Modeling the first activation stages of the Fe(hfa)2TMEDA CVD precursor on a heated growth surface

Iron oxide-based functional nanostructures are important technological materials that can be fruitfully obtained with high purity and tailored phase composition/morphology by Chemical Vapor Deposition (CVD). In this context, previous works have experimentally demonstrated the suitability of the Fe(II) diketonate-diamine complex Fe(hfa)2TMEDA as CVD precursor. However, further progress in the field strongly depends on the understanding of mechanisms governing the molecule-to-materials conversion, a goal that can be achieved by advanced computational methods. In this work, structural optimization of the Fe(hfa)2TMEDA molecule on a model CVD growth surface was performed to provide an insight on the physisorption geometry at 0 K. The first stages of thermally activated surface processes were then investigated by first principles molecular dynamics simulation, which revealed interesting aspects of the precursor behaviour at temperatures conditions typically adopted in Fe2O3 deposition experiments. Whereas the physisorbed complex maintains its octahedral geometry, high temperature interactions with the surface lead to drastic perturbations of the molecular structure and significant weakening of the coordination bonds of the metal center with the diamine ligands. Our results provide key elements for the fundamental knowledge of the temperatureinduced behaviour of this precursor on a heated substrate, which may help the understanding of its CVD activation mechanisms and decomposition pathways.