Surface geometrical structure and incommensurate growth: Ultrathin Cu films on TiO 2(110)

Abstract

The TiO 2(110) surface geometrical structure and the growth at room temperature of ultrathin Cu film on the titanium dioxide (rutile) substrates have been examined by means of low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). For clean TiO 2(110) surfaces it is found that there is a reversible structure change between (1 × 1) and (1 × 2) surfaces over a 450–700 °C annealing temperature range. Based upon the spectra features and the LEED observations we propose a missing-row model for the (1 × 2) surface, a model for which the mechanism is revealed to be due to a competition of diffusion of the bulk lattice-oxygen to the surface and desorption of the surface oxygen into vacuum. Cu deposition on the TiO 2(110) surface causes a combination of adsorption in registry with the substrate unit mesh along the [1 1 0] direction and an incommensurate growth, forming a slightly contracted hexagonal superlattice leading to a (111) oriented Cu overlayer. The surface geometry of protruded one-dimensional oxygen rows of TiO 2(110) is an important factor in establishment of this superlattice. The Cu adatoms apparently grow as islands upon the initial monolayer, i.e. in a Stranski-Krastanov growth mode.