Rocksalt-structured nitride films were grown on MgO(001) substrates, by molecular beam epitaxy, using a radio-frequency plasma source for N. The case of Sc-rich growth conditions, which occurred when the Sc flux exceeded the N flux, was considered. Despite the excess Sc during growth, reflection high-energy electron diffraction and X-ray diffraction showed that these films had only a single orientation, of (001), and ion-channeling confirmed good crystallinity. Rutherford back-scattering showed that these films were non-stoichiometric, and this was found to be directly related to variations in the N, not the Sc, content by secondary ion mass spectrometry. High-resolution X-ray diffraction reciprocal lattice mapping showed that these variations in the N content were related to the existence of the N vacancies. It was concluded that Sc-rich growth led to the incorporation of N vacancies into the crystal structure, the concentration of which depended upon the Sc/N flux ratio. In addition, excess-Sc conditions at the surface were explored by means of in situ scanning tunnelling microscopy. Observed wider terrace widths, as compared to N-rich growth, were due to an increased surface diffusion which was attributed to a Sc-rich metallic surface structure. Combined with the large dislocation density, the enhanced diffusion results in a predominantly spiral growth mode.

Phase Stability, Nitrogen Vacancies, Growth Mode and Surface Structure of ScN(001) under Sc-Rich Conditions. H.A.H.Al-Brithen, E.M.Trifan, D.C.Ingram, A.R.Smith, D.Gall: Journal of Crystal Growth, 2002, 242[3-4], 345-54