Pulsed Laser Deposition of WOx and FeOx thin films
thesisposted on 11.09.2015 by Andrew J. Caruana
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The deposition of WOx and FeOx thin films by reactive PLD and post-deposition annealing in an oxygen environment have been investigated. The influence of the deposition parameters on the growth and structure of WOx as well as the electronic and structural properties of FeOx thin films are presented. WOx thin films have been deposited onto native oxide Si (100) and SrTiO3 (100) substrates, whilst FeOx films were deposited onto glass and MgO (100). The films have been analysed using X-ray diffraction (XRD), texture pole figure analysis, X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and resistance vs temperature measurements. The WOx films deposited on both Si and SrTiO3 substrates were found to exhibit a dependence on the primary texture with fluence in the range of 5.3 J cm-2 to 14.7 J cm-2. The WOx films deposited on SrTiO3 were observed to exhibit a biaxial texture whilst the films on Si displayed a (002) WO3 out of plane fibre texture. The primary texture of the WOx films on SrTiO3 was observed to evolve from (200)/(020) WO3 to a single (002) WO3 texture with increasing fluence. The FeOx films deposited via reactive PLD onto glass substrates were found to exist in the Fe2O3 oxidation state for all parameters used. The production of Fe3O4 by post-deposition annealing of Fe films on glass and MgO (100) substrates in an oxygen environment is also presented. On both substrates it was necessary to use a two-stage anneal process to produce Fe3O4; an initial 175 °C oxygen anneal followed by a 500 °C vacuum anneal. The presence of Fe3O4 was confirmed by the existence of the Verwey transition at close to 120 K, during resistance vs temperature scans. The anneal parameters required to produce Fe3O4 are shown to be different for MgO substrates in comparison to glass.