Surface segregation on Fe-25 %Cr-2 %Ni-0.14%Sb-N,S (100) single crystal surfaces

Surface segregation on (100) oriented single crystal surfaces of the alloy Fe-25%Cr-2%Ni-0.14%Sb-N,S has been investigated by means of Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). The experiments have been carried out in the temperature range from 500 degrees C to 700 degrees C in which a variety of segregation phenomena is observed. In the low temperature range, cosegregation of nitrogen and chromium occurs. Depth profiling and XPS studies suggest that the Cr and N segregation layer consists of (i) a two-dimensional surface compound and (ii) three-dimensional precipitates in the surface near region. A LEED investigation of the Cr and N saturated surface yields a clear (1 X 1) pattern after sufficiently long annealing times. At temperatures in excess of 600 degrees C, segregated nitrogen and chromium are replaced by segregating antimony and nickel. Studies of the kinetics show that nickel and antimony jointly enrich at the sample surface; this proves that true cosegregation occurs. An XPS study of the antimony and nickel saturated surface shows that the antimony binding energy coincides with the value that had been measured for the binding energy of segregated antimony on pure iron. The corresponding LEED pattern shows reflex splitting which indicates domain formation. A further increase of the temperature to about 700 degrees C causes segregation of sulphur displacing antimony from the surface. The sulphur covered surface exhibits a typical c(2 X 2) LEED pattern. (C) 2000 Elsevier Science B.V. All rights reserved.