Surface X-ray diffraction study ion the initial oxidation of NiAl(100)

The oxidation behavior of NiAl(100) surfaces was studied using surface X-ray diffraction. After oxidation of the preferentially Ni-terminated surface at 950 degreesC for 500 s at 2 x 10(-6) mbar O-2, the formation of epitaxial Al2O3, in a (2 x 1) superstructure was observed. Along the (2 x 1.) superstructure reciprocal lattice rods, two different modulation periods could be detected. The shorter period arises from the growth of 2 nm high theta -Al2O3 oxide islands in monoclinic structure, the longer period from a 0.76 nm thick Al2O3 layer. This layer exhibits a theta -Al2O3-like structure with strongly modified Al ion positions at the surface and at the metal/oxide interface. (C) 2000 Elsevier Science B.V. All rights reserved.