NRRA - Nuclear Resonant Reaction Analysis
Depth Profiling of Hydrogen using the 15N Method:
This method allows the absolute measurement of the H-concentration as a function of the depth.
The major advantage of this method is, that no sample specific reference standard is needed. The nuclear reaction of 15N ion beam with the hydrogen contained in the sample produces characteristic gamma radiation. It takes place almost only at an ion energy (resonance energy) of 6.4 MeV. Therefore, a 15N beam of higher energy does not probe the surface of the sample. However, the sample is probed in a certain depth, because the ions are loosing energy when penetrating the sample material. For a selected beam energy the 6.4 MeV is reached after a definite path length. Starting with a 6.4 MeV ion beam (surface), the energy is increased step by step to measure the hydrogen depth profile of a sample.
Typical Parameters , pros and cons:
- gives the absolute H concentration
- no standard needed
- resolution of depth ≈ 10 nm (surface)
- depth profile 0 - 3 µm
- lateral resolution ≈ 3 mm
- sensitivity <100 at ppm
- sample time ≈ 1 - 2 hour / profile
- non-destructive method
- H-content of some samples is instable under ion beam irradiation