Surface Science

Structure and epitaxy of anodic TiO2/Ti(1120)

View publication


We report the results of a study by synchrotron X-ray scattering of the anodic oxide formed on Ti(1120). The oxide was grown slowly by ramping the potential to 9-10 V at 0.1 mV/s in 0.1N H2SO4. We find that the film consists of crystalline TiO2, present in nearly equal amounts as rutile and anatase. There is no evidence for amorphous oxides or oxides with stoichiometry different from TiO2. The rutile is orietationally ordered to within 8° of the Ti substrate; its tetragonal a- and b-axes are in the Ti[1100] and [0001] directions, and the c-axis is along the surface normal. The rutile diffraction peak widths correspond to an average in-plane domain size of 40 Å. The anatase has domains twice this size, but it is not as orientationally ordered as the rutile. The dominant anatase orientation has its (013) planes in the surface, rotated azimuthally so that the near-neighbor Ti-Ti bonds are matched as closely as possible between the Ti and the oxide. Because both rutile and anatase have well-defined orientations with respect to the Ti substrate, but not to each other, we propose that both oxides are formed at the metal/oxide interface. © 1992.