Concentration profile of light elements near interface

The knowledge of depth concentration of atoms introduced by diffusion or implantation in thin layers is essential, but it is difficult to measure. Nuclear resonant reaction analysis is a powerful technique to determine the depth profile of light elements in a matrix. These reactions occur often in the low energy range by accelerating protons or alpha particles with a Van de Graaff accelerator producting resonant reactions in the diffused atom. The depth resolution at surface depends on the resonance width used and the beam energy resolution. The exact localization of the interface remains a problem. The reason is that in the NRA technique, the depth is calibrated using the energy loss of the particle as measured by the magnetic analyser. This scale, however, should be converted into . Moreover, in the case of depth profiling measurement, the density is not uniform. The different origins of errors are: accuracy of the stopping power parameter, validity of Bragg's rule, exact composition of the layer and inhomogeneity. We describe a method that we have used since several years, which reduces considerably these uncertainties. It consists of measuring the energy loss in the thin layer by RBS near resonance energy. The depth profile at interface is then calibrated from the direct observation (RBS) without using stopping power parameters. The method is also insensitive to concentration variations in the surface layer. We used this method for Na, F, Al, in the study of glass coatings. It can be used for all the elements that can be analysed by nuclear resonant reactions.