A Surface Science and Thin Film Approach to the Development of Functional Materials

Abstract

Nanoscale properties are becoming increasingly important for the successful utilisation of modern materials and devices, where surfaces or interfaces often largely define functionality. It is critical to understand surface behaviour and its impact on properties for the development of new and existing materials. Current surface science and thin-film techniques have been utilised and developed to investigate promising functional materials. The surface chemistry of Au/Pd surface alloys was examined for the selective oxidation (selox) of crotyl alcohol to crotonaldehyde. X-ray Photoelectron Spectroscopy (XPS) and Thermal Desorption Spectroscopy (TDS) have been used to elucidate the reaction pathway for the alcohol and the main products. Au moderates the surface reaction by ‘turning off’ the main decomposition pathway of the aldehyde. The amount of surface Au has a critical role in determining the selectivity. To mimic ‘true’ selox, the influence of co-adsorbed O over the Au/Pd alloys was also investigated. O plays an important role in aiding desorption of the aldehyde. The exact nature and role of Au and O in moderating the reaction over Pd(111) requires further investigation. A key area of technological interest is field of spintronics, whereby the spin and charge of electrons are exploited for electronics. Thin-films of Fe3O4, a promising spin injector, were grown on a variety of substrates to characterise the magnetic/magnetoresistive (MR) properties. The Magnetorefractive Effect (MRE), an optical technique, was used for non-contact measurements of the MR. Despite no difference in the MR, the MRE shows a thickness dependence, which is partly due to the large skin-depth associated with Fe3O4. Modelling the complex dielectric function for Fe3O4/MgO allowed simulations to be carried out of the IR and MRE spectra. With further work, the model may be used to determine film thickness, examine the conductivity mechanisms and their influence on the MR/MRE.