In order to continue with metal-oxide-semiconductors (CMOS) transistor scaling and to reduce the power density, the channel should be replaced with a material having a higher electron mobility, such as a III-V semiconductor. However, the integration of III-V's is a challenge because these materials oxidize rapidly when exposed to air and the native oxide produced is characterized by a high density of defects. Deposition of high-k materials on III-V semiconductors using Atomic Layer Deposition (ALD) reduces the thickness of these oxides, improving the semiconductor/oxide interface quality and the transistor electrical characteristics. In this work, ALD is used to deposit two dielectrics, Al₂O₃ and TiO₂, on two III-V materials, GaAs and InGaAs, and in-situ X-ray photoelectron spectroscopy (XPS) and in-situ thermal programmed desorption (TPD) are used for interface characterization. Hydrofluoric acid (HF) etching of GaAs(100) and brief reoxidation in air produces a 9.0 ± 1.6 Å-thick oxide overlayer containing 86% As oxides. The oxides are removed by 1 s pulses of trimethylaluminum (TMA) or TiCl₄. TMA removes the oxide overlayer while depositing a 7.5 ± 1.6 Å thick aluminum oxide. The reaction follows a ligand exchange mechanism producing nonvolatile Al-O species that remain on the surface. TiCl₄ exposure removes the oxide overlayer in the temperature range 89°C to 300°C, depositing approximately 0.04 monolayer of titanium oxide for deposition temperatures from 89°C to 135°C, but no titanium oxide is present from 170°C to 230°C. TiCl₄ forms a volatile oxychloride product and removes O from the surface while leaving Cl atoms adsorbed to an elemental As layer, chemically passivating the surface. The native oxide of In(0.53)Ga(0.47)As(100) is removed using liquid HF and gas phase HF before deposition of Al₂O₃ using TMA and H₂O at 170°C. An aluminium oxide film with a thickness of 7.2 ± 1.2 Å and 7.3 ± 1.2 Å is deposited during the first pulse of TMA on liquid and gas phase HF treated samples, respectively. After three complete ALD cycles the thickness of the aluminum oxide film is 10.0 ± 1.2 Å on liquid HF treated and 6.6 ± 1.2 Å on gas phase HF treated surfaces. Samples treated with gas phase HF inhibit growth. Inhibition is caused by residual F atoms that passivate the surface and by surface poisoning due to the thicker carbon film deposited during the first pulse of TMA. On InGaAs covered by native oxide, the first TMA pulse deposits 9 Å of aluminum oxide, and reaches saturation at 13 Å after 15 pulses of TMA. The film grows by scavenging oxygen from the substrate oxides. Substrate oxides are reduced by the first pulse of TMA even at 0°C. At 0°C, on a 9 Å thick Ga-rich oxide surface, 1 pulse of TMA mainly physisorbs and a limited amount of aluminum oxide is deposited. At 0°C, 110°C, and 170°C, more aluminum oxide is deposited on surfaces initially containing As oxide, and larger binding energy (BE) shifts of the O 1s peak are observed compared to surfaces that contain Ga oxides only, showing that As oxides improve the nucleation of Al₂O₃.

<p>While much is known about the abundance and genetic diversity of environmental microbial communities, little is known about their taxon-specific activity. In this thesis I address this gap using a model marine microbe, the cyanobacterium <italic>Prochlorococcus spp.</italic>, which numerically dominates tropical and subtropical open oceans and encompasses a group of genetically defined clades that are ecologically distinct. Ribosomal RNA is a promising indicator of in situ activity because of its essential role in protein synthesis as well as its phylogenetic information, which could be used to distinguish clades among mixed populations. Here I show that, in a laboratory system the specific growth rate of representative <italic>Prochlorococcus</italic> strains could be quantitative predicted from cellular rRNA content (assessed by RT-qPCR), cell size (assessed by flow cytometry) and temperature. Applying this approach in the field, I show unique clade-specific activity patterns for <italic>Prochlorococcus</italic>. For example, vertically within the euphotic zone, eHL-II activity is strongly impacted by light and is consistent with patterns of photosynthesis and on a horizontal transect from Hawaii to San Diego, eHL-I and eHL-II activities exhibit significant transitions and appear to be regulated by temperature, nutrient and vertical mixing gradients. Using ribosomal tag pyrosequencing of DNA and RNA, I have extended our observation to the Eubacterial community and described the biomass distribution (rDNA) and activity (rRNA) patterns from two representative depths (25 and 100 m) at a well-studied oligotrophic ocean station. These results show that for some populations the abundances and activities are significantly uncoupled, which suggests substantial top-down controls or physical transport processes. Further exploring the taxon-specific activity patterns along with abundances and environmental variables across time and space is essential to better understanding the dynamics of a complex microbial system as well as predicting the consequences of environmental change.</p> / Dissertation

Ingeniero Civil de Minas / La realización de esta memoria de título, consiste en evaluar la explotación de los yacimientos Quetena y Toki, utilizando lixiviación de caserones. El proyecto se evalúa a nivel de ingeniería de perfil, lo que implica que se utilizaron antecedentes de otras minas, con aspectos similares a la operación de esta, y el grado de detalles permite obtener un primer acercamiento a una aplicación a gran escala de este método. El método de explotación denominado lixiviación de caserones, consiste en la irrigación de soluciones a través del mineral quebrado, mediante tronadura. Lo cual permite un control adecuado de la lixiviación, al generar una diferencia de permeabilidad entre la roca in situ y el material tronado. Una vez captadas las soluciones por la base del caserón, el cobre es recuperado en las plantas de SX EW de manera convencional. Los yacimientos Toki y Quetena, lugar donde se está evaluando el método, se encuentran a menos de 5 km de Calama. Los cuerpos están cubiertos bajo una capa de gravas estériles, de un espesor que varía entre los 40 a 150 m, y la explotación se centró solo en la lixiviación de los óxidos presentes, cuyas reservas superan los 500 MTon a una ley de 0.42 %. La metodología consiste en el estudio de un proyecto minero, el cual contempla la realización de los siguientes análisis: diseño de la unidad básica de explotación, estimación de costos e inversión, determinación del ritmo óptimo de explotación, planificación y evaluación económica. Todo esto con la finalidad de determinar si el proyecto es rentable tanto técnica como económicamente. El diseño elegido comprende la construcción de caserones tipo sublevel stoping de 80 metros de alto, 100 metros de largo y 40 metros de ancho en el caso de los caserones primarios y 60 metros de ancho en el caso de los caserones secundarios. Los aspectos determinantes que permiten una operación rentable son: una baja inversión de capitales, debido a que no se requiere la construcción de plantas de procesamiento de minerales, el costos de transporte de mineral, el cual considera solo la extracción del esponjamiento a un ritmo de 12,000 Ton/día, pero lixiviando 60,000 Ton/día, y el costo total a cátodo de 2.3 US$/lb que hace rentable al proyecto. El proyecto de explotación resulta rentable, obteniendo un VAN de 171.2 MUS$ con una inversión de 200.1 MUS$, lo cual es más rentable económicamente que la explotación por rajo abierto.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

This thesis is concerned with measuring the fabric thermal performance of houses. This is important because the evidence shows that predictions of performance, based upon a summation of expected elemental performance, are prone to significant inaccuracy and in-situ performance is invariably worse than expected the so-called performance gap . Accurate knowledge of the thermal performance of houses could cause a shift in the way that houses are built, retrofitted and managed. It would enable quality-assurance of newly-built and retrofitted houses, driving an improvement in the energy performance of the housing stock. The current barrier to achieving these benefits is that existing measurement methods are impractically invasive for use on a mass-scale. The aim of this research is to address this issue by developing non-invasive fabric thermal performance measurement methods for houses. The co-heating test is currently the most used method for measuring whole-house fabric thermal performance; it is used to measure the Heat Loss Coefficient (HLC) of a house, which is a measure of the rate of heat loss with units of Watts per degree Kelvin. It has been used extensively in a research context, but its more widespread use has been limited. This is due to a lack of confidence in the accuracy of its results and the test s invasiveness (the house must be vacant for two weeks during testing, which has so far been limited to the winter months, and testing cannot be carried out in newly-built houses for a period of approximately one year due to the drying out period). To build confidence in the results of co-heating testing, the precision with which test results can be reported was determined by the combination of a sensitivity analysis to quantify measurement errors, and an analysis of the reproducibility of the test. Reproducibility refers to the precision of a measurement when test results are obtained in different locations, with different operators and equipment. The analysis of the reproducibility of the test was based upon a direct comparison of seven co-heating tests carried out by different teams in a single building. This is the first such analysis and therefore provides a uniquely powerful analysis of the co-heating test. The reproducibility and sensitivity analyses showed that, provided best practise data collection and analysis methods are followed, the HLC measured by a co-heating test can be reported with an uncertainty of ± 10%. The sensitivity analysis identified solar heat gains as the largest source of measurement error in co-heating tests. In response, a new approach for co-heating data collection and analysis, called the facade solar gain estimation method, has been developed and successfully demonstrated. This method offers a clear advancement upon existing analysis methods, which were shown to be prone to inaccuracy due to inappropriate statistical assumptions. The facade method allowed co-heating tests to be carried out with accuracy during the summer months, which has not previously been considered feasible. The demonstration of the facade method included a direct comparison against other reported methods for estimating solar gains. The comparison was carried out for co-heating tests undertaken in three buildings, with testing taking place in different seasons (winter, summer, and spring or autumn) in each case. This comparison provides a unique analysis of the ability of the different solar gain estimation methods to return accurate measurements of a house s HLC in a wide variety of weather conditions. Building on these results, a testing method was developed: the Loughborough In-Use Heat Balance (LIUHB). The LIUHB is a non-invasive measurement method, designed and tested in this study, which can measure the HLC of a house with an accuracy of ± 15% while it is occupied and used as normal. Measurements of energy consumption and internal temperature are discreetly collected over a period of three weeks, and combined with data collected at a local weather station to inform an energy balance, from which the HLC is calculated. This low impact monitoring approach removes the barriers to fabric thermal performance testing on a mass scale. The LIUHB has been successfully demonstrated in several comparative trials versus a baseline measurement provided by the co-heating test. The trials have included the application of extreme examples of synthetic occupancy conditions, testing in an occupied house, and quantification of the effects of a retrofit. Subject to further validation, the LIUHB has the potential to deliver many of the benefits associated with mass-scale measurement and quality assurance of housing performance.

In this thesis, we demonstrate in-situ scanning electron microscopy techniques for both electron beam lithography (EBL) and in-situ one dimensional nano materials electrical characterization. A precise voltage contrast image positioning for in-situ EBL to integrate nanowires into suspended structures for nanoswitch fabrication has been developed. The in-situ EBL eliminates the stage movement error and field stitching error by preventing any movements of the stage during the nanolithography process; hence, a high precision laser stage and alignment marks on the substrate are not needed, which simplifies the traditional EBL process. The ZnO piezoelectronics is also studied using nano-manipulators in scanning electron microscope. Methods to improve the contact have been demonstrated and the contacts between probe tips and the nanowires are found to have significant impact on the measurement results.