This thesis focusses on the phenomena of charge ordering and orbital ordering in transition metal oxides, using the technique of resonant x-ray diffraction (RXD). The technique is suited to such studies, as it provides an elemental and band specific probe of long range electronic correlations. Here, we present hard and soft x-ray diffraction results on iron and manganese compounds, and demonstrate the utility of resonant x-ray diffraction in revealing their electronic properties. By performing comprehensive hard x-ray RXD studies on the complex charge ordered structures of magnetite and iron oxyborate, we demonstrate that both systems possess non-integer charge order by using the FDMNES simulation code. We find certain reflections have anisotropic polarisation dependencies, due entirely to the crystal structure, with no need to invoke orbital order to explain the observations. In both materials we demonstrate that the anomalous scattering components can result in a surprising conversion from linearly to non-linearly polarised light, through two subtly different interference processes. This is the first report of such mechanisms. By performing soft x-ray scattering on Pr(Sr$_{0.1}$Ca$_{0.9}$)$_2$Mn$_2$O$_7$, we have provided the first direct observation of the orbital rotation within this compound. We have found that there is no apparent change in the orbital occupation during the stripe rotation, but an increase in the charge disproportionation upon cooling. We have used soft x-ray RXD on lutetium ferrate to discover an anisotropic contribution to the scattering at the charge order wavevector. This is not apparent when probing the crystal structure directly using hard x-rays. We attribute such a signal to charge-orbital order within the system, in contrast to previous claims that the system is an orbital glass.

Measurement of sound wave velocity and attenuation by the ultrasonic pulse-echo technique are used to obtain insight into the nature of weak interatomic binding forces which are present or develop in certain materials. In particular, anomalies are found in both the elastic and anelastic properties in the vicinity of the martensitic phase transformations which occur in TiNi andIndium-thallium alloys. Considerable differences found between the elastic moduli of the two phases of TiNi are shown to arise Mainly from a variation in the free carrier density. Previously reported elastic constant data of some fcc indium-thallium alloysAre complemented by the present results and an overall picture of the compositional dependence of the elastic properties of theseAlloys in both the tetragonal and cubic phases are provided. Zirconia can be forced into a cubic structure by the addition of more than 7 mole % yttria: elastic constant data of two zirconia-yttria solid solutions, technologically important materials, provides a basis for the discussion of the stability of the cubic phase. Finally, on the basis of an evaluation of the elastic moduliof arsenic, a pronounced layer-type crystal, the ultrasonic wave propagation characteristics in this material are extensively compared and contrasted with those of the other two rhombohedral elemental semimetals antimony and bismuth, neither of which are themselves layer-like. The elastic wave propagation in antimony and bismuth is shown to differ not only in degree but also in kind from that in arsenic which exhibits the characteristics expected for a layer-like crystal. The weak binding forces in each of the materials studied are shown to play a dominant role in their elastic behaviour.

The structure and growth of self-assembled nanoparticle networks and epitaxial rare-earth thin-films have been studied using X-ray scattering.;A diffusive growth model was developed to model the specular reflected X-ray signal monitored at the anti-phase position, during the growth of two rare-earth (RE) metals, gadolinium and samarium onto molybdenum(110) single crystals. The model identifies atomic layer spacings and the degree of interlayer mass transport. Both RE elements are shown to grow in a layerwise manner but with significant roughness after the initial layer is occupied. The RE growth mode was modified by raised substrate temperatures. The presence of pre-deposition oxygen at the surface was found to encourage layer-by-layer growth for both Gd and Sm.;The structure of noble-metal nanoparticles passivated with thiolate organic ligands was studied using small and wide angle X-ray scattering (SAXS/WAXS). Ag nanoparticles were found to consist of a spherical metal core with fcc atomic packing. The passivating shell was modified to induce direct cross-linking between nanoparticles. The structure and development of the nanoparticle aggregates formed due to the interactions between functionalised thiol derivatives of porphyrin, benzene, C5 dithiol and MUA was monitored with SAXS. In all cases the structures were found to be open and fractal, with the size of the cross-link determined by the size of the functionalised ligand.;The structural quality of self-assembled noble-metal nanoparticle superlattices was investigated using GISAXS. Au nanoparticle networks were formed at the air/water interface. Fits to the GISAXS data, revealed that strain build-up in the layer can directly control the interparticle spacing. Larger Au nanoparticles were allowed to self-assembly onto a Si(111) substrate. The influence of the substrate temperature prior to assembly was investigated and revealed a striking phase transition below 16.7°C from disordered nanoparticle networks to highly ordered layered nanoparticle structures. It is thought that solvent volatility plays a crucial role in the ordering process.

This thesis reports on the application of the Kelvin probe in materials science and in particular on the study of metal and semiconductor surfaces in both ambient and UHV environments. The concept of the work function φ and its importance as a parameter in materials science is discussed in the context of novel technological applications. The various methods to determine the work function are reviewed. The main measurement technique used here – the Kelvin probe - is described in detail. The Kelvin probe measures local work function differences between a conducting sample and a reference tip in a non-contact, truly non-invasive way over a wide temperature range. However, it is an inherently relative technique and does not provide an absolute work function if the work function of the tip (φtip) is not known. Therefore, a novel technique has been developed to measure φtip with the Kelvin probe via the photoelectric effect, thus combining the advantages of both methods to provide the absolute work function of the sample surface. High and low work function surfaces were generated as target materials for a novel ion source based on hyperthermal surface ionisation: oxidised rhenium exhibits the highest work function of 7.15eV at a temperature of ~900K whereas the lowest work function of ~2.54eV was measured on lanthanum hexaboride, LaB6. The process of thermal and hyperthermal surface ionisation (SI, HSI) as well as the generation of hyperthermal molecular beams is discussed and a model of the surface ionisation process is developed to estimate its efficiency. Experimental data of SI and HSI are presented. The application of the Kelvin probe for the detection of defects and impurities in semiconductors, namely iron contamination, is demonstrated via two methods based on the measurement of the surface photovoltage. We find that both methods yield a lower surface potential and surface charge for iron contaminated wafers compared to a clean sample and therefore can be used as an indicator for chemical contamination on semiconductor surfaces.

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