Correlation between Structural Phase Transition and Surface Chemical Properties of thin film SrRuO3/SrTiO3 (001)

Abstract

The correlation between the structural phase transition (SPT) and oxygen vacancy in SrRuO3 (SRO) thin films was investigated with in situ X-ray diffraction (XRD) and ambient pressure X-ray photoelectron spectroscopy (AP-XPS). In situ XRD shows that the SPT occurs from a monoclinic SRO (M-SRO) phase to a tetragonal SRO (T-SRO) phase near ~ 200 ℃ regardless of pressure environment. On the other hand, significant core level shifts in both the Ru and Sr photoemission spectra are found under ultra-high vacuum (UHV), but not under oxygen pressure environment. The directions and behavior of the core level shift of Ru and Sr are attributed to the formation of oxygen vacancy across the SPT temperature of SRO. The analysis of in situ XRD and AP-XPS results indicate the formation of metastable surface oxide possibly due to migration of internal oxygen atoms across the SPT temperature, signifying the close relationship between oxygen vacancy and SPT in SRO thin films.