Stability and stoichiometry of (polar) oxide surfaces for varying oxygen chemical potential

Polar oxide surfaces constitute a class of surfaces long considered as unstable because of their theoretically predicted diverging electrostatic surface potential, although such crystal orientations form spontaneously in nature. Because of the intrinsic hindrances (charge build-up, electron correlation effects) a reliable description of such surfaces necessitates a combined theory-experiment approach. Experimentally, detailed investigations became possible in recent years because of the availability of charge build-up insensitive techniques such as surface x-ray diffraction, which is thoroughly used in the presented work. We consider here prototypical polar oxide surfaces of different crystalline structures and show that their stability regime strongly depends on the external conditions applied to the surface in terms of oxygen chemical potential. In order to understand the structure and stability of polar oxide surfaces, their chemical environment must be included.