Common anion rule in oxide heterointerfaces: Experimental verification by in situ photoemission spectroscopy

The band alignment at the interface is one of the fundamental parameters for designing electronic devices and artificial functional materials. However, there is no firmly established guideline for oxide heterostructures, limiting the functional design of oxide heterostructures. Here, we provide spectral evidence that the band diagram of oxide heterointerfaces is well described by the Zhong and Hansmann scheme based on the common anion rule [Z. Zhong and P. Hansmann, Phys. Rev. X 7, 011023 (2017)]. By utilizing the elemental selectivity of Ti 2p–3d resonant photoemission for the Ti 3d state near the Fermi level, we directly visualize the presence or absence of charge transfer from the overlayer films to SrTiO3 in prototypical heterointerfaces of SrVO3/SrTiO3 and SrNbO3/SrTiO3. It is found that the charge transfer occurs in SrNbO3/SrTiO3 but not in SrVO3/SrTiO3, as predicted by the Zhong and Hansmann scheme, indicating that the presence or absence, as well as the sign and amount, of interfacial charge transfer is predicted by this scheme. Our findings provide guidelines for designing and controlling the functionalities in oxide nanostructures.