Title:
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The fabrication of nanoporous template thin films for supercritical fluid electrodeposition
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This work investigates the fabrication of nanoporous templates as a part of the supercritical fluid electrodeposition (SCFED) project. The goals set for this investigation was to produce films with pore channels (diameter < 5 nm) orientated perpendicularly on top of an electrode. During the course of this work, two techniques were investigated, Stöber-derived method and electrochemical-assisted self-assembly (EASA). The Stöber films produced perpendicularly orientated pore structure through a hydrothermal process. EASA film were generated through electrodeposition, resulting in highly ordered vertically aligned pore channels. Both these techniques were transferred from indium-tin oxide (ITO) onto titanium nitride (TiN), which increased the potential window of the substrate. The pore diameters of the Stöber and EASA films were determined as 2.6 and 1.6 nm respectively. This could be increased with the addition of a swelling agent or decreased by using a surfactant with a shorter tail length. Helium-ion microscopy was shown to provide high-resolution images of silica films. It provided detailed images of the topography and pores structure at the surface of the films. Tin was deposited into the pores of an EASA film using SCFED method. The EASA films were also subjected to post-synthesis chemical modification based on grafting functionalised silane molecules. As a result, the pore size and chemical properties were altered using a range of functionalised silane based grafting agents. Trimethylchlorosilane was found to be most successful at coating the pore walls. Other larger grafting agents were shown only to partially coat the surface of the films. This was only possible due to the films being placed on the reflective surface of the TiN substrates, which allowed for changes in porosity to be analysed using ellipsometric porosimetry.
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