoltaic devices. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2011-09-29 21:28:58.898

Les récepteurs couplés aux protéines G (RCPG) font partie de la plus importante famille de récepteurs membranaires. Leur implication dans une grande majorité de processus physiologiques et pathologiques en fait une cible pharmaceutique de choix. Parmi les RCPG, nous avons déjà démontré que le récepteur de la neurotensine NTS2 joue un rôle important dans la régulation de la transmission de l'information nociceptive. Cependant, des études ont révélé que le récepteur NTS2 est principalement localisé dans des compartiments intracellulaires et est notamment stocké dans l'appareil de Golgi. Par conséquent, les processus de transport et de trafic du récepteur vers la membrane plasmique sont critiques pour son activation par des agonistes exogènes. Dans le but d'étudier les mécanismes qui conduisent à l’insertion du récepteur NTS2 à la surface cellulaire, nous avons procédé à un criblage en double hybride chez la levure pour identifier des protéines potentiellement impliquées dans la régulation du trafic de NTS2. Nous avons utilisé le fragment correspondant à la troisième boucle intracellulaire du récepteur NTS2 comme appât pour cribler une banque d'ADNc de cerveau de rat. Cet essai a permis d'identifier la sécrétogranine III (SCG3), une protéine de la voie de sécrétion régulée, comme partenaire d'interaction du récepteur NTS2. Pour mieux caractériser cette association, les protéines taguées HA-NTS2 et YFP-SCG3 ont été co-exprimées dans les cellules HEK-293 et immunoprécipitées. L'analyse par immunobuvardage de type Western a révélé la présence de bandes à 45 et 80 KDa, correspondant au récepteur HA-NTS2 et à la protéine YFP-SCG3 respectivement, démontrant l'interaction par la co-immunoprécipitation des protéines. Des études de microscopie confocale effectuées sur des cellules HEK-293 coexprimant CFP-NTS2 et YFP-SCG3, ont également montré que les deux protéines colocalisent à l’échelle subcellulaire. Des analyses de transfert d'énergie entre molécules fluorescentes (frT) ont été réalisées afin de confirmer l'interaction moléculaire NTS2-SCG3. Enfin, dans le but de déterminer l'impact physiologique de la régulation de l'adressage à la membrane plasmique du récepteur NTS2 par la SCG3, nous avons développé deux DsiRNA afin de réduire l'expression de SCG3. Ces DsiRNA dirigés contre SCG3 validés in vitro seront prochainement utilisés in vivo chez le rat adulte afin d'examiner leurs effets sur le rôle du récepteur NTS2 dans le contrôle de la douleur. Ainsi, nos résultats suggèrent que la SCG3 pourrait servir de protéine escorte pour NTS2 dans son adressage vers la membrane plasmique. Aussi, nos résultats renforcent l'idée que les RCPG ne sont pas seulement adressés à la surface cellulaire par la voie constitutive mais qu'ils peuvent être transportés via la voie de sécrétion régulée. Finalement, ces résultats suggèrent que l'interaction physique entre NTS2 et SCG3 pourrait affecter la fonction physiologique du récepteur NTS2, y compris son rôle dans le contrôle de la douleur.

No description available.

Successful bacterial pathogens manipulate crucial intracellular host processes as a virulence strategy. One particular potent mechanism utilized by bacterial phytopathogens is to inject virulence factors (effectors) directly into the host cell. While many effectors have been identified and shown to suppress plant immune responses, very few have well-characterized enzymatic activities or host targets. To overcome the challenges of functional analysis of effectors, I designed two heterologous screens to characterize effector proteins of the bacterial phytopathogen Pseudomonas syringae. Specifically, my objective was to identify those P. syringae effectors that target evolutionarily conserved host proteins or processes and to subsequently elucidate the molecular mechanisms of these effectors. The first heterologous screen that I performed was to utilize tandem-affinity-purification (TAP)-tagged effectors in human cells to identify potential interacting host proteins. The second heterologous screen iii utilized a high-throughput genomics approach in yeast, known as the pathogenic genetic array (PGA), to characterize P. syringae effectors. Using the first heterologous approach, I have identified HopZ1a as the first bacterial phytopathogen effector that binds tubulin. I have shown that HopZ1a is an acetyltransferase activated by the eukaryotic co-factor, phytic acid. In vitro, activated HopZ1a acetylates itself and tubulin. In Arabidopsis thaliana, activated HopZ1a causes microtubule destruction, disrupts the secretory pathway and suppresses cell wall-mediated defense. The acetyltransferase activity of HopZ1a is dependent on the conserved catalytic cysteine residue (C216) and a conserved lysine residue (K289). Using the second heterologous screen in yeast, I have shown that HopZ1a may target the mitogen-activated protein kinase (MAPK) signaling cascades. Together, my work has identified novel eukaryotic targets and elucidated the virulence functions of HopZ1a.

Successful bacterial pathogens manipulate crucial intracellular host processes as a virulence strategy. One particular potent mechanism utilized by bacterial phytopathogens is to inject virulence factors (effectors) directly into the host cell. While many effectors have been identified and shown to suppress plant immune responses, very few have well-characterized enzymatic activities or host targets. To overcome the challenges of functional analysis of effectors, I designed two heterologous screens to characterize effector proteins of the bacterial phytopathogen Pseudomonas syringae. Specifically, my objective was to identify those P. syringae effectors that target evolutionarily conserved host proteins or processes and to subsequently elucidate the molecular mechanisms of these effectors. The first heterologous screen that I performed was to utilize tandem-affinity-purification (TAP)-tagged effectors in human cells to identify potential interacting host proteins. The second heterologous screen iii utilized a high-throughput genomics approach in yeast, known as the pathogenic genetic array (PGA), to characterize P. syringae effectors. Using the first heterologous approach, I have identified HopZ1a as the first bacterial phytopathogen effector that binds tubulin. I have shown that HopZ1a is an acetyltransferase activated by the eukaryotic co-factor, phytic acid. In vitro, activated HopZ1a acetylates itself and tubulin. In Arabidopsis thaliana, activated HopZ1a causes microtubule destruction, disrupts the secretory pathway and suppresses cell wall-mediated defense. The acetyltransferase activity of HopZ1a is dependent on the conserved catalytic cysteine residue (C216) and a conserved lysine residue (K289). Using the second heterologous screen in yeast, I have shown that HopZ1a may target the mitogen-activated protein kinase (MAPK) signaling cascades. Together, my work has identified novel eukaryotic targets and elucidated the virulence functions of HopZ1a.

In New Zealand, Māori currently experience the "poorest health status of any ethnic group" characterised by high rates of physical and mental illness, educational underachievement, unemployment, criminal incarceration, and low socioeconomic status (Durie, 1998; Ministry of Health, 1999, 2002a, p. 2). Despite attempts to reduce the disparities between Māori and other New Zealanders, Māori continue to have a lower life expectancy than non-Māori (Durie, 1998; Reid, 1999). Māori children show similar levels of disadvantage experiencing high rates of illness and preventable death (Ministry of Health, 1998). Māori children also achieve poorly in educational settings, with literacy levels and overall involvement in education found to be below that of non-Māori (Ministry of Education, 2003a). Research findings have identified that health and educational disparities may be explained in part, by a mismatch between current approaches to practice and service delivery, and the values, beliefs, and experiences of Māori (Phillips, McNaughton, & MacDonald, 2004). In line with such findings, a number of standardised psychometric tests developed outside of New Zealand, have also been found to produce culturally biased results when used with Māori (Ogden, 2003; Ogden & McFarlane-Nathan, 1997). The Peabody Picture Vocabulary Test (PPVT-III) is one such test which is currently used in New Zealand to measure receptive vocabulary skills (Stockman, 2000). This research investigated the suitability of the PPVT-III with 46 Māori children from three different age groups. Results revealed that the PPVT-III appeared to be suitable for use with Māori, although a number of suggestions were made as to ways in which the administration and interpretation of PPVT-III test scores could be adjusted when working with Māori. Additional research is required to establish whether changes to culturally biased items may improve the validity of the PPVT-III for use with Māori.

Duisburg, Essen, Universiẗat, Diss., 2005.

Thesis (M.S.)--University of Michigan, 1974.