Oxidation of NiAl(1 0 0) studied with surface sensitive X-ray diffraction

Abstract

In this article surface X-ray diffraction experiments on the oxidation of the NiAl(1 0 0) surface will be described. Crystal truncation rod measurements show that the clean, flash-annealed surface is Ni terminated with an inward relaxation of the first layer of 3%. After oxidation at 950°C and 1×10 −6 mbar O 2 for 1000 s epitaxial oxide growth of θ-Al 2O 3 with monoclinic structure was observed, as determined from the oxide superstructure rods. The oxide layer forms a commensurate (2×1) superstructure with two in-plane domains that are rotated 90° with respect to each other. In addition, for each in-plane domain a twinning along the growth direction was revealed from the reflection splitting on the oxide layer superstructure rods, leading to a total of four different domains.