Compositional Studies

The richness of collisional phenomena associated with ion beam interactions with solids gives rise to a variety of techniques for compositional studies. These microanalytic techniques, which rely on the detection of characteristic signals generated in the collisions, may be classified broadly as either “destructive” or “nondestructive,” according to whether or not material is eroded from the sample to be analyzed. The ease with which the light emission of the sputtered species can be detected and identified is appealing for surface composition analysis and also for depth profiling if the amount of target erosion by the beam is also monitored. Large-backward-angle elastic scattering is widely used particularly in the regime where the well-known Rutherford cross section is applicable. For a given projectile incident on a target, this regime corresponds to a bombarding energy range, such that at the distance of closest approach in the collision, the screening of the atomic electrons is ineffective on the one hand and the short-range nuclear interactions are not significant on the other. Neutral-beam bombardment has been shown to be particularly attractive in the analysis of insulators in avoiding the charge-build-up problem. As in the case of secondary ion mass spectrometry (SIMS), however, the surface processes are incompletely understood, and the quantification generally requires the calibration of the experimental setup with known standards.