Band alignment and electronic structure of the anatase TiO2/SrTiO3(001) heterostructure integrated on Si(001)

Using density functional theory (DFT), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS), we study the interface structure and electronic properties of the anataseTiO(2)/SrTiO3(001) heterostructure epitaxially grown on Si(001) by molecular beam epitaxy (MBE). We show that charge transfer at the TiO2/SrTiO3 interface is induced by the chemical bond formation between Ti and O. Subsequent O lattice polarization is found to be the leading screening mechanism at the interface. By comparing the theoretical local electronic structure to the O K edge EELS spectra taken at the interface with atomic resolution, we are able to trace how the local band structure evolves in response to the change in symmetry and bonding across the interface. We also discuss the effect of interfacial point defects (O vacancy and F impurity) on the band alignment.