Interfacial electronic structure of SrTiO3∕SrRuO3 heterojuctions studied by in situ photoemission spectroscopy

In situ photoemission spectroscopy (PES) has been performed on SrTiO3 (STO)∕SrRuO3 (SRO) bilayers to study the interfacial electronic structure of a SRO layer buried in STO. Using the interface (surface) sensitivity of PES measurements, the interface spectra of Ru 4d derived states near the Fermi level (EF) were extracted from the spectra of STO/SRO bilayers, as well as the surface spectra of SRO films. We found that the Ru 4d derived sharp peak at EF persists at the interface, while it smears out at the surface. These results suggest that the physical properties of SRO are maintained at the interface with STO.