NON-GAUSSIAN ENERGY-LOSS DISTRIBUTION OF LIGHT-IONS IN THIN-FILMS

The energy loss distribution of 100 keV H+ and He+ transmitted through carbon thin films has been measured by high-resolution ion energy los s spectroscopy with a resolution of approximately 40 eV. The distribut ion shows an asymmetry and the asymmetry is compared with that of a ca lculation based on the Coulomb scattering with electrons. By this comp arison, the square root of the variance of the assumed Gaussian distri bution for the film thickness fluctuation was evaluated as approximate ly 10% for the film thickness of approximately 10 nm. This value is fo und to be comparable with that derived from the film thickness depende nce of the width of the energy loss distribution. The energy loss stra ggling has also been deduced and agrees reasonably with the theoretica l values. It appears that the asymmetry decreases with increasing ion beam dose, indicating beam-induced film roughening.