This thesis presents a study of the intensified charge-coupled device (ICCD) imaging of pulsed laser ablated plumes. Two-dimensional imaging of laser ablated plumes is a very important diagnostic for PLD. ICCD array photography is a useful tool for imaging PLD. The images obtained using the standard technique are characterized and compared with ICCD images of an altered plume, ICCD images intentionally violating standard imaging procedures, and film thickness. The depth resolving properties of a pinhole was investigated with the intention of applying it to PLD plume imaging. This results in a more thorough understanding of the depth resolving property of a pinhole. The investigation leads to a theoretical improvement for the resolution in confocal microscopy.

A growing need for developing new multi-functional materials operating at microwave frequencies is demanding a better understanding of ferroelectric and ferrimagnetic materials and their combinations. Some of these materials exhibit tunable physical properties, giving an extra degree of freedom in the device design. New multifunctional ferroelectric and ferrimagnetic thin film structures are investigated in this dissertation research, in which dielectric and magnetic properties can separately be tuned over a certain frequency range. The materials of choice, Ba0.5Sr0.5TiO3 (BST) and BaFe12O19 (BaM), both well studied and used in many microwave applications, were prepared using rf magnetron sputtering and pulsed laser ablation. Thin-film bilayers, multilayers and composite thin films were grown on various substrates, and their underlying microstructure and crystallographic properties were analyzed and optimized. After identifying the most successful growth conditions,dielectric and magnetic properties were measured. Unusual features in magnetic hysteresis loops in both sputtered and laser ablated films grown under different conditions were observed. Microcircuits were fabricated using optical lithography and microwave properties and tunability were tested in the range 1-65 GHz.

This project focused on two aspects of magnetite thin films. The first was to find optimum parameters and conditions for deposition of stoichiometeric Magnetite films using pulsed laser deposition (PLD). The second aspect was the characterization of the magnetic and electrical properties in order to broaden the spectrum of understanding of PLD Magnetite films. These properties were also investigated in terms of the substrates on which the films were deposited. Discussed in this thesis are deposition parameters, structural characteristics, magnetic and electrical characteristics of the films in terms of different substrates and film thicknesses. The discussion consists of structural parameters obtained using X- ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), and electric properties such as resistance as a function of temperature and voltage dependence on the applied current. The magnetic properties measured were the magneto-resistance, M-H hysteresis loop, and magnetization as a function of temperature. The results obtained are then compared with pre-existing literature data. It will be shown that there is an impurity phase that may be seen when magnetite films are deposited on Sillicon dioxide substrates.

The growth of thin-film metal nitride materials from elemental metal targets by plasma-assisted pulsed laser deposition (PLD) has been explored and analysed. A new UHV PLD growth system has been installed and assembled and its system elements were calibrated. A series of GaN thin films have been grown to calibrate the system. In-situ RHEED indicated that the films were single crystal and that growth proceeded in a three-dimensional fashion. SEM images showed heavy particulation of film surfaces that was not in evidence for later refractory metal nitride films. This may be connected to the fact that Ga targets were liquid while refractory metals were solid. Most GaN films were not continuous due to insufficient laser fluence. Continuous films did not exhibit photoluminescence. HfN films have been grown by PLD for the first time. Films grown have been shown to have high reflectivity in the visible region and low resistivity. These factors, along with their crystal structure, make them suitable candidates to be used as back-contacts in GaN LEDs and could also serve as buffer layers to enable the integration of GaN and Si technologies. Growth factors affecting the films’ final properties have been investigated. Nitrogen pressure, within the operating range of the plasma source, has been shown to have little effect on HfN films. Substrate temperature has been demonstrated to have more influence on the films’ properties, with 500 °C being established as optimum. ZrN films have also been grown by PLD. Early results indicated that they exhibit reflectivities 50 % ± 5 % lower than those of HfN. However, further growth and characterisation would be required in order to establish this as a fundamental property of ZrN as nitride targets were mostly used in ZrN production. Single-crystal epitaxial GdN and SmN films have been produced by PLD. This represents an improvement in the existing quality of GdN films reported in the literature, which are mostly polycrystalline. In the case of SmN, these are the first epitaxial films of this material to be grown. Film quality has been monitored in-situ by RHEED which has allowed growth to be tailored to produce ever-higher crystal quality. Post-growth analyses by collaborators was also of assistance in improving film growth. Substrate temperatures and nitrogen plasma parameters have been adjusted to find optimum values for each. In addition, laser fluence has been altered to minimise the presence of metal particulates in the films, which interfere with magnetic measurements carried out in analyses. Capping layers of Cr, YSZ or AlN have been deposited on the GdN and SmN prior to removal from vacuum to prevent their degradation upon exposure to atmospheric water vapour. The caps have been steadily improved over the course of this work, extending the lifetime of the nitride films in ambient. However, they remain volatile and this may persist since water vapour can enter the film at the edge regardless of capping quality. Optical transmission has shown an onset of absorption at 1.3 eV for GdN and 1.0 eV for SmN.

With recent trends in miniaturization in the electronics sector, ferroelectrics have gained popularity due to their applications in non-volatile RAM. Taking one step further researchers are now exploring multiferroic devices that overcome the drawbacks of ferroelectric (FE) and ferromagnetic (FM) RAM’s while retaining the advantages of both. The work presented in this dissertation focuses on the growth of FE and FM thin film structures. The primary goals of this work include, (1) optimization of the parameters in the pulsed laser deposition (PLD) of FE and FM films and their heterostructures, (2) development of a structure-property relation that leads to enhancements in electric and magnetic polarizations of these structures, (3) investigation of doping on further enhancement of polarizations and coupling between the FE and FM layers. The materials of choice are La0.7Sr0.3MnO3 (LSMO) as the ferromagnetic and PbZr0.52Ti0.48O3 (PZT) as the ferroelectric component. Epitaxial thin film capacitors were grown using PLD. The work starts with the establishment of the optimum deposition conditions for PZT and goes on to describe results of attempts at performance enhancement and tuning using two methods. It is demonstrated that ferroelectric and ferromagnetic properties can be tuned by inserting a ferromagnetic buffer layer of CoFe2O4 (CFO) between PZT and LSMO. One of the key findings of this work was the anomalously high ferroelectric polarizations produced by lanthanum (La) doped PZT films. This work attempts to shine light on a possible mechanism that leads to such high enhancements in polarization.

III-nitride mainly GaN semiconductors are the most important materials for a wide range of applications, in particular high-power devices, due to the tunable direct bandgap, their chemical, and thermal stability. However, their growth on suitable substrates is still problematic, and low UV GaN efficiency hinders the efforts aimed at improving the performance of emitting devices. This dissertation presents novel growth and device fabrication methods capable of overcoming these issues using different novel strategies. The work reported in this dissertation comprises five parts. The first two parts demonstrate a new low-cost pulsed laser deposition (PLD)-based strategy for large-scale applications. This was developed to grow high-quality dislocation-free GaN NWs epitaxially on any bulk, flexible, or two-dimensional (2D) substrates without a catalyst, irrespective of the lattice mismatch or type of the substrate. As part of the work reported here, Si, p-GaN, Ga2O3, sapphire, graphene, MXene, and transition-metal dichalcogenide (TMD) substrates were utilized. Also, the adopted growth mechanisms are discussed, along with the advanced structural and optical characterizations. Advanced structural and optical characterizations further confirm the growth mechanism and demonstrate the superior optical and structural quality of GaN NWs. In the third part, a novel multiple quantum wells (MQWs)-based structure grown on the NWs is described, indicating that these NWs can be used as a template to grow III-nitride-based devices. In the fourth part of the work, the significance of these GaN NWs is further demonstrated by reporting on the fabrication of a high-performance self-powered broadband photodetector incorporating these NWs hybridized by two perovskite types: organic/inorganic as well as all-inorganic perovskites (CH3NH3PbI3 and CsPbBr3), revealing two different self-powered photodetector characteristics with high photo-responsivity at 0V. In the last part of this work, the focus is given to a new environmentally friendly strategy to enhance the device UV emission efficiency by functionalizing GaN NWs with solution-processed p-MnO quantum dots (QDs) characterized by much wider bandgap energy than that of GaN. The energy transfer mechanism from QDs to NWs is also discussed using different structural and optical characterizations. This novel strategy is based on drop-casting QDs on NWs, which is simple, cost-effective, and applicable for large-scale applications.

Philosophiae Doctor - PhD / Sexually transmitted infections (STIs) are a problem for both developed and developing countries. Sub-Saharan Africa has the highest rates in the 15-49 years old group. The discovery that these infections playa vital role in the transmission of HIV raised their profile and made their control one of the central strategies of stopping the HIV/AIDS epidemic. In response to the challenge of improving the quality of care for people infected with STIs in the public health sector, the South African Ministry of Health adopted the syndromic management approach, recommended by the World Health Organisation as suitable for resource-poor settings, for use in primary health care clinics. In addition to providing guidelines on clinical management of STIs, the syndromic approach requires health providers to counsel and educate patients about STIs, encourage patients to complete treatment even if symptoms abate, promote condom use and the treatment of all sexual partners. While the management guidelines are clear and detailed around the diagnostic and medication issues, the processes of education and counseling are not as clearly outlined. Furthermore, although the syndromic approach is a viable way of providing good quality care to larger sections of the population than could be serviced through dedicated STI clinics, it requires health providers working in primary health care clinics, most of whom are professional nurses, to perform some tasks for which they may not be adequately trained. This study evaluated the quality of care for persons infected with ST!s by examining the extent to which the syndromic approach was being implemented in primary health care clinics. Interviews, using semi-structured interview schedules, were conducted with ST! patients and health providers in twenty-four clinics located in four provinces. In depth qualitative interviews were also conducted with a sub-sample of the patients. For further triangulation the methods of participant observation, through the use of simulated patients, and focus group discussions with various community groups were used. The findings of the study indicate that although primary health care clinics in South Africa are well-resourced, the management of patients with ST!s is inadequate. Adherence to the various aspects of syndromic management was poor. Similar to other studies in South Africa, the attitudes of health providers towards patients with ST!s were found to be problematic, a finding that has implications for health-seeking behaviours. The thesis argues that a large part of the problem is related to the multiple roles that nurses have to play in primary health care settings, as well as the content and methodology of the training of nurses who manage ST! patients. It further argues for the constitution of the basic health team at primary health clinics to be multi-disciplinary, and for a multi-disciplinary input in the training of health providers.

The present work covers investigation of the growth mechanism and growth kinetics of the ZnO nanowires and nanoneedles fabricated by using high-pressure pulsed laser deposition. The growth model based on the combination of four different flows of the interfacial particles is introduced. A variation of the free energy is given as a major reason of the change of the growth mechanism which appears by using different doped seed layers, growth temperature and the doping of the deposited material. A fabrication of the ultrathin nanowires with a diameter of d < 10 nm at CMOS compatible growth temperature of T = 400°C is demonstrated. The diameter of these nanowires is comparable with the Bohr radius. The growth of the Al and Ga doped and undoped ZnO nanoneedles with a sharp tip was shown. The doping of the nanowires and nanoneedles can be promising for their applications. By using a patterned sapphire substrate, an unidirectional growth of the nanowires and nanoneedles was achieved. These nanostructures are tilted by 58°ZnO with respect to the surface normal.:Bibliographic Record Contents 1 Introduction I Basics and Methods 2 Basic properties and growth concept 2.1 ZnO nanowires and nanoneedles 2.1.1 Applications 2.2 Nanowire and nanoneedle fabrication 2.2.1 Growth mechanisms which require a catalyst 2.2.2 Catalyst-free epitaxial growth mechanism 2.3 Free energy and the growth mechanism 2.4 NW growth techniques 2.5 Aligned tilted growth 3 Growth and characterization 3.1 Preparation of the seed layers by CVD 3.2 Preparation of the seed layers by low pressure PLD 3.3 HP PLD for the NW and NN growth 3.4 Characterization techniques 3.4.1 X-ray Diffraction 3.4.2 Atomic Force Microscopy 3.4.3 Scanning electron microscopy 3.4.4 Energy Dispersive X-ray Spectroscopy 3.4.5 Spectroscopic Ellipsometry 3.4.6 Cathodoluminescence 3.4.7 Angle-varied X-ray photoelectron spectroscopy 3.4.8 Etching of the seed layers 4 Seed layer characterization 4.1 Doping concentration 4.2 Surface morphology 4.3 Crystalline quality 4.4 Surface polarity 4.5 Summary of the Chapter II NW growth: results 5 NW growth characteristics 5.1 Material free energy and the deposited material parameters 5.2 Growth kinetics 5.3 Summary of the Chapter 6 NW growth on doped seed layers 6.1 Al doped seed layers 6.2 NW growth on Ga doped seed layers 6.3 Optical characteristics of the ZnO NWs 6.4 Summary of the Chapter 7 Growth of ZnO(Al) and ZnO(Ga) NWs 7.1 Al-doped ZnO NWs grown on ZnO(Al) seed layers 7.2 Ga-doped ZnO NWs grown on ZnO(Ga) seed layers 7.3 Summary of the Chapter 8 Growth of tilted ZnO NWs and NNs 8.1 Patterning of the substrates . 8.2 Growth of tilted NNs 8.3 Growth of tilted NWs 8.4 Optical properties of the tilted nanostructures 8.5 Summary of the Chapter 9 Summary and outloock 9.1 Summary 9.2 Outlook Acknowledgements Curriculum Vitae List of own Articles List of own Conference Talks and Posters References

Endocannabinoids (eCBs) are lipophilic signals that are produced by postsynaptic neurons in an activity-dependent manner, and signal in a retrograde fashion to modulate neurotransmitter release. As such, eCBs are highly involved in synaptic plasticity, a process that strengthens or weakens synapses. eCB-mediated synaptic plasticity is involved in many brain processes including learning, short-term memory, and adaptive reward, which are processed in the hippocampus and ventral tegmental area (VTA), respectively. However, the expression of eCB biosynthetic enzyme mRNA within hippocampal and VTA neurons, as well as the relationship between these mRNA species and the occurrence of synaptic plasticity, remains unclear. The goal of these studies was to demonstrate the expression pattern of eCB biosynthetic enzyme mRNA within hippocampal and VTA neurons, and to describe the relationship between synaptic plasticity and mRNA expression. Using whole-cell electrophysiology and real-time quantitative PCR, I tested hippocampal and VTA neurons for the presence of eCB biosynthetic enzyme mRNA and described the relationship between these enzymes and synaptic plasticity. The data presented herein demonstrate the importance of eCB signaling within the hippocampus and VTA and the expression patterns of eCB biosynthetic machinery within several neuron types. These data provide evidence that eCB signaling plays a critical role in learning, short-term memory, and adaptive reward.

Iron-based superconductors might be promising for high field applications due to their decent superconducting transition temperature Tc, high upper critical field and low anisotropy. However, similar to cuprates the materials suffer from the detrimental effect of large angle grain boundaries reducing significantly the critical current density J c. Therefore, a coated conductor technology must be applied to solve this issue using highly textured templates based either on the ion beam assisted deposition (IBAD) or the rolling assisted biaxial textured substrates (RABiTS) approach. The main aim of this thesis was to apply such templates and to study the correlation between the microstructure and the current transport on a local scale in epitaxial Fe(Se,Te) layers deposited on such tapes as well as on single crystals. Therefore, thin films were grown by pulsed laser deposition and studied in detail afterwards including a local texture analysis with high-resolution electron back scattering diffraction (EBSD) as well as transmission electron microscopy (TEM) to identify the local defect structure. Simultaneously, the current transport was investigated globally by magnetization measurements and on a local scale by scanning Hall probe microscopy (SHPM). X-ray diffraction studies showed a clear epitaxial relationship and a high texture quality for thin films on all templates. However, misoriented grains were observed for higher deposition rates and film thicknesses. The Tc reached values of up to 21 K on CaF2 single crystals and 18 K on metal templates, respectively. The J c determined from magnetization loops showed values above 2 MA cm−2 and 1 MA cm−2 at 2 K in self-field on single crystals and IBAD based templates, respectively, whereas the global J c for films on RABiTS templates was one magnitude lower. Detailed TEM studies revealed smooth layers on all templates with minor defects for films on single crystals, but pronounced grain boundaries for layers on metallic templates. Unfortunately, EBSD measurements on the grown films showed a low indexing rate prohibiting the analysis of the grain boundary network. In contrast, SHPM proved a homogeneous magnetization profile for Fe(Se,Te) films on singe crystals and IBAD templates, whereas a distinct magnetic granularity was observe on RABiTS tapes. Detailed TEM studies in combination with transmission Kikuchi diffraction pattern revealed a strong dependence of the film growth on the out-of-plane orientation of the Ni-W grains. In general, the local SHPM studies revealed a similar dependence of superconductivity on granularity for Fe(Se,Te) as previously observed for YBCO.