Modification of the Schottky barrier height at the RuO₂ cathode during resistance degradation of Fe-doped SrTiO₃

The long-term stability of electronic devices at high temperatures and electric fields might be strongly influenced by the electronic properties of interfaces. A modification of Schottky barrier heights at electrode interfaces of functional oxides upon changes of the external oxygen partial pressure is well documented in literature. In this work, an experimental approach using X-ray photoelectron spectroscopy is presented, which enables to study transient changes in the Schottky barrier height induced by electrical degradation. A rise of the Fermi level at the RuO₂ cathode interface of Fe-doped SrTiO₃ single crystals by 0.6 eV is observed in the course of resistance degradation. The change of the effective barrier height is associated to the migration of oxygen vacancies towards the cathode and accompanied by the observed reduction of Ti. Different scenarios are discussed to explain the origin of barrier modification and the localization of the reduced Ti.