Single crystal RuO2/Ti and RuO2/TiO2 interface: LEED, Auger and XPS study

The interactions at the evolving RuO₂/titanium interface have been studied by LEED, AES and XPS. Titanium films of up to 5 monolayers were evaporated onto well ordered and ion sputtered ruthenium dioxide crystal surfaces of (110) and (100) orientation. Stabilization of the surface oxygen content under thermal treatment in UHV (up to 600°C) with increasing titanium coverage was established. After extended (up to 4 h) annealing in O₂ at 600°C an epitaxial ordering of TiO₂ on RuO₂(110) was observed. The (1 × 1) LEED patterns from the epitaxial layer exhibit a reduced background level when compared to the RuO₂ substrate itself. These findings are correlated with the XPS data and are interpreted in connection with the disappearance of the defect RuO₂ phase in the surface layer of the RuO₂. The appearance of the (1 × 2) surface reconstruction at the RuO₂(100)/Ti interface is discussed in the context of maximum cation coordination by oxygen atoms.