Epitaxial growth of NiO layers on MgO(0 0 1) and MgO(1 1 0)

About 33 nm thick NiO layers have been epitaxially grown on MgO substrate at 900°C. Investigations by X-ray diffraction, atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM) give evidence for a close relationship between surface morphology and substrate orientation. Deposited on MgO(0 0 1) surface, the NiO layer grows layer by layer leading to a flat NiO(0 0 1) surface. On the contrary, the surface of the NiO layers grown on MgO(1 1 0) has a roof-like morphology consisting of (1 0 0) and (0 1 0) facets elongated along the [0 0 1] direction. This particular surface configuration comes from a mechanism of surface energy relaxation during the growth process.