Growth mechanisms for TiO2 at its rutile (110) surface

Mechanisms for growth on the rutile (110) surface were investigated using a combination of ab initio, variable charge classical molecular dynamics and kinetic Monte Carlo methods. Ab initio calculations were performed to determine relevant energy barriers and these were used to parameterise a variable charge classical potential. Low energy (10-40 eV) interactions of small Tix Oy clusters with a rutile (110) substrate were then investigated, by molecular dynamics using the variable charge potential, with the aim of determining the influence of various parameters on surface growth and defect formation. Rutile growth was simulated through sequentially depositing randomly selected clusters with energies in the tens of eV range. Long time scale evolution was approximated through heating the substrate and through on the fly kinetic Monte Carlo simulations which could be used to simulate realistic experimental deposition times. The main growth mechanism was found to involve a fast kinetic effect to sub-plant interstitial Ti atoms, until an O-rich surface layer formed, followed by a slower diffusion of the Ti interstitials to the O-rich surface. Bombardment at an energy of around 20 eV in an oxygen rich atmosphere with a high proportion of bombarding clusters, TiO, TiO2, as opposed to single atoms, was found to produce rutile growth with the best crystallinity.