Fig. 1.

Reaction of O₂ with TiO₂(110). (A) Ball model of TiO₂(110). Red and blue spheres denote O and Ti, respectively. The pink spheres are bridging O atoms, which lie in the [001] azimuth of the substrate. Parallel Ti rows that lie between the bridging-O rows are fivefold coordinated Ti atoms. Green spheres indicate H atoms (from OH_b). (B) 130 × 170 Å ² STM image (V = 1.5 V, I = 0.25 nA) of an as-prepared TiO₂(110) surface that contains O_b-vac and OH_b. OH_b forms from dissociation of water from the residual vacuum at O_b-vac. An O_b-vac, an OH_b, and an OH_b pair are indicated. (C) The surface in B after exposure to ∼90 L O₂ at 300 K. One of the bright spots assigned to O_ad is circled. B and C have been smoothed using Image SXM (12) v.1.75. (D) A histogram showing the height distribution of 276 bright spots found on the Ti_5c rows fitted to two Gaussian curves. The data are taken from an unsmoothed, larger version of the image in C. The histogram indicates that the reaction products are almost entirely from one species.