The first step is to determine whic

The first step is to determine which of the two components, if any, is surface related. Figure 2 shows the Ba3d peak from the polished surface obtained at two different takeoff angles. The idea behind this study is that the higher the angle between the detector and the average surface normal, the more surface sensitive the spectrum (normal detection leading to highest average escape depth and, therefore, minimum surface sensitivity). Figure 2 shows that at normal takeoff angle, the peak is predominantly a. When glancing angle (80°) is used, increased surface contribution leads to an increase in the /3 component. Therefore, yS is the component that is richer at the surface. On mechanically polished samples, it forms a very thin layer on the bulk, a phase.When the surfaces are annealed, the thickness of the (3 phase increases to cover the entire detected volume at normal detection (10-20 A). Annealed samples therefore show the same peak shape [mostly /3 as in Fig. l(b)] for all takeoff angles.