Atomic and valence-band electronic structures of the epitaxial SiON layer on the SiC(0001): X-ray diffraction and angle-resolved photoemission spectroscopy investigations

Atomic and valence-band electronic structures of a recently discovered epitaxial silicon oxynitride (SiON) layer on a 6H-SiC(0001) surface were investigated with x-ray diffraction (XRD) and angle-resolved photoemission spectroscopy (ARPES). The atomic structure optimized by XRD analysis well agrees with a previous low-energy electron diffraction analysis and a first-principles calculation. Band dispersions of surface states observed by ARPES can be explained by the previous calculation. Interface states intrinsic to the SiON layer were not observed above the valence-band maximum of SiC, but a diffuse, non-dispersive state was found by ARPES. Its origin is suggested to be a by-product of graphite-like clusters formed on the SiON layer during heat treatment.