Ultrathin SiO2-films on 4H-SiC(0 0 0 1) studied by angle-scanned photoelectron diffraction

X-ray photoelectron spectroscopy and angle-scanned photoelectron diffraction were used to investigate thermally grown ultrathin SiO2 films on 4H-SiC(0 0 0 1). Due to the chemical sensitivity of the applied methods it was possible to study different aspects of the films. A chemically shifted component in the Si 2p photoemission spectrum was ascribed to Si emitter atoms at the interface and allowed a determination of the interface structure between the ultrathin SiO2 film and the SiC substrate. The photoelectron diffraction pattern of another chemically shifted Si 2p component contained information about the local environment of near-interface Si emitters in the oxide film. This information was made accessible by means of an extensive comparison between experimental and simulated data. In the simulations the use of the cluster radius as a fitting parameter turned out to provide information about the range of local order in the oxide film. A chemically shifted component in the C 1s photoemission spectrum was used to study the structural properties of carbon contaminations, which were detected in the SiO2 layer after special preparation procedures.