RBS-CHANNELING DETERMINATION OF DAMAGE PROFILES IN FULLY RELAXED SI0.76GE0.24 IMPLANTED WITH 2 MEV SI IONS

The RBS-channeling technique has been used to measure damage concentra tion profiles in fully relaxed Si0.76Ge0.24 layers implanted with 2 Me V Si ions. The method of elaboration based on the two-beam model and l inear calculation of dechanneling has been compared with the more exac t trial-and-error determination of defect profiles through a Monte Car lo simulation of spectra, which describes the details of each ion path in the damaged crystal. The comparison shows that a correct descripti on of the energy loss process of channeled He particles is very import ant to obtain reliable results, especially in the case of deep damage profiles. When an approximate description of this effect is introduced in the two-beam model, its results show a much better agreement with those of Monte Carlo elaboration. The large discrepancies observed at low damage concentration are related to the intrinsic approximations o f the two-beam model: in this range accurate results can be obtained o nly by a detailed description of the ion paths in the damaged crystal.