Simulations were made of ion-channeling spectra in a disordered Si crystal. Lattice relaxation in the neighborhood of point defects, calculated by the application of empirical potentials, was taken into account. It was shown that, in general, the back-scattering yield increased when the perfectly symmetrical configurations of point defects in the unperturbed lattice were allowed to relax. The yield enhancement depended upon the potential used, the point defect type, and the beam-lattice alignment condition. A quantitative correlation between the microscopic disorder and the macroscopic yield measured by ion channeling, was determined under the condition of a low concentration of weakly interacting point defects. An important result was that, if relaxation effects were neglected (as in previous damage models), the number of defects deduced from channeling analyses could be appreciably over-estimated. The method developed here was applied to the study of the damage distribution in the near surface of a Si sample implanted with high-energy ions. In spite of the simplified description of damage in terms of point defects, the preliminary results showed that taking account of lattice relaxation in ion-channeling simulation permitted the simultaneous fitting of back-scattering spectra collected along different axial alignment conditions. The same result could not be achieved by using the standard description, based upon unrelaxed defects.

Atomistic Modeling of Ion Channeling in Si with Point Defects - the Role of Lattice Relaxation. S.Balboni, E.Albertazzi, M.Bianconi, G.Lulli: Physical Review B, 2002, 66[4], 045202 (7pp)