**5. Application examples**

The examples of analyses below have been selected from the literature to highlight some of the relative strengths (and weaknesses) of the two IBA techniques discussed in this chapter.

#### **5.1 ERDA analysis of an alumina-titanium layer stack**

**Figure 4** shows results of ERDA depth profiling of an Al2O3/Ti/Al2O3/Ti/Si bilayer film annealed at 800°C in vacuum [20], to study the Al2O3-Ti solid state reaction. The measurement was carried out using a 26.1 MeV 63Cu7+ beam, with a time-offlight (ToF) recoil detector mounted at 30o (φ = 150<sup>o</sup> in **Figure 1**) to the incident beam direction. Further details of the measurement set-up are given in Msimanga et al. [20]. Coincidence measurement of the ToF and energy of atoms recoiled from the target sample allows for their separation according to mass. The 2-D scatter plots in

*Depth Profiling of Multilayer Thin Films Using Ion Beam Techniques DOI: http://dx.doi.org/10.5772/intechopen.105986*

**Figures 4a** and **c** show all the elements detected from each target sample, as well as the forward scattered incident 63Cu beam. The shape of the scatter plots derives from the simple inverse relationship between the ToF and kinetic energy *E*<sup>r</sup> of the recoil atoms; *ToF* <sup>¼</sup> ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi *mr=*2 *Er* p ∙*L*, where *m*<sup>r</sup> is the recoil atom mass and *L* is the length of the flight path. For a given atomic species, atoms recoiled right from the surface will be detected with higher energy (i.e. shorter ToF) than those from deeper layers due to energy loss of the latter as they move through, and out of the sample. And for a given energy *Er*, the ToF increases as the particle mass increases, i.e. heavier atoms move slower, hence the observed separation of recoil atoms in terms of mass.

The depth profile of the as-prepared sample is shown in **Figure 4b** and that of the annealed one in **Figure 4d**. To get a sense of the analytical depth shown, if the depth scale is converted to units of nanometres using known atomic densities of the Al2O3 and Ti, the Ti/Si interface is about 150 nm from the surface in **Figure 4b** and shifts to just under 140 nm in **Figure 4d**, indicating silicide formation at the interface. The advantage of such 'raw' depth profiles, calculated using the direct energy-to-depth conversion code KONZERD [16] is that they give a quick visual description of the layer structure, with no need for a standard or reference sample. This provides a good starting point for further, more detailed analysis through MC simulation codes as described in ref. [20].
