Effect of alloying on ion-bombardment-induced surface topography on face-centred cubic metals

Abstract

Previous studies of sputter-induced topographical development have shown that it is possible to form pyramids on single-crystal fcc metals oriented in the 〈1131〉 crystallographic direction. These pyramids form when the surface is bombarded with relatively large (> 1 × 1019cm−2) doses of Ar+, Kr+ or Xe+ ions in the energy range 20–41 keV. Until recently most of the work was con to pure fee metals (Cu, Pd, Ir, Ag, Au), all of which exhibit similar pyramid formation on bombardment. Later studies involving 〈1131〉 Cu, however, showed that, although pyramids form with inert-gas ion (e.g. Ar+ on Cu) or self-ion (Cu+ on Cu) bombardment, they are not produced when either Br+, Fe+ or Ni+ ions are used. This observation led to further investigations of alloying effects on topographic evolvement during sputtering. We report here a study of the influence of alloying on pyramid formation on 〈1131〉 single crystals, through comparison of that of Ni and Cu with that of Ni-8%Cu. We find that bombardment with Ar+ ions can produce pyramids on Ni-8%Cu but that the conditions necessary are different from those for pure metals. We have looked for sputter-induced segregation effects in the alloy but none have been observed.