XPS Study of the Electronic Properties of the Ce/4H-SiC Interface, and the Formation of the SiO2/Ce2Si2O7/4H-SiC Interface Structure upon Oxidation

The deposition and annealing in ultra high vacuum (UHV) of 5-6 monolayers (ML) of cerium on clean reconstructed Si-face 4H-SiC (0001) is studied by x-ray photoemission spectroscopy (XPS). Band bending as a function of annealing was studied by shifts of the bulk peak contribution in the C1s and Si2p spectra relative to the clean reconstructed surface. Additional datapoints for Schottky barrier formation on 4H-SiC are thus obtained by the low work function rareearth metals, and presented in the framework of the metal-induced-gap states and electronegativity model. A Ce/CeSi2-x/4H-SiC interface alloy forms by annealing to 850-1050oC. Kinetic information from the oxidation of the Ce/CeSi2-x/4H-SiC interface alloy is also reported. In particular, a SiO2- x/Ce-Si mixed oxide/4H-SiC forms upon oxidation. The shift of the C1s SiC-bulk-peak towards higher binding energies upon oxidation indicates that the mixed Ce-Si oxide interface layer appears to passivate the near Fermi-level 4H-SiC interface states at least as well as SiO2, and are expected to modify the electrical interface characteristics.