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Growth mechanisms for TiO 2 at its rutile (110) surface

2011; American Physical Society; Volume: 83; Issue: 7 Linguagem: Inglês

10.1103/physrevb.83.075412

1550-235X

Louis James Vernon, S.D. Kenny, Roger Smith, Edward Sanville,

Electronic and Structural Properties of Oxides

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 (KMC) methods. Ab initio calculations were performed to determine relevant energy barriers, and these were used to parametrize a variable charge classical potential. Low-energy (10--40-eV) interactions of small ${\mathrm{Ti}}_{x}{\mathrm{O}}_{y}$ molecules 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 atoms and molecules with energies in the tens of eV range. Long-time scale evolution was approximated through heating the substrate and through on-the-fly KMC simulations, which could be used to simulate realistic experimental deposition times. The main growth mechanism was found to involve a fast kinetic effect to subplant 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 TiO, ${\mathrm{TiO}}_{2}$, as opposed to single atoms, was found to produce rutile growth with the best crystallinity.