Pax3 protein is initially expressed in the dermomyotome of embryonic somites, which gives rise to skeletal muscle. Following myogenesis, Pax3 expression is mostly down-regulated and becomes restricted to a few satellite cells (SCs) of select mature muscles. SCs are activated to form new myonuclei during muscle hypertrophy, regeneration and repair. Intrafusal fibers of muscle spindles are thought to persist in a comparatively immature state as, unlike extrafusal fibers, they maintain small diameters, developmental myosins, Myf5 expression and high SC concentrations. This thesis tests the hypotheses that Pax3 expression is preferentially maintained in SCs of adult skeletal muscle spindles and can be augmented under conditions of SC activation. To study Pax3 through development, immunohistochemical techniques were used to identify SCs by their Pax7 expression, and analyze the proportion of SCs and myonuclei (MN) expressing Pax3 in chicken anterior latissimus dorsi (ALD) muscle excised at 9, 30, 62, and 145 days post-hatch. To induce SC activation, tenotomy was performed on the right ALD muscle of 138-day post-hatch chicks to induce compensatory hypertrophy of the ipsilateral synergistic posterior latissimus dorsi (PLD) muscle. The PLD was analyzed seven days after ALD tenotomy using similar immunohistochemical techniques. This is the first study to show Pax3 expressing SCs within intrafusal fibers of muscle spindles. This thesis demonstrates that throughout development there is a higher percentage of Pax3 expressing SCs within intrafusal fibers of muscle spindles than the surrounding extrafusal fibers that compose the bulk of the muscle. It is also revealed that the proportion of the SC population expressing Pax3 declines with age in both intrafusal and extrafusal fibers. Compensatory hypertrophy of the PLD resulted in a greater percentage of Pax3 expressing SCs in intrafusal and extrafusal fibers than under control conditions. The percentage of SCs expressing Pax3 after PLD overload was similar to that seen in young control muscle. The percentage of Pax3 expressing MN also increased after muscle overload to levels seen in young muscle. A disproportionate decrease in the proportion of SCs expressing Pax3 during development, and a disproportionate increase in the percentage of Pax3 positive SCs as a result of experimentally induced muscle hypertrophy, suggests that Pax3 expression in maturing muscle may be more than just a developmental vestige. Pax3 may be a factor in the activation and differentiation of SCs in maturing muscle.

The atomic layer deposition (ALD) growth of titania thin films was studied for the infiltration of silica photonic crystals. Titania thin films were grown in a custom-built ALD reactor by the alternating pulsing and purging of TiCl4 and water vapor. The conformal nature of ALD growth makes it an ideal candidate for the infiltration of the complex opal structure. Titania is a high refractive index material, which makes it a popular material for use in photonic crystal (PC) applications. Photonic crystals are periodic dielectric structures that forbid the propagation of light in a certain wavelength range. This forbidden range is known as the photonic band gap (PBG). A refractive index contrast of at least 2.8 is required for a complete PBG in an inverted opal structure. Therefore, the rutile structure of titania is more desirable for use in PCs due to its higher index of refraction than the anatase or brookite structure. The growth mechanisms and film properties of the TiO2 thin films were studied. Investigation of the growth mechanisms revealed saturated growth rate conditions for multiple temperature regions. Film characterization techniques included XRD, SEM/EDS, XPS, AFM, reflectivity, and index of refraction measurements. Post growth heat treatment was performed to study the conversion from the as-deposited crystal structure to the rutile structure. After optimization of the deposition process, the infiltration of silica opals for PC applications was attempted. The filling fraction was optimized by increasing the pulse and purge lengths at a deposition temperature of 100oC. Although the silica opals were successfully infiltrated using ALD of TiO2, the long range order of the PC was destroyed after the heat treatment step required to achieve the high index rutile structure.

Previous studies on very high-cycle fatigue behavior of thin silicon films suggest a strong environmental dependence of the degradation mechanism, the precise nature of which is still subject to debate. In the present study, 2-micron-thick polycrystalline Si notched cantilever beam structures were used to investigate fatigue degradation in a high-temperature (80°C), high-humidity (90%RH) environment. The specimens were subjected to fully reversed sinusoidal loading at resonance (~40kHz) with stress amplitudes ranging from 1.46 to 1.6GPa, resulting in life-spans between 10⁶ and 10⁹ cycles. Comparison to a reference set of S-N data obtained at moderate environmental conditions (30°C and 50%RH) reveals a strong tendency for faster degradation with increasing temperature and humidity. The obtained damage accumulation rates in the 80°C, 90%RH environment exceed the reference by two orders of magnitude. Transmission electron microscopy (TEM) on vertical through-thickness slices reveals oxide thickening after cycling. The influence of ~20nm Al[subscript2]O₃ deposited on the surface of the fatigue specimens using Atomic Layer Deposition (ALD) technique was also studied. The presence of the alumina coating results in a higher fatigue resistance at 30°C and 50%RH, as well as a drastically different frequency evolution behavior. No oxide thickening was observed in the TEM for coated run-out specimens. A model is proposed to explain the different degradation behavior of the ALD-alumina coated samples. Thickened oxides after cycling appear consistent with the reaction-layer fatigue mechanism. Finite element modal analysis incorporating surface oxide layers and cracking was employed to relate the damage observed in TEM to the experimentally measured changes in resonant frequency. In conclusion, the reaction-layer mechanism seems capable of describing micron-scale polysilicon fatigue, even though the critical processes such as room-temperature, stress-assisted oxidation remain elusive.

System integration and miniaturization demands are driving integrated thin film capacitor technologies with ultra-high capacitance densities for power supply integrity and efficient power management. The emerging need for voltage conversion and noise-free power supply in bioelectronics and portable consumer products require ultra high-density capacitance of above 100 μF/cm2 with BDV 16-32 V ,independent capacitor array terminals and non-polar dielectrics. The aim of this research,therefore, is to explore a new silicon- compatible thin film nanoelectrode capacitor technology that can meet all these demands. The nanoelectrode capacitor paradigm has two unique advances. The first advance is to achieve ultra-high surface area thin film electrodes by sintering metallic particles directly on a silicon substrate at CMOS- compatible temperatures. The second advance of this study is to conformally- deposit medium permittivity dielectrics over such particulate nanoelectrodes using Atomic Layer Deposition (ALD) process. Thin film copper particle nanoelectrode with open-porous structure was achieved by choosing a suitable phosphate-ester dispersant, solvent and a sacrificial polymer for partial sintering of copper particles to provide a continuous high surface area electrode. Capacitors with conformal ALD alumina as the dielectric and Polyethylene dioxythiophene (PEDT) as the top electrode showed 30X enhancement in capacitance density for a 20-30 micron copper particulate bottom electrode and 150X enhancement of capacitance density for a 75 micron electrode. These samples were tested for their mechanical and electrical properties by using characterization techniques such as SEM, EDS, I-V and C-V plots. A capacitance density of 30 μF/cm2 was demonstrated using this approach. The technology is extensible to much higher capacitance densities with better porosity control, reduction in particle size and higher permittivity dielectrics.

ZnO nanostructures have been investigated for quite a long time. However, only recently they triggered much interest due to advances in materials synthesis and characterization, as well as emerging demand for new nanostructured materials in novel device implementations. A large part of the work was devoted to exploring new methodology for patterning growth sites and controlling nanowires morphology using the deposition methods that are compatible with integrated circuits (IC) processing. Microcontact printing was used to pattern the seeding layer, and, subsequently, ZnO nanowires through a resistless soft lithography process. When considering hydrothermal growth of ZnO nanowires in the framework of IC compatible techniques, it is favorable to keep the chemistry of the process constant, while tailoring morphological properties of ZnO nanowires through other means. Therefore, control over morphology of ZnO nanowires was realized by setting the physical properties of seeding layers. Atomic Layer Deposition (ALD) was used to deposit seeding layer required for hydrothermal growth and the effect of the physical properties of ALD thin films on resultant ZnO nanowires was studied. Opto-electrochemical properties of ZnO nanowires were studied in various electrolytes and performance of ZnO nanowires as an electrode material for multifunctional applications was investigated. Also, bulk nucleation and growth of novel aster-like nanostructures was investigated. These nanostructures may prove useful for creation of mechanically reinforced biocompatible polymers. Another key objective of the present work was to create strategies for controlled growth of ZnO nanowires on substrates previously unavailable for conventional hydrothermal growth of ZnO nanowires. The newly developed approach greatly facilitates growth of ZnO nanowires in confined microstructures, which greatly enhances the possibilities for the usage of ZnO nanowires in applications where they act as a porous electrode. These novel techniques open wide possibilities for improving performance of devices such as dye sensitized solar cells or supercapacitors.

This poster was presented in the Materials for Advanced Metallization (MAM) 2014 Conference in Chemnitz, Germany. Abstract: Atomic Layer Deposition (ALD) has emerged as an ubiquitous method for the deposition of conformal and homogeneous ultra-thin films on complex topographies and large substrates in microelectronics. Electrochemical deposition (ECD) is the first choice for the deposition of copper (Cu) into the trenches and vias of the interconnect system for ULSI circuits. The ECD of Cu necessitates an electrically conductive seed layer for filling the interconnect structures. ALD is now considered as a solution for conformal deposition of Cu seed layers on very high aspect ratio (AR) structures also for technology nodes below 20 nm, since physical vapor deposition is not applicable for structures with high AR. Cu seed layer deposition by the reduction of Cu2O, which has been deposited from the Cu(I) β-diketonate precursor [(nBu3P)2Cu(acac)], has been successfully carried out on different substrates like Ta, TaN, SiO2, and Ru [1, 2]. However, still many questions are unanswered regarding the underlying surface chemistry of the precursor on many substrates, leading to different growth modes during ALD. In this work, the surface chemistry of [(nBu3P)2Cu(acac)] on SiO2 substrate is investigated by in-situ X-ray photoelectron spectroscopy (XPS), reporting vital information about the oxidation state and the atomic concentration after chemisorption on the substrates kept at different temperatures. The aim of the investigation is to understand the stepwise change in the precursor oxidation state with increasing substrate temperature and to identify the temperature limit for the thermal ALD with this Cu precursor on SiO2. For the experiments, the Cu precursor was evaporated on SiO2 substrates kept at temperatures between 22 °C and 300 °C. The measured C/Cu and P/Cu concentration indicated that most of the nBu3P ligands were released either in the gas phase or during adsorption (Fig. 1a). No disproportionation was observed for the Cu precursor in the temperature range between 22 °C and 145 °C. Similarly, in this temperature range the Auger parameter calculated from Cu 2p3/2 and Cu L3VV spectra was found to be 360.0±0.2 eV, comparable to Cu(I) oxidation state [3]. However, disproportionation of the Cu precursor was observed above 200 °C, since C/Cu concentration ratio decreased and substantial metallic Cu was present on the substrate. Hence, 145 °C is the temperature limit for the ALD of Cu2O from this precursor, as the precursor must not alter its chemical state after chemisorption on the substrate. 500 ALD cycles with the probed Cu precursor and wet O2 as co reactant were carried out on SiO2 at 145 °C. After ALD, in situ XPS analysis confirmed the presence of Cu2O on the substrate. Ex-situ spectroscopic ellipsometry indicated an average film thickness of 2.5 nm of Cu2O deposited with a growth per cycle of 0.05 Å/cycle, comparable to previous experiments. References: [1] T. Waechtler, S. Oswald, N. Roth, A. Jakob, H. Lang, R. Ecke, S. E. Schulz, T. Gessner, A. Moskvinova, S. Schulze, M. Hietschold, J. Electrochem. Soc., 156 (6), H453 (2009). [2] T. Waechtler, S. -F. Ding, L. Hofmann, R. Mothes, Q. Xie, S. Oswald, C. Detavernier, S. E. Schulz, X. -P. Qu, H. Lang, T. Gessner, Microelectron. Eng., 88, 684 (2011). [3] J. P. Espinós, J. Morales, A. Barranco, A. Caballero, J. P. Holgado, A. R. González Elipe, J. Phys. Chem. B, 106, 6921 (2002).

An experimental and theoretical approach is taken to determine the effect of a heterojunction on the effective work function in a metal/high-? gate stack, the characteristics of aqueous hydrochloric acid cleaned (aq-HCl) GaN surface and the interface between GaN and Al2O3, HfO2 and GaON. The investigation of the effect of a heterojunction on the effective work function in a metal/high-? gate stack found that when a Ge/Si heterostructure on silicon is lightly doped and sufficiently thin, the work function can be extracted in a manner similar to that for a simple silicon substrate. Modifications to the terraced oxide structure are proposed to remove oxidation effects of the alternate channel materials. The extracted work function of TiN with various thicknesses on HfSiO is found to be in agreement with that of TiN on a silicon substrate. X-ray and ultraviolet photoelectron spectroscopy are used to observe the interface electronic states at the GaN (0001) and Al2O3, HfO2 and GaON dielectric interfaces. The GaN is cleaned using aqueous HCl prior to thermal oxidation to form GaON and atomic layer deposition of Al2O3 and HfO2. This was followed by a post deposition anneal. The GaN/HfO2 and GaN/Al2O3 interfaces exhibited dipoles of 1.6 eV and 0.4 eV +/- 0.2 eV, respectively. It is determined that the formation of an interfacial layer at the GaN/HfO2 interface is the primary cause of the larger dipole. Due to the knowledge of the formation of an interfacial GaOx or GaON layer during atomic layer deposition of HfO2, a better understanding of the GaN/GaON interface is needed. To accomplish this task, the interface electronic states at the GaN(0001) and GaON interface are observed using X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS). XPS and UPS analysis of the GaN/GaON interface resulted in the calculation of a -2.7 eV +/- 0.2 eV dipole assuming that the core level shifts are only representative of the GaN band bending at the interface. If it is assumed that the core level shifts are only due to the oxidation of GaN, then the exhibited dipole at the GaN/GaON interface is -1.8 eV +/- 0.2 eV. Results indicate that the observed dipole is primarily caused by the polarization of the GaN. A theoretical approach is taken to provide a more complete understanding of the underlying formation mechanisms of a GaON interfacial layer during atomic layer deposition of HfO2. First, density functional theory is used to calculate the interactions of oxygen and water with the Ga-face of GaN clusters. The GaN clusters could be used as testbeds for the actual Ga-face on GaN crystals of importance in electronics. The results reveal that the local spin plays an important role in these interactions. It is found that the most stable interactions of O2 and the GaN clusters results in the complete dissociation of the O2 molecule to form two Ga-O-Ga bonds, while the most stable interactions between a H2O molecule and the GaN clusters are the complete dissociation of one of the O-H bonds to form a Ga-O-H bond and a Ga-H bond. Second, density functional theory is used to calculate the interaction of the reactants used to deposit HfO2 and Al2O3 during atomic layer deposition with hydrolyzed Ga-face GaN clusters. The results suggest that while further research is needed in this area to grasp a better understanding of the interactions of Trimethylaluminum (TMA) or Tertrakis(EthylMethylAmino)Hafnium (TEMAH) with hydrolyzed GaN clusters, it is found that a Ga-N(CH3)(CH2CH3) bond can form during the deposition of HfO2 using ALD and TEMAH as the reactant without breaking the Hf-N bond. The formation of a Ga-N(CH3)(CH2CH3) bond is significant because with the introduction of water into the system, the methyl and ethylmethyl groups may react to form a Ga-N-O bond which is believed to be the interfacial oxide found during deposition of HfO2 using ALD on GaN. No Ga-C bond structure formed in any fully optimized stable structure when analyzing the interaction of TMA with hydrolyzed GaN.

No description available.

Le but de cette thèse était de fabriquer des structures cœur / coquille à base de nanofils d’oxyde de zinc (ZnO) pour des applications en photovoltaïques principalement, et ensuite pour des détecteurs UV. Des réseaux de nanofils de ZnO de dimensions contrôlées ont été synthétisés en utilisant la méthode d’électrodéposition de ZnO (ECD). Nous avons également synthétisé des oursins organisés à base de nanofils de ZnO (U-ZnO NWs) en combinant les méthodes de nanostructuration de surface (auto-assemblage de sphères de polystyrène), dépôt de couche atomique (ALD) et ECD de ZnO. Plusieurs approches concernant le contrôle des dimensions de ces nanofils ont été envisagées. Les diamètres, la densité et la morphologie de ces nanofils ont été ajustés soit en modifiant les diamètres des sphères utilisés soit en modulant les paramètres expérimentaux durant la déposition (ALD et/ou ECD). Des monocouches et des multicouches de U-ZnO NWs de longueur variant de 750 nm jusqu'à 1500 nm ont été obtenus dans une large gamme de diamètre (57-170 nm).Ces matériaux ont été utilisés pour la construction de cellules solaires à colorant (DSSC) à base de réseaux de nanofils et des U-ZnO NWs, recouverts de couches minces d’oxyde de titane (TiO2) par dépôt de couches atomiques (ALD). Des rendements de conversion solaire de ~ 2% ont été atteints, sachant que le ZnO absorbe seulement dans l’UV. Ces matériaux ont été également utilisés pour la construction de cellules solaires de type II formés des U-ZnO NWs recouverts de couches d’oxyde de cuivre (Cu2O) de différentes épaisseurs par ECD. Les effets de la morphologie et des dimensions des nanofils et des U-ZnO NWs sur la diffusion de la lumière et la performance électronique des dispositifs ont été étudiés. Des capteurs d’ultraviolet ont été testés en utilisant les nanofils et les U-ZnO NWs. Une amélioration significative de la performance et de la stabilité en matière de détection UV a été observée en utilisant ces nanostructures de ZnO. Cela est dû à l'augmentation de la surface active offerte par les nanofils et les U-ZnO NWs en comparaison avec la performance obtenue avec les couches minces de ZnO. Finalement, une bioélectrode à base de nanofibres de polyacrylonitrile (PAN) recouverts par une couche d’or a été préparée pour la réduction électrochimique du CO2 en biocarburants utiles. L'électrode de PAN / Or a été préparée en utilisant une méthode de synthèse basée sur l'électrofilage suivi d'une pulvérisation d'Or. Une amélioration significative de l'activité électrochimique et de la stabilité de la bioélectrode a été observée. / The aim of this thesis was to fabricate core / shell structures based on zinc oxide (ZnO) nanowires for photovoltaic applications mainly, and UV sensors as well. ZnO nanowire arrays of controlled size were grown using electrodeposition method (ECD). We also synthesized organized urchins based on ZnO nanowires by combining methods of surface nanostructuring (self-assembly of polystyrene spheres), atomic layer deposition (ALD) and electrodeposition of ZnO (ECD). Several approaches concerning the control of dimensions on these nanowires have been investigated. The diameter, density and morphology of these nanowires were adjusted either by modifying the diameters of spheres or by modulating the experimental parameters during deposition (ALD and / or ECD). Organized monolayers and multilayers of urchins based on ZnO nanowires ranging between 750 -1500 nm in length were obtained in a diameter range between 50-170 nm. The construction of dye solar cells (DSSC) was based on nanowire arrays and organized urchins based on ZnO nanowires coated with thin shells of titanium oxide (TiO2) obtained by atomic layer deposition (ALD). As proof of concept, solar conversion efficiencies of ~ 2% were achieved, bearing in mind that ZnO absorbs only in UV range. These materials have also been used for solar cells construction of type II based on organized urchin-like ZnO nanowires coated with copper oxide (Cu2O) layers of different thicknesses by electrodeposition of Cu2O. The effects of the morphology and the dimension of the organized nanowires and urchin-like ZnO nanowires on light scattering and electronic performance of the devices have been studied. UV sensors were tested using nanowires and urchin-like ZnO nanowires. A significant improvement in the performance and stability in UV detection was observed when using these ZnO nanostructures. This is due to the increase in active area offered by the ZnO nanowires and urchins compared to the performance obtained with ZnO thin films. Finally, a bioelectrode based on polyacrylonitrile nanofibers (PAN) coated with a layer of gold has been prepared for the electrochemical reduction of CO2 into useful biofuels. The PAN/gold electrode was prepared using a homemade synthesis method, based on electrospinning followed by gold sputtering. A significant improvement in the electrochemical activity and the stability of the bioelectrode was observed.

abstract: In this dissertation, in-situ X-ray and ultraviolet photoemission spectroscopy have been employed to study the interface chemistry and electronic structure of potential high-k gate stack materials. In these gate stack materials, HfO2 and La2O3 are selected as high-k dielectrics, VO2 and ZnO serve as potential channel layer materials. The gate stack structures have been prepared using a reactive electron beam system and a plasma enhanced atomic layer deposition system. Three interrelated issues represent the central themes of the research: 1) the interface band alignment, 2) candidate high-k materials, and 3) band bending, internal electric fields, and charge transfer. 1) The most highlighted issue is the band alignment of specific high-k structures. Band alignment relationships were deduced by analysis of XPS and UPS spectra for three different structures: a) HfO2/VO2/SiO2/Si, b) HfO2-La2O3/ZnO/SiO2/Si, and c) HfO2/VO2/ HfO2/SiO2/Si. The valence band offset of HfO2/VO2, ZnO/SiO2 and HfO2/SiO2 are determined to be 3.4 ± 0.1, 1.5 ± 0.1, and 0.7 ± 0.1 eV. The valence band offset between HfO2-La2O3 and ZnO was almost negligible. Two band alignment models, the electron affinity model and the charge neutrality level model, are discussed. The results show the charge neutrality model is preferred to describe these structures. 2) High-k candidate materials were studied through comparison of pure Hf oxide, pure La oxide, and alloyed Hf-La oxide films. An issue with the application of pure HfO2 is crystallization which may increase the leakage current in gate stack structures. An issue with the application of pure La2O3 is the presence of carbon contamination in the film. Our study shows that the alloyed Hf-La oxide films exhibit an amorphous structure along with reduced carbon contamination. 3) Band bending and internal electric fields in the gate stack structure were observed by XPS and UPS and indicate the charge transfer during the growth and process. The oxygen plasma may induce excess oxygen species with negative charges, which could be removed by He plasma treatment. The final HfO2 capping layer deposition may reduce the internal potential inside the structures. The band structure was approaching to a flat band condition. / Dissertation/Thesis / Ph.D. Physics 2012