Stimulated desorption induced by hydrogen aggregates (E ≤120 keV/u) and by heavy ions (E ≤ 400 keV/u). Analytical applications

This work presents an original group of results on stimulated desorption induced by Hn+ clusters (n up to 61) at 600 keV on insulating samples. This phenomenom has been applied to surface microanalysis using both these particles and MeV argon ions. A time of flight spectrometer is used for the secondary ion detection. As far as clusters are concerned and for CsI material it is shown that the Cs+ yield varies quadratically with the stopping power for these cluster, both above and below the BOHR velocity, v0. Such a trend is based on a coherent interpretation of the role of collective and individual interactions leading to the energy deposit. The study of H+ variation is not only in agreement with this interpretation but also gives some new informations on the interaction below v0. As for the organic material, phenylalanine, we show the qualitative applicability of the model of intact molecule desorption from the periphery of the primary particle track. The high values of the measured ion yields (up to 100%), allows the use of low intensity ion beams using collimators of 2 μm diameter. The optimum lateral resolution has not been obtained with clusters due to technical limitations, but with the Ar ion irradiation system; a value of 10 μm has been obtained. On the other hand, marked differences have been observed between various alkali compounds, for which we make a tentative interpretation. Finally the evolution of desorption yields with the particle fluence constitutes an insight into the role played by the energy density on material modification under irradiation