The influence of electrode material on the resistance degradation of Fe-doped SrTiO3

Resistance degradation, a common phenomenon in high permittivity dielectrics such as Fe-doped BaTiO3 or SrTiO3, occurs under dc voltage and temperature stress and limits the application temperature window. Based on the... [ view full abstract ]

Resistance degradation, a common phenomenon in high permittivity dielectrics such as Fe-doped BaTiO₃ or SrTiO₃, occurs under dc voltage and temperature stress and limits the application temperature window. Based on the internal migration of oxygen vacancies towards the cathode, the increase of current with time can be described quantitatively. In order to study the influence of the oxygen migration on the electrode interface properties, we have performed combined resistance degradation and photoemission experiments on Fe-doped SrTiO₃ single crystals. Asymmetric contacts with a thick and thin electrode have been deposited onto the SrTiO₃ crystal surfaces by magnetron sputtering to form capacitor structures. The thin electrodes were used for analyzing the chemical and electronic properties of the interfaces by X-ray Photoelectron Spectroscopy before and after degradation respectively. In order to avoid island formation, thin conducting oxide electrodes have been used instead of the common Pt electrode. Several electrode materials with different work functions were compared as well by various combinations of electrodes. The experiments revealed that the degradation behavior depends strongly on electrode material and polarity. Moreover, degradation is clearly identified to be accompanied by a reduction of the substrate at the cathode interface.