Ca-induced surface reconstructions on TiO2(1 1 0) studied by scanning tunneling microscopy, reflection high-energy electron diffraction and atomistic simulation

We have prepared and investigated Ca-induced surface reconstructions on TiO2(1 1 0). Experimental investigations were carried out by scanning tunneling microscopy (STM), reflection high-energy electron diffraction, low-energy electron diffraction and Auger electron spectroscopy. Atomistic simulation was used to study the segregation behaviour of calcium and to calculate the surface structure. In good agreement between experiment and calculations the (3×1) surface reconstruction was found to consist of elevated Ca2+ ions in the top layer of the surface. This strongly suggests that the STM contrast is mainly of geometric origin. After further oxygen loss trenches are formed on the surface which can be described as a disordered (1×4) reconstruction. Though energy calculations did not show a significant energy gain by forming the trench structure it is suggested that oxygen loss and subsequent elastic interaction contribute to their formation.