On the limitations introduced by energy spread in elastic recoil detectionanalysis

Improvements in experimental techniques have led to monolayer depth resolut ion in heavy ion elastic recoil detection analysis (HI-ERDA). Evaluation of the spectra, however, is not trivial. The spectra, using even the best exp erimental set-up, are subject to finite energy resolution of both extrinsic and intrinsic origin. A proper account for energy spread is necessary to e xtract the correct depth profile from the measured spectra. With calculatio n of the correct energy (or depth) resolution of a given method. one can de cide in advance whether or not the method will resolve details of interest in the depth profile. To achieve the best depth resolution, it is also poss ible to find optimum parameters for the experiments. The limitations introd uced by the energy spread effects are discussed. An example for simulation is shown for high energy resolution HI-ERDA measurements. Satisfactory agre ement between the simulated and the measured HI-ERDA spectra taken by 60 Me V I-127(23-) ions on highly oriented pyrolythic graphite (HOPG) sample is f ound, in spite of the non-equilibrium charge state of the recoils and the d ifference in the stopping powers caused by the given charge state of the in cident ion and the recoil, which are not taken into account. To achieve mor e precise data evaluation these effects should be included in simulation co des, or all the subspectra corresponding to different recoils charge states should be measured and summed. (C) 2001 Elsevier Science B.V. All rights r eserved.