High resolution photoemission study of $SiOx/Si(111)$ interface disruption following in situ $HfO2$ deposition

We report on an in situ high resolution core level photoemission study of the early stages of interface formation between an ultrathin $SiOx$ layer $(∼0.3nm)$ grown on the atomically clean Si(111) surface and a $HfO2$ dielectric layer. Si $2p$ core level spectra acquired at 130 eV photon energy reveal evidence of a chemically shifted component on the lower binding energy side of the substrate peak which is attributed to interface defect states resulting from the incorporation of silicon atoms from the substrate into the interfacial oxide at room temperature. This evidence of $Si/SiOx$ interface disruption would be expected to increase charge carrier scattering mechanisms in the silicon and contribute to the generally observed mobility degradation in high-$k$ stacks with ultrathin silicon oxide interface layers.