Stoichiometric ScN and nitrogen deficient scandium nitride layers studied by photoelectron spectroscopy

The electronic structures of scandium nitride layers have been investigated by X-ray and ultraviolet photoelectron spectroscopies. The spectrum of stoichiometric ScN in the valence region is found to be consistent with the results of band-structure calculations, except for the width of the forbidden band of which evidence is only obtained by the experiments. Attempts to synthesise a non-stoichiometric ScN x compound failed. When layers deficient in nitrogen were grown, analysis of the electron core levels demonstrated that they were composed of mixtures of metallic scandium and stoichiometric ScN. This result is discussed in parallel with the titanium nitride case in terms of a vacancy stabilisation mechanism for transition-metal nitrides emphasising the role of the metal-metal interactions that form around a nitrogen vacancy.