Surface preparation of TiO2 anatase (101): Pitfalls and how to avoid them

Fermi Level Positions and Induced Band Bending at Single Crystalline Anatase (101) and (001) Surfaces: Origin of the Enhanced Photocatalytic Activity of Facet Engineered Crystals

“…The surface orientation has been confirmed by low energy electron diffraction (see Figure S2, Supporting Information). [12] The O vacancy concentration for the (101) and (001) surface prepared by the procedure is estimated to be 7 ± 2 and 1 ± 2%, respectively. Sample preparations and measurements were carried out in the Darmstadt integrated system for materials research (Daisy-Mat) [22] equipped with a multitechnique surface analysis system Physical Electronics PHI 5700 capable of XPS and UPS, which is connected to different sample preparation chambers without breaking vacuum.…”

“…Sample preparations and measurements were carried out in the Darmstadt integrated system for materials research (Daisy-Mat) [22] equipped with a multitechnique surface analysis system Physical Electronics PHI 5700 capable of XPS and UPS, which is connected to different sample preparation chambers without breaking vacuum. [12] In addition, atomic O in the O plasma is more oxidative than a molecular O 2 during annealing in O atmosphere. Although this procedure has been conventionally accepted to prepare clean surfaces of single crystal TiO 2 , [8,23] Ar sputtering not only results in a highly reduced surface and thus leads to the formation of O vacancies and Ti 3+ surface states, but also partially destroys the crystallinity of the surface and introduces an amorphous phase.…”

Oxygen partial pressure dependence of surface space charge formation in donor-doped SrTiO3

“…15 Complementing defect chemical considerations, at lower temperatures, the presence of charged adsorbates might influence n-SrTiO 3 surfaces in oxidizing conditions. Setvin et al showed the existence of oxygen molecules forming superoxides at TiO 2 surfaces below 300 K. 23,24 Similarly, charged oxygen adsorbate species are proposed on perovskite surfaces at comparably high temperatures, their concentration diminishing with increasing temperature though. 25 Far above room temperature, the presence of any of those oxygen species on n-SrTiO 3 surfaces is still unconfirmed and any effect on the space charge formation has not been quantified so far.…”

“…25 Far above room temperature, the presence of any of those oxygen species on n-SrTiO 3 surfaces is still unconfirmed and any effect on the space charge formation has not been quantified so far. Thus, up to now, it is not known, whether intrinsic electronic surface states, 11 or unintentional defect layers due to carbonate adsorbates, 4 or possibly chemisorbed charged oxygen molecules such as observed for TiO 2 , 23,24,26 or intrinsic ionic surface defects, namely, V Sr , 15 can cause the observed surface space charge layer effect in n-SrTiO 3 13 and its dependence on the oxygen partial pressure (pO 2 ).…”

“…Such a formation of a surface coverage with chemisorbed oxygen species is considered typically at room temperature and below. 23,24 However, the existence of charged oxygen species at elevated temperatures has been discussed on other perovskite type oxides (e.g. (La,Sr)MnO 3 δ 25 ), with finite concentrations up to 1000 K and thus might be considered on SrTiO 3 , too.…”