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<p>Silicon-based dielectric thin films including amorphous hydrogenated aluminium-doped silicon oxides (<em>a-</em>SiAl_xO_y:H), amorphous hydrogenated silicon nitrides (<em>a-</em>SiN_x:H), and amorphous hydrogenated silicon carbides (<em>a-</em>SiC_x:H) were deposited by remote plasma chemical vapour deposition (RPECVD) techniques including electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR-PECVD) and inductively-coupled-plasma chemical vapour deposition (ICP-CVD) on silicon (Si) wafers, soda-lime glass microscope slides, and glassy carbon (C) plates. Aluminium (Al) in the SiAlO films was incorporated by way of a metalorganic Al(TMHD)₃ precursor.</p> <p>Thickness, refractive index, and growth rate of the films were measured using variable angle spectroscopic ellipsometry (VASE). Film composition was measured using energy dispersive X-ray spectroscopy (EDX) for the SiAlO films and Rutherford backscattering spectrometry (RBS) for the SiC_x films. Elastic modulus and hardness of the SiAlO and SiC_x films were measured using nanoindentation and their adhesion was characterized via progressive load scratch testing.</p> <p>All films were observed to be optically transparent at near-IR and red wavelengths with many SiN_x and SiC_x films exhibiting significant optical absorption above 2.25eV. Modification of a previously developed deposition recipe produced doubled growth rates in SiN_x and SiC_xfilms. SiAlO films were produced with up to 1.6±0.1at% aluninium (Al) incorporation, while SiC_x films with composition ranging from SiC_0.25:H to SiC₂:H could be produced depending on the growth gas flow ratios. SiAlO films exhibited hardness and reduced modulus (<em>H</em> and <em>E</em>) up to 8.2±0.4 and 75±2GPa, respectively; <em>H </em>and <em>E</em> for the SiC_xfilmsreached 11.9±0.2 and 87±3 GPa. Initially, adhesion to Si wafers was extremely poor with films delaminating at loads of 1.5±0.3N when scratched with a 3/16” alumina (Al₂O₃) sphere; implementation of a rigorous pre-deposition surface cleaning procedure produced films showing only cracking and no delamination up to 30N loads vs. a 200μm radius Rockwell C diamond stylus.</p> / Master of Applied Science (MASc)

Frequency multiplication is an effect that arises in electronic components that exhibit a non-linear response to electromagnetic stimuli. Barriers to achieving very high frequency response from electronic devices are the device capacitance and other parasitic effects such as resistances that arise from the device geometry and are in general a function of the size of the device. In general, smaller device geometries and features lead to a faster response to electromagnetic stimuli. It was posited that the small size of the silicon nanowires (SiNWs) would lead to small device capacitance and spreading resistance, thus making the silicon nanowires useful in generating microwave and terahertz radiation by frequency multiplication. To verify this hypothesis, silicon nanowires based devices were fabricated and investigated using two experimental setups. The setups were designed to allow the investigation of the nanowire based devices at low frequencies and at high frequencies. Both setups consisted of an RF/microwave source, filters, waveguide, and a spectrum analyzer. They also allowed the characterization of the samples with a semiconductor parameter analyzer. The first step in the investigation of the SiNW devices was to install them in the waveguides and perform Current-Voltage (I-V) sweeps using the semiconductor parameter analyzer. The devices that exhibited the non-linear I-V characteristics typical of diodes were further investigated by first exposing them to 70MHz and 500MHz frequencies in the low frequency setup and then to 50GHz microwaves in the high frequency setup. The response of the devices was captured with a spectrum analyzer. The results demonstrate that the non-linear effect of frequency multiplication is present in nanowire devices from DC to 100GHz. The HF setup provides a platform that with an appropriate detector can be used to detect harmonics of the SiNWs in sub-millimeter/THz region of the electromagnetic spectrum.

Graphene materials, exhibiting outstanding mechanical properties, are excellent candidates as reinforcement in high-performance polymer nanocomposites. In this dissertation, advanced atomic force microscopy (AFM) techniques are applied to study the nanomechanics of graphene/polymer nanocomposites, specifically the graphene/polymer interfacial strength and the stress transfer at the interface.;Two novel methods to directly characterize the interfacial strength between individual graphene sheets and polymers using AFM are presented and applied to a series of polymers and graphene sheets. The interfacial strength of graphene/polymer varies greatly for different combinations. The strongest interaction is found between graphene oxide (GO) and polyvinyl alcohol (PVA), a strongly polar, water-based polymer. On the other hand, polystyrene, a non polar polymer, has the weakest interaction with GO. The interfacial bond strength is attributed to hydrogen bonding and physical adsorption.;Further, the stress transfer in GO/PVA nanocomposites is studied quantitatively by monitoring the strain in individual GO sheet inside the polymer via AFM and Raman spectroscopy. For the first time, the strains of individual GO sheets in nanocomposites are imaged and quantified as a function of the applied external strains. The matrix strain is directly transferred to GO sheets for strains up to 8%. at higher strain levels, the onset of the nanocomposite failure and a stick-slip behavior is observed. This study reveals that GO is superior to pure graphene as reinforcement in nanocomposites. These results also imply the potential to make a new generation of nanocomposites with exceptional high strength and toughness.;In the second part of this dissertation, AFM is used to study the structure of silk proteins and the morphology of spider silks. For the first time, shear-induced self-assembly of native silk fibroin is observed. The morphology of the Brown Recluse spider silk is investigated and a novel silk/GO nanocomposite is proposed.;Finally, the growth, capacitance and frequency response of vertically oriented graphene sheets prepared by radio frequency plasma-enhanced chemical vapor deposition and used in electric double layer capacitors (EDLC) are presented. These capacitors exhibit the highest frequency response observed, to date, for carbon based materials, providing EDLC suitable for AC filtering. The results also suggest mechanisms other than surface area are operative in the double layer charge storage, such as a stronger polarization from graphene edges and vacancies.

In modern agriculture, nanotechnology has been at the forefront of agrochemical product innovation. For crop protection, researchers have turned to nano-zinc oxide (nano-ZnO) products that could potentially serve as an alternative to copper-based pesticides while mitigating micronutrient Zn deficiency. In this thesis, Zinkicide®, a nano-ZnO (4.5% Zn) based agriculture-grade product formulation has been investigated for their potential use as a broad-spectrum bactericide with systemic activity. Initial studies showed that Zinkicide® exhibits phytotoxicity to susceptible plants and experiences limited rainfastness. It is hypothesized that a suitable spray adjuvant will improve rainfastness and zinc absorption without compromising the antimicrobial efficacy. To test these hypotheses, the effect of three commercially available spray adjuvants – FitoFix®, Photon®, and AgriOil® – on Zinkicide®'s physico-chemical properties including wettability, zinc mobility and rainfastness were evaluated using citrus plants. Effects of adjuvant on Zinkicide® antimicrobial properties were also examined. Characterization results indicated that the composition of spray adjuvants has minimal effect on the deposition pattern (coffee ring effect) of Zinkicide® on glass and almost no effect on citrus leaf substrates. The wettability of Zinkicide® was slightly altered by the addition of adjuvants when tested on both substrates. FTIR data indicates that the adjuvants do not chemically interact with Zinkicide®. The effect of spray adjuvants on Zinkicide® antimicrobial properties were investigated using two model pathogens, Xanthamonas alfalfae and Pseudomonas syringae. The results suggest that the addition of adjuvants had no noticeable effect on the antimicrobial properties of Zinkicide®. The zinc in-planta mobility and rainfastness studies showed that the spray adjuvants have no observable effect on these properties. The above research findings could help advance Zinkicide® research in finding other potential adjuvant candidates in tank-mix settings.

<p>A non-contact on-site surface roughness measurement method was investigated in experimental and simulation approaches. The resolution of the vertical surface roughness was obtained at 20 nm by using self-interference theory. Various surface roughness measurement techniques, such as mechanical stylus, AFM and Michelson interferometer, were employed for different roughness samples. The novelty of this study was to measure the surface roughness on a rotating sample. For each sample with different step height, corresponding intensity distribution data was obtained and analyzed. The fringe visibility ratio resulted in a curve that is related to the step height, which represents the roughness. The results from simulations for all samples were compared with experimental data. Good agreements were obtained for the studied conditions.</p> / Master of Applied Science (MASc)

<p>The aim of third-generation photovoltaics (PV) is ultimately to achieve low-cost, high-efficiency devices. This work focused on a third-generation PV concept known as down-shifting, which is the conversion of high-energy photons into low-energy photons which are more useful for a typical solar cell. Silicon nanocrystals (Si-NCs) fabricated using electron-cyclotron resonance plasma-enhanced chemical vapour deposition (ECR-PECVD) were studied as a down-shifting material for single-junction silicon cells. A calibration was done to determine optimal deposition parameters for Si-NC formation. An experiment was then done to determine the effect of film thickness on emission, optical properties, and photoluminescence quantum efficiencies.</p> <p>Photoluminescence (PL) peaks varied depending on the stoichiometry of the films, ranging from approximately 790 nm to 850 nm. Variable-angle spectroscopic ellipsometry was used to determine the optical constants of the Si-NC films. The extinction coefficients indicated strong absorption below 500 nm, ideal for a down-shifting material. Transmission Electron Microscopy (TEM) was used to determine the size, density, and distribution of Si-NCs in two of the films. Si-NCs were seen to have an average diameter of approximately 4 nm, with larger nanocrystals more common near the surface of the film. A density of approximately 10⁵ nanocrystals per cubic micron was approximated from one of the TEM samples.</p> <p>The design and implementation of a PL quantum efficiency measurement system was achieved, using an integrating sphere to measure the absolute efficiency of Si-NC emission. Internal quantum efficiencies (IQE) as high as 1.84% and external quantum efficiencies (EQE) of up to 0.19% were measured. The EQE was found to increase with thicker films due to more intense photoluminescence; however the IQE remained relatively independent of film thickness.</p> / Master of Applied Science (MASc)

<p>InP nanowires with short InAs segments were grown on InP (111)B substrates by Au assisted vapour-liquid-solid growth in a gas source molecular beam epitaxy system. Nanowire crystal structure and morphology were investigated by transmission electron microscopy as a function of temperature, growth rate, and V/III flux ratio. At 370C predominantly kinked nanowires with random morphology and low areal density were observed with a rough parasitic 2D film. At 440C, nanowire density was also reduced but the 2D film growth was smoother and nanowires grew straight without kinking. An optimum temperature of 400C maximized areal density with uniform nanowire morphology. At the optimum temperature of 400C, an increase in V/III flux ratio changed the nanowire morphology from rod-shaped to pencil like indicating increased radial growth. Growth rate did not affect the crystal structure of InP nanowires. For InAs nanowires, changing the growth rate from 1 to 0.5 μm/hr reduced the presence of stacking faults to as low as one per nanowire. Short InAs segments in InP nanowires were found to grow through two mechanisms for nanowires of length L and diameter D. The first mechanism described the supply of In to the growth front via purging of In from the Au droplet where L was proportional to D. The second mechanism involved direct deposition of adatoms on the nanowire sidewall and subsequent diffusion to the growth front where L was proportional to 1/D. For intermediate growth durations, a transition between these two mechanisms was observed. For InP and InAs nanowires, the growth mode was varied from axial to radial through the inclusion of Al to form a core shell structure. Al_xIn_1-xAs(P) shells were grown on InAs cores with Al alloy fractions between 0.53 and 0.2. These nanowires were examined by transmission electron microscopy and it was found, for all values of x in InAs-Al_xIn_1-xP structures, that relaxation had occurred through the introduction of dislocations. For InAs-Al_xIn_1-xAs structures, all values except x=0.2 had relaxed through dislocation formation. A critical thickness model was developed to determine the core-shell coherency limits which confirmed the experimental observation of strain relaxation. The effects of passivation on the electronic transport and the optical properties were examined as a function of structural core-shell passivation and chemical passivation. The mechanisms for the observed improvement in mobility for core-shell versus bare InAs nanowires was due to the reduction in ionized impurity scattering from surface states. Similarly an increase in photoluminescence intensity after ammonium sulfide passivation was explained by the reduction of donor type surface states.</p> / Doctor of Philosophy (PhD)

<p>The solid state dewetting characteristics of thin gold films sputtered onto (111) MgAl₂O₄ substrates were investigated. Prior research done on this system reported discovering the self-assembly of intricately shaped nanostructures, consisting of a faceted sphere lying above a truncated triangular pyramid, formed by applying a specific two stage heating profile. The current work was done to provide deeper insight on the odd self-assembly observed in this system. The results indicate that the intricate structures are not purely gold self-assemblies, but in fact consist of three distinct materials: a single crystal or polycrystalline gold faceted sphere, separated by an interfacial boundary layer, from above a crystalline MgAl₂O₄ necking structure that spontaneously developed from the initially flat substrate. The boundary separating these two assemblies is confined within a thin, sharp region of a third material consisting of Au and O elements. The composition and crystalline nature of the individual nanostructures were studied using high angle annular dark-field imaging, energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy employed by a high resolution transmission electron microscope. Two-dimensional X-ray diffraction texture analysis revealed that the gold nanoparticles are crystalline, with majority of the maximum intensity signal corresponding to the epitaxial alignment of the gold nanoparticles with the substrate. The MgAl₂O₄ necking structures were found to be sensitive to both the annealing profile, and the thickness of the gold film, which influenced the distinguishable presence, size, and footprint of the MgAl₂O₄ nanostructures. Atomic force microscopy and scanning electron microscopy results were consistent with the gold overlayer playing an essential role in the self-assembly of MgAl₂O₄ nanostructures. While the fundamental mechanisms that govern this phenomenon are not entirely clear, the presented results do provide insight into the role of interfaces in heteroepitaxial systems, especially the self-assembly of crystalline nanostructures from a previously stable substrate.</p> / Master of Applied Science (MASc)

<p>In this thesis, a modern transmission electron microscope is used to perform high-resolution electron energy loss studies of metallic nanostructures and carbon nanotubes.</p> <p>The remarkable optical properties of metallic nanostructures arise from the excita- tion of surface plasmons. With improved instrumentation, surface plasmon resonances are imaged in a variety of nanostructures, enabling a greater understanding of their behaviour in nanoscale systems. It is shown that surface plasmons set up multiple high order resonances in silver nanorods, and they freely propagate around sharp corners in silver nanowires. It is also demonstrated that silver nanorice structures resonate in a similar manner to nanorods, despite the high density of stacking faults in the structure. Finally, a complementary structural pair is found to resonate in a complementary fashion, in agreement with Babinet’s principle.</p> <p>Carbon nanotubes exhibit unique physicochemical properties that have led to their use in a variety of novel materials science applications. Despite rapid progress in the theoretical and experimental investigation of carbon nanotubes, techniques capable of studying the structural and electronic properties of individual tubes are limited. Here, it is demonstrated that the spectral signature of carbon can be used to identify the electronic character of individual single-walled carbon nanotubes. In addition, a new technique is used to map bonding anisotropy in a multi-walled carbon nanotube.</p> <p>Also presented in this thesis is the design and construction of a unique laser-TEM system. Early results from the system include in-situ measurements of laser-induced structural and electronic distortions in individual carbon nanotubes.</p> / Doctor of Philosophy (PhD)