Mg interaction with TiO2(100): MIES and UPS(HeI) results

The interaction of Mg with TiO2(100)-(1 x 3) surfaces at room temperature w as studied with metastable impact electron spectroscopy (MIES) and ultravio let photoelectron spectroscopy. In the early stage of Mg exposure a charact eristic initial decrease of the surface work function by about 2 eV and a c oncomitant rise of the yield for formation of Ti3+ 3d-cations is observed; charge transfer from Mg adsorbates to Ti cations takes place. Ionically bon ded Mg species seem to play a key role as nucleation sites. In the MIES spe ctra Mg-induced emission is found in the band gap of titania. This emission involves Mg3s electrons that are involved in bonds formed between the ioni cally bonded Mg+ species and additional Mg atoms. Initially, the Mg layer s hows 2D growth. From the exposure dependence of the Mg3s-induced MIES signa l a critical coverage of about 0.35 ML for the transition from 2D to 3D gro wth is derived. (C) 2001 Elsevier Science B.V. All rights reserved.