Structural investigation of the NiO(111) single crystal surface

We report an in situ grazing incidence X-ray scattering study of the NiO(lll) single crystal surface. it evidences a relatively high stability of this surface. After an air anneal at 1300 K it is flat and almost not reconstructed. Annealing at 860 K in ultra-high vacuum leads to two domains: one covered by epitaxial and relaxed metallic Ni clusters associated with a highly ordered interfacial supercell on the coincidence sire lattice, presumably a misfit dislocation network and one exhibiting a p(2 x 2) reconstruction. After oxidation the metallic Ni transforms again into NiO(lll) and only a p(2 x 2) reconstructed flat surface remains. In these conditions macroscopic (100) Facetting was never observed. The general behaviour of the NiO(lll) surface is discussed and compared with other polar and non-polar oxide surfaces, with emphasis on the specific properties which could explain its stability. (C) 1997 Elsevier Science B.V.