One of two project reports. Part A can be found at: http://hdl.handle.net/11375/18452 / No abstract was provided. / Thesis / Master of Engineering (ME)

One of two project reports. Part B can be found at: http://hdl.handle.net/11375/18523 / Recent measurements of the sputtering of frozen gases by MeV ions gave yields several orders of magnitude greater than predicted by collision cascade theory. Only a "thermal spike" model, invoking a coupling of electronic excitation to nuclear motion, agrees qualitatively with experimental results. Yields of 300 keV to 2 MeV ions ranging in mass from 4 a.m.u. to 40 a.m.u. were investigated for ice, Kr and Xe films in the temperature range of 15°K to 120°K. / Thesis / Master of Engineering (ME)

Missing page 91 / <p> This report presents a numerical method which can be used to solve the advection equation </p> <p> (∂ɸ/∂t) + (∂[u(x,t)ɸ]/∂x) = S(x,t) </p> where: </p> <p> ɸ ≣ concentration field </p> <p> u(x,t) ≣ velocity field </p> <p> S(x,t) ≣ source term </p> <p> Central to this method are the concept of particle path and the Eulerian interpretation of the time rate of change of the concentration field ɸ. </p> In actual comparison tests for particular cases with known solutions this method proved to be at least two orders of magnitude more accurate than the usual one sided upwind finite difference method. </p> / Thesis / Master of Engineering (ME)

Pages viii, xii, xiv, 32, 110, 182, 188, 194 were blank and therefore omitted. / <p> The functional density of photonic integrated circuits can be significantly increased by stacking multiple waveguide layers. These vertically-integrated devices require optical couplers to switch light signals between their layers. In this thesis, optical coupling between two stacked silicon-on-insulator slab waveguides has been demonstrated with a coupling efficiency of 68±4%, obtained with a coupler length of 3535 μm. The main advantage of using a silicon-based material system for photonic integrated circuits is its compatability with existing electronics manufacturing processes, facilitating cost-effective fabrication and the monolithic integration of both photonics and electronics on a single device. </p> <p> Coupling between more complex silicon-on-insulator waveguide structures with lateral confinement was then demonstrated. The coupling ratio between stacked silicon rib wavelengths was measured to be 54±4%, while ratios of 71±4% and 93±4% were obtained for stacked channel waveguide and multimode interferometer-based couplers respectively. The corresponding coupler lengths for these three designs were 572 μm, 690 μm and 241 μm respectively. The sensitivity of these couplers to the input wavelength and polarization state has also been evaluated. These vertical-integrated couplers, along with other structures, have been thoroughly simulated, including their tolerance to fabrication errors. Novel fabrication processes used to demonstrate coupling in proof-of-concept devices have been developed, including an in-house wafer bonding procedure. </p> / Thesis / Doctor of Philosophy (PhD)

<p>Optical coatings have been applied to the facets of semiconductor diode lasers using the electron cyclotron resonance plasma enhanced chemical vapour deposition technique. Processes have been developed for the fabrication of optical interference filters from silicon oxynitride thin films using both tris dimethylaminosilane and silane as the silicon precursor. An important component for the fabrication of filters with a controlled reflectance index by ellipsometry. Using the ellipsometer, it is shown that, after correcting for systematic errors, an accurate measurement of the film index of refraction can be made during a deposition. Three separate applications of these optical coatings are discussed. The fabrication of anti-reflection coatings, the fabrication of narrow band reflectance coatings which could potentially have beneficial effects on the spectral properties of the laser and the use of silicon nitride layers, in conjunction with a sulphur based passivation, to improve the reliability of high power AlGaAs based lasers. Single and double layer anti-reflection coatings have been designed for specific laser waveguide structures. An existing theoretical model of the spectral output of a semiconductor laser has been modified to include the effect of an optical filter with a highly wavelength dependent reflectance, in order to understand the limitations of this technique. Finally, improvements in the surface properties of passivated and encapsulated AlGaAs material have been observed through an increase in the yield of photoluminescence after the passivation process was applied.</p> / Doctor of Philosophy (PhD)

<p>Electric field induced changes in the excitonic band-edge absorption spectra of Multiple Quantum-Well (MQW) structures were investigated theoretically and experimentally. Three In(x)Ga(1-x)-GaAs quantum-well p-i-n waveguide structures were designed, and were then grown by the National Research Council of Canada. Band edge absorption changes with field were then investigated using light incident perpendicular to the sample surface. Theoretically, a comparison was made of three different exactly solvable methods for calculating quantum-well energies in an electric field, both with and without conduction-band non-parabolicity. An exactly solvable method was used to calculate the hole dispersion and thereby determine the heavy-hole parallel effective mass. By using calculated wavefunctions, and these mass values, a numerical method was used (Wu, 1989) to solve for the exciton binding energies. After determining broadening factors, the absorption edge was calculated at low and moderate fields for three In(x)Ga(1-x)As-GaAs structures for various fields. At high fields, a different Franz-Keldysh type of absorption calculation was developed. Comparisons vs. experiment were favourable, but some discrepancy was noted. Slab and rib waveguide modulators, with operating wavelengths from about 970nm to 1035nm, were processed from the three material growths. Waveguiding transmission spectra again agreed favourably with theory, although some differences were seen. The modulators typically exhibited greater than 20 dB of switching over a 40nm range with less than 2 dB of low-bias absorption loss. Switching speed was not examined. Theoretical analysis of different structures revealed many trade-offs, in design, with 3% to 17% indium, and 6.5nm to 13nm well-widths being acceptable.</p> / Doctor of Philosophy (PhD)

<p>The optical efficiency of a commercially available sputter deposited spectrally selective solar absorber was improved. The main purposes were to decrease the thermal emittance, increase the solar absorbtance of the absorber and to protect the substrate from degradation due to environmental influence. The adhesion properties between the corrosion-protecting barrier and the substrate were also studied. This project was focused on process improvements that are realistic to implement in industrial production.</p><p>The thermal emittance of the absorber was decreased from 0.12 to 0.06 by changing the material of the corrosion-protecting layer from nickel-chromium to copper-nickel. Copper-nickel was less sensitive to variations in the sputter parameters than nickel-chromium. A novel method that could simplify the search for alternative corrosion resistant materials with a low thermal emittance has been purposed. Since resistivity data usually exist or can easily be measured and infrared measurements require more sophisticated measurements, the Hagen-Rubens relation was investigated for copper-nickel and nickel-chromium alloys. The dc-resistivity was found to be related to the infrared emittance or the integrated thermal emittance for alloys in their solid soluble fcc phase.</p><p>The solar absorbtance was increased when a graded index absorbing coating was tailored for a crossover of the reflectance from low to high reflectance at about 2.5 µm. The solar absorber graded index coating was optimized for nickel metal content in nickel oxide and a solar absorptance of 0.89-0.91 was achieved. The solar absorptance was further increased to 0.97 when an antireflection coating was added on top of the absorbing layer.</p><p>Finally, extrapolation algorithms were developed to assure correct determination of the thermal emittance for coatings on glass since modern spectrometers that do not cover the complete wavelength interval required to calculate the thermal emittance of surfaces at room temperatures accurately. The error arising from the extrapolation algorithms were smaller than the noise from the optical measurements. Similar strategies can be used for other surfaces.</p>

<p>Ceramics constitute an important group of low-density armour materials. Their high intrinsic strength makes it possible to design ceramic armour systems capable of defeating projectiles directly on the ceramic surface. This capability, named interface defeat, signifies that the projectile material is forced to flow radially outwards on the surface of the ceramic without penetrating significantly.</p><p>This thesis presents impact experiments between long-rod projectiles and ceramic targets. The projectile/target interaction was studied using flash X-ray technique. Transition velocities (the impact velocity at which interface defeat can no longer be maintained and penetration starts) were estimated for different combinations of metallic projectiles and ceramic targets and compared to critical velocities estimated on a theoretical basis. Replica scaling experiments were also performed in order to investigate the possible influence of scale.</p><p>All ceramic materials tested showed a distinct transition from interface defeat to penetration. Experiments with different silicon carbides showed that the transition velocity correlated better with the fracture toughness than with the hardness of the ceramic materials. For conical projectiles, penetration occurred along a conical surface crack and at a lower transition velocity than that observed for cylindrical projectiles. Experiments with unconfined alumina targets in different scales showed only a slight increase in dimensionless final penetration with length scale.</p><p>A unique transition velocity seems to exist for each combination of projectile, target material and target configuration. This velocity was found to depend on both the strength (hardness) and the brittleness (fracture toughness) of the ceramic. The lower transition velocity of conical projectiles compared with cylindrical ones is mainly due to the radially expanding load and the penetration of projectile material into surface cracks. The results of the experiments in different scales indicate that replica scaling is valid for penetration in ceramics.</p>

<p>Microengineering has developed a broad range of production techniques to reduce size, increase throughput, and reduce cost of electrical and mechanical devices. The miniaturisation has also entailed entirely new opportunities.</p><p>In this work, a piezoresistive silicon sensor measuring mechanical deformation has been designed and fabricated with the help of microengineering. Due to the large variety of used processes, this device can serve as a survey of techniques in this field. Four basic process categories are recognised: additive, subtractive, modifying, and joining methods.</p><p>The last category, joining methods, has previously been the least investigated, especially when it comes to compatibility with the other categories. The adaptability of wet chemical etching to established silicon wafer bonding technique has been investigated. Further, phenomena related to oxygen plasma pre-treatment for direct bonding has been investigated by blister bond adhesion tests, X-ray photoelectron spectroscopy, and atomic force microscopy.</p><p>Wafer bonding has been adapted to monocrystalline quartz. For wet chemical pre-treatment, characteristics specific for quartz raise obstacles. Problems with limited allowable annealing temperature, low permeability of water released in the bond at annealing, and electrostatic bonding of particles to the quartz surface, have been studied and overcome. The influence of internal bond interfaces on resonators has been investigated.</p><p>Chemical polishing of quartz by ammonium bifluoride has been experimentally investigated at high temperatures and concentrations. Chemometrical methods were used to search for optimum conditions giving the lowest surface roughness. These extreme conditions showed no extra advantages.</p><p>Adhesion quantification methods for wafer bonding have been comprehensively reviewed, and augmentations have been suggested. The improved techniques’ usefulness for three areas of use has been forecasted: general understanding, bonding scheme optimisation, and quality control. It was shown that the quality of measurements of all commonly used methods could be dramatically improved by small means.</p>

<p>In recent years portable electronic devices, such as mobile phones and personal digital assistants, have increased the demand for high performance displays with low power consumption. An interesting candidate with the potential of fulfilling these demands is the reflective single-polarizer surface controlled bistable twisted nematic liquid crystal display. The main focus of this work involves the optical properties of displays based on these bistable structures. In the investigations, the display is considered as an integrated optical system, containing not only the liquid crystal cell, but also components such as polarizers and retardation films. The specific aim of the thesis was to derive new optical modes of the reflective single-polarizer bistable twisted nematic device using the Jones matrix method to study the interaction between the polarization of light and the optically anisotropic media. The electro-optical properties of the derived modes have been studied and evaluated both theoretically and experimentally. The modes possess excellent brightness and high contrast ratio. By introducing a quarter-wave retardation film into the optical configuration, the contrast ratio can be significantly increased by preventing spectral leakage of light in the dark state. To experimentally realize the derived optical modes, special layers for the alignment of the liquid crystal molecules on the cell substrate surface have been proved needed. Therefore, also the photo-alignment technology of nematic liquid crystals on novel alignment materials has been studied with the aim to control liquid crystal cell parameters such as pretilt angle and anchoring energy, both critical for the bistable switching. The results of this thesis will increase the understanding of the optical properties of the reflective single-polarizer bistable twisted nematic liquid crystal display and will be valuable when considering this type of device for practical applications.</p>