Surface segregation on Fe-25%Cr-2%Ni-0.1%Sb single crystals

Surface segregation of various segregating species has been investigated on Fe-25%Cr-2%Nd-0.1%Sb-N single crystals by AES and LEED. The experiments were performed on (100) oriented surfaces in the temperature range between 450 degrees C and 650 degrees C. At temperatures up to 500 degrees C, cosegregation of nitrogen and chromium is observed; the resulting CrN surface compound exhibits a characteristic (1 x 1) LEED pattern. For higher temperatures, antimony segregates to the surface accompanied by nickel, and replaces nitrogen and a large part of the chromium. This displacement process is reversible. The kinetics of the replacement of CrN by antimony and nickel depend on the pretreatment of the sample. A depth profile of the segregation layer of antimony and nickel shows that the enrichment of these elements is restricted to one monolayer. A surface covered by antimony and nickel yields a complex LEED pattern that is related to an imperfect c(2 x 2) structure. (C) 1999 Elsevier Science B.V. All rights reserved.