Structural characterization of NiO films on Al2O3(0001)

NiO films on clean alpha-Al2O3(0 0 0 1) were prepared by molecular beam epitaxy. Two parameters were considered: the growth temperature (320-700 degrees C) and the film thickness (29-200 nn). Low energy electron diffraction (LEED) patterns of the deposits show a six-fold symmetry. The samples were ex situ characterized by atomic force microscopy (AFM) and by grazing incidence X-ray diffraction. For all samples, NiO islands with different sizes and shapes were observed. A layer of pyramidal NiO islands, with triangular facets is present. Depending on the sample, also hexagonal or square islands were observed. The angles of the triangular facets correspond to (1 0 0) surfaces of the NiO(1 1 1). X-ray diffraction evidences that the NiO film grows with the (1 1 1) plane parallel to the (0 0 0 1)Al, 0, one. Twinned and not-twinned face centered cubic (FCC) NiO(1 1 1) stacking are present in approximately equal quantities. The crystallographic quality of the NiO layers was investigated (C) 2000 Elsevier Science B.V. All rights reserved.