Crystalline effect on the lateral spread of implanted ions

We examined the lateral distribution of stopped ions in a crystalline target, considering the correlation between range straggling and the energy loss. Here we focused on the intermediate energy regime. The key quantity is the ratio of the lateral (ΔR_L) to the longitudinal (ΔR_p) range straggling in a crystalline target. Making use of a model of the impact-parameter dependent electronic stopping power, S_e, we calculated ΔR_L/ΔR_p of 10 keV-1 MeV B ions and 20 keV-10 MeV As ions implanted into Si(100) target. The value ΔR_L/ΔR_p of random ions increased with ion velocity, and this agrees with previous results given for an amorphous target. The velocity dependence of ΔR_L/ΔR_p closely correlated with that of entire electronic energy loss. On the other hand, in the case of aligned incidence, the ΔR_L/ΔR_p looked almost invariant even at a high energy when ions receive the maximum S _e. This difference was explained by means of different depth profiles of the energy transfer