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The aim of the presented work was to deposit cubic boron nitride thin films by magnetron sputtering under simultaneous stress relaxation by ion implantation. An in situ instrument based on laser deflectometry on cantilever structures and in situ ellipsometry, was used for in situ stress measurements. The characteristic evolution of the instantaneous stress during the layered growth of cBN films observed in IBAD experiments, could be reproduced for magnetron sputter deposition. To achieve simultaneous stress relaxation by ion implantation, a complex bipolar pulsed substrate bias source was constructed. This power supply enables the growth of cBN thin films under low energy ion irradiation (up to 200 eV) and, for the first time, the simultaneous implantation of ions with an energy of up to 8 keV during high voltage pulses. It was demonstrated that the instantaneous stress in cBN thin films can be released down to -1.1 GPa by simultaneous ion bombardment during the high voltage pulses. A simultaneous stress relaxation during growth is possible in the total investigated ion energy range between 2.5 and 8 keV. These are the lowest ion energies reported for the stress relaxation in cBN. Since such a substrate bias power supply is easy to integrate in existing process lines, this result is important for industrial deposition of thin films, not only for cubic boron nitride films. It was found that the amount of stress relaxation depends on the number of atomic displacements (displacements per atom: dpa) that are induced by the high energy ion bombardment and is therefore dependent on the ion energy and the high energy ion flux. In practise, this means that the stress relaxation is controlled by the product of the pulse voltage and the pulse duty cycle or frequency. The cantilever bending measurements were complemented on microscopic scale by x-ray diffraction (XRD). The analysis of the cBN (111) lattice distances revealed a pronounced biaxial compressive state of stress in a non-relaxed cBN film with d(111) being larger in out-of-plane than in in-plane direction. Post deposition annealing at 900 ° C of a sample with an ion induced damage of 1.2 dpa, resulted in a complete relaxation of the lattice with equal in-plane and out-of-plane lattice parameters. In the case of medium-energy ion bombardment, the in-plane and out-of-plane lattice parameters approach the value of the annealed sample with increasing ion damage. This is a clear evidence for stress relaxation within the cBN lattice. The stability of cBN under ion bombardment was investigated by IR spectroscopy and XRD. The crystalline cBN was found to be very stable against ion irradiation. However a short-range ordered, sp3/sp2 - mixed phase may exist in the films, which could be preferably converted to a sp2 -phase at high damage values. From the analysis of the near surface region by XANES, it can be concluded the stress relaxation by the energetic ion bombardment is less at the surface than in the bulk film. This is explained with the dynamic profile of the ion induced damage, that reaches the stationary bulk value in 15-20 nm depth, whereas it is decreasing towards the surface. This fits with the results that the stress relaxation is dependent on the amount of ion induced damage. Comparing the results from substrate curvature measurement, XRD, XANES, and IR spectroscopy possible mechanisms of stress relaxation are discussed. Concluding the results, it can be stated that using simultaneous ion implantation for stress relaxation during the deposition it is possible to produce BN films with a high amount of the cubic phase and with very low residual stress.

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The vast majority of oil and gas reserves are trapped in fractured carbonate reservoirs. Most carbonate reservoirs are naturally fractured, with fractures ranging from millimeter- to kilometer-scale. These fractures create complex flow behaviors which impact reservoir characterization, production performance, and, eventually, total recovery. As we know, bridging the gas from plug to near-wellbore, eventually to field scales, is a persisting challenge in modeling Naturally Fractured Reservoirs (NFRs). This dissertation will focus on assessing the fundamental flow mechanisms in fractured rocks at the plug scale, understanding the governing upscaling parameters, and ultimately, developing fit-for-purpose upscaling tools for field-scale implementation. In this dissertation, we first focus on the upscaling of rock fractures under the laminar flow regime. A novel analytical model is presented by incorporating the effects of normal aperture, roughness, and tortuosity. We then investigate the stress-dependent hydraulic behaviors of rock fractures. A new and generalized theoretical model is derived and verified by a dataset collected from public experimental resources. In addition, an efficient coupled flow-geomechanics algorithm is developed to further validate the proposed analytical model. The physics of matrix-fracture interaction and fluid leakage is modeled by a high-resolution, micro-continuum approach, called extended Darcy-Brinkman-Stokes (DBS) equations. We observe the back-flow phenomena for the first time. Machine learning is then implemented into our traditional upscaling work under complex physics (e.g., initial and Klinkenberg effects). We finally consolidate the lab-scale upscaling tools and scale them up to the field scale. We develop a fully coupled hydro-mechanical model based on the Discrete-Fracture Model (DFM) in fractured reservoirs, in which we incorporate localized effects of fracture roughness at the field-scale.

No / The current work was undertaken to assess suitability of liquid crystalline phase for engineering of lactose crystals and their utility as a carrier in dry powder inhalation formulations. Saturated lactose solution was poured in molten glyceryl monooleate which subsequently transformed into gel. The gel microstructure was analyzed by PPL microscopy and SAXS. Lactose particles recovered from gels after 48 h were analyzed for polymorphism using techniques such as FTIR, XRD, DSC and TGA. Particle size, morphology and aerosolisation properties of prepared lactose were analyzed using Anderson cascade impactor. In situ seeding followed by growth of lactose crystals took place in gels with cubic microstructure as revealed by PPL microscopy and SAXS. Elongated (size approximately 71 mum) lactose particles with smooth surface containing mixture of alpha and beta-lactose was recovered from gel, however percentage of alpha-lactose was more as compared to beta-lactose. The aerosolisation parameters such as RD, ED, %FPF and % recovery of lactose recovered from gel (LPL) were found to be comparable to Respitose(R) ML001. Thus LC phase (cubic) can be used for engineering of lactose crystals so as to obtain particles with smooth surface, high elongation ratio and further they can be used as carrier in DPI formulations.

Ultra-thin solar cells that incorporate earth-abundant and non-toxic materials are promising candidates in the endeavor toward sustainable energy harvesting. Methods to counteract the inevitable low absorption of thinner semiconductor layers are of high interest and have raised considerable attention in the research society. In an attempt to increase the absorption of these types of assemblies, optical coupling effects between the localized surface plasmon resonances (LSPR) of disordered Au nanostructures and a Fabry-Pérot cavity were studied using a previously established absorber/spacer/reflector stack. The disordered Au array was fabricated by evaporating a thin Au film on a substrate with a 55 nm SiO2 dielectric spacer and a 100 nm Al reflecting film, followed by thermal annealing. Nominal Au film thicknesses in the range of 5-25 Å and annealing temperatures of 200-500 oC were investigated. In situ spectroscopic ellipsometry measurements during the subsequent atomic layer deposition (ALD) of tin monosulfide (SnS) allowed analysis of how the optical properties of the SnS/Au absorber layer changed as a function of the growing SnS layer thickness. By employing the Transfer Matrix Method with the estimated optical properties from the in situ analysis, the absorptance of the absorber/spacer/reflector stacks was simulated as a function of the spacer thickness, revealing any signs of the characteristic anti-crossing behavior. It was discovered that a nominal Au film thickness of 25 Å, annealed at 450 oC, and coated with a SnS film of ∼13 nm primed toward the π-phase, resulted in strong optical coupling between the cavity mode and the LSPR. The energy difference at the avoided crossing in the specular reflectance measurement gave an estimated Rabi-splitting energy of 537 meV. This corresponded to about 40% of the original LSPR energy, placing itself within the ultra-strong coupling regime. To evaluate the relevance of the thin-layered structure in photovoltaic applications, more advanced computational methods are required to estimate the useful absorption that occurs in the SnS layer. Nevertheless, these results elucidate the realization of strong optical coupling effects between disordered Au nanostructures and a Fabry-Pérot cavity, and further the possibility of using scalable fabrication methods for this type of ultra-thin absorber/spacer/reflector stack.