Abstract : We have performed an experiment at GANIL with a beam of Pb72+ and Pb56+ ions at 29 MeV/u and Pb28+ at 6,5 MeV/u. We observed the sputtering of positive ions at the entrance of a thin germanium crystal as a function of the incident charge and of the energy loss of the transmitted ions. We found that the sputtering is composed mainly of ions which come from the surface impurity layers, and from the fragmentation of large species. For an energy deposition below the amorphous layer, the dependence of the multiplicity on the charge q is qn where n3. The dependence of the yields on the charge is qn, where n varies between 2 and 6 depending on the emitted species. For a particular incident charge, we observed differential effects with the energy loss in the crystal, for the multiplicities, the yields and the fragmentation probability. The intensity of these effects is almost constant for all species issued in the case of the high energy beam. At low energy, this effect varies from one species to another, and, in the average, it is stronger than at high energy. These effects are related both to the emission depth for each species and to the density of energy deposition around the ion path below the amorphous layer. By means of simulations performed for the high energy case, we found that the differential effect on the multiplicity is weaker as a function of ion energy loss at the entrance of the crystal than as a function of their energy loss in the crystal.