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This thesis details the use of x-ray photoelectron spectroscopy to monitor in-situ surface processing of solid surfaces in real-time. The processing methods investigated were annealing, deposition of thin organic films and exposure to oxygen and hydrogen produced by in-situ microwave plasmas. Three solid surfaces were investigated; metals, diamond and zinc oxide. Clean copper and gold were annealed up to 1000 K while monitoring with real-time XPS. A temperature-dependent shift of the Cu 2p3/2 and Au 4f7/2 core-level to lower binding energy was measured, -1.29 ± 0.04 meV/10 K and -2.36 ± 0.01 meV/10 K respectively. The shift was identified as being due to a thermal expansion of the lattice. The removal of argon ion induced damage to the copper surface was monitored in real-time and a critical temperature of 680 ± 20 K for the removal of the damage was measured. The formation of an interface between aluminium and copper phthalocyanine was monitored in real-time. Hydrogen and oxygen terminated (111) natural diamond surfaces were prepared in-situ and surface reconstruction by annealing up to 1200 K was monitored in real-time. Large reversible shifts to core-level binding energies were attributed to a surface photovoltage that was persistent at high temperature on the hydrogen and oxygen terminated surfaces. A model of the surface photovoltage is given where the bulk resistance of the diamond is identified as sustaining the photovoltage at elevated temperature. The zinc oxide (0001) surface was found to have a temperature-dependent core-level binding energy shift that was fully reversible up to 900 K and symmetric with cooling. The shift was attributed to a diffusion of oxygen vacancies from the bulk into the sub-surface. The zinc oxide (0001) surface was found to exhibit different temperature dependence to the (0001) surface that was fully reversible up to 700K but not symmetric with cooling. The shift was attributed to an additional disruption to stabilizing charge transfer between the polar surfaces. The formation of interfaces between the (0001) surface with copper phthalocyanine and C60 were monitored in real-time.

No description available.

<p><p>The adsorption of proteins to solid surfaces has been extensively investigated during the past 20-30 years. The knowledge can be applied in biotechnological applications in for example immunoassays and biosensors. Human carbonic anhydrase II is a widely studied protein and the CO₂-activity makes it an interesting candidate for biotechnological purposes. To make this possible, the factors affecting the adsorption of proteins have to be mapped. The stability of the protein is under great influence of the adsorption and the protein tends to undergo conformational changes leading to a molten globule like state upon adsorption. The stability of a protein also affects the extent of conformational changes and the nature of the adsorption. A more stable protein, adsorbs with less structural changes as a consequence of adsorption, and desorbs from the surface more rapidly than a less stable one. Also the hydrophobicity, charge and area of the surface are affecting the interaction with the protein. Still, the same adsorption pattern is noticed for the same protein at different surfaces, leading to the conclusion that the properties of the protein affect the interaction, rather than the properties of the surface. Biosensors containing carbonic anhydrase have been developed. These make measurement and detection of zinc ions possible. To be able to use carbonic anhydrase as a potential agent in biotechnology, attached to solid surfaces, the protein has to be biotechnologically engineered to get a more stable structure, or else the denaturation will destroy this possibility.</p></p>

The adsorption of proteins to solid surfaces has been extensively investigated during the past 20-30 years. The knowledge can be applied in biotechnological applications in for example immunoassays and biosensors. Human carbonic anhydrase II is a widely studied protein and the CO2-activity makes it an interesting candidate for biotechnological purposes. To make this possible, the factors affecting the adsorption of proteins have to be mapped. The stability of the protein is under great influence of the adsorption and the protein tends to undergo conformational changes leading to a molten globule like state upon adsorption. The stability of a protein also affects the extent of conformational changes and the nature of the adsorption. A more stable protein, adsorbs with less structural changes as a consequence of adsorption, and desorbs from the surface more rapidly than a less stable one. Also the hydrophobicity, charge and area of the surface are affecting the interaction with the protein. Still, the same adsorption pattern is noticed for the same protein at different surfaces, leading to the conclusion that the properties of the protein affect the interaction, rather than the properties of the surface. Biosensors containing carbonic anhydrase have been developed. These make measurement and detection of zinc ions possible. To be able to use carbonic anhydrase as a potential agent in biotechnology, attached to solid surfaces, the protein has to be biotechnologically engineered to get a more stable structure, or else the denaturation will destroy this possibility.

This thesis addresses the evolution of nanoscale ripple patterns on solid surfaces during low-energy ion sputtering. Particular attention is paid to the long-time regime in which the surface evolution is dominated by nonlinear processes. This is explored in simulation and experiment. In numerical simulations, the influence of anisotropy on the evolution of the surface patterns in the anisotropic stochastic Kuramoto-Sivashinsky (KS) equation with and without damping is studied. For a strong nonlinear anisotropy, a 90 rotation of the initial ripple pattern is observed and explained by anisotropic renormalization properties of the anisotropic KS equation. This explanation is supported by comparison with analytical predictions. In contrast to the isotropic stochastic KS equation, interrupted ripple coarsening is found in the presence of low damping. This coarsening seems to be a nonlinear anisotropy effect that occurs only in a narrow range of the nonlinear anisotropy parameter. Ex-situ atomic force microscopy (AFM) investigations of Si(100) surfaces sputtered with sub-keV Ar ions under oblique ion incidence show the formation of a periodic ripple pattern. This pattern is oriented normal to the direction of the ion beam and has a periodicity well below 100 nm. With increasing ion fluence, the ripple pattern is superposed by larger corrugations that form another quasi-periodic pattern at high fluences. This ripple-like pattern is oriented parallel to the direction of the ion beam and has a periodicity of around one micrometer. Interrupted wavelength coarsening is observed for both patterns. A dynamic scaling analysis of the AFM images shows the appearance of anisotropic scaling at large lateral scales and high fluences. Based on comparison with the predictions of different nonlinear continuum models, the recent hydrodynamic model of ion erosion, a generalization of the anisotropic KS equation, is considered as a potentially powerful continuum description of this experiment. In further in-situ experiments, the dependence of the dynamic scaling behavior of the sputtered Si surface on small variations of the angle of incidence is investigated by grazing incidence small angle X-ray scattering (GISAXS). A transition from strongly anisotropic to isotropic scaling is observed. This indicates the presence of at least two fixed points in the system, an anisotropic and an isotropic one. The dynamic scaling exponents of the isotropic fixed point are in reasonable agreement with those of the Kardar-Parisi-Zhang (KPZ) equation. It remains to be seen whether the hydrodynamic model is able to show such a transition from anisotropic to isotropic KPZ-like scaling.

The research topic of liquid drop interaction with solid surfaces is being actively pursued to gain in-depth understanding of several practical cases such as the impingement of fuel spray droplets on surfaces like combustion chamber walls and piston top of an I.C. engine, heat transfer via spray impingement, ink-jet printing, etc. In most of the cases, the physical and flow properties of the liquid drop/spray may be fixed whereas it may be possible to tune the physical and chemical properties of the solid surface thereby enabling to control the interaction process. The present work belongs to the study of liquid drop-solid surface interaction process with special focus on the physical characteristics of solid surface. The thesis reports an experimental study of the dynamics of millimetric water drops impacted onto the junction of dual-textured substrates made of stainless steel. The dual-textured substrates consisted of hydrophobic (textured) and hydrophilic (smooth) portions. The entire textured portion comprised of parallel groove-like structures separated by solid posts/pillars. Two dual-textured substrates, which differ only in the geometry of their textured portions, were employed. Surface topography features of the dual-textured substrates were characterized using scanning electron microscopy (SEM) and optical surface profilometer. The wetting behavior of the textured and smooth portions of the substrates, quantified in terms of the equilibrium, advancing, and receding contact angles adopted by a water drop on the surface portions, was characterized experimentally through the methods of sessile drop formation, captive needle volume addition, and drop evaporation under ambient conditions. Free-falling water drops were impacted from a height onto the junction between the hydrophobic (textured) and hydrophilic (smooth) portions of the dual-textured substrates. A set of twelve different impact experiments were conducted on each of the target substrates with drop impact velocity (Uo) ranging from 0.37 to 1.50 m/sec. The dynamics of drop impact were captured using a high speed camera with frame rate ranging from 3000 to 10000 frames per second. From the captured frames, the temporal variations of the impacting drop parameters were measured using a MATLAB-assisted program. A systematic analysis of experimental data revealed the existence of four distinct regimes of drop dynamics on the dual-textured substrate: (a) early inertia driven drop spreading, (b) primary drop receding, (c) secondary spreading on the hydrophilic portion, and (d) final equilibrium regimes. It is shown that the drop impact dynamics during the early inertia driven impact regime remains unaffected by the dual-texture feature of the substrate. A larger retraction speed of impacting drop liquid observed on the hydrophobic portion of the substrate makes the drop liquid on the higher wettability/hydrophilic portion to advance further (secondary drop spreading). The net horizontal drop velocity towards the hydrophilic portion of the dual-textured substrate decreases with increasing drop impact velocity. The available experimental results suggest that the movement of bulk drop liquid away from the impact point during drop impact on the dual-textured substrate is larger for the impact of low inertia drops. A semi-empirical model, based on the balance of the wettability gradient, contact angle hysteresis, and viscous forces acting on impacted drop liquid on the substrate, is formulated to predict the movement of bulk drop liquid away from the impact point (ξ). A satisfactory comparison between the model predictions and the experimental measurements is reported for the variation of ξ with Uo.

This thesis addresses the evolution of nanoscale ripple patterns on solid surfaces during low-energy ion sputtering. Particular attention is paid to the long-time regime in which the surface evolution is dominated by nonlinear processes. This is explored in simulation and experiment. In numerical simulations, the influence of anisotropy on the evolution of the surface patterns in the anisotropic stochastic Kuramoto-Sivashinsky (KS) equation with and without damping is studied. For a strong nonlinear anisotropy, a 90 rotation of the initial ripple pattern is observed and explained by anisotropic renormalization properties of the anisotropic KS equation. This explanation is supported by comparison with analytical predictions. In contrast to the isotropic stochastic KS equation, interrupted ripple coarsening is found in the presence of low damping. This coarsening seems to be a nonlinear anisotropy effect that occurs only in a narrow range of the nonlinear anisotropy parameter. Ex-situ atomic force microscopy (AFM) investigations of Si(100) surfaces sputtered with sub-keV Ar ions under oblique ion incidence show the formation of a periodic ripple pattern. This pattern is oriented normal to the direction of the ion beam and has a periodicity well below 100 nm. With increasing ion fluence, the ripple pattern is superposed by larger corrugations that form another quasi-periodic pattern at high fluences. This ripple-like pattern is oriented parallel to the direction of the ion beam and has a periodicity of around one micrometer. Interrupted wavelength coarsening is observed for both patterns. A dynamic scaling analysis of the AFM images shows the appearance of anisotropic scaling at large lateral scales and high fluences. Based on comparison with the predictions of different nonlinear continuum models, the recent hydrodynamic model of ion erosion, a generalization of the anisotropic KS equation, is considered as a potentially powerful continuum description of this experiment. In further in-situ experiments, the dependence of the dynamic scaling behavior of the sputtered Si surface on small variations of the angle of incidence is investigated by grazing incidence small angle X-ray scattering (GISAXS). A transition from strongly anisotropic to isotropic scaling is observed. This indicates the presence of at least two fixed points in the system, an anisotropic and an isotropic one. The dynamic scaling exponents of the isotropic fixed point are in reasonable agreement with those of the Kardar-Parisi-Zhang (KPZ) equation. It remains to be seen whether the hydrodynamic model is able to show such a transition from anisotropic to isotropic KPZ-like scaling.

Detergents are broadly used in our everyday life for cleaning and washing procedures. They are however, a source of water pollution and can have a negative effect on human health and the environment. To reduce their negative impact, a new trend of using only pure water for washing and cleaning applications is being implemented. However, a scientific basis needs to be established first, as the mechanisms and the effectiveness of this method are not fully understood. In this work, we aim to investigate the effect of water purity on the removal of oil from surfaces and the stability of colloidal systems. To do that, two purified water grades are compared with non-purified tap water and 10 mM NaCl solution. Results from measurement of oil film mass before and after water contact and Quartz Crystal Microbalance with Dissipation (QCM-D) indicate that purified water grades can wash a surface more efficiently than non-purified water grades. Contact angle measurements show that pure water facilitates the cleaning process while spreading of oil on plastic surfaces indicates that electrostatic interactions have an important role in the system. Visual observations of o/w emulsions, show that purified water grades redisperse the oil better. We hypothesize that the mechanism behind the cleaning and washing without detergents relies on the electrostatic interactions. To further investigate the effect of salt on cleaning mechanisms, we performed zeta potential measurements. Results indicate that salt has a negative effect on the stability of the particles.

Dynamic behavior of impacting water drops on superhydrophobic solid surfaces provides important details on the stability/durability of such solid surfaces. Multi-scale surface roughness combined with a layer of low energy chemical is an essential surface modification process followed to create superhydrophobic capabilities on solid surfaces. The present work aims at studying the effect of low energy surface coating on droplet impact dynamics by carrying out experiments of water drop impacts on rough solid surfaces with and without chemical modification. A group of six aluminium alloy (Al6061) surfaces (three pairs) are prepared. Roughness, characterized in terms mean surface roughness, Ra, is introduced to these metallic surfaces using sand-paper polishing, electric discharge machining (EDM), and chemical based surface etching process. Low energy surface layer is laid on the rough surfaces by coating NeverWet hydrophobic solution, octadecyl-trichloro-silane (OTS), and perfluorodecyltricholorosilane (FAS-17). The impact dynamics of water drops is analyzed by capturing high speed videos for a range of drop Weber number from 1 to 570 and the salient features of drop impact process on the coated rough surfaces are compared with the corresponding uncoated rough surfaces. A one-to-one comparison on the spreading, fingering, receding, and final equilibrium of impacting drops on the coated and uncoated target surfaces is presented. Upon coating NeverWet, the original surface features of the base aluminium surface are completely covered by the hydrophobic coating material resulting in a fresh top surface layer. The outcomes as well as the bounce-off characteristics of impacting water drops on the coated surface are comparable to those observed on lotus leaf. The surface morphology features of rough aluminium surfaces coated with OTS and FAS-17 are comparable to those of the corresponding uncoated surfaces. The quantitative measurements on primary spreading and maximum spread factor of impacting drops are largely unaffected by the presence of low energy chemical coating. The dominant effect of surface coating is seen on the receding of impacting drops and hence the final drop configuration. This behavior is more prominently seen on EDM fabricated rough surface (larger Ra) combined with OTS coating than that on etching based rough surface (smaller Ra) combined with FAS-17 coating highlighting the dependence of coating effect with roughness features.