A NEW MONTE-CARLO MODEL FOR THE CALCULATION OF MEIS ENERGY-SPECTRA

A Monte Carlo model for the simulation of the interaction of medium energy ions with crystalline solids is presented. In the simulations all energy loss events are taken into account to obtain simulated ion backscattering energy spectra. The inelastic energy loss in the ion-atom interactions is calculated using either one of three distinct models: (1) a continuous or impact parameter independent model; (2) the Oen and Robinson model; and (3) the dielectric response model of Lindhard. Calculated and measured spectra of medium energy He+-ions scattered from Cu(100) are compared. It is concluded that both the continuous model and the dielectric response model underestimate the impact parameter dependence of the inelastic energy loss. A good fit between simulated and experimental results is obtained for the Oen and Robinson model. The Monte Carlo simulations are used to analyze high energy resolution spectra of 100 keV H+ backscattered from NiSi2/Si(111). It is shown that the relaxation of the outermost atomic layer can be determined by comparing measured with simulated energy losses.