Silicon Carbide has been a semiconductor material of interest as a high power and temperature replacement for Silicon (Si) in harsh environments due to the higher thermal conductivity and chemical stability of SiC. The cost, however, to produce this material is quite high. There are also defects in the substrate material (SiC) that penetrate into the active devices layers which are known device killers. Silicon is a material that provides a low cost substrate material for epitaxial growth and does not contain the defects that SiC substrates have. However, the large (~22%) lattice mismatch between Si and SiC creates dislocations at the SiC/Si interface and defects in the SiC epitaxial layer. These defects result in high leakage currents in 3C-SiC/Si devices. The main focus of the this research was to reduce or eliminate these defects using novel Si substrates. First a 3C-SiC on Si baseline process was developed under atmospheric pressure conditions consisting of 3 steps - an in-situ hydrogen etch to remove the native oxide, a carbonization step to convert the Si surface to SiC, and finally a growth step to thicken the SiC layer to the desired value. This process was then modified to establish a high-quality, low-pressure 3C-SiC CVD growth process. This LPCVD process was then used to grow 3C-SiC on numerous novel Si substrates, including porous Si, porous 3C-SiC "free-standing" substrates and SOI substrates which consisted on thin Si films bonded to poly-crystalline SiC plates. The results of these experiments are presented along with suggestions for future work so that device-grade films of 3C-SiC can be developed for various applications.

Metal oxide thin films are dynamic materials that have revolutionised the nature of semiconductor and electronic thin film devices. Recently, progress has stagnated in some aspects due to the increasingly complex deposition apparatus required, and the dearth of suitable precursor complexes of certain ???difficult??? metals. This thesis seeks to address both of these issues. The application of a precursor complex, Mg6(O2CNEt2)12 to the SSCVD of MgO thin films delivered the highest quality films ever reported with this technique. The resultant films were found to be of purely (111) orientation. Due to the nature of the precursor, the chemical reactions occurring at the surface during SSCVD growth result in a high growth rate, low flux environment and films of (111) orientation have been achieved without the amorphous underlayer. This finding has important implications for buffer layers in perovskite thin film devices. The unprecedented precursor chemistry has been used as a basis for the extremely high quality material produced, along with the unusual, yet beneficial structural morphology it possesses. A new range of barium complexes with single encapsulating ligands have been prepared for use in chemical vapour deposition (CVD) of BaTiO3 thin films. A novel pathway to an unprecedented class of barium carbamates is reported, and also new dianionic bis ??-ketoesterates and their barium, strontium, and calcium analogues were synthesised. High resolution mass spectrometry showed the barium bis ??-ketoesterate derivatives to be monomeric, and preliminary testing indicated some volatility in these species. Insights were gained into the likely successful pathways to building a volatile heterobimetallic precursor complex containing an alkaline earth metal. The knowledge of intimate mixing in heterobimetallic precursor complexes was extended by some novel chemistry to develop the first mixed Zn/Mg carbamato cluster complexes. These complexes were found to be excellent SSCVD precursors for ZnxMg1-xO thin films. Thin films were deposited with these precursors and exhibited a single preferred orientation, with a constant amount of magnesium throughout the bulk of the films. Investigation of the light emission properties of the films revealed significant improvements in the structural order commensurate with the incorporation of magnesium, and the formation of the ZnxMg1-xO alloy.

Metal oxide thin films are dynamic materials that have revolutionised the nature of semiconductor and electronic thin film devices. Recently, progress has stagnated in some aspects due to the increasingly complex deposition apparatus required, and the dearth of suitable precursor complexes of certain ???difficult??? metals. This thesis seeks to address both of these issues. The application of a precursor complex, Mg6(O2CNEt2)12 to the SSCVD of MgO thin films delivered the highest quality films ever reported with this technique. The resultant films were found to be of purely (111) orientation. Due to the nature of the precursor, the chemical reactions occurring at the surface during SSCVD growth result in a high growth rate, low flux environment and films of (111) orientation have been achieved without the amorphous underlayer. This finding has important implications for buffer layers in perovskite thin film devices. The unprecedented precursor chemistry has been used as a basis for the extremely high quality material produced, along with the unusual, yet beneficial structural morphology it possesses. A new range of barium complexes with single encapsulating ligands have been prepared for use in chemical vapour deposition (CVD) of BaTiO3 thin films. A novel pathway to an unprecedented class of barium carbamates is reported, and also new dianionic bis ??-ketoesterates and their barium, strontium, and calcium analogues were synthesised. High resolution mass spectrometry showed the barium bis ??-ketoesterate derivatives to be monomeric, and preliminary testing indicated some volatility in these species. Insights were gained into the likely successful pathways to building a volatile heterobimetallic precursor complex containing an alkaline earth metal. The knowledge of intimate mixing in heterobimetallic precursor complexes was extended by some novel chemistry to develop the first mixed Zn/Mg carbamato cluster complexes. These complexes were found to be excellent SSCVD precursors for ZnxMg1-xO thin films. Thin films were deposited with these precursors and exhibited a single preferred orientation, with a constant amount of magnesium throughout the bulk of the films. Investigation of the light emission properties of the films revealed significant improvements in the structural order commensurate with the incorporation of magnesium, and the formation of the ZnxMg1-xO alloy.

Metal oxide thin films are dynamic materials that have revolutionised the nature of semiconductor and electronic thin film devices. Recently, progress has stagnated in some aspects due to the increasingly complex deposition apparatus required, and the dearth of suitable precursor complexes of certain ???difficult??? metals. This thesis seeks to address both of these issues. The application of a precursor complex, Mg6(O2CNEt2)12 to the SSCVD of MgO thin films delivered the highest quality films ever reported with this technique. The resultant films were found to be of purely (111) orientation. Due to the nature of the precursor, the chemical reactions occurring at the surface during SSCVD growth result in a high growth rate, low flux environment and films of (111) orientation have been achieved without the amorphous underlayer. This finding has important implications for buffer layers in perovskite thin film devices. The unprecedented precursor chemistry has been used as a basis for the extremely high quality material produced, along with the unusual, yet beneficial structural morphology it possesses. A new range of barium complexes with single encapsulating ligands have been prepared for use in chemical vapour deposition (CVD) of BaTiO3 thin films. A novel pathway to an unprecedented class of barium carbamates is reported, and also new dianionic bis ??-ketoesterates and their barium, strontium, and calcium analogues were synthesised. High resolution mass spectrometry showed the barium bis ??-ketoesterate derivatives to be monomeric, and preliminary testing indicated some volatility in these species. Insights were gained into the likely successful pathways to building a volatile heterobimetallic precursor complex containing an alkaline earth metal. The knowledge of intimate mixing in heterobimetallic precursor complexes was extended by some novel chemistry to develop the first mixed Zn/Mg carbamato cluster complexes. These complexes were found to be excellent SSCVD precursors for ZnxMg1-xO thin films. Thin films were deposited with these precursors and exhibited a single preferred orientation, with a constant amount of magnesium throughout the bulk of the films. Investigation of the light emission properties of the films revealed significant improvements in the structural order commensurate with the incorporation of magnesium, and the formation of the ZnxMg1-xO alloy.

A study of the effect of catalyst properties on the synthesis of carbon nanotubes (CNTs) is done in this thesis. Three different metal alloy catalysts, Fe/Ti, Ni/Ti, Co/Ti, have been studied. Various atomic concentrations and thicknesses were cosputter deposited on clean Si wafers using AJA Orion 4 RF Magnetron sputter deposition tool at 5mtorr and 17��C, and the films were characterized using a scanning electron microscope, Energy-dispersive X-ray spectroscopy. All the alloys have been annealed at 650��C and 3 torr in an argon atmosphere at 100 SCCM, followed by ammonia gas plasma etch at different powers at 3 torr and 50 SCCM NH��� flow in a modified parallel plate RF chemical vapor deposition tool for 1 minute. The influence of plasma power, thickness of catalyst and concentration of Ti the secondary metal in the alloy composition, on the surface morphology of the catalyst are investigated by characterizing them with atomic force microscopy. The study has shown that the surface roughness is affected by Ti concentration, thickness and plasma power. The 35 W power NH��� plasma produced rougher surfaces when compared to the 75 W NH��� plasma. The result is interpreted as follows: ion bombardment leads to greater etching of the catalyst surface. Thus, plasma power must be optimized for catalyst thin film and etch time. The study has provided an in depth analysis and understanding of the various factors that influence catalyst surface morphology which can be applied into further study for optimizing parameters for synthesis of single walled CNTs. Following this, a study on catalysts for CNT synthesis was performed using Plasma enhanced chemical vapor deposition and characterized by scanning electron microscope. CNTs were synthesized on Ni, Ni-Ti, Co, Co-Ti and Fe catalyst. Ni, Ni-Ti catalyst produced forest like vertically aligned CNTs whereas Co, Co-Ti produced vertically aligned free standing CNTs. The growth was dense and uniform across the substrate. Initial growth runs on Fe, Fe-Ti alloy did not produce any CNTs until catalyst was restructured with a thicker Ti under layer after an investigation using Secondary ion mass spectrometry of suspected Fe catalyst poisoning due to reaction with Si substrate. A room temperature run was carried out on annealed and plasma etched Ni catalyst and no CNTs were produced indicating the importance of substrate temperature of CNTs. A deeper understanding of factors of influence on CNTs such as catalyst types, structure/morphology, and substrate temperature has been achieved with this study. / Graduation date: 2013

This research is aimed at synthesizing millimeter-scale carbon nanotube arrays (CNTA) by conventional chemical vapor deposition (CCVD) and water-assisted chemical vapor deposition (WACVD) methods, and exploring their application as catalyst supports for electrochemical supercapacitors. The growth mechanism and growth kinetics of CNTA under different conditions were systematically investigated to understand the relationship among physical characteristics of catalyst particles, growth parameters, and carbon nanotube (CNT) structures within CNTAs. Multiwalled CNT (MWCNT) array growth demonstrates lengthening and thickening stages in CCVD and WACVD. In CCVD, the lengthening and thickening were found to be competitive. By investigating catalyst particles after different pretreatment conditions, it has been found that inter-particle spacing plays a significant role in influencing CNTA height, CNT diameter and wall number. In WACVD, a long linear lengthening stage has been found. CNT wall number remains constant and catalysts preserve the activity in this stage, while MWCNTs thicken substantially and catalysts deactivate following the previously proposed radioactive decay model in the thickening stage of WACVD. Water was also shown to preserve the catalyst activity by significantly inhibiting catalyst-induced and gas phase-induced thickening processes in WACVD. Mn3O4 nanoparticles were successfully deposited and uniformly distributed within millimeter-long CNTAs by dip-casting method from non-aqueous solutions. After modification with Mn3O4 nanoparticles, CNTAs have been changed from hydrophobic to hydrophilic without their alignment and integrity being destroyed. The hydrophilic Mn3O4/CNTA composite electrodes present ideal capacitive behavior with high reversibility. This opens up a new route of utilizing ultra-long CNTAs, based on which a scalable and cost-effective method was developed to fabricate composite electrodes using millimeter-long CNTAs. To improve the performance of the composites, -MnO2 nanorods were anodically pulse-electrodeposited within hydrophilic 0.5 mm-thick Mn3O4 decorated CNTAs. The maximum gravimetric capacitance for the MnO2 nanorods/CNTA composite electrode was found to be 185 F/g, and that for -MnO2 nanorods was determined to be 221 F/g. After electrodeposition, the area-normalized capacitance and volumetric capacitance values were increased by a factor of 3, and an extremely high area-normalized capacitance of 1.80 F/cm2 was also achieved for the MnO2 nanorods/CNTA composite. / Materials Engineering

c-BN has been in focus for several years due to its interesting properties. The possibility for large area CVD is a requirement for the realization of these different properties in various applications. Unfortunately, there are at present severe problems in the CVD growth of c-BN. The purpose with this research project has been to theoretically investigate, using DFT calculations, the possibility for a layer-by-layer CVD growth of c-BN. It could be established that, PEALD, using a BF3-H2-NH3-F2 pulse cycle and a diamond substrate, is a promising method for deposition of c-BN films. The gaseous species will decompose in the plasma and form BFx, H, NHx, and F species (x = 0, 1, 2, 3). The H and F radicals will uphold the cubic structure by completely hydrogenate, or fluorinate, the growing surface. However, surface radical sites will appear during the growth process as a result of atomic H, or F, abstraction reactions. The addition of NHx growth species (x = 0, 1, 2) to B radical sites, and BFx growth species (x = 0, 1, 2) to N radical sites, will then result in a continuous growth of c-BN.

Piezoelectric actuators (PEA) hold the most promise for precision positioning applications due to their capability of producing extremely small displacements down to 10 pm (1 pm = 10-12 m) as well as their high stiffness and force output. The piezoelectric-driven stick-slip (PDSS) actuator, working on the friction-inertia concept, has the capacity of accomplishing an unlimited range of motion. It also holds the promises of simple configuration and low cost. On the other hand, the PDSS actuator has a relatively low efficiency and low loading capability, which greatly limits its applications. The purpose of this research is to improve the performance of the PDSS actuators by employing specially-designed working surfaces.<p> The working surfaces, referred as anisotropic friction (AF) surfaces in this study, can provide different friction forces depending on the direction of relative motion of the two surfaces, and are used in this research to accomplish the aforementioned purpose. To fabricate such surfaces, two nanostructure technologies are employed: hot filament chemical vapour deposition (HFCVD) and ion beam etching (IBE). The HFCVD is used to deposit diamond on silicon substrates; and the IBE is used to etch the diamond crystalloid with a certain angle with respect to the coating surface to obtain an unsymmetrical-triangle microstructure. <p> A PDSS actuator prototype containing the AF surfaces was developed in this study to verify the function of the AF surfaces and characterize the performance of PDSS actuators. The designed surfaces were mounted on the prototype; and the improvement in performance was characterized by conducting a set of experiments with both the normal isotropic friction (IF) surfaces and the AF surfaces, respectively. The results illustrate that the PDSS actuator with the AF surface has a higher efficiency and improved loading capability compared to the one with the IF surfaces.<p> A model was also developed to represent the displacement of the novel PDSS actuator. The dynamics of the PEA and the platform were approximated by using a second order dynamic system. The pre-sliding friction behaviour involved was investigated by modifying the LuGre friction model, in which six parameters (Note that three parameters are used in the LuGre model) were employed to represent the anisotropic friction. By combining the PEA mechanism model, the modified friction model, and the dynamics of end-effector, a model for the PDSS actuator with the AF surface was developed. The model with the identified parameters was simulated in MATLAB Simulink and the simulation results obtained were compared to the experimental results to verify the model. The comparison suggests that the model developed in this study is promising to represent the displacement of the novel PDSS actuators with AF surfaces.

The effect of annealing conditions on the microstructure evolution of CVD nickel was investigated systematically in the present study by differential scanning calorimetry, optical microscopy and transmission electron microscopy (TEM), upon both ex-situ and in-situ annealing. TEM observation revealed the as-deposited CVD nickel possessed a bi-modal grain structure, with large columnar grains embedded in nanocrystalline matrix. Ultrafine and nano growth twins were present as well as multiply twinned grains with five-fold symmetry. Microstructure observation upon annealing showed that grain growth did not occur until annealing at 400ºC. Detwinning was observed at 400ºC and higher temperatures. The ultrafine and nano twins tended to transform into dislocation cell structures and this phenomenon was driven by the excess free energy associated with the high density of grown-in twin boundaries. The five-fold twinned grains were found to be thermally stable up to 600ºC. The hardness was observed to decrease with increasing annealing temperature.

The effect of annealing conditions on the microstructure evolution of CVD nickel was investigated systematically in the present study by differential scanning calorimetry, optical microscopy and transmission electron microscopy (TEM), upon both ex-situ and in-situ annealing. TEM observation revealed the as-deposited CVD nickel possessed a bi-modal grain structure, with large columnar grains embedded in nanocrystalline matrix. Ultrafine and nano growth twins were present as well as multiply twinned grains with five-fold symmetry. Microstructure observation upon annealing showed that grain growth did not occur until annealing at 400ºC. Detwinning was observed at 400ºC and higher temperatures. The ultrafine and nano twins tended to transform into dislocation cell structures and this phenomenon was driven by the excess free energy associated with the high density of grown-in twin boundaries. The five-fold twinned grains were found to be thermally stable up to 600ºC. The hardness was observed to decrease with increasing annealing temperature.