Carbon possesses a number of properties that make it ideal for use in sensor and electrical applications. Using radio frequency plasma with various precursor gases it is possible to prepare carbon surfaces for further molecular attachment or functionalisation. Research in our laboratory has involved studies of plasma fluorination, hydrogenation and methanation of highly ordered pyrolytic graphite (HOPG) (as it serves as a highly ordered, single crystal, model substrate for other more complex forms of carbon), glassy carbon in the form of pyrolysed photoresist films (PPF) and single-walled carbon nanotubes (SWCNTs). Treated surfaces have been characterised using a variety of investigatory surface techniques. In this article we report on results obtained using X-ray Photoelectron Spectroscopy (XPS) for probing the chemical nature of the surface and hence the extent of treatment; Time of Flight Secondary-Ion Mass Spectrometry (ToFSIMS) has been utilised to examine the molecular surface structure and in particular, determine the extent of surface hydrogenation; Scanning Tunnelling Microscopy (STM) measurements provide information on the morphology of treated surfaces, in particular the damage and change in surface structures caused by various plasma treatments. We show in this work that the morphology, mechanisms and extent of modification of the plasma-modified surface obtained is strongly influenced by various experimental conditions. For instance, etching and/or nucleation and growth features are observed, with the type of features and their distribution strongly dependent on the precursor gas that is used to support the plasma. Other important parameters are operating pressure, RF power and exposure time.
In this paper a new approach for directly organizing single-walled carbon nanotubes (SWCNTs) onto a silicon (100) surface by the surface condensation reaction with hydroxyl terminated silicon is presented. X-ray photoelectron spectra, Raman spectroscopy and atomic force microscopy show that the shortened SWCNTs have been organized successfully on silicon. The optical properties of SWCNT array exhibit strong fluorescence in the visible wavelength range from 650-800 nm. The fluorescence can be attributed to the coupling effects between attached SWCNTs and silicon substrate.
Nanosphere lithography, which allows for the fabrication of patterned metal surfaces, is a simple, effective and unconventional technique that exploits a self-assembly process. Using this technique, polystyrene nanospheres with diameters of 500nm, and 100nm were assembled onto a 'muscovite' mica substrate in a hexagonally close packed monolayer array, to provide a physical mask for material deposition. Thermal evaporation was subsequently used to deposit gold through the nanosphere mask layer, to generate a periodic array of gold nanostructures. Upon changing the mask to a multi-layered array of nanospheres, slightly more complex nanostructures were achieved. However due to thermal evaporation being a high temperature process the nanostructures obtained deviated from their predicted quasi triangular shape due to a slight annealing of the polystyrene mask.
Lumogen Yellow S0790 is a commercial azomethine based pigment and is used for enhancing CCD devices for detecting ultraviolet radiation. In this work we report on the crystal structure and morphology of the raw material, as-deposited and post-annealed films, as well as the influence these have on the subsequent optical properties. Our measurements of physical vapour deposited (PVD) Lumogen films indicate that commercial Lumogen powder is crystalline in its as-received state, with a melting point of 273.3°C and boiling point of 328.6°C. Furthermore, we have found that as-deposited films on room temperature substrates possess an inherent crystalline structure, which has not been reported previously, but also that the material’s structure changes into a completely different crystalline form upon annealing for 90 hours at 80°C.