Surface lattice structure and dynamics of rutile titanium dioxide(110)

Surface structure and dynamics of the rutile TiO₂(110) is investigated using high resolution helium atom diffraction and single phonon inelastic scattering experiments. This work is the first investigation of the chemically interesting and dynamically complicated surface of TiO ₂(110) using helium atom scattering. The surface preparation method by itself raised a question about the possibility of conducting measurements due to extreme sensitivity of helium atoms to order-disorder on the surface. The surface suitable for helium atom scattering measurements is successfully prepared and indeed exhibits a number of interesting features. To date no theoretical calculations have been performed on this surface for the study of vibrational modes. Surface phonon dispersion curves are obtained and vibrational modes, together with ionic motion patterns are identified with the guidance from theoretical results obtained for MgF₂(110). Both crystals have the same rutile structure and appear to yield very similar (110) surface dynamical measurements with the exception of the effect from difference in atomic masses. Surface structural features observed earlier with STM and AFM on stoichiometric rutile surfaces are shown to agree with helium diffraction measurements. When extensively annealed, the surface undergoes significant structural changes likely forming crystallographic shear regions which are displayed in surface structural measurements as additional Bragg peaks, unbalanced Bragg peaks etc. These effects are also studied, although not as extensively as surface phonon dispersion relations, but represent good preliminary measurements.