Band alignments in oxygen-deficient HfO₂/Si(100) interfaces

We investigated the band alignment across the interface between an oxygen-deficient HfO_x<2 film and Si(100) by using photoelectron spectroscopy with X-ray and ultraviolet photon sources. The Fermi level in the system is determined from the core level binding energy in the X-ray photoelectron spectra and from the onset energies of secondary electrons in the ultraviolet photoemission spectra. Considering the effects of post-annealing and oxygen introduction on the film characteristics, we analyzed the band lineups across the interfaces by adopting the contemporary concept of charge neutrality level at the interface.