Scattered ion yields from bimetallic crystal surfaces

For a number of bimetallic single crystal surfaces and ordered epilayers we investigated scattered ion yields. He+ and Ne+ ions in the energy range of 1-4.5 keV were used to study the systems CuAu, PdRu, AuRu, NiAl and FeAl. Choosing appropriate scattering conditions the contributions from the topmo st first and second atomic layers can be separated. Comparison of the measu red ion yields for different elements or with numerical simulations that do not include neutralization effects provides the possibility to identify re lative ion survival probabilities for scattering from different layers of t hese surfaces. The results show large differences for the various elements and emphasize the importance of the chemical nature of first layer species for ion yields from second layer scattering. Au and Cu in the first layer c ause a much higher neutralization rate than Al or Ru. Besides the relevance for neutralization processes these results are also important for quantita tive analysis of alloy surface layers by low-energy ion scattering (LEIS). (C) 1999 Elsevier Science B.V. All rights reserved.