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We present an experimentally guided study of film layer structure and opto-electronic properties of transition metal oxide (TMO) films. The oxide material system studied comprised the metals silicon (Si), zinc (Zn), and indium (In). The films were deposited via radio frequency magnetron sputtering (RFMS) on room-temperature Corning Eagle XG Glass (CEXG) substrates. Distinct (bi-layer (BL) vs single-layer (SL)) layer structures manifest as a function of angular distribution or pressure distance product (Greek letter 'phi') of sputtered material flux sourcing film growth. The films are amorphous, transparent and semiconducting. Experimental determination of absolute temperature (T) dependence of resistivity (Greek letter 'rho') revealed that at temperatures close to room-temperature, ionized impurity scattering (IIS) is the dominant conduction electron scattering mechanism. Thence, application of the Brooks-Herring (BH) model of IIS permitted analysis of the electronic state of the films. Thereby, the electronic state was revealed to be highly compensated. The design of experiment (DOE) and (associated) response surface analysis (RSA) frameworks were recruited from the very first stage - namely, the stage of film fabrication - of this study. This provisioned a self-referencing set of (nine) films (the 'samples') that are the subject of this study. The two layers of the BL films are / will-be-referred-to-as the sub-plantation layer (SPL) and the thin-film layer (TFL). The SPL is situated mediate substrate and TFL, and constitutes thereby the film-substrate interface. For consistent nomenclature, the term 'TFL' will be used to refer to the sole (film) layer of SL films. The layer structures of the films were established via x-ray reflectometry (XRR). The films were interrogated optically via spectroscopic ellipsometry (SE) (at room-temperature), and electrically via AC Field Hall Effect (ACFHE) measurements (between T = 10.1 K to 300 K). An account of the understanding of the film layers - viz., SPL, and TFL - as has been achieved, is as follows: ~ The sub-plantation layer (SPL) ~ We report the controlled emergence of a bonafide nanoscale layer - the SPL - at (comprising) the film-substrate interface. The determination of presence of a SPL is direct - that is, sans any assumptions, or modeling - via Fourier analysis of XRR results. We present three independent - experimental, empirical, and theoretical - threads of analysis to rationalize emergence of the SPL, as follows: > In terms of deposition process conditions under which a SPL manifests. Our semi-quantitative analysis is in terms of angular distribution or phi of the material flux sourcing film growth. Evidently, this thread of analysis is beholden to the specific physics of the deposition process, namely, RFMS. > Via RSA of SPL physical properties (SPL thickness (dSPL), SPL density (DSPL), and SPL roughness (rSPL)). This analysis reveals the following two process factors to be relevant: RF power (PRF), and process gas pressure (p). While the analysis is on the basis of experimentally observed process factors dependence of the physical properties noted, it is not beholden to the physics of the deposition process (RFMS). > Via dimensional analysis (DA) of the physical properties noted previously, in light of RFMS process. The dimensionless group for PRF (PRF*) thus determined reveals precisely the two previously noted process factors to be relevant. This analysis is ab initio. We highlight implications of our results for the industrially important problem of sputtered-film-on-substrate adhesion. Thereby, our results bear commercial promise, particularly for research and development (R&D) of flexible electronics applications. ~ The thin-film layer (TFL) ~ We quantify the semiconducting nature of the films (TFLs) on basis of optical (via SE) and electrical (via ACFHE) measurements of their room-temperature electronic properties. We interrogate the film (material system) electronic state on basis of the experimentally determined T dependences of conduction electron concentration (n) and conduction electron mobility (Greek letter 'mu'). Presence of a T-range (in the vicinity of and including room-temperature) where IIS is the dominant conduction electron scattering mechanism is established. Application of the BH model of IIS then lead to the (quantitative) determination that the electronic state is (highly) compensated. This determination - consistent with the experimentally observed anomalous oxygen content dependence of - is consistent with trap limited conduction. Thereby, we relate the electronic state to the chemistry and physics of film microstructure and material system. ~ The ready-reckoner ~ Figure 7.1 presents another and visual walk through - a 'ready-reckoner' - of this study. ~ Epilogue ~ This study represents new lines of investigation for the Professor Peter P. Edwards FRS ML Group.

Since the fabrication of the first organic-inorganic halide perovskites solar cell in 2009 this material class has shown a lot of promise for solar cell and other semiconductor device applications. The rapid increase in the realised power conversion efficiencies and the unusual properties of the perovskite materials have drawn many researchers to focus on this material group. The perovskite materials which are investigated for use in solar cells, combine many advantageous properties which are known from either organic or inorganic semiconductors. Their high carrier mobilities, long carrier diffusion lengths, and long radiative lifetimes are similar to those in inorganic semiconductors, while the processibility at low temperatures and from solution as well as the chemical tunability of the optical properties are comparable to properties found in organic semiconductors. Co-evaporation is a versatile method to deposit organic-inorganic halide perovskite thin-films. It was pioneered in 2013 and offers several advantages over solution-based deposition techniques. Co-evaporated films are exceptionally smooth and uniform and due to the additive nature of the technique can be deposited onto solvent sensitive substrates which is crucial for the fabrication of flexible substrates or when building a multi-layer stack for tandem solar cells. In this thesis the co-evaporation of organic-inorganic halide perovskite thin-films is developed further and the resulting films and devices are studied in detail. Initially, the first reported co-evaporation of formamidinium lead triiodide (FAPbI3) solar cells is realised and high efficiencies are achieved. Subsequently, the impact of impurities on the co-vaporation of methylammonium lead triiodide (MAPbI3) is studied and insights are gained to improve the process control and reproducibility of the co-evaporation of perovskite thin-films. Finally, the experience and knowledge gained from these two studies are combined to fabricated co-evaporated patterned (FAPbI3) thin-films for applications in semi-transparent solar cells and micro-lasers. The results from this thesis are important contributions towards the deeper understanding of organic-inorganic halide perovskites and their properties as well as towards the development of stable, efficient, large-scale perovskites solar cells.

Ultrathin films of Cobalt, Iron and Manganese have been thennally evaporated onto an fcc Copper (111) single crystal substrate and investigated using a variety of surface structural teclmiques. The small lattice mismatch between these metals and the Cu (111) substrate make them an ideal candidate for the study of the phenomena of pseudomorphic film growth. This is important for the understanding of the close relationship between film structure and magnetic properties. Growing films with the structure of their substrate rather than their bulk phase may provide an opportunity to grow materials with novel physical and magnetic properties, and hence new technological applications. Both Cobalt and Iron have been found to initially maintain a registry with the fee Cu (111) surface in a manner consistent with pseudomorphic growth. This growth is complicated by island rather than layer-by-layer growth in the initials stages of the film. In both cases a change in the structure of the film seems to occur at a point where the coalescence of islands in the film may be expected to occur. When the film does change structure they do not form a perfect over-layer with the structure of their bulk counterpart. The films do contain a number of features representative of the bulk phase but also contain considerable disorder and possibly remnants of fcc (111) structure. The order present in these films can be greatly improved by annealing. Manganese appears to grow with an fee Mn (111) lattice spacing and there is no sign of a change in structure in films of up to 4.61 ML thick. The gradual deposition and annealing of a film to 300°C, with a total deposition time the same as that for a 1 ML thick film, causes a surface reconstruction to occur that is apparent in a R30° (√3×√3) LEED pattern. This is attributed to the formation of a surface alloy, which is also supported by the local expansion of the Cu lattice in the (111) direction.

PVD hard ceramic coatings grown via the combined cathodic arc/unbalance magnetron deposition process were studied using Raman microscopy. Characteristic spectra from binary, multicomponent, multilayered and superlattice coatings were acquired to gain knowledge of the solid-state physics associated with Raman scattering from polycrystalline PVD coatings and to compile a comprehensive spectral database. Defect-induced first order scattering mechanisms were observed which gave rise to two pronounced groups of bands related to the acoustical (150-300cm[-1]) and optical (400-750cm[-1]) parts of the phonon spectrum. Evidence was gathered to support the theory that the optic modes were mainly due to the vibrations of the lighter elements and the acoustic modes due to the vibrations of the heavier elements within the lattice. A study into the deformation and disordering on the Raman spectral bands of PVD coatings was performed. TiAIN and TiZrN coatings were intentionally damaged via scratching methods. These scratches were then analysed by Raman mapping, both across and along, and a detailed spectral interpretation performed. Band broadening occurred which was related to "phonon relaxation mechanisms" as a direct result of the breaking up of coating grains resulting in a larger proportion of grain boundaries per-unit-volume. A direct correlation of the amount of damage with band width was observed. Band shifts were also found to occur which were due to the stresses caused by the scratching process. These shifts were found to be the largest at the edges of scratches. The Raman mapping of "droplets", a defect inherent to PVD deposition processes, found that higher compressive stresses and large amounts of disorder occurred for coating growth onto droplets. Strategies designed to evaluate the ability of Raman microscopy to monitor the extent of real wear on cutting tools were evaluated. The removal of a coating layer and subsequent detection of a base layer proved successful. This was then expanded to real wear situations in which tools were monitored after 3,6,12,64,120 and 130 minutes-in-cut. A PCA chemometrics model able to distinguish between component layers and oxides was developed. Raman microscopy was found to provide structural and compositional information on oxide scales formed on the surfaces of heat-treated coatings. Wear debris, generated as a consequence of sliding wear tests on various coatings, was also found to be primarily oxide products. The comparison of the oxide types within the debris to those formed on the surface of the same coating statically oxidised, facilitated a contact temperature during sliding to be estimated. Raman microscopy, owing to the piezo-spectroscopic effect, is sensitive to stress levels. The application of Raman microscopy for the determination of residual compressive stresses within PVD coatings was evaluated. TiAlN/VN superlattice coatings with engineered stresses ranging -3 to -11.3 GPa were deposited onto SS and HSS substrates. Subsequent Raman measurements found a correlation coefficient of 0.996 between Raman band position and stress (determined via XRD methods). In addition, there was also a similar correlation coefficient observed between hardness and Raman shift (cm-1). The application of mechanical stresses on a TiAlCrN coating via a stress rig was investigated and tensile and compressive shifts were observed.

The search for new coating materials, particularly high-refractive-index layers, is crucial in the field of interferometric gravitational-wave (GW) detectors. These detectors require coatings with low mechanical loss to minimize thermal noise and low optical absorption to maintain measurement stability and precision. The development of novel high-index coating materials with improved mechanical and optical properties has the potential to advance GW detection and enable more precise measurements of astrophysical phenomena.This study investigated the structural and mechanical properties of amorphous silicon (a-Si), hydrogenated amorphous silicon (a-Si:H), and amorphous silicon carbide (a-SiC) films deposited using magnetron sputtering (MS). The effects of deposition parameters, such as working gas, gas pressure, substrate temperature, and post-growth treatments including vacuum annealing and post-hydrogenation, were explored. The choice of working gas and its pressure, which influences the kinetic energy of the sputtered atoms upon arrival at the substrate, was found to significantly affect the properties of the deposited films. The impact of energetic incoming atoms is reflected in compressive film stress and film densification, a phenomenon known as the atomic peening effect. Additionally, a transition in dominant defects from nanovoids in e-beam a-Si to divacancies and self-interstitials in MS a-Si was observed, which can be attributed to the higher kinetic energy of incident atoms. By selecting appropriate working gas and deposition conditions, such as low gas pressure and high growth temperature, the structural order was improved, as indicated by lower bond angle deviation, and the mechanical loss of MS a-Si was reduced at both low temperatures and room temperature.Introduction of hydrogen to a-Si had a significant impact on its optical absorption at infrared wavelengths and the room-temperature mechanical loss. We propose that hydrogen plays a dual role in a-Si:H, acting as a passivating agent for dangling bonds, particularly at high temperatures, and facilitating structural relaxation, and the latter is responsible for the observed changes in the physical properties of a-Si:H. The incorporation of carbon in a-SiC films resulted in higher mechanical loss and optical absorption compared to pure a-Si films. These findings provide insights into the underlying mechanisms and offer potential solutions for optimizing the performance of a-Si-based coatings for GW detector mirrors.

To design high pressure fuel system components that resist wear and scuffing failure when operated in low viscosity fuels, a comprehensive study on the tribological performance of various existing coating materials is necessary. This thesis aims to provide the relative performance of a variety of coating materials across different fuel environments by testing them in conditions that model those experienced in fuel pumps. The relative performance of these coatings are then indexed across a variety of material properties, including hardness, elastic modulus, wettability, and the interaction between the surface and the various types of fuel molecules.

Increasing the efficiency of gas turbine engines, both for aviation and commercial power generation, means higher operation temperatures and new materials capable of withstanding the increasingly extreme environments in the hot sections of these engines. Ceramic matrix composites have increased temperature capabilities, and particularly porous matrix oxide fiber ceramic composites (OFCCs) are promising materials due to their innate oxidative stability, resistance to thermal shock, cost, and ease of manufacture. However, OFCCs are not without limitations. The fibers and porous matrices have temperature limitations for microstructural stability, and the primary oxide constituents, Al2O3 and especially SiO2, have issues with corrosion and volatilization in high temperature water vapor, a major constituent of combustion atmospheres. Components require thermal and environmental barrier coatings (T/EBCs) with engineered structures and properties to maximize protection. This work studied techniques for building multilayered T/EBC systems for OFCCs and tests their efficacy. Two generations of air plasma sprayed (APS) coated OFCC coupons were supplied by Siemens Corporate Technology for durability assessment. These were compared against in-house coated OFCC coupons using electron beam-physical vapor deposition (EB-PVD) in thermocyclic testing from room temperature to 1200°C. EB-PVD coated samples performed better, with significant delamination seen in the APS coated specimens. The porous matrices of the OFCCs, while necessary for bulk damage tolerance and fiber pullout, complicates adhesion of these barrier coatings. Precursor impregnation and pyrolysis was used to infiltrate uncoated OFCC coupons with both alumina and yttria stabilized zirconia precursor solutions to create a gradient in density to selectively strengthen the matrix region near the surface to be coated, without sacrificing bulk toughness. The gradient was characterized using Vickers microhardness indentation tests of matrix pockets in cross-section. Further EB-PVD coating was performed on hardened, uncoated OFCCs, with additional compositions from 7wt% yttria stabilized zirconia (7YSZ) to more yttria rich compositions of Y4Zr3O12 (YZO) and Y2O3 with better matched thermal expansion to the OFCC. The latter compositions were deposited in bilayer configurations with a thin 7YSZ interlayer to prevent diffusional interaction with the OFCC. Despite morphological irregularities observed in 7YSZ and Y2O3 depositions, especially at deposition temperatures above 1080°C, adherent coatings with desirable columnar microstructures were grown in all three compositions, with deposition temperatures below 1035°C. Finally, select EB-PVD coated OFCCs were thermally cycled in flowing water vapor at 1200°C to assess durability of the coatings and amount of damage to the SiO2 – containing fibers from water vapor ingress through the porous coating. All coatings remained adherent, fiber damage from SiO2 volatilization was observed, especially around coating defects. Specimens with denser interlayers did mitigate some ingress, coating and OFCC surface defects still provided pathways for water vapor. The multilayer thermal and environmental barrier coating systems for OFCCs assembled and tested in this work provides insight into creating needed effective barrier coatings for the implementation of OFCCs into hot gas components of gas turbine engines.

This dissertation tested the hypothesis that energy transferred from a plasma or plume can be used to optimize the structure, chemistry, topography, optical and electrical properties of pulsed laser deposited and sputtered thin-films of ZnO, a-BOxNy, and few layer 2H-WS2 for transparent electronics devices fabricated without substrate heating or with low substrate heating. Thus, the approach would be compatible with low-temperature, flexible/bendable substrates. Proof of this concept was demonstrated by first optimizing the processing-structure-properties correlations then showing switching from accumulation to inversion in ITO/a-BOxNy/ZnO and ITO/a-BOxNy/2H-WS2 transparent MIS capacitors fabricated using the stated processes. The growth processes involved the optimization of the individual materials followed by growing the multilayer stacks to form MIS structures. ZnO was selected because of its wide bandgap that is transparent over the visible range, WS2 was selected because in few-layer form it is transparent, and a-BOxNy was used as the gate insulator because of its reported atomic smoothness and low dangling bond concentration. The measured semiconductor-insulator interfacial trap properties fall in the range reported in the literature for SiO2/Si MOS structures. X-ray photoelectron spectroscopy (XPS), Hall, photoluminescence, UV-Vis absorption, and X-ray diffraction (XRD) measurements investigated the low-temperature synthesis of ZnO. All films are nanocrystalline with the (002) XRD planes becoming more prominent in films grown with lower RF power or higher pressure. Low power or high chamber pressure during RF magnetron sputtering resulted in a slower growth rate and lower energetic conditions at the substrate. Stoichiometry improved with RF power. The measurements show a decrease in carrier concentration from 6.9×1019 cm-3 to 1.4×1019 cm-3 as power increased from 40 W to 120 W, and an increase in carrier concentration from 2.6×1019 cm-3 to 8.6×1019 cm-3 as the deposition pressure increased from 3 to 9 mTorr. The data indicates that in the range of conditions used, bonding, stoichiometry, and film formation are governed by energy transfer from the plasma to the growing film. XPS characterizations, electrical measurements, and atomic force microscopy (AFM) measurements reveal an increase in oxygen concentration, improved dielectric breakdown, and improved surface topography in a-BOxNy films as deposition pressure increased. The maximum breakdown strength obtained was ~8 MVcm-1, which is comparable to a-BN. Metal-Insulator-Metal (MIM) structures of a-BOxNy grown at 10 and 15 mTorr suggest a combination of field-enhanced Schottky emission and Frenkel-Poole emission are likely transport mechanisms in a-BOxNy. In comparison, better fitted data was gotten for field enhanced Schottky emission which suggests the more dominant mechanism. The static dielectric constant range is 3.26 – 3.58 for 10 and 15 mTorr films. Spectroscopic ellipsometry and UV-Vis spectroscopy measured a bandgap of 3.9 eV for 15 mTorr grown a-BOxNy. 2H-WS2 films were grown on both quartz and a-BOxNy which revealed that the XRD (002) planes became more prominent as substrate temperature increased to 400 oC. AFM shows nano-grains at lower growth pressure. Increasing the growth pressure to 1 Torr resulted in the formation of larger particles. XPS chemical analysis reveals improved sulfur to tungsten ratios as pressure increased. Sulfur deficient films were n-type, whereas sulfur rich conditions produced p-type films. Frequency dependent C-V and G-V measurements revealed an interface trap concentration (Nit) of 7.3×1010 cm-2 and interface state density (Nss) of 7.5×1012 eV-1cm-2 for the transparent ITO/a-BOxNy/ZnO MIS structures, and approximately 2 V was required to switch the a-BOxNy/ZnO interface from accumulation to inversion. Using 2H-WS2 as the channel material, the ITO/a-BOxNy/2H-WS2 required approximately 4 V to switch from inversion to accumulation in both n and p-channel MIS structures. Interface trap concentrations (Nit) of 1.6×1012 cm-2 and 3.2×1010 cm-2, and interface state densities (Nss) of 1.6×1012 eV-1cm-2 and 6.5×1012 eV-1cm-2 were calculated for n and p-channel 2H-WS2 MIS structures, respectively. The data from these studies validate the hypothesis and demonstrate the potential of ZnO, a-BOxNy, and few layer 2H-WS2 for transparent electronics.

Lithium-ion batteries (LIBs) have been widely used in electric vehicles, portable devices, grid energy storage, and space because of their high energy densities, power density, and high cycle-life. Since the commercialization of LIBs in 1991 by Sony Inc., the energy density of LIBs has significantly increased, closing to ~250 Wh kg-1 (900 kJ kg-1). However, if operated improperly, the stored energy can be abruptly released in the form of fire or explosions. Accidents involving battery fires and explosions in cell phones, laptops, electric vehicles, and airplanes have occurred often in recent years. Some have caused severe threats to human life and health and have led to numerous product recalls by manufacturers. These incidents underline the urgent need to develop methods and materials to improve the safety of LIBs. LIBs using the traditional carbonate-based organic liquid electrolytes (OLE) in which organic solvents are flammable and prone to catching fires limits its operation when the battery is operated beyond 65 °C. In this dissertation, the primary focus is to replace the flammable components of LIBs with new materials that have little to no heat release, so that in the event of an abuse condition, there will be less fire or smoke, to begin with. Battery separators play a crucial role in determining LIB safety. The primary function of the separator is to prevent physical contact between the anode and cathode, thereby preventing electrical shorting while facilitating ion transport in the cell. Any electrical (electronic) connection between the two electrodes (cathode and anode) can create a short circuit. An electrical short circuit can lead to a sudden discharge and consequent cell heating that may ultimately result in battery thermal runaway and potentially fire and even explosion due to the increasing temperature inside the LIB. Short circuits between battery cell electrodes can occur for several reasons, such as lithium dendrite (wire of metallic lithium) growth, and dimensional shrinkage or fracture of the separator under unusual heating of the cell. Therefore, to enhance the safety of LIBs, and enhance the thermal stability of separators, we have contributed in developing a binder-free, thin-film ceramic coating on a commercial separator, conceived and patented by the UD/UDRI battery laboratory. The new separator has been demonstrated to enhance thermal stability without compromising the electrochemical performance of LIB and adding only a negligible weight and ceramic coating thickness (Gogia et. al., 2021), and has been published in the journal of American Chemical Society (ACS) Omega.Solid-state batteries replace the OLE with inorganic solid ceramic electrolytes (SCE) that are thermally stable and make these batteries safer for wide range including high-temperature operations. However, one of the significant challenges is the high interfacial impedance of SCEs with the solid electrodes (cathode and anode), which negates battery power capability and useable energy density. To address those challenges, we have systematically investigated different materials, and their coating techniques to form a stable interface between SCE and Li anode. We have also found that materials such as gold (Au) deposited by sputtering, helps in forming an stable interface between SCE and Li anode, and has been tested at different temperatures. After designing a stable interface of Li anode with SCE, we have discussed the experimental details, cells assembly, and the electrochemical performance of SCE based molten Li battery that can operate at extremely high temperatures (>230 °C - 500 °C) required for space exploration investigating hot planets like Venus and useful for stationary energy storage. A molten Li-battery based on SCE uses electrodes in a molten phase. In summary, we demonstrated a proof-of-concept H.T. molten Li║Se SCE based cell functional at 465 °C. A part of this research has been published in the journal of energy and fuels (Gogia et. al., 2021).Further, we have also explored strategies to improve the performance of room-temperature all-solid-state Li batteries (ASLB) using SCE and two solid-state electrodes. ASLB is most suitable for powering electric vehicles and high-performance electronics. This research further investigates the performance of the ASLB at various charge/discharge voltages with impedance spectroscopy and cathode morphology, and studies the degradation mechanisms responsible for capacity fade and SCE decomposition when placed in contact with active materials. The publication based on this research is under submission (Gogia et. al, 2021).Finally, the last section concludes with a summary of all the work carried out in this dissertation and a perspective on future battery performance and safety.

The next generation of electronic and optical devices require high quality, crystalline materials in order to obtain relevant properties for novel devices. Two classes of materials offer unique material properties that can satisfy the requirements for next generation devices. These two classes of materials are the transition metal nitrides (TMNs) and transition metal oxides (TMOs). These materials offer electronic properties that range from conductive, metallic, materials to semiconducting and insulating materials. However, for many optical and electronic applications, the band structure and crystalline symmetries must be preserved. This work examines the growth and characterization of the TMN materials AlN and ScN as well as the TMO materials VO2 and TiO2. In all these materials, the crystalline structure plays and extremely important role in the desired properties. In addition, incorporation of other impurities can detrimentally impact the functionality of these film materials. In order to minimize the impurity incorporation and maintain the crystalline structure, the growth of AlN, ScN, VO2, and TiO2 films by various deposition techniques were examined and optimized. This allowed growth of high quality TMN and TMO materials that resulted in characterization and optimization of the relevant optical, electronic, and structural properties and, somewhat, the degree to which these properties could be tuned through growth conditions.

Two pi-conjugated polymers containing isoindigo or 3,3-(ethane-1, 2 diylidene)bis(indolin-2-one) (EBI) units with latent hydrogen-bonding on the main chain were synthesized and characterized. The designed polymers use thermal liable t-Boc groups as side chains on the backbone and can be easily dissolved in common organic solvent. Further thermal treatment of the polymers at around 180 oC can convert the polymers into strong hydrogen-bonded materials. The effect of formation of intermolecular hydrogen bonding networks on the polymer film properties including the UV/Vis absorption and electrochemical properties are studied. In the second part of this work, 2D organic single crystals of three conjugated small molecules, di-tert-butyl 1,4-dioxo-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-2,5(1H,4H)-dicarboxylate (DPPBoc), isoindigo, and cyclized DPP were successfully prepared by either solution epitaxial growth, mechanical exfoliation, or physical vapor deposition methods for organic field-effect transistor (OFET) applications. A thickness that less than 100 nm can be achieved for the obtained 2D crystals.

Magnesium is a promising candidate for biodegradable applications. However, the performance of magnesium based implants is hampered by fast corrosion of the implants as well as hydrogen evolution and excess alkalinity in the vicinity of the implant. Unalloyed magnesium with high purity shows higher resistance to corrosion in simulated body fluids than commercial magnesium and magnesium alloys.The experiments for preparing high purity magnesium coatings using thermal PVD system have been described. The coatings were evaluated using D.C. polarization tests, in vitro and in vitro tests. These high purity coatings lower the corrosion potential and corrosion current of bulk magnesium in simulated body fluid environment and increased cell activity was also observed near the coated surfaces of conventional implant materials. The different issues arising out of using bulk polycrystalline magnesium in the human body can be addressed by using single crystals. This document describes successful efforts to design, build, establish, test and utilize a single crystal grower using the Bridgman approach for directional solidification and study the obtained single crystals. The obtained single crystals were verified for their quality using metallography with optical microscopy, powder x-ray diffraction, laue x-ray diffraction, x-ray pole figures and micro-computed tomographyThe mechanical properties of single crystal magnesium were studied in comparison with polycrystalline magnesium through tensile, compressive, 3-point bend and izod tests. These tests indicated that single crystal magnesium can have high ductility. Further, the microstructure response to compressive load in two orthogonal directions was also studied by electron backscattered diffraction and x-ray pole figure analysis. It revealed incipient recrystallization at strains as low as 8 % strain during compression. The observed variation in microstructural response with the orientation allows for wide range for tailoring mechanical properties of magnesium single crystals Electrochemical D.C polarization tests were carried out on these single crystals and they showed an improvement in corrosion potential. Additionally, the response of magnesium single crystals was observed In vivo in sub cutaneous implantation in mice, ACL ring in goat and Ulna fracture model in rabbits. The in vivo tests showed favorable cell response and healthy tissue growth around the implant. Overall, the high purity magnesium coatings and magnesium single crystals reveal unique and promising properties, which can be harnessed for biomedical applications.

The historical and current market trends for transparent conductive coating are considered. The metal oxide transparent conductive coatings are found to have all but reached their theoretical limits. In light of this background, a coating process that was developed for an electron-beam deposition chamber at VisiMax Technologies is described. The coating process is shown to be capable of depositing an ITO film that is on par with the protective coatings that are currently on the market. The protective coating market is investigated and found to be sufficiently large for a specialized thin film-coating firm to enter. The ITO film that was produced by this process had a sheet resistance of 62 ohm-squares and an average transmission through the visible range (400nm – 700nm) of 89.4%.

The focus of this research is to develop, implement, and utilize phase-field models to study microstructure evolution in thin films during physical vapor deposition (PVD). There are four main goals to this dissertation. First, a phase-field model is developed to simulate PVD of a single-phase polycrystalline material by coupling previous modeling efforts on deposition of single-phase materials and grain evolution in polycrystalline materials. Second, a phase-field model is developed to simulate PVD of a polymorphic material by coupling previous modeling efforts on PVD of a single-phase material, evolution in multiphase materials, and phase nucleation. Third, a novel free energy functional is proposed that incorporates appropriate energetics and dynamics for simultaneous modeling of PVD and grain evolution in single-phase polycrystalline materials. Finally, these phase-field models are implemented into custom simulation codes and utilized to illustrate these models’ capabilities in capturing PVD thin film growth, grain and grain boundary (GB) evolution, phase evolution and nucleation, and temperature evolution. In general, these simulations show: grain coarsening through grain rotation and GB migration such that grains tend to align with the thin film surface features and GBs migrate to locations between these features so that each surface feature has a distinct grain and orientation; the incident vapor flux rate controls the density of the thin film and the formation of surface and subsurface features; the substrate phase distribution initially acts as a template for the growing microstructure until the thin film becomes sufficiently thick; latent heat released during PVD increases the surface temperature of the thin film creating a temperature gradient within the thin film influencing phase evolution and nucleation; and temperature distributions lead to regions within the thin film that allow for multiple phases to be stable and coexist. Further, this work shows the sequential approach for coupling phase-field models, described in goals (i) and (ii) is sufficient to capture first-order features of the growth process, such as the stagnation of GBs at the valleys of the surface roughness, but to capture higher-order features, such as orientation gradients within columnar grains, the single free energy functional approach developed in goal (iii) is necessary.

Abstract: Glancing angle deposition (GLAD) is a thin film deposition technique that utilizes oblique vapour incidence and substrate rotation to grow various nanocolumn structures. The growth of these structures is heavily influenced by the substrate temperature during deposition. Therefore, in-situ change of substrate temperature offers an additional dimension of control for GLAD growth. This thesis describes the design of a GLAD compatible heating and cooling system. This system is then used to explore the effects of substrate temperature on the inclination angle of slanted posts grown through GLAD. Results varied depending on material type and material melting temperature. Using the heating system, a method was developed for producing Sn seeds through thermal dewetting. SiO2 vertical posts were grown on seeded and unseeded samples, and a linear relationship was observed between seed separation and post separation.

The thermo-mechanical effects on the strain evolution within an EB-PVD thermal barrier coating (TBC) is presented in this work using in-situ characterization. Synchrotron X-ray diffraction at sector 1-ID at the Argonne National Laboratory provided both qualitative and quantitative in-situ data on the strain evolution under a thermal cycle with mechanical loading. The results show that at a critical combination of temperature and load, the stress in the thermally grown oxide (TGO) layer in the TBC reaches a tensile region. These significant findings enhance existing literature showing purely compressive strains within the TGO where mechanical loads have been neglected. The results have important implications on the effects on the overall life of the coating. Depth resolved quantitative strain is presented as contour plots over a thermal cycle highlighting the complementary strains in the adjacent layers including the bond coat and the TBC with time and temperature. Systematic identification of the appropriate peaks within the multi-layer TBC system provides guidelines for future strain studies using high energy X-rays. Piezospectroscopic studies with applied mechanical loading are further presented as verification of the room temperature XRD data for future development of the method as an operational technique to be used outside the laboratory environment.

A detailed understanding of failure mechanisms in thermal barrier coatings (TBCs) can help develop reliable and durable TBCs for advanced gas turbine engines. One of the characteristics of failure in electron beam physical vapor deposited (EB-PVD) TBCs is the development of instability, named rumpling, at the interface between (Ni, Pt)Al bond coat and thermally grown oxide (TGO). In this study, thermal cycling at 1100°C with 1 hr dwell time was carried out on 25.4mm disc specimens of TBCs that consisted of EB-PVD coated ZrO2-7wt. %Y2O3, (Pt,Ni)Al bond coat, and CMSX-4 Ni-based superalloy. At specific fraction of lifetime, TBCs were examined by electron microscopy and photostimulated luminescence (PL). Changes in the average compressive residual stress of the TGO determined by PL and the magnitude of rumpling, determined by tortuosity from quantitative microstructural analyses, were examined with respect to the furnace thermal cyclic lifetime and microstructural evolution of TBCs. The combination of elastic strain energy within the TGO and interfacial energy at the interface between the TGO and the bond coat was defined as the TGO energy, and its variation with cyclic oxidation time was found to remain approximately constant ~135J/m2 during thermal cycling from 10% to 80% thermal cyclic lifetime. Parametric study at ~135J/m2 was performed and variation in residual stress with rumpling for different oxide scale thicknesses was examined. This study showed that the contribution of rumpling in residual stress relaxation decreased with an increase in TGO thickness. High pressure turbine blades serviced for 2843 hours and in the as coated form were also examined using electron microscopy and photostimulated luminescence. The difference in iv residual stress values obtained using PL on the suction and pressure sides of as-coated turbine blade were discussed. The presence of a thick layer of deposit on the serviced blade gave signals from stress free α-Al2O3 in the deposit, not from the TGO. The TGO growth constant data from the disc-shape TBCs, thermally cycled at 1100°C, and studies by other authors at different temperatures but on similar EB-PVD coated TBCs with (Pt, Ni)Al bond coat and CMSX-4 Nibased superalloy were used to determine the temperature profile at the YSZ/bond coat interface. The interfacial temperature profiles of the serviced blade and the YSZ thickness profile were compared to document the variable temperature exposure at the leading edge, trailing edge, suction and the pressure side.

Catalysts can be significantly improved by modifying their structure or composition. Simple adaptations of the physical structure of a catalyst can give rise to changes in the chemical behavior, in part, due to alterations in the coordination of active sites. Modifications in the surface or bulk composition of a material have a profound impact on the chemistry that is promoted as a result of electronic and physical factors. Optimizing these qualities may enhance the catalyst’s activity, selectivity or stability. In this dissertation, we explore the application of two distinct approaches for modifying the chemical properties of catalytically active materials. Through the use of a broad array of techniques we quantify changes in critical properties such as physical-crystallographic structure; morphology, surface area and porosity; as well as catalytic activity, selectivity and stability. First, reactive ballistic deposition of metal atoms within a low pressure gas provides a unique opportunity for synthesizing thin films of a wide variety of materials. The morphology, structure, and porosity of the resulting material can be tailored through control of the deposition angle and substrate temperature. By conducting deposition perpendicular to the surface, a film can be grown with a dense, conformal structure. On the other hand, deposition at oblique angles results in high surface area, porous films comprised of regular arrays of nanocolumnar structures. Furthermore, variations in the deposition angle allow for the inclusion of under-coordinated sites which change the chemical activity of the surface. Improvements in the activity, selectivity and stability of transition metal catalysts can be made by alloying the catalyst with a second element. The formation of molybdenum carbide decreases the strength of chemisorption on the surface, with respect to molybdenum, and improves selectivity for the dehydrogenation of formic acid. Platinum is active for the water-gas shift reaction. However, this catalyst cannot operate at low temperatures due to CO poisoning and is susceptible to deactivation due to accumulation of carbonaceous deposits. The formation of a platinum-copper near-surface alloy dramatically modifies the interactions of the surface with CO, H₂O and H₂ which can enhance the performance of this catalyst for the water-gas shift reaction.

The ability to improve performance of the high-end metal oxide semiconductor field effect transistor (MOSFET) is highly reliant on the dimensional scaling of such a device. In scaling, a decrease in dielectric thickness results in high leakage current between the electrode and the substrate by way of direct tunneling through the gate dielectric. Observation of a high leakage current when the standard gate dielectric, SiO2, is decreased below a thickness of 1.5 nm requires engineering of a replacement dielectric that is much more scalable. This high- dielectric allows for a physically thicker oxide, reducing leakage current. Integration of select lanthanide-based oxides and silicates, in particular lanthanum oxide and silicate, into MOS gate stack devices is examined. The quality of the high-K dielectrics is monitored electrically to determine properties such as equivalent oxide thickness, leakage current density and defect densities. In addition, analytical characterization of the dielectric and the gate stack is provided to examine the materialistic significance to the change of the electrical properties of the devices. It is shown that optimization of low-temperature processing can result in MOS devices with an equivalent oxide thickness (EOT) as low 5 Å and a leakage current density of 5.0 A⁄cm2. High-temperature processing, consistent with a MOSFET source-drain activation anneal, yields MOS devices with an EOT as low as 1.1 nm after optimization of the TaN/W electrode properties. The decrease in the device effective work function (phi_M,eff) observed in these samples is examined in detail. First, as a La2O3 capping layer on HfSiO(N), the shift yields ideal-phi_M,eff values for nMOSFET deices (4.0 eV) that were previously inaccessible. Other lanthanide oxides (Dy, Ho and Yb) used as capping layers show similar effects. It is also shown that tuning of phi_M,eff can be realized by controlling the extent of lanthanide-silicate formation. This research, conducted in conjunction with SEMATECH and the SRC, represents a significant technological advancement in realizing 45 and sub-45 nm MOSFET device nodes.

Tribological thin films are of interest to designers and end-users of friction management and load transmission components such as steel rolling element bearings. This study sought to reveal new information about the properties and formation of such films, spanning the scope of their technical evolution from natural oxide films, to antiwear films from lubricant additives, and finally engineered nanocomposite metal carbide/amorphous hydrocarbon (MC/a-C:H) films. Transmission electron microscopy (TEM) was performed on the near-surface material (depth < 500 nm) of tapered roller bearing inner rings (cones) that were tested at two levels of boundary-lubricated conditions in mineral oil with and without sulfur- and phosphorus-containing gear oil additives. Site-specific thinning of cross-section cone surface sections for TEM analyses was conducted using the focused ion beam milling technique. Two types of oxide surface films were characterized for the cones tested in mineral oil only, each one corresponding to a different lubrication severity. Continuous and adherent antiwear films were found on the cone surfaces tested with lubricant additives, and their composition depended on the lubrication conditions. A sharp interface separated the antiwear film and base steel. Various TEM analytical techniques were used to study the segregation of elements throughout the film volume. The properties of nanocomposite tantalum carbide/amorphous hydrocarbon (TaC/a-C:H) thin films depend sensitively on reactive magnetron sputtering deposition process conditions. TaC/a-C:H film growth was studied as a function of three deposition parameters in designed experiments: acetylene flow rate, applied d.c. bias voltage, and substrate carousel rotation rate. Empirical models were developed for the following film characteristics to identify process-property trend relationships: Ta/C atomic ratio, hydrogen content, film thickness, TaC crystallite size, Raman spectrum, compressive stress, hardness, and elastic modulus. TEM measurements revealed the film base structure consisted of equiaxed cubic B1-TaC crystallites (< 5 nm) suspended in an a-C:H matrix. At the nanometer-scale, the film structure was lamellar with alternating TaC- and a-C:H-rich layers, the periodicity and distinctness of which were affected by deposition factors. The empirical property trends were interpreted with hypothesized growth mechanisms that incorporate elements of physical vapor deposition and plasma-enhanced chemical vapor deposition.

Ultra high vacuum physical vapor deposition is used to deposit thin films of varying yttrium:aluminum and hafnium:aluminum concentrations on H-terminated silicon(100) and oxidized ex-situ at several temperatures. X-ray Photoelectron Spectroscopy is used to analyze the surface composition of the films and electrical properties were evaluated using capacitance-voltages measurements with aluminum electrodes. The diffusion of silicon into the dielectric films is decreased with high concentrations (>78%) of aluminum. However, at high concentrations of aluminum a relatively thick interfacial oxide layer is formed. The flatband voltage shifted from –0.18V to –0.78V for the hafnium oxide films and –1.22V to –1.18V for yttrium oxide films. The flatband voltage shifted from –0.55V to –0.61V for 70% Hf:Al mixture and –0.78V to –0.76V for 42%Y:Al mixture. These flatband voltage shifts indicate that hafnium based mixtures are more sensitive to thermal treatments than yttrium based mixtures. Also, capacitance-voltage measurements show the ability to tune the flatband voltage and possibly vary the rate of silicon oxidation (tune equivalent oxide thickness) by aluminum alloying.

The increase in electrical conductivity of silica fiber yarn by the continuous deposition of titanium was experimentally evaluated. A system was developed for the continuous fabrication of the titanium coated yarn in a magnetron sputtering system. The bending stress in a coated fiber and preliminary coating experiments were used to evaluate the design for non-destructive transportation of the coated yarn. The electrical resistance was shown to decrease with increasing deposition times and increasing power levels. Increasing the number of contact points between adjacent segments of yarn was also shown to decrease the electrical resistance of a bundle of yarn segments.