Metal oxides exhibit a wide range of chemical and electronic properties, making them an extremely interesting subject for numerous applications in modern electronics. The primary goal of this research is to develop metal-oxide-based electronic devices, including thin-film transistors (TFTs), resistance random-access memory (RRAM) and planar nano-devices. This research requires different processing techniques, novel device design concepts and optimisation of materials and devices. The first experiments were carried out to optimise the properties of zinc oxide (ZnO) semiconductors, in particular the carrier concentration, which determines the threshold voltage of the TFTs. Thermal annealing is one common method to affect carrier concentration and most work in the literature reports performing this process in a single-gas environment. In this work, however, annealing was carried out in a combination of air and nitrogen, and it was found that the threshold voltage could be tuned over a wide range of pre-determined values.Further experiments were undertaken to enhance the carrier mobility of ZnO TFTs, which is the most important material quality parameter. By optimising deposition conditions and incorporating a high-k gate dielectric layer, the devices showed saturation mobility values over 50 cm2/Vs at a low operating voltage of 4 V. This is, to our knowledge, one of the highest field-effect mobility values achieved in ZnO-based TFTs by room temperature sputtering. As an important type of metal-oxide-based novel memory devices, which have been studied intensively in the last few years, RRAM devices were also explored. New materials, such as tin oxide (SnOx), were tested, exhibiting bipolar-switching operations and a relatively large resistance ratio. As a novel process variation, anodisation was performed, which yielded less impressive results than SnOx, but with a potential for ultra-low-cost manufacturing. Finally, novel planar nano-devices were explored, which have much simpler structures than conventional multi-layered transistors and diodes. Three types of ZnO-based nano-devices (a side-gated transistor, a self-switching diode and a planar inverter) were fabricated using both e-beam lithography and chemical wet etching. After optimisation of the challenging wet etching procedure at nanometre scale, ZnO nano-devices with good reproducibility and reliability have been demonstrated.

Indium tin oxide (ITO) is the most widely used transparent electrode in flexible solar cells because of its high transparency and conductivity. But still, cracking of ITO on PET substrates due to tensile loading is not fully understood and it affects the functionality of the solar cell tremendously as ITO loses its conductivity. Here, we investigate the cracking evolution in ITO/PET exposed to two categories of tests. Monotonous tensile testing is done in order to trace the crack propagation in ITO coating as well as determining a loading range to focus on during our study. Five cycles test is also conducted to check the crack closure effect on the resistance variation of ITO. Analytical model for the damage in ITO layer is implemented using the homogenization concept as in laminated composites for transverse cracking. The homogenization technique is done twice on COMSOL to determine the mechanical and electrical degradation of ITO due to applied loading. Finally, this damage evolution is used for a simulation to predict the degradation of ITO as function in the applied load and correlate this degradation with the resistance variation. Experimental results showed that during unloading, crack closure results in recovery of conductivity and decrease in the overall resistance of the cracked ITO. Also, statistics about the crack spacing showed that the cracking pattern is not perfectly periodical however it has a positively skewed distribution. The higher the applied load, the less the discrepancy in the crack spacing data. It was found that the cracking mechanism of ITO starts with transverse cracking with local delamination at the crack tip unlike the mechanism proposed in the literature of having only cracking pattern without any local delamination. This is the actual mechanism that leads to the high increase in ITO resistance. The analytical code simulates the damage evolution in the ITO layer as function in the applied strain. This will be extended further to correlate the damage to the resistance variation in following studies.

>Magister Scientiae - MSc / Tin dioxide (SnO2) thin films are a worthy candidate for an electron transport layer (ETL) in perovskite solar cells, due to its suitable energy level, high electron mobility of 240 cm2 v-1 s- 1, desirable band gap of 3.6 - 4.0 eV, and ultimately proves to be suited for a low temperature thermal oxidation technique for ETL production. A variety of methods are available to prepare SnO2 thin films such as spin and dip coating and chemical bath deposition. However, the customary solid-state method, which incorporates thermal decomposition and oxidation of a metallic Sn precursor compound in an oxygen abundant atmosphere prevails to be low in cost, is repeatable and allows for large-scale processing.

Ce travail porte sur l’élaboration de matériaux nanostructurés et le contrôle de la formation de nanocristaux d’oxyde d’étain dans une matrice de silice amorphe obtenue par voie sol-gel. Préalablement à l’étude structurale et microstructurale des xérogels, une première partie de ces travaux de thèse concerne le procédé sol-gel. Le lavage des gels par des solutions hydro-alcooliques permet d’extraire une quantité importante d’acide chlorhydrique après gélification. Ainsi si les solutions de lavage sont renouvelées, 50 % de l’acide introduit peut être retiré. Ce lavage, associé avec un séchage contrôlé, a également permis de réduire significativement la durée du séchage et d’obtenir des xérogels centimétriques non fissurés.La seconde partie de ce travail a porté sur l’étude structurale et microstructurale des xérogels réalisée au travers de mesures de diffraction des rayons X ex situ ou de diffusion centrale et diffraction des rayons X couplée in situ en fonction de la température sur des lignes de lumière situées autour de sources synchrotrons. Nous avons montré que dans des xérogels contenant 10 % d’étain, la quantité de cristaux nanométriques d'oxyde d'étain peut augmenter continuellement sans que leur taille moyenne ne s’accroisse. La taille moyenne la plus faible est obtenue après un prétraitement thermique de séparation de phases préalable à celui de cristallisation et plus ce traitement est long plus la taille des cristaux est faible. Cette étude a été complétée par des traitements thermiques effectués in situ afin de suivre simultanément la séparation de phases et la cristallisation. Ces mesures ont permis d’observer le phénomène de séparation de phases dans les xérogels contenant 10 % d’étain et dont la quantité cristallisée obtenue lors d’un traitement thermique à 350 °C est la plus importante au regard des autres températures de traitement thermique et des concentrations en étain. / This PhD work deals with the development of nanostructured oxide materials and the control of the formation of tin oxide nanocrystals in an amorphous silica matrix obtained by sol-gel process. Prior to the structural and microstructural study of xerogels, a first part of this work concerns the sol-gel process. Washing the gels with hydroalcoholic solutions allows to extract a significant quantity of hydrochloric acid after gelation. Thus, if the washing solutions are renewed, 50% of the acid introduced can be removed. This washing, combined with improvement of the drying process, allowed to reduce the drying duration and finally to obtain bulk xerogels exhibiting a centimetric size.The second part of this work focuses on the structural and microstructural evolution of xerogels through thermal treatments. The results of this second part are obtained through ex situ measurements of X-ray diffraction or coupled small angle X-ray scattering and X-ray diffraction experiments realized in situ as a function of temperature. In both cases the measurements have been performed on synchrotron beamlines. We show that in xerogels containing 10% tin, the amount of nanosized tin oxide crystals can continuously increases without increasing the average size of these crystals. The lowest average size is obtained after a phase separation thermal pretreatment before crystallization and the longer this treatment is, the smaller the size of the crystals. This study is completed by heat treatments carried out in situ in order to simultaneously evidence phase separation and crystallization. These measurements allow to observe the phenomenon of phase separation by small angle X-ray scattering in xerogels containing 10% tin and whose crystallized quantity obtained during a thermal treatment at 350 °C is the highest compared to other heat treatment temperatures and tin concentrations.

Indium tin oxide is a transparent conductive oxide electrode which is widely used for organic electronics. Morphology of ITO plays an important role in the performance of organic electronics. To understand the influence of the substrate morphology in device performance, a controllable route for producing periodic and aperiodic roughness of ITO surfaces are necessary. In this thesis, this was attempted by using various approaches to forming ITO nanostructures. Initially, ITO was deposited by a traditional sputtering procedure. However, the roughness distribution of the sputtered ITO resulted in a s Gaussian distribution, unsuitable to further studies of roughness. ITO nanostructures can also be formed by depositing ITO nanoparticles on an ITO sub- strates. Using acetate and chloride precursors, ITO films were produced from solution and formed into nanoparticles using the reverse micelles deposition approach. The acetate route (InAc+SnCl2+ethanol), was the most successful prior to the nanoparticle formation, showing high quality ITO with bixbyte crystal structure and Sn percentages of 20%, low enough to form a conductive film. Nanoparticles were fabricated with diblock copolymer reverse micelles(PS-b-P2VP). Reverse micelles were found to act as a nano reactor, restricting the size of nanoparticles by having hydrophilic reactants undergo chemical reactions inside the micelles. However, nanoparticles from the reverse micelles revealed Sn percentages much above 20%. This was attributed to the solubility difference of the precursors leading to displacing or preventing of pre- cursor loading into the reverse micelles. The change of the stirring time, the micelles concentration, the sequence of precursors loading, and the weight of precursors were not found to affect the Sn concentration; moreover, large variations in Sn concentrations were observed. From quantitative nano mechanical testing of the micelles, a maximum load amount for the precursors was observed, confirming that the high concentration of Sn was likely due to the solubility differences between the precursors and their ability to penetrate the micelle. By manipulating the nanoparticles distribution through spin coating speeds, micelles concentration, and deposited volume, several degrees of order were obtained, though hexagonal packing was not observed. In general, even though Sn concentration were found to be above 20%, nanoparticles were successfully fabricated with reverse micelles, confirming that the reverse micelle technique is a good strategy for future studies of roughness. / Thesis / Master of Applied Science (MASc)

The work presented in this thesis can be divided into two research areas. First, two sets of organic-inorganic hybrid nanocomposites containing phenolic resin/trisilanolphenyl-POSS and phenolic resin/octa(aminophenyl)-T8-POSS nanocomposites were synthesized and the morphology and properties were investigated. Octa(aminophenyl)-T8-polyhedral silsesquioxane is an octafunctional-T8-POSS containing eight aniline-like amino groups, one on each corner silicon atom. It was synthesized in our laboratory by an improved two-step reaction sequence; nitration (HNO3) and reduction (HCOOH/Et3N). Varying amounts of POSS were codissolved with a resole phenolic resin in organic solvent. This was followed by solvent removal and thermal curing. Intermolecular interactions in these nanocomposites were probed by FT-IR. The micro-morphology and aggregation state of POSS were investigated using SEM, TEM, and WAXD studies. The thermal and mechanical properties and thermal stabilities of these composites were investigated by DMTA, DSC, and TGA. Second, two types of carbon-covered mono- and bimetallic (Sn, and Sn/Sb alloy) nanorods for use as anode materials in lithium ion batteries were synthesized by a thermal chemical vapor deposition method. Commercial antimony and tin oxide (Sb3O4/SnO2) nanopowders and added tin (IV) oxide (SnO2) nanoparticles (~19 nm) were used as the precursors for the growth of bimetallic Sn/Sb alloy and monometallic Sn nanorods, respectively. In addition, the shape of the products recovered were different when different hydrocarbon gas flow rates were used for growing intermetallic nanorods in carbon templates. Acetylene and methane were the gases tried. The morphologies and structures of the intermetallic nanorods in carbon templates were investigated using SEM and TEM and proved by X-EDS, XRD, and XPS studies.

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A custom-built surface sol-gel pumping system was built for applying conformal sol-gel based coatings with controlled thicknesses on three-dimensional (3-D) nanostructured templates. The 3-D templates utilized in this work were derived from biological species, such as diatoms and butterfly wings, as well as a synthetic photoresist polymer (SU-8). Tin oxide coatings were applied on silica-based diatom frustules using the automated surface sol-gel pumping system. An organic dendrimer method was developed for amplifying hydroxyl groups on the silica-based frustule surfaces to enhance the surface sol-gel deposition process. Conformal tin oxide coatings with controlled thicknesses were obtained on the hydroxyl amplified frustule surfaces; however, little if any deposition was observed on the frustules that were not subjected to the hydroxyl amplification process. The automated surface sol-gel system was also utilized to apply multicomponent tin oxide-doped titania alkoxide chemistries on the wing scales of a blue Morpho butterfly. The alkoxide solutions reacted directly with the OH functionalities provided by the native chitin chemistry of the scales. The tin oxide served as a rutile nucleating agent which allowed the titania to completely crystallize in the high refractive index rutile titania phase with doping concentrations of tin oxide as low as 7 mol % after annealing at 450oC. The tin oxide-doped titania coatings were both nanocrystalline and nanothick and replicated the nanostructured scales with a high degree of precision. Undoped titania coatings applied on the scales required a heat treatment of 900oC to crystallize the coating in the rutile titania phase which led to adverse coarsening effects which destroyed the nanostructed features of the scales. Tin oxide-doped titania coatings were also deposited on 3-D SU-8 photonic crystal structures. The coating was crystallized in an acidic solution at 80oC which led to the formation of rutile titania inverse opal photonic crystal structures which maintained the overall structure and ordering of the template. Barium titanate and europium-doped barium titanate coatings were applied on diatom frustules using a conventional reflux/evaporation deposition process. The silica-based diatom frustules had to first be converted into magnesia/silicon composite replicas using a gas/solid displacement reaction to render the template chemically compatible with the barium titanate-based coating. Conformal titanate-based coatings were obtained on the magnesia frustule replicas possessing uncontrolled thicknesses and excess inorganic particles using the reflux/evaporation deposition process. The europium-doped barium titanate coated frustules exhibited bright red photoluminescent properties upon stimulation with an ultraviolet light source.

Understanding interfacial charge injection processes is one of the key factors needed for development of efficient organic electronic devices, such as biosensors and energy conversion systems, since these processes control the electrical characteristics of these devices. Spectroelectrochemical characterization of electron transfer processes occurring at the electrode - electroactive thin film interface has been evaluated to improve our understanding of charge transfer kinetics using a novel form of electroreflectance spectroscopy, potential-modulated attenuated total reflectance (PM-ATR), which makes it possible to sensitively monitor spectroscopic changes in thin films as a function of applied potential.PM-ATR was used to evaluate three different redox-active films deposited on indium tin oxide (ITO) electrodes to investigate: i) the orientation dependence of charge transfer rates of thin films of biomolecules, ii) surface treatment and modification effects on charge transfer kinetics of conducting polymers and, iii) estimation of rates of electron injection and conduction band edge of semiconductor nanocrystalline materials.First, Prussian blue film as a model system was used successfully to examine the PM-ATR technique for determination of the charge transfer rate constant between ITO and a molecular film.Second, an anisotropic and redox active protein film, cytochrome c, was used to probe charge transfer rates with respect to molecular orientation. The electron transfer rate measured using TM polarized light was four-fold greater than that measured using TE polarized light. These data are the first to correlate a distribution of molecular orientations with a distribution of electron transfer rates in a redox-active molecular film.Third, the effects of ITO surface treatment and modification on charge transfer kinetics on a conducting polymer, poly(3,4-ethylenedioxythiophene/)/poly(styrenesulfonate) (PEDOT/PSS), were studied. The apparent interfacial charge transfer rate constant for PEDOT/PSS on ITO has been reported for the first time which cannot be measured otherwise with conventional electrochemistry due to high non-Faradaic background of PEDOT/PSS films.Fourth, PM-ATR enabled characterization of reversible redox processes between submonolayer coverages of surface-tethered, CdSe nanocrystals and ITO for the first time. Optically determined onset potentials for electron injection were used for estimation for the conduction band and valance band energies (ECB and EVB, respectively).