Thermally activated reconstruction of TiO2(1 1 0)-(1 × 1) surface in the presence of potassium: An STM study

The deposition of potassium onto TiO2(1 1 0) surface at 330 K and the effects of post-annealing are investigated by scanning tunneling microscopy (STM), thermal desorption spectroscopy (TDS) and Auger-electron spectroscopy (AES). At lower K coverages (a few percentage of a monolayer), 3–4 nm long and 1–2 nm wide islands appear which can be identified with K covered regions. At higher K coverages, the surface exhibits disordered structures. Depending on the initial K coverage, the annealing above 700 K in UHV results in ordering of the surface. For app. 1/3 monolayer K and annealing at around 900 K, the entire surface reconstructs into a (1 × 2) phase accompanied by the appearance of pits with an average diameter of 20–30 nm. This morphology is characteristic up to 1000 K. Above this temperature, the recovery of the (1 × 1) phase was observed. At low K coverages (<0.2 ML) the annealing at 1000 K resulted in the formation of protruding islands of approximately 2 × 2 nm2 which were identified with a strongly bonded surface compound containing K.

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► Reduction and reconstruction of an TiO2(1 1 0) surface activated by potassium.
► A complete (1 × 1) → (1 × 2) phase transition on TiO2(1 1 0) surface covered by potassium.
► K-induced formation of nanopits on TiO2(1 1 0) terraces.