CONTOUR MAPPING AS AN INTERPRETIVE AND CALCULATIVE TOOL IN ALLOY SPUTTERING MEASUREMENTS

Using a sputter model which describes Gibbsian segregation in terms of chemical potential differences, the equilibrium surface and first sub surface layer concentrations under noble gas ion sputtering were calcu lated as a function of the bulk diffusion coefficient D and the segreg ation free energy DELTAG. It is shown by means of contour mappings tha t any surface/first bulk layer concentration combination corresponds t o a unique (D, DELTAG) pair. The contour mapping is also used to deter mine the (D, DELTAG) values for the system He --> Fe3Al by simply plot ting the first and second layer concentrations as measured by low ener gy scattering (ISS) on an overlaid contour mapping - thus eliminating tedious fit procedures. It is finally shown how these mappings, constr ucted for ISS-ISS data combination pairs, may be extended to ISS-AES a nd AES-AES combinations.