EFFECTS OF ELECTRONIC-ENERGY LOSS STRAGGLING ON RANGE DISTRIBUTIONS

The effect of electronic energy loss straggling on calculated projected range distributions has been examined using computer simulations. The distributions predicted by the transport of ion in matter (TRIM) computer simulation program (version 90) were compared to the experimental data for the B-Si (100-1000 keV), P-Si (100-1000 keV), and Ar-C (10-200 keV) systems. Although the calculated projected range values from TRIM are generally acceptable, the calculated projected range straggling values are consistently lower than the experimental data. The discrepancy is attributed to the neglect of electronic energy loss straggling in TRIM. This interpretation is supported by the fact that the addition of an impact-parameter dependent electronic stopping formula to a Monte Carlo simulation code similar to the TRIM program improves the agreement between the simulated and experimental projected range straggling data.