This thesis presents work to develop methods for a novel magneto-optical tweezing microscope used to interrogate DNA, as well as complementary multiscale molecular dynamics simulations.

Optical diagnostics on fusion devices are important for both research and real time control. All of these diagnostics depend on reflective optics in the form of metallic mirrors. Etching and re-deposition during fusion operation from the beryllium inner wall onto the mirrors can cause severe degradation in the reflectivity. Using the mirror as the powered electrode to form a capacitively coupled plasma above the surface is seen as the most favourable method for recovery of the mirror reflectivity. The ions created within the plasma can bombard the surface and remove the deposit. This method has been tested experimentally in various ways and in various geometries and has been proven to work in these cases. However, in order to optimise the system modelling efforts are carried out within this thesis. The Hybrid Plasma Equipment Model (HPEM) is configured to simulate the etching plasma and is benchmarked against experimental results. After successful benchmarking parameters are varied in an attempt to find optimum settings for the successful implementation of this method on ITER. Results concluding that individual mirrors require individual modelling efforts as trends cannot necessarily be applied to each mirror geometry. A beryllium/argon/oxygen gas chemistry set is created to more accurately model the ITER environment which is compared with a published aluminium/argon/oxygen set. Aluminium is currently used as a proxy for beryllium in the majority of experimental work. They are shown to be dissimilar in their behaviour within a bulk Ar plasma which will have knock on effects for the etching process. The bulk plasma properties remain identical at low fractions of Be or Al. Also presented is work involving understanding the mechanism behind modification of polypropylene using an atmospheric-pressure plasma jet. A two stage process is identified involving atomic oxygen from the jet and nitrogen from the surrounding atmosphere.

Highly spin-polarised materials show great promise in applied spintronics as spin-filters and spin transfer torque magnetic random-access memory devices for data storage. However, controllable magnetisation switching requires materials with a low Gilbert damping parameter and stable magnetic properties at room temperature. Two highly spin-polarised magnetic materials with critical temperatures well above room temperature are characterised using a series of structural and magnetic analysis techniques. Correlation between the magnetic damping and microstructure is observed in both Fe3O4 and Co2FeAl0.5Si0.5 samples and both are seen to improve structurally and show more favourable damping parameters with annealing. Annealing Fe3O4 in CO/CO2 is shown to reduce the antiphase boundary density and decrease the two-magnon scattering-like extrinsic damping effects. The quality of the sample structure and the stoichiometry is also seen to improve considerably after the annealing although the defects are not completely eliminated. An anomalous peak in the damping of the annealed film is observed at 10GHz Co2FeAl0.5Si0.5 grown on germanium and silicon substrates is seen to also improve with thermal annealing. The Gilbert damping is seen to be lower in the as-grown scheme using the silicon substrate but greater reduction of damping post-annealing is seen on germanium. In both cases the B2 order is observed in the Co2FeAl0.5Si0.5 thin films, and intermixing between the sample and substrate observed above 500oC is sufficient to disrupt the crystal structure and introduce significant extrinsic damping effects which increase the total damping. This prevents the Co2FeAl0.5Si0.5 from reaching the more desirable L21 structure.

The study of shell middens and archaeological marine shells is important to investigate palaeoenvironments and human development. Analytical methods, such as isotope analyses, used for these reconstructions can only be trustworthy if the shells have not been drastically changed by the effect of diagenesis or by human intervention, eg., heating of the shells. These changes are difficult to quantify by the current methods, which are either limited or destructive. In this thesis, a quantitative method for the assessment of diagenesis and the evidence of heating in sea shells has been proposed with Raman spectroscopy (RS), which is based on the inelastic scattering of light, whereby a small difference in the incoming and outgoing light energy provides highly sensitive spectroscopic information. The quantitative analysis of the Raman spectrum involved peak fitting procedures to obtain the peak position, amplitude and full width half maximum (FWHM) parameters, which were then compared between modern and ancient Conomurex fasciatus and Nucella sp. shells to obtain markers of diagenesis. Modern Conomurex fasciatus shells were heated at different temperatures and time conditions with the quantitative Raman parameters compared across different heat-treatments that were later compared to burnt archaeological Conomurex fasciatus fragments obtained from the same shell midden. The results have proven that quantitative RS is responsive to diagenetic alterations and heating of sea shells indicating an increase in the calcium carbonate crystallinity caused by the degradation of the organic macromolecules that supported the strained mineral lattice, demonstrating that RS is sensitive to indicate diagenesis in sea shells.

Magnetic nano-systems have a wide scope of applications ranging from data storage technologies to biomedicine. In data storage devices the information is encoded in the grain magnetisation corresponding to bit "0" and "1". The recording media industry is driven by increasing the areal density of stored data and decreasing cost, while in the same time maintaining the thermal stability and signal-to-noise ratio. For this, close-packed 2-dimensional granular systems are used, with nanometre grain size. The quality of such magnetic recording media depends on the intrinsic material properties and on the inter-granular coupling via exchange and magnetostatic interaction. The work presented here studies the effects of inter-granular coupling and investigates different approaches to extract intrinsic properties from the bulk measurements. Due to the irregular shape of the grains, the dipole approximation for magnetostatic interaction is inaccurate. For higher accuracy, a 5-fold numerical integral is required for each pair of grains. Analytical integration over the grains height is possible reducing the numerical calculation to a 3-fold integral. The competition between the exchange and magnetostatic interactions leads to complex magnetic structures and correlated behaviour, where groups of grains behave collectively. The effects are observed and studied here based on the magnetic radial correlation function which shows a damped oscillatory form as a function of grain separation. The correlation length increases with increasing exchange interaction. An important consequence of correlated behaviour is that it alters the intrinsic switching field distribution (SFD), leading to an effective SFD. The intrinsic SFD is a fundamental characteristic of granular magnetic materials, defined as the distribution of irreversible switching events of magnetic grains in the absence of inter-granular interactions. Separating the intrinsic SFD from the effective SFD remains a challenge. Two methods that have been widely used to extract the intrinsic SFDs from hysteresis based measurements, the so-called FORC method and the Delta H(M, Delta M)-method are compared. It is shown here that the FORC diagrams contain useful information about the interactions in the system, but the ability to extract the intrinsic SFD is limited to the system in which the magnetic correlations can be neglected. Identifying the SFD from hysteresis loop measurements in the parameter range relevant for applications, requires applying the inverse problem solving techniques such as the Delta H(M, Delta M)-method.

Monolayers of molybdenum disulphide MoS2, a two dimensional (2D) semiconductor with a direct band gap of 1.9 eV, have been proposed as a candidate for next generation nanoscale electronic and opto-electronic devices. Controlled synthesis of MoS2 monolayers is critically important since the thickness uniformity and grain size are major concerns for the fabrication of opto-electronic devices. In this study, we demonstrated the growth of wafer scale uniform MoS2 monolayers on SiO2 covered silicon wafers, at a range of growth temperatures (650 oC-850 oC) with optimum grain sizes as large as 400 μm, using low pressure chemical vapor deposition (LPCVD). By controlling the partial pressure of the reactant species at the growth surface and the limiting time, we can achieve prefered monolayer growth over multilayer growth. The MoS2 monolayer crystals follow a lognormal size distribution, consistent with random crystal nucleation, with single crystal domains as large as 400 μm. We estimated the thermal expansion coefficient to be (2.5±1.2) ×10-6 /oC, which is at least double that of the bulk. We have found film growth can be clearly classified into the reaction limited, feed limited and desorption limited regimes. With the help of COMSOL simulations, we have related the local growth environment such as growth temperature, MoO2 concentration, sulphur chemical potential and growth time with the macroscopic growth parameters such as Ar flux. In the feed limited regions, it is the supply of Mo that is the rate limiting factor. In the desorption regions, the growth is controlled by thermal stability of MoS2 monolayers. The growth modes also can be used to tune the grain morphology from perfect triangles to hexagons. Finally, we have also compared our approach with an LPCVD approach based on MoO3 as the Mo source. MoO3 has a higher vapor pressure than MoO2 which was used in the previous approach. By tuning the the S:MoO3 ratio, we could grow controllably planar MoS2 monolayers, vertically aligned MoS2/MoO2 and planar MoO2 crystals.

This thesis presents the photophysical characterization and device performance of a series of small molecules and copolymers showing thermally activated delayed fluorescence (TADF). This triplet harvesting mechanism allows triplet states to contribute to the light generation process, thus increasing the efficiency of organic light emitting diodes (OLEDs). TADF based OLEDs with internal quantum efficiency (IQE) close to 100% have already been demonstrated. However, many aspects of the mechanism still remain unclear and need to be tackled in order to design novel and more efficient TADF molecules, with emission in different regions of the spectrum. In order to maximize the TADF mechanism in different organic systems, the interplay between the charge transfer state and local triplet excited states are studied in detail and it was found that the mixing of CT and local triplet states is essential to achieve efficient reverse intersystem crossing (RISC). The consequence of introducing bulky side groups on the D unit was also studied and the luminescence from these molecules varies from efficient TADF to strong phosphorescence at room temperature. Remarkably, in clear contrast with the donor substituted molecules, their acceptor substituted analogues are strong TADF emitters. Furthermore, the fine-tuning of TADF efficiency in copolymers was explored by using spacer groups in a range of polymeric structures, overcoming the theoretical IQE limit for pure fluorescent compounds in solution-processed OLEDs. Moreover, the contribution of TADF emission in Cu-complexes showing aggregated induced emission was studied to probe the effects of vibrations on the luminescence quenching in these complexes.

In this thesis two different types of effective field theories (EFTs) have been considered to give an interpretation to effects of physics beyond the Standard Model. The first type of EFT is a so-called Simplified Models, in which the Standard Model is extended by new scalar degrees of freedom $A$ (CP-odd) and $S$ (CP-eve), which give rise to interactions of the type $t\bar{t}S$ and $t\bar{t}A$ with subsequent decay of $S/A \to b\bar{b}$. We study the phenomenology of these processes at the LHC and find that the production of $t\bar{t}A$ is suppressed compared to that of $t\bar{t}S$. Using the Weyl-van-der-Waerden spinor formalism we analyse the helicity amplitudes in order to explain this phenomenon.\newline \noindent In the second part of this thesis, we focus on the dimension-six Standard Model Effective Field Theory (SMEFT) to calculate the next-to-leading order (NLO) electroweak corrections to the forward-backward asymmetry in the process $e^+ e^- \to b\bar{b}$. We find that the NLO EFT corrections can not be neglected compared to the LO EFT contributions. We show that relevant numerical results have been obtained, which can be used to constrain the Wilson Coefficients involved in this process. We calculate the amplitude of the $Z \to b\bar{b}$ process and renormalise it together with the $e^+ e^- \to b\bar{b}$ process. We have also analysed the NLO EFT corrections to the cross-section of the $e^+ e^- \to b\bar{b}$ process, which can be used to set limits on the Wilson coefficients with future collider experiments.

Rhenium diselenide and rhenium disulphide are layered semiconductors that belong to the transition metal dichalcogenide (TMD) family. Like graphene and other TMDs, these materials can be exfoliated down to a few atomic layers. However, unlike other TMDs, the rhenium dichalcogenides are only stable in a triclinic structure that exhibits in-plane anisotropy. This anisotropy manifests itself in the vibrational, optical and electronic transport properties ofthese crystals. Ab initio calculations and experimental results are presented to describe the Raman spectra of the rhenium dichalcogenides. From Raman spectroscopy the anisotropy of these crystals can be observed. Flipping a flake (a C2 rotation about an axis in the layer plane) is not a symmetry of the system. Therefore, there are two non-equivalent vertical orientations. Raman spectroscopy can be used to identify whether a flake is facing "up" or "down". The latticedynamics of these crystals are described using a simple ball and spring model. It is shown that low mass impurities, such as sulphur, in ReSe2 can occupy four non-equivalent positions of the unit cell; there are four local vibrational modes corresponding to these four positions and Raman spectroscopy can be used to find them. An unusual experimental geometry (edge-on excitation) helps enhance these signals. The electronic band structures of bulk ReSe2 and ReS2 are explored using angle-resolved photoemission spectroscopy (ARPES). From the measurements and complementary DFT calculations it is shown that: (i) there is anisotropy in the electronic dispersions; (ii) the valence band maxima are not located along any of the high symmetry directions; and (iii) both of these crystals have indirect band gaps. The rhenium dichalcogenides were thought to act as electronically decoupled monolayers; it is demonstrated that this is not the case and that thereis signicant electronic coupling between the layers. Finally, ARPES results of a monolayer of ReSe2 are presented; again, anisotropy in the electronic band structure is observed.

This thesis details the development of the pre-requisite experimental tools to create a proof-of-principle spin-squeezed atomic clock based upon an array of individual strontium atoms using Rydberg-dressed interactions. We experimentally and theoretically study Rydberg-dressing in a strontium narrow-line MOT, demonstrating that it is possible to coherently admix a Rydberg state into the narrow intercombination transitions of strontium. This work is based upon a quantitative semi-classical Monte-Carlo model of a strontium narrow-line MOT, where the combination of a quantum treatment of the light scattering process with a Monte-Carlo simulation of the atomic motion leads to a quantitative description of the spatial, thermal and temporal dynamics of the narrow-line MOT. By performing calculations of the dynamic polarisability of all the states relevant to laser cooling strontium, we have designed and constructed a new experimental apparatus to facilitate the creation of a microtrap of strontium. We observe and characterise the frst known microtrap of strontium and outline the next steps towards the creation of an array of single atoms. Due to the creation of Rydberg atoms in the strontium microtrap, understanding ionisation and interaction mechanisms may be of signifcant importance. We therefore study Rydberg ionisation mechanisms in a thermal beam of strontium atoms using simultaneous measurements of Rydberg EIT and spontaneously created ions or electrons. By connecting the optical and electrical signals using the optical Bloch equations, we are able to determine the dominant ionisation mechanisms of Rydberg atoms in the thermal beam. We also report the frst observations of optical and electrical bistability, which may shed further light onto the origin of bistability in atom vapours.