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Elastic Recoil Detection Analysis (ERDA)

Elastic Recoil Detection (ERD) is a ion beam analysis technique for quantitative analysis of light elements in solids. The sample to be analyzed is irradiated with an ion beam (e.g. He, C or O ions) of several MeV energy. Light elements (e.g. H, D, Li) from the sample are scattered in forward directions and can be detected with a Si detector. From the measured energy spectrum of the recoils a concentration depth profile can be calculated.

The detection of scattered ions from the incident ion beam is normally suppressed in order to avoid background. The easiest and most common method is the use of a foil which stops the scattered ions, but allows the passing of the recoils.

For low ion energies (<0.3 MeV/amu) the scattering cross section can be calculated assuming Rutherford scattering. For higher energies experimentally measured cross section have to be used in most cases. The depth profile calculation can be done directly from the spectrum. The accuracy is about 10%, limited by the uncertainties in the stopping power values of the sample material, experimental cross section values and geometrical uncertainties.

The ERD method provides absolute concentration values and is not affected by matrix effects. Furthermore ERD is non invasive, e.g. the sample is not damaged on a macroscopic scale.

Elastic Recoil Detection Analysis