IMPROVED STOICHIOMETRY MEASUREMENTS USING 4HE ELASTIC BACKSCATTERING : EXPERIMENT AND SIMULATION

Abstract We have measured absolute spectra for MeV energy 4 He ions backscattered from amorphous silicon, SiO 2 and Si 3 N 4 targets. The simulated backscattering spectra from a-Si are only brought into acceptable agreement with experiment when we adopt 4 He stopping cross section values recently reported by Konac et al. [Nucl. Instr. and Meth. B 136–138 (1998) 159]. When these same values are used to simulate RBS spectra from SiO 2 and Si 3 N 4 targets, good agreement is found for ions incident at 2 MeV but there is ∼8% disagreement for 1 MeV ions. The implications for stoichiometry determinations based on RBS are discussed.