Thin film devices for windows, mirrors, space applications and other purposes, have become an essential part of modern technology. A great advantage with a thin film device is the small amount of material used and the compact volume of the device. Dynamic control of thin film device properties is usually obtained by the application of a potential with a resulting charge transport. To understand this charge transport, thus become of great importance to improve, develop, and invent new thin film devices. Charge transport in transition metal oxide thin films and electrochromic devices have been studied in this thesis using dielectric and electrochemical methods. The dielectric methods used are impedance spectroscopy, the isothermal transient ionic current technique and current-voltage measurements. The electrochemical methods include the galvanostatic intermittent titration technique and electrochemical impedance spectroscopy. Ion intercalation parameters have been obtained for sputtered and ALD ZrO2 and sputtered TiO2, and the ion conduction processes have been analysed. The dielectric permittivity of as-deposited as well as intercalated thin films of ZrO2 and TiO2 have been studied and electron conduction mechanisms in as-deposited films deduced. From the impedance spectroscopy it is found that the dielectric response changes drastically upon ion intercalation. The complex dielectric response suggests different relaxation processes being important at different levels of intercalation and an explanation built on defect induced dipoles is proposed. Moreover, ion transport in electrochromic devices has been studied. The transient ionic current has been analysed to extract transport parameters both in single layers and whole devices and a deeper understanding of the ionic motion has been achieved.

<p>This thesis presents investigations on ultrafast laser irradiation of silicon towards the goal of hybridizing ultrafast laser processing and conventional semiconductor fabrication techniques to improve device applications. The fundamental sub-threshold damage accumulation mechanisms for potential defect engineering applications were studied through the use of positron annihilation spectroscopy, in situ sample heating during laser irradiation, varying the laser repetition rate, and samples implanted with various ion species at different conditions. Positron annihilation spectroscopy results suggest an increase in the divacancy density at the surface region of silicon following near- and slightly sub-threshold ultrafast laser irradiations. Laser irradiations at increasing sample temperature up to 600°C show a general decreasing trend of single-shot thresholds, and an increase in the suppression of sub-threshold damage accumulation. There is also a temperature dependence on the surface morphology resulting from ultrafast laser irradiation. Ion implantation modified the ablation threshold fluence, and a dependence on the ion implantation conditions was observed. Surface microstructuring of silicon was shown to improve absorption of light with a sub-bandgap wavelength of 1550 nm. An initial attempt with sulfur implantation did not exhibit further improvement in the optical absorption, and first attempts in device fabrication did not provide photoresponsivity at sub-bandgap wavelengths. Ultrafast laser irradiation of SiO₂-on-Si structures yielded different modification thresholds for different thicknesses of the oxide layer. Surface morphologies obtained in the irradiation of these structures can affect potential applications. Selected studies of ultrafast laser irradiation of GaP, metal-SiO₂-Si structures, quartz, diamond, and porcine bone demonstrated similarities in ablation behavior and morphologies, and the potential for a broad range of applications. The results in combination with the proposed future work in this thesis can contribute to potential device applications while providing valuable insights into the ultrafast laser ablation mechanisms.</p> / Doctor of Philosophy (PhD)

<p>With the advances in MEMS technology, the studies of the properties of magnetic crystals have reached the microscopic level. Critical information such as the magnetization and susceptibility of a magnetic sample can be obtained using a microtorque magnetometer, such as ones incorporating piezoresistive or capacitive detection that have been fabricated and tested by earlier research groups. This type of magnetic information is useful in the study of superconductivity, for example. The microtorque magnetometer designed and fabricated in this thesis has the potential of being used in this field of study.</p> <p>This thesis describes the design, fabrication and testing of a capacitive microtorque magnetometer. By using ANSYS, a computer modelling program, an ideal model of the rotating microtorque magnetometer was devised. Fabrication involved testing a variety of procedures before establishing the successful and efficient method of building the microtorque magnetometer. A fifth order resonant mode was successfully detected during the testing stage. A method of studying the desired resonant mode has been devised and explained in the later chapters of this thesis.</p> / Master of Applied Science (MASc)

<p>An <em>isotype heterojunction</em> is a junction between two layers of dissimilar semiconductors both of which are doped either n-type or p-type. These semiconductor structures are found in a variety of optoelectronic devices, such as solar cells, semiconductor lasers, and detectors. Motivated by the structure of third generation inorganic solar cells, this thesis concentrates on the analytical modelling of isotype heterojunctions and its application to the design optimization of these devices. The main development of this work is the introduction of an analytical expression for the current density across an isotype heterojunction valid for arbitrary doping concentration ratios. This result generalizes the standard expression found in the literature, which is limited by the assumption that the doping concentration ratio between the two sides of the heterojunction is equal to one. The generalization is developed by employing the Lambert W function in the solution of the electrostatic boundary condition associated with the heterojunction interface. As done in the derivation of the standard expression found in the literature, the generalization only considers thermionic emission, but the same method can readily be applied for other transport mechanisms. A key feature of this generalized result is that it mathematically contains the expression for the current density across a metal-semiconductor Schottky contact as a limiting case, thereby unifying the treatment of these two heterointerfaces into a single general analytical description. This latter find is particularly significant from a theoretical perspective, considering that the two heterointerfaces are traditionally described as separate topics in the presentation of semiconductor device theory.</p> / Master of Applied Science (MASc)

<p>Mechanical instruments, such as saw and bur are commonly used for bone cutting during orthopedics surgeries. These conventional instruments showed good bone removal efficiency. Nonetheless, there are some issues with the use of the mechanical tools, such as ill-placed screws and elevation of tissue temperature, which results in thermal damage to the surrounding tissues. These difficulties accompanied with using mechanical tools led to laser ablation investigations. Lasers, including continues wave (CW) and pulsed, were considered to be a promising tool for bone ablation. When compared to mechanical tools, lasers produce less thermal damage to the surrounding tissues due to their ability to focus on a very small spot, which also produces more precise ablation. Lasers also produce no significant mechanical vibrations within the surrounding tissue and thus less mechanical damage and cracks occur during ablation. Performances of laser ablations are measured by several factors; such as collateral damage, machining time, ablated depth, and ablative precision. In this thesis work, a literature review was conducted with the aim of understanding the bone characteristics that are related to the optical properties of bone, which leads to a better understanding for ablation mechanisms. This helps in a proper choice of laser parameters for a certain tissue ablation, and thus avoiding collateral damage.</p> <p>Some laser parameters (pulse energy, scanning speed, and number of passes) were characterized as a first step towards producing large holes. The effect of each one of these laser parameters on the groove depth was found. The feasibility of the ultrafast laser in creating large scale holes was examined, using two scanning strategies: (i) concentric circles scanning, the largest crater depth measured using this procedure was 3.81 mm, (ii) helical scanning, which was used to reduce the machining time, using this procedure a micropillar was created with 12 passes in just 2.5 minutes.</p> / Master of Applied Science (MASc)

<p> A Pulse Forming Network (PFN) was built and optimized using an Algorithm based on theory and experimental data. The target load for the PFN was a Helical Electromagnetic Launcher. The target application of the launcher is Environmental Testing &mdash; mechanical shock &mdash; time domain replication. The new Algorithm that was used combines time, frequency, and energy domain methods to restrict the solution space before optimization. As in many other applications, the final optimization was done though experimental trial and error. The PFN ultimately met the repeatability and uncertainty targets specified by environmental engineers.</p>

<p> In this thesis, the conventional four-point measurement technique and the van der Pauw (vdP) method are systematically investigated in the presence of non-ideal conditions, namely, non-uniform carrier density distribution and absence of ohmic contacts, which are nonetheless commonly encountered in semiconductor characterizations. Upon understanding the challenges in the conventional methods, novel characterization techniques are developed to address these challenges. </p><p> A longitudinal magnetoresistance asymmetry method was developed to study the carrier density non-uniformity in two-dimensional samples. By analyzing the asymmetric longitudinal magnetoresistance under positive and negative <i> B</i>-fields, an analytical model based on a linear density gradient across the sample was deduced to quantitatively describe the asymmetry. Based on the theoretical model, a practical method was described which enabled one to experimentally measure the density gradient within a single sample. The method requires only measurements of longitudinal resistances <i>R_xx</i> and <i>R_yy</i> under both positive and negative <i>B</i>-fields, and equations have been provided to extract both the angle and the magnitude of density gradients from the measured resistances. The method was demonstrated in a GaAs quantum well wafer at cryogenic temperatures and <i>n</i>-GaAs bulk-doped wafer at room temperature. In both systems, the density gradient vectors extracted with our method matched well with the interpolated density gradient vectors estimated from actual density distribution maps as a base comparison set, suggesting that our method can be a universal extension of the vdP method to extract density gradients in various systems. The method also allows one to uncover the true local longitudinal resistivity &rho;<i>_xx</i> at the center of the sample, which the conventional vdP method cannot describe in the presence of non-uniform densities. The ability to find &rho;<i>_xx</i> makes it possible to study interesting physics in semiconductors such as interaction-induced quantum corrections to resistivity and valley filtering in multi-valley systems. </p><p> To extend the vdP method to cases where ohmic contacts are not available, a capacitive contact technique was introduced which sends current and senses voltage capacitively. A capacitive contact is formed between the buried conducting layer and the contact metal which is simply evaporated onto the sample. Systematic studies of four-point measurements with ohmic and/or capacitive contacts were conducted on a test sample and a Hall bar sample to demonstrate the effectiveness of the capacitive contact method. With a pre-defined capacitive scaling factor &gamma; and a measurement frequency band (<i>f_L</i> &sim; <i> f_H</i>), it was shown that capacitive contacts could extract the same four-point resistance as ohmic contacts, establishing the validity of the capacitive contact technique. </p><p> Built on the idea of capacitive coupling with capacitive contacts, a contactless electrical characterization probe was proposed. On the probe head, there are two types of metal gates: depletion gates to define a test region and separate the contacts, and capacitive contacts to conduct four-point measurements. To characterize a piece or a region on a wafer hosting a buried conducting layer, one brings the probe onto the sample, conducts the electrical measurements with the capacitive contacts, and removes the probe. The sample remains untouched and can be reused. The contactless probe should provide a fast and nondestructive way of semiconductor characterization.</p>

<p> This work describes technical innovations to improve the data quality and volume for the Fast Plasma Investigation (FPI) on board the Magnetospheric Multiscale mission (MMS). A parametric study of wavelet compression has shown that plasma count data can be compressed to high compression ratios with a minimal effect on the integrated plasma moments. Different regions of the magnetosphere are analyzed for both electron and ion count data. The FPI trigger data, intended as a data ranking metric, has been adapted and corrected to a point where scientifically accurate pseudo moments can be generated and released to the research community, drastically increasing the availability of high time resolution data. This is possible due to a scaling system that tunes the dynamic range of the system per region, and the method of using a neural network to correct for exterior contamination effects, such as spacecraft potential. Finally, a map of detection angle bias has been generated that can be used to correct raw count for errors in look direction of incoming particles. This map was generated by statistically sampling particle flight paths through a charged spacecraft environment, validating against flight data. All three of these efforts lead toward the overarching goal of improving data quality and volume for the FPI suite, and future missions to come. </p><p>

<p> The operating temperature of energy conversion and electronic devices affects their efficiency and efficacy. In many devices, however, the reference values of the thermal properties of the materials used are no longer applicable due to processing techniques performed. This leads to challenges in thermal management and thermal engineering that demand accurate predictive tools and high fidelity measurements. The thermal conductivity of strained, nanostructured, and ultra-thin dielectrics are predicted computationally using solutions to the Boltzmann transport equation. Experimental measurements of thermal diffusivity are performed using transient grating spectroscopy.</p><p> The thermal conductivities of argon, modeled using the Lennard-Jones potential, and silicon, modeled using density functional theory, are predicted under compressive and tensile strain from lattice dynamics calculations. The thermal conductivity of silicon is found to be invariant with compression, a result that is in disagreement with previous computational efforts. This difference is attributed to the more accurate force constants calculated from density functional theory. The invariance is found to be a result of competing effects of increased phonon group velocities and decreased phonon lifetimes, demonstrating how the anharmonic contribution of the atomic potential can scale differently than the harmonic contribution.</p><p> Using three Monte Carlo techniques, the phonon-boundary scattering and the subsequent thermal conductivity reduction are predicted for nanoporous silicon thin films. The Monte Carlo techniques used are free path sampling, isotropic ray-tracing, and a new technique, modal ray-tracing. The thermal conductivity predictions from all three techniques are observed to be comparable to previous experimental measurements on nanoporous silicon films. The phonon mean free paths predicted from isotropic ray-tracing, however, are unphysical as compared to those predicted by free path sampling. Removing the isotropic assumption, leading to the formulation of modal ray-tracing, corrects the mean free path distribution. The effect of phonon line-of-sight is investigated in nanoporous silicon films using free path sampling. When the line-of-sight is cut off there is a distinct change in thermal conductivity versus porosity. By analyzing the free paths of an obstructed phonon mode, it is concluded that the trend change is due to a hard upper limit on the free paths that can exist due to the nanopore geometry in the material.</p><p> The transient grating technique is an optical contact-less laser based experiment for measuring the in-plane thermal diffusivity of thin films and membranes. The theory of operation and physical setup of a transient grating experiment is detailed. The procedure for extracting the thermal diffusivity from the raw experimental signal is improved upon by removing arbitrary user choice in the fitting parameters used and constructing a parameterless error minimizing procedure.</p><p> The thermal conductivity of ultra-thin argon films modeled with the Lennard-Jones potential is calculated from both the Monte Carlo free path sampling technique and from explicit reduced dimensionality lattice dynamics calculations. In these ultra-thin films, the phonon properties are altered in more than a perturbative manner, referred to as the confinement regime. The free path sampling technique, which is a perturbative method, is compared to a reduced dimensionality lattice dynamics calculation where the entire film thickness is taken as the unit cell. Divergence in thermal conductivity magnitude and trend is found at few unit cell thick argon films. Although the phonon group velocities and lifetimes are affected, it is found that alterations to the phonon density of states are the primary cause of the deviation in thermal conductivity in the confinement regime.</p><p>

All operational electronic equipment dissipates some amount of energy in the form of infrared radiation. Faulty electronic components on a printed circuit board can be categorized as hard (functional) or soft (latent functional). Hard faults are those which are detected during a conventional manufacturing electronic test process. Soft failures, in contrast, are those which are undetectable through conventional testing, but which manifest themselves after a product has been placed into service. Such field defective modules ultimately result in operational failure and subsequently enter a manufacturer's costly repair process. While thermal imaging systems are being used increasingly in the electronic equipment industry as a product-testing tool, applications have primarily been limited to product design or repair processes, with minimal use in a volume manufacturing environment. Use of thermal imaging systems in such an environment has mostly been limited to low-volume products or random screening of high-volume products. Thermal measurements taken in a manufacturing environment are often taken manually, thus defeating their capability of rapid data acquisition and constraining their full potential in a high-volume manufacturing process. Integration of a thermal measurement system with automated testing equipment is essential for optimal use of expensive infrared measurement tools in a high-volume manufacturing environment. However, such a marriage presents problems with respect to both existing manufacturing test processes and infrared measurement techniques. Methods are presented in this dissertation to test automatically for latent faults, those which elude detection during conventional electronic testing, on printed circuit boards. These methods are intended for implementation in a volume manufacturing environment and involve the application of infrared imaging tools. Successful incorporation of infrared testing into existing test processes requires that: PASS/FAIL criteria be established; a procedure for dealing with variable radiation heat transfer properties across a printed circuit board be developed; and a thermally-controlled enclosure in which testing is performed be provided. These tasks are addressed and positive results are presented. Testing procedures and software developed to perform analyses are described. The feasibility of an infrared test process is demonstrated. A description of acquired experimental data, results, and analyses designed to verify measurement and fault analysis techniques are also presented. There are a number of phenomena which are known to contribute undesirably, and often unpredictably, to results. Methods for reducing random error in results and suggestions for establishing PASS/FAIL criteria and improving measurement techniques are addressed.