Formation of highly ordered Ca-overlayers on TiO 110/surfaces 2 studied by scanning tunneling microscopy and atomistic simulation

An ordered surface layer of Ca on TiO2 110.has been prepared and studied after annealing of a TiO2-rutile crystal. During the annealing process Ca impurities from the bulk segregate to the surface. A well ordered p 3=1.reconstruction has been observed by scanning tunneling microscopy STM.. Calculations have shown that the p 3=1.reconstruction has the lowest energy. Every third Ca ion in thew001xdirection is elevated by around 1 A° . Therefore, the STM contrast is mainly due to calcium and caused by geometry rather than electronic effects. q1999 Elsevier Science B.V. All rights reserved