Electronic properties of the Ce∕4H-SiC interface studied by x-ray photoemission spectroscopy

Abstract

The deposition and annealing in ultrahigh vacuum of 5–6 ML (monolayers) of cerium on clean reconstructed Si-face 4H-SiC (0001) are studied by x-ray photoemission spectroscopy and low-energy electron diffraction. Band bending as a function of annealing was studied by shifts of the bulk peak contribution in the C 1s and Si 2p spectra relative to the clean reconstructed surface. Silicide formation was studied by low binding energy components in the C 1s and Si 2p spectra. A large relative upward band bending of 0.3–0.4eV takes place upon deposition of Ce on 4H-SiC at room temperature. Upon annealing to 350°C, a disordered CeSixCy interface layer forms, as observed from chemically shifted components in the Si 2p and C 1s spectra. Annealing to 600°C causes the interface to become CeSi2−x, and carbon desorbs from the interface. A maximum relative band bending of 0.6eV is observed from 400to600°C. Further heating of the sample to 850–1000°C results in a relative total upward band bending of approximately 0.4eV and a relatively sharp CeSi2−x peak in the Si 2p spectrum. SiC bulk bonds appear not to be broken and it is found that a Ce overlayer terminates the layer, with a cerium silicide layer at the interface.