Phd In Chemical Vapour Deposition Of Complex Ferroic Oxide Thin Films
Cork, Ireland
During my PhD, I have developed novel chemical vapour deposition (CVD) route for the fabrication of oxide ferroelectrics and multiferroics. Highlights of my PhD work are as follows:1. A versatile layer-by-layer growth mode was developed to prepare naturally super-latticed bismuth-based materials belonging to the Aurivillius phase family, with which good control over composition and crystal structure was achieved. 2. The effect of epitaxial strain on one of the very simple oxide materials TiO2 was studied. It has been found that the ultra-thin TiO2 films demonstrate ferroelectric behaviour when grown on NdGaO3 substrates. 3. A unique growth method for multiferroic BiFeO3 (BFO) thin films is shown, where a phase pure BFO thin films can be prepared even in the presence of excess bismuth precursor during the growth process. This type of growth is usually called adsorption controlled growth and can be used for growing various bismuth-containing compounds, where the volatility of bismuth can create various types of defects.4. The growth of Bi4Ti3O12 thin films was performed in a layer-by-layer growth mode. The effect of Bi and Ti precursor flows on the growth of thin films is discussed and it is shown that how the change in precursor flows leads to out-of-phase boundary defects during the layer-by-layer growth mode. 5. The growth of a compound Bi5Ti3FeO15, which is a 1:1 mixture of BiFeO3 and Bi4Ti3O12, is presented. The growth mechanism of Bi5Ti3FeO15 thin films is presented, where the Fe precursor flow was controlled from zero to the insertion of one full BiFeO3 perovskite unit cell into the Bi4Ti3O12 structure.
