High-resolution x-ray scattering has attracted intensive attention for both fundamental research and industrial applications. Recently, the advance of synchrotron radiation sources has dramatically improved x-ray intensities, brightness and resolution, which has enhanced the ability of x-ray scattering studies. In spite of weak scattering cross-sections, high-brilliance x-ray sources have made the studies of surfaces and interfaces possible. In the last decade, many new x-ray techniques such as glancing-incidence-x-ray-reflectometry, crystal-truncation-rod analysis and reciprocal-space-mapping have been established and had great success in exploring the structure of various materials. This thesis starts with a review of high-resolution x-ray scattering which covers both the theoretical and the experimental backgrounds. Near perfect semiconducting thin films are examined to demonstrate the abilities of high-resolution x-ray scattering. Glancing incidence x-ray reflectometry was used to explore the interface morphology of a Si<SUB>0.1</SUB>Ge<SUB>0.9</SUB> heterostructure grown with and without antimony acting as a surfactant. The results demonstrate that the film is smoother when grown with a sub-monolayer of the surfactant. Furthermore, due to the existence of the surfactant during growth, abnormal strong scattering was found from the long-range coherent conformal roughness. YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>x</SUB> thin film superconductors grown on various substrates from different growers were studied. Using high-resolution x-ray scattering techniques, the sample quality was measured using the position and the width of the Bragg reflections. By analysing the reciprocal space maps, the surface parallel lattice parameters were also determined. One of the best samples, the YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>x</SUB> grown on SrTiO<SUB>3</SUB> by pulsed laser deposition was further studied. The results suggest that an ultra-high-quality crystal with thousands Ångstrom vertical and microns horizontal correlation is occupied nearly 95% of volume. However, due to the interface roughness, the scattering from this crystal can only be observed at low angle Bragg reflections and, therefore, is often ignored. Because this type of film is the best single crystal high-T<SUB>c</SUB> superconductor, it will be the doorway to understanding high-T<SUB>c</SUB> superconductivity.

No description available.

The work described in this thesis is concerned with the synthesis, stability and dye incorporation into large pore molecular sieves, in particular looking at the ultra-large pore aluminophosphate molecular sieve VPI-5. The synthesis of VPI-5 was carried out with two types of system: i) Gels templated with the amine di-n-propylamine; ii) A clear solution "organic-free" system using a water soluble aluminium phosphate hydrochloride ethanolate (APHE) precursor. High purity yields of VPI-5 were obtained by optimisation of both systems. Analysis of the products produced by the different synthesis routes gave evidence that the aluminophosphate H1 and VPI-5 are very closely related. By the addition of polyethylene glycol to APHE systems large single crystals (10-20 μm wide by 250-1000 μm long) of VIP-5 synthesised for single crystal X-ray diffraction studies. The thermal stability of VPI-5 was thoroughly investigated and the apparent activation energy for the conversion of VPI-5 (synthesised with d-n-propylamine) to A1PO<SUB>4</SUB>-8. Encapsulation of dye within VPI-5 was shown to be capable of increasing the photostability of the dye. Dye sorption into faujasite materials with differing Si/Al ratios was investigated. It was found that a water sensitive solvatochromic complex was formed when the dye waxoline yellow RPFW was sorbed into the hydrogen form of dealuminated zeolite Y.

The hydrophilic and hydrophobic properties of surfactant molecules enable them to organise in large structures when dissolved in water. Under certain conditions they can organise in bilayers forming the lamellar phase. The equilibrium properties of this phase have been well studied. In this study we observe the dynamic and kinetic behaviour during the swelling and dissolution of the lamellar phase. We have performed penetration scan experiments under different thermodynamic conditions using video microscopy. When the lamellar phase is insoluble in water classic myelin instabilities are observed. These instabilities have been studied with microscopy and in some cases we use tracer particles to follow fluid flow in between the myelins. We report qualitative features of the myelin growth as well as provide some quantification of the swelling process. Specifically, we determine an effective diffusion coefficient for the swelling lamellar phase. In the case of a soluble lamellar phase myelin instabilities are not observed. Also, we report instabilities observed at the liquid surfactant/lamellar interface. These instabilities appear to create multilayer vesicles which move into the liquid surfactant. We have found these to be attached to the surface of a wedge of lamellar phase that moves along the surface of the cell into the liquid surfactant phase. Also, we have conducted contact experiments using a presheared lamellar phase the so called “onion” texture. The onion phase does not form myelins as in the normal case. Instead the onions dissolve into an isotropic (“sponge”) phase. During the onion dissolution a small stable core remains. If the sample is observed over a more extended period the onions are observed to coalesce. These features were investigated at different temperatures.

No description available.

No description available.

The work has dealt with the study of sulphide and oxide overlayers on a Ni(111) single crystal sample, applying the surface science techniques of Auger Electron Spectroscopy, Low Energy Electron Diffraction and Reflection Absorption Infra-Red Spectroscopy. The later technique has been used to probe these layers at pressures up to 100's of Torr revealing novel features for the absorption of carbon monoxide and hydrogen not previously observed on this crystal face. The absorption of CO under UHV conditions was also studied using Reflection Absorption Infra-Red Spectroscopy on the sulphide and oxide overlayers prepared. The data obtained from the experiments yielded information on coverage, thermodynamic, isobaric and isothermal parameters. The sulphide layers investigated were the (39x39)-S, (53x2)-S, (83x2)-S and a layer designated S1 in this work which had no literature equivalent. Two oxide layers were studied, a well characterised p(2x2)-O overlayer prepared by classical methods and a more heavily oxidised NiO/p(2x2)-O surface prepared by continuous oxidation of the sample. AES and LEED were used as experimental probes to complement the infra-red data as well as during the initial surface preparation.

The potential exploitation of the metal-dissolution effect in chalcogenide glass for the fabrication of diffractive structures is investigated. Evaporated As-S films form the host chalcogenide glass for optical or thermally stimulated dissolution from a metal source, usually an evaporated Ag film. A potentially more flexible alternative fabrication method in which the source is a photolithographically generated metal grating is considered. Ag gratings with periods of 6-12<I>μ</I>m and thicknesses up to 0.4<I>μ</I>m are produced on fused silica substrates and coated with 1-2<I>μ</I>m thick As-S layers. The resultant metal-dissolved structures have diffraction efficiencies of 4-7% when replayed with a HeNe laser (λ = 633nm) and remain well defined in the lateral dimensions despite some sideways leakage of Ag evident for both the thermal and optical dissolution regimes. Higher efficiencies should be possible using this method with optimised structures. The gratings are stable for HeNe beam powers of ˜6mW once all the Ag source has dissolved. The thermal coefficients of the optical thickness (<I>nd</I>) of the metal-rich and metal-free glass phases were measured in the infrared to assess the potential of metal-dissolved gratings in the field of athermalised optical systems. The metal-rich glass phase was found to have a coefficient ˜2.5x that for the metal-free phase, the films being annealed in each case. Coupled-wave theory is used to predict the likely behaviour of metal-dissolved gratings for various profiles and modulations in refractive index. Low modulation bulk gratings can give high diffraction efficiencies (>90%, neglecting reflection losses) and it is shown that the square-wave structure has particular merit because of its reduced grating depth requirements. For a bulk square-wave grating with a larger modulation the diffraction efficiency is shown to be over 80% when the grating depth is twice the period (<I>d </I>= 2Λ).

No description available.

No description available.