This thesis reports a medium energy ion scattering investigation (MEIS) of platinum, palladium, and rhodium deposited upon the copper (110) surface using 100 keV hydrogen ions. The Daresbury National MEIS facility was used to take blocking curve and energy profiles of the structure formed by e-beam deposition of various thicknesses of platinum, palladium, and rhodium upon an atomically clean and ordered copper (110) crystal face. Quantitative analysis was conducted using an in-house version of the IGOR macro widely used within the MEIS community, adapted to analyse these systems. Sub-monolayer deposits of palladium and platinum were found to preferentially occupy subsurface sites, predominantly in the second layer below a copper first layer. This process occurred at room temperature. The interlayer separation between the deposited species and first layer copper were found in all three cases, being 1.21±0.04 Å for platinum, 1.17±0.06 Å for palladium and 1.16±0.06 Å for rhodium. These are contractions when compared to bulk interlayer spacing for copper which is 1.278 Å but are comparable to the first interlayer spacing from literature for relaxed copper which is 1.18 Å. A c(2x2) LEED pattern was observed in the case of the 0.3 ML platinum deposit which is an interesting comparison to the (1x2) reconstruction observed for sub-monolayer palladium in some literature sources. Upon annealing, the deposited species were observed to occupy third and fourth layer sites despite the temperature not being sufficient for diffusion deeper into the copper substrate. A process of burying through substrate adatom diffusion upward onto step edges is suggested as an energetically favoured process.

Physicists are interested in understanding the processes of nature. Within the field of Solid State Physics the characterisation of materials and the measurement of their properties is the first step towards identifiying new and interesting areas of scientific activities. The electrical resistivity of conductive materials is an important property which provides information about the electronic behaviour of the material. An elegant method to determine this characteristic is the measurement without using electrical contacts. Such a method avoids a whole set of experimental problems connected with the physics of electrical contacts to the sample. This Master-thesis gives an introduction into this experimental technique. A detailed theoretical description is developed. The experimental activity has involved the design, construction and testing of the apparatus. In the process of testing the method novel aspect emerged: The measurement at resonance point. These measurements can yield separate values for two different physical quantities: the electrical resistivity e and the magnetic susceptibility x. The innovation of this project is the simultaneous characterisation of both values for the material under investigation. The report starts by giving the theoretical background within which the first part of the detailed theoretical predictions are discussed. The second part contains experiments and a description of the experimental set-up. This design is the result of a long period of optimisation and testing. The working of the apparatus is demonstrated by the measurement of some samples.

Over the past number of years multiple frequency capacitively coupled plasmas have achieved widespread usage in plasma based nano-fabrication. However,the control of charged particle dynamics in such discharges is often limited by poor understanding of the non-linear coupling between the frequencies used. This is particularly true for plasmas produced in molecular gases. such as oxygen. where long-lived reactive neutral species can significantly affect the dynamics of charged particles. As these gases are used frequently in industry. it is crucial to achieve better understanding of their characteristics under multiple frequency excitation. In order to understand the dynamics of non-linear frequency coupling. this work proposes a novel dual frequency excitation scheme utilizing odd harmonics. The odd harmonic approach has been studied systematically utilizing both numerical simulations and experiments in plasmas produced in molecular oxygen gas. Through these Investigations it has been demonstrated that the frequencies used and the ratio to which they contribute to the resultant voltage waveform have significant influence over the final plasma parameters. This occurs through electron heating and ionization mode transitions which are non~linearly dependent upon the frequency contributions to the overall voltage waveform. A specific scheme for controlling the ion bombardment energy and ion flux to the substrate in Industrial plasma applications. using frequencies of 13.56 MHz and 40.68 MHz has been proposed. It has been predicted. through numerical simulations. and confirmed through experimental measurements. that the proposed scheme offers enhanced control of plasma properties over a wide parameter range. Furthermore. a critical benchmark study has been performed by undertaking a quantitative comparison between the results of state-of-the-art numerical simulations and experimental data. This has identified areas where further improvement in the understanding and modelling of oxygen plasmas is required in order to utilize numerical simulations in a truly quantitative manner for process design and control.

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Energy security and supply is a key problem for the UK in the coming years. Photovoltaics have an important role to play in this. In order for demand to be met, continued research into new materials and methods of production is necessary. By modelling deposition techniques using classical molecular dynamics (MD), an atomistic scale understanding can be obtained. Combining this with long time scale dynamics (LTSD) techniques allows us to also model diffusion and surface growth over realistic time scales. The LTSD technique applied throughout this project is an on-the-fly Kinetic Monte Carlo (otf-KMC) method, which determines diffusion pathways and barriers, in parallel, with no prior knowledge of the involved transitions. These simulation techniques allow parameters such as deposition energy, substrate bias and plasma pressure to be easily changed to gain understanding of their effects. During this project, growth via industrial scale deposition techniques has been simulated, including evaporation (thermal and electron beam), ion-beam assisted evaporation and reactive magnetron sputtering. Metal thin films, of interest due to their uses in reflectors in concentrator photovoltaics, electrical conductors in the monolithic interconnect processes and back contacts, were investigated using otf-KMC. Ag and Al film growth was simulated for around 0.3 seconds of real time. It was found that Ag has the ability to grow smooth surfaces, using several mechanisms including multiple-atom concerted motion, exchange mechanisms, and damage and repair mechanisms. Ag (111) and (100) surfaces grew dense, complete and crystalline films when sputtering was simulated, however, evaporation deposition produced incomplete layers. The inclusion of Ar in the ion-beam assisted evaporation of Ag (111) aided growth by transferring extra energy to the surface allowing increased diffusion and atomic mixing. Al (111) and (100), however, show different patterns. Growth by evaporation deposition and magnetron sputtering actually produced very similar results. The inclusion of the ion-beam assist on the (111) surface actually damaged the film, producing subsurface Ar clusters where Al atoms were displaced, creating voids throughout the film. Otf-KMC methods enabled the investigation of specific mechanisms allowing film growth and a very important transition enabling the smooth and complete Al film growth was found to be the Ehrlich-Schwoebel (ES) barrier. The ES barrier involves an atom dropping off a step edge of an island and this barrier was found to be much smaller for the Al surfaces, therefore allowing the more complete growth from both evaporation and sputtering. Metal oxides are also of great interest in the photovoltaic industry. The rutile TiO$_2$ (110) surface was investigated using single point depositions, high temperature MD and otf-KMC. Otf-KMC enabled the simulation for up to 9 seconds of real time, totally inaccessible using traditional simulation methods. Results concluded that the evaporation deposition process produced a void filled, incomplete structure, even with the use of a low energy ion-beam assist, this material is of interest for dye-sensitised solar cells where a dye is injected into the voids. Sputtering, however, produced dense and crystalline film, which is much more applicable to anti-reflective coatings where a crystalline structure is required. Mechanisms which enabled crystalline rutile to form were also investigated, highlighting Ti interstitial annealing in the presence of an O rich surface as an important rutile growth mechanism. ZnO, an inorganic compound with many uses including transparent conductive oxides, is investigated in the most stable wurtzite phase. The O-terminated (000$\bar{1}$) polar surface was used as the substrate for otf-KMC growth simulations, where around 1 second of real time was simulated. Evaporation deposition of a stoichiometric distribution of deposition species was found to produce the best quality film, however, a phase boundary was observed where an area of zinc blende forms within the wurtzite. Sputtering resulted in a denser, more complete and crystalline structure due to the higher deposition energy of arriving species, similar to the TiO$_2$ results. Post-annealing at 770K did not allow complete recrystallisation, resulting in films with stacking faults where monolayers formed in the zinc blende phase. Annealing at 920K, however, in some cases enabled the complete recrystallisation of films back into the wurtzite structure. Although, the higher annealing temperature did not always enable recrystallisation and in some cases both wurtzite and zinc blende phases existed in the same layer, resulting in a phase boundary. An important mechanism for the nucleation of ZnO growth was found to be the formation and vibration of Zn$_x$O$_y$ strings on the surface, which after hundreds of milliseconds formed the desired hexagonal structure. Combining MD and otf-KMC enabled the simulation of systems over very large time scales which were previously totally inaccessible. Key mechanisms occurring during the growth of metals and metal oxides were investigated, providing a much more precise understanding of how growth occurs. It is clear from the work that the deposition technique used plays a significant role on the resulting film quality and surface morphology and we are now able to provide an insight into the optimum conditions under which complete, crystalline layers can form.

Micromixing phenomena (i.e. mixing at molecular level) play a very important role in the chemical industry when the time scale of the chemical reaction involved have the same magnitude or smaller than the time scale of mixing process. The study of micromixing is very critical to the understanding of important processes such as polymerization, precipitation, crystallization and competing fast chemical reactions. It has long been recognised that the intense mixing characteristics of thin films in the spinning disc reactor (SDR), play an important role in improving the selectivity, yield, and quality of final products of a chemical reaction. However, to date, there has been no systematic study of micro and macro mixing in SDR thin films. The first part of this study reports on the fundamental study undertaken to characterise micromixing in the thin films formed in 10 cm and 30 cm SDRs operating under a wide range of operating conditions. A well-established parallel-competitive reaction test scheme was adopted to quantify micromixing in terms of the segregation index (Xs) or micromixedness ratio (α), the power dissipation (ε) and micromixing time(tm). The micromixing data obtained from 10cm and 30cm SDRs were benchmarked against both a 1.37 l conventional semi-batch reactor (SBR) and continuous tubular flow reactors in the form of narrow channels (NCRs) of 1.0 mm diameter and three different lengths namely 5 cm, 10 cm and 15 cm (Y and T shape junctions). The effects of various operating parameters such as disc rotation rates, disc size, disc surface configurations, feed flowrates, feed distribution systems, liquid feed concentrations and viscosities were investigated. It was observed that, at an acid concentration of 1 M, the lowest segregation index of 0.05 was achieved for a feed of 0.001Ns/m2 viscosity at the highest flowrate of 5ml/s (corresponding to Refilm=72) and highest rotational speed of 2400 rpm in the 10cm diameter disc. Greatly improved micromixing was obtained on the larger disc of 30 cm diameter, especially at the lower Refilm of 15 and 42, in comparison to the smaller disc. Under optimised conditions, the micromixing time(tm) in the water-like film on the 30cm diameter disc was estimated to be as low as 0.3ms with corresponding power dissipation (ε) of 1025 W/kg. In contrast, the SBR could only achieve, under optimised conditions, segregation indices of no lower than 0.13 corresponding to a micromixing time of above 1ms with power dissipation of no more than about 21 W/kg. On the other hand, the NCRs could only achieve, under optimised conditions, a micromixing time of about 19 ms corresponding to power dissipation (ε) of about 208 W/kg. Therefore, when compared with other mixing devices such as conventional SBRs or NCRs, the SDR is shown to give significantly better micromixing performance which highlights its potential as an alternative device for processes where a high degree of mixing is critically important. In the second part of this study, the residence time distribution (RTD) of the liquid flow in the 30 cm SDR was characterised for a range of operating conditions including disc rotational speeds, disc configuration (smooth vs. grooved), total flow rate of liquid and viscosity in order to determine the conditions for which plug flow profile became more prevalent in the SDR films. The dispersion number from the RTD results and Peclet number were also estimated for the purpose of further characterising the extent of axial dispersion in the thin film flow on the rotating disc. All the mentioned operating conditions were found to have a profound influence on the overall Mean Residence Time, ( ), variance, , dispersion number and Peclet number, (Pe). More specifically, the lowest value for the of 10.1 s was achieved for a feed of 0.001 Ns/m2 viscosity at the highest flowrate of 15ml/s and highest rotational speed of 1200 rpm on the smooth disc with corresponding of 2.16. The dispersion number and Pe were 0.010 and 100 respectively, showing that the degree of axial dispersion was very small. A considerable reduction in the dispersion number and Pe was observed when the smooth disc was replaced by grooved disc. Thus, under the above mentioned hydrodynamic conditions, whilst the was almost unchanged at 10.10 s on grooved disc, the corresponding variance of 1.03 was significantly lower, indicating even more reduced axial dispersion in the film on the grooved disc. This is further substantiated by dispersion number and Pe of 0.005 and 200 respectively. In general the RTD curves become narrower and the values of and decreased as the disc rotational speed and flowrates increased and as the feed viscosity decreased. For the given operating conditions used in this research, it was confirmed that the 30 cm SDR approaches plug-flow regime which had a positive influence on the micromixing intensity on the SDR.

Complex fluids are commercially- and industrially-important materials which exhibit ordering on scales much larger than atomic. Their usage is typically in non-equilibrium conditions, however traditional methods for measuring rheology are not appropriate for measuring samples with gradients present, such as temperature and concentration. In this work a safe and easy to use optical tweezer (OT) apparatus has been developed in order to facilitate the investigation of various systems during dilution or drying. In contrast to other OT setups, this equipment is safe to use without laser goggles or interlocked rooms, yet still allows full access to the microscope. Proof-of-concept experiments are performed on aqueous poly (ethylene oxide) (PEO) solutions to demonstrate the changes in viscosity and concentration over time, and the OT is then used in a rheological investigation into a commercially-relevant wormlike micelle (WLM) system, in conjunction with Diffusing Wave Spectroscopy (DWS) and traditional bulk rheology. It is shown for the first time that equimolar (eM) SDS:CAPB WLM samples can be considered ‘model’ systems, and form close approximations of Maxwellian systems on the addition of extra salt or surfactant above 0.1eM. The effect of an uncharged polymer (PEO 4M MW) on this WLM network structure was subsequently investigated; its effects are consistent with current theories of polymer-surfactant interactions. The effect of a conditioning polyelectrolyte on the network structure was also studied; its effect was highly dependent on surfactant and electrolyte concentration, but hinted at the previously unreported behaviour of a polyelectrolyte initiating micellar branching. A precursor investigation into evaporation of sessile droplets of aqueous PEO solutions is presented last, reporting a previously unseen droplet evaporation regime in which the solid deposits grow to nearly twice their starting height. This research concludes that the growth phenomena is due to the unusual solvation mechanism of PEO, and a predictive theory is presented in support of this.

The spontaneous capillary-driven filling of micro channels is important for a wide range of applications. Reporting for the first time for vertically mounted open top channels, in this work the theory for capillary rise in channels of rectangular cross-section has been tested and verified, taking into account the effects of surface topography assuming a Wenzel state. The theory has been tested via capillary rise experiments using polydimethylsiloxane oils of viscosity 96.0, 48.0, 19.2 and 4.8 mPa s within the 400μm and 600μm closed square glass tubes and SU8 open top smooth walled rectangular cross-section channels having width 400μm and 600μm and depth 135μm. It has been shown that capillary rise heights in plane open top walled channels (with roughness factor of 1) can be fitted using the exact numerical solution and that these are similar to fits using the analytical visco-gravitational solution. The viscous friction contribution was found to be higher than predicted by theory assuming a non-rigidified liquid–air boundary, but far below that for a rigidified boundary, which is recently reported for imbibition into horizontally mounted open micro channels. It has also been observed that fingers of liquid spreading along the internal edges of the smooth walled channels in advance of the main body of liquid consistent with wetting expectations. These fingers were observed to be thicker and larger in size for wider and shallower channels. The data from the experiments in which prominent liquid fingers were observed was fitted using the visco-gravitational approximation and it was found that the rise heights were far less than the expected heights especially in wider and shallower channels. In SU8 open top channels, Wenzel roughness was introduced on the walls in the form of triangular steps to provide additional surface area to rising liquid. The experiments were performed with 300-350μm deep open top rough walled SU8 channels of width 400μm and 600μm using PDMS oils of viscosity 19.2, 48 and 96 mPas. The equilibrium height was observed to be increased in channels with greater roughness. The data was fitted using the visco-gravitational solution and the fitted height was found to be increased with roughness but not as much as expected from a Wenzel consideration. This deviation of fitted height from its predicted value was found to be more in the channels with greater roughness factors. The stick-slip behaviour of the liquid fingers was observed along the roughness steps.