Surface X-ray diffraction study on 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°C for 500 s at 2×10−6 mbar O2, the formation of epitaxial Al2O3 in a (2×1) superstructure was observed. Along the (2×1) superstructure reciprocal lattice rods, two different modulation periods could be detected. The shorter period arises from the growth of 2 nm high θ-Al2O3 oxide islands in monoclinic structure, the longer period from a 0.76 nm thick Al2O3 layer. This layer exhibits a θ-Al2O3-like structure with strongly modified Al ion positions at the surface and at the metal/oxide interface.