Sputtering and RBS investigations of ordered and disordered Ni4Mo

The crystal structure of Ni4Mo is known in two modifications, viz. an ordered and a disordered one. The molubdenum atoms are situated in lattice positions of the fcc Ni structure in a sublattice or randomly, respectively. The fcc Ni lattice has a tetragonal distortion. Single crystals of Ni4Mo in the two modifications have been prepared with the [001] axis perpendicular to the surface. They were bombarded with 80 keV Ar+ ions along the [001] or the <110> directions with fluences up to 4x1018 cm-2. The sputtered material was collected on a hemicylindrical aluminum foil and analyzed using Rutherford backscattering of 500 keV He2+ ions. In addition, weight loss measurements and RBS analyses of the implanted crystals in different crystallographic orientations were performed. The RBS analyses show no distinct difference between the ordered and disordered crystals. Wehner spots were not observed for any ejection angle in contrast to comparative measurements made on a pure (001) Ni crystal. The angular distribution of the sputtered materials is broader for nickel than for molybdenum, indicating segregation of nickel to the surface. (orig.)