Focused Ion Beam (FIB) technology is a versatile tool that can be applied in many fields to great effect, including semiconductor device prototyping, Transmission Electron Microscopy (TEM) sample preparation, and nanoscale tomography. Developments in FIB technology, including the availability of alternative ion sources and improvements in automation capacity, make FIB an increasingly attractive option for many tasks. In this thesis, FIB systems are applied to photonic device fabrication and modification, semiconductor reverse engineering, and the production of structures for the study of nanoscale radiative heat transfer. Optical facets on silicon nitride waveguides were produced with plasma FIB (PFIB) and showed an improvement of 3 ± 0.9 dB over reactive ion etched (RIE) facets. This process was then automated and is capable of producing a facet every 30 seconds with minimal oversight. PFIB was then employed to develop a method for achieving local backside circuit access for circuit editing, creating local trenches with flat bases of 200 x 200 μm. Gas assisted etching using xenon difluoride was then used in order to accelerate the etch process. Finally, several varieties of nanogap structure were fabricated on devices capable of sustaining temperature gradients, achieving a minimum gap size with PFIB of 60 nm. / Thesis / Master of Applied Science (MASc)

Terahertz region in the electromagnetic spectrum is the region between Infrared and Microwave. As the Terahertz region has both wave and particle nature, it is difficult to make a room temperature, fast, and sensitive detector in this region. In this work, we fabricated a Palladium based IR detector and a CNT based THz bolometer. In Chapter 1, I give a brief introduction of the Terahertz region, the detectors already available in the market and different techniques I can use to test my detector. In Chapter 2, I explain about the Palladium IR bolometer, the fabrication technique I have used, and then we discuss the performance of the detector. In Chapter 3, I explained about the Roll to Roll based THz bolometer, its working and fabrication techniques, and at the end we discussed its performance.

yes / The aim of the experiment reported here was to investigate the processes underlying the construction of truthful and deliberately fabricated memories. Properties of memories created to be intentionally false (fabricated memories) were compared to properties of memories believed to be true (true memories). Participants recalled and then wrote or spoke true memories and fabricated memories of everyday events. It was found that true memories were reliably more vivid than fabricated memories and were nearly always recalled from a first-person perspective. In contrast, fabricated differed from true memories in that they were judged to be reliably older, were more frequently recalled from a third-person perspective, and linguistic analysis revealed that they required more cognitive effort to generate. No notable differences were found across modality of reporting. Finally, it was found that intentionally fabricated memories were created by recalling and then “editing” true memories. Overall, these findings show that true and fabricated memories systematically differ, despite the fact that both are based on true memories.

Consumer additive manufacturing (3D printing) has rapidly grown over the last decade. While the technology for the most common type, Fused Filament Fabrication (FFF), has systematically improved and sales have increased, fundamentally, the capabilities of the machines have remained the same. FFF printers are still limited to depositing layers onto a flat build plate. This makes it difficult to combine consumer AM with other objects. While consumer AM promises to allow us to customize our world, the reality has fallen short. The ability to directly modify existing objects presents numerous possibilities to the consumer: personalization, adding functionality, improving functionality, repair, and novel multi-material manufacturing processes. Indeed, similar goals for industrial manufacturing drove the research and development of technologies like direct write and directed energy deposition which can deposit layers onto uneven surfaces. Replicating these capabilities on consumer 3-axis FFF machines is difficult mainly due to issues with reliability, repeatability, and quality. This thesis proposes, demonstrates, and tests a method for scanning and printing dimensionally-accurate (unwarped) digital forms onto physical objects using a modified consumer-grade 3D printer. It then provides an analysis of the machine design considerations and critical process parameters. / Master of Science / Consumer additive manufacturing (3D printing) has rapidly grown over the last decade. While the technology for the most common type, Fused Filament Fabrication (FFF), has systematically improved and sales have increased, fundamentally, the capabilities of the machines have remained the same. FFF printers are still limited to depositing layers onto a flat build plate. This makes it difficult to combine consumer AM with other objects. While consumer AM promises to allow us to customize our world, the reality has fallen short. The ability to directly modify existing objects presents numerous possibilities to the consumer: personalization, adding functionality, improving functionality, repair, and novel multi-material manufacturing processes. Indeed, similar goals for industrial manufacturing drove the research and development of technologies like direct write and directed energy deposition which can deposit layers onto uneven surfaces. Replicating these capabilities on consumer 3-axis FFF machines is difficult mainly due to issues with reliability, repeatability, and quality. This thesis proposes, demonstrates, and tests a method for scanning and printing dimensionally-accurate (unwarped) digital forms onto physical objects using a modified consumer-grade 3D printer. It then provides an analysis of the machine design considerations and critical process parameters.

More efficient semiconductor lasers will be needed in tomorrow's applications. These lasers can only be realized through the application of new device processing techniques, designed to restrict current, carrier, and/or photon flow through the lasing cavity. This work aims to evaluate a non-conventional stripe laser processing technique which has the potential for effective current and possibly carrier confinement at low cost. This technique, referred to as hydrogen passivation, involves exposing laser material to a low energy hydrogen plasma, causing hydrogen ions to bind to charged acceptor and donor atoms. Such binding compensates the electrical activity of these dopant atoms and thereby increases the resistance of the exposed material. Optical confinement can also be achieved (subsequent to hydrogenation) by using a simple wet-etching process to form a lateral waveguide. Stripe lasers fabricated via hydrogen passivation have been demonstrated previously; however, the benefits of this method have not been fully explored or characterized. Our work aims to quantify the degree of current and carrier confinement provided by this technique. The cleaved cavity method of analysis is used to extract laser parameters via direct measurement. These parameters are then compared against those obtained from more conventional stripe lasers to identify improvements that have accrued from using hydrogen passivation. / Master of Science

This thesis details several modifications to the mechanical design of the Orthotic Lower Limb Exoskeleton (OLL-E) that improve upon the functionality and manufacturability of parts and their assemblies. The changes made to these parts maintain or improve the factor of safety against yield and fatigue failure as compared to the original designs. Design changes are verified by FEA simulations and hand calculations. The changes included in this thesis also allowed parts that were previously difficult or impossible to manufacture using traditional methods to be made in house or outsourced to another machine shop. In addition to the mechanical design changes, this thesis also details the design and implementation of a six axis force-torque sensor built into the foot of OLL-E. The purpose of this sensor is to provide feedback to the central control system and allow OLL-E to be self-balancing. This foot sensor design is calibrated and initial results are discussed and shown to be favorable. / Master of Science / Recent developments in the fields of robotics and exoskeleton design have increased their feasibility for use in medical rehabilitation and mobility enhancement for persons with limited mobility. The Orthotic Lower Limb Exoskeleton (OLL-E) is an exoskeleton specifically designed for enhancing mobility by allowing users with lower limb disabilities such as spinal cord injuries or paraplegia to walk. The research detailed in this thesis explains the design and manufacturing processes used to make OLL-E as well as providing design details for a force sensor built into the exoskeleton foot. Before manufacturing could take place some parts needed to be redesigned and this thesis provides insight into the reasons for these changes. After the manufacturing and design process was completed the OLL-E was assembled and the project can now move forward with physical testing.

To support the large growth in wireless devices, such as personal data assistants (PDAs), wireless local area network (WLAN) enabled laptop computers, and intelligent transportation systems (ITS), the FCC allocated three high-frequency bands for unlicensed operation. Of particular interest is the 5-6 GHz Unlicensed National Information Infrastructure (UNII) band intended to support high-speed WLAN applications. The UNII band is further split into three smaller 100 MHz sub-bands: 5.15 - 5.25 GHz; 5.25-5.35 GHz; and 5.725-5.825 GHz. VCOs that can be switched between each of the three UNII sub-bands offer flexibility and optimum phase-locked loop (PLL) design versus non-switchable VCOs. This work presents switched-tank voltage controlled oscillators (VCOs) designed in Motorolaà ­s 0.18 à µm HIP6WRF BiCMOS process that could be used in multiband receivers covering the three UNII sub-bands. The first VCO was optimized for low power consumption. The VCO draws a total of 6.75 mA from a 1.8 V supply including buffer amplifiers. The VCO is designed with a switched-capacitor LC tank circuit that can switch to two center frequencies, 5.25 GHz and 5.775 GHz, with 200 MHz of varactor-supplied tuning range. The simulated output voltage swing is 2.0 V peak-to-peak and is kept constant between sub-bands by an active PMOS load integrated into the biasing circuitry. The second VCO was optimized for a high output voltage swing by replacing the current biasing circuit with a degenerating inductor. This design targeted three center frequencies, 5.2 GHz, 5.3 GHz, and 5.775 GHz, with 100 MHz of tuning range. This design has an output peak-to-peak voltage swing of 5.2 V but consumes an average of 16.5 mA from a 1.8 V supply. The two fabricated circuits exhibit tuning ranges similar to the simulated results; however, the center frequencies of each decrease due to interconnect parasitics there were unaccounted for in the designs. The measured center frequencies are 4.4 GHz and 5.37 GHz for the first design, and 4.4 GHz and 4.7 GHz for the second design (with one state inoperative due to a faulty switch). The phase noise of the fabricated VCO designs was limited primarily by the low quality factor (Q-factor) of the on-chip LC tank circuits. Oscillators referenced with high-Q off-chip components such as quartz crystal references and surface acoustic wave (SAW) resonators in a PLL can exhibit much improved performance; however, these off-chip components add packaging/assembly cost and higher bill of materials, impedance matching issues, and parasitics that can significantly affect performance for RF applications. Thus, there is tremendous incentive for integrating high-Q components on-chip with the eventual goal of consolidating all of the RF/analog/digital components onto a single wireless-enabled chip, commonly called RF system-on-a-chip (SoC). Microelectromechanical (MEM) resonators have received significant attention based on their ability to provide high on-chip Q-factors at RF frequencies using fabrication techniques that are compatible with modern IC processes. MEM resonators transduce electrical signals into extremely low-loss mechanical vibration and vice versa. Consequently, this thesis also describes the modeling, simulation, and fabrication of contour-mode disk-shaped MEM resonators. This resonator geometry is capable of providing high-Q oscillation at frequencies exceeding 1 GHz at sizes easily within the limits of modern photolithography techniques. Finite element analysis is used to predict the frequency response of disk resonators under various operating conditions and to determine variables that are most critical to the resonator design. A silicon-on-insulator (SOI) fabrication process for constructing the disk is also discussed. Finally, the possible future integration of MEM resonators with multiband VCOs in a common IC process is proposed. / Master of Science

Yes / Fabrication of extracellular matrix (ECM)-like scaffolds (in terms of structural-functional) is the main challenge in skin tissue engineering. Herein, inspired by macromolecular components of ECM, a novel hybrid scaffold suggested which includes silk/hyaluronan (SF/HA) bio-complex modified by PCP: [polyethylene glycol/chitosan/poly(ɛ-caprolactone)] copolymer containing collagen to differentiate human-adipose-derived stem cells into keratinocytes. In followed by, different weight ratios (wt%) of SF/HA (S1:100/0, S2:80/20, S3:50/50) were applied to study the role of SF/HA in the improvement of physicochemical and biological functions of scaffolds. Notably, the combination of electrospinning-like and freeze-drying methods was also utilized as a new method to create a coherent 3D-network. The results indicated this novel technique was led to ~8% improvement of the scaffold's ductility and ~17% decrease in mean pore diameter, compared to the freeze-drying method. Moreover, the increase of HA (>20wt%) increased porosity to 99%, however, higher tensile strength, modulus, and water absorption% were related to S2 (38.1, 0.32 MPa, 75.3%). More expression of keratinocytes along with growth pattern similar to skin was also observed on S2. This study showed control of HA content creates a microporous-environment with proper modulus and swelling%, although, the role of collagen/PCP as base biocomposite and fabrication technique was undeniable on the inductive signaling of cells. Such a scaffold can mimic skin properties and act as the growth factor through inducing keratinocytes differentiation.

Filament-based material extrusion additive manufacturing (MEAM) is an established technique in additive manufacturing (AM). However, semicrystalline polymers, such as polypropylene (PP), have limited commercial use in MEAM processes in the past due to their rapid crystallization kinetics and the subsequent effect on the integrity of the generated structures. The rapid crystallization of PP can be controlled by formulating blends of PP with hydrocarbon resins to enable longer re-entanglement times for interlayer adhesion. While the topic of formulating PP blends/composites with other materials to improve the printability has been investigated, variation in properties of commercial PP grades, of similar molecular weight (MW) and molecular weight distribution (MWD), on printability is still to be investigated. Those commercial PP grades can have wide variation in properties such as Melt Flow Index (MFI), additive content, and polymer architecture which can impact material properties relevant to printability. To investigate the effect of properties of commercial PP on their printability and mechanical performance, different commercial PP grades, with different properties, are blended with a fixed loading of hydrogenated resins, and the consequent effects on the mechanical properties of MEAM generated PP structures are studied via mechanical analysis. Tensile strength and the extent of interlayer adhesion in the 3D printed blends are characterized through rheological measurements. These measurements emphasize the importance of the relative location of the storage/loss modulus crossover point via small oscillatory frequency sweeps. We specifically show that a relatively higher crossover frequency will correlate with improved interlayer adhesion and reduced warpage in printed structures. However, this improvement is accompanied by a tradeoff, resulting in inferior tensile strength and an increased degree of print orientation anisotropy. / Master of Science / Additive Manufacturing (AM), commonly known as 3D printing, is a transformative technology with high potential to revolutionize the manufacturing landscape. Polymers are widely used in AM for various applications. As a result, extensive research is conducted to enhance the printability and properties of printed polymer structures. Polypropylene (PP) exhibits desirable mechanical, optical, and chemical properties that make its use in AM attractive. Despite this potential, optimizing the use of PP in 3D printing remains challenging. Consequently, extensive research is underway to improve the printability of PP. However, the effects of including additives to enhance the properties of commercial PP grades are often overlooked. We demonstrate that the choice of commercial PP grade is crucial to the mechanical and structural properties of structures generated via AM. This was established by developing a systematic experimental procedure to assess the printability of various PP grades and to measure their key mechanical and structural properties.

Yes / Designing and manufacturing functional parts with enhanced mechanical property is a major goal of fused filament fabrication (FFF) for polymeric elastomers, which exhibits major advantages in producing such parts with a range of structures. But the unsatisfactory mechanical performance constrains greatly its real application and there is yet no consensus in the mechanical characterization of printed samples. This work takes the nozzle height as the considered factor and tests the tensile property of FFF-printed thermoplastic polyurethane (TPU). Rheological property of the TPU melt, represented here by die swell behavior and shear viscosity, were measured initially to obtain a preliminary assessment of the material suitability and an optimization of melt extrusion conditions for FFF processing. Then correlation between the cross-section profile of deposited bead and the tensile performance of printed sample were evaluated. Both the shape of deposited bead and the bonding strength of two adjacent beads are emphasized when explaining the measured tensile strength. The significance of molecular permeation efficiency at bead-bead interfaces, and bonding-releasing patterns between adjacent beads to the tensile failure of printed objects is discussed. / The support provided by China Scholarship Council (CSC, 201806465028) for Xiang Lin during his academic visit in University of Bradford is acknowledged.