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 concentration profiles in fully relaxed Si0.76Ge0.24 layers implanted with 2 MeV Si ions. The method of elaboration based on the two-beam model and linear calculation of dechanneling has been compared with the more exact trial-and-error determination of defect profiles through a Monte Carlo simulation of spectra, which describes the details of each ion path in the damaged crystal. The comparison shows that a correct description of the energy loss process of channeled He particles is very important 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 of the two-beam model: in this range accurate results can be obtained only by a detailed description of the ion paths in the damaged crystal.