The band line-up at the 4H-SiC/Ni interface was determined using X-ray photoemission spectroscopy (XPS). Ni was deposited in 14 steps on an ex situ cleaned n-type 4H-SiC substrate starting with an initial deposition of 0.5 Angstrom up to a final thickness of 110 Angstrom. The sample surface was characterized in situ by XPS before the growth sequence, and after each Ni deposition step. Analysis of the Ni 3d and O 1s core level peaks indicates that a thin Ni oxide layer was formed at the interface due to a chemical reaction with oxidizing agents on the sample surface due to the ex situ substrate preparation before a metallic Ni film could be grown. The substrate core level spectra exhibit a significant shift to lower binding energy due to the development of an inversion condition in the semiconductor at the interface. This resulted in the formation of an electron injection barrier of 3.26 eV at the interface. (C) 2004 Elsevier B.V. All rights reserved.