Bulk-defect dependent adsorption on a metal oxide surface: S/TiO2(110)

Molecular dynamics investigation of oxygen vacancy diffusion in rutile

“…Further oxygen vacancy diffusion towards the bulk, V O (12) to O(13), was not studied since the cluster used for the present calculations is not large enough to describe relaxation correctly around the defect. Oxygen vacancy diffusion V O (12) to O (13) occurs in a similar way as for V O (10) to O (12), except that Ti-O bonds perpendicular to the surface plane will be broken. Futher diffusion down from V O (13) proceeds via a mechanism similar to the V O (7) to O(10) diffusion.…”

“…During the experimental study of adsorption of sulfur on the clean and stoichiometric rutile (110) surface, Hebenstreit et al 10 found that at temperatures above 600 K sulfur atoms occupy the positions of two-fold coordinated bridging oxygens. We suggest the following explanation for this observation.…”

“…It is assumed that the formation of a TiS x layer during the adsorption of sulfur on the clean rutile (110) surface above 500 K is due to the migration of oxygen vacancies from bulk to the surface. 10 Dissociative adsorption of water molecules at temperatures near 500 K may be due to the increase in concentration of the surface oxygen vacancies, which act as the active centers for water dissociation. 11 In the case of NO 2 adsorption on the rutile (110) surface oxygen vacancy diffusion was observed above 300 K. 12 Activation energies for the diffusion of several transition metal cations were calculated by Ajayi et al 13 with classical potentials.…”

The interaction of size-selected Ru3 clusters with RF-deposited TiO2: probing Ru–CO binding sites with CO-temperature programmed desorption

“…It is probable that for oxidation the transport of O 2À anions on the substrate must be activated by heating such that they are mobilized and can be transported to the clusters; the idea of bulk TiO 2 defects becoming mobile at elevated temperatures and interacting with supported metals has been suggested previously. 30,33,91 Zhao et al 19 have previously deposited Ru 3 (CO) 12 by CVD onto TiO 2 (110). Aer heating and ligand removal the authors found that the Ru 3d 5/2 peak was located at 279.9 eV, which is comparable to bulk Ru.…”

Surface-based manipulation of point defects in rutile TiO2

“…By analogy with the previous work in which adsorbed N dramatically slowed the rate of self-interstitial injection into Si, 7 we performed isotopic exchange experiments in which a small quantity of sulfur was adsorbed after equilibration with natural abundance O 2 but before exposure to 18 O 2 . Sulfur was chosen because it occupies oxygen adsorption sites, 26 and can thereby interfere with the sequential steps of oxygen adsorption, dissociation, and injection into the underlying bulk. Sulfur was deposited controllably at room temperature via an electrochemical cell modeled on a published design, 27 and the coverage was measured by Auger electron spectroscopy.…”