Photoemission study of SrTiO3 surface layers instability upon metal deposition

In this work we study the Pt/SrTiO3 (STO) interface system using X-ray photoelectron spectroscopy (XPS). The polycrystalline Pt layers with a thickness of about 2-3 nm are deposited by sputtering and thermal evaporation methods on STO(100) single crystals with two different type of terminations. We propose and show local conductivity (LC) measurements as a good method to check whether such very thin metal layers are continuous. The XPS data show that both methods of Pt deposition lead to changes of the chemical composition of the crystal surface layers, and such chemical instability should be taken into consideration when studying the physical properties of a metal-insulator interface.