ESDIAD studies of the structure of TiO2(110) (1x1) and (1x2) surfaces and interfaces in conjunction with LEED and STM

The TiO2(110)-(1 x 1) surface and its reconstruction as a (1 x 2) form have been studied with low energy electron diffraction (LEED), electron stimulated desorption ion angular distribution (ESDLAD) and scanning tunnelling microscopy (STM). Oxygen ion desorption occurs within a lobe perpendicular to the (1x1) surface, changing to two off-normal lobes for the (1x2) reconstruction. This transformation in the ESDIAD pattern is consistent with the added Ti2O3 row model of the (1 x 2) reconstruction proposed by Onishi and Iwasawa. STM studies of the stoichiometric and electron irradiated surfaces reinforce the association of the O+ ESD contribution with majority sites at the surface. Adsorption of acetic acid on the (1 x I) surface produces a (2 x 1) overlayer and induces a reconstruction of the underlying substrate. ESDIAD reveals H+ ions emitted off-normally from dissociatively adsorbed acetate, and along the surface normal from surface hydroxyls. Adsorption of acetic acid on the (1 x 2) surface does not modify the LEED pattern, but ESDIAD reveals H+ desorption with a weaker off-normal contribution consistent with the Ti2O3 model of the reconstruction. (C) 1997 Elsevier Science B.V.