This is a copy of the slides presented at the meeting but not formally written up for the volume.

Oxygen nonstoichiometry plays a major role in the physics of complex oxides with perovskite structure, also because of its effect on carrier density. Such issue has been systematically investigated in the multichamber system recently set up in our labs, equipped with a RHEED/PLD chamber for thin film growth, and with two XPS/SPA-LEED, and STM/AFM chambers for sample characterization. Variable temperature electron diffraction and photoemission experiments, complemented by scanning probe analyses, were performed in our system in order to systematically address the influence of thermodynamic conditions on oxygen content. SrTiO3-x, in particular, was taken as a prototypical example of an oxygen deficient perovskite for most experiments. The configuration of oxygen vacancies in the terminating TiO2 layer appears to be influenced by the presence of surface steps.